Chitons and Gastropods

(Haliotidae Through

Adeorbidae)

From the

Western Pacific Islands

GEOLOGICAL SURVEY PROFESSIONAL PAPER 531
Chitons and Gastropods

(Haliotidae Through

Adeorbidae)

From the

Western Pacific Islands

By HARRY S. LADD

GEOLOGICAL SURVEY PROFESSIONAL PAPER 531

Description and preliminary paleoecologic interpretations of fossil moll usks from seven island 

groups

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1966
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

Library ut' Oongivw, catalog-curd Xo. GS 66-257

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price $1.25 (paper cover)
CONTENTS

Page

Abstract ________________ __ - 1

Introduction - 1

Area and localities 1

Purpose and scope ____ .. - 1

Earlier references to fossil mollusks _______ ______ 3

Palau ____________________________- 3

Mariana Islands ___________________ 3

Marshall Islands __________ _ _ 3

Ellice Islands _____________________ 3

Funafuti ________________________. 3

New Hebrides _____________________ 3

Fiji ______________________________ 4

Tonga ____________________________ 5

Collections __________________________ 5

Acknowledgments _______-_______________ 6

Geology ________________________________ 6

Stratigraphy _________. 

Eocene ____________. 

Oligocene ____________

Miocene ___________.

Post-Miocene ________.

Pliocene ________.

Pleistocene and Recent 

Correlation ____________.

6

.___________. 9

.___________. 9

.___________. 9

Paleontology ____________________________ 9

Geographic and geologic distribution of species _____ 9

Page

Paleontology Continued

Paleoecology ____ 11

Faunal relations _ 15

Systematic paleontology . 20

Chitons ________ - 21

Schizochitonidae _ _ 21

Chitonidae _______________ ______ 23

Acanthochitonidae _ ___ 24

Gastropods ______ 25

Haliotidae _ 25

Scissurellidae .. 26

Fissurellidae ________ 27

Patellidae __________________-_ 32

Trochidae ____________-__ - 33

Stomatellidae ________ . 41

Angariidae (Delphinulidae) 42

Turbinidae _______ - 43

Phasianellidae ________ _ _ 53

Neritopsidae ______________ _ 55

Neritidae _______________________- 55

Littorinidae _ 59

Iravadiidae ________________ ___ 59

Rissoidae ______________________ 60

Assimineidae ____________________. 75

Adeorbidae (Vitrinellidae) ____________ 75

Localities __________ _______ __ ___ 81

References ______________________________ 89

Index __________________________________ 93
ILLUSTRATIONS

PLATE 1. Chitons. 

2-16. Gastropods:

2. Haliotidae, Scissurellidae, and Fissurellidae.

3. Fissurellidae, Patellidae, and Trochidae.

4. Trochidae.

5. Trochidae, Stomatellidae, and Angariidae. 

6-9. Turbinidae.

10. Phasianellidae, Neritopsidae, Neritidae, and 

Assimineidae.

11. Neritidae, Littorinidae, Iravadiidae, and Rissoidae. 

12,13. Rissoidae

14. Rissoidae and Adeorbidae. 

15, 16. Adeorbidae.

[Plates follow index")

FIGURE 3. 

4.

FIGURE 1. Index map showing location of island groups _ 

2. Sketch map showing fossil localities in the

Goikul area, Palau _______________________

Page

2

81

5-8.

9-14.

Sketch map of Guam, Mariana Islands, showing 

localities mentioned in text _______________

Sketch map showing fossil localities on

Haipan, Mariana Islands __. 

Maps showing locations of drill holes:

5. Eniwetok Atoll ______________ _ 

6. Eniwetok Atoll ___________________

7. Bikini Atoll ______ .

8. Funafuti Atoll _________ 

Maps showing fossil localities:

9. New Hebrides _____________________

10. Viti Levu, Fiji _____ .

11. Fulanga, Lau, Fiji ____ .

12. Ongea, Lau, Fiji ____ .

13. Lakemba, Lau, Fiji __ .

14. Tongatabu, Tonga ____________________

Page

82

83

84

85

86

86

87

87

89

89

TABLES

TABLE 1. Distribution of Cenozoic sediments in the island area _________________________ 

2. Major stratigraphic subdivisions recognized in holes drilled in the Marshall Islands_________

3. Correlation of Cenozoic units in the island area ______________________________

4. Geographic distribution of species _________________________________________________________

5. Geologic distribution of species _______________________________________.

6. Living Lido-Pacific mollusks that also occur in the upper Tertiary sediments of the island area

Page

7

7

10

12

16

20
CHITONS AND GASTROPODS (HALIOTIDAE THROUGH ADEORBIDAE) 

FROM THE WESTERN PACIFIC ISLANDS

By HARRY S. LADD

ABSTRACT

Cenozoic mollusks from seven island groups in the western 

Pacific are treated systematically. The islands form a broad belt 

spreading 4,000 miles across tropical latitudes from the Mariana 

Islands and Palau on the northwest through the Marshall, Ellice 

and New Hebrides groups to Fiji and Tonga on the southeast. 

Each of the island groups has a section of Quaternary limestones 

and all except the Ellice group are known to have a Tertiary 

sequence as well. The known Tertiary in all island groups, except 

that in the New Hebrides, extends back as far as the Eocene. 

No Paleocene rocks have been recognized.

Two hundred and eight species and subspecies are described. 

These include representatives of 3 families of chitons and 16 

families of gastropods (Haliotidae through Adeorbidae). Three 

new subgenera of gastropods are described: Vitiastraea (subgenus of Astraea), Subditotectarius (subgenus of Tectarius), and 

Ailinzebina (subgenus of Zebina). Sixty-seven new species and 

five new subspecies are described. The species discussed in the 

present report comprise approximately one-sixth of available 

collections.

About three-fourths of the new forms were recovered from the 

drill holes in the Marshall Islands; the remainder, from outcrop 

samples, are divided almost equally between Palau and Fiji. A 

few of the new forms from the Marshall Islands also occur in 

Palau and Fiji.

The richest and most widespread assemblages are Miocene 

(Tertiary / and g). Most of the mollusks are reef associated. 

Many, notably those of the limestones in the deep drill holes of 

the Marshall?, occur in beds that were deposited in lagoons; 

some species occur in beds that were accumulated on tidal flats; 

a few species lived in fresh or brackish waters.

The assemblages of fossil mollusks, like those living in the 

area today, are Indo-Pacific in general aspect. The strongest discernible ties are with living and fossil faunas of tropical Indonesia, rather than with faunas from more southerly areas (southern Australia and New Zealand) or more northerly areas (the 

Ryukyu Islands and Japan). Thirty-throe of the des-ribed species 

that still live in the island area have been there at least since 

late Tertiary time. Of this group, the shells of 25 were recovered 

from Marshall Island drill holes, those of 10 from outcrops in 

Fiji. A few species that lived in the island area during the 

Tertiary are now living only in other parts of the Indo-Pacific 

region.

Numerous living Indo-Pacific species had close relatives, some 

perhaps ancestral, in the island area during the upper Tertiary. 

In the Miocene of Bikini is a species of Pisulina, a genus known 

previously only from a few species living near India and Ceylon. 

The neanvt relatives of a lower Miocene CtjniNcn of Eniwetok 

live off the Capo of Ciood Hope, South Africa, tichtzachitott, the 

reef chiton that lives today in the Philippines and northern Australia, had representatives in the Marshall Islands and Palau

during the Miocene. Ties between the island area and the 

Americas are suggested, but they are less impressive than relationships with the Indo-Pacific.

INTRODUCTION

AREA AND LOCALITIES

The islands of the western Pacific considered here 

form a broad and somewhat irregular belt spreading 

4,000 miles across the tropical latitudes of the western 

Pacific, from the Mariana Islands and Palau on the 

northwest to Fiji and Tonga on the southeast (fig. 1). 

The belt measures approximately 1,000 miles in width 

and includes seven island groups Marshall,- Ellice, 

Mariana, Palau, New Hebrides, Fiji, and Tonga. Of 

these, only the Marshall and Ellice Islands lie in the 

Pacific Basin proper, within the circum-Pacific 'andesite 

line. As thus outlined, the belt includes all of Micronesia 

and eastermost Melanesia and separates Indonesia from 

most of the Pacific Basin proper.

PURPOSE AND SCOPE

This primarily paleontologic report deals mainly with 

large collections of fossil mollusks obtained by the U.S. 

Geological Survey and other governmental agencies during field investigations in Micronesia in the years immediately following World War II. These investigations 

were of two types: (1) Deep drilling at Bikini Atoll in 

connection with Operation Crossroads in 1947 and at 

Eniwetok Atoll for the Atomic Energy Commission in 

1951-52; all deep drilling was under the supervision of 

U.S. Geological Survey personnel. (2) Detailed mapping 

projects carried on by the U.S. Geological Survey under 

the sponsorship of the U.S. Army, Corps of Engineers, 

in Palau, 1947-48, Saipan, 1948-49, Tinian, 1949-51, and 

Guam, 1951-54. The Survey's collections from Guam 

supplement even larger collections made earlier by the 

Pacific Island Engineers under contract with the U.S. 

Navy.

In an attempt to make the study of island fossil mollusks as complete as possible, collections from other 

island groups Fiji, Tonga, New Hebrides, and Ellice 

Islands have been reviewed. Some material from these 

islands, already described in print, has been reexamined.
CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

FIGTRK 1. Location of island groups from which fossil mollusks have been obtained. Dashed line marks structural boundary of

Pacific Basin (andesite line).

The mollusks living in the western Pacific island area 

today are closely related to those of Indonesia, and a 

study of fossil forms should have some bearing on questions involving origin and migration. Preliminary statements of age, correlation, and paleoecologic interpretation are given in this paper, but a full discussion of these 

matters and detailed interpretations of regional relations 

of the faunas arc reserved for a later paper.
INTRODUCTION

EARLIER REFERENCES TO FOSSIL MOLLUSKS

Published papers that contain identifications or descriptions of fossil mollusks from the island under consideration are briefly annotated and arranged chronologically under island groups below.

PALAU

1951. Hatai, Kotora, Fossil Mollusca from Angaur Island: Inst. 

Geology and Paleontology, Tohoku Univ., Short paper 

3, p. 127.

Collections made by R. Tayama contain a dozen 

forms. Five are identified with Recent species, and it 

is concluded that the beds are probably post-Miocene 

in age.

MARIANA ISLANDS

1956. Gardner, Julia, in Cloud, P. E.. Jr., Schmidt, R. G., and 

Burke, H. W., Geology of Saipan, Mariana Islands: 

U.S. Geol. Survey, Prof. Paper 260-A, p. 47, 60, 66-67, 

80-81, 86-87.

Preliminary reports on collections of fossil mollusks 

from Tertiary and younger rocks of Saipan. From the 

Eocene (Hagman Formation and Matanzas Limestone) 

a few generic references; from the Miocene (Tagpochau 

Limestone) 29 mollusks named, 13 being specifically 

identified or compared with named species; from the 

Pleistocene (Mariana and Tanapag Limestones) 30 mollusks, of which 19 are identified specifically or compared 

with described species. Molluscan fauna of Mariana 

Limestone probably represents older Pleistocene.

MARSHALL ISLANDS

1954. Ladd, H. S., in Emery, K. 0., Tracey, J. I., Jr., and Ladd, 

H. S., Geology of Bikini and nearby atolls, Marshall 

Islands: U.S. Geol. Survey Prof. Paper 260-A. p. 80- 

84, 90.

Fossil mollusks from seven intervals in upper 300 

feet in deep drill holes identified with species living in 

existing lagoons of Bikini and Eniwetok. Mollusks from 

925 to 935 feet recognized as appreciably older shallowwater fauna.

1957. Ladd. H. S., and Tracey, J. I., Jr., Fossil land shells from 

deep drill holes on western Pacific atolls: Deep-Sea 

Research, v. 4, no. 3, p. 218-219.

Records occurrence of four species of minute land 

snails in Miocene and younger rocks of atolls, including 

Bikini and Eniwetok. Because the shells belong to a 

genus (Ptychodon) that normally lives on forested islands well above sea level, their occurrence suggests 

that the present-day atolls periodically stood above sea 

level, functioning as stepping stones in the distribution 

of life.

1958. Ladd, H. S., Fossil land shells from western Pacific atolls: 

Jour. Paleontology, v. 32, no. 1, p. 183-198.

Descriptions of fossil endodont land snails (Ptychodon) including three species obtained from Bikini and 

Eniwetok from lagoonal deposits now 170-1800 feet below sea level. Ages ranges from Miocene (Tertiary e) 

to Pleistocene or Recent.

1960. Ladd, H. S., Origin of the Pacific Island molluscan fauna: 

Am. Jour. Sci., Bradley volume, 258-A, p. 137-150.

Summarizes data supporting a suggestion that many 

elements of the Indo-Pacific fauna may have originated 

in the islands in Cretaceous and Tertiary times and 

later migrated with aid of prevailing winds and currents 

to west and southwest.

1960. Ladd, H. S., and Schlanger. S. 0., Drilling operations on 

Eniwetok Atoll. U.S. Geol. Survey Prof. Paper 260-Y, 

p. 863-903.

Includes generic identifications of mollusks in series 

of drill holes, deepest of which reached upper Eocene 

(Tertiary b).

1960. Ladd, H. S., Distribution of molluscan faunas in the Pacific islands during the Cenozoic: U.S. Geol. Survey 

Prof. Paper 400-B. p. B374-B375.

Brief summary of known occurrences of fossil mollusks in six island groups in the western Pacific.

ELLICE ISLANDS 

FUNAFUTI

1904. Hinde, G. J., Report on the materials from the borings 

at the Funafuti Atoll, in The Atoll of Funafuti: Royal 

Soc. London, p. 187-361.

A few of the sands obtained from the upper parts of 

the drill holes contain rare but well-preserved shells of 

micromollusks, and many of the cores from lower levels 

show molds of larger mollusks. A few generic determinations made by E. A. Smith and others are cited, but 

in most places molluscan occurrences are recorded merely 

as casts of gastropods or lamellibranchs.

1957. Ladd, H. S., and Tracey, J. I., Jr., Fossil land shells from 

deep drill holes on western Pacific atolls: Deep-Sea 

Research, v. 4, no. 3. p. 218-219.

Cites occurrence of species of Ptychodon in sample 

obtained from holes drilled in post-Miocene reefs.

1958. Ladd, H. S., Fossil land shells from western Pacific Islands: 

Jour. Paleontology, v. 32, no. 1, p. 183-198.

Ptychodon sp. A is described and figured from pardally leached coralliferous limestone from a drill hole 

at a depth of 166-170 feet. Age, Pleistocene or Recent.

NEW HEBRIDES

1905. Mawson, Douglas, The geology of the New Hebrides: 

Linnean Soc. New South Wales Proc., v. 30, p. 400-485.

Includes reference (by number) to occurrences of 

fossil mollusks identified by Charles Hedley and listed 

in appendix.

1905. Hedley. Charles. Determinations of Mollusca, in Mawson, 

Douglas, The geology of the New Hebrides: Linnean 

Soc. New South Wales Proc., v. 30, p. 477-478.

Lists 82 generic and specific determinations of mollusks believed to range in age from Pliocene to Recent. 

Several are considered to be new but are not described. 

Some forms thought to have lived beyond intertidal 

levels, perhaps as deep as 15 fathoms.
CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

1937. Abrard, Rene, and La Rile, E. A. de, Sur 1'existence du 

Neogene superieur a Cycloclypeus aux iles Epi et Malekula (Nouvelles-Hebrides): Acad. sci. [Paris] Comptes 

i-emhis, v. 204, no. 25, p. 1951-1953.

Nine fossil mollusks are identified with Recent IndoPacific species, four with fossil forms described by Ladd 

from Viti Levu, Fiji, two with Miocene species from 

Java; 17 others appear to be undescribed.

1937. Abrard, Rene, and La Rile, E. A. de, Sur la presence du 

Pliocene a Tile Malekula (Nouvelles Hebrides): Acad. 

sci. [Paris] Comptes rendus, v. 205, no. 4, p. 290-292.

A total of 31 mollusks are identified with Recent 

species or compared with such forms. Three others are 

recognized as new, and three are identified with species 

from the Pliocene of Java. The beds are assigned to 

the Pliocene.

1938. Abrard, Rene, and La Riie, E. A. de, Note sur les depots 

Quaternaires et les recif s souleves du Nouvelles-Hebrides: 

Soc. geol. France Bull., v. 8, p. 63-66.

Twenty-five generic and specific identifications of 

mollusks are reported from elevated limestone on Efate; 

age probably Quaternary but possibly Pliocene. Nineteen mollusks are listed from similar limestones on 

Eromanga.

1946. Abrard, Rene, Fossiles Neogenes et Quaternaires des Nouvelles-Hebrides: Annales de paleontologie, v. 32, 112 

p., 5 pis.

Detailed and well-illustrated report on large collections of mollusks (126 species) and other fossils made by 

E. A. de La Riie from Miocene and later rocks at 

Malekula, Epi, Efate, and Eromanga. Close ties established to Miocene of Fiji.

FIJI

1880. Woods, J. E. T., On some fossils from Levuka, Viti: 

Lmnean Soc. New South Wales Proc., v. 4, p. 358-359.

Several fossils, including mollusks, said to have been 

collected from the center of Ovalau, exact locality unknown. No specific identifications were made, but some 

of the mollusks were compared with Miocene species 

of Australasia. The fossils were imbedded in clay and 

sandy clay. [No rock of this type has been reported 

from Ovalau. and it seems probable that the material 

was collected from the marls of nearby Viti Levu. 

H.S.L.]

1898. Ball, W. H., in Agassiz, Alexander, The Tertiary elevated 

limestone reefs of Fiji: Am. Jour. Sci., 4th ser., v. 6, 

p. 165.

Contains identification of examples of 10 still-living 

genera of mollusks. Expresses the belief that the rock 

is probably younger than Eocene, possibly Miocene or 

Pliocene.

1900. David, T. W. E.. Preface to geological report by E. C. 

Andrews: Harvard Coll. Mus. Comp. Zoology Bull., v. 38, 

p. 5-10.

Mentions occurrence of large Tridacna in conglomerate 

exposed at Walu Bay on Viti Levu that suggests an 

age not older than late Tertiary.

1903. Woolnough, W. G., The continental origin of Fiji: Linnean 

Soc. New South Wales Proc., v. 28, p. 457-540.

1907. Woolnough, W. G., A contribution to the geology of Viti 

Levu, Fiji: Linnean Soc. New South Wales Proc., v. 

32, p. 433-474.

Though Woolnough collected no specifically identifiable fossil mollusks, he records the occurrence of fragmentary shells of Conus and Pecten, believed to be 

Tertiary, at localities in the then little known interior 

of Viti Levu. [These clues led later workers to wellpreserved molluscan faunas. H.S.L.]

1903. Guppy, H. B., Vanua Levu, v. 1, oj Observations of a 

naturalist in the Pacific between 1896 and 1899: Macmillan and Co., 392 p.

Generic identification given for pelecypods in shell 

bed elevated a few feet above the sea, in limestones and 

in tuffs, some of the tuffs now lying more than 2.000 

feet above sea level.

1918. Foye, W. G., Geological observations in Fiji: Am. Acad. 

Arts and Sci. Proc, v. 54, no. 1, p. 1-142.

On page 86 there is a list of 15 generic identifications 

of mollusks as made by Paul Bartsch; the genera are 

common tropical forms, each being followed by a query; 

Foye collected the material from three localities on 

Viti Levu.

1926. Mansfield, WT . C., Fossils from quarries near Suva, Viti 

Levu, Fiji Islands * * * with annotated bibliography of 

the geology of the Fiji Islands: Carnegie Inst. Washington Pub. 344, p. 85-104.

Description of 4 gastropods and 14 pelecypods (including 3 new species). Tertiary age suggested, probably late Miocene or early Pliocene.

1927. Matley, C. A., and Davies, A. M., Some observations on 

the geology of Viti Levu: Geol. Mag. [Great Britain], 

v. 64, no. 752, p. 65-75.

Includes description of supposed fresh-water clam,

Nodularia vitiensis Davies, from the marls above

Nasongo; beds probably Tertiary, possibly Miocene.

1930. Davies, A. M., Fossils from Viti Levu: Geol. Mag. [Great 

Britain], v. 67, no. 787, p. 48.

Molds of bivalves from near Nasongo, referred in 

1927 (Matley and Davies) to the fresh water clam 

Nodularia, are reassigned to marine Mactracea.

1934. Ladd, H. S., in Ladd and others, Geology of Vitilevu, 

Fiji: B. P. Bishop Mus. Bull. 119, 263 p.

One hundred and twenty-two mollusks (53 pelecypods, 

3 scaphopods, 1 chiton, and 65 gastropods), most of which 

were collected during reconnaissance surveys in 1926 

and 1928. are described and most of them figured; they 

are from beds ranging in age from Miocene to Recent. 

Brief discussion of paleoecological conditions.

1945. Ladd. H. S., in Ladd and Hoffmeister, J. E., Geology of 

Lau, Fiji: B. P. Bishop Mus. Bull. 181, 399 p.

Seventy-six mollusks, half pelecypods and half gastropods, most of them collected during a reconnaissance
INTRODUCTION

survey in 1934, are described and many figured; they 

are from beds ranging in age from Miocene to Pleistocene. Brief discussion of paleoecological conditions (by 

Ladd and Hoffmeister).

1959. Charig, A. J., in Bartholomew, R. W., Geology of the Lautoka area north-west Viti Levu: Suva, Fiji, Geol. Survey 

Dept. Bull. 2, 25 p., geol. map.

Sixteen mollusks, 3 pelecypods and 13 gastropods, are 

identified by A. J. Charig and C. P. Nuttall (p. 18-19) 

from two localities in bedded tuffaceous sediments 

mapped as part of the Sambeto series. Twelve fossils are 

identified with still-living species, three others are compared with such forms. Only one species appears to 

represent an extinct species though several are known 

to occur as fossils in the Pliocene or later. A Pliocene 

age is thought probable, a late Miocene age possible.

1960. Ibbotson, Peter, Geology of the Suva area, Viti Levu: 

Suva, Fiji Geol. Survey Dept. Bull. 4, 47 p., geol. map.

Detailed report on quarter-degree sheet in southeastern Viti Levu that includes many of the late Tertiary localities in the Suva Formation that have yielded 

fossil mollusks. Identifications of Mansfield (1926), 

Davies (1927, 1930), and Ladd (1934) are listed.

1960. Bartholomew, R. W.. Geology of the Nandi area, western 

Viti Levu: Suva, Fiji Geol. Survey Dept. Bull. 7, 27 p., 

geol. map.

A list of fossils identified by L. R. Cox in 1954 (p. 11) 

includes six molluscan generic determinations.

1961. Ibbotson, Peter, Geology of Ovalau, Moturiki and Naingani: Suva, Fiji Geol. Survey Dept. Bull. 9, p. 1-7, 

geol. map.

Quotes in full, Tenison-Woods' brief report of 1897, 

pointing out that it is the only report on fossiliferous 

material from Ovalau.

1963. Charig, A. J., The gastropod genus Thatcheria and its relationships: British Mus. (Nat. History) Bull., Geol. 

v. 7, no. 9, p. 257-297.

Includes description of Thatcheria vitiensis from 

luffaceous marl of Vanua Levu Formation on Vanua 

Levu; age probably early Pliocene.

1963. Rickard, M. J., The geology of the Mbalevuto area: Suva, 

Fiji Geol. Survey Dept. Bull. 11, 36 p., geol. map.

Includes references (p. 30-33) to mollusks, identified 

by H. S. Ladd, from the Singatoka, Suva, and Mba 

series of upper Tertiary area.

1965. Ladd, H. S., Tertiary fresh-water fossils from Pacific 

islands: Malacologia v. 2, no. 2, p. 189-198.

Includes description of a species of Melanoides from 

beds formed in mangrove swamp on Viti Levu in late 

Tertiary time.

TONGA

1926. Mansfield. W. C., Fossils from * * * Vavao, Tonga Islands 

* * *: Carnegie Inst. Washington Pub. 344, p. 85-104.

Three mollusks, one identified with a living species 

and one related to a living form, are listed, and a postTertiary age is suggested.

1932. Hoffmeister, J. E., Geology of Eua, Tonga: B. P. Bishop 

Mus. Bull. 96, 93 p.

Records the occurrence of the nautiloid Aturia (p. 

33) in bedded volcanic tuffs believed to be Miocene in 

age.

1935. Ostergaard, J. M., Recent and fossil marine Mollusca of 

Tongatabu: B. P. Bishop Mus. Bull. 131, 59 p.

A total of 39 fossil mollusks (26 gastropods and 13 

pelecypods) from Tongatabu and Vavau are identified 

with Recent species. Limestones containing fossils believed to be late Pleistocene in age.

1941. Miller, A. K., An Aturia from the Tonga Islands of the 

central Pacific: Jour. Paleontology, v. 15, no. 4, p. 

429-431.

Specimen collected by J. E. Hoffmeister from tuffs, 

believed to be Miocene, is described and figured as 

Aturia cf. A. aturi (Basterot).

COLLECTIONS

Most of the collections on which the present study is 

based were made by U.S. Geological Survey personnel; 

others were loaned for study by museums and other institutions. All important sources are given below:

Palau. Most of the Palau material was collected by 

H. S. Ladd in 1958; other collections had been made 

earlier by several Geological Survey geologists, particularly in 1948 by a party headed by the late Arnold 

Mason.

Mariana Islands. The largest collections of megafossils from any of the islands under consideration were 

made from Guam by the Pacific Islands Engineers under 

contract with the U.S. Navy in 1946-50; supplementary 

collections from Guam were made by a Geological Survey 

field party under the leadership of J. I. Tracey, Jr., in 

1951-54 and by H. S. Ladd in 1958. Most of the Saipan 

material was collected by a Geological Survey field party 

headed by P. E. Cloud, Jr., in 1948-49, and minor additions were made by H. S. Ladd in 1958. The few fossil 

mollusks that have been obtained from Tinian were collected by the late Josiah Bridge in 1946 and by Cloud in 

1949, both of the Geological Survey.

Marshall Islands. Cores and cuttings were obtained 

from drill holes on Eniwetok and Bikini Atolls between 

1947 and 1952.

Ellice Islands. Cores and cuttings from drill holes 

obtained by the British on Funafuti Atoll between 1896 

and 1898 (David and others, 1904). Material was borrowed from the British Museum (Natural History), the 

Australian Museum in Sydney, and the Museum of Comparative Zoology at Harvard.

New Hebrides. Small collections were made by H. T. 

Stearns of the Geological Survey in 1943; some material
CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

was borrowed from M. R. Abrard of the Museum National d'Histoire Naturelle in Paris.

Fiji. The collections of larger mollusks described by 

Ladd in 1934 and 1945 have been supplemented by undescribed larger mollusks from Viti Levu collected by 

Ladd in 1934 and by micromolluscan material not previously described. Additional material collected in recent 

years has been furnished by the Geological Survey Department in Fiji and by William Briggs of the U.S. 

Geological Survey who visited Viti Levu in 1962.

Tonga. A few Tertiary mollusks were collected by 

J. E. Hoffmeister in 1926 and 1928; post-Tertiary material was collected by J. Ostergaarcl in 1926 and was 

loaned by the Bernice P. Bishop Museum in Honolulu.

The largest molluscan collections are those from Eniwetok, Guam, and Fiji, in that order. The Eniwetok 

collections from drill holes are rich in well-preserved 

micromollusks. Those from Guam and Fiji are outcrop 

samples, and many of them are molds or calcite casts; 

they are comparatively poor in micromollusks.

ACKNOWLEDGMENTS

Prior to her retirement in 1952, the late Dr. Julia 

Gardner made preliminary determinations of many of 

the fossil mollusks collected by Geological Survey personnel in the Mariana Islands and Palau. Her identifications of Saipan mollusks were published in Professional 

Paper 280-A (Cloud and others, 1956). In connection 

with her studies, she assembled a useful index of references on island fossil mollusks. In 1947 she visited Palau 

where she collected from the Palau Limestone in the 

Koror area.

In 1945, I discussed Palauan geology with the late 

Prof. Risaburo Tayama in Sendai, Japan, and was given 

suggestions as to promising places in which to collect 

fossil mollusks. These suggestions proved invaluable 

during fieldwork in Palau in 1958. At that time I was 

cordially received and was given much assistance by Mr. 

R. P. Owen, staff entomologist with the Trust Territories 

in Koror.

The extensive collections of Recent mollusks at the 

U.S. National Museum contain many shells collected by 

Dr. J. P. E. Morrison and others in the Marshall Islands 

during Operation Crossroads in 1946-47 and later. These 

shells were particularly useful in studying fossils obtained from drill holes. The Academy of Natural Sciences in Philadelphia, through Dr. R. T. Abbott, curator, 

loaned Recent chitons for comparative studies and gave 

full access to the collections when I visited Philadelphia 

in 1964; the Bishop Museum, through Mr. E. H. Bryan, 

Jr., curator, loaned the fossil material from Tonga collected by Jens Ostergaarcl; the British Museum (Natural

History), the Australian Museum, and the Museum of 

Comparative Zoology at Harvard loaned samples from 

the drill holes on Funafuti. Professor Rene Abrard of the 

Museum National d'Histoire Naturelle loaned fossil 

material described by him from the New Hebrides. Dr. 

C. Beets of Leiden, Netherlands, kindly checked identification of a species that appeared to be closely related 

to a form described by him from the Miocene of Borneo. 

Mr. W. M. Briggs, Jr., and Mrs. Evelyn Bourne, both 

of the U.S. Geological Survey, aided in the preparation 

of much of the material, and Mr. Briggs made almost all 

the photographs of fossils. I am indebted to Drs. H. A. 

Rehder and J. P. E. Morrison, of the U.S. National 

Museum, and Dr. Robert Robertson, of the Academy of 

Natural Sciences, for assistance in the identification of 

certain mollusks. The manuscript has benefited from 

critical reviews by W. P. Woodring of the U.S. National 

Museum and by Dr. R. T. Abbott of the Academy of 

Natural Sciences.

GEOLOGY 

STRATIGRAPHY

Detailed studies in recent years have greatly increased 

our knowledge of the Cenozoic sections in several of the 

island groups under consideration. In the Pacific Basin 

proper, a standard section has been established from 

results of deep drilling in the Marshall Islands (described 

in the numerous chapters of U.S. Geol. Survey Prof. 

Paper 260, especially Emery and others, 1954; Cole, 

1958; Todd and Low, 1960; Ladd and Schlanger, 1960; 

Schlanger, 1963). Outside the basin, in the Mariana 

Islands (Cloud and others, 1956; Doan and others, 1960; 

Tracey and others, 1964) ; in Palau, (Mason and others, 

1956) ; and in Fiji, (bulletins published by Geol. Survey 

Dept. of Fiji, including: Bartholomew, 1959, 1960; 

Houtz, 1959, 1960, 1963; Ibbotson, 1960, 1962; Rickard, 

1963; Houtz and Phillips 1963; also Cole, 1960); detailed 

mapping and paleontological studies have established 

similar sections. In the Ellice Islands, in the New 

Hebrides, and in Tonga, available information is much 

less complete.

Each of the seven island groups has a section of 

Quaternary limestones and all except Funafuti in the 

Ellice group are known to have a Tertiary sequence as 

well. The known Tertiary in all groups, except that in 

the New Hebrides, extends downward into the Eocene. 

No Paleocene has been reported from any of the island 

groups.

The subdivisions of the Tertiary are based on the system developed for the East Indies by van der Vlerk and 

Umbgrove (1927). By using larger Foraminifera, the
GEOLOGY 

TABLE 1. Distribution of Cenozoic sediments in the island area

[ X, present; question mark indicates uncertain identification]

Quaternary

Upper 

Tertiary

Lower 

Tertiary

Indonesia1

h

g

f

e

d

c

b

a2

Recent

Pleistocene

Pliocene

Upper 

Miocene

Lower 

Miocene

Oligocene

Eocene

Marshall Islands

Eniwetok

X

X

X

X

X

X

X?

X

Bikini

X

X 

X

X

X

X

X?

X

Ellice

X

X

Mariana Islands

Guam

X

X

X

X

X

X

X

X

Saipan

X

X

?

X

X

Tinian

X

X

X

?

?

X

X

Palau

X

X

X

X

X

X

New 

Hebrides

X

X

X

X

X

Fiji

Viti 

Levu

X

X

X

X

X

X

X

X

Lau

X

X

X

X

X

X

Tonga

X

X

X

X

1 Some workers (Bemmelen, 1949, p. 88) place part of Tertiary g into the Pliocene with Tertiary h.

2 Occurrence of Tertiary a ba^ed on smaller Foraminifera on Sylvania Guyot adjoining Bikini (Hamilton and Rex, 1959).

Tertiary sequence was subdivided into six units, designated by the letters a-/. Later, two younger stages g 

and h were added (Leopold and van der Vlerk, 1931; 

table 1, this paper). This classification has proved to be 

exceedingly useful in the western Pacific island groups.

In the atoll groups (Marshall and Ellice Islands), the 

sedimentary rocks consist of reef limestone and dolomitized limestone. Similar limestones occur in the high 

island groups along with a variety of terrestrial and 

marine tuffs and coarser volcanic sediments. The 

Cenozoic sedimentary rocks are known to rest on volcanic 

rocks in most areas. In the Ellice Islands, no volcanic 

rocks are exposed nor have they been reached by the 

drill, but seismic evidence suggests such a foundation at 

a depth of about 1,800 feet (Gaskell and Swallow, 1953, 

p. 3). In Fiji (McDougall, 1963) and Tonga (Guest, 

1959, p. 3), plutonic rocks are known; their presence 

records more complex histories than in other island 

groups. The Tongan plutonic rocks are thought to be of 

pre-Tertiary age.

Fossils from the section established by deep drilling 

in the Marshall Islands have been studied by several 

workers; their findings have been published as chapters 

of U.S. Geological Survey Professional Paper 260. The 

major divisions recognized are shown in table 2. With 

slight modification, this is the arrangement given by Cole 

(1958, p. 745).

EOCENE

The only known occurrence of lower Eocene (Tertiary 

a) sediments in the island area is the phosphatized

Globigerina ooze described by Hamilton and Rex (1959) 

from the top of Sylvania Guyot adjacent to Bikini. The 

ooze contained no mollusks.

Limestones of late Eocene age (Tertiary b] are widely 

known in Eniwetok, the Marianas, Palau, Fiji, and 

Tonga. Mollusks occur in some of these limestones, but 

they are rare, and in many places they are poorly preserved; none from the families here treated has been 

specifically identified. In Fiji and Tonga the limestones 

have yielded diagnostic larger Foraminifera, but no other 

identifiable fossils. In Palau, numerous fragments of an 

upper Eocene limestone containing larger Foraminifera, 

algae, and unidentifiable mollusks occur in a volcanic 

breccia. In the Mariana Islands, upper Eocene rocks have 

yielded a considerable variety of fossils, including 

Foraminifera, radiolarians, discoasters, algae and in

TABLE 2. Major stratigraphic subdivisions recognized in

holex drilled in the Marshall Islands

Stratigraphic divisions

Post- Miocene

Upper Miocene

Lower Miocene

Upper Eocene

Tertiary g

Tertiary /

Tertiary e

Tertiary b

Eniwetok

Depth 

(feet)

0-615

615-860

860-1,080

1,080-2,780

2,780-4,610

Bikini

Depth 

(feet)

0-700

700-980

980-1,166

1,166-2,556 +
8 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

some places fragmentary and poorly preserved mollusks 

have been found. In the Marshall Islands, some Eocene 

mollusks have been recovered from deep holes on Eniwetok. These include poorly preserved bivalves {Area 

and Pecten), but most are the molds of minute gastropods, including turbinids and eyclostrematids, that are 

not identifiable.

OLIGOCENE

Limestones containing larger Foraminifera diagnostic 

of the lower Oligocene of the Indonesian section (Tertiary 

c) have been found in Fiji and in Guam (Cole 1960, 

1963). The beds containing these fossils are restricted in 

their distribution and to date (1965) have yielded no 

identifiable mollusks. Some of the limestones on Guam 

that contained Oligocene larger Foraminifera also yielded 

an assemblage of smaller Foraminifera that is definitely 

early Oligocene (Tertiary c) in age (Ruth Todd, oral 

commun., 1963).

The section drilled in the Marshall Islands includes 

beds containing smaller Foraminifera that may represent the lower Oligocene (Tertiary c) but the correlation is questionable (Todd and Low, 1960). In drill 

holes F-l and E-l on Eniwetok, there is an interval of 

about 100 feet (2,687-2,780 ft) that Cole (1958, p. 745, 

748) labeled "unknown" because it yielded no diagnostic 

larger Foraminifera. Above this interval the beds contain lower Miocene Foraminifera (Tertiary e ) and below 

they contain upper Eocene species (Tertiary 6). Along 

with the smaller Foraminifera that are suggestive of the 

lower Oligocene, the questionable beds yielded three 

specimens of Rissoina ailinana Ladd, n. sp., a species 

that occurs in some Tertiary e samples in both Eniwetok 

and Bikini. Also recovered were nine specimens (from 

four samples) of a well-preserved Miocene Ampullina, 

described from East Borneo by Beets (1941) as Globularia berauensis.^ Because of the occurrence of these 

mollusks, I have tentatively assigned the unknown interval to the Miocene.

No beds that would represent the upper Oligocene 

(Tertiary d) have been found in any of the island groups 

here considered. The Fina-sisu Formation of Saipan, 

previously assigned to the late Oligocene (Todd and 

others, 1954) on the basis of smaller Foraminifera, is now 

regarded as early Miocene in age (Ruth Todd, oral 

commun., 1963).

MIOCENE

Miocene sedimentary rocks have been recognized in all 

the island groups except in the Ellice Islands. In the 

Eniwetok drill holes, shallow-water lagoonal limestones

1 Mr. Beets kindly checked the identification of this species by comparing 

an Eniwetok shell with his type in the museum in Leiden.

exceed 2,000 feet (table 2). All three major subdivisions 

of the Miocene (Tertiary e, /, and g ) are represented, but 

the section is not complete, inasmuch as a solution unconformity appears at the top of Tertiary e (Schlanger, 1963, 

p. 995). Miocene reef limestones are also found in Palau. 

The total section exceeds 750 feet, but some parts may 

be younger than Miocene (Cole, 1950; Mason and others, 

1956, p. 55-59). In at least two areas in Palau the 

Miocene includes thin tuffaceous limestone and marl 

that are here assigned to the upper Miocene (Tertiary g). 

On Saipan and Tinian in the Mariana Islands, the lower 

Miocene (Tertiary e) limestones are 750 to nearly 1,000 

feet in maximum thickness and include some tuffaceous 

facies (Cloud and others, 1956, p. 62-77; Doan and 

others, 1960, p. 60-62). Tertiary e rocks on Guam exceed 

2,000 feet, but most of the sequence consists of volcanic 

flows and breccias. Although some of the included limestones are of shallow-water origin, Globigerina-rich sediments, of deeper water origin, are present. On Guam the 

Tertiary e rocks are overlain by several hundred feet of 

younger limestones; some of these are definitely of Tertiary / age, others may be Tertiary g. (Tracey and others, 

1964). In Fiji the Miocene sequence is dominantly volcanic. It consists of many thousands of feet of agglomerates, tuffs, and marls, some water laid, together with a 

variety of igneous rocks. Limestones of shallow-water 

origin are at least 200 feet thick in some areas. Miocene 

rocks of comparable types have been reported from the 

less well known New Hebrides (Mawson, 1905; Abrard, 

1946). In Tonga the known Miocene is thin; it consists 

of a series of volcanic tuffs totaling 200-300 feet in thickness (Hoffmeister, 1932, p. 30, 33).

POST-MIOCENE

In the island area it is difficult, if not impossible, to 

recognize age boundaries in the post-Miocene sediments. 

Diagnostic larger Foraminifera which are so useful in 

subdividing the Miocene and older Tertiary beds have 

not been found. Other organisms, especially planktonic 

smaller Foraminifera, discoasters, and radiolarians, offer 

great promise, but these organisms are not everywhere 

present, and their geologic distribution in the islands has 

not yet been adequately determined. Mollusks, even 

where well preserved and abundant, are of limited usefulness in determining exact post-Miocene ages.

In the Marshall Island drill holes, the top of the 

Miocene has been agreed upon by those who have studied 

the Foraminifera from cores and cuttings. The postMiocene section ranges from 510 to 700 feet in thickness, 

but it has not been subdivided accurately (Cole 1958, p. 

745; Todd and Low, 1960, p. 802, 807). These limestone 

beds thought to be mostly lagoonal, have not yielded
PALEONTOLOGY 9

assemblages of diseoasters or radiolarians. The smaller 

Foraminifera in the elevated post-Miocene reef limestones of Fiji, Tonga, and Palau, are preserved mostly as 

unidentifiable molds, as are those in most of the Quaternary sediments drilled on Funafuti. The post-Tertiary 

limestone of the Mariana Islands contains both larger 

and smaller Foraminifera, but no extinct species are included and hence no exact stratigraphic boundaries are 

indicated. Some of the elevated limestones of the New 

Hebrides contain molluscan species previously reported 

from the Pliocene of Java (Abrard and La Rile, 1937).

PLIOCENE

The Pliocene-Pleistocene boundary is perhaps the most 

difficult Cenozoic boundary to recognize in the island 

area. Environmental conditions in the tropical islands 

seem to have been little affected by the onset of glaciation 

in other parts of the world, and no clear stratigraphic 

break appears.

In cores of deep-sea sediments containing layers of icerafted materials, the earliest of these can be taken as the 

base of the Pleistocene, and correlations with other deepsea sections can be made on the basis of wide-ranging 

Foraminifera or other planktonic organisms. Eventually 

a system of this sort may be successfully applied to some 

of the sediments of the island area.

PLEISTOCENE AND RECENT

In the absence of definitive paleontologic evidence, it 

is not possible to recognize Pleistocene beds with certainty, though suggestive physiographic evidence has 

been called upon in several areas. In the Bikini drill 

holes, three rock units above 294 feet, characterized by 

distinctive species of still-living smaller Foraminifera, 

seem to be related to present physiographic features. 

These rock units are thought to represent three late 

stages of reef growth, probably separated by two periods 

of emergence representing Pleistocene shifts in sea level 

(Emery and others, 1954, p. 2, 75, 132-133).

On Saipan, the name Mariana was applied to limestones now as much as 500 feet above existing sea level 

and the name Tanapag to limestones below 100 feet. The 

Mariana includes reef and lagoonal deposits, whereas the 

Tanapag represents rock of an elevated fringing reef. 

The Mariana was assigned an early, and the Tanapag a 

younger, Pleistocene age. These interpretations are supported by a period of faulting that intervened between 

the benching of the Mariana and the deposition of the 

Tanapag. Carbon-14 analyses of the Tanapag seem to 

support the postulated younger Pleistocene age (Cloud 

and others, 1956, p. 2, 79-80, 87). On Guam, the Mariana 

Limestone yielded no diagnostic larger Foraminifera but 

was assigned a Pleistocene, or possibly Recent, age (Cole, 

1963, p. El, E10).

In eastern Fiji (Lau), the Fulanga Limestone is composed of elevated veneers of reef limestone, occurs on 

two or three islands, and has been referred tentatively 

to the Pleistocene. Paleontologically it yielded two previously undescribed echinoids, a new decapod crustacean, 

and a few species of still-living mollusks. Among the 

mollusks are species that no longer live in Fiji. The preceding data suggest an appreciable age for the Fulanga, 

but they do not clearly indicate Pleistocene. That interpretation was based almost entirely on field evidence 

(Ladd and others, 1945, p. 267, 313, 322, 380).

CORRELATION

Age determinations and correlations involving major 

stratigraphic units in the several island groups are based 

on the letter classification established for Indonesia (van 

tier Vlerk and Umbgrove, 1927; Leopold and van der 

Vlerk, 1931 L No attempt is made to tie these Indonesian 

units to the stages of the standard European sequences. 

Efforts of this sort have been made, but most such efforts 

have been regarded as tentative, even by their proposers 

(Glaessner, 1943, 1959; Todd and others, 1954; Cloud, 

1956; Eames and others, 1962). The exact ages (by the 

Indonesian letter system) of some of the Tertiary units 

in the islands are in question because of conflicting interpretations of faunal evidence, notably that of the larger 

versus the smaller Foraminifera. These differences are 

still being discussed vigorously. (Cole and others, 1960; 

Glaessner, 1960; Eames and others, 1962). The mollusks, 

which rarely occur in beds with diagnostic Foraminifera, 

are not deeply involved with questions of exact correlation. The correlations shown in table 3 are based more 

heavily on evidence from the larger Foraminifera than 

on that of other groups of fossils. It is recognized, however, that eventually the evidence of such mobile planktonic groups as some of the smaller Foraminifera, the 

Radiolaria (Riedel, 19591, and especially the diseoasters 

(Bramlettc and Riedel, 19541 may offer modified, and 

perhaps sounder, correlations. Boundaries and units that 

are questionable are so marked in table 3, and it should, 

perhaps, be repeated that the exact ages of all postMiocene units in the island area are debatable.

PALEONTOLOGY

GEOGRAPHIC AND GEOLOGIC DISTRIBUTION 

OF SPECIES

The geographic distribution of all the species treated 

is shown in table 4. The Marshall Island faunas are the 

richest, and more than half of the total number of named 

forms are recorded from Eniwetok alone. Fiji ranks 

second in number, Palau a poor third. Faunas from the 

other island groups are smaller but none of these areas, 

except the Mariana Islands, has been adequately collected.
^ 2-S 

S H^ 

O

f. ^- 

* K 

". W2, 

" .^1 

I asto' O 

* ^ 

rHm 

m > 

m

8(0

3

Lower

«

Globigenna 1ooze

Upper

o33

O

3

-

O 

f

3 

(C

Lower

-

 __. 

. 

Upper

a.

"O

Babelthuap ? 

' Formation 

 o

"O

-r 

= 

6

3

01

3

-n

1

0 

<c

3

Fm. 1inyama 

"

Fm. tansa 

Pyroclastic 

rocks

Ngeremlengui Formation

s^

T3 d 

m > 

33 33 

8

D

Upper Lower 

«S *-*, 

O 

3

=» 

QUATERNARY

o

3

33

3

chiefly complex, Reef 

forereef and lagoonal 

limestone, Reef 

bed lagoon chiefly 

 o

m

S o 

5-3

3

limesto

aSeries 

o_

3

Wainima Tholo 

Plutoni and limes

u> o 

3

n § 3 

ft8 00 

§LT 2 

Tagpochan Limestone

if

0 O 

3

r3

> 3 

^ W CD "~ 

" i 5^ 0 1 

| c 3 

¥ oo 

m

o 

If Ul 

013

H 

<- 

Reef 

limestone

1 I 

8 c 

3 

(0

3[?3^ 1 &5

S S 3 0 8 SK 3 0) 3 » (n 

u" <t> <t> 

r-

-< (D 

3 O 

U 3 

to

|f 

O)' ft 

3 O 

01 3 

Reef 

limestone

H s 

c cr 

= 00 

g (0 

2 r 

a 3 

0 ° 

"°

1 limestone

Vatia Ser

Tavua Se

(n *' 

3? 

1%

013 O 

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(D (n 

Z, o 

3 

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Beach deposits 

Rai 

Peleliu ___

sedands

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Raised beach and gravel

CD

CL 

(0

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Alluvium 

lateritt

3 

Q.

of °- 

3 3 

Reef 

nestone

SYSTEM

m

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LETTER 

CLASSIFICATION

ENIWETO

CD 

2

FUNAFUTI

MARSHALL

m 

rO 

m

 PALAU 

5AIPAN

TINIAN

GUAM

MARIANA

NEW 

HEBRIDES

H 

m

c 

c

-n

3

OT

SKOXIHO QKV saodOHiSvo WOUA omovd
PALEONTOLOGY 11

The geologic distribution of species is shown in table 

5. The numbers of named species from each of two stages 

of the Miocene (Tertiary / and g I exceed those recorded 

from all other divisions of the Cenozoic.

PALEOECOLOGY

Many of the Cenozoic sediments that crop out on the 

islands, or have been reached by the drill below sea level, 

are limestones that were formed in shallow7 water on 

reefs or in adjacent lagoons. Such sediments dominate 

in the sections drilled below the three atolls Eniwetok, 

Bikini, and Funafuti. Similar reef limestones crop out 

extensively in the Mariana Islands, in Palau, and in 

eastern Fiji. At Eniwetok and in the Mariana Islands, 

the shallow-water limestones occur with off-reef limestones that appear to have been accumulated in somewhat 

deeper water, the indicated depths being not less than 

100 fathoms (Todd, 1957, p. 271; Todd and Low 1960, 

p. 812-815; Schlanger 1963, p. 999-1002). Among the 

high islands, particularly in Fiji and the New Hebrides, 

are thick sequences of tuffs and marls, many of which 

were deposited in marine water. Globigerina-rich beds in 

these sections point to water of at least moderate depths, 

but lenticular masses of shallow-water limestones are 

included between them. Such associations raise many 

problems that have not, as yet, been satisfactorily solved. 

On most islands, both lateral and vertical changes in 

facies are abrupt and even repetitious. Paleoecological 

interpretations of a given fossiliferous bed can be made 

without great difficulty but the environmental history 

recorded by sequence of appreciable thickness is much 

more complicated.

Mollusks occur in most of the kinds of rocks mentioned 

above but the species described in the present report were 

all derived from shallow-water deposits that formed on 

reefs, reef flats, shore platforms, and in lagoons adjacent 

to reefs. This report deals with the scanty record left 

by the chitons,- and the fuller records of 15 families of 

gastropods. Taken together, the fossils represent only 

about one-sixth of the collections available, and hence 

full paleoecological interpretations are not attempted at 

this time.

In Palau, the thick sections of cavernous rock that 

form the Palau Limestone of southern Babelthuap and 

the numerous islands that lie to the south are of reef 

origin. Mollusks are abundant in the Palau, but most of 

them are unidentifiable molds of common reef types, 

including trochids and turbinids. Locally, however, at 

the base of the Palau, tuffaceous and marly beds carry 

a rich molluscan fauna of late Miocene (Tertiary g) age. 

On the Goikul Peninsula of southeast Babelthuap, a thin 

wedge of marl lies between the Airai Lignite and a thick

section of cavernous Palau Limestone. Around the peninsula today there is a broad shore platform bordered by 

mangrove swamps. This flat is nearly awash at low tide 

and is partly covered by waving eel grass. Shore-flat 

mollusks are abundant. Apparently, conditions were 

similar during the late Miocene. Many bedding planes 

in the marls are crossed by carbonaceous stripes, thought 

to represent eel grass, and the same genera of shallowwater mollusks are common, though the species are different. All but 2 of the 18 Palauan mollusks described 

in the present report were obtained from the marl on the 

Goikul Peninsula.

In the Mariana Islands, particularly on Saipan and 

Guam, Cenozoic reef-associated limestones and certain 

Globigerina-Y\ch sediments that suggest deeper waters 

have been mapped and studied in detail. Paleoecological 

interpretations, based in large part on the distribution 

of Foraminifera, have been offered (Todd and others, 

1954, p. 677; Cloud and others, 1956, p. 68, 80-81, 86-88; 

Hanzawa, 1957, p. 33-34; Todd, 1957, p. 265, 273-283; 

Cole, 1963, p. E11-E12).

Mollusks left a meager fossil record on Saipan, particularly as to the kinds considered in the present report. 

Mollusk collections from Guam are larger and more 

varied, but most of those here described are types commonly found near the reef edge or on the reef flat. Collecting localities on Guam are concentrated in the waist 

of the island where the several facies of the Mariana 

Limestone are widely exposed. This same area is notably 

poor in Foraminifera, because many of these organisms 

lived in moderate to fairly deep water.

The limestone sections drilled beneath Eniwetok and 

Bikini in the Marshall Islands are all reef associated. 

Many of the highly fossiliferous beds, especially those 

rich in mollusks, appear to have been deposited in 

lagoons, but other environments reef wall, open shoal, 

and off-reef deposits are also found. Paleoecological 

interpretations have been summarized and graphically 

portrayed by Scblanger (1963, p. 998-1001).

Of particular interest is a thick zone that roughly encompasses the beds assigned to Tertiary g and /. This 

zone was found in all the deep holes drilled on Eniwetok 

and Bikini. The section, referred to by Schlanger (1963, 

1). 10001 as the "Coral-mollusk-rich zone," apparently 

never was raised above the sea to be leached and recrystallized. Its fossils are almost perfectly preserved, 

many mollusk shells even retaining traces o,f their original 

color patterns. The beds are unconsolidated and core 

recovery was difficult, but rich concentrations of mollusks 

were obtained in some core runs. The cored material 

appeared to be far richer in mollusk shells than any sediments dredged from the floors of the existing lagoons.
12 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

TABLE 4. Geographic distribution of species

Species

Sohizochitonidae : 

Schizochiton incistts yoikulensis Ladd. n. subsp

marshallensis Ladd, n. sp

Lor ic ell a sp. A

Chitonidae : 

Lucilina russelli Ladd, n. sp

sp. A_ ____ _

sp. B.

sp - - _- _________ __ _______

Acanthochitonidae : 

Acanthochitona sp_

Cryptopla* cf. C. ntenkrawitensis Beets

sp. A.

sp. B__

sp.

Haliotidae: 

Haliotis (Padollus) or/na Gmeliii

cf. //. clathrala Reeve

turuthaensis Laddsp _ _ _____ _

Scissurellidae: 

Srissurella (Scissurdla) declfnans Watson

(Scissitrella) coronata Watson

(Atiatoma) equatoria Hedley

Fissurellidae : 

Emarginula (Emarginula) bicancellata Montrouzier

(Emarginula) cf. E. peasei (Thiele)

aff. E. clypeus A. Adams

(tiubztidora) souperbiana Pilsbry

(Xubzeidora) sp. A___

sp. B.__________ _

llcmitoma (Hemitoma) sp

(Montfortia) bikiniensis Ijadd, n. sp

(Montfortia) sp. A_ _

(Montforttsta) e.rcentrica (Iredale)

K tin ula e.rquisita A. Adams

sp

.SVittug (Nannoscutum) sp. A

(Nannoscutum) sp. B

Diodora (Elegidion) marshallensis Ladd, n. sp

(Elegtdion) aff. D. granifera (Pease)

sp. A__ _

Patellidae: 

Patella (Scutellastra) stellaeformis Reeve

Cellana aff. C. sagittata (Goulcl)

sp. A_

? sp_.

Trochidae: 

Euchelus (Euchelus) cf. E. quadricarinatus (Dillwyn)

(Herpetopoma) instrictus (Gould)

(Herpetopoma) instrictus suvaensis Ladd, n. subsp

(Vaceuchelus) angulatus Pease

( I aceuchelus) sp. A .

Hybochelus cancellatus orientalis Pilsbry

karoricus Ladd _

Thalotia (Thalotia) berauensis (Beets)

(Thalotia) aff. T. elongatus (Wood)

(Beraua) sp .

Turd ca (Perrinia) morrisoni Ladd, n. sp

Gibbula (Gibbula) engebiensis Ladd, n. sp

Fossanna (Minopa) hoffmeisteri Ladd, n. sp

Astele (Calhstele.) engebiensis Ladd, n. sp

Trochus (Trofhus) maculatus Linnaeus

(Trorhus) hi.ttrio (Reeve)

incrassatus Lamarck

tubiferus Kiener

f'lanrulux (Clanculus) clanguloides ftjiensis Ladd

Tectus (Tertus) maurihanus (Gmelin)

(Tectus) pyramis (Born)

cf. T. bomasensis (Martin)

(ftortm) nihticus (Ijnnaeus)

Isanda (Parminolia) apicina (Gould)

Monilea (Monilea) mateana Ijadd

(Monilea) marshallensis Ladd, n. sp

lifuana Fischer _

belcheri (Philippi)

Stomatellidae: 

Pseudostomatella (Psc-iidostomatelta) maculata (Quov and Gaimard)

Stomatia cf. X. phymotis Helbling

Synaptocochlea, concinna (Gould)

rosacea (Pease)

lekalekana (Ladd)

marshallensis Ladd, n. sp

Angariidae : 

Angaria delphinus (Linnaeus)

Palau

v

v

v

v

Guam

v

v

v

v

X

?

Saipin 

and Tinian

v

v

v

Eniwetok

v

<i

v

v

v

X

v

v

X

X

v

v

v

v

v

X

X

X

X

v

v

v

v

X

v

X

v

v

v

v

v

v

Bikini

v

X

v

X

v

X

v

X

X

v

t

Funafuti

v

v

v

NewHebrides

v

^

v

Fiji

v

X

X

v

v

X

v

v

v

v

v

X

v

Tonga

X

v

v

v
PALEONTOLOGY 13

TABLE 4. Geographic distribution of species Continued

Species

Turbinidae : 

Atttraea (Astraliuni) rhodostoma (Lamarck)

(Astraliuni) aff. A. rhodostoma (Lamarck) _.

eniiretokensis Ladd, n. sp

iraluensis Ladd, n. sp _

sp. B__

sp. C-..___

(hellastraea) sp. D

(Bellastraea) sp. E

(Vitiastraea) holmes! Ladd, n. sp

Arene (Arent) metallilana Ladd, n. sp

Jjiotina (Australia! ia) of. L. botanira (Hedlev)

(Dentarene) loculosa (Gould)

(Denlarene) sp. A,

sp. B_._ .

Turbo (Turbo) petholatus Linnaeus. , .

(Turbo} petholattis than us Ladd _

(Marmarostoma) chrysotttomus Linnaeus

(Mai'marostoma) argyrostomus Linnaeus

setosus Gmelin?. _ .

crassits Wood- _

perlatus Abrard

sp. A . _ _

Cyniscti pacifica Ijadd, n. sp

Leptothyra niaculosa (Pease)

inepta (Gould)

harlani I^add, n. sp._

aff. L. laeta Montruzier

aff. L. Candida (Pease)

balnearii Pilsbry

irellsi Ijadd, n. sp

(/lareosa marshallensis T^add, n. subsp

picta (Pease). . ....._ ._

emenana Ladd, n. sp...

sp. A . ._ .

Phasianellidae: 

Phasianella sp

Gabrielona raunana Ladd, n. spTrirolia (Hiloa) variabilis (Pease)

(ffiloa) sp. ANeritopsidae: 

AT eritopsis (\eritopsis) radula Linnaeus

Neritidae : 

Nerita (Ani)>hinerila) inscnlpla Recluz

(Amphinerita) aff. Ar. polita Linnaeus

(Ritena) palauensis Ladd, n. sp

(Ritena) aff. N. undata Linnaeus

(Theliostyla) cf. Ar. semirugosa Recluz

(Theliostyla) sp. A .___

sp. B--.-_... ......_ __

Xeritina (Yitta) oualaniensis Lesson

Clithon (Clithon) corona (Linnaeus)

Neritilia tracet/i Ladd . _ . _ .

Smaragdia (Smaragdia) jogiacartensis (Martin)

(Smaragdia) aff. .S. rangiana (Recluz)

rolei Ladd, n. sp _ ______

1'isitlina subpacifica Ladd, n. sp

Littorinidae: 

Tectarius (Kubditoterlarius) rehderi Lad<l n. sp

Iravadiidae: 

Iraradia yardnerae Ladd, n. sp

Ripsoidae: 

Putilla (I'seudosctia) morana Ladd, n. sp

(Parrisetia) goiki/lensis Ladd, n. sp

(Parrisetia) suraensis Ladd n. sp

Cingula (Peringiella) parri/ensis Ladd, n. sp.

(Peringiella} cf. C. roseocincta (Suter)

Aniphithalmus (Cerostraca) jeffcoati T^add, n. sp

(Cerostraca!) mi/ersi T.add, n. sp

(Pisinna) bikiniensis Ladd n. sp

Alrania (Taramellia) cnrai/i Ladd, n. sp

(Taramellia) kenneyi tjadd, n. sp

Merelina (Mereh'na) pisinna (Melvill and Standen)

(Linemera) telkibana Ladd, n. sp

Paraslitpla bcetsi Ladd n. sp

Palaii

v

Guam

X

V

V

v

Saipin 

and Tinian

X

^

Eniwetok

X

X

X

v

v

X

X

v

v

^

X

^

v

V

Bikini

X

X

X

v

^

t

^

^

v

v

Funafuti

X

 >

v

NewHebrides

X

X

X

X

Fiji

X

X

?

X

X

X

X

v

X

X

X

Tonga

X

X

v

X

?
14 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

TABLE 4. Geographic distribution of species Continued

Species

Rissoidae Continued

Rissoina (Schwartziella) gracilis (Pease)

(Xctnvartziella) aff. R. flexuosa Gould

jirikana Ladd, n. sp

aff. R. suprarostata Garrett

(Phosinella) clathrata A. Adams

(Phosinella) briggsi Ladd. n. sp

transenna Watson _ .

alpxisi Ladd, n. sp__

Kiniioina (Rissoina} abbo/ti Ladd, n. sp

(Rissoina) mijana Ladd, n. sp

lomaloana Ladd, n. sp

goikulensis Ladd, n. sp

ekkanana Ladd, n. sp

ambigiia Gould

ambigua parryensis Ladd, n. subsp.

(Rissolina) marshallensis Ladd, n. sp

ephamilla Watson

herringi Ladd, n. sp

plicata A. Adams. .

sp. B. _________________

Barleeia (Barleeia) meiauhana Ladd. n. sp

Assimineidae:

Adeorbidae : Haplocochlias sp. A _ .

crossei Tryon_

? stephensoni Ladd, n. sp

Lophocochlias minittissimus (Pilsbry)

paueicarinatus Ladd, n. sp_.

MunditieUa qualum (Hedley)

Teinostoma (Esmeralda) engebiense Ladd n. sp

(Esmeralda) marshallense Ladd, n. sp ______

sp. A_ _

Solariorbis tricarinata (Melvill and Standen)

? sp.__. ________ .... .___

Lydiphnis eniwetokense Ladd, n. sp_

Cyclostrerniscus emeryi Ladd, n. sp

(Ponocyclus} novemcarinatus (Melvill)

(Ponocyclus) cingulifera (A. Adams) ....

Cochliolepis diangalana I, add, n. sp

VitrineUa sp. A

Total of 208 occurrences _ _

Palau

v

^

18

Guam

14

Saipin 

and Tinian

8

Eniwetok

v

v

v

^

^

^

v

v

v

^

v

^

v

v

v

v

v

v

122

Bikini

?

X

X

v

v

^

v

66

Funafuti

8

New 

Hebrides

X

10

Fiji

X

X

X

v

47

Tonga

X

X

14

The thousands of feet of reef-associated limestones 

that underlie Eniwetok and Bikini do not record slow 

and continuous subsidence. On the contrary, as Schlanger 

(1963) has shown, the section is interrupted by "solution 

unconformities" that record periods when the atolls stood 

above the sea as high islands, and their limestones were 

leached and recrystallized. This interpretation is 

strengthened by the occurrence of spores and pollen that

indicate a richer and more varied flora during part of the 

Miocene than is found in the area today (E. B. Leopold, 

unpub. data I. It is strengthened, likewise, by the occurrence of high-island fossil land shells of the genus 

Ptychodon at both Eniwetok and Bikini (Ladd, 1958) 

and by the occurrence of fresh- and brackish-water mollusks Neritilia and Gyraulus in the Miocene beds 

beneath Bikini, an area where no such animals live
PALEONTOLOGY 15

today. When it stood above the sea, Bikini evidently 

contained both fresh- and brackish-water pools near sea 

level, as do many elevated limestone islands today 

(Ladd, 1965).

Shallow-water mollusks occur in normal abundance in 

the reef limestones that lie beneath Funafuti Atoll, but 

because much of the rock that was drilled is leached, 

reerystallized, or dolomitized, shells are poorly preserved. Only eight mollusks from Funafuti are named 

in this report, and half of these are small forms recovered 

from the unaltered sands obtained at depths of less than 

100 feet. None of the mollusks was found in the parts of 

the section that yielded Cycloclypeus. According to the 

interpretation of Grimsdale (1952), the limestones containing this foraminifer were deposited under open-sea 

conditions on a reef talus slope or a submerged bank.

I have not visited the New Hebrides and have no firsthand information about the fossil associations in the 

sediments of those islands. From all a'ccounts, the exposed rock sections are similar to those of Fiji: Miocene 

marls with included shallow-water limestones that contain many of the mollusks and brachiopods that have 

been recorded from Viti Levu (Abrard, 1946), and terraced reef limestones of post-Miocene age appear to be 

similar to those of eastern Fiji (Lau).

An attempt to interpret the ecological conditions under 

which the several types of fossiliferous sediments of Viti 

Levu, Fiji, were accumulated was made by Ladd in 1934 

(in Ladd and others, 1934, p. 87-97), and a similar discussion on the sediments of eastern Fiji (Lau) was made 

by Ladd and Hoffmeister in 1945 (in Ladd, Hoffmeister, 

and others, 1945, p. 260-264). These discussions could 

be somewhat amplified now (1965), but a full analysis 

depends on complete studies of other groups of mollusks. 

Two short papers involving Fijian paleoecology have 

been written since the two general discussions mentioned 

above were published. G. F. Elliott described the first 

fossil example of. the deepwater brachiopod Abyssothyris 

which was collected from limestones in the upper Tertiary 

Suva Series near Suva, Fiji. (Elliott in Muir-Wood 

1960, p. 256). Additional specimens of this rare brachiopod have since been collected by William Briggs of the 

U.S. Geological Survey and by others of the Geological 

Survey Department of Fiji from the marls that enclose 

the Suva Limestone. Heinz Lowenstam of the California 

Institute of Technologoy is making analyses of the shell 

substance in an attempt to determine the temperature 

and hence the depth under which the brachiopod may 

have lived.

In a recent paper I (1965) reinterpreted the Suva beds 

that yielded the river snail Clithon corona Linnaeus as 

a reef flat or shore platform. I also described an unusual

upper Tertiary deposit from northern Viti Levu that 

appears to have been laid down in the fresh or slightly 

brackish waters of a coastal swamp or bog. The deposit 

contains numerous examples of a fresh-water snail, 

Melanoides, with lignitic material and the pollen and 

spores of land plants, including mangrove.

The only Tertiary mollusk that has been described 

from Tonga is a nautiloid collected by Hoffmeister 

(19321 from bedded tuffs on the island of Eua that are 

probably Miocene in age (Miller 1941). Quaternary 

mollusks collected on Tongatabu and elsewhere by Ostergaard (1935) were obtained from elevated reef limestones 

that are probably Pleistocene in age. None of the 14 

species identified in the present report is extinct. The 

abundant forms are trochids and turbinids that live 

today on reefs in the same area.

FAUNAL RELATIONS

A full discussion of this subject, like that of paleoecology, must await the completion of studies of other groups 

of mollusks, but it is possible, at this time, to consider 

briefly certain relationships that are suggested by the 

group of more than 200 species described in the present 

report.

The assemblages of fossil mollusks from the island 

area are clearly Indo-Pacific in general aspect, the strongest discernible ties being with the living and fossil faunas 

of tropical Indonesia rather than with faunas from more 

southerly areas (south Australia and New Zealand) or 

more northerly areas (the Ryukyu Islands and Japan). 

Most biogeographers, including those concerned with 

marine mollusks, have recognized this relationship and 

have supported the conventional interpretation that 

Indonesia is the center of dispersal and that there is a 

gradual attenuation in numbers of species from Indonesia 

eastward and north eastward into the open Pacific (Hedley, 1899a, p. 397-401; 1899b; Edmondson, 1940, p. 598; 

Ekman, 1953, p. 18; Solem, 1958, p. 18).

One of the objections to this theory of origin and dispersal is the fact that the prevailing winds, the storm 

winds, and the strongest ocean currents all trend from 

the island area toward Indonesia, rather than away from 

it. Consequently, some workers have postulated circuitous routes of migration, and I have suggested that 

much of the traffic may have been in the opposite direction. The known geological history of the area indicates 

that during the Tertiary many more reef and island 

stepping stones were available in the western Pacific 

than are there now (Hamilton, 1956), and it would have 

been much easier for many marine animals to make their 

way from Hawaii in the central Pacific to Indonesia 

(Ladd, 1960; Durham, 1963, p. 356). Hawaii is not
16 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

TABLE 5. Geologic distribution of species

Species

Schizochitonidae :

marshallensis Ladd, n. sp--- - -- ___. - _-_._

Loncella sp. A _. - ___- ._ --- _.- ._-- __ __. 

Chitonidae :

sp B

SP---.. --------.---_-----_.- -_----------_----------_--__------

Acanthochitonidae :

Haliotidae:

Scissurellidae : 

ScissureUa (Scissurella) declinans Watson __ _ _ . __ _ _ - __

(Anatoma) equator ia Hedlev - - -- _.. .. 

Fissurellidae :

(Emarginula) cf. E. peasei (Thiele) --------

(Subzeidora) souterbiana Pilsbry -. --- - -----.-_---_-_-- 

(Subzeidora) sp. A _______ __. _ _ _ _ _ . _ . . __ _-__

(Montfortia) sp. A-_____ _ . _ . - . . - _- . . . . - . . .

(Montfortista) excentnca (Iredale)- - .__---_ --.. _ _- ______

Diodora (Elegidiori) marshallensis Ladd, n. sp ~

(Elegidiori) aff. D.granifera (Pease) __ _ ___- . .. _ ___ -._

Patellidae:

? sp

Trocludae:

(Herpetopoma) instrictus suvaensis Ladd, n. subsp. ... 

(Vaceuchelus) angulatusPea.se-.- _ - . _._ . _ ..

(Vaceuchelus) sp. A_ _ _-_-_-_ . ..-. .- ._ -.._ -__

Thalotia (Thalotia) berauensis (Beets) ______ __ ._.. __ ___ _. _

Gibbula (Oibbula) engebiensis Ladd, n. sp_-_ . . _ - 

Fossarina (Minopa) hoffmeisteri Ladd. n. sp . . - -.._.. 

Astele (Callistele) engebiensis Ladd, n. sp . _ _ 

Trochns (Trochus) maculatus Linnaeus _ -___ .._ ___

(Trochus) histrio (Reeve), -_ __ 

inrrassatus Lamarck- _. . . . _

tubiferus Kiener _ . . _ _ _ -_..__

Tectus (Tectus) maiiritianus (Gnielin) _ ._ . _ _ .

(Tertus) pyramis (Born)___ __ . _ . . 

ff. T. bomasensift (Martin) _ . _ _

Monilea (Monilea) mateana Ladd _ . 

(Monilea) marshallensis Ladd, n. sp _ _ _ _ . _ -__

bdcheri (Philippi), . . __ . . . . . . __ _ -_ _

Tertiary

e f

o<

S £ 

^ 2

,3 3

?

?

« ? ~-m 

mm^m ? « 

? -mll

 f

a

Upper Miocene

?

?

?

h

Pliocene

?

^^B ? ^^__

Quaternary

Pleistocene

__ ?

?

?

Recent so

3
PALEONTOLOGY 17

TABLE 5. Geologic distribution oj species Continued

Species

Stomatellidae: 

PseudostomateUa (Pseudostomatella) rnaculata (Quoy and Gaimard)

Stomatia cf. .1 phymotis Helbling

tiynaptocochlea concinna (Gould),

rosacea (Pease)

lekalekana (Ladd) -.-_-.

rnarshaUensts Ladd, n. sp.

Angariidae: 

Angaria delphinus (Linnaeus)

Turbinidae: 

Astraea (Astralium) rhodostoma (Lamarck)

(Astralium) aff. A. rhodostoma (Lamarck)

eniwetokensis Ladd, n. spwaluensis Ladd, n. sp

sp. A. . _ .

sp. B ___

sp. C-..-_ _ """"

(Bdlastraea) sp. D.___ _

(T itiastraea) holmest Ladd, n sp.

Arene (Arene) metaltilana Ladd, n. sp

(Arene) sp. A. . _ __ _

Liotina (Austrohotia) cf. L. botanica (Hedley)

(Dentarene) loculosa (Gould)

sp. B ._

Turbo (Turbo) petholatus Linnaeus. .

(Turbo) petholatus thanus Ladd

(Marmarostoma) chrtjsostomus Linnaeus

(Marmarostomd) argyrostomus Linnaeus

setosus Gmelin?

perlatus Abrard --..

sp. A _ _

Cynisra pacifica Ladd, n. sp .

Leptothyra maculosa (Pease)

harlani Ladd, n. sp_ _

aff. L. laeta Montrouzier

aff. L. Candida (Pease)

balneani Pilsbry

wellsi Ladd, n. sp. .

glareosa marshallensis Ladd, n. sp

emenana Ladd, n. sp-_ .

Phasianellidae: 

Phasianella sp._ _

Gabnelona raunana Ladd, n. sp

Trirolia (Htloa) ranabilis (Pease)

(Hiloa) sp. A... -----------

Neritopsidae: 

Neritopsis (Neritopsis) radula Linnaeus

Neritidae : 

Nerita (Amphinerita) insculpta Recluz

(Amphmerita) aff. N. polita Linnaeus

(Ritena) palauensis Ladd, n sp

(Ritena) aff. N. undata Linneaus

(Theliostyla) cf. N. semirugosa Recluz

(Theliostyla) sp. A

sp. B_.._. .

^entina (T itta) oualamensis Lesson

Chthon (Chthon) corona Ijnnaeus

Srnaragdia (Smaragdia) jogjacartensis (Martin)

(Smaragdia] aff. &. rangiana (Recluz)

colei Ladd, n. sp

Pisuhna subpacifica Ladd, n sp

Littorinidae : 

Tectarius (Subditotectarius) rehderi Ladd, n. sp

Iravadiidae: 

Iravadia gardnerae Ladd, n. sp

Tertiary

e f

<Da

?- c;

0 0

'* .2 3 §

?

?

 f

|

_ ? ^^ ^ ? ^^_

g

Upper Miocene

h

Pliocene

^^m ? ^^m

 >

7

9

Quaternary

Pleistocene

^^^ 9 ^^^

Recent M
18 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

TABLE 5. Geologic distribution o} species Continued

Species

Rissoidae :

Putilla (Pseudosetia) morana Ladd, n. sp _.. _ _

(Parvisetia) goikulensis Ladd, n. sp. . ----- _._

suvaensis Ladd, n. sp_

Cingula (Peringiella) parryensis Ladd, n. sp___. . ___ . .

(Peringiella) cf. C. roseocincta (Suter) _ __

Amphithalmus (Cerostraca) jeffcoati Ladd, n. sp

(Cerostraca?) myersi Ladd, n. sp _ _

(Pisinna) bikiniensis Ladd, n. sp_ --_---__

Alvania (Taramellia) corayi Ladd, n. sp

(Taramellia) kenneyi Ladd, n. sp __

Merelina (Merelina) pisinna (Melvill and Standen)

(Linemerqft telkibana Ladd, n. sp_ _ _

Parashiela beetsi Ladd, n. sp_

Zebina (Cibdezebina) metaltilana Ladd, n. sp

(Morrhiella) cf. Z. cooperi (Oliver) _

(Morchiella) killeblebana Ladd, n. sp . - .

(Ailinzebina) abrardi Ladd, n. sp

? sp. A .. _.-.--______ . -

Rissoina (Schwartziella) gracilis (Pease) . . _ _ .

(Schwartziella) aff. R. flexuosa Gould

aff. R. indrai Beets.

mejilana Ladd, n. sp.____

jirikana Ladd, n. sp

rilebana Ladd, n. sp ______

(Zebinella) emnanana Ladd, n. sp_

(ZebineUa) tenuistriata Pease _.__

aff. R. supracostata Garrett

(Phosinella) clathrata A. Adams. _-. - . _.

(Phosinella) briggsi Ladd, n. sp

balteata Pease. - -_.___

bikiniensis Ladd, n. sp __--_ ______ _

transenna Watson _

alexisi Ladd, n. sp._____

(Rissoina) abbotti Ladd, n. sp _. __

(Rissoina.) mijana Ladd, n. sp_ _ _

ailinana Ladd, n. sp_

lomaloana I^add, n. sp

goikulensis Ladd, n. sp

waluensis Ladd, n. sp

ekkanana Ladd, n. sp

ambigua GoulcL . . .

ambigua parryensis Ladd, n. subsp__ _ __

concinna A. Adams. _

sp. A_. .__.__ __

(Rissolina) turricula Pease. .... _

(Rissolina) marshallensis Ladd, n. sp

ephamilla Watson __ _ _

ktckarayana Ladd, n. sp_-.._-

herringi Ladd, n. sp.

harti Ladd, n. sp..-_

bourneae Ladd, n. sp_ _ _

plicata A. Adams _

sp. B_____._.___ _ ' ' "

Barleeia (Barleeia) meiauhana Ladd, n. sp

Assimineidae: 

Assiminea nitida eniwetokensis Ijadd, n. subsp

Adeorbidae: 

Haplocochlias sp. A_

Leitcorhynchia caledonica Crosse

crossei Tryon

? stephensoni Ladd, n. sp. ? lilli Ladd, n. sp ----------------

Lophocochlias minutissimus (Pilsbry)

pauacarinatus Ladd, n. sp

Mundthella gualum (Hedley)

parryensis Ladd, n. sp

Temostoma (Esmeralda) engebiense I.add, n. sp

(Esmeralda) marshallense Ladd, n. sp

Xolanorbis tncannata (Melvill and Standen)

Lydiphnis eniwetokense Ladd, n. sp

Tertiary

e /

£ 

S3 £ 

* 2 

3 §

?

?

?

g

Upper Miocene

9

h

Pliocene

Quaternary

Pleistocene Recent st
PALEONTOLOGY 

TABLE 5. Geologic distribution of species Continued

19

Species

Tertiary

Quaternary

included in the present study, but geological evidence 

suggests that the group may have been in existence since 

Cretaceous time (Ladd, 1961, p. 714-715; Menard and 

Hamilton, 1963, p. 203; Durham, 1963 p. 358). In this 

connection it should be noted that shallow-water mollusks, perhaps of Miocene age, recently have been 

dredged from a depth of 500-520 meters off the island of 

Oahu in Hawaii (Menard and others, 1962). The present 

study offers no decisive evidence on the important questions of origin and migration, but the past and present 

distribution patterns of some of the mollusks provide 

evidence, as shown below.

Many mollusks that live today in the island area have 

been there since late Tertiary time. A total of 33 such 

species are listed in table 6. Twenty five of these were 

recovered from deep drill holes in the Marshall Islands 

and 11 from outcrops in Fiji. Table 6 also shows the 

distribution of a few Indo-Pacific species that no longer 

live in the island area though they were there during the 

Tertiary. The island-area species that now live in Indonesia and the Indian Ocean are more numerous than 

those that now live in the Ryukyu Islands and Japan.

Not listed in table 6 are numerous living IndoPacific species that had close relatives, some of which 

perhaps were ancestral, in the island area during the late 

Tertiary. Such relationships are noted in the discussions 

of individual species in the systematic section. Several 

of these may be significant. The presence in the upper 

Miocene of Bikini of a species of the neritid Pisulina, 

which has a characteristically large median tooth, ex^ 

tends the range of that genus geographically as well as 

geologically. Pisulina has been known previously only 

from a few species living near India and Ceylon. An 

even greater geographic gap separates the single lower 

Miocene Cynisca of Eniwetok from a half dozen Recent 

species, all of which live today at the extreme western

end of the Indo-Pacific, off the Cape of Good Hope, South 

Africa.

The reef chiton Schizochiton, which has extraordinary 

large eyes, is another genus not previously reported as a 

fossil. Representatives lived on Eniwetok during the 

Miocene (Tertiary e and g) and in Palau (Tertiary g). 

The genus lives today in the Philippines, Shouten 

Islands, and northern Australia. On the basis of available information, it can be regarded as a genus that 

started in the island area and migrated to the southwest 

where it has persisted.

Evidence of the type given above is suggestive but certainly not conclusive. If more were known about the 

Tertiary of Indonesia, India, and South Africa, it might 

be discovered that the genera cited were living in those 

places as well as in the island area during the Miocene.

Suggestive evidence of another sort is found in the 

occurrence of Haplocochlias in the upper Miocene of 

Eniwetok. This genus, not previously reported as fossil, 

is known only from the waters off Baja California, from 

the southern tip of the peninsula to Bahia Magdalena 

175 miles to the northwest. An eastward migration from 

the Marshalls to the west coast of North America is difficult to explain even with the help of the Equatorial 

Counter Current. Two species of Arene have also been 

found in the Miocene of Bikini. This group is West 

Indian where it has been represented from the Miocene 

to Recent. More information is needed on the geological 

and geographical distribution of the rare genera Haplocochlias and Arene.

Some ties between the island-area fossil faunas and 

those described from the upper Tertiary of Indonesia 

have been recognized. Thalotia berauensis described by 

Beets (1941, p. 13) from the upper Miocene of East 

Borneo occurs in the lower Miocene (Tertiary /) of 

Eniwetok. The lower Miocene Topochau Limestone of
20 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

TABLE 6. Living Indo-Pacific molluskK that also occur in upper Tertiary sediments of island area

Species

Scissuretta (Scissurella) dedinans Watson

Rimula exquisita A. Adams

Euchelus (Herpetopoma) instrictus (Gould)

(Vaceuchelus) angulatus Pease

Turcica (Perrinia) marrisoni Ladd, n. sp

Fossarina (Minopa) hoffmeisteri Ladd, n. sp

Trochus (Trochus] maculatus Linnaeus

(Trochus) histrio (Reeve)

Isanda (Parminolia) apicina (Gould)

Pscudostomatella (Pseudostomatella) inaculata 

(Quoy & Gaimard)

Synaptocochka rosacca (Pease)

Angaria delphinus (Linnaeus)

Liotina (Dentarene) cycloma Tomlin

Turbo (Turbo) petholatus Linnaeus

(Marmarostoma) chrysostomus 

Linnaeus

(ftlarmarostoma) argyrostomus Linnaeus

Leptothyra maculosa (Pease)

balnearii Pilsbry

glareosa marshallensis Ladd, n. sp

Neritopsis (Neritopsis) radula Linnaeus

Nerita (A mphinerita) insculpta Recluz

Clithon (Clithon) corona (Linnaeus)

Merelina (Merelina) pisinna (Melvill and Standen) _ 

Zebina (Cibdezebina) metaltilana Ladd, n. sp

(Ailinzebina) abrardi Ladd, n. sp

Rissoina (Zebinella) tenuistriata Pease

(Phosinella) clathrata A. Adams

balteata Pease

transenna Watson

(Rissolina) turricula Pease

ephamilla Watson

plicata A. Adams

Lophocochlias minutissimus (Pilsbry)

Solariorbis tricarinata (Melvill and Standen)

Cyclostremiscus (Ponocyclus) novemcarinatus (Melvill)--^.

(Ponocyclm) cingulifera (A. Adams)

Total

Living

Indian 

Ocean

X

X

X

X

X

X

X

X

X

X

X

11

Indonesia 

and 

northern 

Australia

X 

X

X

X 

X

X

X

X

X

X 

X

X

X

13

Ryukyu 

and 

Japan

X 

X

X 

X

X 

X 

X

X 

X

X 

X

X

12

Island 

area

X 

X 

X 

X 

X

X 

X 

X 

X

X 

X

X 

X

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X

X

33

Upper Tertiary

Palau

X

X

2

New 

Hebrides

X '

1

Fiji

X

X

X

X

X

X

X

X

X

X

X

11

Mariana 

Islands

X

X?

X 

X?

X?

X

6

Marshall 

Islands

X 

X 

X

X 

X

X

X

X

X 

X 

X 

X 

X

X 

X 

X 

X

X 

X 

X 

X 

X 

X 

X

X

25

Saipan yielded a poorly preserved Thalotia referred to 

the subgenus Beroua, which was established by Beets 

(1941, p. 14) for T. erinaceus from the same Borneo beds. 

The Saipan shell closely resembles Beets' type species. 

The Borneo beds and the lower Miocene of Eniwetok 

also have in common the Recent species Cyclostremiscus 

novemcarinatus (Melvill), and an Eniwetok lower 

Miocene rissoid seems closely related to Beets' Rissoina 

indrai. A chiton described by Beets as Cryptoplax 

menkrawitensis has a close relative in the Miocene of 

Fiji.

The neritid described by Martin from the lower 

Miocene of Java as Neritina jogjacartensis is a Smaragdia 

that occurs throughout the Miocene under Eniwetok and 

in the upper Miocene of Palau. Another of Martin's

lower Miocene Java species, Tectus bomasensis, may be 

identical with a species from the Miocene of Fiji. Several 

still-living species are common to the upper Tertiary of 

the island area and Indonesia.

SYSTEMATIC PALEONTOLOGY

The systematic order followed is, in general, that used 

in "Indo-Pacific Mollusca" under the editorship of R. T. 

Abbott (1959); this arrangement, in turn, is based on 

Thiele (1929-31) and Wenz (1938-44). An exception is 

made for the chitons. They are considered before the 

gastropods rather than after them, and the systematic 

order given in the "Treatise on Invertebrate Paleontology" is followed (Smith, 1960).

Drill-hole specimens taken from cores are so identified; 

all other drill-hole specimens were picked from cuttings.
PALEONTOLOGY 21

Depths of many cuttings samples have been rounded to 

the nearest foot.

The following new subgenera are proposed: 

Vitiastraea, subgenus of Astraea, Turbinidae. 

Type: Tectarius rehderi Ladd, n. sp. 

Suva Formation, lower Miocene (Tertiary /), Fiji,

page 45. Gender feminine.

Subditotectarius, subgenus of Tectarius, Littorinidae. 

Type: Tectarius rehderi Ladd, n. sp. 

lower Miocene (Tertiary /), Bikini, Marshall

Islands, page 59. Gender masculine. 

Ailinzebina, subgenus of Zebina, Rissoidae. 

Type: Zebina abrardi Ladd, n. sp. 

Recent. Bikini, Marshall Islands, page 65.

Gender feminine.

One-third of the 75 new species and subspecies described arc represented by only 1 or 2 specimens. Of 

these 25 poorly represented forms, 2 are from Palau, 2 

from Fiji, and the balance from drill holes in the Marshall 

Islands. Future collecting in Palau and Fiji may yield 

additional specimens of rare species, but there is little 

prospect of additional drilling in the Marshall Islands. 

The rare Marshall Island species can be looked for, however, when reef drilling is undertaken in Hawaii or 

another part of Polynesia.

CHITONS

Most chitons ai'e rock clingers and are found most 

abundantly on rocky shores. They are not limited to 

such shores, however; even along beach coasts they may 

find some sort of hard surface such as the shell of a 

dead oyster to which they may adhere.

As a group, the chitons of the existing seas are particularly abundant in the Australian region where some 

200 species have been identified. In that area also, fossil 

forms have been described from upper Tertiary and 

Pleistocene beds.

Many reef-encircled islands in the Pacific offer favorable niches for chitons. Chitons may be particularly 

abundant in the nips that are developed at high-tide level 

along most limestone coasts, and they may also be found 

on blocks of reef rock on reef flats. Coral itself is not a 

choice base because most chitons feed on vegetation. 

Hull < 1925, p. 12), in working on the Great Barrier Reef, 

found that only carnivorous species of Cryptoplax, 

Schizochiton, and some species of Acanthochitona are to 

be expected on living coral. Some of these chitons are 

specialize I forms adapted to living in holes or crevices 

in coral. Only a single specimen of one of the three 

genera mentioned by Hull was collected from the Recent 

fauna in the Marshall Islands during the investigations 

of 1945-46 (a Cryptoplax found between tide levels on

Eniwetok), but representatives of all three genera were 

recovered from the Tertiary sections drilled in the Marshall Islands. In addition, a Cryptoplax was collected 

from the Miocene reef and reef-flat deposits in Fiji and 

Palau; the Palau deposits also yielded Schizochiton.

No fossil chitons were obtained in the Mariana or the 

New Hebrides Islands, and only a single undetermined 

valve has come from Tonga. The Marshall Island drill 

holes and the marly upper Tertiary deposits of Palau and 

Fiji yielded the most specimens. In addition to the described material, a total of 26 undetermined specimens 

were obtained in the island area.

Order NEOLORICATA 

Family SCHIZOCHITONIDAE

Genus SCHIZOCHITON Gray

Gray, 1847, Zool. Soc. London Proc., p. 65, 68, 169.

Type (by monotypy): Chiton incisus Sowerby. 

Philippines, Torres Straits, northeast Australia.

Schizochiton includes elongate chitons characterized 

by a deep fissure in the tail valve and by the development of lines of prominent ocelli on all valves. On reefs 

they live in protected spots, under blocks, or in crevices 

in dead coral.

Schizochiton incisus goikulensis Ladd, n. subsp.

Plate 1, figures 1-3

Tail valve large, thick; dorsal ridge flattened, lateral 

pleural areas gently concave, lateral posterior areas tricostate; entire surface covered by strong slightly flattened ribs that are distinctly narrower than the flattened 

areas between; ribs tend to parallel anterior margin of 

lateral pleural areas but follow a zigzag course, best 

developed on the left side; 22 ribs on right side, 21 on 

left. Lateral-posterior areas less strongly ribbed than 

lateral pleural areas, those of the left side more irregularly angled than those on the right; 15 ribs are distinguishable on right side, 19 on left; large eyepits present 

where ribs meet diagonal costae of lateral-pleural areas. 

Deeply excavated caudal sinus with pustulose surface 

leads to prominent mucro; on'sides of sinus the pustules 

arc roughly alined in rows. Interior of valve smooth 

near center, irregularly ridged at sides; sinus broadly 

V-shaped with low rounded projections into apex of V; 

sutural plates broad and regular; posterior insertion 

plates cut by three prominent slits on each side; teeth 

stout, distinctly crenulated outside.

Measurements of valve (holotype), USNM 648208: 

length 10.0 mm, width 9.6 mm, convexity 4.5 mm.

The above description is based on a single well-preserved specimen. It has been compared with specimens 

of the Recent S. incisus Sowerby (Sowerby, 1841, p. 61;
22 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Pilsbry, 1892, p. 235-236, pi. 51, figs. 1-8) from the 

nearby Philippines and Schouten Islands. The fossil is 

larger and has a greater number of ribs and an unusually 

well developed pustulose surface in the caudal sinus.

Occurrence: Marl fades at base of the Miocene (Tertiary g) Palau Limestone (USGS 21301), near village of 

Goikul, Babelthuap, Palau.

Schizochiton marshallensis Ladd, n. sp. 

Plate 1, figures 4-9

Head valve with six prominent lines of close-set ocelli; 

each of two outermost rows having about 20 pits each, 

the inner four rows with about 30 each; surface between 

rows marked by close-set zigzag ridges separated by 

grooves of about the same width. In the single worn 

specimen, the ridges form a series of chevrons between 

each two rows of ocelli, the angle formed by the ridges, 

pointing forward.

Intermediate valves beaked, lateral areas narrow and 

slightly elevated, separated from central area by a strong 

diagonal bearing a dozen or more ocelli; surface of entire 

valve crossed by flattened more or less zigzag ridges that 

on most specimens are much narrower than the spaces 

separating them; dorsal ridge broadly rounded having 

flattened longitudinal ridges that meet with the ridges 

of the central area to enclose irregular and diamondshaped depressions. On valves believed to represent second valves, the flattened ridges of the central area extend 

only one-third to one-half way to the main dorsal ridge 

before meeting a series of longitudinal ridges to form a 

diamondback pattern; insertion plates with single slit.

Tail valve large, thick; dorsal ridge rounded; lateral 

pleural areas concave; lateral posterior areas with 4 

prominent ocelli-bearing costae on the right side and 4 

or 5 on left; insertion plates with 4 prominent slits on 

each side; sculpture similar to that of other valves; flattened ribs on lateral pleural areas range from 14 to 20; 

surface of caudal sinus rough with traces of chevronshaped ridge pattern pointing toward mucro.

Measurements of the types (in mm) :

Length Widtlt Convexity

Holotype

(a tail valve, E-l, Eniwetok,

870-880 ft), USNM 648209 ____ 8.2 7.8 4.6 

Paratype A

(a head valve, F-l, Eniwetok,

740-750 ft), USNM 648210 ____ 5.5 5.7 3.0 

Paratype B

(a second valve, F-l, Eniwetok.

750-760 ft), USNM 648211 ____ 7.2 6.4 3.9 

Paratype C

(a second valve, 2A, Bikini,

1,030-1,034 ft) USNM 648212 __ n 3.1 

Mcas irmenls of the types (in mm) Continued

Length Width Convexity

Paratype D

(an intermediate valve,

E-l, Eniwetok,

830-840 ft). USNM 648213 ____ 4.1 4.0 1.4 

Paratype E

(an intermediate valve,

2A, Bikini,

893-899 ft), USNM 648214 ____ X 3.3 

1 Incomplete.

S. marshallensis differs from the Recent S. incisus 

Sowerby and the new7 subspecies S. incisus goikulensis 

by having four or five posterior ridges on each side of the 

posterior valve. >S. incisus goikulensis does not show-the 

chevron-shaped ridge pattern in the caudal sinus exhibited by S. marshallensis and by some specimens of 

>S. incisus. The Recent 8. polyps Iredale and Hull has a 

jugum that is smooth or nearly so.

Occurrence: Nineteen separate valves, believed to 

represent a single species, were recovered from cuttings 

from the three deep holes on Eniwetok and one of the 

deep holes on Bikini. The youngest specimen, from a 

depth of 660-670 feet, is in beds assigned to Tertiary g, 

and the oldest, from a depth of 2,610-2,620 feet, is in 

beds referred to Tertiary e. The valves are rare, and only 

twice were two specimens found in a single sample. The 

stout tail valves show the most diagnostic features, and 

a total of seven such valves were recovered; one of these, 

from a depth of 870-880 feet in drill hole E-l on Eniwetok, is the holotype. Only one head valve was found, 

paratype A, depth 740-750 feet in hole F-l on Eniwetok. The remaining 11 specimens are intermediate 

valves, 3 being No. 2 valves showing the jugum.

Genus LORICELLA Pilsbry

Pilsbry, 1892, Manual Conchology, v. 14, p. 288.

Type (by monotypy): Lorica angasi H. Adams (in 

Adams, H., and Angas, G. F., 1864, Zool. Soc. London 

Proc., p. 193). Recent, Australia.

Loricella sp. A 

Plate 1, figures 10-12

Head valve broadly arched, nearly twice as wide as 

long; insertion plate narrow, pectinate, cut by 10 slits. 

Upper surface of valve smooth near median apex; remainder of surface with 13 radial rows of beads; the 

beads elongated parallel to anterior margin of valve; 

beads in row next to posterior margin on each side rise 

from a moderately strong rib. Measurements of the figured head valve (F-l, 55-60 ft), USNM 648215: length 

1.6 mm, width 2.8 mm, convexity 1.1 mm.

Intermediate valve highly arched and slightly beaked; 

jugum smooth; remainder of valve crossed by 14 ribs on
PALEONTOLOGY 23

each .side, the 3 ribs nearest the jugum being smaller than 

the others; lateral areas each with 4 diagonal ribs, the 

anterior and posterior ones larger than the others and 

bearing obscure ocelli on the beads formed by the crossing of the vertical ribs. On the single fossil available, the 

insertion plates are not preserved. Measurements of the 

figured intermediate valve (E-l, 35-40 ft), USNM 

648216: length (minus insertion plates) 2.0 mm, width 3.6 

mm, convexity 1.5 mm.

The fossils do not appear to be closely related to described species, but they may be immature and a specific 

name is withheld. The species may be still living in the 

Marshall Islands, though no specimens have yet been 

collected. The genus is widely known from the AustraliaIndonesia area but appears not to have been previously 

reported from the islands of the open Pacific.

Occurrence: One head valve and one intermediate valve 

from drill hole E-l on Eniwetok Atoll at depth of 35-40 

feet and one head valve from F-l at depth of 55-60 feet; 

age, Recent.

Family CHITONIDAE 

Genus LUCILINA Dall

Ball, 1882, U.S. Natl. Mus. Proc., 4, p. 284, 287, (= Lucia Gould, 

1862, Boston Soc. Nat. History Proc., v. 8, p. 283; [not] 

Swainson, 1833).

Type (by monotypyl: Chiton confossus Gould. Recent, Fiji.

Lucilina russelli Ladd, n. sp. 

Plate 1, figures 13-15

Tail valve .small, moderately arched, thick; mucro 

prominent, lying directly above the posterior edge of the 

valve; profile below and above mucro gently convex; 

sinus wide, its flat bottom pectinated; anterior insertion 

plates broadly rounded, their outer edges pectinated 

above; posterior insertion plates short, thick, inclined 

forward, strongly grooved outside and cut by numerous 

(about 16) slits. In front of a broad ridge extending 

from the mucro to the anterior corners, the surface bears 

numerous slightly curved vertical riblets; surface posterior to ridge microscopically punctate with scattered 

larger pits that represent ocelli; obscure elevated horizontal lines cross the post mucral area.

Measurements of the holotype (only specimen), 

USNM 648217: length 4.1 mm, width 6.2 mm, convexity 

2.7 mm.

The Eniwetok fossil is very closely related to the 

Recent /,. confoxsus (Gould) (USNM 30763), but the 

Recent shell does not show the vertical riblets on the 

anterior part of the valve that are so well developed on 

the fossil; the Recent shell likewise has a stronger ridge 

from mucro to the anterior corners.

Occurrence: Drill hole Kl-B on Eniwetok Atoll at a 

depth of 537-548 feet; age, probably Pliocene.

Lucilina sp. A

Plate 1, figure 16

Tail valve small, gently arched, moderately thick; 

mucro about one-third the length from the posterior 

margin; area behind broadly convex, surface in front 

nearly flat; bottom of sinus pectinated; posterior insertion plates short, inclined forward, strongly grooved 

outside, and cut by numerous slits. A narrow and prominent ridge extends from the mucro to the anterior 

corners; ahead of the ridge the jugum is smooth, but the 

remainder of the central area bears an irregular series of 

pitted grooves that are best developed near the anterior 

margin; low elevated lines cross the entire central area 

parallel to the anterior margin of the valve. Posterior 

to the mucro the surface is smooth except for scattered 

ocelli and obscure elevated lines that parallel the posterior margin.

Measurements of the figured specimen, USNM 648219: 

length (insertion plates missing) 2.1 mm, width 3.9 mm, 

convexity 1.2 mm.

This species superficially resembles L. confossus 

( Gould), but its well-developed pitted grooves are not 

found on the Recent shell. Lucilina sp. A differs from 

L. russelli in having more widely spaced vertical grooves 

and a more prominent ridge from mucro to the anterior 

corners. The single specimen is incomplete, and a specific name is withheld.

Occurrence: Marl facies at base of the Palau Limestone (USGS 21304), near village of Goikul, Babelthuap, 

Palau; age, late Miocene (Tertiary g).

Lucilina sp. B

Plate 1, figure 17

Tail valve medium in size, moderately arched, thick; 

mucro prominent, situated almost directly above posterior 

margin; surface below mucro slightly concave; sinus 

broad, flat-bottomed, and pectinate; anterior insertion 

plates wide and flat; insertion plates along the posterior 

and lateral margins thick, strongly grooved externally, 

and cut by numerous shallow slits. Surface of valve 

eroded but showing traces of close-set riblets that diverge 

from a broad ridge that extends from the mucro to the 

anterior corners of the valve.

Measurements of the figured specimen (Fiji sta. HOB), 

USNM 648218: length 6.5 mm, width 10.3 mm, convexity 4.0 linn.

On a poorly preserved intermediate valve from the 

same locality, a low, narrow ridge separates the pleural 

areas from the central area; traces of fine vertical riblets 

are preserved on the jugum and a fanlike pattern of
24 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

similar lines is; discernible on the rest of the central area. 

The valve measures 19.2 mm in width.

The illustrated Fijian fossil resembles the "Recent L. 

confossus described by Gould from Fiji but has a lower 

mucro and the vertical riblets of the central area that are 

well developed on the fossil are not present on the Recent 

shell.

Occurrence: In the Ndalithoni Limestone; age, probably Pliocene (Tertiary h) ; Vanua Mbalavu, Fiji (sta. 

HOB). Two similar but more coarsely ribbed tail valves 

from the Miocene Suva Formation; age, Tertiary /; Viti 

Levu, Fiji (sta. FB20), and from drill hole F-l on Eniwetok at a depth of 320-330 feet (Tertiary h or Pleistocene) are questionably referred to this species.

Lucilina sp. 

Plate 1, figures 18, 19

Intermediate valve minute, width greatly exceeding 

length, moderately arched; beak and dorsal area smoothly 

rounded; lateral areas divided on each side by a nodose 

ridge extending from near the beak to about the midpoint of the lateral margin of valve; on posterior side of 

ridge there is a prominent row of eye spots (eight on 

each side in figured specimen); lateral area crossed by 

rounded longitudinal ridges that are better developed 

on anterior side of diagonal eye-bearing ridge. Insertion 

plates short, pectinated, each with a single slit at side; 

insertion plates separated by a shallow denticulated 

sinus.

Measurements of the figured specimen (MCZ 28020): 

length 0.9 mm, width 3.0 mm, convexity 0.6 mm.

Represented by two intermediate valves, both obtained 

from the same small sample. The specimens may be 

immature. They seem similar in general features to L. 

picta (Reeve), a Recent species from the Torres Straits, 

but I have not seen specimens.

Occurrence: Cuttings from a drill hole on Funafuti 

Atoll at depth of 70 feet; age, Recent.

Family ACANTHOCHITONIDAE 

Genus ACANTHOCHITONA Gray

Cray, 1821, Nat. Arrangement Mollusca, London Med. Repository, v. 15, p. 234.

Type (by monotypy): Chiton fascicularis Linnaeus. 

Recent, Mediterranean.

Acanthochitona sp. 

Plate 1, figures 20, 21

Intermediate valve thin, highly arched; exposed part 

of valve semicircular in outline, lateral areas densely 

pustulose, the pustules in indistinct radial lines; dorsal 

area narrowly triangular with traces of longitudinal

grooves; beak inconspicuous; insertion plates wide, each 

with a single slit near posterior edge.

Measurements of the figured specimen (E-l, Eniwetok, 

770-780 ft), USNM 648220: length 1.1 mm, width 2.5 

mm, convexity 0.8 mm.

Occurrence: Two slightly worn specimens from drill 

hole E-l on Eniwetok Atoll, depth 560-780 feet; a similar intermediate valve was recovered from drill hole 2B 

on Bikini at depth of 873-884 feet; the figured specimen 

and the Bikini specimen are from beds referred to late 

Miocene (Tertiary g). The younger Eniwetok specimen 

(560-570 ft) may be Pliocene.

Genus CRYPTOPLAX Blainville

Blainville, 1818, Dictionnaire Sci. Nat., v. 12, p. 124.

Type (by subsequent designation, Herrmannsen 1852, 

Indicis Generum Malacozoorum Primordia, supp., Cassellis, p. 39): Chiton larvae-formis Burrow, Recent, 

southwest Pacific islands.

A group of vermiform chitons with well-developed 

fleshy girdles; adapted to living in burrows and other 

holes in coral or other rock. J. P. E. Morrison collected 

numerous specimens beneath pieces of coral rubble on 

the barrier reef off Noumea in New Caledonia. He noted 

that the chitons were completely light fugitive (J. P. E. 

Morrison, oral commun., 1961). Insertion plates are extended forward; head valve with three slits; others unslit. 

Though specialized, species in the same advanced state 

have been described from the Tertiary of Australia and 

Indonesia, and the occurrence of representatives in the 

Miocene of the Marshall Islands and Fiji is not unexpected.

Cryptoplax cf. C. menkrawitensis Beets 

Plate 1, figure 22

Three incomplete intermediate valves and a tail valve 

from the Miocene (Tertiary /) Suva Formation of station 

160, Viti Levu, Fiji, bear the pustulose sculpture of C. 

menkrawitensis Beets (1941, p. 8-9, pi. 1, 1-3; 1942, p. 

242, pi. 26, 4-6) from the upper Miocene of East Borneo.

Measurements of the figured Fijian specimen, an intermediate valve, USNM 648221: length (incomplete) 1.7 

mm.

The tail valve from Fiji is proportionately longer and 

more highly arched longitudinally than that of Cryptoplax sp. A from Bikini (below) ; in the Fijian specimen 

the continuous insertion plate is extended slightly forward.

Cryptoplax sp. A 

Plate 1, figures 23-27

Head valve small, slightly longer than wide, central 

areas more than a semicircle; apex small; insertion plate
PALEONTOLOGY 25

broad, bearing three grooves that end in shallow slits or 

notches; surface covered by close-set pustules arranged 

in rows paralleling lateral margins; shallow groove 

parallels anterior and lateral margins.

Measurements of the figured specimen (pi. 1, figs. 23, 

24; E-l, Eniwetok, 750-760 ft), USNM 648222: length 

1.4 mm. width 1.2 mm.

Intermediate valves known only from one specimen 

that is unbroken but shows no trace of surface sculpture. 

Measurements (pi. 1, fig. 25; 2B, Bikini, 1,891-1,902 ft), 

USNM 648223: length 2.1 mm, width 1.2 mm.

Tail valve small, slightly longer than wide, mucro 

rounded, central area wide, bordered on each side by 

three rows of heavy pustules; insertion plate thick, extending posteriorly beyond the mucro. Measurements of 

the figured specimen (pi. 1, figs. 26, 27; 2B, Bikini, 1,870- 

1,881 ft), USNM 648224: length 1.1 mm, width 0.9 mm, 

convexity 0.4 mm.

The sculpture of the Bikini tail valve is similar to that 

of the Recent ('. striatus Lamarck, but in the Recent 

species the central area is narrower, and the insertion 

plate is directed forward. The Marshall Island specimens probably represent an undescribed species.

Occurrence: Head valve from drill hole E-l, Eniwetok 

Atoll, depth 750-760 feet; late Miocene (Tertiary g). 

Intermediate and tail valves from drill hole 2B, Bikini 

Atoll, at depths of 1,891 Vj-1,902, 1,870 y2 , and 1,881 

feet respectively; in beds referred to early Miocene 

(Tertiary e (.

Cryptoplax sp. B 

Plate 1, figures 28-30

Two valves of a larger species of Cryptoplax were recovered from cuttings in drill hole F-l, Eniwetok Atoll: 

a tail valve from a depth of 720-730 feet and an intermediate valve from a depth of 800-810 feet, both occurrences in beds referred to Tertiary g. Save for the median 

ridge, all traces of sculpture have been eroded from the 

valves. A specific determination is not possible, but 

both valves probably represent the same species. The 

general shape and proportions of the intermediate valve 

(USNM 648225; length 7.3 mm, width 3.0 mm, convexity 

1.3 mm) are similar to ('. nicnkrawitensis Beets from the 

upper Miocene of Borneo.

Measurements of the tail valve, USNM 648226: length 

o.5 mm. width 3.1 mm, convexity 1.6 mm.

The tail valve of ('. sp. B differs from C'. sp. A in having the insertion plate projecting forward. A small and 

badly worn tail valve from drill hole E-l at a depth of 

890-900 feet (Tertiary e) may represent C. sp. B; a small 

incomplete head valve from this same horizon is proportionately wider than C. sp. A and may represent C. 

sp. B.

Cryptoplax sp.

Four badly worn intermediate valves and one tail 

valve occurring with C, cf. menkrauntensis in the Suva 

Formation at station 160 (early Miocene, Tertiary /) on 

Viti Levu may represent a distinct species. All the valves 

except one are much longer than wide, and all are marked 

by strong longitudinal ribs rather than lines of pustules.

GASTROPODS

Family HALIOTIDAE 

Genus HALIOTIS Linnaeus

Linnaeus, 1758, Systema naturae, 10th ed., p. 779.

Type (by subsequent designation, Montfort, 1810, 

Conchyliologie systematique, v. 2, p. 119): Haliotis 

asinina Linnaeus. Recent, Indo-Pacific seas.

Haliotis is widely distributed in the warm and temperate seas of the world today. Species are particularly 

numerous in the Australian area but are not uncommon 

in Japan and others areas in the western Pacific and 

along the west coast of North America. Some species 

also occur on reefs encircling the islands of the open 

Pacific.

Cretaceous species have been reported from California 

lAnderson, 1958, p. 146) and Puerto Rico (N. F. Sohl, 

oral commun., 1964). Miocene forms have been described 

from Australia, Japan, Fiji(?), and the west coast of 

North America and Europe. Most species cling to rocks in 

shallow waters; fossil occurrences are rare. A total of 

nine specimens are found in the present collections six 

from Guam, two from Fiji, and one from Tinian. All, 

unfortunately, are preserved as internal molds but appear 

to be identical with, or closely related to, species known 

to inhabit reefs in these same areas today. All, with the 

possible exception of the Fijian occurrences, appear to 

be post-Miocene in age.

Subgenus PADOLLUS Montfort

Montfort, 1810, Conchyliologie systematique, v. 2, p. 115.

Type (by original designation): Padollus rubicundus 

Montfort, Recent, Indo-Pacific seas.

Haliotis (Padollus) ovina Gmelin 

Plate 2, figures 1, 2

Haliotis oinna Gmelin, 1791, Systema naturae 13, p. 3681. 

Pilsbry, 1890, Manual Conchology, v. 12, p. 124, pi. 19, figs.

7, 8.

Ovinotis ovina (Gmelin), Cotton, 1943, Royal Soc. South Australia Trans., v. 67, no. 2, p. 179.

Cotton, 1952, Royal Soc. South Australia. Malacological Sect., 

no. 1, fig. 20.
26 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

A medium-sized, elongate-oval, moderately convex 

species marked by strong radial folds that are clearly 

reflected on internal molds of the shell. The folds extend 

more than half way across the last whorl, ending in 

prominent knobs. A flattened area separates the knobs 

from a series of elevated perforations that rise from a 

low keel; below the line of perforations a concave strip 

extends to a sharp peripheral keel that is marked by 

spiral threads; columellar plate wide and flat.

Measurements of the figured specimen (Guam, USGS 

20489), USNM 648227: length 58.2 mm, width 37.5 mm, 

height 18 mm.

Represented in the collections by four internal molds, 

two of which are immature.

Occurrence: Guam, USGS 20489, 20687, 20619, 20602. 

Age, Mariana Limestone in Reef facies, Detrital facies, 

and Agana argillaceous member; Pliocene and Pleistocene.

Recent shells have been reported from Australia and 

many islands in the western Pacific (Philippines, 

Ryukyu, Fiji, Ellice, Marshalls, Samoa, and others).

Haliotis (Padollus) cf. H. clathrata Reeve 

Plate 2, figures 3-5

Three internal molds, two from Guam and one from 

Tinian, may represent this Recent species described from 

the Philippines (Reeve, 1846a, p. 57; 1846b, pi. 17, fig. 

711 and also known from the Marshall Islands. The 

following notes are based on the fossils.

A small elongate-oval species with body whorl flattened and spire low. The surface of the body whorl is 

marked by prominent radial folds that are crossed by 

numerous waved spiral ribs; the folds terminate at a 

low-angled carina bearing the molds of large elevated 

perforations. Below the perforated carina there are 

strong spiral ribs; the peripheral carina is moderately 

rounded. The columnar plate is wide and flat.

Measurements of the figured specimen from Guam 

(USGS 20994), USNM 648228: length 24.8 mm, width 

22.2 mm, height 6.6 mm; figured specimen from Tinian 

(USNM 648229): length 15.9 mm, width 8.9 mm, height 

about 5 mm.

Localities: Guam, USGS 20994 and 20639 (immature 

specimen); Tinian, USGS 21611. Collected by Josiah 

Bridge.

Horizon: Guam occurrences from detrital facies of 

Mariami Limestone; age, Pliocene and Pleistocene 

(figured specimen) and Alifan Limestone, (Miocene, 

Tertiary g or h) ; Tinian specimen from limestone terrace at altitude of 120 feet, probably equivalent to 

Mariana Limestone of Guam.

Haliotis s. 1. 

Haliotis tuvuthaensis Ladd

Haliotis tuvuthaensis Ladd, 1945, B. P. Bishop Mus. Bull. 181, 

p. 351, pi. 50, figs. E, F.

The single internal mold on which this species is based 

does not show the radial folds that characterize H. ovina 

Gmelin but there are two rows of secondary nodes inside 

the keel that bears the nodular openings.

Occurrence: Island of Tuvutha in Lau (eastern Fiji) at 

an altitude of 650 feet. Collected by E. C. Andrews. 

Probably Futuna Limestone, early Miocene (Tertiary 

/>.

Haliotis sp.

Haliotis sp. Ladd, 1945, B. P. Bishop Mus. Bull. 181, p. 351.

A single incomplete internal mold resembling H. ovina 

Gmelin but with a higher spire and a more convex body 

whorl.

Occurrence: Island of Ngillangilla off coast of Vanua 

Mbalavu in Lau (eastern Fiji) at an altitude of 10 feet. 

Collected by E. C. Andrews. Possibly Futuna Limestone, 

early Miocene (Tertiary /).

Family SCISSURELLIDAE 

Genus SCISSURELLA d'Orbigny

d'Orbigny, 1824, Soc. Hist. Nat. Paris Mem., 1, p. 341.

Subgenus SCISSURELLA s.s.

Type (by subsequent designation, Gray, 1847, Zool. 

Soc. London Proc., pt. 15, p. 146): Scissurella laevigata 

d'Orbigny. Recent, Mediterranean Sea.

Scissurella (Scissurella) declinans Watson 

Plate 2, figure 6

Scissurella declinans Watson, 1886, Challenger Kept., Gastropoda,

p. 115, pi. 8, fig. 2. 

Pilsbry, 1890. Manual Coneholouy v. 12, p. 57, pi. 65, figs. 6-8.

Minute, depressed, thin, transparent; upper half of 

whorl with a strong carina with elevated edges; above 

the carina the surface of the whorl is flattened, below the 

carina it is at first concave, then broadly convex; last 

whorl very large; carina the site of a narrow deep slit 

extending backward from the aperture; umbilicus wide 

and deep, funnel shaped, marked by fine lines parallel to 

inner lip and bordered by a distinct carina; aperture 

ovate, oblique. Sculpture of last whorl consisting of fine 

spiral striae and lines of growth; on earlier whorls, 

stronger oblique axial riblets are present both above and 

below the carina.

Measurement of the figured specimen, USNM 648230: 

diameter 1.3 mm, height 0.7 mm.

Occurrence: In drill hole E-l on Eniwetok Atoll at 

depth of 30-45 feet, a single well-preserved Recent shell;
PALEONTOLOGY 27

in hole 213 on Bikini Atoll at depth of 884-894 feet 

(figured specimen); late Miocene (Tertiary g). Recent 

examples were recovered from drift on Rongelap and 

Rongerik in the Marshall* and on Ifaluk Atoll; in the 

Carolines, D. P. Abbott collected the species alive from 

algae growing on dead coral of patch reefs on lagoon 

shelf 75 feet from shore in very shallow water (0-4 ft). 

The type material was collected by the Challenger near 

Cape York Peninsula, northeast Australia, in coral sand 

at a depth of 155 fathoms.

Scissurella (Scissurella) coronata Watson

Plate 2, figures 7. 8

Scissurella coronata Watson, 1886, Challenger Rept., Gastropoda,

p. 114, pi. 8, fig. 4.

Pilsbry, 1890, Manual Conchology. v. 12, p. 56, pi. 65. figs. 

11-13.

Very small; spire flattened, thin; upper part of whorl 

flat, bordered by a strong carina with erect margins; 

below carina the whorl is slightly concave, then broadly 

convex; umbilicus moderately wide and deep; aperture 

large, ovate, oblique. Sculpture consisting of strong, 

curved axial ribs that are prominently developed on the 

flat area above the carina and on the convex area below, 

dying out near the umbilicus; fine spiral threads are 

present above and below carina.

Measurements of the figured specimen (E-l, Eniwetok, 

30-35 ft), USNM 648329: diameter 1.9 mm, height 1.3 

mm.

On the three Tongan fossil specimens the spiral sculpture is obscurely preserved, but they seem clearly to 

represent this strongly ribbed Recent species.

Occurrence: Drill hole E-l, Eniwetok, 30-35 feet; age, 

Recent. Station 3, sea cliff at Hounia, Tongatabu, Tonga 

(B. P. Bishop Mus., geology No. 1338); from material 

filling specimens of Turbo argyrostomus. Collected by 

,T. M. Ostergaard at an altitude of 35 feet; age, probably 

Pleistocene. Type material collected in the harbor of 

Tahiti, Society Islands, near the reefs at a depth of 20 

fathoms.

Subgenus ANATOMA Woodward 

Woodward, 1859, Zool. Soc. London Proc., p. 204.

Type (by original designation): Scissurella crispata 

Fleming. Recent, North Sea.

Scissurella (Anatoma) equatoria Hedley 

Plate 2, figures 9, 10

Scissurella equutoria Hedley, 1899, Australian Mus. Mem. 3, pt. 

9, p. 551.

The following description is based on the fossil material :

Minute; spire moderately high, thin; periphery of 

whorls located near midpoint and bears a strong carina 

leading to a slit whose edges are slightly reflected outward; above, carina whorls are gently convex; immediately below carina is a concave zone below which the 

remainder of the base is tumid; aperture subquadrate, 

oblique; inner lip slightly reflected below; umbilicus narrow, partly shielded by inner lip. Sculpture consisting of 

minute close-set curved lines of growth that are more 

distinct above the carina than below it; spiral threads 

obscure.

Measurements of the figured specimen, MCZ 28021: 

diameter 0.8 mm, height 0.6 mm.

Occurrence: Two specimens in cuttings from a drill hole 

on Funafuti Atoll, at a depth of 65 feet; nine specimens 

from drill hole E-l, Eniwetok Atoll, at depths of 20-40 

feet; occurrences at both places probably Recent. The 

single type described by Hedley was dredged from a 

depth of 200 fathoms off Funafuti.

Hedley recognized that S. equatoria is closely related 

to /S. aedonia Watson, a Recent species obtained by the 

Challenger near Tristan da Cunha in the South Atlantic 

at depths of 100-150 fathoms. Hedley noted that S. 

equatoria wras the largest species of the genus (major 

diameter 3.0 mm) and that it also differed from S. aedonia 

in having a contracted zone beneath the carina and a 

lesser development of spiral sculpture. Some of the fossil 

specimens appear to be adults; they are much smaller 

than the type, but the fossils show the other diagnostic 

features mentioned by Hedley.

Family FISSURELLIDAE 

Genus EMARGINULA Lamarck

Lamarck, 1801, Systeme des Animaux pan* Vertebres, p. 69.

Subgenus EMARGINULA s.s.

Type (by monotypy): Emarginula conica Lamarck 

(=Patella fissura Linnaeus). Recent, European seas.

Emarginula (Emarginula) bicancellata Montrouzier 

Plate 2, figures 11, 12

Emarginula bicancellata Montrouzier, 1860, Jour, conchyliologie,

v. 8, p. 112, pi. 2, fig. 9. 

Pilsbry, 1890, Manual Conchology, v. 12, p. 256, pi. 64, fig. 42.

Small, solid, oval, highly convex; apex narrow, fairly 

sharp, back slope below apex flattened. Slit narrow, open 

for about one-third its length; closed section crossed at 

fairly regular intervals by erect lamellae. Sculpture consisting of about 30 radial ribs, alternately larger and 

smaller, that are crossed by less prominent concentric 

ribs to give the shell a latticed appearance.
28 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Measurements of the figured specimen (British Mus. 

1964, 231: length (incomplete) 3.0 mm, width 2.3 mm, 

height 2.5 mm.

Occurrence: A single specimen from the first boring on 

Funafuti Atoll in the Ellice Islands, depth 65-74 feet; 

two other specimens from drill holes F-l and E-l, Eniwetok Atoll, at depths of 55-100 feet; all occurrences 

probably Recent. Originally described from New Caledonia; also collected in Samoa where it was found under 

coral blocks and in pieces of dead coral at intertidal 

levels.

Emarginula (Emarginula) cf. E. peasei (Thiele) 

Plate 2, figures 13, 14

Small, elongate-oval, depressed; side margins slightly 

arched so that shell rests on extremities; apex inconspicuous, located about one-third of the length from the 

posterior end; slit narrow, less than one-fourth of total 

length of shell. Sculpture consisting of about 21 strong 

radial ribs which on the posterior half of the shell alternate with secondary ribs, the total number of ribs being 

about 31; ribs crossed at fairly regular intervals by concentric lirae that form deep pits between ribs.

Measurements of the figured specimen, USNM 648231: 

length 3.3 mm, width 2.0 mm, convexity 0.6 mm.

The fossil appears to be most closely related to E. 

peasei, a Recent species originally described from the 

Pacific islands (Thiele, 1915, p. 87). The single fossil 

shell is less than half the size of that of the living species 

and may be immature. Immaturity may explain the 

absence on the fossil of the finest sculpture exhibited on 

the primary ribs and in the pits of the living species. 

The secondary ribs of the fossil have not been noted 

on the living shell.

Occurrence: In drill hole E-l on Eniwetok Atoll at a 

depth of 90-110 feet; age, Recent.

Emarginula (Emarginula) aff. E. clypeus A. Adams 

Plate 2, figures 15, 16

Small, broadly oval, narrowed anteriorly, depressed; 

apex posterior, slightly more than two-thirds of the total 

length of the shell; anterior slope gently convex, posterior 

slope flat; shell margin crenulated, moderately arched 

below; slit narrow, open for one-fifth of its length. 

Sculpture consisting of about 33 radial ribs, of which 

about 6 3 on each side are larger than the others; shell 

surface latticed by regularly spaced concentric lirae.

Measurements of the figured specimen (F-l, Eniwetok, 

60-70 ft), USNM 648232; length 4.3 mm, width 2.9 mm, 

convexity 1.1 mm.

The Eniwetok fossils are similar to E. clypeus A. 

Adams (1851, p. 83), a Recent species from the Philippines. Pilsbry (1890, p. 265, pi. 28, fig. 7) noted that 

the species "has some prominent ribs." The fossils are 

smaller than the examples figured by Thiele (1915, p. 

97, pi. 11, figs. 24, 25). I have not seen specimens of 

E. clypeus. The fossils probably represent a distinct 

species; they may be immature.

Occurrence: Nine specimens from drill holes on Eniwetok Atoll clown to depths of 60-70 feet; age, Recent.

Subgenus SUBZEIDORA Iredale

Iredale, 1924, Linnean Soc. New South Wales Proc., v. 49, p. 217.

Type (by original designation): Emarginula connectens Thiele. Recent, Kermadec Islands.

Emarginula (Subzeidora) souverbiana Pilsbry

Plate 2, figures 17, 18

Emarginula maculata Souverbie, 1872, Jour, conchyliologie, v.

20, p. 55, pi. 1, fig. 6. 

Emarginula souberbiana Pilsbry, 1890, Manual Conchology, v.

12, p. 262, pi. 64, fig. 28.

Small, thin, moderately convex, elongate-oval in outline, slightly narrowed in front; sides arched so that shell 

rests on extremities; apex posterior, incurved; anterior 

slope gently convex, posterior slope flat; slit narrow, 

exceeding one-third total length of shell; margin of 

shell finely crenulated; nacreous within. Sculpture consisting of 24 primary radial ribs, alternating with an 

equal number of secondary ribs; surface cancellated by 

close-set concentric lirae.

Measurements of the figured specimen (E-l, Eniwetok, 10-20 ft), USNM 648233: length 3.0 mm, width 

1.9 mm, convexity 0.9 mm.

The two fossil specimens referred to E. souverbiana 

are small and may be immature; they are proportionately flatter than the typical Recent shells.

Occurrence: Drill hole E-l, Eniwetok Atoll at a depth 

of 10-20 and 30-35 feet; age, Recent. The Recent types 

were collected in New Caledonia.

Emarginula (Subzeidora) sp. A 

Plate 2, figures 19, 20

Minute, broadly oval, highly arched forward from 

posterior; incurved apex, profile beneath apex gently 

convex; split open for about one-third of total length. 

Sculpture consisting of about 20 strong radial ribs beaded 

by concentric lirae. Internally the platform beneath 

the apex is inconspicuous.

Measurements of the figured specimen, USNM 648234: 

length 2.1 mm, width 0.9 mm, convexity 0.6 mm.

The single fossil appears close to, and may be identical with, the Recent type species E. connectens Thiele 

from the Kermadecs, but it is even smaller than that 

species and may be immature. Adequate figures of the
PALEONTOLOGY 29

type species are not available, and I have not seen specimens. E. sp. A also appears to be closely related to 

E. sublathrata Pilsbry from Hawaii, but the fossil is 

narrower and more inflated posteriorly than is the Recent 

shell.

Occurrence: Drill hole 2B, Bikini Atoll at a depth of 

1,807-1,819 feet; early Miocene (Tertiary e).

Emarginula (Subzeidora) sp. B

Plate 2. figures 21, 22

Minute, highly arched, laterally compressed; outline 

from below sub rectangular; apex posterior, strongly incurved, anterior slope gently convex; posterior slope 

flattened below apex; slit long and narrow, open for more 

than one-third of total length. Sculpture consisting of 

about 20 strong primary radial ribs alternating with an 

equal number of finer secondary ribs; close-set concentric lirae over entire shell give a cancellated appearance ; the more prominent lirae forming beads where they 

cross primary ribs. Anterior part of shell, below a line 

extending from upper end of slit to margin on each side 

at points below the apex, colored dark green; a small 

spot of green crosses selenizone a short distance above 

slit; remainder of shell white and translucent.

Measurements of the figured specimen, USNM 648235: 

length 2.2 mm, width 1.4 mm, convexity 1.0 mm.

The single fossil specimen appears to be much more 

compressed laterally than other described species. The 

fossil may represent an unnamed species, but it could 

be an unusual or immature specimen. A name is withheld pending the recovery of additional material.

Occurrence: Drill hole F-l on Eniwetok Atoll at a 

depth of 20-45 feet; age, Recent.

Genus HEMITOMA Swainson

Swainsoii, 1840, Treatise on malacology, p. 356.

Subgenus HEMITOMA s.s.

Type (by mouotypy): Patella tricostata Sowerby 

(=Patella octoradiata Gmelin). Recent, West Indies

Hemitoma (Hemitoma) sp. 

Plate 2, figure 23

Large, low, ovate in outline; posterior slope flat; 

selenizone inconspicuous; slit a shallow marginal indentation. Sculpture consisting of about a dozen rather 

regularly spaced broad but sharp-crested ribs that cause 

crenulation on the margin of the shell; two or more 

secondary ribs lie between each two primary ribs; all ribs 

made slightly scaly by irregular concentric lirae.

Measurements of the figured specimen, USNM 648449: 

length 28.8 mm, width 22.6 mm.

The single Fijian fossil, seated upon a worn coral 

pebble, is incomplete, the apical area being worn away. 

It is larger, less convex, and less regularly ribbed than 

H. ossea (Gould), a Recent species knowai only from Fiji.

Occurrence: In the Ndalithoni Limestone; age, probably Pliocene (Tertiary h) ; Vanua Mbalavu, Fiji (sta.

HOB).

Subgenus MONTFORTIA Recluz

Recluz, 1843, I. Travaux inedits catalogue descriptif de plusicurs 

nouvelles especes de coquilles des mers de la France, p. 

259.

Type, (by subsequent designation, Iredale, 1915, New 

Zealand Inst. Trans. and Proc., v. 47, p. 435): Emarginula australis Quoy and Gaimard. Recent, Australia.

Hemitoma (Montfortia) bikiniensis Ladd, n. sp. 

Plate 2, figures 24, 25

Small, moderately arched, broadly ovate in outline; 

anterior slope convex, posterior slope concave immediately below apex; anterior slit broad and short; internal 

groove distinct. Sculpture consisting of about a dozen 

large rounded radial ribs, between each two of which 

lie one to three small rounded ribs; concentric lirae form 

low nodes that are particularly prominent on the larger 

ribs; margin of shell crenulated.

Measurements of the holotype, USNM 648236: length 

4.8 mm, width 3.6 mm, convexity 2.0 mm.

H. bikiniensis is smaller than the type species H. austrahs, is less convex, and has more strongly developed 

concentric structure.

Occurrence: Holotype from drill hole 2 on Bikini Atoll 

at a depth of 105 feet; a second specimen in hole F-l 

on Eniwetok at depth of 45-55 feet; both occurrences 

probably Recent.

Hemitoma (Montfortia) sp. A

Plate 2, figures 26, 27

Small, depressed, subrectangular in outline, thin; anterior slope gently convex, posterior slope (below apex) 

flat; apex about two-thirds of length from anterior margin; slit narrow, moderate in length; internal groove 

shallow. Sculpture consisting of about 20 poorly marked 

radial ribs of which 4, extending roughly to the corners, 

are larger than the others; concentric lirae obscurely 

developed.

Measurements of the figured specimens (E-l Eniwetok, 35-40 ft I, USNM 648237: length 3.0 mm, width 

2.1 mm, convexity 1.2 mm.

The fossils may be related to H. ossea (Gould), a 

Recent species collected in Fiji. H. ossea, however, is a 

larger, heavier, and more coarsely marked shell whose 

apex is more centrally located. The type and only speci-
30 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

men of H. ossea is worn, and detailed comparisons are 

not possible.

Occurrence: Represented by a total of 10 specimens, 

all small and possibly immature, from shallow depths 

(30-60 ft! in drill holes E-l and F-l on Eniwetok 

Atoll; age, Recent.

Subgenus MONTFORTISTA Iredale

Iredale, 1929. Queensland Mus. Mem., v. 9, p. 267.

Type (by original designation): Montfortia excentrica Iredale. Recent, North Queensland.

Hemitoma (Montfortista) excentrica (Iredale)

Plate 2, figures 28, 29

Montfortia (M out f ortista) excentrica Iredale, 1929, Queensland 

Mus. Mem., v. 9, p. 267, pi. 31, figs. 14, 15.

Medium, highly elevated, slightly compressed laterally; anterior slope broadly convex, posterior slope concave. Sculpture consisting of about 20 strong ribs, the 

anterior rib being strongest; traces of secondary ribs 

between some of main ribs; strong concentric lirae give 

the 'shell a deeply pitted appearance.

Measurements of the figured specimen, USNM 648238: 

length (incompleteI 9.2 mm, width (incomplete) 6.6mm, 

height 7.7 mm.

The single fossil specimen is incomplete, but there 

appears to be little doubt that it represents H. excentrica, 

a Recent shell from the Queensland coast.

Occurrence: From coral pit (USGS 21029) on Espiritu 

Santo, New Hebrides, at altitude of 215 feet; age, Pleistocene or Recent.

Genus RIMULA Defrance

Defranee, 1827, Dictioimaire Sci. Nat., v. 45, p. 471.

Type (by subsequent designation, Gray, 1847, Zool. 

Soc. London Proc., v. 15, p. 147): Rimula blainvilli Defrance. Eocene, France.

Rimula closely resembles Emarginula but the slit is 

partly closed, leaving a hole about half way up the 

anterior slope. This feature first appeared on species 

that developed during the Lower Cretaceous. Living 

examples are widely distributed in the warmer parts 

of the Pacific and the Atlantic. The only fossil representatives of the genus in the Pacific island collections 

are from the Marshall Islands. A single specimen identified as R. exquisita was obtained from beds probably 

of Pliocene age on Bikini. Three small Recent shells 

from near the surface on Eniwetok are probably immature. A single somewhat worn shell from a depth of 

more than 2,000 feet on Eniwetok is Miocene (Tertiary 

f) and appears to represent a second species.

Rimula exquisita A. Adams 

Plate 2, figures 30, 31

Rimula exquisita A. Adams, 1851, Zool. Soc. London Proc., 19,

p. 226.

Sowerby, 1862, Thesaurus conchyliorum 3, p. 210, figs. 3, 4. 

Pilsbry, 1890, Manual Conchology, v. 12, p. 270, pi. 64, figs.

3,4.

Medium in size, oval in outline; anterior slope broadly 

convex, posterior slope flattened; perforation long, 

slightly narrowed anteriorly; sculpture consisting of 

about 34 ribs that tend to alternate in size and are beaded 

by regularly spaced concentric lirae. Measurements of 

the figured specimen, USNM 648239: length 4.4 mm, 

width 3.0 mm, convexity 1.6 mm.

Occurrence: The single immature fossil was obtained 

in drill hole 2A on Bikini Atoll at a depth of 447-453 

feet; age, post-Miocene, probably Pliocene. Recent shells 

have been collected from the Philippines, Japan, and the 

Mariana Islands.

Rimula sp.

Plate 2, figures 32, 33

Small, oval in outline; margin crenulated, moderately 

convex, translucent; apex strongly recurved; perforation 

short, subrectangular. Sculpture consisting of about 20 

strong radiating ribs that alternate with smaller secondary ribs; primary ribs conspicuously beaded by regularly spaced concentric lirae. Two of the three specimens available show traces of about eight broad radial 

bands of greenish brown. Measurements of the figured 

specimen, USNM 648240: length 1.9 mm, width 1.4 mm, 

convexity 0.9 mm.

Occurrence: Drill hole E-l on Eniwetok Atoll at a 

depth of 10-20 feet; age, Recent. A single worn shell 

from hole F-l, Eniwetok, may represent this species; it 

was obtained from cuttings at a depth of 2,010-2,020 

feet in Miocene beds (Tertiary e) but may have been 

derived from a higher level.

Genus SCUTUS Montfort

Montfort, 1810, Conchyliologie systematique, v. 2, p. 58-59.

Type (by original designation): Scutus antipodes 

Montfort. Recent, southeast Australia.

Subgenus NANNOSCUTUM Iredale

Iredale, 1937, Australian Zoology, v. 8, pt. 4, p. 244.

Type (by original designation): Nannoscutum forsythi 

Iredale. Recent, Lord Howe Island, Australia.

The shell of the type species of Nannoscutum is 

strongly lined concentrically, but even in this definitive 

feature it does not differ markedly from some of the 

shells ordinarily referred to Scutus s.s. Iredale, however,
PALEONTOLOGY 31

has pointed out that the animal is unlike that of any 

previously described Scutus. Only two specimens of 

scutid shells are found in the collections of island fossils. 

Both are from drill hole on Eniwetak Atoll in beds referred to Tertiary g. Both are small, as is the type of 

Nannoscutum, both show strong concentric sculpture, and 

each has a thickened margin that indicates adulthood. 

They differ in detailed sculpture, however, and may 

represent distinct species. Neither shell is complete, and 

this fact coupled with their rarity makes it unwise to 

attach specific names. They are described and figured 

as species A and B.

The scutids are an Indo-Pacific group. In life the 

animals appear sluglike, because the flattened shells are 

partly or completely covered by the mantle. They are 

know to inhabit shallow water and to be light sensitive. 

Tredale found the type species of Nannoscutum living 

under stones.

Scutus (Nannoscutum) sp. A 

Plate 2, figures 34, 35

Shell small, depressed, stout, marked posteriorly 

(anterior end missing) by six strong concentric ridges 

whose interior margins are wavy; outer ribs widely 

spaced with fine secondary ribs in the intervening depressions.

Measurements of the figured specimen, USGS 648241: 

width 7.1 mm, convexity 2.8 mm.

Occurrence: Drill hole F-l, Eniwetok Atoll at depth of 

720-730 feet; late Miocene (Tertiary g.)

Scutus (Nannoscutum) sp. B

Plate 2, figures 36, 37

Shell small, thin, outer parts marked by wavy concentric ridges; area near apex comparatively smooth but 

bearing fine concentric lines that are bent backward 

along the median line of the shell.

Measurements of the figured specimen, USNM 648242: 

length (incomplete) 5.3 mm, convexity 1.5 mm.

The single incomplete shell resembles the genotype 

N. forsythi but appears to have been more strongly indented anteriorly. A comparison with actual specimens 

of the type might reveal other distinctions.

Occurrence: Drill hole K-1B, Eniwetok Atoll at a 

depth of 768-779 feet; late Miocene (Tertiary g).

Genus DIODORA Gray

Gray. 1821, Xat. Arrangement of Mollusca. London Med. Repository, v. 15, p. 233.

Type (by monotypy): Patella apertura Montagu (= 

Patella graeca Linnaeus). Recent, Mediterranean Sea.

Subgenus ELEGIDION Iredale

Iredale, 1924, Linnean Soc. New South Wales Proc., v. 49, p. 220, 

pi. 35, figs. 5, 6.

Type (by original designation): Elegidion audax Iredale. Recent, Australia.

Elegidion includes species in which the perforation lies 

wrholly on the anterior slope.

Diodora (Elegidion) marshallensis Ladd, n. sp. 

Plate 3, figures 1, 2

Small, ovate, conical; slopes nearly straight; apex 

prominent, perforation broadly oval or elliptical, located 

immediately anterior to apex. Sculpture consisting of 

about 18 sharply elevated ribs that increase in size from 

apex to shell margin where they form hollow crenulations 

on the inner surface of the shell; a single secondary rib 

is intercalated between each 2 primary ribs, but the 

secondaries arc small and cause only minor crenulations 

on the shell margin; both sets of ribs crossed by concentric lirae that become progressively larger near the 

shell margin where they form prominent beads on the 

primary ribs. The type specimens retain traces of eight 

dark green rays, the color being limited in each specimen to a single primary rib.

Measurements of the holotype (pi. 3, figs. 1, 2; E-l, 

Eniwetok, 700-710 ft), USNM 648243: length 3.4 mm, 

breadth (incomplete) 2.4 mm, height 1.5 mm.

Shells referred to this species can be easily differentiated from those of D. aff. D. granifera (Pease) (see 

below I, which occur in post-Tertiary beds in Eniwetok 

drill holes. D. marshallensis is heavier, has a much 

sharper sculpture, and a greater contrast in size between 

the two sets of ribs. The perforation of D. marshallensis 

is oval to elliptical rather than elongate and is closer to 

the apex than in the younger species; likewise, in D. 

marshallensis each of the green rays is limited to a single 

primary rib.

Occurrence: The types and a half dozen other specimens from deep drill holes on Eniwetok in cuttings from 

depths of 700-852 feet in beds assigned to late Miocene 

(Tertiary g ) ; two apical fragments from lower levels 

(873-915 ft) are from section referred to Tertiary / and 

may have been derived from younger beds. On Bikini a 

single apical fragment was recovered in hole 2B from the 

789-800 feet interval (Tertiary g}. Identifiable fragments also obtained from the marls at the base of the 

Palau Limestone in the Goikul area, Babelthuap, Palau 

(USGS 21301) ; late Miocene (Tertiary g).

Diodora (Elegidion) aff. D. granifera (Pease) 

Plate 3, figures 3, 4

Small, oval in outline, slightly narrower in front, conical; posterior slope slightly concave near apex, other
32 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

slopes nearly straight; apex prominent, projecting 

posteriorly; perforation elongate, located on the anterior 

slope. Sculpture consisting of 30 or more radial ribs with 

a tendency to alternate in strength; ribs beaded by 

weaker concentric lirae. Two of the five fossil specimens 

show traces of about 10 green radial bands visible inside 

and outside the shell.

Measurements of the figured specimen, USNM 648244: 

length I incomplete I 3.0 mm, width 2.4 mm, height 1.4 

mm.

The Eniwetok fossils are identical with several Recent 

shells collected in surface float on the atoll and appear to 

be closely related to the variable D. granifera known 

from many localities in Hawaii. (Pease, 1861, p. 244; 

Pilsbry 1890, p. 407, pi. 63, fig. 13). The Eniwetok shells 

on the average are smaller, and their radial ribs have a 

stronger tendency to alternate in size than do those of 

the Hawaiian shells.

Occurrence: Five specimens from four drill holes on 

Eniwetok Atoll at depths of 5-20 feet.

Diodora (Elegidion) sp. A 

Plate 3, figures 5, 6

Medium in size, ovate, highly conical; slopes gently 

convex; perforation small, broadly oval, located only 

slightly anterior to apex. Sculpture consisting of about 

40 strong radial ribs that alternate with a second set of 

much smaller ribs; ribs conspicuously beaded by concentric lirae that increase only slightly in size from apex 

to shell margin.

Measurements of the figured specimen, USNM 648245: 

length 14.8 mm, width 10.1 mm, height (incomplete* 8.6 

mm.

D. sp. A does not appear to be closely related to described fossil or Recent species. It may represent a new 

form, but neither of the two specimens available would 

:-iake a satisfactory type.

D. sp. A is much larger, proportionately higher, has 

more convex slopes, and is more conspicuously cancellate 

than D. inarshallensis Ladd, n. sp., which occurs with it. 

The concentric lirae of D. sp. A are, likewise, more uniform in size than those of D. marshallensis.

Occurrence: Two specimens from the marls at the base 

of the Palau Limestone in the Goikul area, Babelthuap, 

Palau lUSGS 21304); age, late Miocene (Tertiary g). 

An incomplete and poorly preserved specimen from the 

Palau Limestone close to the volcanic contact on Auluptagel (USGS 17715) may represent D. sp. A.

Family PATELLIDAE 

Genus PATELLA Linnaeus

Linnaeup, 1758, Systema naturae, 10th ed , p. 780.

Type (by subsequent designation) : Fleming, 1818, 

Enclopedia Britannica, supp. not seen: Patella vulgata 

Linnaeus. Recent, seas of Europe.

Subgenus SCUTELLASTRA H. and A. Adams

Scufellastra H. and A. Adams, 1854, Genera Recent Mollusca, 

v. 1, p. 466.

Type (fide Keen, 1960, Treatise on invertebrate 

paleontology, Mollusca 1, p. 1235): Patella plicata Born 

= Patella barbara Linnaeus. Recent, southwest Pacific.

Patella (Scutellastra) stellaeformis Reeve

Plate 3, figure 7

Patella stellaeformis Reeve, 1842, Conchyliologie systematique,

v. 2, pi. 136, fig. 3.

Pilsbry, 1891, Manual Conchology, v. 13, p. 98, pi. 17, figs. 

25-27; pi. 61, figs. 62-65.

An internal mold believed to represent this variable 

and widely distributed western Pacific species was obtained from a shallow drill hole, F-23C at depth of 85-88 

feet, on Engebi Island, Eniwetok; age, probably Recent. 

The mold is low, conic, irregularly oval in outline; six 

major ribs radiate from the near-central apex; margin 

crenulated. Measurements of the figured specimen 

USNM 648246: length 9.1 mm, width 6.7 mm.

The species occurs from east Africa to eastern Polynesia and is found in abundance today on the reefs of 

Eniwetok and other Marshall Island atolls.

Genus CELLANA H. Adams 

H. Adams, 1869, Zool. Soc. London Proc., p. 273.

Type (by original designation): Nacella cernica 

Adams. Recent, Mauritius.

Cellana aff. C. sagittata (Gould)

Helcionisciis aff. sagittata Ladd, 1945, B. P. Bishop Mus. Bull. 

181, p. 350, pi. 50, fig. D.

No additional material was collected, and identification remains uncertain. As previously pointed out, the 

fossil shells (14 specimens) from the Ndalithoni Limestone, probably Pliocene (Tertiary h), on Vanua Mbalavu, Fiji (stas. HOB, HOC) are slightly more elongate 

and somewhat less convex than the Recent shells (Gould 

1846, p. 148; 1852, p. 337; 1856, Atlas, figs. 449a-c) and 

may represent a distinct species. Recent shells of C. 

sagittata have apparently not been found outside Fiji.

Cellana sp. A 

Plate 3, figure 8

Medium in size, thick, oval, a little narrowed anteriorly, depressed conical; apex slightly anterior. Sculpture consisting of about 22 strong rounded radiating ribs, 

each of which, near the margin of the shell, bears 3 or 4
PALEONTOLOGY 33

low secondary riblets; concentric lines of growth are 

obscure on the worn shell but more prominent near the 

margins than elsewhere.

Measurements of the figured specimen, USNM 648247: 

length 28.2 mm, width 24.3 mm, height (apex slightly 

broken) 8.6 mm.

The marginal secondary riblets seem to differentiate 

the fossil from described species, but the single specimen 

is worn and broken.

Occurrence: In the Tanapag Limestone of Saipan 

(USGS 17891) ; age, probably Recent.

Cellana? sp.

//r/r/oHjVi/x? sp. Ladd, 1934, B. P. Bishop Mus. Bull. 119, p. 200, 

pi. 34. figs. 13, 14.

Occurrence: A single specimen from the marls of the 

Suva Formation, Yiti Levu, Fiji (sta. 305) ; age, Miocene 

(Tertiary /). No additional material collected; identification remains questionable.

Family TROCHIDAE

Trocliids are well represented on the island reefs today 

and apparently they were equally abundant during all 

of late Tertiary and Quaternary time. A total of 28 fossil ^pecies have been recognized. These have been placed 

in 12 genera and 15 subgenera. There are, in addition, 

numerous internal molds of trochids that are too poorly 

preserved even for generic determination. Many of these 

are large forms, and most of them were collected from 

elevated and recrystallized reef limestones.

Genus EUCHELUS Philippi

Philippi, 1847, Zoitschr. Malakozool., v. 4, p 20.

Subgenus EUCHELUS s.s.

Type (by subsequent designation, Herrmannsen, 1847, 

Indicis Generum Malacozoorum 1, p. 43,0: Trochus 

quadricarinatus Dillwyn. Recent, Indian Ocean.

Euchelus (Euchelus) cf. E. quadricarinatus (Dillwyn) 

Plate 3, figures 9, 10

Small, globose; whorls rounded, sutures impressed; 

deep umbilicus partly filled by a spiral fold; aperture 

subcircular, columella thin, straight with a poorly developed basal tooth. Sculpture consisting of 12 spiral ribs 

of which 4 are more prominent than the others; larger 

ribs beaded by axial lamellae; secondary ribs between 

primary ribs are inconspicuously beaded; 4 or 5 ribs 

cover the base; on the figured specimen the rib bounding the umbilicus is larger than the other basal ribs.

Measurements of the figured specimen (K-1B, Eniwetok, 663-674 ft), USNM 648253: height 3.7 mm, 

diameter 3.4 mm.

Occurrence: Eight specimens from four drill holes on 

Eniwetok Atoll at depths to 120 feet; age, Recent; a 

single specimen from a fifth hole (K-1B) at a depth of 

663-674 feet is from sediments referred to the late Miocene (Tertiary g} , but this specimen is incomplete and 

may have been derived from a higher level.

The fossil specimens appear to be closely related to, 

if not identical with, the type species that lives in the 

Indian Ocean (Pilsbry, 1889, p. 439, pi. 38, figs. 9-11). 

The fossils are immature and deeply umbilicate, as are 

young shells of the living species; the basal columellar 

tooth is only poorly developed on the fossils.

Subgenus HERPETOPOMA Pilsbry

Pilsbry, 1889, Manual Conchology, v. 11, p. 430.

Type (by original designation): Euchelus scabriusculus A. Adams and Angas. Recent, Australia.

Euchelus (Herpetopoma) instrictus (Gould) 

Plate 3, figures 11-13

Trochus (Monodonta) instrictus Gould, 1849, Boston Soc. Nat.

History Proc.. v. 3, p. 107.

Gould, 1852, U.S. Explor. Exped., Mollusca, p. 190.

Gould, 1856, U.S. Explor. Exped., atlas, fig. 225a-c.

Euchelus instrictus Gould, 1862, Otia Conchologica, p. 245.

Pilsbry, 1889, Manual Conchology, v. 11, p. 440, pi. 67, figs.

62, 63. 

Johnson, 1964, U.S. Natl. Mus. Bull. 239, p. 92.

Small, ovate-conic, stout; whorls moderately inflated, 

separated by a prominent channel; body whorl with 

10-11 sharply elevated spiral ribs, the 3 nearest the 

periphery being the most prominent; ribs beaded by 

close-set axial lamellae; base rounded; umbilicus narrow; columellar tooth large, with a deep basal notch below; outer lip strongly lirate within, its thin edge crenulated by the surface ribs.

Measurements of the figured specimen (E-l, Eniwetok, 30-40 ft) USNM 648254: height 4.1 mm, diameter 

3.8 mm.

Occurrence: Represented by 14 specimens from drill 

holes on Eniwetok at depths as much as 120 feet in 

Quaternary beds. A single shell from E-l at a depth of 

620-630 feet is in the top of the section referred to the 

Miocene (Tertiary g] but may have been derived from 

a higher horizon. Gould's type specimen, a Recent shell 

(USNM 5625), was collected in the Pacific, exact locality not stated. Living specimens have been collected 

in Fiji, and the species is common in the northern Marshall Islands.

Euchelus (Herpetopoma) instrictus suvaensis Ladd, n. subsp. 

Plate 3, figures 14-16

Small, conic, thick; whorls moderately inflated, the 

body whorl separated from penultimate by channel;
34 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

body whorl with nine strong spiral ribs that are coarsely 

beaded by axial lamellae; base convex, umbilicus closed; 

columellar tooth stout with deep basal notch below; inner 

edge of outer lip strongly lirate.

Measurements of the holotype, USNM 648255: height 

3.6 mm, diameter 3.3 mm.

The fossil resembles Recent examples of E. instrictus 

from the same area but is more coarsely sculptured and 

has a covered umbilicus.

Occurrence: Represented by a single specimen from 

the conglomerate at the base of the limestone in the type 

section of the Suva Formation, Viti Levu, Fiji (sta. 160); 

age, Miocene (Tertiary /).

Subgenus VACEUCHELUS Iredale

Iredale, 1929, Queensland Mus. Mem. 9, p. 272.

Type (by original designation): Euchelus angulatus 

Pease. Recent, Anaa, Tuamotu Archipelago.

Euchelus (Vaceuchelus) angulatus Pease 

Plate 3, figure? 17-19

Euchelus angulatus Pease, 1867, Am. Jour. Conchology, v. 3, 

p. 283, pi. 23a, fig. 27.

Euchelus foveolrttiiis ungulatua Pea.se, Pilsbry, 1889, Jour. Cont-hology, v. 11, p. 437, pi. 38, fig. 1.

Euchelus (Vaceuchelus) angulatus .Pease, Iredale, 1929, Queensland Mus. Mem. 9, p. 272.

Small, globular, turreted, stout, nacreous within, imperforate or narrowly umbilicate; columella without 

basal tooth; whorls convex, marked with strong spiral 

ribs crossed by well-developed axial lamellae that give 

ribs a beaded appearance and form deep pits in spaces 

between ribs. Body whorl with six to eight ribs, the 

three nearest the periphery larger than the others.

Measurements of the figured specimen (E-l, Eniwetok, 40-50 ft), USNM 648256: height 3.0 mm, diameter 

(incomplete) 2.5 mm.

The fossil occurrences are apparently the first to be 

recorded. The strongly cancellated sculpture and the 

absence of a columellar tooth easily distinguish this 

form from all related species. Comparison with several 

lots of Recent shells indicates that the fossils fall within 

the limits of variation of such shells. The strong ribs 

vary in number from five to seven and the relative 

prominence of the peripheral members of the series also 

varies somewhat. The presence or absence of a narrow 

umbilicus does not seem to be a feature of significance.

Occurrence: A single specimen from the conglomerate 

at the base of the limestone section of the Miocene 

(Tertiary /) Suva Formation, Viti Levu, Fiji. Two specimens from Quaternary beds in drill holes 2 and 2A on 

Bikini Atoll, depths of 100-285 feet; two specimens were

recovered from drill hole E-l on Eniwetok at depths of 

10-50 feet; age, Recent.

Type locality of Recent shell is the island of Anaa in 

the Tuamotus; species also collected in the Society and 

Marshall Islands and reported from Fiji, Philippines, 

and Ceylon.

Euchelus (Vaceuchelus) sp. A 

Plate 3, figures 20-22

Minute, conical, stout, narrowly perforate; aperture 

subcircular, columella straight, thin, without basal tooth; 

whorls flattened, sutures deeply impressed. Sculpture 

consisting of strong spiral ribs, 10 being present on body 

whorl; peripheral rib and the one immediately below it 

are larger than those above and than the 5 on the base; 

ribs crossed by slightly oblique axial lamellae to produce 

a pitted surface. Upper surface of whorls marked at 

fairly regular intervals by narrow reddish-brown axial 

bands.

Measurements of the figured specimen (E-l, Eniwetok, 30-40 ft), USNM 648257: height 2.8 mm, diameter 

2.6 mm.

Easily differentiated from E. cf. quadricarinatus, previously described, by the flatness of the whorls and the 

absence of the basal tooth. In general form and sculpture the fossil resembles Antillachelus (Miocene to Recent, 'West Indies), but in that group there is a wide 

umbilicus and a heavy basal tooth and the aperture is 

lirate within.

Occurrence: Two specimens at shallow depths (22- 

40 ft) from drill holes on Eniwetok Atoll; age, Recent.

Genus HYBOCHELUS Pilsbry

Pilsbry, 1889, Manual Conchology, v. 11, p. 430.

Type (by original designation): Stomatella cancellata 

Krauss. Recent, Cape of Good Hope.

Hybochelus cancellatus orientalis Pilsbry 

Plate 3, figures 23, 24

EuclicliiN (Hyborhclitx) caiicclhitiix oriental^ Pilsbry, 1904, Acad. 

Nat. Sci. Philadelphia Proc., p. 35, pi. 6, figs. 57, 57a.

Small, turbinate, depressed; body whorl large, suture 

deep; aperture ovate, oblique; umbilicus narrow, deep. 

Sculpture consisting of strong spiral ribs alternating with 

smaller secondary ribs, there being 10 primary spirals 

at the beginning of the last whorl; spirals crossed by 

oblique axial ribs to form deep, narrow pits; lowest of 

primary ribs spirals into the umbilicus. Traces of spots 

of brown on some of spiral ribs.

Measurements of the figured specimen (E-l, 50-60 

ft), USNM 648258: height (incomplete) 3.6 mm, diameter (incomplete) 4.7 mm.
PALEONTOLOGY 35

The fossil specimens are small; one is incomplete, the 

other immature, neither specimen shows the threads of 

a third order mentioned by Pilsbry, though some of the 

Recent Marshall Island specimens do show this feature.

Occurrence: Two specimens from drill holes on Eniwetok Atoll at a depth of 29-60 feet; age, probably Recent. The species is a common one on the atoll today 

and was also collected at nearby Rongelap and Rongerik 

Atolls; Pilsbry's types were collected in Japan.

Hybochelus kavoricus Ladd 

Plate 3, figures 25, 26

Euchelun (Hybochelus) kavoricus Ladd, 1945, B. P. Bishop Mus. 

Bull. 181, p. 353, pi. 50, figs. J, K.

No additional material collected. Holotype and only 

specimen from Ndalithoni Limestone; age, probably 

Pliocene (Tertiary h) ; Vanua Mbalavu, Fiji, (sta. 

HOB). As noted in the original description, H. kavoricus 

differs from H. cancellatus orientalis chiefly in having 

fewer spiral ribs.

Genus THALOTIA Gray

Gray, 1840, Synop. contents British Mus., p. 147.

Subgenus THALOTIA s.s.

Type (by subsequent designation, Gray, 1847, Zool. 

Soc. London Proc., p. 145): Trochus pictus Wood= 

^lonodonta conica Gray. Recent, Australia.

Thalotia (Thalotia) berauensis (Beets) 

Plate 3, figures 27, 28

C(inthariiins (Canlharidus) herauensis Beets, 1941, Geol.-mijnb. 

gonoot.sch. Nedorland on Koloiiien Vorli.. Gool. sor., v. 13. 

pt. 1, p. 13-14, pi. 9, figs. 338-340.

Small, broadly conical, stout, imperforate; spire flat, 

periphery of body whorl rounded; aperture ovate, lirate 

within; columella inclined with a strong nearly horizontal basal tooth. Whorls marked by spiral ribs conspicuously beaded by inclined axial lamellae; on body 

whorl the 5-6 ribs above the strong peripheral fib are 

subequal in size; the 5-6 ribs on the base below the 

periphery arc variable in size; axial wrinkles are well developed on the early whorls, 9-11 being on the penultimate whorl.

Measurements of the figured specimen, USNM 648259: 

height 5.2 mm, diameter 3.4 mm.

Occurrence: Originally described from the upper Miocene of East Borneo. Three specimens found in drill 

hole Kl-B on Eniwetok Atoll at a depth of 1,070-1,081 

feet in beds referred to lower Miocene (Tertiary /).

Thalotia (Thalotia) aff. T. elongatus (Wood) 

Plate 3, figure 29

Narrowly conical, heavy; periphery rounded, sutures 

slightly impressed, imperforate. Sculpture consisting of 

two spiral rows of heavy nodes and finer spiral ribs; base 

with close-set spiral ribs.

Measurements of the figured specimen, USNM 648260: 

height 22.2 mm, diameter 15.3 mm.

The single fossil is complete, but the shell is recrystallized and most sculptural features are obscured. It resembles the Recent T. elongatus (Wood, 1828, pi. 5, fig. 

19 ) in its unusual height of spire and its heavy nodes that 

tend to form longitudinal plications. On the fossil, the 

nodes are larger and the rows are more distinctly separated than on the Recent shells. When better material is 

obtained, the fossil may prove to be a distinct species. 

T. elongatus was described from New Caledonia (Pilsbry, 1889, i). 143, pi. 45, fig. 56), but it is also known from 

Japan. During Operation Crossroads in the Marshall 

Islands, a single dead shell was collected from the lagoon 

shore of Eniwetok Atoll.

Occurrence: In the Mariana Limestone of Guam 

lUSGS 20574) ; age, probably Pleistocene.

Subgenus Beraua Beets

Beds. 1941, Giol.-mijnb. genootsrh. Nodorland on Kolonicu 

Verh., Geol. ser., v. 13, pt. 1, p. 14.

Type (by original designation): Cantharidus erinaceus Beets. Upper Miocene, Borneo.

Thalotia (Beraua) sp. 

Plate 3, figure 30

Small, high-conical; base convex; early whorls flat 

sided with low axial plications; last two whorls with 

strong sutural nodes, all whorls and base bearing fine 

spiral ribs.

Measurements of the figured mold, USNM 648261: 

height 9.7 mm, diameter 7.5 mm.

The single specimen from Saipan is an incomplete 

external mold, but it does show the unique sutural nodes 

that characterize Beraua. It closely resembles the 

plumper form of the type species T. erinaceus, described 

by Beets from the Miocene of Borneo, but appears to 

have a more convex base. Specific identification must 

await better material.

Occurrence: Inequigranular facies of Miocene (Tertiary 

e\ Tagpochau Limestone, Saipan, Mariana Islands 

(USGS 17904).

Genus TURCICA A. Adams

A. Adams, 1854, Zool. Soc. London Proc., p. 37.

Type (by monotypy): Turcica monilifera A. Adams. 

Recent, Morton Bay, Australia.
36 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Subgenus PERRINIA H. and A. Adams 

H. and A. Adams, 1854, Genera Recent Mollusca, 1, p. 419.

Type (by subsequent designation, Pilsbry, 1889, 

Manual Conchology, v. 11, p. 419): Monodonta angulifera A. Adams. Recent, Philippine Islands.

Turcica (Perrinia) morrisoni Ladd, n. sp.

Plate 3, figure 31; plate 4, figures 1-5

Small, conic, stout, imperforate, nacreous within. 

Whorls with a prominent peripheral carina which is extended into a series of flattened triangular spines that 

are regularly spaced (about 13 on the last whorl) and 

that give the shell a stellate appearance when viewed 

from above; suture impressed. Above the peripheral 

carina are three beaded spirals, the uppermost one coarser 

than the other two; base has four beaded concentric 

spirals, the outer one the coarsest, its beads spinose. 

Aperture semi-elliptical, lirate within; columella strong, 

granulate, with a broad basal tooth; outer lip thin, its 

edge crenulated by the surface ribs.

Measurements of the holotype, a Recent shell (pi. 3, 

fig. 31; pi. 4, figs. 1, 21, USNM 648262: height 3.3 mm, 

diameter 2.8 mm.

Euchelus morrisoni is closely related to E. stellata 

described by A. Adams from the China Seas, but both 

Recent and fossil examples of E. morrisoni are much 

smaller, have a broader apical angle (roughly 65° as 

against 45° for E. stellata), and the concentric ribs on 

the base are strongly beaded whereas those of E. stellata 

are not.

Occurrence: Type lot (five specimens) collected alive 

from the undersides of coral blocks on the reef flat behind 

the seaward margin on the south side of Bokororyuru 

Island, Bikini Atoll. This area is the "zone of blocks" 

in a measured traverse (Emery, Tracey, and Ladd 1954, 

p. 170-171) ; it lies 115-225 feet from the seaward edge, 

and its surface is covered by a foot of water at low tide. 

Collected by .1. P. E. Morrison.

A few dead shells were found in drift samples from 

half a dozen localities on several islands of Bikini Atoll 

a.id of Eniwetok Atoll; dead shells were' found in abundance in a drift sample taken on Bock Island, Rongerik 

Atoll.

Only two fossil shells have been found. One of these 

shells is from a depth of 27^ feet in drill hole 2 on Bikini 

Island and is Recent in age; the other (USNM 648263, 

pi. 4, figs. 3-5) from a depth of 1,461-1,472 feet in drill 

hole 2B on Bikini Island i.s from beds referred to the 

Miocene (Tertiary /), but the single fossil picked from 

the drill cuttings is slightly worn and may have been 

derived from a younger horizon.

Genus GIBBULA Risso

Risso. 1826, Histoire naturelle des priricipales productions de 

1'Europe meridionals, v. 4, p. 134.

Subgenus GIBBULA s.s.

Type (by subsequent designation, Herrmannsen, 1848, 

Indicis Generum Malacozoorum Primordia, p. 437): 

Trochus magus Linnaeus. Recent, Mediterranean Sea.

Gibbula (Gibbula) engebiensis Ladd, n. sp. 

Plate 4, figures 6, 7

Shell small, conical, distinctly turreted with sutures 

impressed; moderately thick; aperture subcircular, 

smooth and pearly within; umbilicus narrow, bordered 

by a thick 'beaded spiral ridge; inner lip callused, expanded a little above, more extensively below where it 

covers the end of the umbilical ridge. Sculpture consisting of primary and secondary spiral ribs inconspicuously 

beaded by fine axial lines of growth; on the body whorl 

there are four primary ribs, the middle two being slightly 

larger and forming a biangular periphery; secondary 

ribs are present between all primary ribs and on the base 

which is set off from the rest of the whorl by a sharp 

angle. Traces of original color in the form of wide, regularly spaced reddish-brown bands appear on the last two 

whorls and extend across the base of the body whorl; 

inner lip white.

Measurements of the holotype, only specimen, USNM 

648264: height 2.9 mm, width 2.9 mm.

The fossil species is tentatively referred to Gibbula 

s.s. because it seems to fit better there than in any one 

of the numerous subgenera that have been recognized. 

The type of the genus, G. magus (Linnaeus), is a mediumsized shell from the Mediterranean with a wider umbilicus than that shown by the fossil and a less well developed columellar callus. The fossil is much more closely 

related to G. gradata (Gould), a species described from 

the Pacific islands (Gould, 1849, p. 91) and later from 

the West Indies (as G. pisum Philippi, Pilsbry, 1889, p. 

241, pi. 31, figs. 38-401. The Recent shell is considerably 

larger than the fossil, is more distinctly ribbed, and on 

the body whorl the uppermost of the four primary ribs 

is the largest; the Recent shell likewise has a wider umbilicus than does the fossil.

Occurrence: Drill hole Kl-B on Engebi Island, Eniwetok Atoll, at a depth of 926-936 feet in beds referred 

to early Miocene (Tertiary /).

Genus FOSSARINA A. Adams and Angas 

A. Adam,* and Angas, 1863, Zool. Soc. London Proc., p. 423.

Type (by subsequent designation, Suter, 1913, Manual 

New Zealand Mollusca, p. 139): Fossarina patula A. 

Adams and Angas. Recent, Australia.
PALEONTOLOGY 37

Subgenus MINOPA Iredale

Iredale, 1924, Linnean Soc. New South Wales Proc., v. 49, p. 226.

Type (by original designation): Fossarina legrandi 

Petterd. Recent, South Australia.

Fossarina (Minopa) hoffmeisteri Ladd, n. sp. 

Plate 4, figures 8-10

Small, globose, thin; whorls inflated; suture impressed, 

descending at aperture; aperture subcircular, oblique; 

peristome slightly projecting at base of columella. Sculpture consisting of faint spiral threads and fine lines of 

growth; spirals are better developed on earlier whorls 

than on body whorl. Many examples from younger beds 

retain traces of original color in the form of widely spaced 

oblique bands and irregular pointed cross bands of reddish brown.

Measurements of the holotype (Mu-4, Eniwetok, 40 

ft I, USNM 648265: height 4.1 mm, diameter 3.8 mm.

Occurrence: Twenty-four specimens from five drill 

holes on Eniwetok Atoll from near the surface to a depth 

of 670 feet; age, Recent to late Miocene (Tertiary g)\ 

two drill holes on Bikini Atoll yielded five specimens, 

one from post-Miocene beds (core) at 2351/^ feet and 

four others from early Miocene (Tertiary e\ beds 1,335- 

1,892 feet. The species still lives in the Marshall Islands 

but appears to be rare, as only a single dead shell was 

collected during Operation Crossroads.

Genus ASTELE Swainson 

Swainson, 1955, Royal Soc. Van Diemensland Papers, v. 3, p. 38.

Type (by monotypy): Trochus suhcarinatus Swainson. 

Recent, Tasmania.

Subgenus CALLISTELE Cotton and Godfrey

Cotton and Godfrey, 1935, South Australian Naturalist, v. 16, 

no. 2, p. 20.

Type (by original designation): Astele calliston Verco. 

Recent, Australia.

Astele (Callistele) engebiensis Ladd, n. sp. 

Plate 4, figures 11-13

Small, conical, thin; protoconch of about l 1/^ smooth 

whorls; sides flat, base gently convex; aperature quadrate, 

nacreous within; columella nearly vertical, slightly 

callused; umbilicus narrow, smooth sided; periphery 

sharply angled, scalloped. Sculpture consisting of fine, 

closely spaced spiral ribs, five above periphery on body 

whorl, nine below periphery on base; ribs and interspaces 

crossed by numerous fine oblique lines.

Measurements of the holotype, USNM 648266: height 

2.7 mm, diameter 2.9 mm.

The Recent shell A. calliston Verco described from 

Spencer Gulf, South Australia, has been the only species 

referred to Callistele. I have not seen specimens, but 

Verco's figures show that the Recent shell has a more 

prominently projecting peripheral cariria and fewer ribs 

on the base than does the fossil.

Occurrence: Holotype and only specimen from drill 

hole K-1B on Engebi Island, Eniwetok Atoll at a depth 

of 968-978 feet in beds assigned to early Miocene age 

(Tertiary /(.

Genus TROCHUS Linnaeus

Linnaeus, 1758. Systema naturae, 10th ed., p. 756.

Subgenus TROCHUS s.s.

Type (by subsequent designation, Iredale, 1912, 

Malacological Soc. London Proc., v. 10, p. 225): Trochus 

maculatus Linnaeus. Recent, Indo-Pacific.

Trochus (Trochus) maculatus Linnaeus 

Plate 4, figures 14, 15

Trochus maculatus Linnaeus, 1758, Systema naturae, 10th ed., 

p. 756.

Trochus (Infundibulurn) maculatus Linnaeus, Pilsbry, 1889, Manual Conchology, v. 11, p. 24, pi. 9, figs. 100, 1, 2, 3.

Trochus maculatus Linnaeus. Demond, 1957, Pacific Sci., v. 11, 

no. 3, p. 285.

Identifiable specimens of the variable type of Trochus 

s.s. were recovered from 13 localities in the detrital deposits and Agana Argillaceous Members of the Pliocene 

and Pleistocene Mariana Limestone of Guam (figured 

specimen from USGS 20636, USNM 648248) and from 

one additional locality (USGS 21383) on the island that 

may be referred to the upper Tertiary Alifan Limestone. 

Incomplete specimens that probably represent this 

species were also collected from Quaternary beds on 

Saipan (Tanapag Limestone) and from an unnamed 

coastal limestone on Espiritu Santo Island in the New 

Hebrides. These fossil occurrences are not the first, because the species has been reported from the Pliocene of 

Java and Quaternary of Timor and Billiton. Recent 

shells are widely known from Samoa to Fiji, the Philippines, the Ryukyus, Japan, Indonesia, and the Indian 

Ocean.

Trochus (Trochus) histrio (Reeve) 

Plate 4, figures 16-18

Turbo histrio Reeve, 1848, Zool. Soc. London Proc., pt. 16, p. 52. 

TrocJius histrio Reeve, 1861, Conchlogica Iconica, v. 13, pi. 15,

fig. 90. 

Trochus calcaratus Pilsbry, 1889, Manual Conchology, v. 11, p.

30. pi. 2, fig. 15; pi. 8, figs. 83, 84. 

Trochus histrio histrio Reeve, Demond, 1957, Pacific Sci., v. 11,

no. 3, p. 285, fig. 1.
38 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Small; upper surface of whorls bearing six rows of 

rounded circular, elongate, and slightly oblique granules; 

basal row on upper whorls forming prominent open 

pustules, 15 on penultimate whorl; on last whorl granules 

become smaller, more uniform in size, and pustules are 

not open; base with 10 concentric rows of beads; on outer 

half of base, rows of fine beads alternate with rows of 

larger beads; pseudoumbilicus with 2 smooth spiraling 

plicae. Faded traces of original color, broad red axial 

bands on the spire and spiral lines of short red dashes 

on the base, are preserved on both fossil specimens from 

Eniwetok.

Measurements of the figured specimen, USNM 648249: 

height 11.2 mm, diameter 13.4 mm.

Occurrence: Cuttings from drill hole F-l, Eniwetok, 

at a depth of 110-120 feet (figured specimen); a fragment was also recovered from cuttings in the same hole 

at a depth of 80-90 feet; age, Recent. A worn specimen 

from the Miocene I Tertiary /) Suva Formation at Viti 

Levu (sta. 160), probably represents the same species. 

Recent shells were collected on reef at Eniwetok and from 

beach drift there and at Bikini. The species also is known 

from other western Pacific islands including Palau, 

Mariana, Ellice, Loyalty, Ryukyu, and Line groups and 

from southern Japan and the South China Sea.

Trochus (Trochus) incrassatus Lamarck

Trochus incrassatus Lamarck, 1822. Hist. Nat. Animaux sans

Vertebres, v. 7, p. 20.

Reeve, 1861, Conchologica Iconica, v. 13, fig. 77. 

Pilsbry, 1889, Manual Conchology, v. 11, p. 26, pi. 6, figs.

48-50. 

Trochux incrassatns crenifems Kiener, Pilsbry, 1889, Manual

Conchology, v. 11, p. 27, pi. 7, figs. 67, 68. 

Ostergaard, 1935, [parti, B. P. Bishop Mus. Bull. 131. p. 46-47.

Represented by four incomplete and poorly preserved 

fossils from the shore rocks at Houma, Tongatabu, 

Tonga (sta. 3). J. M. Ostergaard collected the fossils 

and identified them with Recent shells from the same 

area referring them to T. incrassatus crenifems Kiener. 

The fossils, however, are not strongly tuberculate around 

the periphery, as are shells commonly referred to Kiener's 

variety. The base of the fossils is marked by 11 or 12 

concentric ribs rather than the 7 or 8 normally shown by 

T. incrassatus. The fossils are probably Pleistocene. 

Recent shells have been reported from various island 

groups, including Tonga, Samoa, and Japan.

Trochus (Trochus) tubiferus Kiener 

Plate 4, figure 19

Trochus tubijems Kiener, Fischer, 1880, Species general des coquilles, vivantes, Troque, v. 37, fig. 3. 

Pilsbry, 1889, Manual Conchology, v. 11, p. 31, pi. 6, figs.

62, 63. 

Ostergaard, 1935, B. P. Bishop Mus. Bull. 131, p. 47.

Four specimens of this species, characterized by a row 

of pustules at the base of each whorl and by numerous 

lirae on the flattened base, were collected by Ostergaard 

from elevated limestone on Tongatabu, Tonga (stas. 

2_4); age, probably Pleistocene. Measurements of the 

figured specimen from station 2, B. P. Bishop Museum, 

geology No. 1339: diameter 25.9 mm, height (incomplete) 

20.8 mm. The Recent shells have been reported from 

Tonga, Fiji, Ellice Islands, Loyalty Islands, and New 

Caledonia in the southwest Pacific.

Genus CLANCULUS Montfort

Montfort 1810, Conchyliologie systematique, v. 2, p. 191. 

Subgenus CLANCULUS s.s.

Type (by original designation): Trochus pharaonius 

Linnaeus. Recent, Red Sea.

Clanculus (Clanculus) clanguloides fijiensis Ladd 

Plate 4, figures 20-22

Clanculus (Clanculus) clanguloides fijiensis Ladd, 1945, B. P. 

Bishop Mus. Bull. 181, p. 352, pi. 50, figs. H, I.

Type material (four specimens) collected from the 

Ndalithoni Limestone, probably Pliocene (Tertiary h), 

on Vanua Mbalavu in eastern Fiji; an incomplete mold 

from the so-called older limestone (possibly Tertiary /) 

of the island of Fulanga in the same area (sta. L-78) may 

also represent this species.

Genus TECTUS Montfort

Montfort, 1810, Conchyliologie systematique, v. 2, p. 187. 

Subgenus TECTUS s.s.

Type (by original designation): Tectus pagodalis= 

Trochus mauritianus Gmelin. Recent, Indonesia.

Tectus (Tectus) mauritianus (Gmelin) 

Plate 4, figure 23

Trochux mauritianus Gmelin, 1791, Systema naturae, 13th ed.,

p. 3582. 

Trochus (Tcctux) niduiititnuis CJmeJin. Pilsbry. 1899. Manual

Conchology, v. 11, p. 23, pi. 2, figs. 11, 12; pi. 4, figs. 24,

25, 27.

A single incomplete example of this widely distributed 

Recent Indo-Pacific type of the genus was collected by 

Harold Stearns from a limestone pit I.USGS 21028) on 

Espiritu Santo Island, New Hebrides, at an altitude of 

240 feet;'age, Quaternary. The characteristic projecting 

peripheral tubercles are well preserved on the fossil. 

Measurements of the specimen, USNM 648250: height 

(incomplete) 16.5 mm, width 17.4 mm.
PALEONTOLOGY 39

Tectus (Tectus) pyramis (Born)

Trochus pyramis Born, 1778, Index Rerum Naturaeium Musei 

Caesarei Vindobonensis, pt. 1, Testacea, p. 338.

Trochus obeliscus Gmelin, 1791. Systema naturae, 13th ed., p. 

3579.

Trachn* (Tectttx) ob<>lixc«K (iinelin. Pilsbry. 1889. Manual

Couchology, v. 11, p. 19, pi. 2, figs. 13, 14. 

Ostergaard, 1935, B. P. Bishop Mus. Bull. 131, p. 47.

Ten poorly preserved but identifiable examples of this 

widely distributed western Pacific species were collected 

by Cloud and by Ladd from the Pleistocene Tanapag 

Limestone of Saipan (USGS 17387 and 21407 respectively). Ostergaard collected six specimens (identified 

as T. obeliscus Gmelin) from the sea cliff near Houma 

(sta. 3) on Tongatabu, Tonga, in rock that is probably 

late Pleistocene in age.

Tectus (Tectus) cf. T. bomasensis (Martin) 

Plate 4, figure 24

Medium in size, conical, higher than wide; base flat, 

meeting the body whorl at a sharp angle; nonumbilicate 

but with a strong columellar fold that is bordered by a 

broad smooth groove. Sculpture consisting of a prominent double nodose spiral ridge at the base of each 

whorl; lower part of ridge larger than upper; above the 

peripheral ridge each whorl bears three beaded riblets; 

on the body whorl the grooves between each two riblets 

contains a fine spiral cord; base marked by about eight 

beaded concentric cords.

Measurements of the figured specimen, USNM 648251: 

height 15.1 mm, diameter 13.6 mm.

The single Fijian fossil is incomplete, but it appears to 

be closely related to, if not identical with, T. bomasensis 

described by Martin (1917, p. 261, pi. 3, figs. 90a, b) 

from the lower Miocene of Java.

The fossil resembles T. fenestratus (Gmelin), a Recent 

species that occurs in Fiji and other Pacific and Indonesian islands. T. fenestratus is a variable species, and 

some shells show a dual ridge along the periphery, but it 

is not as prominent as in the fossil; the Recent shell is 

likewise much more strongly nodose than the fossil.

Occurrence: Conglomeratic facies of the Mba series at 

locality MR-20, about 3 miles south of Mba, Viti Levu, 

Fiji, collected by M. R. Rickard.of the Fiji Geological 

Survey Department; age, probably Pliocene (Tertiary 

h).

Subgenus ROCHIA Gray

Gray, 1857, Guide Systematic Distrib. Mollusca British Mus., 

pt. 1, p. 148.

Type (by monotypy): Trochus acutangulus Chemnitz 

=Trochus conus Gmelin. Recent, Indo-Pacific. Also 

reported from the Pliocene or Quaternary of Timor.

Tectus (Rochia) niloticus (Linnaeus) 

Plate 4, figure 25

Trochus ii-iloticus Linnaeus. 1767, Systema naturae 12th ed., no.

579, p. 1227.

Pilsbry, 1889, Manual Conchology, v. 11, p. 17, pi. 1, figs. 5-8. 

Demond, 1957, Pacific Sci., v. 11, p. 285. 

MacNeil, 1960, U.S Geol. Survey Prof. Paper 339, p. 25, pi.

18, figs. 3, 5. 

Trochus (Rochia) niloticus Linnaeus, Ladd, 1934, B. P. Bishop

Mus. Bull. 119, p. 202.

Rippingale and McMichael, 1961, Queensland and Great Barrier Reef shells, Jacaranda Press, Brisbane, p. 31, fig. 19.

A large and well-preserved example of this widely distributed Recent species was collected by H. T. Stearns 

from a coral pit (USGS 21029) on Espiritu Santo Island 

in the New Hebrides at an altitude of 215 feet. Though 

part of the body whorl is broken, the shell (USNM 

648252) shows its nacreous luster and traces of its original color pattern. The deposit is probably not older 

than Pleistocene. The species has also been reported 

from the Pliocene of Sumatra and Java and the Pliocene 

and Pleistocene of Okinawa.

Genus ISANDA H. and A. Adams

H. and A. Adams, 1854, Zool. Soc. London Proc., for 1853, p. 

189.

Type (by original designation): Isanda coronata A. 

Adams. Recent, Australia.,

The genus Isanda includes small heavy polished trochids having an open umbilicus and smooth interior. 

They are widespread in the Indo-Pacific and Australian 

area.

Subgenus PARMINOLIA Iredale 

Iredale, 1929. Queensland Mus. Mem. 9, p. 271.

Type (by original designation): Mineola agapeta Melvill and Standen (1896)=Mom7ea apicina Gould (1861). 

Recent, South Pacific.

Isanda (Parminolia) apicina (Gould)

Plate 5, figures 1-4

Monilea apicina Gould, 1862, Boston Soc. Nat. History Proc.,

p. 16. 

Monilea agapeta Melvill and Standen, 1896, Jour. Conchology

[Leeds] v. 8, p. 312, pi. 11, fig. 77. 

Monilea apicina Gould, Pilsbry, 1889, Manual Conchology, v.

11, p. 254. 

Johnson, 1964, U.S. Natl. Mus. Bull. 239, p. 41, pi. 14, fig. 4.

The following description is based on the fossil material. Small, conical, solid; apex sharp, about five inflated 

whorls distinctly angled a short distance below suture 

and on body whorl, obscurely angled at periphery; aperture subcircular, outer lip thin, inner lip thickened, bearing a basal tooth and slightly scalloped by extensions
40 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

that cover the ends of two ribs that spiral into the umbilicus; outer of two umbilical ribs larger and beaded; 

umbilicus narrow and deep. Sculpture consisting of closeset spiral ribs crossed by fine axial lines; ribs wider on 

base near umbilicus. Two of the fossils retain patches 

of reddish-brown on the upper parts of penultimate and 

body whorls.

Measurements of the figured specimen, (E-l, 60-70 

ft) USNM 648267: height 3.9 mm, diameter 4.0 mm. 

Gould's type USNM 24159 (pi. 5, figs. 3, 4) measures: 

height 4.9 mm, diameter 5.9 mm.

The Marshall Island specimens, both surface shells 

and those from drill holes, are smaller than Gould's type 

and are less sharply angled below the suture; the second 

(lower) funiclc in the umbilicus is less well developed in 

the Marshall Island shells.

Occurrence: Eight specimens from drill holes on Eniwetok at depths from 1-243 feet; age, Recent; in Bikini 

drill holes, one specimen at 40 feet, three others at depths 

of 1,356-1,850 feet; the deeper specimens from the early 

Miocene (Tertiary e].

Gould's type (USNM 24159) is labeled "Coral Sea" 

but the published description cites Port Jackson [Sydney] , Australia. The Recent shells described by Melville 

and Stamlen were collected in the Loyalty Islands. The 

species is common in collections of drift shells from both 

Eniwetok and Bikini.

Genus MONILEA Swanson

Swanson, 1840, Treatise on malacology, p. 352.

Subgenus MONILEA s.s.

Type (by monotypy): Trochus callijerus Lamarck. 

Recent, Indo-Pacific; also reported from Pliocene of 

Java.

Monilea (Monilea) mateana Ladd 

Plate 5, figures 5-8

Monilcn (Monilea) mateana Ladd, 1934, B. P. Bishop Mus. Bull. 

119, p. 203, pi. 35, figs. 1, 2.

Small, solid; inner surface of outer lip has 10-12 

strong lirations with small liration in interspaces; 

columella dentate below; umbilicus wide with a broad 

ridge or funicle spiraling up its side to terminate against 

the dentate part of the columella; funicle, in some specimens marked with a median groove. Sculpture consisting 

of strong spiral ribs beaded by axial striae. On the base 

the ribs arc flattened and subecmal in size; on the upper 

parts of the whorl, they are rounded, more strongly 

beaded and each second or third rib is larger than the 

others. Shell marked exteriorly by axial bands of reddish brown.

Holotype: B. P. Bishop Museum, geology No. 1196 (pi. 

5, figs. 5, 6): height 7.0 mm, diameter 8.0 mm. Figured 

specimen, USNM 648392 (pi. 5, figs. 7, 8): height 6.7 mm, 

diameter 7.2 mm.

Examination of additional specimens collected from 

the type locality- (Viti Levu, sta. 160) has shown that the 

median depression in the funicle is a variable feature and 

that the internal lirations and surface ribs are less constant than formerly thought.

M. mateana is most closely related to M. (Monilea) 

marshallensis Ladd, n. sp., a younger species from the 

Marshall Islands drill holes, described below.

Occurrence: Many specimens from stations 160 and 

160A, Viti Levu, and a single shell from station L493, 

Lakemba, Fiji; age, Miocene (Tertiary /).

Monilea (Monilea) marshallensis Ladd, n. sp. 

Plate 5, figures 9-12

Small, globular, solid; edge of outer lip thin, the thicker 

part within bearing 9 or 10 strong lirations; columella 

dentate below; umbilicus moderately wide, partly filled 

by a broad funicle. Sculpture consisting of strong spiral 

ribs beaded by axial striae; on the base the ribs may 

alternate with weaker ones.

Holotype: USNM 648270: height 3.9 mm, diameter 

3.4 mm. Paratype A (USNM 648268): height 4.1 mm, 

diameter 4.1 mm.

The new species appears to be very closely related to 

M. mateana from the lower Miocene of Fiji. The Marshall Island fossils have a narrower umbilicus and show 

only one set of lirations within the aperature.

Examples of M. marshallensis were not found in the 

collections of Recent shells made at Bikini and Eniwetok 

Atoll.

Occurrence: Holotype from drill hole K-1B, Eniwetok 

Atoll at a depth of 1,248-1,259 feet; lower Miocene 

(Tertiary e) ; numerous other Eniwetok occurrences 

range from near the surface to 880 feet (Recent to Tertiary /). On Bikini, paratype A was recovered in drill 

hole 2A from core at a depth of 235 feet; age, postMiocene; a dozen other Bikini occurrences range downward to 1,135 feet; age, Tertiary e.

Monilea (Monilea) lifuana Fischer 

Plate 5, figures 13, 14

Trochus (Monilea) lijuanus Fischer, 1878, Jour, conchyliologie,

v. 26, p. 63. 

Monilea lifuana Fischer, Pilsbry, 1889, Manual Conchology. 11,

p. 252, pi. 41. figs. 6, 7; pi. 59, figs. 64, 65.

Small, depressed, thin; body whorl inflated, broadly 

angled at periphery; aperture subquadrate, smooth 

within; inner lip thickened below; umbilicus narrow and
PALEONTOLOGY 41

deep, partially filled by a heavy funicle. Sculpture consisting of fine spiral lines crossed by oblique axial lines 

of growth; axial lines more conspicuous on base near 

umbilicus than elsewhere. Measurements of the figured 

specimen, USNM 648269: height 5.2 mm, diameter 6.9 

mm.

Occurrence: A single specimen from drill hole En-4, 

Eniwetok Atoll, at depth of 2 feet; age, Recent.

The species was described from the Loyalty Islands 

but has also been collected in Japan and on Bikini and 

Eniwetok Atolls in the Marshall Islands. One specimen 

was dredged alive from a depth of 180-200 feet in Bikini 

lagoon.

Monilea (Monilea) belcheri (Philippi) 

Plate 5, figures 15, 16

Trochus belcheri Philippi, 1849, Zeitschr. Malakozool., p. 148. 

Monilea (Monilea) belcheri Philippi, Pilsbry, 1889, Manual 

Conchology, v. 11, p. 250, pi. 61, figs. 3, 4.

Medium in size, depressed; whorls inflated, suture 

deeply incised; aperture subquadrate, smooth within; 

outer lip thin; columella oblique; umbilicus moderately 

wide, partially filled by a strong spiral funicle. Sculpture 

consisting of about 30 short close-set spiral ribs that, on 

the upper surface, show a tendency to alternate in size.

Measurements of the figured specimen, B. P. Bishop 

Museum, geology No. 1235: height 8.6 mm, diameter 

11.1 mm.

Occurrence: Single specimen from station 320, Viti 

Levu, Fiji; age, late Tertiary; a specimen wdth fewer 

ribs but probably representing the same species was collected from the Futuna Limstone at station 304 on the 

island of Lakemba in eastern Fiji; age, Miocene (Tertiary /). Recent shells are known from Tonga, Fiji, New 

Caledonia, and Japan. The fossils are more strongly 

ribbed on the base and more uniformly ribbed above than 

are the Recent shells.

Family STOMATELLIDAE 

Genus PSEUDOSTOMATELLA Thiele

Thiele, 1921, Revision des Systemes Trochacea, p. 29. 

Subgenus PSEUDOSTOMATELLA s.s.

Type (by original designation): Stomatella pupyracea 

"Chemnitz," A. Adams. Recent, Indo-Pacific.

Pseudostomatella (Pseudostomatella) maculata (Quoy and 

Gaimard)

Plate 5, figures 17, 18

Stomatella. maculata Quoy and Gaimard, 1834, Voyage de 1'Astrolabc, Zoologir. v. 3, p. 305, pi. 66 (bis), figs. 13-16.

Reeve, 1874, Conchologica Iconica. v. 19, Stomatella, pi. 1, 

fig. 5.

Pilsbry. 1890, Manual Conchology. v. 12, p. 13, pi. 51, figs. 

17-19; pi. 52, figs. 60, 61.

Small, moderately elevated, with four inflated whorls; 

columellar margin flattened; sculpture consisting of 

spiral ribs; above the periphery the strongest of three 

sets of ribs are beaded by oblique axial striae; the middlesized set of ribs shows traces of beading; below the 

periphery the ribs are less conspicuous.

Measurements of the figured specimen, USNM 648271: 

height 10.5 mm, diameter (outer lip incomplete) 11.6 

mm.

Occurrence: Six specimens collected from the Ndalithoni Limestone; age, probably Pliocene (Tertiary h); 

Vanua Mbalavu, Fiji (sta. HOB). The species, originally 

described from Recent shells from the Santa Cruz 

Islands, has since been collected westward to Torres 

Straits, eastward to the Society Islands, and northward 

to the Marshall Islands.

Genus STOMATIA Helbling

Helbling, 1779, Abh. Privatgesell., Prag, v. 4, p. 124, pi. 2, figs. 

34, 35.

Type (by monotypy): Stomatiu phymotis Helbling. 

Recent, Indo-Pacific.

Stomatia cf. S. phymotis Helbling 

Plate 5, figure 19

Small, resembling a high-spired Haliotis; last whorl 

with double keel whose lower ridge bears prominent 

nodes; strong plicas present on body whorl immediately 

below suture.

Measurements of the figured specimen, USNM 648272: 

width 8.5 mm, height 7.3 mm.

Occurrence: USGS 20534 on outskirts of Taguag near 

west coast of Guam; probably Alifan Limestone; age, 

Tertiary g or h.

The single fossil is a mold showing the larger external 

markings. It seems closely related to, possibly identical 

with, the type S. phymotis, a variable and widely distributed Recent Indo-Pacific species. The body whorl 

of the fossil does not descend as deeply as on the Recent 

shells. The Guam specimen appears to be the first fossil 

record of the genus.

Genus SYNAPTOCOCHLEA Pilsbry 

Pilsbry, 1890, Manual Conchology, 12, p. 6, 25.

Type (by original designation): Stomatella montrouzieri Pilsbry. Recent, New Caledonia.

Synaptocochlea concinna (Gould) 

Plate 5, figures 20-23

Stomatella concinna Gould, 1845, Boston Soc. Nat. History Proc.,

v. 2, p. 26. 

Adams. A.. 1854. in Thesaurus Conchyliorum, 2. p. 831, pi.

173, figs. 20, 21. 

Johnson, 1964, U.S. Natl. Mus. Bull. 239, p. 58, pi. 21, fig. 7.
42 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Stomatt'lla (Synaptocochlea) conciima Gould, Pilsbry, 1890, Manual Conchology, v. 12, p. 28, pi. 2, figs. 6, 7; pi. 55, figs. 

27, 28.

Small, ovate, thin; body whorl large, aperture broadly 

oval; upper margin of outer lip turned down at junction 

with penultimate whorl. Sculpture consisting of fine 

spiral riblets, close set on most of shell but more widely 

separated near aperture; riblets beaded by lines of 

growth; on upper and lower thirds of shell the ribs are 

intermittently dark red, the streaks being discernible inside the aperture; on the middle (peripheral) third of the 

shell the ribs are uncolored.

Measurements of the figured specimen, USNM 648273: 

diameter 2.7 mm, height 3.0 mm.

The ornamentation and color pattern appear to distinguish this small species from all others assigned to the 

genus.

Occurrence: Figured specimen from drill hole F-l, 

Eniwetok Atoll, at a depth of 60-70 feet; three specimens 

in other drill holes even closer to surface; age, Recent; 

Recent shells were recovered from beach drift at Rongerik 

Atoll in the Marshall Islands. Gould's types were collected in Hawaii, and the species has also been reported 

from the Tuamotu (Paumotu) group.

Synaptocochlea rosacea (Pease) 

Plate 5, figure 24

Gena rosacea Pease, 1867, Am. Jour. Conchology, v. 3, p. 284,

pi. 24 [a] fig. 1. 

Pilsbry, 1890, Manual Conchology, v. 12, p. 41, pi. 55, fig. 12.

Small, elongate-oval, moderately convex; spire posterior, whorls slightly angulated, body whorl flattened 

near apex. Entire shell marked by close-set concentric 

striae, which become less conspicuous near the-outer lip, 

and by fine lines of growth. Traces of irregular areas of 

brown are preserved on the body whorl.

Measurements of the figured specimen (E-l, 30-35 ft) 

USNM 648274: length 4.5 mm, breadth 3.0 mm, convexity 1.3 mm.

Occurrence: Two specimens from drill hole E-l, Eniwetok Atoll, at a depth of 30-35 feet; age, probably 

Recent. Pease described Recent material from the 

Tuamotu f Paumotu | Islands. A minute shell from drill 

hole 2B on Bikini Atoll at a depth of 1,555-1,566 feet 

(Tertiary /) probably represents this species.

Synaptocochlea lekalekana (Ladd) 

Plate 5, figures 25, 26

Kiiittm Ichtlckdhtim Ladd, 1945, B. P. Bi.-liop Mu.-. Bull. 181. 

p. 357, pi. 50, figs. O, P.

No additional material collected. Species based on 

four specimens collected from the Ndalithoni Limestone,

probably Pliocene (Tertiary h), Vanua Mbalavu (stas. 

HOB and HOC), Fiji.

Synaptocochlea marshallensis Ladd, n. sp. 

Plate 5, figures 27, 28

Minute, ovate; spire low; aperture very large, wider 

than high, upper margin meeting penultimate whorl at 

midpoint; sculpture consisting of fine spiral ribs, cut by 

close-set axial lines.

Measurements of the holotype (K-1B, 757-769 ft), 

USNM 648275: height 1.5 mm, diameter 2.3 mm.

8. marshallensis is smaller and more strongly sculptured than »S. lekalekana (Ladd) from the Ndalithoni 

Limestone, probably Pliocene, of Vanua Mbalavu, Fiji.

Occurrence: Two specimens from K-1B, Eniwetok 

Atoll, at depth of 757-769 feet; age, late Miocene (Tertiary g). An incomplete specimen from E-l at depth of 

870-880 feet (Tertiary /I probably represents the same 

species.

Family ANGARIIDAE (DELPHINULIDAE) 

Genus ANGARIA Roding

Roding, 1798, Mus. Boltenianum, pt. 2, p. 71.

Type (by subsequent designation, Fischer, Species 

general et Iconographic des coquilles vivantes * * * p. 58, 

Paris, 1875): Turbo delphinus Linnaeus. Recent, IndoPacific; also reported from the upper Miocene of Java 

and Nias, the Pliocene and Pleistocene of Okinawa, and 

the Quaternary of Soemba.

Angaria delphinus (Linnaeus) 

Plate 5, figures 29-34

Turbo delphinus Linnaeus, 1758, Systema naturae, 10th ed., p. 764.

Angnria delphinus Roding, 1798, Mus. Boltenianum, pt. 2, p. 71.

MacNeil, 1960, U.S. Geol. Survey, Prof. Paper 339, p. 29, pi.

16, figs. 6, 11-12. 

Delphinula distorta (Linnaeus) Ladd, 1934, B. P. Bishop Mus.

Bull. 119, p. 205-206, pi. 35, fig. 9.

A reexamination of the two Fijian fossils described by 

Ladd in 1934 and an additional specimen collected from 

the same locality (USNM 648393) indicate that all fall 

within the range of the highly variable Recent type of 

the genus. The Fijian fossils are from the conglomerate 

at the base of the limestone section in the Miocene Suva 

Formation (Tertiary /) on AValu Bay, Viti Levu.

On a single coarsely recrystallized specimen from 

Guam, the surface plicae are poorly preserved but the 

general form and arrangement strongly suggest the type 

species. The specimen, USNM 648276, measures: height 

30.2 mm, diameter 30.6 mm. It was collected from the 

Alifan Limestone (Tertiary g or h) at USGS locality 

20720.
PALEONTOLOGY 43

Family TURBINIDAE 

Genus ASTRAEA Roding

Roding, 1798, Mus. Boltenianum, pt. 2, p. 79.

Type (by subsequent designation, Suter, 1913, Manual 

New Zealand Mollusca, p. 166): Trochus imperialis 

Gme\in=T. heliotropium Martyn. Recent, New Zealand.

Subgenus ASTRALIUM Link, 1807

Link, 1807, Beschreibung der Naturalien-Sammlung der Universitat zu Rostock, p. 135.

Type (by subsequent designation, Fischer, in Kiener, 

1875, Species general et Iconographie des Coquilles 

vivantes, Genre Turbo, p. 5): Turbo calcar Linnaeus. 

Recent, Indo-Pacific.

Astraea (Astralium) rhodostoma (Lamarck)

Plate 6. figures 1-5

Truchiix rltodostomun Lamarck, 1822, Hist. Xat. Animaux sans

Vertebres, v. 7, p. 13. 

Axlralium (Cyclocatitha) petrosum Martyn, Pilsbry. 1888, Manual

Conchology, v. 10, p. 234, pi. 64, figs. 65, 66. 

Astralium petrusum virescens Pease, Ostergaard, 1935, B. P.

Bishop Mus. Bull. 131, p. 17. 

Astraea (Calcar) confragosum Gould, Ladd, 1945, B. P. Bishop

Mus. Bull. 181, p. 354.

Trochus (Infundibulum) calcaratm Souverbie, Abrard, 1946, 

Annales de paleontologie, v. 32, 48, pi. 4, fig. 9.

Sculpture variable but characteristically having two 

distinct rows of peripheral spines, those in the upper row 

numbering about 12 on the body whorl, those of the 

lower row smaller and more numerous; the columella is 

wide, has a shallow groove, and bears a denticle near its 

base.

Measurements of the figured specimen, USNM 648285: 

height 29.1 mm, diameter 25.3 mm.

The best preserved of Ostergaard's four Tongan fossils 

has many small subequal wrinkles, and the peripheral 

spines are not prominent.

Occurrence: A common and widespread species; fossil 

occurrences from Saipan (figured specimen from USGS 

21407; questionable specimen from USGS 17387); Guam 

(USGS 17416, 20574, 20616, 20634, 20636, 20732, 20981); 

Fiji (sta. 148, Ongea); Tonga (sta. 7, Tongatabu) ; New 

Hebrides (USGS 21028, Espiritu Santo and Eromanga) 

(Abrard) ; all occurrences in beds of post-Tertiary age.

The Recent shells have been collected from many island 

groups in the Pacific, from the Marshall Islands to Fiji.

Astraea (Astralium) aff. A. rhodostoma (Lamarck) 

Plate 6, figure 6

An external mold of an Astralium from the Main boring at Funafuti Atoll has sculpture similar to the variable A. rhodostoma but probably represents a distinct

species. The shell had two rows of peripheral spines, but 

those in the lower row are twrice as numerous as those in 

the upper; both rows are more oblique than in A. rhodostoma, the spines of the lower row on the fossil making 

an angle of slightly less than 45° with the base. Measurements of the figured impression, USNM 648286: height 

19.7 mm, diameter 18.7 mm.

Occurrence: In core 528A (British Mus. Nat. History), 

dolomitic limestone from a depth of 1,006 feet, Main 

Boring, Funafuti Atoll; age, probably Pleistocene.

Astraea (Astralium) eniwetokensis Ladd, n. sp. 

Plate 6, figures 7-9

Medium size, depressed conic; base slightly convex 

with narrow shallow umbilicus; whorls convex above, 

concave below; body whorl with 15 prominent rounded 

nodes above periphery with lesser number of smaller 

nodes that end as open scaly processes; on body whorl 

rows of smaller nodes lie between two main series; base 

with nine concentric spinose ribs; columella with low 

obliquely pinched tubercle.

Measurements of the holotype and only specimen, 

USNM 648290: height 7.9 mm, diameter 10.4 mm.

Resembles A. calcar (Linnaeus), type of the subgenus, 

but has a lower spire.

Occurrence: Drill hole F-l, Eniwetok Atoll, at depth 

of 790-800 feet; age, late Miocene (Tertiary g).

Astraea (Astraliuni) waluensis Ladd, n. sp. 

Plate 6, figures 10-12

Astraea (Calcar) sp. A, Ladd, 1934, B. P. Bishop Mus. Bull. 119, 

p. 205, pi. 35, figs. 7, 8.

Shell medium in size, thick, trochoid; aperture ovoid, 

channeled at the periphery, nacreous within; columella 

wide with shallow depression and an elongate basal 

tooth; whorls flattened; body whorl with seven or eight 

broad-based spines lying well above the periphery; small 

oblique wrinkles cover the areas between the large 

spines; periphery marked by a row of small close-set 

spines; base flattened, bearing numerous concentric 

spinose ribs.

Measurements of the holotype, USNM 648291: height 

12.9 mm, diameter 10.8 mm.

One of the two additional specimens representing this 

species has been designated the holotype. The form is 

closely related to the Recent A. rhodostoma Lamarck, 

but the fossils are smaller and less distinctly bicarinate. 

On the fossils the spines in the upper row are fewer and 

proportionately much larger.

Occurrence: Five specimens from the Suva Formation, 

Viti Levu, Fiji (sta. 160) ; age, early Miocene (Tertiary
44 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Astraea (Astralium) sp. A 

Plate 6, figures 13-15

Medium in size, trochoid; whorls flattened; base 

gently convex near middle, concave near periphery and 

near middle, concave near periphery and near columella; 

nonumbilicate; body whorl with about 10 low spiral ribs 

that are beaded by oblique ribs; spiral ribs on lower half 

of whorls scaly, especially the marginal rib which is more 

prominent than those above; base with a dozen concentric spinose ribs; aperture broken.

Measurements of the figured specimen, USNM 648292: 

height (incomplete) 11.2 mm, diameter (incomplete) 

13.9 mm.

Resembles Axtrued eniwetokcnsis n. sp. from slightly 

younger beds in the same drill hole but has a sharper 

spire and finer sculpture. May represent an imdescribed 

form, but the single specimen available is too incomplete 

to be made a type.

Occurrence: Drill hole F-l, Eniwetok Atoll, at a depth 

of 840-850 feet; late Miocene (Tertiary </l.

Astraea (Astralium) sp. B 

Plate 6, figures 16-18

Small, trochoid; base flat and nonumbilicate; periphery 

carinate, extended into broad flattened regularly spaced 

spines, 10 being present on body whorl; whorls flattened 

above periphery, with 4 siibequal beaded spiral ribs; 

base flat with 6 fine spiral ribs.

Measurements of the figured specimen, USNM 648293: 

height 1.8 mm, diameter 2.1 mm.

The single fossil appears to be immature; it has not 

been identified with a described species.

Occurrence: Drill hole 2, Bikini Atoll, from core at a 

depth of 115 feet; age, Recent.

Astrea (Astralium) sp. C 

Plate 6. figures 19-20

The opercula described below appear to belong to a 

species of Astralium, possibly to one of the two large 

shells, A. eniwetokensis and A. sp. A, already described 

from the same Tertiary section in one of the drill holes 

that yielded some of the opercula. Each of the two shells 

recognized is represented by only a single specimen, and 

it is of course possible that still other species are completely unrepresented in the drill-hole samples. There 

are a total of 19 specimens of the heavy opercula. These 

structures arc nearly indestructible, and hence the high 

ratio of opercula to shells is understandable. The opercula show little variation and probably represent a single 

species.

Operculum broadly ellipsoidal, heavy; inner face 

flattened with a rounded edge and a broad shallow spiral

depression near the suture; nucleus below and to the left 

of the midpoint, the last whorl covering most of the inner 

face; outer face highly convex, broadly excavated near 

the margin except on the lower left side where the structure thickens to a rounded apex; to the left of the apex 

and below the midpoint there is a shallow spiral depression; surface more or less puckered by irregular shallow 

grooves.

Measurements of the figured specimen (K-1B, 937-947 

ft), USNM 648294: width 3.3 mm, height 2.8 mm.

Occurrence: A total of 15 opercula were recovered from 

the 3 deep holes on Eniwetok Atoll at depths of 558-947 

feet; four specimens were recovered from drill hole 2A 

on Bikini Atoll at depths of 925-1,063 feet. Age, late Tertiary (Tertiary f-h at Eniwetok; f-g at Bikini). A closely 

similar operculum was recovered from the Suva Formation on Viti Levu, Fiji (sta. FB-20) ; age, Miocene 

(Tertiary /).

Subgenus BELLASTRAEA Iredale

Iredale, 1924, Linnean Soc. New South Wales Proc., v. 49, p. 

182, 232.

Type (by original designation): Bellastraea keateueni 

Iredale (=Astraea fimbriata auct.). Recent, Australia.

Astraea (Bellastraea) sp. D

Plate 6, figures 21-23

Minute, lenticular; apex flattened, periphery with 

prominent flattened spines, 11 on last whorl; umbilicus 

wide and deep, bordered by a broad beaded rib. Measurements of the figured specimen (K-1B, Eniwetok, 841- 

853 ft) USNM 648295: height 1.1 mm, diameter 2.9 mm.

Occurrence: Figured specimen and six other examples 

from drill hole K-1B, Eniwetok Atoll, at depth of 841- 

853 feet in beds assigned to late Miocene (Tertiary g\ ; 

two additional specimens from same drill hole at depth 

of 863-873 feet, early Miocene (Tertiary /) ; one specimen from hole F-l, Eniwetok, at depth of 1,210-1,220 

feet (Tertiary e I ; a single specimen was found in drill 

hole 2A on Bikini Atoll at a depth of 1,030-1,034 feet 

(Tertiary /). The 11 small fossils are probably immature.

Astraea (Bellastraea) sp. E 

Plate 6, figures 24-26

Minute, planoconvex; spire depressed; periphery with 

a row of broad flattened upturned spines (nine on body 

whorl) ; suture impressed, scalloped near aperture by 

peripheral spines of preceding whorl; below periphery, 

whorl is semicircular in section with a low median ridge 

bearing prominent widely spaced, rounded knobs; this 

basal ridge spirals into the wide umbilicus as does an
PALEONTOLOGY 45

obscurely headed rib bordering that structure; aperture 

subcircular.

Measurements of the figured specimen, USNM 648296: 

height 1.2 mm, diameter 3.2 mm.

The aperture of the single small fossil is incomplete. 

It is possible that the shell is immature, but comparisons 

with large astraeids that have depressed early whorls do 

not support this possibility. The fossil probably represents an undescribed species, possibly an undescribed 

.siibgenus, but a new name must await better type material. The species differs markedly from Astrea sp. D 

that has been recovered from the same horizon on Eniwetok. The form described as sp. E is flatter and has an 

impressed suture; it has fewer peripheral spines, and 

these are strongly upturned. The whorl is more convex 

below and bears a strongly beaded ridge.

Occurrence: Drill hole K-1B on Eniwetok Atoll at a 

depth of 1,196-1,207 feet; from early Miocene (Tertiary 

e\.

Subgenus VITIASTRAEA Ladd, n. subgen.

Type: Astraea (Vitiastraea) holme si Ladd, n. sp.

Small; spire low; early whorls with a nodose keel or 

shoulder from the base of which a flat scalloped fringe 

spreads outward to conceal the suture; shoulder becomes 

obsolete on the body whorl and below it the scalloped 

fringe changes into a peripheral keel which, in turn, dies 

out before reaching the aperture; a third keel appears on 

the body whorl below the peripheral keel; it descends 

below the periphery and dies out before reaching the 

aperture. Aperture circular; umbilicus narrow, surrounded by a coarsely puckered rib.

The scalloped fringe that overlaps the suture on the 

early whorls indicates clearly that A. holmeai is an 

astraeid, but the pattern set by the other disappearing 

keels is not to be matched closely in any of the numerous 

subgenera of Asti'aea. The closest'approach seems to be 

in Ortnastraliitut Sacco, known from' the Miocene and 

Pliocene of Europe. In that group there is a spiny 

peripheral keel that, on the early whorls, covers the 

suture. Later whorls also have two other major keels, 

one above and one below the periphery. Both of these 

are armed with blunt knobs. None of the keels dies out 

before reaching the aperture, and the shell is imperforate.

Astraea (Vitiastraea) holmesi Ladd, n. sp. 

Plate 6, figures 27-29

Small, low spired; apex flat; early whorls with a 

strong nodose keel or shoulder from the base of which a 

thin flat scalloped fringe extends outward to conceal the 

suture completely; shoulder dies out on body whorl and 

scalloped fringe changes to a sharp peripheral keel which

also dies out before reaching aperture, a third spiral keel

 strong and beaded appears below the periphery on 

the body whorl; it descends gradually and dies out before 

reaching aperture. Aperture circular, outer lip thin, 

inner lip callused and broadly expanded below; umbilicus narrow, surrounded by a coarsely puckered rib.

Measurements of the holotype, USNM 648297: height 

2.4 mm, diameter 3.0 mm.

Occurrence: Holotype and only specimen from the 

Miocene (Tertiary /) Suva Formation on Viti Levu, 

Fiji (sta. 160).

Genus ARENE H. and A. Adams 

H. and A. Adams, 1854, Genera Recent Mollusca, v. 1, p. 404.

Type (by subsequent designation, Woodring, 1928, 

Carnegie Inst. Washington Pub. 385, p. 422): Turbo 

cruentatus Megerle von Miihlfeld. Recent, West Indies.

Arene (Arene) metaltilana Ladd, n. sp.

Plate 7, figures 1-6

Minute, strongly turreted; apex flattened; a smooth 

gently convex whorl of protoconch followed by 2% sculptured whorls; aperture subcircular, inner lip expanded 

below; umbilicus moderately wide and deep. Sculpture 

consisting of three spiral ribs that form a flattened 

peripheral band on the body whorl; uppermost rib 

strongest, turned upward and scalloped into rounded 

scales that are most prominent on the earlier whorls; 

middle peripheral rib smaller than other two; flattened 

areas above and below peripheral band bear obscure 

axials; a broad puckered rib spirals into the umbilicus.

Measurements of the holotype, USNM 648298: height 

1.2 mm, diameter 1.3 mm. Paratype, USNM 648299: 

height 1.2 mm, diameter 1.6 mm.

A. metaltilana is characterized particularly by the 

comparatively smooth flattened areas that lie above and 

below the strongly ribbed peripheral band.

Occurrence: Represented by only two shells, both from 

drill hole 2B on Bikini Atoll; holotype from a depth of 

1,702-1,713 feet and paratype from a depth of 2,297- 

2,307 feet; age. early Miocene (Tertiary e).

Arene (Arene) sp. A

Plate 7, figures 7, 8

Very small; spire moderately high, turreted; apex depressed; about four whorls, flattened above a prominent

-houlder; aperture subcircular; umbilicus narrow and 

deep, bordered by a heavy spiral. Sculpture consisting 

of three strong spiral ribs that form a flattened peripheral 

band on the body whorl; on earlier whorls the upper two 

of the primary whorls are conspicuously scalloped; three 

secondary spirals are present on the body whorl above
46 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

the peripheral bund and others occur on the base; still 

finer spirals occur between the primary spirals; close-set 

oblique axials, present over the entire shell, cause beading of the secondary spirals and a puckering of the 

umbilical rib.

Measurements of the figured specimen, USNM 648300: 

height 2.3 mm, diameter (incomplete) 2.6 mm.

The species is represented by a single specimen on 

which the peristome is not preserved. There seems little 

question about the generic reference, but I have not found 

a close living relative in the Pacific. The fossil is similar 

in many ways to A. mineata Dall, a Recent species from 

Santo Domingo and other parts of the Caribbean, but it 

has a more depressed apex, a more prominent peripheral 

band, and more conspicuously scalloped early whorls.

Occurrence: Drill hole 2A, Bikini Atoll, at a depth of 

742-747 feet; age, late Miocene (Tertiary </).

Genus LIOTINA Munier-Chalmas (in P. Fischer)

Munier-Chalmas in Fischer, P., 1885, Manual Conchology, p. 831.

Type (by subsequent designation) Cossman, 1888,

Catalogue Illustre Coquilles Fossiles * * *, v. 3, p. 53):

Delphinula gervillci Defrance. Middle Eocene, France.

Subgenus AUSTROLIOTIA Cotton

Cotton, 1948, Royal Soc. South Australia Trans., 72, p. 31.

Type (by original designation): Liotia botanica Hedley. Recent, New South Wales.

Liotina (Austroliotia) cf. L. botanica (Hedley)

Plate 7, figures 9-11

Small, lenticular, solid; about four whorls, gently convex above a weak shoulder, strongly and uniformly 

convex below; suture impressed; aperture circular and 

slightly oblique; peristome complete, outer lip thickened 

below shoulder to form a varixlike structure leading to 

a thick pad of callus that projects over part of the wide 

umbilicus. Sculpture consisting of 10 spiral ribs; the 3 

that lie above the shoulder are weak, the others, including 1 that spirals into the umbilicus, are strong; spirals 

crossed by axial ribs, about 20 on body whorl, giving the 

shell a latticed appearance.

Measurements of the figured specimen, USNM 648301: 

height 1.4 mm, maximum diameter 3.3 mm, minimum 

diameter 2.3 mm.

The single fossil Ls somewhat worn but seems to agree 

in all essential features with the larger L. botanica 

(Hedley, 1915, p. 710), type species of Austroliotia.

Occurrence: In drill hole F-4-A, Elugelab Island, 

Eniwetok Atoll, at a depth of 6-12 feet; age, Recent.

Subgenus DENTARENE Iredale

Iredale, 1929, Queensland Mus. Mem., v. 9, p. 274.

Type (by original designation): Dentarene sarcina 

Iredale, new name for Delphinula crenata Kiener. Recent, Philippines.

Liotina (Dentarene) loculosa (Gould)

Plate 7, figures 12-14

Lioiia laciiloxa Gould, 1862, Otia Conchologica, p. 114.

Johnson, 1964, U.S. Natl. Mus. Bull. 239, p. 103, pi. 5, fig.

15 above [not fig. 12]. 

Liotina cycloma Tomlin, 1918, Jour. Conchology, v. 15, no. 10,

p. 305, pi. 10, figs. 1, 2. 

Liotina (Dentarene) loculosa (Gould), Kuroda, 1960, Catalogue

of molluscan fauna of Okinawa Islands, p. 5.

Medium in size, heavy, discoidal; spire low, body 

whorl descending to a circular aperture surrounded by a 

strong erect varix; umbilicus narrow and deep, with a 

ridge that merges with the varix surrounding the lip. 

Whorls of protoconch smooth, remainder of shell covered 

by fine close-set axial lamellae. Six spiral cords recognizable on the body whorl; the smallest of these, next to 

the suture, bears regularly spaced spiny elevations; a 

second cord, somewhat larger, forms a low shoulder and 

bears similar spiny elevations; two very strong cords 

form the periphery and their prominent spines are connected by the bundles of axial lamellae that form the 

spines; a fifth cord near the middle of the base is comparable in size to the cord at the shoulder; a sixth cord 

that encircles the umbilicus is deeply notched like a cog 

wheel.

Measurements of the figured specimen (E-l, Eniwetok, 110-120 ft) USNM 648302: height 3.6 mm, 

diameter 5.1 mm.

L. locidoxa is similar to L. crenata (Kiener), type of 

the subgenus Dentarene, but that of Recent species, reported from the Philippines, Australia, and Ceylon, has 

a smooth base. L. infensa Finlay, a Recent Australian 

species, has wide umbilicus. L. chinenensis described by 

MacNcil (1960, p. 29, pi. 11, figs. 29-31) from the 

Pliocene of Okinawa is a larger, and proportionately 

higher form with a wide umbilicus and fewer peripheral 

spines.

Occurrence: Rare examples, total of seven specimens, 

in four drill holes on Eniwetok Atoll at depths of 2-120 

feet; all Eniwetok occurrences probably Recent. Common in beach drift at Rongerik Atoll; a single shell found 

at Bikini. The type, a Recent shell, was collected in the 

Ryukyu Islands. A single specimen from hole 2 on Bikini 

at depth of 86-87 feet is probably Recent; a worn specimen in the same hole from a depth of 1,366-1,377 feet 

(Tertiary e) may have been derived from a higher level.
PALEONTOLOGY 47

Liotina (Dentarene) sp. A

Plate 7, figures 15-17

Medium in size; spire depressed, suture impressed; 

umbilicus moderately wide, deep. Whorls of protoconch 

smooth, remainder of shell covered by fine close-set 

axial lamellae. Six spiral cords recognizable on the body 

whorl: the uppermost of these is broad and low, lying 

about one-third of the distance from suture to periphery; 

the peripheral cord is the strongest and is extended into 

sharp spiny processes that give the shell a stellate appearance when viewed from above or below; four cords with 

low regularly spaced spiny projections occur below the 

periphery, the lowest closely encircling the umbilicus; 

spiny projections on basal cords merge to form distinct 

axial ribs.

Measurements of the figured specimen (E-l, 2,590- 

2,600 ft I, USNM 648303: diameter (incomplete) 3.4mm, 

height (incompleteI 1.9mm.

Liotina sp. A is clearly distinct from L. loculosa Gould 

found in Recent beds at higher levels in Eniwetok drill 

holes. The Miocene shells have a lower spire, a wider 

umbilicus, and a single prominent peripheral cord; likewise, on the Tertiary shells the axial ribs below the 

periphery are much more conspicuous than on L. loculasa. 

The Miocene shells clearly represent an undescribed 

species but, because none of the available specimens has 

the aperture preserved, a specific name is withheld.

Occurrence: Five specimens from drill holes E-l and 

K-1B on Eniwetok Atoll at a depth of 936-2,600 feet; 

age, early Miocene (Tertiary e and /).

Liotina (Dentarene) sp. B

Plate 7, figures 18-20

A single incomplete specimen (USNM 648304) from a 

drill hole on Bikini Atoll closely resembles Liotina sp. A 

from Eniwetok but has more numerous cords on the body 

whorl three above the peripheral cord and four below 

 and lacks well-developed axial ribs on the base. The 

Bikini shell may represent a distinct species, but the 

single specimen does not show the apertural features and 

has, therefore, not been given a specific name. Measurements: diameter (incomplete) 2.2 mm, height (incomplete) 1.4 mm.

Occurrence: Drill hole 2B, Bikini Atoll, at a depth of 

1,629-1,639 feet in beds referred to early Miocene (Tertiary/).

Genus TURBO Linnaeus

Linnaeus, 1758. Systema naturae, 10th ed., p. 761.

Subgenus TURBO s.s.

Type (by subsequent designation, Montfort, 1810, 

Conchyliologie systematique, v. 2, p. 203): Turbo

ptthohitus Linnaeus. Recent, Indo-Pacific; also reported 

from upper Miocene and Pliocene of Java, the Pliocene 

and Quaternary of Timor and Okinawa, the Pliocene of 

Taiwan, the Quaternary of Celebes, and the Pleistocene* ?) of Tonga.

Turbo (Turbo) petholatus Linnaeus

Plate 7, figures 21, 22

Turbo petholatus Linnaeus, 1758, Systema naturae, 10th ed., p.

762.

Reeve, 1848, Conchologica Iconica, v. 4, Turbo: pi. 3, fig. 12. 

Sowerby, 1886, Thesaurus Conchyliorum Turbo, p. 191, pi.

40, fig. 46.

Pilsbry, 1888, Manual Conchology, v. 10: p. 193, pi. 40, fig. 14. 

Ostergaard, 1935, B. P. Bishop Mus. Bull. 131, p. 48. 

Ladd, 1945, B. P. Bishop Mus. Bull. 181, p. 354. 

MacNeil, 1960, U.S. Geol. Survey Prof. Paper 339, p. 31,

pi. 18, fig. 12.

Shell medium in size, turbinate, imperforate, solid; 

aperture circular, outer lip thin, inner lip callusecl; sculpture consisting of inconspicuous axial lines of growth.

Measurements of the figured specimens from Guam: 

(USGS 20653), USNM 648277: height (incomplete) 23.8 

mm, diameter 23.8 mm; (USGS 20720), USNM 648278: 

height 29.4 mm, diameter 27.9 mm.

Occurrence: On Guam, single specimens from half a 

dozen localities in the reef facies and Agana Argillaceous 

Member of the post-Miocene ^Mariana Limestone and 

from beds that probably belong to the late Tertiary 

Alifan Limestone (Tertiary g or h). Previously described 

(single specimen) from the Futuna Formation, early 

Miocene (Tertiary /) from Lakemba in eastern Fiji, the 

upper Miocene and Pliocene of Java. Common in postTertiary beds in the New Hebrides (USGS 21028, 

Espiritu Santo). Recent shells have been collected from 

many parts of the Indo-Pacific region.

Turbo (Turbo) petholatus thanus Ladd

Plate 7, figure 23

Turbo (Turbo) petholatus thanus Ladd, 1934, B. P. Bishop Mus. 

Bull. 119, p. 203, pi. 35, fig. 3.

Four additional specimens have been collected from 

the type locality in Suva, Fiji one juvenile and three 

adults. The color pattern, though faded, is recognizable 

as a series of revolving broken lines of dark spots and 

irregular areas, basically similar to those exhibited by 

living examples of T. petholatus.

Measurements of the figured specimen (Viti Levu, 

Fiji, sta. 160) USNM 648279: height 23.2 mm, diameter 

(incomplete) 23.2 mm.

Occurrence: Five specimens from station 160, Walu 

Bay, Suva, Fiji; age, Miocene (Tertiary /), Suva Formation. Two small specimens that apparently represent
48 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

this subspecies were collected from the Ndalithoni Limestone on Vanua Mbalavu in eastern Fiji (sta. HOC); 

age, probably Pliocene (Tertiary h}.

A dozen heavy opercula, apparently referable to this 

species, were collected with the shells at stations 160, 

160A, FB-20.

Subgenus MARMAROSTOMA Swainson

Swainson, 1829, Zool. Illus., 2d ser., v. 1, pi. 14.

Type (by original designation): Turbo chrysostomus 

Linnaeus. Recent, Pacific islands.

Turbo (Marmarostoma) chrysostomus Linnaeus

Plate 7, figure 24

Tui'ho cftri/Hoxtoniiix Linnaeus, 1758, Systema naturae, 10th ed.,

p. 762. 

Murimiroxloina cftnjsoxlomux Linnaeus, Swuinson, 1829, Zool.

Illus., 2d ser., v. 1, pi. 14. 

Turbo (Turbo) chnjsostomus Linnaeus, Pilsbry, 1888, Manual

Conchology, v. 10, p. 200, pi. 40, fig. 19.

A dozen specimens referable to this spirally ribbed and 

variable species were collected from several localities on 

Guam and one from the New Hebrides. Shells from both 

areas are strongly shouldered, the central part of each 

whorl being conspicuously flattened with strong scaly 

ribs at the top and bottom of the flattened band; ribs of 

two or three sizes alternate; on well-preserved specimens 

the scales on the main ribs are prominent open nodes.

Measurements of the figured specimen from Guam, 

USNM 648280: height 22.0 mm, diameter 22.9 mm.

Occurrence: Guam at USGS localities 20636 (figured 

specimen), 20533, 20732, and 21377 (all from the Agana 

Argillaceous Member of the Pliocene and Pleistocene 

Mariana Limestone) ; single incomplete specimen from 

New Hebrides, USGS 21028 in beds believed to be no 

older than Pleistocene. Recent shells have been collected 

in many island groups in the southwest Pacific.

Turbo (Marmarostoma) argyrostomus Linnaeus

Plate 7, figures 25, 26

Turbo argyrostomus Linnaeus, 1758, Systema naturae, 10th ed.,

p. 764.

Reeve, 1848, Conchologica Iconica, v. 4, pi. 2, fig. 7. 

Pilsbry, 1888, Manual Conchology, v. 10, p. 197-198, pi. 40,

fig. 18; pi. 42, fig. 41; pi. 46, fig. 8. 

Ostergaard, 1935. B. P. Bishop Mus. Bull. 131, p. 47. 

Demond, 1957, Pacific Sci., v. 11, p. 268-269. 

Marmarostoma argyrostoma (Linnaeus), MacNeil, U.S. Geol. 

Survey Prof. Paper 339, p. 31, pi. 18, fig. 4.

This species seems to be the most abundant of several 

large strongly ribbed turbos that are widely distributed 

in the island area today, and the fossil collections suggest 

that this species was also most abundant in Pleistocene

time. Plate 7, figure 25, shows a specimen with heavy 

operculum in place.

Measurements of the figured specimens: (1) specimen 

from Saipan (USGS 17387), USNM 648281; height (tip 

of spire broken) 59.5 mm, diameter 54.5 mm; (2) specimen from Guam, (USGS 20679) USNM 648282; height 

(spire incomplete) 62.6 mm, diameter 55.1 mm.

T. argyrostomus is closely related to T. setosus 

Gmelin, which is a species that has been reported over 

much of the same range although in less abundance. The 

two species show a distinct tendency to intergrade. End 

members of the two series exhibit four rather striking 

differences: T. argyrostomus has a strong shoulder, its 

ribs are spinose, it is distinctly umbilicate, and the inner 

side of its heavy operculum is flat or slightly convex. 

T. setosus shows no shoulder, its ribs are smooth except 

for growth lines, it is nonumbilicate, and the inner side 

of its operculum is distinctly concave. However, in a 

large series of Recent shells of T. argyrostomus there is 

a considerable variation in the development of the 

shoulder, the spines, and the umbilicus. The inner face 

of the operculum seems a constant character, but unfortunately one that can only rarely be used in studying 

fossils. At Funafuti, Hedley (1899a, p. 408) found T. 

argyrostomus on the west (lee) side of the atoll and 

T. setosus on the east (windward) side.

Occurrence: One of the commonest species in the 

Pliocene and Pleistocene Mariana Limestone of Guam, in 

the Pleistocene Tanapag Limestone of Saipan, and in 

limestones of Quaternary age in the New Hebrides and 

Tonga; an immature but typical specimen recovered 

from drill hole MU-5 on the island of Mujinkarikku, 

Eniw7 etok Atoll, at a depth of lS-21 1/^ feet is Recent in 

age. An immature shell from a depth of 680-690 feet in 

drill hole F-l on Eniwetok seems to represent this variable species. Though still preserving traces of the original color pattern on the spire, the single shell shows 

evidence of wear. The beds from which it is recorded 

are referred to the late Miocene (Tertiary g) ; it may 

have been derived from a higher horizon. Opercula that 

probably represent this species were recovered from 

three drill holes on Eniwetok at depths of 66-340 feet 

and molds from drill hole on Funafuti at depths of 922- 

1,053 feet; age, post-Miocene.

The species has been described from the Pliocene and 

Pleistocene of Okinawa. Living examples have been collected from many parts of the Indo-Pacific, from 

Aldabra Island in the western Indian Ocean through 

Indonesia to Australia, and the Pacific islands from 

Japan to the Tuamotus. It lives along the seaward reef 

edge, on the reef flats, and on lagoonal reefs.
PALEONTOLOGY 49

Turbo (Marmarostoma) setosus Gmelin? 

Plate 7, figure 27

Turbo setosus Gmelin, 1791, Systema naturae, 13th ed., p. 3494. 

Reeve, 1848, Conchologica Iconica, v. 4, pi. 8, fig. 37. 

Pilsbry, 1888, Manual Conchology, v. 10, p. 195. pi. 63, fig. 32. 

Demond, 1957, Pacific Sci., v. 11, p. 387.

An incomplete mold from core piece 276 obtained at 

Funafuti in the Ellice Islands at a depth of 526-546 

feet very probably represents this species. There is no 

indication of a shoulder nor of spines on the ribs such as 

characterize T. argyrostomus Linnaeus, described above; 

the broad ribs are wider than the interspaces, and secondary ribs are present. Figured specimen USNM 

648283 is a cast whose height is 24 mm; it was taken 

from a core loaned by the British Museum; age postMiocene. An incomplete and poorly preserved specimen 

from the post-Miocene Mariana Limestone of Guam 

(TJSGS 21373) may possibly represent the same species.

T. setosus has been reported from many island groups 

in the western Pacific. Hedley (1899a, p. 408) found it 

abundantly on the east side of Funafuti at low water 

on the outer reef.

Turbo (Marmarostoma) crassus Wood 

Plate 8, figures 1, 2

Turbo crassus Wood, 1828, Index Testareologicus supp., pi. 6,

fig. 43.

Reeve, 1848, Conchologica Iconica, v. 4, fig. 10. 

Pilsbry, 1888, Manual Conchology v. 10, p. 194, pi. 47, fig. 20. 

Ostergaard, 1935, B. P. Bishop Mus. Bull. 131, p. 48. 

Turbo canaliculatus Reeve, 1848, Conchologica Iconica, v. 4, 

fig. 27.

Shell large and heavy with broad flat spiral ridges 

separated by narrow shallow grooves. On many shells 

there is a strong spiral keel on the upper part of the 

whorl; above the keel the surface is deeply concave, below the keel a similar concavity, if present, is shallow. 

On the fossil specimens from Tonga, identified as this 

species by Ostergaard, the keel is present but not strongly 

developed.

Measurements of the figured specimen, B. P. Bishop 

Museum, 202976: height 79.3 mm, diameter 63.3 mm.

Occurrence: Two specimens from limestone near 

Houma village, Tongatabu, Tonga at an altitude of 35 

feet; probably Pleistocene. Ostergaard also collected the 

species alive on a wave bench at the foot of a sea cliff 

below the fossil locality. I found it rare on the reefs 

on both sides of the entrance to Suva harbor, Fiji. Recent shells have also been collected from Samoa, the 

Admiralty and Solomon Islands, New Caledonia, and 

northern Australia.

Turbo (Marmarostoma) perlatus Abrard

Turbo (Senectus) perlatus Abrard, 1946, Annales de paleontologie, 

v. 32, p. 50, pi. 4, fig. 11.

As pointed out by the author of the species, T. perlatus 

is closely related to T. chrysostomus Linnaeus and T. 

radiatus Gmelin, differing from these by having welldeveloped beads on the spiral cords. The beads are not 

cut by the axial lamellae and are particularly conspicuous 

on the lower parts of the whorls and on the base. Some 

Recent shells of T. chrysostomus from New Caledonia, 

Palau, and the Philippines show a moderate development of beading on the lower spiral cords, but in no 

specimen was this feature as strongly marked as in 

T. perlatus.

The type, from the upper Miocene of Epi, New 

Hebrides, is probably a young shell. The species has not 

been found in the Miocene or in younger beds elsewhere 

in the islands.

Turbo (Marmarostoma) sp. A 

Plate 8, figures 3, 4

Turbo sp. a Mansfield, 1926, Carnegie Inst. Washington,Pub. 344,

p. 88, pi. 3, fig. 2. 

Turbo sp. b Mansfield, 1926, Carnegie Inst. Washington Pub. 344,

p. 88, pi. 3, fig. 3a, 3b. 

Turbo (Ocana) cf. gruneri Philippi, Ladd, 1935, B. P. Bishop

Mus. Bull. 119, p. 204, pi. 35, figs. 4, 5.

Examination of additional material has shown that 

this strongly ribbed form should be placed in Marmarostoma. On the middle and upper parts of the whorls, 

large ribs alternate with small ribs, and on the base, the 

ribs are subequal in size. All ribs are beaded, those on 

the base and the upper parts of the whorls most conspicuously so.

Occurrence: Numerous molds from stations 160, 295 

(figured specimen, B. P. Bishop Mus., geology No. 1228), 

and 297, Viti Levu, Fiji; age, probably early Miocene 

(Tertiary/).

Genus CYNISCA H. and A. Adams 

H. and A. Adams, 1854, Genera Recent Mollusca, v. 1, p. 406.

Type (by original designation): C. granulata A. 

Adams Delphinula granulosa [Dunker ms.] Krauss. 

Recent, off South Africa.

Cynisca pacifica Ladd, n. sp.

Plate 8, figures 5-7

Small, depressed-turbinate, thick; sutures channeled; 

umbilicus moderately wide, deep; aperture circular, 

faintly lirate within; upper edge of outer lip extended 

onto base of penultimate whorl. Sculpture consisting of 

strong spiral ribs all of which are made granulose by
50 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

axial lines; the peripheral rib and the three above it are 

larger than the five ribs on the base; of the basal ribs 

the two next to the umbilicus are more strongly beaded 

than the others.

Measurements of the holotype, only specimen, USNM 

648284: height 4.1 mm, diameter 4.5 mm.

The Miocene shell from Eniwetok appears to be the 

only known fossil occurrence. At least six species have 

been referred to Cynisca and all were collected from the 

seas off South Africa the extreme western edge of the 

Indo-Pacific region. C. pacifica is very closely related 

to the type C. granulosa and to four other species, the 

chief differences being in sculpture. C. pacifica lias 

fewer ribs than the type C. granulosa Krauss; the beading of the ribs is not restricted to the upper ribs as in 

that species, and the apertural lirae are less well developed. C. pacifica appears to be most closely related to 

C. forticostata Smith, but that species has only seven 

spiral ribs. The three species named by Bartsch (1915, 

p. 163-166) C. gloriosa, C. alfredensis, and C. africana 

are based on worn beach shells, and the apertural 

features are obscure or wanting. C. gloriosa bears 11 

ribs, C. alfredensis 7 ribs, and C. afncana 8 ribs. On 

none of these three species is the beading developed on 

all ribs as in C. pacifica.

Occurrence: Drill hole E-l on Eniwetok at a depth 

of 1,000-1,010 feet; age early Miocene (Tertiary /).

Genus LEPTOTHYRA Pease

Pease, 1869, Am. Jour. Conchology, v. 5, p. 70.

Type (by monotypy). Leptothyra costata Pease. Recent, Hawaii.

Leptothyra maculosa (Pease)

Plate 8, figure? 8-13

Collonia maculosa Pease, 1868, Am. Jour. 'Conchology, v. 4. p. 91,

pi. 11, fig. 1. 

Leptothyra maculosa (Pease), Pilsbry, 1888, Manual Conchology

10, p. 256, pi. 57, fig. 60.

Shell minute, nacreous within; apex blunt, umbilicus 

narrow, aperture circular; edge of outer lip thin, basal 

edge of inner lip reflected outward; sculpture consisting 

of three strong primary spiral ribs, with secondary 

spirals between and below; uppermost of primary spirals, 

spiral nearest the suture, and one next to umbilicus 

beaded. Each of the primary ribs, and in some specimens, 

the basal ribs, spotted at regular intervals with reddish 

brown.

Measurements of the figured specimen (E-l, Eniwetok, 

40-45 ft), USNM 648305: height 1.7 mm, diameter 

1.6 mm.

Occurrence: The species is common in the post-Miocene parts of several holes on Eniwetok and Bikini

Atolls. The shells are so characteristically marked that 

well-preserved specimens may be recognized with ease. 

The globular shells are so small and so light that they 

circulate freely in drilling mud, and occurrences of white 

glistening shells among buff-colored Tertiary fossils are 

not to be trusted. Some of the fossil occurrences, however, 

are preserved as are other Tertiary shells, and there is no 

reason to question the depths. A few of these fossils 

retain faint traces of original color. Unquestioned fossils 

were found in beds referred to Tertiary / and g, the 

maximum depth being 830-842 feet in hole K-1B on 

Eniwetok. The species also is abundant in the Miocene 

Suva Formation (Tertiary /) on Viti Levu (sta. 160). 

The Fijian shells are somewhat larger than those from 

the Marshall Islands and are badly worn, but there is 

little doubt that they represent the same species. Rare 

specimens were also found in the limestone of Tongatabu, 

Tonga (B. P. Bishop Mus., cat. 202980; sta. 3), probably Pleistocene, and in the Recent sediments drilled on 

Funafuti at depths of 65 and 70 feet.

The Recent shell was originally described from the 

Tuamotu [Paumotu] Islands. It has also been collected 

in Hawaii and is common in the northern Marshalls.

Leptothyra inepta (Gould) 

Plate 8, figures 14-22

Monilea inepta Could. 1861, Boston Soc. Nat. History Proc., v.

8, p. 16.

Pilsbry, 1889, Manual Conchology, v. 11, p. 254. 

Johnsor, 1964, U.S. Natl. Mus. Bull. 239, p. 91, pi. 4, fig. 2.

Minute, turreted; apex flattened or slightly depressed. 

Body whorl divided into three subequal parts by two 

spiral angulations; uppermost part flattened, middle 

section (between two angulations) gently convex, lowest 

part (base) convex. Suture impressed, aperture subcircular, outer lip thin, inner lip callused and extended 

below; umbilicus moderately wide, plicate. Sculpture 

consisting of about 20 strong spiral ribs, those at the 

angulations being larger than the others, except the rib 

encircling the umbilicus which is large and coarsely 

beaded; ribs on penultimate whorl beaded; on the base, 

small secondary ribs developed between some of the primary ribs. On the holotype (USNM 1372), axial bands 

of reddish brown cross the upper part of the whorls and 

near the aperture there are larger areas of pink; several 

of the fossils preserve remnants of this color pattern.

Measurements of the figured specimen (Mu-4; Eniwetok, 40y2-41 ft), USNM 648306: height 2.8 mm, 

diameter 2.8 mm. Gould's type, USNM 1372 (pi. 8, figs. 

19-22) measures: height 2.3 mm, diameter 2.5 mm.

The two angulations that enclose a nearly flat peripheral area particularly characterize this species.
PALEONTOLOGY 51

Occurrence: Nine specimens from several drill holes 

at depths above 80 feet on Eniwetok Atoll; age, Recent. 

Gould's Recent type was collected at Kagoshima, Japan, 

in sand under 5 feet of water.

Leptothyra harlani Ladd, n. sp. 

Plate 9, figures 1-3

Minute; spire low, turreted; apex depressed; body 

whorl with inconspicuous shoulder; suture impressed; 

aperture subcircular, outer lip thin, callus of inner lip 

extended below; umbilicus wide and deep. Sculpture consisting of spiral ribs of which three or four near the 

periphery are a little larger than the others; above and 

below peripheral zone, ribs beaded by axial striae; a 

coarse puckered rib surrounds the umbilicus. Well-preserved specimens retain traces of broad axial bands of 

brown color.

Measurements of the holotype (K-1B, Eniwetok, 

663-674 ft), USNM 648307: height 1.9 mm, diameter 

2.5 mm.

Resembles L. inepta but has a lower spire, is less 

strongly shouldered, and is less flattened around the 

periphery.

Occurrence: Eight specimens from drill holes E-l and 

K-1B on Eniwetok Atoll at depths of 642-950 feet; age, 

Miocene (Tertiary f-g). A single specimen from drill 

hole 2B on Bikini at depth of 820-831 feet (Tertiary g) 

may represent the same species.

Leptothyra aff. L. laeta Montrouzier 

Plate 9, figures 4-6

Small, slightly turreted; apex flattened, shell thick; 

body whorl with inconspicuous shoulder; outer lip thickened inside, its upper edge descending sharply at the 

aperture; suture impressed; aperture subcircular, strongly 

oblique; inner lip thickened below at termination of 

wide puckered rib surrounding the deep umbilicus. 

Sculpture consisting of numerous spiral ribs; near the 

periphery large ribs alternate with smaller ones; above 

the shoulder on early whorls the ribs are conspicuously 

beaded; ribs on base weakly beaded. Holotype and one 

other specimen retain faint traces of axial bands of 

brown color.

Measurements of the figured specimen (K-1B, Eniwetok, 957-968 ft), USNM 648312: height 2.9 mm, 

diameter 3.2 mm.

The four fossil specimens differ from Recent examples 

of L. laeta by having an inconspicuous shoulder; they 

are smaller than the Recent shells and may be immature; this would account for the fact that the columella 

is not excavated next to the umbilicus and for the absence of well-developed crenulations within the aperture.

L. laeta has been reported from Australia, New Caledonia, Fiji, and the Solomon Islands (Pilsbry, 1888, p. 

258); Hedley (1899a, p. 408) found the shells common 

on the lagoon beach at Funafuti.

Occurrence: Four specimens from drill holes E-l and 

K-1B on Eniwetok Atoll at depths of 957-1,985 feet; 

age, early Miocene (Tertiary e-f) ; a single specimen 

from hole 2B on Bikini at 1,902-1,913 feet (Tertiary e) 

may represent the same species.

Leptothyra aff. L. Candida (Pease) 

Plate 9, figures 7-9

Minute, globose; whorls inflated; suture impressed, 

descending slightly at aperture; aperture circular, outer 

lip thin, inner lip expanded below; umbilicus narrow, 

plicate. Sculpture consisting of about 10 spiral ribs, 4 

of which on the broad periphery are larger than the 

others; fine secondary ribs are discernible under magnification; ribs near the suture and those on the base are 

beaded.

Measurements of the figured specimen (drill hole BO2-1, depth 7 inches), USNM 648308: height 1.7 mm, 

diameter 2.2 mm.

L. aff. Candida appears to be characterized particularly by the uniform rate of curvature of its inflated 

whorls and the absence of a shoulder or strong peripheral 

rib. The ribs of the specimens from Eniwetok are more 

conspicuously beaded than ribs of shells from Hawaii.

Occurrence: Two specimens from Eniwetok Atoll: in 

drill hole BO-2-1 on island of Bogallua, at a depth of 

only 7 inches and in drill hole E-l, Parry Island at 

depth of 40-45 feet; age, Recent. The Eniwetok specimens appear to be closely related to L. Candida from 

Hawaii, the area from which the shells described by 

Pease (1860, p. 436, as Collonial Candida} were obtained, 

tained.

Leptothyra balnearii Pilsbry 

Plate 9, figures 10-12

Leptothyra balnearii Pilsbry, 1920, Acad. Nat. Sci. Philadelphia 

Proc., v. 72, p. 378, fig. 14.

Minute, globose, wider than high; apex flattened, perforate, thick; aperture oblique, outer lip thin, inner lip 

expanded below. Sculpture consisting of smooth spiral 

ribs of which three or four on the gently rounded periphery are larger than the others; above there is a single 

beaded rib and, next to the suture, a wide beaded band; 

on the base three or four slightly beaded riblets and a 

larger beaded rib spirals into the umbilicus. On some 

shells, secondary threads are developed between the 

peripheral ribs. Well-preserved fossil specimens, like some
52 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Recent shells, are red except for the first whorl and the 

umbilical area, which are colorless. Two older fossils 

retain traces of brown spots on the peripheral ribs of the 

body whorl, a pattern likewise found on the shells of 

living specimens.

Measurements of the figured specimen (drill hole F-l, 

Eniwetok Atoll, depth 55-60 ft), USNM 648309: height 

0.7 mm, diameter 1.0 mm.

Occurrence: Represented by a total of seven specimens 

from five drill holes on Eniwetok Atoll. Five specimens 

from depths of 20-70 feet are Recent; one from a depth 

of 620-630 feet is late Miocene (Tertiary g) ; the oldest 

from a depth of 904-916 feet is early Miocene (Tertiary /).

Pilsbry's types were collected in Hawaii, off Waikiki 

at a depth of 25-50 fathoms. Shells have also been collected at other localities on Oahu and on Molokai and 

Kauai.

The Marshall Island fossils are smaller than the 

Hawaiian shells but appear identical in all other features. The species is similar to the type species L. costata 

Pease, a Recent species from Hawaii that has a different 

color pattern; L. cotata also differs by having a thicker 

outer lip.

Leptothyra wellsi Ladd, n. sp.

Plate 9, figures 13-15

Minute; spire flat or nearly so, umbilicus wide and 

deep; aperture oblique, outer lip thin, inner lip expanded 

below. Sculpture consisting of three or four smooth spiral 

ribs in the peripheral zone and smaller beaded ribs immediately above and below; a large rib that borders the 

umbilicus and two others that spiral into it are conspicuously beaded. The holotype, paratype B, and several other well-preserved specimens retain traces of 

radial brown bands on the crests of the ribs.

Measurements of the types: Holotype (F-l, Eniwetok, 

690-700 ft), USNM 648310: height 0.9 mm, diameter 

1.2 mm; paratype A (E-l, Eniwetok, 770-780 ft), 

USNM 648311, and paratype B (Viti Levu, Fiji, sta. 

160), USNM 648406 have the same measurements as the 

holotype.

L. wellsi resembles L. balnearii that occurs most commonly in younger beds but has a lower spire and a much 

wider umbilicus. In two samples in which the species 

occur together they can be differentiated without difficulty.

Occurrence: More than 50 specimens from 30 levels 

in 3 drill holes on Eniwetok Atoll at a depth of 230- 

1,993 feet; 3 specimens from 2 deep holes on Bikini 

Atoll at depth of 862-884 feet; abundant in the Suva

Formation at station 160 on Viti Levu, Fiji. Age, Recent or Pleistocene to early Miocene (Tertiary e).

Leptothyra glareosa marshallensis Ladd, n. subsp. 

Plate 9, figures 16-20

Small, globose, thick; body whorl inflated but showing 

a suggestion of a shoulder; shoulder more prominent on 

earlier whorls, giving the shell a turreted appearance; 

suture impressed, descending at aperture; apex flattened; 

aperture circular, inner lip expanded below; umbilicus 

narrow and deep, partially filled by a low heavy beaded 

funicle. Sculpture consisting of fine close-set spiral ribs 

(about 24 on body whorl), the rib at the shoulder slightly 

larger than the others; ribs on earlier whorls and those 

near umbilicus beaded by axial lines. Colored pale brown 

or reddish brown with indistinct darker axial bands; 

apex and umbilical area white. Operculum: inside convex, warped, multispiral; outside with deep excentric 

pit with beaded margin, partially surrounded by five 

concentric flaring ridges.

Measurements of the holotype, a Recent shell from 

Bikini, USNM 648313: height 2.3 mm, diameter 2.6 mm. 

Operculum of paratype, a Recent shell occurring with 

holotype, USNM 648314: maximum diameter 1.1 mm, 

minimum diameter 0.9 mm.

Recent shells and fossils from the Marshall Islands 

have been compared with the types of Gould's Monilea 

glareosa (USNM 971 and 24227), with Recent shells collected in the Ryukyu (Loo Choo) Islands, and with 

shells from Japan and the Bonin Islands. The Marshall 

Island specimens, both Recent and fossil, differ only in 

the possession of a shoulder that is marked on the body 

whorl by an enlarged spiral rib. The species described 

by Pease as Collonia granulosa (1868, p. 92) and referred by Pilsbry to Leptothyra (1888, p. 259, pi. 57, 

fig. 59) appears to be identical with Gould's Monilea 

glareosa. Pease's type was collected on Ponape in the 

Caroline Islands, not far from the Marshalls, but it does 

not possess a distinct shoulder. A shoulder like that on 

the Marshall Islands specimens is found on Recent shells 

from New Caledonia (Acad. Nat. Sci. Philadelphia 

271717).

Occurrence: Abundant in the Marshall Islands today. Holotype, a Recent shell dredged alive from a 

depth of 30 fathoms in Bikini lagoon. Six fossil specimens from three drill holes on Bikini were recovered 

from a depth of 110-295 feet; probable age, Recent to 

Pliocene (Tertiary h). Also present in numerous drill 

holes on Eniwetok Atoll at depths of 1-890 feet; age, 

Recent and Miocene (Tertiary / and g.). Many opercula 

representing this species were recovered from several
PALEONTOLOGY 53

Eniwetok drill holes from near the surface to 1,777 feet; 

age, Recent to Tertiary e.

Leptothyra picta (Pease) 

Plate 9, figures 21-23

Collonia picta Pease, 1868, Am. Jour. Conchology 4, p. 91, pi. 11,

fig. 1. 

Leptothyra picta (Pease), Pilsbry, 1888, Manual Conchology, v.

10, p. 256, pi. 69, fig. 35.

Minute, strongly turreted; apex flat; suture impressed, 

descending abruptly at aperture; aperture circular, outer 

lip thin, inner lip thick and broadly expanded below; 

umbilicus exceedingly narrow, bordered by a broad 

beaded rib. Sculpture consisting of about 10 strong spiral 

ribs alternating fairly regularly with weak secondary 

ribs. Strong ribs at the suture, the shoulder, near the 

upper margin of the base, and next to the umbilicus are 

larger than the others; ribs on earlier whorls, those 

bordering the suture and near umbilicus are beaded.

Measurements of the figured specimen (E-l, 35-40 

m, USNM 648315: height 2.1 mm, diameter 2.3 mm.

Occurrence: Many specimens from drill hole E-l on 

Parry Island, Eniwetok Atoll, at depth of 30-110 feet; 

age, Recent.

Originally described as a Recent shell from the Tuamotu Islands; later, reported from Tahiti, Society Islands; rare in the northern Marshalls. The fossils agree 

in all essential features with the types of L. picta (Acad. 

Nat. Sci. Philadelphia 38416), but the turreting in the 

fossils is a little stronger, particularly the strength of 

the strong spiral rib at the upper edge of the aperture.

Leptothyra emenana Ladd, n. sp. 

Plate 9, figures 24-26

Small; spire low to medium, turreted; apex flat: suture 

impressed, descending at aperture; aperture subcircular, 

oblique; outer lip thin, inner lip thickened and on some 

specimens expanded below; umbilicus narrow, bordered 

by a large conspicuously beaded spiral rib. Sculpture 

variable, consisting of about 15 spiral ribs, the 4 that 

occur on the gently convex peripheral band being larger 

than those above and below; secondary spirals may alternate with larger spirals above the peripheral band; below the peripheral band the spirals are subequal in size, 

all being smaller than the rib next to the umbilicus; all 

spiral ribs except the lowest three of the peripheral band 

are more or less beaded. Well-preserved shells show 

traces of broad radial brown bandy.

Measurements of the holotype (drill hole F-l, Eniwetok, depth 940-950 ft), USNM 648316: height 2.7 mm, 

diameter 2.8 mm. Paratype (F-l, 880-890 ft), USNM 

.648317: height 2.3 mm, diameter 2.6 mm.

This somewhat variable species is characterized particularly by the nearly flat peripheral band bearing four 

strong spiral ribs.

Occurrence: In all deep holes on Eniwetok and Bikini. 

On Eniwetok, 40 specimens were recovered from 26 

samples. Most of these were in beds referred to the Miocene (Tertiary e-g) ; rare in beds that probably are 

Pliocene (Tertiary h) ; on Bikini a total of six specimens 

were recovered from the Miocene (Tertiary e and g).

Leptothyra sp. A 

Plate 9, figures 27-29

Minute; spire medium, apex flattened; aperture subcircular; outer lip thin, inner lip slightly thickened, expanded below; umbilicus narrow, deep, puckered by a 

wide riblike elevation. Sculpture consisting of spiral 

ribs that are beaded and scalloped by axial lines; on the 

body whorl four ribs, larger than those above and below, 

form a peripheral band; three somewhat smaller spirals 

lie above the band and five obscure spirals lie below it; 

under magnification, fine threads can be seen between 

the ribs of the peripheral band and between those that 

lie above it; the uppermost of the peripheral ribs and the 

third one in the series are extended as a frill that is scalloped on part of the body whorl and on earlier whorls. 

Body whorl retains traces of broad radial bands of brown.

Measurements of the figured specimen, USNM 648318: 

height 2.0 mm, diameter 2.4 mm.

The single specimen described may represent an undescribed species, but its thin fluted outer lip indicates 

immaturity, and a specific name is withheld. The whiteness of the shell with its traces of brown suggests that 

the shell may have been derived from a higher level. It 

appears to be most closely related to L. emenana, differing chiefly by having scalloped peripheral ribs.

Occurrence: Drill hole K-1B, Eniwetok Atoll, at a 

depth of 642-653 feet; age, late Miocene (Tertiary g).

Family PHASIANELLIDAE 

Genus PHASIANELLA Lamarck 

Lamarck, 1804, Annales Mus. Histoire Naturelle, v. 4, p. 295.

Type (by ruling of Comm. Zool. Nomenclature, Zool. 

Nomenclature Bull., 1962, v. 19, p. 140): Buccinum 

austrae Gmelin. Recent, south coast of Australia.

Phasianella sp. 

Plate 10, figures 10, 11

Eight specimens of phasianellid opercula were recoverede from Miocene beds in three drill holes on Eniwetok 

and three from hole 2A on Bikini. Six of the opercula 

from Eniwetok occur in sediments referred to Tertiary 

g (642-898 ft); the remaining two, both incomplete, came
54 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

from a slightly lower level, 873-884 feet, in the top of 

the Tertiary / section. The Bikini specimens are from 

beds referred to Tertiary / (877-936 ft). Two opercula 

from the Tertiary marls of the Suva Formation (sta. 

FB-20) on Viti Levu, Fiji, appear to be identical with 

the Marshall Island specimens.

Operculum convex externally with a broad longitudinal off-center bulge, surface polished; internal surface 

concave with excentric paucispiral nucleus, surface 

striate. The striae meet the margin at right angles.

Measurements of the figured specimen (K-1B, Eniwetok, 841-853 ft), USNM 648327: maximum diameter 

3.4 mm, minimum diameter 2.5 mm, convexity 1.1 mm.

Most of the opercula are too large to be assigned to 

any of the phasianellids recognized from the drill holes. 

Their size suggests that they belonged to shells having 

a height of at least 12 mm.

Genus GABRIELONA Iredale

Iredale, 1917, Malacological Soc. London Proc., v. 12, p. 327.

Type (by monotypy): Phasianella nepeanensis Gatliff and Gabriel. Recent, Australia.

Gabrielona raunana Ladd, n. sp. 

Plate 10, figures 1 5

Small, globose, thin; spire low; smooth whorl of protoconch followed by about three rapidly increasing 

sculptured whorls; aperture broadly ovate, peristome 

thin, inner lip expanded below; umbilicus narrow; sculpture consisting of axial riblets that are coarser on the 

upper part of each whorl and near the umbilicus than 

elsewhere. Operculum (preserved in place in holotype) 

is paucispiral and gently concave externally, this face 

being marked on the last volution by an outer band of 

spiral ridges inside which is a wider band of curved 

axial ridges. Operculum of paratype C, USNM 648322, 

measures: maximum diameter 0.8 mm, minimum diameter 0.5 mm; the interior face is flattened by a shallow 

spiral depression and a rounded outer edge. Well-preserved shells have a pink tinge with irregular brown axial 

streaks extending downward from the suture; on paratype B, similar markings occur on the lower part of the 

body whorl.

Measurements of the holotype (F-l, Eniwetok, 20-45 

ft), USNM 648319: height 1.4 mm, diameter 1.4 mm. 

Paratype A (F-l, Eniwetok, 20-45 ft), USNM 648320: 

height 2.0 mm, diameter 1.9 mm. Paratype B (E-l, Eniwetok, 40-45 ft), USNM 648321: height 1.5 mm, diameter 1.5 mm.

Differs from the type species, G. nepeanensis (Gatliff 

and Gabriel) by having the inner lip expanded below.

Occurrence: Thirty-four specimens recovered from 

shallow depths (20-110 ft) in five drill holes on Eniwetok Atoll; age, Recent. A single specimen from hole 

E-l at a depth of 1,865-1,895 feet (Tertiary e) shows 

evidence of wear and was probably derived from a higher 

horizon. Not represented in the extensive Recent collections made on Eniwetok and nearby atolls.

Genus TRICOLIA Risso

RisHo, Histoire naturelle des principales productions de 1'Europe 

Meridionale, v. 4, p. 122.

Type (by subsequent designation, Gray, 1897, Zool. 

Soc. London Proc., pt. 15, p. 144): Turbo pullus Linnaeus. 

Recent, European seas.

Subgenus HILDA Pilsbry

Pilsbry, 1917, Acad. Nat. Sci. Philadelphia Proc., p. 207.

Type (by original designation): Phasianella thaanumi 

Pilsbry. Recent, Hawaii.

Tricolia (Hiloa) variabilis (Pease)

Plate 10, figures 6, 7

Collonia variabilis Pease, 1860, Zool. Soc. London Proc., p. 436. 

Phasianella variabilis (Pease), Pilsbry, 1888, Manual Conchology,

v. 10, p. 176, pi. 39a, figs. 21, 22. 

Pilsbry, 1917, Acad. Nat. Sci. Philadelphia Proc., p. 207.

Small, thin, ovate; about four whorls, ventricose; su- 

.ture deeply impressed; aperture subcircular, inner lip 

callused, slightly extended below and with a deep groove 

behind it in the umbilical region. Sculpture consisting 

of fine oblique axial lines; close-set spiral striae visible 

under magnification on some specimens. Specimens retaining traces of color show nearly continuous close-set 

brownish-red spiral lines or lines of dots and may show 

short thick red axial lines immediately below the suture; 

axial lines may be bunched in groups of three or four.

Measurements of the figured specimens (pi. 10, fig. 

6; E-l, Eniwetok, 30-40 ft), USNM 648323: height 

1.4 mm, diameter 1.1 mm; (pi. 10, fig. 7; E-l, Eniwetok, 

40-45 ft), USNM 648324: height 1.9 mm, width 1.3 mm.

Occurrence: Common in many drill holes on Eniwetok Atoll from near the surface to a depth of 852 feet 

(Recent to upper Miocene, Tertiary g) ; four specimens 

from hole 2B on Bikini at depth of 1,482-1,870 feet 

(lower Miocene, Tertiary e). Recent shells were collected from Bikini, Eniwetok, Rongerik, and Rongelap 

Atolls. The fossils and the Recent Marshall Island shells 

are smaller on the average than the shells described by 

Pease from Hawaii, and they have a somewhat different 

color pattern. The pattern on the Hawaiian shells, as 

Pease's name suggests, is exceedingly variable, but on 

most shells the axial bands seem to dominate over the
PALEONTOLOGY 55

spiral markings. Some Recent Hawaiian shells, however, 

exhibit close-set lines of red dots, a pattern that is 

strongly suggestive of that shown by the Marshall Island 

material.

Tricolia (Hiloa) sp. A 

Plate 10, figure 9

Minute, thin, ovate; about three smooth ventricose 

whorls; suture impressed; aperture subcircular; inner 

lip expanded below with a shallow groove behind it in 

the umbilical region.

Measurements of the figured specimen, USNM 648326: 

height 0.9 mm, diameter 0.7 mm.

Tricolia sp. A should, perhaps, be placed with T. variabilis (Pease), but it has fewer whorls, a less prominent 

groove in the umbilical region, and a more expanded 

basal inner lip. The single Tongan specimen retains 

traces of spiral lines of short red dashes on body whorl.

Occurrence: Three specimens from the Miocene (Tertiary /) Suva Formation on Viti Levu, Fiji (sta. 160); 

a single specimen from Tongatabu in Tonga (B. P. 

Bishop Mus., cat. 202976) may represent this species; 

age, probably Pleistocene.

Family NERITOPSIDAE 

Genus NERITOPSIS Grateloup

Grateloup, 1832, Soc. Linn. Bordeaux Actes. v. 5, p. 129.

Subgenus NERITOPSIS s.s.

Type (by monotypyl: Neritopsis monilijormis Grateloup. Miocene, southern France.

Neritopsis (Neritopsis) radula (Linnaeus) 

Plate 10, figures 12-14

Nerita radula Linnaeus, 1758, Systema naturae, 10th ed., p. 777. 

Neritopsis radula (Linnaeus), Gray, 1899, Zoology, "Blossom," p.

138. 

Xcritopsix radula (Linnaeus), now subspecies?, Ladd, 1934, B. P.

Bishop Mus. Bull. 119, p. 207, pi. 35, fig. 13. 

Neritopsis radula (Linnaeus). Ladd, 1945, B. P. Bishop Mus. Bull.

181, p. 355, pi. 50, fig. L.

N. radula has been reported from the Recent fauna in 

many parts of the Indo-Pacific region (Marshall, Ellice 

and Loyalty Islands, New Caledonia, Java, and Mauritius) and has previously been found in the Tertiary and 

younger rocks of Fiji (sta. 160, Viti Levu; stas. L-24, 

L-35, L-45, L-46, Fulanga; L-120, Ongea; HOB, HOC, 

Vanua Mbalavu). Single typical specimens were collected on Guam from three localities (USGS 20534, 

20614, and 208691 in the Mariana Limestone. In Palau 

the species was found in the Palau Limestone on Urukthapel (USGS 18322> and on Saipan in the Miocene 

Tagpochau Limestone (USGS 17723) ; a mold that may 

represent N. radula was recovered from the Quaternary

beds drilled on Funafuti (core 563A, depth 1,015-1,025 

ft).

In the Marshall Island drill holes, small unbroken 

specimens were recovered from cuttings from Bikini (2A, 

depth 284-290 ft) and from Eniwetok at depths ranging 

from 20 to 1,715 feet. Three of the six Eniwetok specimens are from the Miocene (two from Tertiary / and 

one from Tertiary e ). The small Tertiary specimens, like 

the large specimen from the upper Tertiary of Viti Levu 

(Ladd and others, 19341, appears to be more coarsely 

sculptured than most Recent shells, but the differences 

are not great and hardly seem to justify the naming of a 

new subspecies.

Measurements of the figured specimen (F-l, Eniwetok, 

960-970 ft), USNM 648238: height 2.8 mm, diameter 

2.6 mm.

Family NERITIDAE 

Genus NERITA Linnaeus

Linnaeus, 1758, Systema naturae, 10th ed., p. 776.

Type (by subsequent designation, Montfort, 1810, 

Conchyliologie systematique 2, p. 347): Nerita peloronta 

Linnaeus. Recent, West Indies.

Subgenus AMPHINERITA Martens

Martens, 1887, Systematische Conchylien-Cabinet, v. 2, pt. 11, 

p. 9.

Type (by subsequent designation, Baker, 1923, Acad. 

Nat. Sci. Philadelphia Proc., v. 75, p. 164): Nerita 

umlaasiana Krauss. Recent, Africa.

Nerita (Amphinerita) insculpta Recluz 

Plate 10, figures 15, 16

Nerita insculpta Recluz, 1841, Rev. Zool., Soc. Cuvierienne, p. 152.

Small, stout; spire low; sculpture consisting of 10 

broadly rounded spiral ribs separated by narrow interspaces and crossed by fine growth lines; outer lip 

crenulated by spiral ribs; inner lip and columellar deck 

smooth. Traces of dark spots are preserved along several 

of the spiral ribs.

Measurements of the figured specimen, USNM 648332: 

height 4.6 mm, diameter 5.3 mm.

Occurrence: Eniwetok Atoll, drill hole F-l, at depths 

of 680-690 feet and 690-700 feet (figured specimen); 

late Miocene, Tertiary g.

The two fossil specimens are smaller than Recent 

shells from the same area but probably are immature. 

They have fewer and coarser ribs than most Recent 

shells. The type specimen is a Recent shell from Timor; 

Hedley (1899a, p. 410) found the species living in the 

lagoon at Funafuti.
56 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Nerita (Amphinerita) aff. N. polita Linnaeus 

Plate 10, figures 17, 18

Small, globose, thick, highly polished; spire low, suture 

distinct; aperture polished within, outer lip thick, descending at the aperture; columellar deck convex, white, 

bounded posteriorly by a shallow groove; inner lip feebly 

dentate. Sculpture consisting of fine growth lines that 

may be prominent on the upper part of the body whorl 

close to the suture.

Measurements of the figured specimen (F-l, Eniwetok, 

930-940 ft), USNM 648333: height 3.4 mm, diameter 

4.1 mm.

The fossils resemble the Recent species N. polita 

Linnaeus (Tryon, 1888, p. 30, pi. 6, figs. 7-11, pi. 7, figs. 

12-23) that occurs in abundance in the Marshall Islands 

and in many other parts of the Indo-Pacific region. The 

fossil differs in that its outer lip descends at the aperture, 

and its columellar callus is set off by a shallow but distinct groove.

Occurrence: Eight specimens lone immature) from 

three deep holes on Eniwetok Atoll at depth of 830-978 

feet; age, Miocene (Tertiary j-g}.

Subgenus RITENA Gray

Gray, 1858, Zool. Soc. London Proc., pt. 26, p. 92.

Type (by original designation) Nerita plicata Linnaeus. Recent, Indo-Pacific seas.

Nerita (Ritena) palauensis Ladd, n. sp. 

Plate 10, figure 19

Shell medium sized, spire low; columellar deck 

irregularly tuberculated, inner lip with two large teeth; 

edge of outer lip thin, dentate within; sculpture of body 

whorl 14 or more heavy flattened ribs separated by narrower interspaces.

Holoti/pe: USNM 648330: height 17.3 mm, diameter 

20.9 mm.

N. palauensis is related to the Recent N. lineata 

Gmelin iRippingale and McMichael, 1961, p. 41, pi. 3, 

fig. 7) from Indonesia and Australia, but the Recent 

shells have thinner and more numerous ribs and a smooth 

columellar deck.

Occurrence: Holotype and one other specimen from 

the breccia at the base of the Palau Limestone on Auluptagel Island (USGS 23642), Palau; late Miocene (Tertiary fyl; two other specimen^ from the same horizon 

nearby, USGS 17715 and 21290.

Nerita (Ritena) aff. N. undata Linnaeus

Several clusters of external molds of a large ribbed 

neritid similar in general features to the variable and 

widespread Recent N. undata were collected in 1899 by

the U.S.F.C. steamer Albatross from Alofi on the western 

side of the island of Niue, an island in Tonga lying to 

the east of the main island group. The samples were collected from the third terrace; age, probably Pleistocene. 

On some of the fossils the ribs are beaded by axial lines, a 

feature not shown by N. undata.

N. undata has also been reported from the upper 

Miocene of Java.

Subgenus THELIOSTYLA Mbrch

Morch, 1852, Catalogus Conchyliorum D. A. d'Aguirra et Galdea, 

Comes de Yoldi, pt. 1, p. 167.

Type (by subsequent designation, Kobelt, 1879, 

Illustrirtes Conchylienbuch 2, p. 147) : Nerita albicilla 

Linnaeus. Recent, Indo-Pacific.

Nerita (Theliostyla) cf. N. semirugosa Recluz

Nerita (Theliostyla) semirugosa Recluz, Ladd, 1945, B. P. Bishop 

Mus. Bull. 181, p. 355, pi. 50, fig. M.

Three incomplete and partly crushed specimens from 

stations HOB and HOC, Ndalithoni Limestone; age, 

probably Pliocene (Tertiary h\, Vanua Mbalavu, Lau, 

Fiji may be identical with the Recent species (Tryon, 

1888, p. 20, pi. 3, figs. 41-43). No additional material 

collected.

Nerita (Theliostyla) sp. A 

Plate 10, figures 20, 21

Nerita (Theliostylal) sp. Ladd. 1934, B. P. Bishop Mus. Bull. 

119, p. 208, pi. 35, figs. 14, 15.

Shell small, subglobose, thick; spire low; columellar 

deck slightly concave and covered with circular and oval 

pustules; inner lip bearing rounded widely spaced denticles. Outer lip incomplete but apparently dentate 

within, bordered by a narrow grove and channeled posteriorly at its junction with the parietal wall. Surface of 

body whorl somewhat worn but showing traces of low 

close-set rounded spiral ribs and fine wavy lines of 

growth.

Measurements of single incomplete specimen, B. P. 

Bishop Museum, geology No. 1195: height 11.3 mm, 

diameter 12.8 mm.

This specimen was originally referred questionably to 

Theliostt/la and compared with its type species N. albicilla Linnaeus. Following reexamination and comparison 

with additional Recent material it seems certain that the 

fossil is a Theliostyla and that it is similar to but not 

identical with Ar. albicilla. The most important difference between the fossil and the Recent shells is in the 

spiral ribs. Those of the fossil are lower and much more 

numerous than those of any specimens of the variable 

and widespread Recent species. The fossil probably
PALEONTOLOGY 57

represents an undescribed species, but better type material should be obtained before it is named.

Occurrence: Viti Levu, Fiji (sta. 59); age, probably 

Miocene.

Nerita (Theliostyla) sp. B 

Plate 10, figure 22

Nerita sp. Ladd, 1945, B. P. Bishop Mus. Bull. 181, p. 356.

Shell large, heavy; spire low; sculpture consisting of 

14 heavy spiral ribs whose upper surfaces are nearly flat 

and whose sides are undercut ; spaces between ribs flattened and slightly wider than ribs; ribs and interspaces 

crossed by numerous fine lines of growth that are slightly 

oblique to axes of ribs; growth lines near aperture especially prominent ; outer lip crenulatecl by the ribs, coarsely 

dentate within; columellar deck pustulose.

Diameter of figured specimen, USNM 648331: 31.0 

mm.

Appears to be closely related to N. e.rui'ia Linnaeus, a 

Recent Tndo-Pacific species, but that species shows a 

small median rib in each depression between the major 

ribs. The fossil may represent an undescribed species, 

but the single specimen is incomplete and the apertural 

features are somewhat obscured by recrystallization.

Occurrence: Single specimen from the island of Mango, 

Fiji (sta. M2D); age, probably Miocene. Collected by 

J. E. Hoffmeister.

Genus NERITINA Lamarck

Lamarck, 1816, E^ncyclopedie methodique, Histoire naturelle des 

vers, v. 3, pi. 455; Liste p. 11.

Type (by subsequent designation, Children, 1823, 

Lamarck's genera of shells, p. Ill): Neritina pulligera 

{Nerita pulligera Linnaeus I. Recent, fluviatile, India 

and Melanesia.

Subgenus VITTA Morch

Morch, 1852, Catalogus Conchyliorum D. A. d'Aguirra et Galdea. 

Comes de Yoldi, pt. 1, p. 166.

Type (by subsequent designation, Baker, 1923, Acad. 

Nat. Sci. Philadelphia Proc., v. 75, p. 137): Nerita virgin ea Linnaeus. Recent, southern Florida to northern 

South America, estuarine and marine.

Neritina (Vitta) oualaniensis Lesson 

Plate 10, figures 23-25

oiuilanii'nsix Lesson, 1830, Voyage do La 

Zoologie, v. 2, p. 379.

Neritina ulanensis2 Lesson, Tryon, 1888, Manual Conohology, v. 

10, p. 41, pi. 13, figs. 56-68.

- ''Ulan" is an old name for the island of Kusaie in the eastern Carolines. 

Tryon in substituting: ulanensis for Lesson's oualaniensis appears to have 

attempted to correct Lesson's spelling of the type locality.

Shell small, spire moderately elevated, outer lip thin; 

inner lip callusecl, slightly convex, bearing small denticles; color pattern consisting of dark wavy lines interrupted by white triangular areas in spiral series, each 

triangle pointing forward, its sides outlined by a dark 

line.

Measurements of the figured specimens (pi. 10, figs. 

23, 24), USNM 648334: height 6.3 mm, diameter 5.6 mm; 

<pl. 10, fig. 25) USNM 648335: height (incomplete) 5.0 

mm.

Occurrence: Two specimens from the Pliocene and 

Pleistocene of Guam (USGS 20600 and 21377). Recent 

shells Jiave been widely reported in the Indo-Pacific 

region, including Queensland, Australia. The species has 

also been reported from the lower and upper Miocene of 

Java.

Genus CLITHON Montfort

Montfort, 1810, Conchyliologie systematique, v. 2, p. 327.

Type (by original designation): Nerita corona Linnaeus. Recent, rivers of Asia and Indonesia to Melanesia.

Subgenus CLITHON s.s. 

Clithon (Clithon) corona (Linnaeus)

Neritfi corona Linnarus. 1758. Systema naturae, 10th ed., p. 777.

Neritina brevispina Lamarck, 1822, Hist. Nat. Animaux sans 

Vertebres, v. 6, pt, 2.

Theodoxus corona (Linnaeus), Baker, 1923, Acad. Nat. Sci. Philadelphia Proc., v. 75, p. 155.

Theodoxus (Clithon) corona (Linnaeus), Ladd, 1934, B. P. Bishop 

Mus. Bull. 119, p. 208, pi. 35, fig. 16, pi. 36, fig. 1.

Clithon (Clithon) corona (Linnaeus), Ladd, 1965, Malacologia, 

v. 2, p. 191.

A single worn specimen of this widespread and somewhat variable river snail was described and figured by 

Ladd from the Miocene Suva Formation (Tertiary /) of 

station 160, Viti Levu, Fiji. No other fossil examples 

have been collected in the island area.

Genus NERITILIA Martens

Martens in Martini and Chemnitz, 1879, Systematische Conchylien-Cabinet p. 18.

Type (by original designation): Neritina rubida Pease. 

Recent; fresh water, Tahiti.

Neritilia traceyi Ladd 

Plate 10, figures 26, 27

Neritilia traceyi Ladd, 1965, Malacologia, v. 2, p. 191.

Minute, obliquely elliptical, smooth, thick; aperture 

lunate; inner lip convex, its margin edentulous; columellar deck convex, heavily callusecl, posterior margin of 

callus broadly convex.
58 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Measurements uf the holotype, USNM 648336: height

I.9 mm, diameter 2.5 mm.

N. traceyi has the edentulous inner lip that is characteristic of Neritilia, but the lip margin is convex, 

whereas in typical Neritilia it is straight. The inner lip 

of the fossil is more heavily callused than that of N. 

rubida (Pease), the type of the genus, but a callused 

lip comparable to that of the fossil is present on a small 

brackish-water Neritilia found in abundance of J. E. P. 

Morrison near the mouths of a coastal river in New Caledonia. The outer lip of the fossil is worn, and this fact 

explains, in part, the apparent great thickness of the 

shell and the shortness of its elliptical outline.

Occurrence: Holotype (only specimen) from drill hole 

2B, Bikini Atoll at a depth of 2,154-2,165 feet; age, early 

Miocene (Tertiary e).

Genus SMARAGDIA Issel

Issel, 1869, Malacologia del Mare Rosso, p. 212.

Subgenus SMARAGDIA s.s.

Type (by subsequent designation, Kobelt, in Martini 

and Chemnitz, 1879, Systematische Conchylien-Cabinet 

v. 2, p. 246: Nerita viridis Linnaeus, Recent, Mediterranean Sea.

Smaragdia (Smaragdia) jogjacartensis (Martin) 

Plate 10, figures 28-31; plate 11, figures 1, 2

Ncrithtd jogjacarli'iixix Martin. 1916; Die- Altmiocane faunades 

West-Progogebirge.s auf Java, Geol. Reichs-Mus. Leiden 

Samml., v. 2, no. 6, p. 259, pi. 3, figs. 82, 83.

Small; callus thick and broadly convex except near 

base of inner lip where it becomes the lining of a shallow 

depression; inner lip bearing fine denticles that are 

slightly coarser above; outer lip thin. Color pattern consisting of three broad spiral bands made up of close-set 

parallel axial brown lines; lined areas separated by narrow white spiral bands with short stubby extensions.

Measurements of the figured specimens (pi. 10, figs. 

28, 29; Eniwetok drill hole F-l, 830-840 ft) USNM 648- 

337: height 5.2 mm, diameter 5.9 mm; (pi. 10, fig. 30; 

K-1B, 841-853 ft) USNM 648401: height 2.5 mm, 

diameter 2.7 mm; (pi. 10, fig. 31; K-1B, 873-884 ft) 

USNM 648402: height 3.0 mm, diameter 3.6 mm; (pi.

II, figs. 1, 2) ; from Palau (USGS 21308) USNM 648403: 

height 2.6 mm, diameter 3.3 mm.

The color pattern exhibited by S. jogjacartensis, like 

that of most Smaragdias, is variable. The relative 

widths of the clear and shaded bands vary as do the 

lengths and orientation of the secondary branches.

Occurrence: Described originally from the lower Miocene of Java. In samples from 14 intervals in three deep 

holes on Eniwetok Atoll (F-l, 830-960 ft; E-l, 860-

1,130 ft; K-1B, 842-988 ft) but never in great abundance. All the intervals are Miocene (Tertiary e-g) ; 

rare specimens were also found at three localities in the 

marl facies at the base of the late Miocene Palau Limestone in the Goikul area, Babelthuap, Palau.

Smaragdia (Smaragdia) aff. S. rangiana (Recluz) 

Plate 11, figures 3, 4

Small, obliquely elongate; spire low, whorls with a 

well-developed shoulder close to the suture; suture descending sharply at aperture. Columellar deck heavily 

callused above, unevenly depressed below, delimited by 

a groove that deepens along the base; inner lip denticulate, the largest denticles lying immediately above the 

midpoint.

Measurements of the figured specimen, USNM 648338: 

height (incomplete) 3.2 mm, diameter 3.3 mm.

The Palauan fossil closely resembles the variable Recent species that has been reported from many parts of 

the Indo-Pacific area (Tryon, 1888, p. 55, pi. 18, figs. 

89-92), but seems to have a stronger shoulder; no trace 

of color pattern is preserved on the single fossil.

Occurrence: Single incomplete specimen from late Miocene (Tertiary g ) marls at the base of the Palau Limestone near Goikul, Babelthuap Island, Palau (USGS 

21308).

Smaragdia (Smaragdia) colei Ladd, n. sp. 

Plate 11, figures 5-7

Small, obliquely elongate; spire low; body whorl inflated, with obscure shoulder close to suture. Upper 

two-thirds of columellar deck covered by thick pad of 

callus that is separated by a groove from the depressed 

but gently convex lower third; inner lip denticulate, one 

or two teeth near the midpoint larger than the others; 

outer lip thin (broken in most specimens). Color pattern consisting of spiral lines of brown dots. On some 

specimens, including the holotype, lines are arranged in 

bands of three lines each; on other shells (pi. 11, fig. 7) 

the lines of dots cover the entire shell uniformly; on a 

few shells the lines of dots are reduced or entirely 

absent.

Measurements of the holotype (F-l, Eniwetok, 880- 

890 ft), USNM 648339: height 5.6 mm, diameter (outer 

lip incomplete) 5.4 mm. Paratype (F-l, Eniwetok, 830- 

840 ft), USNM 648405: height 3.8 mm, diameter 4.1 mm.

S. colei is characterized particularly by its depressed 

lower columellar deck; in the types and many other 

specimens this deck is sharply set off from the callus 

above; in a few shells the line of demarkation is less 

sharp. The color pattern appears variable, as in many 

neritids. Specimens showing the dots uniformly dis-
PALEONTOLOGY 59

tributed strongly resemble the pattern on a specimen 

from the upper Miocene of East Borneo. (Beets, 1941, 

p. 21, pi. 1, fig. 30). The Borneo specimen was referred 

to the Recent S. rangiana (Recluz), widely reported from 

the Indo-Pacific area.

Occurrence: Abundant (33 lots containing 77 specimens) in all 3 deep holes on Eniwetok Atoll at depths 

of 780-1,688 feet; age, Miocene (Tertiary e-g). A single poorly preserved specimen from drill hole 2A on 

Bikini, depth 967-978 feet (Tertiary g), probably represents the same species.

Smaragdia (Smaragdia) sp. A 

Plate 11, figures 8, 9

Shell minute, thin; spire low; callus large, moderately 

convex, very thick above, slightly thickened below; color 

pattern of body whorl consisting of two spiral rows of 

short axial brown dashes; in the upper row the lines are 

paired, in the lower row arranged in groups of three.

Measurements of the figured specimen (K-1B, Eniwetok, 715-727 ft I, USNM 648340: height 1.4 mm, 

diameter 1.4 mm.

Smaraydia sp. A is smaller than N. semari Beets from 

the late Miocene of East Borneo (Beets, 1941, p. 22, pi. 

1, figs. 31-43) and has one less spiral row of axial dashes.

Occurrence: In drill holes K-1B (depth 716-727 ft) 

and F-l (depth 660-670 ft) on Eniwetok Atoll in beds 

referred to late Miocene (Tertiary g).

The two specimens from Eniwetok are not given a 

name because they are probably immature. Fragments 

from drill holes 2A (depth 1,082^-1,088 ft) and 2B 

(depth l,576Vo-l,587 ft) on Bikini in beds referred to 

Tertiary / and e, respectively, show a somewhat different 

color pattern but may represent the same species.

Genus PISULINA Nevill and Nevill

Nevill and Nevill, 1869, Jour. Asiatic Soc. Bengal, v. 38, pt. 2, 

no. 2, p. 160, pi. 17, fig. 4.

Type (by monotypy) : Pixitlina adatnsiana G. and H. 

Nevill. Recent, Ceylon.

Pisulina subpacifica Ladd, n. sp. 

Plate 11, figure 10

Minute, globular; spire very low, aperture semilunar; 

outer lip thick, inner lip thinly callused with a large tooth 

centered below the midpoint and occupying fully onethird of the length of the lip; no trace of color pattern.

Measurements of the holotypc, USNM 648341: height 

1.2 mm, diameter 1.3 mm.

Occurrence: Holotype, the only specimen, from drill 

hole 2B on Bikini at depth of 789-799 feet; age, late 

Miocene (Tertiary g ).

The single large tooth differentiates this species from 

all other neritids reported from the island area. The 

genus has previously been known only from a few species 

living in India and Ceylon. The type species is a larger 

shell (the single fossil may be immature) with a higher 

spire.

Family LITTORINIDAE 

Genus TECTARIUS Valenciennes

Valenciennes, 1833, Coquilles, in Humboldt and Bonpland, Voyage aux regions equinoxiales du Nouveau Continent, v. 2, 

p. 271.

Type (by monotypy): Tectarius coronatus Valenciennes. Recent, Indo-Pacific.

Subgenus SUBDITOTECTARIUS Ladd, n. subgen.

Type: Tectarius (Subditotectarius) rehderi Ladd, n. 

sp., Miocene (Tertiary /), Bikini Atoll.

Small, stout; spire conical, base convex; marked with 

beaded spiral ribs and slightly oblique axial lines; 

strongly lirate within.

Distinguished by subdued sculpture; the strong tubercles that characterize other subgenera are represented 

only by small beads.

Tectarius (Subditotectarius) rehderi Ladd, n. sp. 

Plate 11, figures 11-13

Small, conical; whorls flat, base convex, imperforate; 

aperture broadly ovate, columella thickened below by 

a broad tooth; outer lip thin, strongly lirate within. 

Sculpture above the periphery consisting of five or six 

regularly spaced spiral ribs, the ribs close to the periphery 

being the strongest; on the base a strong rib lies immediately below the periphery and smaller ones lie between it and the columella.

Measurements of the holotype, USNM 648342: height 

2.8 mm, diameter 2.4 mm.

The apertural features including the lirate interior and 

the columellar tooth seem to place the fossils clearly in 

the genus Tectarius. In general form and outline the 

shells resemble Plesiotrochus, a cerithid that occurs with 

them. The sculpture of the fossils is basically similar 

to that of Tectarius s.s. but is much subdued. It is not 

known to be closely related to any living species.

Occurrence: Holotype from drill hole 2A on Bikini 

Atoll from a depth of 1,051-1,057 feet; a second specimen 

from F-l, Eniwetok at a depth of 960-970 feet; age, 

early Miocene (Tertiary /I.

Family IRAVADIIDAE 

Genus IRAVADIA W. T. Blanford

Blanford, W. T., 1867, Jour. Asiatic Soc. Bengal, v. 36, pt. 2, 

no. 1, p. 56-58, pi. 13, figs. 13, 14.
60 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Type (by monotypyi: Iravadia ornata Blanford. 

Brackish water, Recent, India.

Small Rissoina-like shells with strong spiral ribs and 

a callused unbroken aperture that is effusive anteriorly. 

Shell covered with a heavy periostracum. The type 

species lives in the brackish waters of the Irrawaddy 

delta, but another species lives under stones at extreme 

low water (Nevill, 1885, p. 97), and it is apparently 

marine.

Iravadia gardnerae Ladd, n. sp. 

Plate 11, figures 14, 15

Shell small, slender. Protoconch consisting of about 

two smooth whorls; later whorls gently convex, sutures 

impressed; body whorl with eight strong spiral ribs that 

are slightly narrower than the spaces between; penultimate whorl with four exposed ribs, earlier whorls with 

less; aperture oval, continuous, with a distinct anterior 

canal; interior of outer lip with three low elongate ridges.

Measurements of the holotype, USNM 648343: height 

3.3 mm, diameter 1.3 mm.

The fossil species closely resembles /. annulata Dunker (=7. trochlearis (Gould) I from Japan and the China 

coast, but shells of the Recent species are larger and 

stouter and the aperture is more heavily callused and 

less effusive anteriorly. The ridges inside the outer lip 

of the Recent shells are obscured by callus; most specimens show only one ridge (posterior), a few show two, 

and on rare shells all three arc discernible.

Occurrence: A total of 41 specimens were found in the 

cuttings from the three deep holes on Eniwetok (F-l, 

850-910 ft; E-l, 670-790 ft; K-1B, 800-936 ft); one 

specimen was recovered from a core in hole 2A on Bikini 

at 935 feet, 6 inches. Mo.<t of the occurrences are in beds 

referred to Tertiary y, but a few are from beds (below 

860 ft) that are referred to Tertiary /. The holotype 

is one of a dozen specimens from hole K-1B, depth, 831- 

842 feet.

Family RISSOIDAE

The risyoids include a great variety of small or minute 

high-spired shells that are extraordinarily abundant 

today in coral reef environments, particularly in lagoons. 

This abundance is not reflected in collections of fossils 

made from elevated reefs because preservation in such 

structures is generally poor. Well-preserved rissoids are 

found in abundance in drill holes through lagoonal beds 

on reef islands and in marly sediments laid down in 

shallow waters near volcanic islands.

In the present report the arrangement of genera and 

subgenera given by Wenz (1938-44) has been followed 

fairly closely. A total of 9 genera, 17 subgenera (1 described as new), and 54 species and subspecies has been 

recognized. Because many are represented by one or 

by only a few specimens, it is difficult or impossible to 

determine limits of variation. If more material were 

available, the species list might be shortened.

Genus PUTILLA A. Adams

A. Adams, 1867, Zool. Soc. London Proc., p. 312, 315.

Type (by monotypy): Putilla lucida A. Adams. Recent, Japan.

Includes very small short-spired shells with smooth or 

striate rounded whorls and a thickened outer lip.

Subgenus PSEUDOSETIA Monterosato

l'Nt'iif!i»n lia Moiilcrowito, 1884, C'oncbiglie Littoruli Mediterrane, 

p. 33.

Type (by subsequent designation, Bucquoy, Dautzenberg, and Dollfus, 1898, Mollusques Marins du Roussillon, v. 2, p. 772): Rissoa turyida Jeffreys. Recent, Norway.

Putilla (Pseudosetia) morana Ladd, n. sp. 

Plate 11, figures 16, 17

Minute, elongate, with blunt apex; smooth convex 

whorl of protoconch followed by 3l/2 gently convex sculptured whorls; imperf orate; aperture broadly oval, 

slightly constricted, peristome entire, inner lip thinly 

callused, edge of outer lip sharp, slightly thickened behind. Sculpture consisting of fine spiral striae over the 

entire surface of the postnuclear whorls.

Measurements of the holotype, USNM 648344: height 

1.1 mm, diameter 0.4 mm.

The Eniwetok fossil resembles the larger Putilla sernistriata Montague, a Recent European species, but the 

fossil is stouter and has a more blunt apex.

Occurrence: Single specimen from drill hole E-l, Eniwetok Atoll, at a depth of 1,805-1,835 feet; age, early 

Miocene (Tertiary e}.

Subgenus PARVISETIA Monterosato

Monterosato, 1884, Nomenclature generica e spezifica di alcune 

conchiglie mediterranee, p. 73, Palermo.

Type (by monotypy): Rissoa scillae Seguenza. Recent, Sicily.

Putilla (Parvisetia) goikulensis Ladd, n. sp. 

Plate 11, figures 18-20

Minute, ovate, with short spire and blunt apex; about 

four smooth convex whorls; imperforate, aperture 

broadly rounded, slightly constricted, peristome entire, 

outer lip thin, on some specimens slightly thickened 

behind.
PALEONTOLOGY 61

Measurements of the holotype, USNM 648345: height 

1.1 nnn, diameter 0.5 mm. Paratype, USNM 648346 

measures: height 0.9 mm, diameter 0.5 mm.

P. goiknlensis closely resembles P. scillae (Seguenza), 

the type of Parvisetia, but is smaller, more robust, and 

has a relatively smaller aperture.

Occurrence: Abundant in the late Miocene (Tertiary 

g) marls at the base of the Palau Limestone on the 

Goikul Peninsula, Babelthuap Island, Palau. (USGS 

21301, 21308 (types), 21310).

Putilla (Parvisetia) suvaensis Ladd, n, sp. 

Plate 11. figures 21, 22

Minute, ovate, with short spire and blunt apex; about 

four smooth whorls, fattened below a weak shoulder; 

aperture subcircular, slightly constricted; peristome entire, margin of outer lip thin but thickened behind into 

a varix.

Measurements of the holotype,USNM 648347: height 

0.9 mm, diameter 0.6 mm.

Putilla suvaensis has a shorter spire and less convex 

whorls than P. (P.) goikulensis from beds of comparable 

age in Palau.

Occurrence: Three specimens from the Suva Formation, Viti Levu, Fiji (stas. 160, FB-20 (holotype) and 

MR-20); age, Miocene (Tertiary /).

Genus CINGULA Fleming

Fleming, 1828, British animals, p. 297, 305.

Type (by subsequent designation, Gray, 1847, Zool. 

Soc. London Proc. Y>. 1531: Turbo cingillus Montagu. 

Recent, Atlantic coasts of Europe.

Small shells with gently convex whorls that may be 

smooth or spirally striate; outer lip sharp or slightly 

thickened.

Subgenus PERINGIELLA Monterosato

Monterosato, 1878, Giorn. sci. nat. econ. Palermo, v. 13. p. 87.

Type (by monotypy): Rissoa laevis Monterosato. Recent, Mediterranean Sea.

Includes minute to small species with blunt apex and 

slightly thickened outer lip.

Cingula (Peringiella) parryensis Ladd, n. sp. 

Plate 11, figures 23, 24

Small, elongate-oval with large body whorl, short spire, 

and blunt apex. Protoconch has about I 1/-* gently convex, polished, whorls showing fine axial lines under high 

magnification, coiled to form an apical depression; about 

three subsequent whorls, bearing faint spiral lines; suture

slightly channeled, bordered below by an obscure elevated thread. Aperture oval, angled above, peristome 

complete; inner lip callused, slightly extended below; 

edge of outer lip sharp, thickened behind by a riblike 

callus.

Measurements of the holotype, USNM 648348: height 

1.7 mm, diameter 0.8 mm.

Cingula parryensis resembles the Recent C. lampra 

described by Suter (1908, p. 29) from New Zealand, but 

that species does not have the depressed apex exhibited 

by the fossil.

Occurrence: Holotype and only specimen from drill 

hole E-l on Eniwetok Atoll at a depth of 700-710 feet; 

age, late ,Miocene (Tertiary g).

Cingula (Peringiella) cf. C. roseocincta (Suter)

Plate 11, figures 25, 26

Minute, globose, with blunt apex, short spire, and 

large body whorl. Protoconch consisting of l1/^ smooth 

convex whorls, followed by about 2l/2 smooth gently 

convex subsequent whorls. Suture well impressed, aperture broadly elliptical; peristome complete in adult 

specimens, flaring slightly below, with a deep groove 

behind inner lip in the umbilical region; edge of outer 

lip thin, thickened behind into an inconspicuous callus.

Measurements of the figured specimen, USNM 648349: 

height 1.0 mm, diameter 0.6 mm.

The fossil shells appear to be closely related to C. 

roseocincta (Suter, 1908, p. 29, pi. 2, fig. 26; 1913-15, p. 

209, pi. 12, fig. 171 and may be identical with it. One 

of the characteristics of the living shells is the color 

pattern: pink early whorls and pink bands on the body 

whorl. The fossils show no trace of color and this lack 

coupled with the general simplicity of form of these 

minute shells would seem to make a positive identification unwarranted.

Occurrence: Abundant in the late Miocene marls (Tertiary g) at the base of the Palau Limestone on Goikul 

Peninsula, Babelthuap Island, Palau (USGS 21301, 

21304 (figured specimen) ,21308and21310) ; a single specimen from drill hole E-l, Eniwetok Atoll, at depth of 620- 

630 feet (Tertiary g); four specimens from drill hole 

MU-4 from a depth of 41 feet are Recent in age.

Genus AMPHITHALMUS Carpenter

Carpenter, 1864, British Assoc. Adv. Sci. Rept., 1863, p. 614, 656.

Type (by original designation): Amphithalmus inclusus Carpenter. Recent, California.

The genus Amphithalmus includes small elongate shells 

with a blunt apex. In Amphithalmus s. s. the oval aperture is surrounded by a double peristome.
62 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Submenus CEROSTRACA Oliver

Oliver, 1915, New Zealand Inst. Trans., v. 47, p. 521.

Type (by original designation): Cerostraca iredalei 

Oliver. Recent, Kermadec Islands.

Thin ovate shells with impressed suture; aperture 

entire, sometimes detached; outer lip with a varixlike 

callosity.

Amphithalmus (Cerostraca) jeffcoati Ladd, n. sp. 

Plate 11, figures 27-31

Small, thin, ovate; about five convex whorls; suture 

impressed; aperture broadly lenticular to subcircular; 

margin of callus of inner lip distinct, in some shells separated from the body whorl; outer lip thin, slightly expanded with a conspicuous callosity a little distance 

behind the edge. Shell smooth or with rounded slightly 

oblique axial ribs that are best developed on the central part of the body whorl.

Measurements of the holotype (smooth .shell from E-l, 

840-850 ft) USNM 648350 ': height 1.9 mm, diameter 

1.2 mm. Paratype A (weakly ribbed shell from K-1B, 

968-978 ft I, USNM 648351:* height 1.9 mm, diameter 

1.2 mm. Paratype B (strongly ribbed shell from E-l, 

1,010-1,020 ft), USNM 648352: height 2.3 mm, diameter 

1.3 mm.

Some of the Marshall Island fossils show a detached 

aperture comparable to that of the Recent type species 

('. iredalei Oliver, but on other specimens there is no 

gap between the inner lip and the shell, though the 

margin of the inner lip is distinct. Some of the fossils 

are smooth, as is the type specimen, others have welldeveloped axial ribs on the lower whorls, all gradations 

between these two conditions being' recognizable.

Occurrence: In all three deep drill holes on Eniwetok 

Atoll at depths of 620-2,060 feet but never in abundance; 

age, Miocene (Tertiary {/-el. A single specimen from 

hole F-l at a depth of 55-60 feet is Recent. It is more 

slender than the older shells and has 6y2 smooth whorls 

but is not recognized as a distinct species. One specimen 

in hole 2A on Bikini at a depth of 935-946 feet is referred to Tertiary ij\ three specimens in hole 2B on 

Bikini from 1,870-1,944 feet are referred to Tertiary e.

Amphithalmus (Cerostraca?) myersi Ladd, n. sp. 

Plate 11, figures 32, 33

Very small, elongate-ovate, robust; about l 1/^ smooth 

convex whorls of protoconch followed by three gently 

convex sculptured whorls, each of the subsequent whorls 

with an obscure shoulder about a third of the way 

below the moderately impressed suture; aperture subcircular; inner lip thinly callused, outer lip sharp but 

expanded behind into an inconspicuous varixlike callosity. Sculpture consisting of fine spiral lines.

Measurements of the holotype, USNM 648353: height 

1.5 mm, diameter 0.9 mm.

Reference of A. myersi to Cerostraca is questioned 

because of the presence of fine spiral sculpture. The 

species is smaller and more slender than A. jeffcoati that 

occurs with it in drill hole E-l on Eniwetok.

Occurrence: Holotype and only specimen from drill 

hole E-l, Eniwetok Atoll, at a depth of 770-780 feet; 

age, late Miocene (Tertiary g).

Subgenus PISINNA Monterosato

Monterosato, 1878, Giorn. sci. nat. econ. Palermo, v. 13, p. 86.

Type (by monotypy): Rissoa punctulum Philippi 

I #. glabrdta auct.==R. seniinulum Monts==R. sabulum 

Cantraine==fi> . mandralisci Aradas). Recent, Mediterranean Sea.

Small elongate-oval to pupoid shells with oval to subcircular aperture; smooth or with axial folds.

Amphithalmus (Pisinna) bikiniensis Ladd, n. sp.

Plate 12, figure 1

 Minute, pupoid, stout, polished; l1/^ moderately convex whorls of protoconch followed by about four flattened whorls; suture impressed; imperforate; aperture 

broadly ovate, slightly constricted; inner lip callused, its 

boundary sharply defined; outer lip sharp, thickened 

within. Shell smooth or with a few obscure axial folds 

on body whorl.

Measurements of the holotype <2B, Bikini, 1,839-1,850 

ft), USNM 648354: height 1.7 mm, diameter 0.7 mm.

A. (P.) bikiniensis resembles the Recent Rissoa subfusca Hutton from the New Zealand area (Suter, 1913- 

15, p. 210, pi. 12, fig. 18). Iredale (1915, p. 254) later 

placed R. subfusca in Estea (=Pisinna], but that species 

has more whorls and shows traces of microscopic spiral 

striation.

Occurrence: In drill hole 2B on Bikini Atoll; total of 

17 specimens in 8 lots at depths of 1,807-1,892 feet; age, 

early Miocene (Tertiary e).

Genus ALVANIA Risso

Risso, 1826, Histoire nuturelle des prineipales productions de 

1'Europe meridionale, v. 4, p. 140.

Type (by subsequent designation, Monterosato, 1884, 

Conchiglie Littorali Mediterranee, p. 19): Rissoa montaqui Payraudeau=E. sardea Risso. Recent, Mediterranean Sea.
PALEONTOLOGY 63

Alvania s.s.

Small robust conical shells with a sharp apex and an 

elongate-oval aperture; bearing strong axial ribs and 

weaker spirals; outer lip thickened.

Subgenus TARAMELLIA Seguenza

Seguenza, 1903, Palaeontographica Italica, v. 9, p. 53-54.

Type (by monotypy): Turbo zetlandica Montagu. 

Recent, Europe.

Small elongate to conical shells with strong spiral 

ribs and equally strong axial ribs except below periphery; 

aperture circular, peristome double.

Alvania (Taramellia) corayi Ladd, n. sp. 

Plate 12, figure 2

Minute, broadly conical, stout; apex sharp; protoconch 

large, consisting of about two smooth whorls; later 

whorls flat, suture incised; imperforate; aperture subcircular; lip double, inner one continuous, outer one 

thickened. Sculpture consisting of strong spiral ribs and 

somewhat weaker axial ribs; axial sculpture much reduced on lower half of body whorl.

Measurements of the holotype, USNM 648355: height 

1.6 mm, diameter 1.3 mm.

The Eniwctok fossil is not turreted as is the type 

species of Taramellia; its whorls are flatter and its outer 

lip is much thicker than in the type.

Occurrence: Seventeen specimens from several drill 

holes on Eniwetok Atoll to depths of 60 feet (holotype 

from Mu-4, depth 35-36 ft); all occurrences probably 

Recent.

Alvania (Taramellia) kenneyi Ladd, n. sp. 

Plate 12, figure 3

Minute, conical, solid; protoconch large, bulbous, consisting of about 2V2 smooth whorls; later whorls flat, 

suture deeply incised; imperforate; aperture circular; 

inner lip double. Sculpture of body whorl consisting of 

six strong spiral ribs, the upper two of which are cut 

into sharp upturned projecting points by axial ribs that 

give the shell a stellate appearance when viewed from 

above.

Measurements of the holotype (E-l, Eniwetok, 1,746- 

1,777 ft), USNM 648356: height 0.8 mm, diameter 0.5 

mm.

A. kennetji is smaller than A. corayi, has a more deeply 

incised suture and a thinner outer lip.

Occurrence: Six specimens from drill hole E-l, Eniwetok Atoll, at depths of 830-1,925 feet; age, Miocene 

(Tertiary g and e).

Genus MERELINA Iredale 

Iredale, 1915, New Zealand Inst. Trans., v. 47, p. 449.

Type (by original designation): Rissoa cheilostoma 

Tenison-Woods. Recent, Tasmania.

Subgenus MERELINA s.s.

Includes moderately solid strongly clathrate shells; 

protoconch spirally striate, peristome continuous, duplicated internally.

Merelina (Merelina) pisinna (Melvill and Standen) 

Plate 12, figures 4, 5

Alvania pisinna Melvill and Standen, 1896, Jour. Conchology 

[Leeds], v. 8, p. 305, pi. 11, fig. 60.

Very small, slender, stout; whorls of protoconch 

about two, convex, bearing spiral striae; subsequent 

whorls, three, gently convex, separated by a deeply lirate 

suture; imperforate; aperture rounded, outer lip thickened with a double wall. Sculpture clathrate, consisting 

of strong spiral ribs, (3 exposed on penultimate whorl, 

5 on body whorl, below which are 2 or 3 short nearly 

smooth spirals) crossed by equally strong axial ribs (18 

on body whorl), beaded at intersections with spirals; 

axial ribs obsolete on basal part of body whorl.

Measurements of the figured specimen (E-l, Eniwetok, 

850-860 ft), USNM 648357: height 1.9 mm, diameter 0.9 

mm.

M. pisinna is smaller and proportionately shorter than 

the type species M. cheilostoma (Tenison-WoodsI, but 

I have not seen specimens.

The clathrate sculpture pattern of M. pisinna is 

matched almost exactly by M. granulosa (Pease), a 

Recent species from Hawaii (USNM 345037), but the 

Hawaiian shells have a smooth and glossy protoconch. 

Only a few of the two dozen fossils from the Marshall 

Islands show traces of spiral sculpture on the whorls of 

the protoconch, and these traces can be clearly seen 

only under high magnification.

Occurrence: In drill holes on Eniwetok at depths of 

620-930 feet; in beds referred to Miocene (Tertiary / 

and g) ; in drill holes on Bikini at depths of 925-1,944 

feet; early Miocene (Tertiary e and /) ; two specimens 

were recovered from the Suva Formation on Viti Levu, 

Fiji (sta. FB-20); age, Miocene (Tertiary /). The 

species was originally described from the Loyalty Islands 

and has been reported from the Kermaclecs.

Subgenus LINEMERA Finlay

Finlay, 1924. New Zealand Inst. Trans.. v. 55, p. 483.

Type (by original designation): Rissoa gradata Hutton. Recent, New Zealand.
64 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Includes shells with clathrate sculpture as in Merelina 

s.s., but with smooth and glossy protoconch and a single 

rimmed aperture.

Merelina (Linemera) telkibana Ladd, n. sp.

Plate 12, figures 6, 7

Very small, robust; about two smooth convex whorls 

of protoconch followed by about three flattened sculptured whorls; suture deeply incised; aperture broadly 

ovate, peristome entire, umbilical chink present, outer lip 

thickened to form a varix. Sculpture consisting of moderately strong axial ribs that become obsolete on the basal 

part of the body whorl and weak spirals that are prominent only on the base of the last whorl.

Measurements of the holotype, USNM 648358: height 

1.9 mm, diameter 1.0 mm.

The axial ribs of M. telkibana are much finer and more 

numerous than those of Rissoa gradata Hutton, the type 

of Linemera.

Occurrence: A total of 14 specimens from late Miocene 

(Tertiary g) marls at the base of the Palau Limestone 

near Goikul, Babelthuap Island, Palau (USGS 21301).

Genus PARASHIELA Laseron

La^cron, 1956. Australian Jour. Marino and Froshwator Rosearch, 

v. 7, no. 3, p. 439.

Type (by original designation): Parashiela ambulata 

Laseron. Recent, Great Barrier Reef, Australia.

Short broad shells with widely spaced axial ribs and a 

single spiral rib at the shoulder.

Parashiela beetsi Ladd, n. sp.

Plate 12, figures 8, 9

Minute, short, white, translucent; protoconch of l 1/^ 

glassy rapidly enlarging whorls followed by about 3% 

strongly shouldered sculptured whorls; aperture subcircular, peristome complete; outer lip with a double 

wall that is thickened behind to form a low varix. Sculpture consisting of fine widely spaced axial ribs and a 

single spiral rib at the shoulder.

Measurements of the holotype, USNM 648368: height 

1.4 mm, diameter 0.9 mm. Paratype, USNM 648369: 

height 1.5 mm, diameter 1.0 mm.

P. beetsi has the unusual sculpture that characterizes 

the type species (and only other known species) P. ambulata, but it differs by possessing a double-walled outer 

lip that is thickened behind to form a low varix. A 

similar type of open sculpture is exhibited by Rissoa invisibilis Hedley from a Funafuti lagoon beach (Hedley, 

1899a, p. 418), but that species has three prominent 

spiral ribs.

Occurrence: Two specimens from drill hole F-8-C on 

Eniwetok Atoll a depth of 19-22 feet; age, Recent.

Genus ZEBINA H. and A. Adams

H. and A. Adams, 1854, Genera Recent Mollusca, v. 1, p. 328.

Type (by subsequent designation, G. Nevill, 1885, 

Hand list Mollusca Indian Mus., pt. 2, p. 93): Rissoina 

coronata Recluz. Recent, Mauritius.

Subgenus ZEBINA s.s.

The type species is smooth except for the early whorls 

which are axially ribbed; the outer lip is thickened with 

one or more tubercles on the anterior part. No examples 

of Zebina s.s. have been found in the fossil faunas of the 

island area.

Subgenus CIBDEZEBINA Woodring 

Woodring, 1928, Carnegie Inst. Washington Pub. 385, p. 369.

Type I by original designation I: Rissoina browniana 

d'Orbigny. Recent, West Indies.

Small smooth shells with flat whorls and a varicose 

outer lip that is extended forward; outer lip with a denticle near the posterior angle and a second denticle near 

the base.

Zebina (Cibdezebina) metaltilana Ladd, n. sp.

Plate 12, figure 10

Small, slender, smooth, and polished; about three convex whorls of protoconch, six flattened subsequent 

whorls; suture linear or lightly impressed; aperture oval 

with acute posterior angle and broad shallow anterior 

channel; inner lip callused, outer lip thickened into a 

smooth varix and extended forward; outer lip with a 

broad but prominent denticle near the posterior angle 

and a less conspicuous dentical near the base; siphonal 

fascicle slightly swollen.

Measurements of the holotype (drill hole 2B, Bikini 

Atoll, 1,860-1,870 ft), USNM 648359: height 3.5 mm, 

diameter 1.4 mm. Paratype (drill hole A-l, Eniwetok 

Atoll, 136-138 ft), USNM 648360: height 3.1 mm, 

diameter 1.2 mm.

The Marshall Island shells agree in all important 

features with the type of Cibdezebina Rissoina browniana known from Miocene to Recent in the Caribbean 

area (Woodring, 1928, p. 370), but it is distinctly more 

slender in outline. The holotype of Z. metaltilana shows 

both denticles on the outer lip, but in many specimens, 

both Miocene and Recent, the anterior denticle is not 

developed.

Occurrence: In many drill holes on Bikini and Eniwetok Atolls at depths of 1-2,349 feet but never in great 

abundance; age, Recent to early Miocene (Tertiary e).
PALEONTOLOGY 65

A single specimen was recovered from the Suva Formation on Viti Levu, Fiji (sta. FB-20); age, Miocene 

(Tertiary /); a few specimens were dredged from a depth 

of 25 fathoms in the Bikini lagoon.

Subgenus MORCHIELLA G. Nevill 

Nevill, 1885, Hand list Mollusca Indian Mus., pt. 2, p. 88.

Type (by original designation): Rissoina gigantea 

Deshayes. Recent, Philippine Islands.

Small to medium-sized solid shells whose apical whorls 

are characteristically more strongly sculptured than later 

whorls.

Zebina (Morchiella) cf. Z. cooperi (Oliver)

Plate 12, figures 11, 12

Medium in size, stout; about l 1/^ smooth convex whorls 

of protoconch and five or six flattened subsequent whorls; 

most, or all, of the whorls above the body whorl bear 

slightly oblique axial ribs and these are strongest near 

the apex; suture hardly discernible; aperture sublenticular, posterior angle sharp, anterior channel indistinct, 

inner lip callused; outer lip thickened and extended forward, with one or two broad low denticles inside, one 

near the base, the other, if present, at about the midpoint.

Measurements of the figured specimen, USNM 648361: 

height 5.7 mm, diameter 2.3 mm; another specimen, 

USNM 648362, probably immature, measures: height 

3.3 mm, diameter 1.5 mm.

Some of the Marshall Island specimens are slightly 

more slender than the shell described from the Kermadecs 

(Oliver, 1915, p. 520), and show two rather than three 

low tubercles inside the outer lip; they likewise have a 

less distinct posterior canal. In describing the Kermadec 

shell, Oliver mentioned "3 minute longitudinal plications" 

on the parietal wall near the posterior canal. These do 

not appear on his published figure nor on specimens from 

the type area identified by Oliver, nor can they be seen 

on the Marshall Island shells here described.

Occurrence: Two specimens from drill hole E-l on 

Parry Island, Eniwetok Atoll, at depth of 110-120 feet 

(figured specimen) and 10-20 feet (immature specimen) ; 

age, Recent. A single Recent shell was also collected 

from drift on Enybarbar Island, Rongelap Atoll. A fossil from drill hole 2B on Bikini Atoll at a depth of 2,235- 

2,246 feet; age, early Miocene (Tertiary e) ; it may be a 

Recent shell pumped in from the mud pits.

Zebina (Morchiella) killeblebana Ladd, n. sp. 

Plate 12, figures 13, 14

Medium in size, stout, polished; spire short, diameter 

of shell slightly exceeding one-half the height. Whorls 

of spire about six, first three showing faint traces of

axial ribs, early whorls flat sided, later whorls gently 

convex; suture not impressed; aperture semicircular; 

inner lip heavily callused, with a denticle next to the 

acute posterior angle, anterior channel broad and shallow; outer lip sharp but thickened behind the peristome 

and slightly extended forward, bearing two or three low 

denticles inside.

Measurements of the holotype, USNM 648363: height 

5.6 mm, diameter 3.0 mm. Paratype, a smaller shell that 

may be immature, USNM 648364: height 3.2 mm, diameter 1.8 mm.

The fossil is closely related to the Recent Z. tridentata 

Michaud, widely distributed in the Indo-Pacific area, 

but the Recent shell is appreciably more slender.

Occurrence: Eniwetok Atoll in drill hole E-l, depth 

960-970 feet (holotype) and in drill hole F-l, 930-940 

feet (paratype); age, early Miocene (Tertiary /).

Subgenus AILINZEBINA Ladd, n. subgen.

Type: Zebina (Ailinzebina) abrardi Ladd, n. sp.

Small, slender; protoconch consisting of two smooth 

whorls coiled at a slight angle to remainder of spire; 

early subsequent whorls bearing heavy axial ribs that 

become finer and more numerous on later whorls; spiral 

sculpture conspicuous only on body, whorl; siphonal 

fasciole heavy but ill defined.

Resembles Morchiella in that there is a progressive 

reduction in axial sculpture, but in Ailinzebina the axials 

are not obliterated, even on the body whorl.

Zebina (Ailinzebina) abrardi Ladd, n. sp.

Plate 12, figures 15-18

Small, slender; two smooth whorls of protoconch coiled 

at slight angle to axis of spire; about six gently convex 

subsequent whorls; the early ones bearing heavy slightly 

oblique axial ribs that become progressively smaller and 

more numerous on later whorls; suture impressed; aperture lenticular, posterior channel narrow and moderately 

deep; anterior channel broad and shallow; outer lip 

thickened and extended forward; spiral threads are most 

conspicuous on the body whorl on and near the heavy 

siphonal fasciole.

Measurements of the holotype (pi. 12, figs. 15, 16) a 

Recent shell from Bikini, USNM 648365: height 3.9 

mm, diameter 1.3 mm. Paratype A, (pi. 12, fig. 17) a fossil from drill hole En-4, depth 11 feet, Eniwetok, USNM 

648366: height 2.9 mm, diameter 0.9 mm. Paratype B, 

(pi. 12, fig. 18) a fossil from drill hole 2B, depth 1,450- 

1,461 feet, Bikini, USNM 648367: height (incomplete) 

2.3 mm, diameter 0.9 mm.

Occurrence: Living in the northern Marshall Islands 

(Bikini and Rongerik); the holotype is a Recent shell
66 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

dredged from the Bikini lagoon at a depth of 20 fathoms. 

Fourteen fossils were recovered from several drill holes on 

Eniwetok to depths of 60 feet, and two specimens were 

obtained from drill hole 2B on Bikini at depths of 1,450- 

1,608 feet in early Miocene (Tertiary e-f).

Genus ZEBINA s. 1.

Zebina? sp. A 

Plate 12, figure 19

Small, stout; whorls gently convex, with strong axial 

ribs; 27 ribs and fine spiral threads on last whorl; inner 

lip with a single strong denticle anteriorly; outer lip witli 

low widely spaced internal ribs.

Measurements of the figured specimen, USNM 648370: 

height 2.7 mm, diameter 1.2 mm.

The single fossil has an incomplete outer lip. The 

well-developed axial ribs combined with the strong 

anterior denticle differentiates this species from others 

found in the area; if better type material were available, 

the species might be recognized as belonging to a new 

subgenus.

Occurrence: Drill hole 2B, Bikini Atoll at a depth of 

2,112-2,128 feet; early Miocene (Tertiary e\.

Genus RISSOINA d'Orbigny

d'Orbiguy, 1840. Voyage dans l'Amoru|Uc meridionulo, v. 5, p. 

395.

Subgenus SCHWARTZIELLA Nevill

Nevill, 1884, Hand list Mollusea Indian Mus., pt. 2, p. 82.

Type (by original designation): Rissoina bryerea 

(Montagu* [Turbo]. Recent, Cuba.

Includes strongly ribbed species some of which also 

bear spiral striae; the oval aperture is slightly angled 

below.

Rissoina (Schwartziella) gracilis (Pease) 

Plate 12, figure 20

Rissoa gracilis Pease, 1860, Zool. Soc. London Proc., p. 438. 

Rissoina gracilis Garrett, 1873, Acad. Nat. Sci. Philadelphia,

Proc., p. 211, pi. 2, fig. 8. 

Tryon, 1887, Manual Conchology 9, p. 373, pi. 55, fig. 42.

Small, slender; about three glossy convex whorls of 

protoconch followed by six gently convex sculptured 

whorls; suture margined; aperture oval, anterior channel broadly rounded, moderately deep; inner lip callused, 

outer lip extended forward near its midpoint, thickened 

to form a varix. Sculpture consisting of strong slightly 

oblique axial ribs almost as wide as the intervening 

spaces; ribs flexuous on body whorl.

Measurements of the figured specimen, B. P. Bishop 

Museum, geology No. 1340: height 3.0 mm, diameter 0.9 

mm.

The species appear to be well named, for it is more 

slender than any other Rissoina found in the island area.

Occurrence: One specimen, about 1 mile southwest of 

Houma, Tongatabu, Tonga; altitude 35 feet; age, probably Pleistocene. The Recent shell briefly described 

(without measurements) by Pease was collected in 

Hawaii; Garrett's specimens came from Fiji; Tryon mentions the Society Islands as well as Fiji.

Rissoina (Schwartziella) aff. R. flexuosa Gould 

Plate 12, figures 21, 22

Small, stout; two smooth whorls of protoconch followed 

by about seven sculptured gently convex whorls; suture 

slightly impressed; aperture broadly lenticular, posterior 

channel narrow; anterior channel wide, slightly undercutting the columella; outer lip thickened; subsequent 

whorls bearing strong narrow, straight or slightly oblique 

axial ribs, 17-21 on the body whorl; traces of spiral 

sculpture are preserved on the lower part of the body 

whorl on most specimens. Siphonal fasciole low, not 

sharply defined.

Measurements of the figured specimen, USNM 648382: 

height 4.0 mm, diameter 1.5 mm.

The fossils are more slender than the Recent Australian 

shell (Gould, 1861, p. 400), and their spiral sculpture is 

less well developed.

Occurrence: Four specimens from drill hole E-l on 

Eniwetok Atoll at depths of 40-45 feet (figured specimen) and 60-70 feet; age, Recent; a specimen from 

drill hole 2B on Bikini Atoll at a depth of 1,492-1,503 

feet should be referred to Tertiary e, but it shows evidence of wear and may have been derived from a higher 

horizon. A single specimen from Guam from the Mariana 

Limestone at USGS locality 20600; age, 'probably 

Pleistocene.

Rissoina (Schwartziella) aff. R. indrai Beets 

Plate 12, figures 23, 24

Large, stout; about seven gently convex whorls with a 

slight suggestion of a shoulder; suture moderately impressed; aperture lenticular, posterior channel narrow 

and shallow, anterior channel broad and deep, peristome 

heavily callused, outer lip thickened and extended forward. Sculpture consisting of slightly curved axial ribs 

and spiral threads. Ribs are coarse on early whorls but 

become smaller and more numerous on later whorls 

(about 40 on penultimate whorl, about 50 on body 

whorl) ; spiral threads become increasingly prominent on 

later whorls as ribs decrease in size; on last two whorls, 

ribs are beaded by spirals; on base of body whorl and on 

thickened exterior of outer lip, the spirals dominate axial 

ribs.
PALEONTOLOGY 67

Measurements of the figured specimen, USNM 648383: 

height 7.7 mm, diameter 3.1 mm.

The Eniwetok fossil appears to differ from the Borneo 

form in that the whorls have a slight shoulder, whereas 

in the Borneo fossils the whorls are thickest near the base.

Occurrence: A single specimen from drill hole F-I, 

Eniwetok Atoll, at a depth of 930-940 feet; early 

Miocene (Tertiary /). R. indrai was described by Beets 

(1941, p. 23, pi. 1, figs. 44-48, 52-56) from the Miocene 

(Tertiary /) of eastern Borneo.

Two incomplete specimens from younger (Tertiary g) 

beds in drill hole F-l (690-700 ft) and K-1B (758-768 

ft) may represent this species. Both are smaller than 

the figured specimen and are more coarsely ribbed, the 

discrepancy in size between the ribs on the early whorls 

and those of the later whorls being much less marked 

than in the figured specimen.

Rissoina (Schwartziella) mejilana Ladd, n. sp. 

Plate 12, figures 25, 26

Small, short, stout; about lVi> smooth convex whorls 

forming protoconch, followed by five sculptured gently 

convex whorls; suture impressed; aperture lenticular, 

posterior angle acute, anterior channel broad and moderately deep; peristome callused, edge of outer lip thin but 

thickened behind to form a low varix. Sculpture consisting of weak to moderately strong axial ribs, 23 or more 

on body whorl; fine spiral threads are on the lower part 

of body whorl but visible only under high magnification.

Measurements of the holotype (K-1B, Eniwetok, 831- 

842 ft), USNM 648384: height 2.8 mm, diameter 1.1 mm.

Characterized particularly by its short stout form and 

numerous axial ribs.

Occurrence: Four specimens from three deep holes on 

Eniwetok at depths of 800-990 feet; age, early Miocene 

(Tertiary /).

Rissoina (Schwartziella) jirikana Ladd, n. sp.

Plate 12, figures 27, 28

Very small, stout; two smooth gently convex whorls 

form protoconch, followed by 3V-> sculptured whorls likewise of slight convexity; suture deeply impressed; aperture lenticular, posterior angle acute, anterior channel 

broad and moderately deep; inner lip heavily callused; 

edge of outer lip thin but thickened behind to form a low 

varix. Sculpture consisting of weak widely spaced axial 

ribs.

Measurements of the holotype <2B, Bikini, 1,440-1,451 

ft), USNM 648385: height 2.3 mm, diameter 0.9 mm.

This Schwartziella is smaller than S. mejilana from 

younger Miocene beds at Eniwetok, has fewer whorls, 

fewer axial ribs, and a more deeply impressed suture.

Occurrence: Two specimens from drill hole 2B, Bikini 

Atoll, at a depth of 1,419-1,451 feet; age, early Miocene 

(Tertiary e).

Rissoina (Schwartziella) rilebana Ladd, n. sp. 

Plate 12, figures 29, 30

Small, pupoid, thick; protoconch of three smooth convex whorls followed by five gently convex sculptured 

whorls; suture obscure; aperture ovate, posterior angle 

acute, anterior channel broad and moderately deep, 

peristome callused, outer lip thickened externally. Sculpture consisting of 12 strong widely spaced continuous 

axial ribs.

Measurements of the holotype (2B, Bikini, 778-789 

ft) USNM 648386: height 3.1 mm, diameter 1.3 mm.

Characterized particularly by its pupoid form and continuous axial ribs. R. rilebana appears to be very closely 

related to R. triticea Pease, a Recent species known from 

Hawaii and many parts of the Indo-Pacific, but that 

species is less pupiform and has a more clearly exposed 

suture.

Occurrence: Two specimens from drill hole 2B, Bikini 

Atoll, at a depth of 778-831 feet; age, late Miocene 

(Tertiary g).

Subgenus ZEBINELLA Morch 

Morch, 1876, Malakozoologische Blatter, v. 23, p. 47.

 Type (by subsequent designation, Nevill, 1885, Hand 

list Mollusca Indian Mus., pt. 2, p. 73, 87): Rissoina 

decussata (Montagu) [Helix]. Recent, West Indies.

Includes species with fine axial ribs and spiral threads; 

outer lip thickened into a varix and extended forward; 

anterior channel shallow, only slightly undercutting 

columella.

Rissoina (Zebinella) emnanana Ladd, n. sp. 

Plate 12, figures 31, 32

Medium in size, moderately slender; protoconch of 

three smooth convex whorls followed by about six inflated whorls; suture impressed; aperture semicircular; 

posterior channel narrow and deep; anterior channel 

broad, slightly undercutting the callus of the inner lip; 

outer lip moderately thickened, extended slightly forward 

and flaring. Sculpture consisting of close-set oblique 

axial ribs that are slightly more prominent on the spire 

than on the body whorl; between axials are numerous 

fine spiral threads.

Measurements of the holotype <E-1, 1,010-1,020 ft), 

USNM 648387: height 4.8 mm, diameter 2.1 mm.

R. emnanana is characterized particularly by its inflated whorls and impressed suture; it differs in these 

features from the West Indian type species R. decussata
68 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

(Montagu) and from other Zebinellas from the Marshall 

Islands.

Occurrence: In drill holes E-l and K-1B, Eniwetok 

Atoll, at depths of 620-1,020 feet (total of nine specimens) ; age, Miocene (Tertiary / and g).

Rissoina (Zebinella) tenuistriata Pease 

Plate 12, figures 33, 34

Rissoina tenuistriata Pease, 1867, Am. Jour. Conchology, v. 3, p.

295, pi. 24, fig. 30. 

Tryon, 1887, Manual Conchology, v. 9, p. 386, pi. 58, fig. 24.

Medium in size, slender; protoconch of about 21/4 unmarked convex whorls followed by six gently convex 

whorls; suture lightly impressed; aperture lenticular, 

posterior channel narrow and deep, anterior channel 

broad and shallow, slightly undercutting the callus of the 

inner lip. Outer lip thickened and extended forward. 

Sculpture consisting of close-set slightly curved axial 

ribs, which become obsolete on the lower half of the body 

whorl, and fine spiral threads.

Measurements of the holotype En-4, Eniwetok, 5V2 ft, 

USNM 648388: height 5.5 mm, diameter 2.3 mm.

Occurrence: Eighteen specimens from several drill 

holes on Eniwetok Atoll from near the surface to 30 feet; 

rare at greater depths to 915 feet; a single specimen 

from drill hole 2A on Bikini, depth 306-310 feet (PostMiocene). Age, Recent to early Miocene (Tertiary /). 

The Miocene specimens are smaller than the Recent 

shells.

R. tenuistriata, first described from the Tuamotu 

[Paumotu] Islands, is now recognized in many parts of 

the Indo-Pacific.

Rissoina (Zebinella) aff. R. supracostata Garrett 

Plate 12, figures 35, 36

Large, moderately slender; whorls, exclusive of protoconch; about seven uniformly convex; suture impressed; 

aperture large, broadly lenticular; inner lip callused, 

outer lip thickened; siphonal fascicle low, smooth. Sculpture consisting of slightly oblique axial ribs on upper 

whorls of spire and fine close-set spiral striae over all 

whorls.

Figured specimen, USNM 648389: height (without 

protoconch) 12.4 mm, diameter 2.9 mm.

Occurrence: A single specimen from drill hole E-l on 

Eniwetok, depth 890-900 feet; age, early Miocene, Tertiary /. The large shell probably represents an undescribed species, but a name is withheld pending better 

type material.

Resembles R, supracostata, a Recent species described 

by Garrett 11873, p. 209) from Fiji, but in that species

the whorls of the spire are distinctly turreted and the 

shell has a more elevated siphonal fasciole.

Subgenus PHOSINELLA Morch

March, Malakozoologische Blateer, v. 23. p. 51.

Type (by subsequent designation, Nevill, 1885, Hand 

list Mollusca Indian Mus., pt. 2, p. 73, 83): Rissoa 

pulchra C. B. Adams. Recent. West Indies.

Includes species with strong reticulate sculpture, a distinct siphonal fasciole, and an anterior channel that is 

broad and deep.

Rissoina (Phosinella) clathrata A. Adams 

Plate 12, figure 37; plate 13, figures 1, 2

Rissoina clathrata A. Adams, 1851, Zool. Soc. London Proc., p. 265.

Tryon, 1887, Manual Conchology 9, p. 381, pi. 57, fig. 79. 

Rissoina (Phosinella) clathrata A. Adams, Abrard, 1946, Annales 

de paleontologie, v. 32, p. 54, pt. 4, fig. 17.

Medium in size, stout; about eight gently convex 

whorls; aperture broadly lenticular, extended forward 

below; posterior angle slightly less than 90°; outer lip 

with a strong varix; anterior channel broad and deep. 

Sculpture reticulate; axial ribs (about 17 on last whorl) 

crossed by spiral ribs (5 on last whorl), most of which 

are stronger than axial ribs; intersections beaded; 

siphonal fasciole heavy and beaded, separated from the 

lowest spiral rib by a prominent sulcus.

Measurements of the New Hebrides specimen (pi. 12, 

fig. 37): height (incomplete) 8.7 mm, diameter 3.6 mm. 

The figured Fijian shell (pi. 13, figs. 1, 2), USNM 

648391: height 7.2 mm, diameter 2.6 mm.

Occurrence: Island of Malekula, New Hebrides, in beds 

of Pliocene age; four specimens from Viti Levu, Fiji 

(stas. 160, 160A, and FB-20) in the Suva Formation of 

Miocene age (Tertiary /). Living shells have been reported from the Philippines, Australia, Singapore, and 

the Red Sea; rare in the Marshall Islands.

R. clathrata appears to be a somewhat variable species. 

The two Fijian fossils are worn and are smaller than the 

New Hebrides fossil and Recent shells.

Rissoina (Phosinella) briggsi Ladd, n. sp. 

Plate 13, figures 3, 4

Small, slender; protoconch of two smooth whorls followed by about six sculptured whorls; aperture semicircular, inner lip slightly curved, posterior angle sharp, 

outer lip broadly rounded with a prominent varix; anterior channel broad and moderately deep. Sculpture 

sharply reticulate; strong axial ribs (13 on last whorl) 

crossing almost equally prominent spiral ribs (4 on last 

whorl); intersections beaded; siphonal fasciole strongly
PALEONTOLOGY 69

beaded, separated from the spiral ribs by a broad deep 

sulcus.

Measurements of holotype (Palau, USGS 21301). 

USNM 648390: height 4.3 mm, diameter 1.8 mm.

R. briygsi is similar to R. clathrata A. Adams, a larger 

Recent Indo-Pacific species also known from the Pliocene 

of the New Hebrides and the Miocene of Fiji. R. briggsi 

has fewer and sharper axial and spiral ribs than does 

R. clathrata.

Occurrence: Abundant in the late Miocene (Tertiary 

g] marls at the base of the Palau Limestone, northwest 

of Goikul, Babelthuap Island, Palau. (USGS 21301, 

21304).

Rissoina (Phosinella) balteata Pease 

Plate 13, figures 5-8

Rissoina bnlteata Pease. 1869, Am. Jour. Conchology, v. 5, p. 72. 

Rissoina multozona Tomlin, 1915, Jour. Conchology, v. 14, p. 321.

Small, slender, sides of spire nearly flat; protoconch 

of two smooth whorls followed by about six sculptured 

whorls; early whorls flat sided, ultimate and penultimate 

whorls may be gently convex; suture impressed; aperture 

small, lenticular with three (rarely four or five) low 

nodes inside outer lip; anterior channel narrow, moderately deep; outer lip varicose behind peristome. Sculpture consisting of fairly close-set axial ribs (about 19 on 

body whorl), crossed by slightly less conspicuous spiral 

ribs I about 7 on body whorl ( ; rib intersections beaded; 

siphonal fasciole with fine close-set spirals. Figured 

specimen shows a yellow spiral band immediately above 

the suture (a similar band on living shells is reddish 

brown (.

Measurements of the figured specimen (pi. 13, figs. 5, 

6) from Recent sediment (drill hole 2, Bikini, 38-40 ft), 

USNM 648394: height 3.7 mm, diameter 1.4 mm; (pi. 

13, figs. 7, 8) from Tertiary / (drill hole E-l, Eniwetok, 

880-890 ft), USNM 648395: height 3.7 mm, diameter 

1.4 mm.

Occurrence: In many drill holes on Bikini and Eniwetok Atolls, from surface to 1,541 feet (70 lots totaling 

some 200 specimens); age, Recent to early Miocene 

(Tertiary e}. The Tertiary specimens seem, on the average, to have less well-developed spiral sculpture, flatter 

sides, and larger apertures, but these features are variable. Pease described the Recent shell from Hawaii where 

it occurs in great abundance. Living examples are rare 

in the Marshall Islands; also know from Tahiti in the 

Society Islands.

As pointed out by Tomlin, this species may be identical with the Recent shell described by Pease as Rissoina 

costulata from the Tuamotu [Paumotu] Islands. The 

very small aperture noted by Pease is certainly suggestive, but Pease located the brown band on the middle 

of the whorls. R. cerithiformis Dunker, a Recent species 

reported from the Red Sea to Hawaii, apparently is identical with R. balteata.

Rissoina (Phosinella) bikiniensis Ladd, n. sp. 

Plate 13, figures 9, 10, 17, 18

Medium in size, slender, protoconch of three smooth 

whorls, the lowest of which is convex; seven or eight 

subsequent whorls all flattened; suture impressed; aperture broadly lenticular with three or four rounded nodes 

inside outer lip; posterior angle acute, anterior channel 

narrow and deep; outer lip slightly or moderately varicose. Sculpture consisting of strong axial ribs (about 23 

on body whorl) crossed by broad close-set spirals (9 on 

the body whorl, 4 on penultimate whorl) that form beads 

on axial ribs. Spiral sculpture not equally developed on 

all specimens.

Measurements of the holotype (2A, Bikini, 1,056- 

1,063 ft), USNM 648396: height 4.9 mm, diameter 1.6 

mm. Paratype (E-l, Eniwetok, 1,746-1,777 ft), USNM 

648400: height 3.6 mm, diameter 1.4 mm.

The Eniwetok specimens have a mode deeply impressed 

suture and a more prominent siphonal fasciole than those 

from Bikini, and they lack apertural nodes. They may 

represent a distinct species.

R. bikiniensis is larger but more slender than R. 

balteata Pease; it has more numerous whorls and a 

deeper anterior channel.

Occurrence: Three specimens from Miocene beds in 

drill hole 2A on Bikini Atoll: one from a depth of 490 

feet (core) is Tertiary g; two others from cuttings at 

lower levels (1,030-1,063 ft) are referred to Tertiary /. 

Three specimens from drill hole E-l, Eniwetok are from 

Tertiary / (960-970 ft) and Tertiary e (1,746-1,777 ft).

Rissoina (Phosinella) transenna Watson 

Plate 13, figures 11, 12

Rissoina transenna Watson, 1886, Challenger Kept., v. 15, p. 620,

pi. 46, fig. 10. 

Tryon, 1887, Manual Conchology, v. 9, p. 382, pi. 58, fig. 10.

Small, slender, stout; protoconch of about two smooth 

convex glassy whorls followed by six sculptured whorls; 

aperture lenticular, posterior angle acute, anterior channel broad and deep, outer lip thickened into a heavy 

varix. Sculpture reticulate, strong axial ribs (about 16 

on last whorl) crossed by equally prominent spirals of 

which there are 7 or 8 on the body whorl (lowest one on 

some specimens smaller than others) and 4 or 5 exposed 

on the penultimate whorl, all intersections beaded; 

siphonal fasciole heavy and conspicuously beaded.
70 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Measurements of the figured specimen (hole Mu-4, 

Eniwetok Atoll, at 40 ftl, USNM 648397: height 3.6 mm, 

diameter 1.5 mm.

Occurrence: In drill holes on Eniwetok (46 specimens) 

and Bikini (6 specimens I from near the surface to a depth 

of 873 feet; age, Recent to early Miocene (Tertiary /).

The fossils placed here are somewhat variable. Many 

specimens from levels below 200 feet have fewer axial 

ribs. They do not show the subsutural threadlet described 

by Watson on the type specimen, a Recent shell from 

Fiji.

Rissoina (Phosinella) alexisi Ladd, n. sp. 

Plate 13, figures 13-16

Small, stout; protoconch of 21/i>-3 smooth convex 

whorls followed by about five sculptured whorls that 

may be slightly turreted; suture deeply impressed, aperture broadly lenticular, posterior angle acute, anterior 

channel broad and moderately deep, outer lip thickened. 

Sculpture reticulate, strong axial ribs (13-15 on last 

whorl) crossed by weaker (spirals (5-6 on last whorl), 

intersections beaded; siphonal fascicle moderately 

strong, beaded.

Measurements of the holotype, USNM 648398: height 

2.7 mm, diameter 1.1 mm. Paratype, USNM 648399: 

height 2.5 mm, diameter 1.0 mm.

Occurrence: Holotype from drill hole F-l, Eniwetok 

Atoll, at depth of 1,110-1,120 feet. Paratype A from 

same hole at depth of 1,100-1,110 feet; both early 

Miocene (Tertiary e). Two other specimens recovered 

from K^IB at depths of 863-1,000 feet; age, Tertiary /.

Subgenus RISSOINA s.s.

Type (by monotypy): Rissoina inca d'Orbigny. Recent, Pacific coast of South America.

Includes species with heavy axial ribs and fine spiral 

threads; the outer lip is thickened; a siphonal fascicle is 

not developed but the anterior channel deeply undercuts 

the columella.

Rissoina (Rissoina) abbotti Ladd, n. sp.

Plate 13, figures 19-21

Small to medium in size, stout; protoconch not preserved; about seven subsequent whorls, gently convex, 

suture impressed; aperture irregularly lenticular; posterior channel narrow; anterior channel broad and deep, 

undercutting the base of the columella; peristome heavily 

callused, outer lip thickened. Sculpture consisting of 

numerous curved axial ribs (25 or more on last whorl I, 

crossed by fine close-set spirals; on lower half of body 

whorl the intersections are conspicuously beaded.

Measurements of the holotype (drill hole 2A, Bikini, 

1,061-1,067 ft), USNM 648371: height (protoconch missing) 4.9 mm, diameter 2.1 mm. Measurements of the 

paratype (Palau, USGS 21301) USNM 648372: height 

(protoconch missing) 8.1 mm, diameter 3.0 mm.

Characterized particularly by its strong curved axial 

ribs and well-developed spiral striae. The single specimen from Palau is larger than the Marshall Island specimens, but in all other respects it is identical with them.

Occurrence: Two specimens from drill hole 2A, Bikini 

Atoll, at depths of 956-1,067 feet (Miocene, Tertiary / 

and g); six specimens from drill holes F-l and K-1B, 

Eniwetok Atoll, at depths of 790-963 feet (Miocene, 

Tertiary / and g ); one specimen from the marl at the 

base of the Palau Limestone northwest of Goikul, Babelthuap, Palau (USGS 21301); (late Miocene, Tertiary g}.

Rissoina (Rissoina) mijana Ladd, n. sp.

Plate 13, figures 22-25

Medium in size with short spire and large body whorl; 

about five gently convex whorls but may be flattened 

near suture which is but little impressed; aperture broadly 

lenticular, posterior channel shallow, anterior channel 

broad and moderately deep, undercutting the columella; 

outer lip thickened. Sculpture consisting of moderately 

strong curved axial ribs and numerous spiral threads, 

which are most conspicuous on lower half of body whorl. 

Axial ribs smaller and more numerous on the body whorl 

than on earlier whorls (about 30 on body whorl, 22 or 

more on penultimate whorl).

Measurements of the holotype (pi. 13, figs. 24, 25), 

USNM 648374: height (incomplete) 4.3 mm, diameter 

1.8 mm.

Occurrence: Holotype from drill hole E-l on Eniwetok 

Atoll at a depth of 880-890 feet; another specimen from 

E-l at depth of 890-900 feet; a third specimen was obtained from drill hole 2A on Bikini at 1,040-1,046 feet; 

age of all three early Miocene (Tertiary /). A specimen 

from beds of the same age in K-1B (pi. 13, figs. 22, 23) is 

assigned R. mijana with reservations. It is more slender 

than the other specimens and has flatter whorls and more 

numerous axial ribs.

Rissoina (Rissoina) ailinana Ladd, n. sp.

Plate 13, figure 26

Small, stout; protoconch of two smooth strongly convex whorls; four to five slightly convex subsequent 

whorls; aperture broadly lenticular, posterior angle acute, 

anterior channel moderately wide and deep, undercutting 

the columella; outer lip thickened without and heavily 

callused within, the callus rising to form a low protuberance near the posterior angle. Sculpture consisting of
PALEONTOLOGY 71

about 20 strong axial ribs on body whorl and fine spiral 

lines that are visible only under magnification.

Measurements of the holotype (E-l, Eniwetok, 1,925- 

1,955 ft), USNM 648375: height 3.0 mm, diameter 1.3 

mm.

R. ailinana is characterized particularly by the small 

number of post-nuclear whorls (four to five) and by the 

low knob of callus inside the outer lip near the posterior 

angle.

Occurrence: In drill holes F-l, and E-l on Eniwetok 

Atoll at depths of 1,925-2,720 feet (10 specimens) and 

in drill hole 2B on Bikini at 1,724-1,975 feet (3 specimens) ; all occurrences early Miocene (Tertiary e].

Rissoina (Rissoina) lomaloana Ladd, n. sp. 

Plate 13, figures 27, 28

Small, moderately slender; protoconch of two smooth 

convex whorls followed by about six gently convex subsequent whorls; suture but little impressed; aperture semicircular, posterior angle acute; anterior channel moderately deep, undercutting the base of the columella; inner 

lip callused, outer lip callused within and thickened into 

a varix immediately behind the peristome. Sculpture 

consisting of close-set axial ribs (about 29 on body 

whorl) and numerous fine spiral lines.

Measurements of the holotype (drill hole K-1B, Eniwetok, 842-852 ft), USNM 648376: height 4.1 mm, diameter 1.5 mm.

Occurrence: Seven specimens from two deep drill holes 

on Eniwetok Atoll at depths of 695-890 feet; single specimen in drill hole 2A on Bikini at 978-988 feet; age, 

Miocene (Tertiary j-g ).

Rissoina (Rissoina) goikulensis Ladd, n. sp. 

Plate 13, figure 29

Small, stout; protoconch of two smooth convex whorls 

followed by about six gently convex sculptured whorls; 

suture strongly impressed; aperture broadly lenticular; 

posterior angle rounded, anterior channel shallow; outer 

lip slightly thickened with low nodes inside. Sculpture 

consisting of 20 narrow axial ribs on last whorl, crossed 

by a few spirals on lower half of body whorl.

Measurements of the holotype, USNM 648377: height 

3.7 inin, diameter 1.3 mm.

II. goikulensis resembles R. ailinana from the early 

Miocene of Bikini and Eniwetok but has more numerous 

whorls, a more sharply incised suture, and a shallower 

anterior channel.

Occurrence: Three specimens from the marl at the 

base of the Palau Limestone on Goikul Peninsula, Babelthuap Island. Palau (USGS 213041; age, late Miocene 

(Tertiary g \.

Rissoina (Rissoina) waluensis Ladd, n. sp. 

Plate 13, figure 30

Small, stout; protoconch of about three smooth convex whorls followed by about six flat-sided sculptured 

whorls; suture impressed; aperture lenticular, posterior 

angle acute; anterior channel broad and moderately deep, 

undercutting the columella; outer lip with two obscure 

elongate nodes within, slightly thickened behind. Sculpture consisting of about 20 slightly oblique axial ribs on 

the last whorl, crossed by a few spirals; intersections 

beaded.

Measurements of the holotype, USNM 648378: height 

3.8 mm, diameter 1.5 mm.

R. waluensis has whorls that-arc more flat sided than 

those of R. ailinana from the early Miocene of Bikini and 

Eniwetok, and it has stronger spiral sculpture than that 

species.

Occurrence: Holotype and four other worn specimens 

from conglomerate layer at base of reef limestone in 

Suva Formation, Walu Bay, Suva, Fiji (sta. 160). Paratype and two other specimens from FB-20 (virtually 

same locality as sta. 160); age, early Miocene (Tertiary 

/> 

Rissoina (Rissoina) ekkanana Ladd, n. sp. 

Plate 13, figures 31, 32

Small, slender; protoconch of l1/^ smooth bulbous 

whorls coiled at an angle with the axis of the spire and 

about six sculptured gently convex subsequent whorls; 

suture impressed; aperture lenticular, posterior angle 

acute, anterior channel broad and moderately deep, 

slightly undercutting the columella; edge of outer lip 

thin but thickened slightly behind. Sculpture consisting 

of strong widely spaced axial ribs, about 14 on body 

whorl, and spiral lines that are especially prominent on 

the lower part of the last whorl.

Measurements of the holotype, USNM 648379: height 

3.2 mm, diameter 1.2 mm.

Occurrence: Forty eight shells from five drill holes on 

Eniwetok Atoll at depths to 110 feet (holotype from 

Mu-4 at 35 ft) ; age, Recent.

Rissoina (Rissoina) ambigua (Gould) 

Plate 14, figures 23, 24

Pyramidella ambigua Gould, 1849, Boston Soc. Nat. History

Proc. v. 3, p. 118 [1851].

Johnson, 1964, U.S. Natl. Mus. Bull. 239, p. 39. 

Rissoa ambigua Gould, 1852, U.S. Explor. Exped., Mollusca, p.

217, pi. 15, pi. 261a-c. 

Rissoina ambigua (Gould), Tryon, 1887, Manual Conchology, v.

9, p. 371, pi. 55, figs. 27, 29, 31, 35; pi. 54, fig. 7. 

Hedley. 1899. Australian Mus. Mem. 3, pt. 7. p. 422. 

Rissoina materinsulae Pilsbry, 1904, Acad. Nat. Sci. Philadelphia

Proc., p. 27, pi. 5, figs. 43, 43a.
72 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Large, elongate-conic, thick, milk white; protoconch 

o'f 21/£ rounded smooth whorls; seven subsequent whorls, 

those above the body whorl showing a weak shoulder 

immediately below the suture; body whorl flattened, 

suture impressed. Aperture irregularly lenticular, inner 

lip concave, anterior channel deep, undercutting columella to form a rounded toothlike projection, outer lip 

thickened. Sculpture consisting of fine close-set axial 

ribs (more than 20 on body whorl, including 3 on thickened outer lip! and weak spirals that are limited to the 

base of the body whorl, below the posterior angle of the 

aperture.

Measurements of the figured specimen, USNM 648423 

(Recent, Rujiyoru, Eniwetok): height 6.4 mm, diameter 

2.3 mm. A fossil specimen from hole 1, Bikini, 5-10 feet, 

USNM 648424: height 6.4 mm, diameter 2.2 mm.

R. ambigua is characterized particularly by its elongate-conic form.

Occurrence: Originally described from the Tuamotu 

[Paumotuj Islands but later widely reported from the 

Indo-Pacific (Hawaii, Ellice Islands, Society Islands, 

Fiji, New Caledonia, New Guinea, Singapore, Ceylon, 

Mauritius, and Japan*. Figured specimen and one other 

Recent shell from the island of Rujiyoru, Eniwetok 

Atoll. Recent shells were also collected at other localities on Eniwetok and on the nearby atolls of Bikini, 

Rongerik, and Rongelap. Three fossil specimens were 

found in shallow drill holes on Eniwetok and Bikini at 

depths to 10 feet; all Recent in age.

Rissoina (Rissoina) ambigua parryensis Ladd, n. subsp. 

Plate 14, figures 25, 26

Large, elongate-conic, thick, whorls flattened; protoconch consisting of about two smooth whorls; seven subsequent whorls; suture not impressed. Aperture subsemicircular, inner lip concave, anterior channel deep, undercutting columella to form a rounded toothlike projection, 

outer lip thickened. Axial sculpture consisting of fine 

close-set ribs (37 on body whorl); spiral sculpture absent.

Measurements of the holotype, USNM 648425: height 

(protoconch incomplete! 6.8 mm, diameter 2.3 mm.

R. ambigua parryensis may be ancestral to the Recent 

shell. The new subspecies has more numerous axial ribs, 

lacks spiral sculpture, and its suture is less impressed.

Occurrence: Single specimen from drill hole E-l, Eniwetok, at depth of 620-630 feet in beds referred to late 

Miocene (Tertiary g).

Rissoina (Rissoina) concinna A. Adams 

Plate 13, figure 33

Rissoina concinna A. Adams, 1851, Zool. Soc. London Proc., p.

266. 

Tryon, 1887, Manual Conchology 9, p. 386, pi. 58, fig. 18.

Medium in size, slender, thick; protoconch not preserved; about six subsequent whorls, the earlier ones 

flattened, the later ones slightly convex; suture impressed; 

aperture semicircular, posterior angle acute, excavated 

to form a shallow channel; anterior channel broad and 

fairly deep, undercutting the columella; inner and outer 

lips heavily callused, outer lip thickened. Sculpture consisting of prominent slightly oblique axial ribs (about 29 

on body whorl ( ; fine spiral lines are limited to the lower 

part of the body whorl near the aperture.

Measurements of the figured specimen (drill hole E-l, 

Eniwetok, 970-980 ft) USNM 648380: height (incomplete) 6.4 mm, diameter 2.3 mm.

Occurrence: Two specimens from deep drill holes on 

Eniwetok at depths of 970-980 feet in beds referred to 

Miocene (Tertiary /). In drill hole 2A on Bikini, a single 

specimen from a depth of 852-857 feet; age late Miocene 

(Tertiary g ) ; a single specimen from 2B at a depth of 

1,020-1,100 feet is early Miocene in age (Tertiary /); 

one from 1,671-1,682 feet is in beds referred to Tertiary 

e.

The Recent shells described by Adams were collected 

in the Philippines.

Rissoina (Rissoina) sp. A 

Plate 13, figures 34, 35

A single imperfect specimen of a distinctive species of 

Rissoina s.s. was collected from the Suva Formation in 

its type section on ^Walu Bay, Fiji (sta. 160); age 

Miocene (Tertiary /). The shell differs from other fossil 

Rissoinas from the island area in that its flattened 

whorls and unimpressed suture give the spire an overall 

convex outline. The narrow close-set ribs of each whorl 

are alined with those of the adjoining whorl; about 30 

ribs are on the last whorl, 25 on the penultimate. Measurements of the single specimen, USNM 648381: height 

(apex missing) 4.8 mm, diameter 1.7 mm.

Rissoina sp. A resembles Rissoina concinna from beds 

of about the same age in the Marshall Islands, but its 

axial ribs are more nearly vertical, and it lacks spiral 

sculpture.

Subgenus RISSOLINA Gould

Gould, 1861, Boston Soc. Nat. History Proc., v. 7, p. 401.

Type (by subsequent designation, Nevill, 1885, Hand 

list Mollusca Indian Mus., pt. 2, p. 73, 77) Rissoina plicatula Gould, Recent, western Pacific.

Characterized particularly by a strong siphonal fasciole.

Rissoina (Rissolina) turricula Pease 

Plate 13, figures 36, 37

Rissoina turricula Pease, 1860, Zool. Soc. London Proc., p. 438. 

Tryon, 1887, Manual Conchology, v. 9, p. 377, pi. 56, fig. 63.
PALEONTOLOGY 73

Small, stout, whorls convex, distinctly angled above; 

aperture ovate, slightly flattened below; anterior channel broad and deep; sculpture consisting of strong axial 

ribs, 11 or 12 on body whorl; spaces between ribs finely 

striate.

Measurements of figured specimen (F-l, Eniwetok, 

20-45 ft), USNM 648407: height 2.7 mm, diameter 1.0 

mm.

Occurrence: Nine specimens from Recent sediments in 

six drill holes at Eniwetok; greatest depth, 70-80 feet in 

hole E-l on Parry Island; figured specimen from depth 

of 20-45 feet in hole F-l on Elugelab; a single specimen 

from drill hole K-1B at depth of 968-978 feet is from 

early Miocene (Tertiary /1; a broken but otherwise 

fresh-looking specimen from drill hole 2B on Bikini at 

a depth of 1,335-1,345 feet (Tertiary e) may have been 

derived from a higher level; four specimens were collected from the Suva Formation, Viti Levu, Fiji (sta. 

FB-20); age, Miocene (Tertiary /) and one from the 

Ndalithoni Limestone, Vanua Mbalavu, Fiji (sta. HOB); 

age, probably Pliocene (Tertiary h).

The species was originally described as a Recent shell 

from Hawaii; later reported from Fiji, Ceylon, and 

Mauritius; also found at Bikini (reef-flat drift) and 

other atolls in the northern Marshalls by J. P. E. Morrison.

Rissoina (Rissolina) marshallensis Ladd, n. sp. 

Plate 13, figures 38-40; Plate 14, figures 1-4

Small to medium, robust; protoconch of two smooth 

convex whorls followed by five to six sculptured whorls 

that are uniformly convex or slightly angled above; 

aperture subseinicircular, inner lip gently convex, outer 

lip thickened, posterior angle acute, anterior channel 

broad and moderately deep. Sculpture consisting of 

strong axial ribs (12-19 on body whorl) separated by 

wide interspaces that may be nearly smooth or heavily 

striate. Siphonal fascicle conspicuously beaded; on some 

shells it is sharply elevated, on others it is not distinctly 

set off from the remainder of the whorl.

The measurements of the holotype and five paratypes 

selected to illustrate the variation in size, profile of 

whorls, development of siphonal fascicle, and spiral 

sculpture, are given in the following table.

Specimen

Holotype USNM 648408- - .

Paratype A, USNM 648409. _

Paratype B, USNM 648410.

Paratvpe C, USNM 648411 .... _

Paratype D, USNM 648412.

Paratype E, USNM 648413..

Drill 

hole

K-1B

E-l

K-1B

K-1B

K-1B

2B

Depth

(feet)

894-905

850-860

1,049-1,060

842-852

uQfi_Q47

1,020-1,100

Height

(mm)

5.0

'3.8

7.4

4.2

3.8

5.2

Diameter 

(mm)

1.9

1.5

2.7

1.6

1.5

2.1

Profile 

of whorls

Slightly

turreted. 

Strongly

turreted. 

Not

turreted. 

Slightly

turreted. 

..-.do....

Not

turreted.

Siphonal 

fascicle

Strong

-__-do_-_.

__-_do-__.

Weak

....do....

____do.__-

Spiral 

threads

Weak.

Absent.

Strong.

..._do-_-

Weak.

Strong.

1 Incomplete.

R. marshallensis appears to be an exceedingly variable 

species. It is closely related to the Recent R. turricula 

Pease but is larger, has sharper and (on the average) 

more numerous ribs. R. turricula may have developed 

from R. marshallensis; in drill holes on Eniwetok where 

both occur there is a stratigraphic gap of nearly 600 feet 

between known occurrences of the two.

R. semari Beets from the late Miocene of East Borneo 

is larger than the Marshall Island fossil and does not 

have a strongly beaded siphonal fasciole.

Occurrence: An abundant species in the Miocene beds 

beneath Eniwetok and Bikini. Sixty-one lots were recovered from cuttings in three drill holes on Eniwetok 

(E-l, F-l, K-1B) at depths of 620-1,715 feet; age,

Tertiary e-g. Nine lots were collected from two drill 

holes on Bikini (2A and 2B) at depths of 904-1,088 feet; 

Tertiary f-g. (One Bikini specimen from core at 936 ft).

Rissoina (Rissolina) ephamilla Watson 

Plate 14, figures 5-8, 11, 12

Rissoina ephamilla Watson, 1886, Challenger Rept. 15, p. 617

[R. scalariformis], p. 719, pi. 46, fig. 6. 

Rissoina scalariformis Watson, Tryon, 1887, Manual Conchology,

9, p. 378, pi. 54, fig. 1.

Very small, slender, polished; protoconch of 

whorls; later whorls about 5, uniformly convex or turreted; aperture semilunate, outer lip oblique with thick 

varix; siphonal fasciole heavy and beaded; anterior chan-
74 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

nel broad and shallow7 . Sculpture consisting of strong 

slightly oblique axial ribs (12-16 on last whorl), the 

spaces between smoothly polished or showing faint traces 

of spiral striae.

Measurements of figured specimen from Eniwetok (pi. 

14, figs. 5, 6) USNM 648414: height 3.0 mm, diameter

I.2 mm. Figured specimen from Bikini (pi. 14, figs. 7, 8), 

USNM 648415: height 2.9 mm, diameter 1.1 mm. An 

unusually slender specimen from Eniwetok (pi. 14, figs.

II, 12) USNM 648417: height 3.0 mm, diameter 0.8 mm.

Easily distinguished by its slenderness from most other 

species of Rissolina in the Marshall Island area.

Occurrence: In all three deep holes on Eniwetok (30 

specimens) at depths of 212-1,029 feet; age, Recent to 

early Miocene (Tertiary /); a single Recent specimen 

was also recovered from one of the shallow holes on Eniwetok (Mu-4) from a depth of 26-27 feet. Two specimens from hole 2B on Bikini Atoll at a depth of 447-464 

feet are post-Miocene in age. The Recent shells described by Watson were collected from the reefs off 

Honolulu at a depth of 40 fathoms.

Rissoina (Rissolina) kickarayana Ladd, n. sp. 

Plate 14. figures 9, 10

Small, slender; protoconch of two smooth whorls succeeded by about six gently convex slightly turreted and 

strongly ribbed later whorls; aperture semilunate, outer 

lip extended forward immediately above base and 

bordered by a heavy varix; siphonal fascicle inconspicuously beaded by extensions of axial ribs of body 

whorl; anterior channel broad and shallow. Sculpture 

consisting of strong erect slightly oblique axial ribs, 9-11 

on body whorl.

Measurements of the holotype (USGS 21301), USNM 

648416: height 4.1 mm, diameter 1.5 mm.

R. kickarayana is smaller and more slender than R. 

niarshallensis, from the Miocene of the Marshalls; its 

axial ribs are more oblique and fewer in number.

Occurrence: In the late Miocene marls at the base of 

the Palau Limestone near Goikul, Babelthuap Island, 

Palau (in great abundance at USGS 21301 and 21304; 

single specimen at 21308 L

Rissoina (Rissolina) herringi Ladd, n. sp. 

Plate 14, figures 13, 14

Small, slender; protoconch of smooth convex whorls, 

coiled at a slight angle to the axis of the spire, followed 

by 61/2 gently convex sculptured whorls; aperture lenticular, posterior angle acute, anterior channel broad 

and moderately deep, slightly undercutting the columella; 

outer lip thickened. Sculpture consisting of axial ribs 

(about 20 on last whorl) and fine spiral striae; spirals

best developed on flattened triangular area lying adjacent to edge of inner lip; siphonal fascicle low, not 

sharply set off from remainder of whorl.

Measurements of the holotype, USNM 648418: height 

4.8 mm, diameter 1.8 mm.

Occurrence: Four specimens from drill holes F-l and 

E-l, Eniwetok Atoll, at depth of 710-860 feet (holotype 

from F-l, 710-720 ft) ; age, late Miocene (Tertiary g).

Rissoina (Rissolina) harti Ladd, n. sp. 

Plate 14, figures 15, 16

Very small, stout; protoconch of 1% smooth convex 

whorls, followed by about six convex sculptured whorls; 

body whorl slightly flattened in profile with a weak 

shoulder that extends forward from the posterior angle 

of the aperture; suture impressed; aperture broadly lenticular, posterior channel narrow and shallow, anterior 

channel shallow and indistinct. Sculpture consisting of 

strong slightly oblique axial ribs, 17-20 on body whorl; 

spiral striae weakly developed on body whorl; siphonal 

fascicle low, not sharply set off from rest of whorl.

Measurements of the holotype (2B, Bikini, 1,555-1,566 

ft) USNM 648419: height 3.2 mm, diameter 1.3 mm.

Occurrence: Five specimens from drill hole 2B on 

Bikini Atoll at a depth of 1,429-1,829 feet; age, early 

Miocene (Tertiary e].

Rissoina ( Rissolina ) bourneae Ladd, n. sp. 

Plate 14, figures 17, 18

Small, stout; protoconch of three smooth rounded 

whorls, followed by about five gently convex weakly 

shouldered sculptured whorls; aperture lenticular; outer 

lip thickened and extended forward; posterior angle 

acute, anterior channel broad, undercutting the columella. 

Sculpture consisting of strong oblique slightly curved 

axial ribs, 15-19 on last whorl; siphonal fasciole thick 

and beaded, separated from the remainder of whorl by a 

broad depression.

Measurements of the holotype from FB-20, USNM 

648420: height 3.2 mm, diameter 1.2 mm.

R. bourneae resembles R. kickarayana Ladd, a species 

of about the same age occurring in Palau, but the Fijian 

shells are smaller and have more numerous axial ribs.

Occurrence: Represented by a dozen specimens from 

the conglomerate layer at the base of the reef limestone 

in the Suva Formation, Walu Bay, Suva, Fiji (stas. 

FB-20 and 160); age, early Miocene (Tertiary /).

Rissoina (Rissolina) plicata A. Adams 

Plate 14, figures 21, 22

plicata A. Adams, 1851, Zool. Soc. London Proc., p. 264. 

Tryon, 1887, Manual Conchology 9, p. 375, pi. 56, figs. 58-60, 

68; pi. 54, fig. 8.
PALEONTOLOGY 75

Shell large, heavy, thick, with strong widely spaced 

axial ribs, 10 on the last whorl and fine spiral striae. 

The siphonal fascicle is heavy, strongly elevated, and is 

smooth or weakly beaded by the axial ribs. Aperture 

lenticular, anterior channel broad and fairly deep, 

undercutting the columella.

Measurements of the figured specimen (F-l, Eniwetok, 

870-880 ft), USNM 648422: height (apex missing) 6.9 

mm, diameter 3.0 mm.

Occurrence: Two specimens from drill hole F-l on 

Eniwetok Atoll at depth of 870-950 feet; age, early 

Miocene (Tertiary /).

Described from Recent shells from Philippines; also 

known from Samoa, Cook Islands, Fiji, Red Sea, and 

Mauritius.

Rissoina (Rissolina) sp. B 

Plate 14, figures 19, 20

Small, stout; with strong curved axial ribs, 21 on body 

whorl; aperture semioval, outer lip thickened, anterior 

channel broad and deep; spiral striae, weak on early 

whorls, more prominent on last whorl, dominating the 

axials on the lower half of that whorl; siphonal fascicle 

low, faintly beaded.

Measurements of the figured specimen, USNM 648421: 

height (apex missing) 3.9 mm, diameter 1.6 mm.

Rissoina (Rissolina) sp. B differs from R. bourneae 

in that it has stronger spiral sculpture, more strongly 

curved axial ribs, and a smoother siphonal fascicle.

Occurrence: Two incomplete specimens from station 

165, west of Nasongo, Viti Levu, Fiji; age, probably 

Miocene.

Genus BARLEEIA W. Clark 

Clark, 1853, Annals and Mag. Nat. History, 2d ser. v. 12, p. 108.

Type (by monotypy) : Rissoa rubra A. Adams. Recent, 

Atlantic.

Subgenus BARLEEIA s.s.

Minute, smooth, imperforate shells with blunt apex 

and large body whorl.

Barleeia (Barleeia) meiauhana Ladd, n. sp.

Plate 14, figure 27

Minute, ovate, apex blunt; about four whorls, inflated, 

smooth; suture impressed; aperture broadly oval, entire, 

slightly constricted, narrowed above, broadly rounded 

below; lips sharp.

Measurements of the holotype, USNM 648426: height 

0.9 mm, diameter 0.6 mm.

B. meiauhana is much smaller and proportionately 

wider than the type species, B. rubra (Adams). The 

Palau fossil more closely resembles B. carpenten Bartsch,

a Recent species from Baja California, but that form 

has flattened slightly shouldered whorls.

Occurrence: Seven specimens from late Miocene (Tertiary g] marls at base of Palau Limestone on Goikul 

Peninsula, Babelthuap Island, Palau (USGS 21301).

Family ASSIMINEIDAE 

Genus ASSIMINEA Fleming

Fleming, 1828, History of British animals, v. 5, p. 275.

Type (by monotypy): Assiminea gray ana Fleming. 

Recent, England.

Assiminea nitida eniwetokensis Ladd, n. subsp.

Plate 10, figure 8

Small, spire low, apex blunt, robust; four to five whorls, 

smooth, gently and uniformly convex; suture lightly impressed; aperture broadly ovate, peristome not continuous, inner lip callused, slightly flaring below, with a 

groove behind it in the umbilical region; outer lip thin. 

The holotype and some other specimens show an obscure 

thread below the suture.

Measurements of the holotype (K-1B, Eniwetok, 831- 

842 ft), USNM 648325: height 1.8 mm, diameter 1.3 mm.

The Marshall Island fossils have been compared with 

the cotypes of the Recent A. nitida (Pease, 1864, p. 674, 

as Hydrocena nitida} from the Society Islands (USNM 

591317) and with examples of many of the numerous 

subspecies that have been recognized from island groups 

in the southwest Pacific (Abbott, 1958). A. nitida eniwetokensis is smaller than A. nitida nitida, has fewer 

whorls, and the base of the body whorl is more uniformly 

rounded. The fossils have also been compared with the 

types and other specimens of A. nitida marshallensis 

Abbott (1958, p. 256) collected at Eniwetok and at other 

atolls in the Marshall group. The same differences in 

size and curvature of the body whorl are apparent, and 

the fossils are proportionately much shorter than adults 

of the elongate Recent shell. The fossil is represented by 

a total of 26 specimens all of which are small but some 

of which certainly are adults.

Assiminea nitida eniwetokensis belongs to a group of 

small amphibious air-breathing snails that has representatives living in the area today (Abbott, 1958).

Occurrence: Twenty-six specimens from deep holes 

(E-l and K-1B) on Eniwetok Atoll at depths of 710- 

842 and 1,835-1,993 feet; and one specimen from Bikini 

(2B, 1,713-1,724 ft) ; age, Miocene (Tertiary e and g\ no 

specimens recovered from beds assigned to Tertiary /).

Family ADEORBIDAE (VITRINELLIDAE) 

Genus HAPLOCOCHLIAS Carpenter

Carpenter, 1864, Annals and Mag. Nat. History, 3d ser., v. 13, p. 

476.
76 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Type (by monotypy): Haplocochlias cyclophoreus 

Carpenter. Recent, west coast of Mexico.

Haplocochlias sp. A

Plate 14, figures 28, 29

Minute, inflated, naticoid in general outline; aperture 

subcircular, peristome continuous, outer lip thickened; 

umbilicus wide, bordered by a smooth ridge. Sculpture 

consisting of fine spiral striae.

Measurements of the figured specimen, USNM 648427: 

height 1.2 mm, diameter 1.1 mm.

This rare shell is unusual in that it combines the general outline of a naticid with a thickened outer lip that 

is suggestive of a rissoid. The single Eniwetok fossil appears to be closely related to the type species H. cyclophoreus Carpenter, a Recent species described from 

Cabo San Lucas at the southern tip of Baja California 

and reported also from Bahia Magdalena, 175 miles to 

the northwest. Carpenter's type lot of specimens (USNM 

18112) contains three large shells (the largest measuring 4.5 mm in height and 5.1 mm in diameter) and one 

minute shell (height 1.3 mm, diameter 1.4 mm) that he 

regarded as a juvenile. The Eniwetok fossil resembles 

the smallest specimen in the type lot, but the two are 

not conspecific because the Recent shell is thicker, more 

coarsely striated, has a weaker umbilical ridge, and a 

less well developed varix on the outer lip. It is possible 

that the minute shell in the type lot is specifically distinct 

from the larger shells.

Occurrence: Single specimen from drill hole K-1B on 

Eniwetok Atoll at a depth of 831-842 feet; age late 

Miocene (Tertiary g).

Genus LEUCORHYNCHIA Crosse

Crosse, 1867, Jour, conchyliologie, 15, p. 319.

Type (by monotypy): Leucorhynchia caledonica 

Crosse. Recent, New Caledonia.

Leucorhynchia caledonica Crosse 

Plate 14, figures 30, 31

Leucorhynchia caledonica Crosse, 1867, Jour. Conchy liologie, v.

15. p. 319, pi. 11, fig. 4. 

Teinostoma (Leucorhynchia) caledonicum Crosse, Tryon, 1888,

Manual Conchology 10, p. 106, pi. 35, figs. 85, 86.

Small, lenticular, smooth, perforate; periphery carinate, the carina becoming obsolete near the circular aperture; peristome entire, its basal edge extended laterally 

to form a thick pad of callus that projects over the 

umbilicus but does not come in contact with it.

Measurements of the figured specimen (Eb-2, Eniwetok, 21-211/0 ft) USNM 648428: height 1.4 mm, 

diameter 2.5 mm.

Occurrence: From four drill holes on Eniwetok Atoll, 

from near the surface to depth of 60 feet (age, Recent) 

but not found living in the area today. The species was 

originally described from New Caledonia and has also 

been reported from Queensland, Australia (Cotton, 1959, 

p. 204).

All six fossil specimens are smaller than the Recent 

shells from New Caledonia.

Leucorhynchia crossei Tryon 

Plate 14, figures 32, 33

Teinostoma (Leucorhynchia) crossei Tryon, 1888, Manual 

Conchology 10, p. 106, pi. 35, figs. 86a, 86b.

As noted by Tryon in defining the species, it differs 

from the genotype L. caledonica only by having a 

rounded, instead of a carinated, periphery.

Measurements of the figured specimen (E-l, Eniwetok, 

35-40 ft), USNM 648429: height 1.2 mm, diameter 2.3 

mm.

Occurrence: From five drill holes on Eniwetok Atoll, 

from near the surface to depth of 55 feet (age, Recent) 

but not found living in the area today. Originally described from Singapore, later reported from northwestern 

Australia and the Arabian Sea.

Represented by 20 fossil specimens from 10 localities 

and horizons. All the fossils are smaller than the Recent 

shells but seem not to differ in other respects. L. crossei 

appears to be very closely related to L. Caledonia. The 

two should, perhaps, be combined though in the Eniwetok 

drill holes they were not found together in the same 

sample.

Leucorhynchia? stephensoni Ladd, n. sp. 

Plate 14, figures 34, 35

Minute; spire flattened, body whorl rapidly expanding, 

periphery broadly angled; perforate; aperture circular; 

peristome entire; expanded below to form a broad flattened callus that extends over the umbilicus and partially obscures it. Under magnification the sculpture is 

seen to consist of fine close-set spiral lines and a ring of 

short widely separated axial lines radiate from the umbilicus.

Measurements of the holotype, USNM 648430: height 

1.0 mm, diameter 2.0 mm.

The sculpture and the flattened spire distinguish this 

species from L. Caledonia and L. crossei which occur at 

higher, levels in Eniwetok drill holes.

Occurrence: Holotype, and only specimen, from drill 

hole K-1B on Eniwetok at a depth of 1,249-1,259 feet in 

sediments referred to early Miocene (Tertiary e].
PALEONTOLOGY 77

Leucorhynchia? lilli Ladd, n. sp. 

Plate 15, figures 1, 2

Small; spire low, body whorl rapidly expanding, 

periphery smoothly rounded; aperture circular, slightly 

constricted; peristome entire; umbilicus wide and deep, 

partially filled by a broad spiral rib. Sculpture consisting 

of fine close-set spiral lines over the entire shell, and, on 

the base, broad widely separated axials that are discernible only under magnification.

Measurements of the holotype, USNM 648432: height 

1.6 mm, diameter 3.1 mm.

L.? lilli resembles L.? stephensoni in sculptural features but has a more elevated spire and lacks the thick 

pad of callus that partially covers the umbilicus in that 

species; its reference to Leucorhynchia is even less certain than in the case of L.? stephensoni.

Occurrence: Single specimen from drill hole 1 on Bikini 

Atoll at a depth of 40 feet; age, Recent.

Genus LOPHOCOCHLIAS Pilsbry 

Pilsbiy, 1921, Acad. Nat. Sci. Philadelphia Proc., p. 377.

Type (by monotypy >: Haplocochlias minutissimus 

Pilsbry. Recent, Hawaii.

Lophocochlias minutissimus (Pilsbry) 

Plate 15, figures 3-5

Haplocochlias (Lophocochlias) minutissimus Pilsbry, 1921, Acad.

Nat. Sci. Philadelphia Proc., p. 377. 

Edmondston, 1946. B. P. Bishop Mus., Spec. Pub. 22, p. 165.

Minute, turbinate; apex sharp, made up of smooth 

whorls; body whorl descending at aperture, bearing six 

strong spiral keels, the upper three forming a prominent 

slightly curved peripheral zone; a weak keel lies between 

the suture and the uppermost strong keel; two cords 

spiral into the wide umbilicus; aperture subcircular and 

oblique; peristome entire, outer lip thickened into a 

strong varix that on some specimens is slightly back 

from the lip edge; regularly spaced oblique axial threads 

most conspicuous in the wide flat depressions between 

keels. Well-preserved fossils from Recent beds retain 

the brownish-yellow color of the apex that is so characteristic of living specimens; remainder of shell white.

Measurements of the figured specimen (E-l, Eniwetok, 

710-720 ft), USNM 648433: height 0.5 mm, diameter 

0.7 mm.

Occurrence: In describing this species as a Recent shell 

from Hawaii, Pilsbry noted that it was the smallest 

marine shell known to him from that area. It now has 

the added distinction of being the most widespread 

species both geographically and geologically in the

western Pacific island area.3 Recent shells have been 

collected from the Marshalls and from the Tuamotu 

Islands (Raroia) far to the southeast. Numerous fossils 

from Eniwetok and Bikini range downward to the lower 

Miocene (Tertiary e] at depth of 2,164 feet. In Fiji the 

species was found in abundance in the Suva Formation 

(sta. 160) on Viti Levu; age, Miocene (Tertiary /); 

single specimen from Tongatabu, Tonga (B. P. Bishop 

Mus., cat 202980, sta. 3), age probably Pleistocene.

Lophocochlias appears to be closely related to Lodderia 

Tate 1899, a genus represented by several species in the 

Recent fauna of the Australian region. Lophocochlias 

minutissimus exhibits variation in sculpture at each of 

the localities from which Recent or fossil shells have 

been obtained. Most of the numerous Fijian and Eniwetok fossils and some of the Recent shells from Raroia 

show an additional secondary keel between the uppermost two primary keels.

Lophocochlias paucicarinatus Ladd, n. sp.

Plate 15, figures 6-8

Minute, turbinate; apex sharp, consisting of smooth 

whorls; body whorl descending at aperture, bearing 

three low primary keels, the upper one giving the shell a 

turretecl appearance; obscure traces of secondary spirals 

are visible under high magnification, three on the base 

and one near the suture; umbilicus moderately wide, 

aperture subcircular, oblique; peristome entire, outer lip 

thickened into a strong varix that on one of the two 

available specimens lies a little back of the lip edge.

Measurements of the holotype, USNM 648434: height 

1.0 mm, diameter 1.2 mm.

L. paucicarinatus has fewer primary keels and a narrower umbilicus than L. minutissimus and lacks the 

axial sculpture of that species.

Occurrence: Two specimens from drill hole E-l on 

Eniwetok Atoll at a depth of 2,040-2,050 feet in beds 

assigned to lower Miocene (Tertiary e].

Genus MUNDITIELLA Kuroda and Habe

Kuroda and Habe, 1954, Venus, v. 18, no. 2, p. 86, 90-91.

Type (by original designation): Cyclostrema ammonoceras A. Adams. Recent, Japan.

Munditiella qualutn (Hedley) 

Plate 15, figures 9-11

Teinostoma qualum Hedley, 1899, Australian Mus. Mem. 3, pt. 

7, p. 406, fig. 2.

Small, depressed; spire nearly flat; width twice the 

height; suture impressed; aperture circular; peristome

3 1 have identified specimens from a well drilled on the coastal plain of 

Guadalcanal in the Solomon Islands (Baker, 1950). The shells were recovered 

from a depth of 380-400 feet. Foraminifera from the same beds are thought 

to be Pleistocene but possibly Pliocene (Ruth, Todd, oral commun., 1964).
78 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

complete, thin inner lip extended below; umbilicus 

moderately wide, deep. Sculpture consisting of regularly 

spaced sharply elevated axial ribs (about 20 on body 

whorl) with fine, close-set spiral lines developed in interspaces; fine axial threads that override the spirals can be 

seen under high magnification; body whorl flattened and 

free of axial ribs immediately below suture and around 

the umbilicus.

Measurements of the figured specimen from Eniwetok, 

USNM 648435: height 1.0 mm, diameter 2.0 mm.

M. qualum is smaller than the type species M. ammonoceras and has a more depressed spire.

Occurrence: Single specimens from drill hole F-l, Eniwetok Atoll, at depth of 280-290 feet, and Tongatabu, 

Tonga, at an altitude of 35 feet (B. P. Bishop Mus., cat. 

2029801 ; age of both occurrences probably Pleistocene. 

Abundant in beach drift on Rongerik Atoll. Hedley's 

types were collected from the lagoon shore of Funafuti, 

Ellice Islands.

Munditiella parryensis Ladd, n. sp. 

Plate 15, figures 12-14

Small, depressed; spire low, width more than twice the 

height; aperture circular, peristome complete; inner lip 

extended below; lower half of peristome thickened behind its edge by swellings at the ends of the spiral 

ridges; umbilicus wide and deep. Sculpture consisting 

of regularly spaced axial ribs (37 on body whorl) separated by wider interspaces bearing fine axial lines; spiral 

sculpture consisting of two obscure peripheral ridges, a 

third on the base, and a fourth that encircles the umbilicus; all ridges best developed on the anterior part of 

body whorl.

Measurements of the holotype, USNM 648436: height 

1.1 mm, diameter 2.6 mm.

M. parryensis has continuous axial ribs and a thickened peristome suggestive of M. archeri (Tryon, 1888, 

p. 89, pi. 33, figs. 84, 85, as Cyclostrema archeri), Recent 

species from Singapore, but that species has spiral lirae 

between the axial ribs.

Occurrence: Represented by three specimens from drill 

hole E-l on Parry Island, Eniwetok Atoll, at depths of 

35-40 (holotype), 750-760, and 850-860 feet; age of 

holotype, Recent; age of other two. late Miocene (Tertiary g). The two Miocene specimens are smaller than 

the holotype and appear to be immature.

Genus TEINOSTOMA H. and A. Adams 

H. and A. Adams, 1853, Genera Recent Mollusca 1, p. 122.

Type (by virtual monotypy): Teinostoma politum A. 

Adams. Recent, Ecuador.

Subgenus ESMERALDA Pilsbry and Olsson

Pilsbry and Olsson, 1952, Acad. Nat. Sci., Philadelphia Proc. 104, 

p. 37, 39.

Type (by original designation): Teinostoma esmeralda 

Pilsbry and Olsson. Recent, Ecuador.

Teinostoma (Esmeralda) engebiense Ladd, n. sp. 

Plate 15, figures 15-17

Small; spire depressed; body whorl inflated, its 

periphery uniformly rounded; imperforate; last whorl 

descending near aperture which is subcircular and 

slightly contracted; peristome entire, upper part of lip 

extended forward; umbilical area covered by thin callus. 

Sculpture consisting of numerous fine spiral lines that 

are distinguishable on all save the earliest whorls but 

are more widely spaced near the umbilicus than elsewhere.

Measurements of the holotype, USNM 648437: height 

2.4 mm, diameter 3.8 mm.

In size and shape, T. engebiense resembles T. rotatum, 

a Recent species described by Hedley from Funafuti, but 

that species is narrowly umbilicate, and on its base bears 

narrow radial bars of callus.

Occurrence: A single fossil, the holotype, from shallow drill hole, En-4, on Engebi Island, Eniwetok Atoll, 

at a depth of 1 foot; age, Recent. The species is living 

today in the Marshall Islands.

Teinostoma (Esmeralda) marshallense Ladd, n. sp. 

Plate 15, figures 18-20

Minute, lenticular; spire depressed, base flattened; 

imperforate; aperture broadly ovate, oblique, slightly 

contracted; peristome entire; umbilical area covered by 

moderately thick pad of callus. Sculpture consisting of 

exceedingly fine spiral lines and, on the base, traces of 

radial lines visible under magnification.

Measurements of the holotype, USNM 648438: height 

1.1 mm, diameter 2.2 mm.

T. marshallense is smaller and much less inflated than 

T. engebiense from Recent beds in the same area and has 

much finer spiral sculpture.

Occurrence: Holotype from drill hole K-1B, Eniwetok 

Atoll, at depth of 863-873 feet; five additional specimens 

from beds immediately below (873-884 ft) ; age, early 

Miocene (Tertiary /). A single specimen from drill hole 

2B on Bikini Atoll at depth of 2,175-2,185 feet is from 

beds still lower in the Miocene (Tertiary e).

Teinostoma (Esmeralda) sp. A 

Plate 15, figures 21-23

Minute, discoidal; spire depressed, thick; imperforate; 

aperture subcircular, slightly contracted; outer lip ex-
PALEONTOLOGY 79

tended forward. Sculpture consisting of closely spaced 

spiral lines.

Measurements of the figured specimen, USNM 648439: 

height 0.7 mm, diameter 1.5 mm.

Teinostoma sp. A resembles T. marshallense but is 

smaller, has coarser sculpture, and is less heavily callused 

in the umbilical region.

Occurrence: Represented by two somewhat worn specimens from the conglomerate at the base of the limestone 

in the Suva Formation on Walu Bay, Suva, Fiji (sta. 

160) ; age, early Miocene (Tertiary /).

Genus SOLARIORBIS Conrad

Conrad, 1865, Am. Jour. Conchology. v. 1, p. 30.

Type (by subsequent designation, Ball, 1892, Wagner 

Free Inst. Sci. Trans., v. 3, pt. 2, p. 414: Delphinula 

depressa Lea, Eocene (Claiborne Group) of Alabama.

Solariorbis tricarinata (Melvill and Standen) 

Plate 16, figures 1-3

Leucorhynchia tncaiinata Melvill and Standen, 1896, Jour. 

Conchology [Leeds], v. 8, p. 311, pi. 11, figs. 75a, b.

Shell discoidal, thick; spire low; periphery with three 

prominent keels separated by deep grooves, the middle 

keel larger than others and with a median depression 

close to the aperture; ends of keels truncated near aperture and covered by callus; whorls of protoconch smooth, 

subsequent whorls, including most of the body whorl, 

marked by low oblique radiating folds that extend less 

than half way across the otherwise smooth surface of the 

whorls. On the base, the exposed three-quarters of the 

body whorl bears 13 strong folds that radiate from the 

umbilicus; on the remainder of the .base, the folds are 

covered by callus which thickens into a projecting pad 

that shields the umbilicus when viewed from below; 

callus also covers the keels above the columella.

Measurements of the figured specimen (drill hole E-l, 

990-1,000 ft), USNM 648440: height 1.6 mm, diameter 

2.8 mm.

Occurrence: A rare shell from seven drill holes on 

Eniwetok and Bikini Atolls in the Marshall Islands. 

Total specimens, 13. The range is from Recent rocks 

close to the surface to Miocene (Tertiary e) at a depth 

of 1,471 feet. No Recent shells were found at Bikini and 

Eniwetok Atolls in spite of intensive collecting, but many 

examples were found in collections of drift shells from 

the nearby atolls of Rongerik and Rongelap. All the 

Recent shells are badly worn.

This distinctive species is one of the few mollusks that 

can be traced in the drill holes from Recent to lower 

Miocene beds without detectable changes. The Recent 

shell was first described from the Loyalty Islands and

was later reported by Hedley from the beach facing the 

Funafuti lagoon (Hedley 1899a, p. 406). Unusual features 

that distinguish it from other members of the genus are 

the strong peripheral ribs, the middle one being grooved 

near the aperture, and the thick pad of callus that shields 

the umbilicus.

Solariorbis? sp. 

Plate 16, figures 4, 5

Small, thick; spire low, consisting of 3^ rounded 

whorls, the last with a low keel at the periphery; aperture subcircular; inner lip callused and somewhat extended below by an obscure ridge that issues from a narrow umbilicus. Sculpture consisting of fine close-set 

spiral striae over the entire shell and regularly spaced 

axial wrinkles on the base.

Measurements of the figured specimen, B. P. Bishop 

Museum, geology No. 1236: height 1.3 mm, diameter 

1.9 mm.

The single fossil does not appear to be closely related 

to any described species, but the shell is worn and not 

suitable for a type. The reference to Solariorbis is questioned because the umbilicus is narrow, its ridge obscure, 

and there is no indication of a groove or channel at the 

junction of the upper edge of the outer lip with the 

parietal callus.

Occurrence: In the conglomerate at the base of the 

limestone in the Suva Formation exposed on Walu Bay, 

Suva, Fiji (sta. 160); age, early Miocene (Tertiary /).

Genus LYDIPHNIS Melvill

Melvill, 1906, Malacological Soc. London Proc., v. 7, p. 25.

Type (by monotypy): Cyclostrema euchilopteron 

Melvill and Standen. Recent, Gulf of Oman.

Lydiphnis eniwetokense Ladd, n. sp. 

Plate 16, figures 6-8

Small, wider than high, strongly turreted; apex flat; 

protoconch of 1% glossy convex whorls followed by 21/£ 

dull flattened sculptured whorls; body whorl with two 

strong spiral keels with scalloped margins; the margin of 

the higher keel turned upward. Aperture subquadrate, 

broadly extended below the columella; umbilicus wide. 

Secondary sculpture consisting of a .spiral rib between 

the two keels, a second spiral rib below the lower keel 

and a conspicuously beaded rib that spirals into the 

umbilicus; an obscure nodose rib developed on the body 

whorl immediately below the suture. Close-set tertiary 

spirals on the flattened upper surface of the body whorl. 

Axial growth lines are especially prominent in the area 

between the two keels. Both the holotype and paratype
80 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

retain traces of broad axial bands of brown on the upper 

part of the body whorl.

Measurements of the holotype (drill hole K-1B, 936- 

946 ft), USNM 648441: height 1.8 mm, diameter 2.1 mm. 

Paratype (E-l, 590-600 ft): height 1.1 mm, diameter 

1.6 mm. Two other specimens from hole E-l are smaller 

and appear to be immature.

The type species of Lydiphnis, L. euchilopteron (Melvill and Standen), is a larger Recent species in which the 

third or middle keel is much more prominent than on the 

Eniwetok fossils; the fossils likewise have a higher spire.

Occurrence: Four specimens from two drill holes on 

Eniwetok Atoll at depth of 590-946 feet; age, Pliocene 

to early Miocene (Tertiary h-f ).

Genus CYCLOSTREMISCUS Pilsbry and Olsson

Pilsbry and Olsson, 1945, Acad. Nat. Sci. Philadelphia Proc., v. 

97, p. 266.

Type (by original designation): Vitrinella panamensis 

C. B. Adams. Recent, Pacific coast of Panama.

Cyclostremiscus emeryi Ladd, n. sp. 

Plate 16, figures 9-11

Minute; spire flat, apex sunken, diameter approximately twice the height; protoconch of single smooth 

whorl followed by two sculptured whorls; umbilicus wide 

and deep; aperture subcircular, peristome continuous, 

outer lip thin, slightly angled by carinae. Sculpture consisting of about nine spiral carinae, two at the periphery 

being larger than .the others; all carinae except the 

peripheral pair are conspicuously beaded.

Measurements of the holotype (E-l, Eniwetok, 780- 

790 ft), USNM 648444: height 0.4 mm, diameter 0.9 mm. 

Paratype (E-l, Eniwetok, 990-1,000 ft) ; height 0.5 mm, 

diameter 1.0 mm.

The species is characterized particularly by its two 

strong almost smooth peripheral carinae with conspicuously beaded carinae above and below.

Occurrence: Eight specimens from drill hole E-l, Eniwetok Atoll, at depth of 630-1,589 feet; age, Miocene 

(Tertiary e-g). Two Recent specimens were recovered 

from beach drift on Rongerik Atoll and one was dredged 

from Bikini lagoon at a depth of 15 fathoms.

Subgenus PONOCYCLUS Pilsbry 

Pilsbry, 1953, Acad. Nat. Sci. Philadelphia Mon. 8, p. 426.

Type (by orginal designation): Adeorbis beaui Fischer. 

Recent, southeastern United States and West Indies.

Cyclostremiscus (Ponocyclus) novemcarinatus (Melvill) 

Plate 16, figures 12-14

Cycluxtrcma novcm-carinatum Melvill, 1907. Malacological Soc. 

London Proc., v. 7, p. 22, pi. 3, figs. 3, 3a.

Vitrinella (Lydiphnix) novcmcarinntum. Melvill. Berts, 1941, 

Geol.-mijnb. genootsch. Nederland en Kolonien Verh., 

Geol. ser., v. 13, pt. 1, p. 25, pi. 1, fig. 59, pi. 9, figs. 343-345.

Small; spire depressed; widely umbilicate, aperture 

oblique, subcircular. Sculpture consisting of strong 

spiral carinae, 8-10 on last whorl, the third and fourth 

from the top being larger than the others; radial striae 

visible under high power.

Measurements of the figured specimen (K-1B, 873-884 

ft), USNM 648442: height 1.0 mm, diameter 2.0 mm.

The Eniwetok fossils are identical with Recent shells 

from the Cook Islands. The radial striae of the fossils 

appear to be less conspicuous than those originally described by Melvill on Recent shells from the Gulf of 

Oman, but I have not seen specimens from the type 

locality.

Occurrence: Four fossils from two drill holes on Eniwetok Atoll at a depth of 873-970 feet; age, early Miocene 

(Tertiary /). A single large worn shell collected from 

beach drift on Rongerik Atoll. Described by Beets from 

the upper Miocene of East Borneo.

Cyclostremiscus (Ponocyclus) cingulifera (A. Adams) 

Plate 16, figures 15-17

Cyclostrema cingulifera A. Adams, 1850, Zool. Soc. London Proc.,

p. 43. 

Sowerby, 1863, Thesaurus Conchyliorum, pt. 23, p. 250, pi.

255, figs. 13-14. 

Tryon, 1888, Manual Conchology, v. 10, p. 93, pi. 32, figs.

72, 73.

Vitrinella cingulifera (A. Adams), Altena, 1938, Leidsche Geol. 

Mededel., v. 10, p. 298, fig. 17a-c. (See for additional 

citations.)

Medium size; spire low; widely umbilicate; aperture 

oblique, nearly circular with slight angle above; inner 

lip thinly callused. Sculpture consisting of strong uniformly spaced spiral carinae; 9-11 carinae of body whorl 

are subequal in size except for highest and lowest which 

are smaller; peristome thin, axial lines of growth appear 

on the early whorls and in the umbilicus but cannot be 

seen elsewhere except under high magnification.

Measurements of the figured specimen (Palau, USGS 

21304), USNM 648443: height 2.4 mm, diameter 4.0 mm.

Occurrence: Eight specimens from the marls at the 

base of the Palau Limestone in the Goikul area (USGS 

21301, 21304), Babelthuap, Palau; age, late Miocene 

(Tertiary g).
LOCALITIES 81

Recent shells have been reported from the Philippines, 

Japan, and other parts of the Indo-Pacific; fossil occurrence include the Pliocene and older beds of Java.

Genus COCHLIOLEPIS Stimpson

Stimpson, 1858, Boston Soc. Nat. History Proc., v. 6, p. 304.

Type (by monotypy): Cochliolepis parasitica Stimpson. Recent, South Carolina.

Cochliolepis diangalana Ladd, n. sp. 

Plate 16, figures 18-20

Small, discoidal; width more than twice the height; 

about three whorls, the last rapidly expanding, flattened 

near suture, partly embracing the preceding whorl; 

suture impressed; aperture oblique, subquadrate; umbilicus moderately wide, deep. Sculpture consisting of 

close-set spiral lines and coarser, more widely spaced 

wrinkles of growth.

Measurements of the holotype, USNM 648445: height 

0.8 mm, diameter 2.0 mm.

The Palauan fossil appears to be more strongly sculptured, both spirally and axially, than other fossil and 

Recent species.

Occurrence: Fifteen specimens from late Miocene 

(Tertiary g) marls at the base of the Palau Limestone in 

the Goikul area, Babelthuap Island, Palau (USGS 21301 

(holotype! and 21304).

Genus VITRINELLA C. B. Adams

Adams, C. B., 1850, Monograph Vitrinella, p. 3.

Type (by subsequent designation Bush, 1897, Connecticut Arts and Sci. Trans., v. 10, p. 105, 122): 

Vitrinella helicoidea C. B. Adams. Recent, Jamaica.

Vitrinella sp. A 

Plate 16, figures 21-23

Small, discoidal, depressed; aperture subcircular, 

oblique; inner lip thickened by slight expansions above 

and below; umbilicus narrow and deep, bordered by a 

beaded rib. Sculpture consisting of very fine spiral striae 

that are a little coarser near the umbilicus than elsewhere.

Measurements of the figured specimen, USNM 648446: 

diameter 1.5 mm, height 0.9 mm.

The small and possibly immature shells are tentatively 

assigned to Vitrinella because of the open umbilicus and 

spiral rib. They are, however, heavier and have stronger 

spiral sculpture than most Vitrinellas.

Occurrence: Single shell from drill hole 2B on Bikini 

Atoll at depth of 1,723-1,734 feet; age, early Miocene 

(Tertiary e) ; two Recent shells were collected from 

drift near Bikini Island.

LOCALITIES

Data on localities from which specimens studied were collected are given 

in the tables and illustrations that follow

Palau

[Balielthuap localities shown in fig. 2]

Island

Auluptagel

Do------

Babelthuap-__

Do___ _..

USGS 

Cenozoic

17715 

18322

21290

23642

21301 

21304

21308

21310

Locality and collector

Acropora zone at base of Palau Limestone at contact 

with underlying volcanic (Ngarsul Member of 

Aimeliik Formation) at southeast part of volcanic 

area, on west end of northern peninsula. P.E. Cloud 

and Arnold Mason, 1948. 

Road to lighthouse, altitude 350 ft. Arnold Mason

and P.E. Cloud, 1948. 

Acropora zone at base of Palau Limestone directly

above contact with underlying volcanic (Ngarsul 

Member of Aimeliik Formation) immediately southeast of causeway to Malakal; altitude 0-6 ft. H.S. 

Ladd, 1958. 

L'pper foot of breccia in quarry at south end of bridge

Malakal. G. Corwin and J.I. Tracey, Jr., 1964. 

Marl facies at base of Palau Limestone, Goikul peninsula (exact loc. on fig. 2), H.S. Ladd, 1958. 

Same as 21301 (fig. 2).

Do.

Do.

FIGURE 2. Sketch map of Goikul peninsula showing fossil 

localities and attitude of marl beds, southeastern Babelthuap, 

Palau.

Mariana Inlands 

[Guam fossil localities shown in fig. 3; Saipan and Tinian localities in fig. 4]

Island

Do _____

Do___.__

Do _____

Do_.--__

Do-_____

Do _ .

Do.__ _

Do-___-_

Do_-_.__

Do_____

Do..-.._

Do..... 

Do___-._

Do___-__

Do__-___

Do..-_.

Do.----_

Do------

USGS 

Cenozoic

17416

17446

17776

20489

20499

20511

20517

20526

20531

20533

20534

20536

20555 

20560

20574

20579

20585

20590

20600

Locality; collector, Pacific Island Engineers, 1946-50, 

unless otherwise indicated

Held. P.E. Cloud, Jr., 1948.

P.E. Cloud, Jr. and R.G. Schmidt, 1949.

from coast, close to high-tide level. P.E. Cloud, Jr. 

and R.G. Schmidt, 1948.

island.

3,050 ft south of Sinajana, waist of island.

About 3,000 ft southeast of Toto, waist of island.

4,600 ft east-northeast of Sinajana, waist of island.

About 3,000 ft east-northeast of Toto, waist of island.

About 4,700 ft southeast of Ordot, waist of island.
82 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

Ritidian Point

Orote Point

Tantapalo Point

Facpi Point

Catalina Point

012345 MILES 

1,1 I I I I

COCOS I

FIGURE 3. Sketch map of Guam, Mariana Islands, showing villages and physiographic features used in placing fossil localities.
LOCALITIES 83

Mariana Island* Continued

Island

Guam _. 

Do. 

Do. 

Do 

Do.

Do. 

Do. 

DoDoDo

DODODO

DoDo. 

Do_ 

DoDo.

Do_ 

DoDo_

Do. 

Do.

Do. 

Do. 

Do

Do

DoDo.

DoSaipan.

Do.

DoDo. 

Tinian- _ ..

USGS 

Cenozoic

Locality; collector, Pacific Island Engineers, 

1946 50, unless otherwise indicated

20602

20613

20614

20613

20616

20619

20634

20636

20639

20649

20650

206.53

20657

20678

20679

20687

20709

20711

20712

20720

20728

20732

20861

20869

20981

20994

21369

21373

21377

21382

21383

21591

21625

17387

17723

17891

17895

17904

18285

21407

21611

About 1,200 ft northeast of Barrigada Hill, waist of

island. 

About 1,700 ft northwest of lates Point, waist of

island. 

About 5,000 ft west of Taogam Point, about 1,000 ft

from shore, waist of island. 

About 2,500 ft northwest of Pago Point, waist of

island. 

About 4,500 ft west-northwest of Taogam Point, about

1,000 ft from shore, waist of island. 

West coast bluff, at Tamuning, 2,000 ft from shore. 

Abovit 1 mile south of Sinajana, waist of island. 

About 6,000 ft south of Sinajana, waist of island. 

About 3,400 ft northeast of Mount Lamlam, southern

part of island. 

About 1 mile northwest of Adjoulan Point, southeast

part of island. 

500 ft northweat of head of Talofofo Bay, southeast

coast. 

About 0.8 mile northwest of Talofofo, southern part

of island.

About 2,500 ft west of Fadian Point, waist of island. 

West side of Route 4, south of Inarajan, near southeast coast. 

Along road about 1 mile south of head of Talofofo

Bay. 

About 3,000 ft south-southeast of end of Asan Point,

west of Agana, west coast.

About 1^4 miles east of Agana, waist of island. 

About 0.4 mile east of Agana, waist of island. 

Eastern edge of Agana, on shore. 

About 3,000 ft inland from midpoint on west side

Inner Apra Harbor, west coast of island. 

About 0.9 mile south-southwest of end of Asan Point,

west of Agana.

1.3 miles south of Sinajana, waist of island. 

On coast near Taguan Point, waist of island. 

Right bank of Talofofo River about 3 miles northwest

of head Talofofo Bay, south lobe of island. 

Fafalog, northern end of island. D. Doan, 1952. 

Roadside ledge south of Mangilao at point 0.65 mile

southeast of junction with US 10. Fadian Point

area, waist of island. P.E. Cloud, 1953. 

Along secondary road about 0.85 mile southeast of

Ordot, waist of island. H.S. Ladd, 1958. 

Abandoned quarry near road, 1 mile south of Agfayan

Bay, southeast coast. H.S. Ladd, 1958. 

Abandoned quarry south side of road about 1 mile

east of fork in road lying about 1 mile southeast of

Chalan Pago; waist of island. H.S. Ladd, 1958. 

Roadcut on south side of point of land projecting into

southeast corner of Inner Apra Harbor, H.S. Ladd.

1958. 

First roadcut east of sta. 21382, southeast corner of

Inner Apra Harbor. H.S. Ladd, 1958. 

Cabras Island, northeast side Apra Harbor. P.E.

Cloud, 1954.

Large Fadian Point quarry. J.E. Tracey. 

About 0.4 mile east-southeast of Agingan Point.

R.G Schmidt and P.E. Cloud, 1948. 

About 1,000 ft N. 50° W. from Donni Springs.

R.G. Schmidt and P.E. Cloud, 1949. 

About 2,900 ft north-northwest of Naftan Point;

south end of island. P.E. Cloud, 1948. 

About 2,300 ft west of Hasngot Beach on east coast.

R.G. Schmidt, 1949. 

About 1,500 ft east of Magpi Point, northern

end of island. H.W. Burke, 1949. 

About 3,600 ft north-northeast of Naftan Point (soxith

tip of island) at a point 500 ft inshore from edge of

sea cliff. P.E. Cloud, 1948. 

Same as 17387, H.S. Ladd, 1958. 

Surface of terrace at Marpo Point, altitude. 120 ft.

J. Bridge, 1945.

Sabaneta Point,

0123 MILES 

L

Naftan Point

FIGURE 4. Sketch map of Saipan, Mariana Islands, showing 

fossil localities.

Marshall Islands

[Eniwetok drill holes (except P- -A and P- -C) shown in figs. 5 and 6, 

Bikini drill holes in fig. 7. ONR, Office of Naval Research; USGS, U.S. 

Geological Survey; AEC, Atomic Energy Commission; JTF, Operation 

Crossroads, Joint Task Force One]

Atoll

Do_-___ _

Do-_ --_.

Do____ _

Do_ --_-_.

Do-.- _--

Do_-._---

Do__..-__

Do_-_-.-_

Do__--_-_

Do__ __-_

Do_ _--.__

Do. ------

Do- _--_--

Bikini. _-- -.

Do..-- _--

Do__--___

Do-. -__

Island

-..--..do _._---

_---.-_do_-.--_-

-._-.-_do__-_._-

_..--.-dO--__-__

_._---. do.___-_.

------ _do.-__-._

Bikini-.-.- ___-

------_do-._---_

___..-_dO-----_-

_-_- .do _

Drill 

hole

F-l

F- A

F--C

E-1

K-l

K-1B

En-4

En-9

Mu-4

Mu-5

Mu-6

EB-2

A-l

RU-2

1

2

2A

2B

Total 

depth

(feet)

4,630

100

102.5

4,222

443.5

1,280

48

110

48

80

100

53.5

200

135

300

190

1,346

2,556

Driller and date 

ONR and USGS, 1952.

AEC, 1952.

AEC, 1952.

ONR and USGS, 1952.

ONR and USGS, 1951.

ONR and USGS, 1951.

AEC, 1950.

AEC, 1950.

AEC, 1950.

AEC, 1950.

AEC, 1950.

AEC, 1950.

AEC, 1950.

AEC, 1950.

JTF, 1947.

JTF, 1947.

JTF, 1947.

JTF, 1947.
84 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

162°00' 162° 10' 162°20' 162°30'

11°20'

PARRY ISLAND

10 

I

15 MILES 

_J

 HAWAIIAN IS

.ENIWETOK

140° 140°

l/2 1 MILE

J_____________I

FIGURE 5. Location of deep holes drilled on Eniwetok Atoll, Marshall Islands.
LOCALITIES 85

162°10' 162°20' 162°30'

11 MO'

140° ISO- 140 0 RUNIT

FIGURE 6. Location of numbered shallow holes drilled on islands of Eniwetok Atoll, Marshall Islands.
86 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

FIGURE 7. Location of holes drilled on Bikini Atoll, Marshall

Islands.

Ellice Islands Funafuti Atoll

Island

Funaf utL _ _ _ _ 

Do 

Drill hole

(fig. 8)

Main 

boring

---_do--.--

Depth 

(feet)

0-698 

698-1114^

Driller and date

Royal Society, T.W. Edgeworth 

David, 1897. 

Royal Society, A.E. Finckh, 1898.

FIGURE 8. Location of deep hole drilled on Funafuti Island, 

Ellice Islands.

JMew tleonaes 

[Fossil localities shown in fig. 9]

Island

Espiritu 

Santo

Do 

Do .-- 

Do- -

Do --

USGS 

Cenozoic

21026

21027 

21028

21029 

21031

Station

ES-4

ES-5 

ES-14

ES-2

Locality and collector

Along road: altitude 150-250 ft. 

H.T. Stearns. 

Altitude 150 ft. H.T. Stearns. 

From engineers pit, altitude 240 ft. 

H.T. Stearns. 

From coral pit at altitude 215 ft. 

H.T. Stearns. 

Gravel bar in Sarakata River near 

coast; north of Segond Channel. 

H.T. Stearns. 

Nua River; waist of island. Collected 

by E.A. de La Rue; described by 

R. Abrard. 

Bay of Foreland, about 3,200 ft northnortheast of Foreland Head. Collected by E.A. de La Rile: described by R. Abrard.

Fiji

Island

Viti Levu_ _ - _ 

Do .-

Do -

Do - 

Do -.-

Do 

DoDo -

Do 

Do __-

Do _.-

Fulanga-_-_- 

Do - 

Do ---

Do .--

Do .-

Do .-

Vanuia, 

Ongea

Do --- 

Lakemba.

Do -

Do __-

Station

59 

160 

160 A

295

297 

305

320 

MR-20

FB-20 

FB-22

L-24 

L-32 

L-35

L-45 

L-46 

L-78

L-120 

L-148 

I --30 1

L-403

Locality 

shown in 

fig 

10 

10 

10

10 

10

10 

10

10 

10

10 

10

11 

11 

11

11 

11 

11

12 

12 

13

13 

13

Locality and collector

Right bank of Wailoa River about 1 

mile west of Nasongo; altitude 995 

ft. H.S. Ladd. 

Conglomerate, quarry on south side 

of Walu Bay, near entrance; few 

feet above sea level. H.S. Ladd. 

South side of Walu Bay about 200 

yards east of bridge (close to sta. 

160). R.E. Houtz. 

Right bank of Wailoa River a few 

yards above sta. 59. H.S. Ladd. 

Tamavua Quarry at head of Walu 

Bay; 41 ft exposed; base 144 ft 

above sea level. H.S. Ladd and 

others. 

Quarry on south side of Walu Bay, 

near entrance; directly overlies 

rock of sta. 160. H.S. Ladd. 

About 1M miles SSE. of Suva Post 

Office; old quarry face on left bank 

of creek which enters sea near tip 

of Suva Point, 12 ft exposed; base 

lying 3 ft above high tide level. 

P. Turner. 

Along trail between Naivotho and 

Matainanu; 15 ft exposed; altitude 

245 ft. H.S. Ladd 

Korotambua Creek. 1,350 ft southwest of end of railroad spur. M.J. 

Rickard. 

Same as Ladd's sta. 160. W.M. 

Briggs, Jr. 

Limestone about 28 ft above conglomerate, south side of Walu Bay 

near entrance. W.M. Briggs, Jr. 

Elevated reef at end of northwest 

horn; altitude 0-10 ft. H.S. Ladd 

Summit of Nawiriwiri (Quoin Hill); 

altitude 260 ft. H.S. Ladd. 

Elevated reef on seaward side of 

Nasuthu; altitude 0-25 ft. H.S. 

Ladd. 

Elevated reef on inner side of northwest 'horn; altitude 5-15 ft. H.S. 

Ladd. 

Elevated reef on small island northwest of Nasuthu; altitude 0-10 ft. 

H.S. Ladd. 

Southeast slope of Ndelai Korolevu; 

altitude 10 ft. H.S. Ladd.

Elevated reef, southwest coast; alti 

tude 0-8 ft. H.S. Ladd. 

Summit of highest hill on northwest 

coast; altitude 200 ft. H.S. Ladd. 

Top of hill at Vatiiloa on southwest 

coast; altitude 84-99 ft. H.S. 

Ladd. 

Outcrop on first point southeast of 

Tumbou; altitude 0-5 ft. H.S. 

Ladd. 1 On west coast about 3 miles northwest of Tumbou; altitude 0-30 ft. 

H.S. Ladd1
LOCALITIES

167°

87

167' 16'

ESPIRITU SANTO

Sarakata

21031 

21026-29. 

(approx) fj&

R/Norsup Bay

168 c

10 15 20 

I

25 MILES

Bay of 

Foreland

Foreland 

Head

FIGURE 9. Fossil localities in the New Hebrides.

Fiji Continued

Island

Yanua

Do------

Station

110H

HOC

M2

Locality 

shown on 

fig.-

Locality and collector

village: altitude 15 ft. H.S. Ladd 

and J.E. Hoffmeister. 

Tip of Ndukelulu Point, north of

Ndalithoni village; altitude 12 ft. 

H.S. Ladd and J.E. Hoffmeister. 

Ngillangilla, northwest extremity of

island; altitude 10 ft. E.C. Andrews.

tude 400 ft. J.E. Hoffmeister. 

Altitude 650 ft. E.C. Andrews.

FIGURE 10. Fossil localities on Viti Levu, Fiji.
88 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

FIGURE 11. Fossil localities on Fulanga, Lau, Fiji.

Tonga

Island

Tongatabu___ 

Do.- .--

Do ____

Do______ 

Do ___..

Do_____

Do _____

Do--__- 

Do-____

Do_ _.-._

B.P. Bishop 

Mus. Cat.

202497 

202720

202879

202950 

202967

202976

202980

204926 

204927

204928

Station 

(fig. 14)

7 

7

2

4

3

3

7 

3

3

Locality and collector

Quarry at Nukualofa % mile from sea, 

alttiude 10 ft. J.E. Hoffmeister 

and J.M. Ostergaard.

altitude 0-40 ft. J.M. Ostergaard, 

W.A. Setchell and J.E. Hoftmeister. 

Holoipepe Quarry about 6 miles west 

of Nukualofa. J.M. Ostergaard 

and J.E. Hoffmeister. 

Shore rocks near Houma. J.M. Ostergaard.

altitude 35 ft. J.M. Ostergaard. 

Do.

See 202497. 

See 202976.

Do.

of island; U.S.F.C. steamer Albatross, 1898.

ONGEA ISLANDS

2 MILES

FIGURE 12. Fossil localities on Ongea, Lau, Fiji.
REFERENCES 89

FIGUKK 13. Fossil localities on Lakemba. Lau, Fiji.

FIGURE 14. Fossil localities on Tongatabu, Tonga.

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INDEX

A Page

abbotti, Rissoina (Rissoina) ____ 14, 18, 70; pl. 13 

abrardi, Zebina ________________________ 21

Zebina (Ailinzebina) __ 14, 18, 20, 65; pi. 12 

Abyssothyris __________________ 15 

Acanthochitona _________________ 21, 24

sp _ 12,16,24; pl. 1 

Acanthochitonidae ___ __ 12, 16, 24 

acutanyulus, Trochus ____________________ 39

adamsiana, Pisulina __________________ 59

Adeorbidae _________________ 14, 18, 75 

Adeorbis beaui ___________________ 80 

aedonia, Scissurella _______________ 27

africana, Cynisca _________________ 50

ayapeta, Mmeola _______________________ 39

Monilea _____________________ 39 

ailinana, Rissoina ______________________ 8, 71

Rissoina (Rissoina) ________ 14, 18, 70; pl. 13

Ailinzebina ____________________________ 21, 65

olbicilla, Nerita ________________________ 56

alexsi, Rissoina (Phosinella) ___ 14, 18, 70; pl. 13 

alfredensis, Cynisca _____________________ 50

Alvania ______________________ f>2, 63

corayi _________ _____________ 63

pisinna _____________________ 63

(Taramellia) corayi ________ 13,18,63; pl. 12

kenneyi _______________ 13, 18, 63; pl. 12

anibiyua parryensis, Rissoina (Rissoina) _ 14,

18,72; pl. 14

Pyramidella ___________________ 71

Rissoa ___________________ 71

Rissoina ____________________ 71

(Rissoina) __________ 14, 18, 71; pl. 14 

ambulata, Parashiela ____________________ 64

ammonoceras, Cyclostrema _________ 77

Munditiella _______________ 78

Amphinerita ______________________ 55

Amphithalmus ___________________ 61

inclusus ______________________ 61

jeffcoati _____ ______________ 62

(Cerostraca) jeffcoati _____ 13, 18, 62; pl. 11 

myersi ____________ 13, 18, 62; pl. 11

(Pisinna) bikiniensis ___ 13, 18, 62; pl. 12 

Ampullina ____________________ 8

Anatoma __________________________ 27

Angaria _____________ __ _____ 42

delphinus ____________ 12, 17, 20, 42; pl. 5

Angariidae ________________ 12, 17, 42 

angasi, Lorica ____________________ 22

angulatus, Euchelus _______________ 34

Euchelus foveolatus _________________ 34

(Vaceuchelus) _______ 12, 16, 20, 34; pl. 3

anyulifera, Monodonta _____________ 36

annulata, Iravadia ________________ 60

Antillachelus -_____________________ 34

antipodes, Scutus _______________ 30

apertura, Patella _________________ 31

apicina, Isanda (Parminolia) _ 12, 16, 20, 39; pl. 5

Monilea _________________ 39

Area _______ ________________ 8

archeri, Cyclostrema _________________ 78

Munditiella _________________________ 78

.Irene _____________________ 19, 45

mineata ________________________ 46

(Arene) metaltilana _________ 13, 17,45; pl. 7

sp. A _____________ 13,17,45; pl. 7

[Italic page numbers indicate descriptions]

Page

aryyrostoma, Marmarostoma _ _ 48 

aryyrostomus, Turbo ________ 27, 48, 49

Turbo (Marmarostoma) __ 13,17,20,48; pl. 7 

asinina, Haliotis ___________________ 25

Assinunea ___________________ 75

yrayana ____________________________ 75

nitida eniwetokensis ________ 14, 18, 75; pl. 10

marshallensis _________ _ 75

nitida _____________________ 75

Assimineidae ________________ 14, 18, 75 

Astele _________________________________ 37

calliston ___________________________ 37

(Callistele) engebiensis ______ 12,16,37; pl. 4

Antraea ______________________ 21, 43, 45 

calcar ____________________ 43

eniwetokensis _________________ 44

fimbriata ___________________________ 44

holmesi ______________________ 45

rhodostoma __________________ 43

(Astralium) eniwetokensis __- 13, 17,43; pl. 6

rliodostoma _________ 13,17,43; pl. 6

waluensis _________ *13, 17, 43; pl. 6

sp. A ____________ 13, 17, 44; pl. 6

sp. B ____________ 13, 17, 44; pl-6

sp. C ___________13,17, 44; pl-6

(Bellastraea) sp. D ______ 13,17,44; pl. 6

sp. E ____________ 13, 17, 44; pl. 6

(Calcar) confrayosum _ 43

sp. A ____________________ 43

(Vitiastraea) holmesi _______ 13,17,45; pl. 6

Astralium ___ ____________ _ 43, 44 

petrusum virescens _______ ___ 43

(Cyclocantha) petrosum _ 43

Aatrea sp. A _ ___ 44

sp. D ______________________ 45

aturi, Aturia _______ 5

Aturia _________________________________ 5

aturi _______________________ 5

audax, Eliyidon ________________ 31

austrae, Buccinum _________ _ 53

australis, Emarginula ______ 29

Hemitoma ___________________ 29

Austroliotia _____________________ 46

B

bainearti, Leptothyra ___ 13, 17, 20, 51, 52; pl. 9

balteata, Rissoina ______ 69

Rissoina (Phosinella) __ 14, 18, 20, 69; pl. 13

barbara, Patella _________ ______ 32

Barleeia 75

carpenteri ___________________ 75

meiauhana __________________ 75

rubra ____________________ 75

(Barleeia) meiauhana ___ 14, 18, 75; pl. 14 

beaui, Adeorbis ______ _ 80

beetsi, Parashiela ___________ 13, 18, 64; pl. 12

belcheri, Monilea (Monilea) __ 12, 16, 41', pl- 5

Trochus __________ _ 41

Bellastraea _________ 44 

kesteveni ___________________ 44

Beraua ________________________ 20, 35

berauensis, Cantharidus (Cantharidus) ___ 35

Globularia __________ 8

Thalotia _____________________ 19

(Thalotia) __________ 12, 16, 35; pl. 3

Page

bicancellata, Emaryinula 27

Emaryinula (Emarginula) 12, 16, 27; pl. 2

bikiniensis, Amphithalmus (Pisinna) 13,

18,62; pl. 12

Hemitoma (Montfortia) __ 12,16,29; pl. 2

Rissoina (Phosinella) __ 14, 18, 69; pl. 13

blainvilli, Rimula 30

bomasensis, Tectus 20, 39

Tcctus (Tectus) 12, 16, 39; pl. 4

botanica, Liotia ___ 46

Liotina __________ 46

(Austroliotia) 13, 17, 46; pl. 7

bourneae, Rissoina (Rissolina) 14, 18, 74', pl- 17

brevispina, Neritina _ 57

briygsi, Rissoina (Phosinella) 14, 18, 68; pl. 13

browniana, Rissoina 64

bryerea, Rissoina 66

Buccinum austrae _ _ - 53

C

calcar, Astraca __ 43

Turbo ____________ 43

calcaratus, Trochus 37

Trochus (Infundibulum) 43

caledonica, Leucorhynchia 14, 18, 76; pl. 14

caledonicum, Tienostoma (Leucorhynchia) _ 76

calliferus, Trochus 40

Callistele - S7

calliston, Astele _ _ 37

canaliculatus, Turbo 49

cancellata, Stomatella 34

cancellatus orientalis, Euchelus (Hybochelus) 34

orientalis, Hybochelus __ 12, 16,34, 35; pl. 3

Candida, Collonia _____ 51

Leptothyra ________ 13,17, 51; pl. 9

Cantharidus erinaceus __ - 35

(Cantharidus) berauensis 35

carpenteri, Barleeia _ _ 75

Cellana _ 32

sayittata __________ 12, 16, 32

sp. A ________________ 12,16,32; pl. 3

sp. ____________________ 12, 16, 33

cerithiformis, Rissoina __ _ 69

cernica, Nacella _ _ 32

Cerostraca _ _ 62

iredalei 62

cheilostoma, Merelina ___ _ 63

Rissoa 63

chinenensis, Liotina _ _ 46

Chiton con/ossus _____ 23

fascicularis _ 24

incisus _ 21

larvae-formis 24

Chitonidae _____ 12, 16, 23

chitons 21

chrysostomus, Marmarostoma 48

Turbo ____________ 48, 49

(Marmarostoma) ___ 13, 17, 20, 48; pl. 7

(Turbo) _________ 48

Cibdezebina - - 64

cinyttlus, Turbo - 61

Cinyula 61

lampra 61

roseocincta _ 61

(Peringiella) parryensis 13, 18, 61; pl. 11

roseocincta 13, 18, 61; pl. 11

93
94

Page 

cingulijera, Cyclostrema ______ 80

Cyclostrerniscus (Ponocychis) ________ 14,

19, 20, SO; pi. 16

Vitrinella __________________ 80

Clanculus _____________________ 38

(Clanculus) clanguloides fijiensis ______ 12,

16, 38 ; pi. 4

clangidoides fijiensis, Clanculus (Clanculus) 12,

16,38; pi. 4

dathrata, Haliotis (Padollus) 12, 16, 26; pi. 2 

Rissoina ___________________________ 68, 69

(Phosinella) _____ 14, 18, 20, 68; pis. 12, 13

Clithon _______________________ 57

corona _ ________________ 15

(Clithon) corona __________ 13, 17, 20, 57

clypeus, Emarginula _________________ 28

Emarginula (Emarginula) __ 12, 16, 28; pi. 2 

Cochliolepis ____________________ 81

diangalana ________________ 14, 19, 81; pi. 16

parasitica ______________ _ 81 

colei, Smaragdia (Smaragdia) __ 13, 17, 58; pi. 11 

Collonia Candida ______________ 51

granulosa ___________________ 52

maculosa __________ _ 50

picta _________ 53

variabilis _______ 54

concinna, Rissoina _ _ 72

Rissoina (Rissoina) ________ 14, 18, 7B; pi. 13

Stomatella _________ 41 

(Synaptocochlea) ________________ 42

Synaptocochlea _____________ 12, 17, 41; pi. 5

confossus, Chiton ___________ 23

Lucilina 23, 24

cunfrago&um, Astraea (Calcar) 43

ronica, Emarginula ____________________ 27

Monodonta _______________________ 35

connectens, Emarginula _______ _ 28

Conus _ __________ 4

Trochus 39

coo-peri, Zebina (Morchiella) ____ 14, 18, 65; pi. 12

corayi, Alvania ______________ _ __ 63

Alvania (Taramellia) _______ 13, 18, 63; pi. 12

corona, Clithon ______ 15 

Clithon (Clithon) _____________ 13, 17, 20, 57

Nerita _____________________________ 57

Theodoxus ___ _ 57 

(Clithon) ___________ _______ 57

coronata, Isanda ________________________ 39

Rissoina ___________ 64

Scissurella _ _ 27

(Scissurella) __ __ 12, 16, 27; pi. 2

coronatus, Tectarius _ 59

costata, Leptothyra _ 50, 52

costulata, Rissoina _______ 69

crassus, Turbo ______ _ _ 49

Turbo (Mannarostoma) _____ 13,17,49; pi. 8

crenata, Delphinula _____________________ 46

Liotina ______________________ 46

creniferus, Trochus incrassatus _______ , 38

crispata, Scissurella _ 27 

crossei, Leucorhynchia _________ 14, 18, 76; pi. 14

Tienostoma (Leucorhynchia) _ _ 76 

Cryptoplax ______________ 21, %

menkrawitensis _______ 12, 16, 20, 24, 25; pi. 1

striatus _____________________ 25

sp. A _______________ 12, 16, 24; pi. 1

sp. B _______________ 12, 16, 25; pi. 1

sp. ______________________ 12, 16, 25

Cycloclypeus _______ 4, 15

cycloma, Liotina ________________ 46

Liotina (Dentarene) _______________ 20

r yclophoreus, Haplocochlias ________ 76

Cyclostrema ammonoceras ______________ 77

archeri _________________ _ 78

cingulijera _ _ 80 

euchilopteron ______________ 79

Page 

novem-carinatum 80

Cyclostremiscus __ 80

emeryi 14, 19, 80; pi. 16

novemcarinatus __ _ 20

(Ponocyclus) cingulifera 14, 19, 20, 80; pi. 16

novemcarinatus _ 14, 19, 20, 80; pi. 16

Cynisca 19, 49, 50

africana ________ _ 50

alfredensis ______ 50

forticostata ____ 50

gloriosa 50 

granulata 49

granulosa _________ 50

pacifica _________________ _ 13, 17, 49; pi. 8

D

declinans, Scissurella __ _ __ 26

Scissurella (Scissurella) __ 12, 16, 20, 26; pi. 2

decussata, Rissoina _ _ - 67

Delphinula crenata 46

depressa __________________ 79

distorta ______ 42

gervillei ______________________ 46

granulosa _________________ 49

Delphinulidae _________ _ -__ 42

delphinus, Angaria ____ 12, 17, 20, 1$; pi. 5

Turbo _____________________________ 42

Dentarene _____________________ 46

sarcina ______________ __ __ 46

depressa, Delphinula _ 79 

diangalana, Cochliolepis _______ 14, 19, 81; pi. 16

Diodora __________________ __ 31 

granifera _________-__ __ -_ 31

marshallensis ____ _ _ __ 32

(Elegidion) granifera _______ 12, 16, 31; pi. 3

marshallensis ________ 12, 16, 31; pi. 3

sp. A ____________ 12, 16, 32; pi. 3

distorta, Delphinula _________________ 42

E

ekkanana, Rissoina (Rissoina) 14, 18, 71; pi. 13

Elegidion _________________,_________ 31

audax _____ ____________ 31

elongatus, Thalotia _____________________ 35

Thalotia (Thalotia) _______ 12, 16, 35; pi. 3

Emarginula _____ __ __ __ 27, 30 

australis _ 29 

bicancellata ________________________ 27

clypeus - _______________ 28

conica _______ __ _ __ 27

connectens __ 28 

maculata ___________________________ 28

peasei _______________________ 28

souberbiana _ 28 

souverbiana ____________ __ __ 28

sublathrata _______ ____ __ 29

(Emarginula) bicancellata __ 12, 16, 27 pi. 2 

clypeus _______________ 12, 16, 28 pi. 2

peasei _________________ 12, 16, 28 pi. 2

(Subzeidora) souverbiana _ 12, 16, 28 pi. 2 

sp. A _____________ 12, 16, 28 pi. 2 

sp. B _____________ 12, 16, 29 pi. 2

emenana, Leptothyra ____ __ 13, 17, 53 pi. 9 

Rissoina (Zebinella) ______ 14, 18, 67; pi. 12

emeryi, Cyclostremiscus _______ 14, 19, 80; pi. 16

engebiense, Teinostoma __ _ _ 78 

Teinostoma (Esmeralda) _ 14, 18, 78; pi. 15

engebiensis, Astele (Callistele) __ 12, 16, 37; pi. 4 

Gibbula (Gibbula) 12, 16, 36; pi. 4

aiiwetokense, Lydiphnis _____ 14,18,79; pi. 16

eniteetokensis, Assiminea nitida __ 14, 18, 75; pi. 10

Astraea _____ _ 44

(Astralium) 13, 17, 43; pi. 6

ephamilla, Rissoina ________-__ 73

Rissoina (Rissolina) ____ 14, 18, 20, 73; pi. 14

Page

cquatoria, Scissurella _ _ 27 

Scissurella (Anatoma) ______ 12,16,27; pi. 2

erinaceus, Cantharidus __________________ 35

Thalotia ____________ __ 20, 35

Esmeralda __ __ __ _ _ 78

esmeralda, Teinostoma 78

Euchelus ___________________ S3

angulatus _________-_ ____ 34

joveolatus angulatus - _ _ 34

instrictus ___________________ 33, 34

morrisoni . 36

quadricarinatus 34

scabriusculus _________________ 33

stellata _ 36

(Euchelus) quadricarinatus _ 12,16,33; pi. 3

(Herpetopoma) instrictus - 12, 16, 20, 33; pi. 3

instrictus suvaensis 12, 16, 33; pi. 3

(Hybochelus) cancellatus orie.nta.lis 34

kavoricus 35

(Vaceuchelus) angulatus 12, 16, 20, 34; pi. 3

sp. A ____________ 12,16,34; pi-3

euchilopteron, Cyclostrema 79

Lydiphnis 80

excentrica, Hemitoma (Montfortista) 12,

16, 30; pi. 2

Montfortia (Montfortista) - - - 30 

exquisita, Rimula ________ 12, 16, 20, 30; pi. 2 

exuvia, N-erita __ _ _ 57

F

fascicularis, Chiton __ _ _ _ _ 24 

jenestratus, Tectus _ 39 

fijiensis, Clanculus (Clanculus) clanguloides 12,

16,38; pi. 4

fimbriata, Astraea 44

fissura. Patella _________ _ ____ 27

Fissurellidae ___________-__ __ 12, 16, 27

flexuosa, Rissoina (Schwartziella) 14, 18, 66; pi. 12

forsythi', Nannoscutum 30, 31

forticostata, Cynisca _ _ _ 50

Fossarina ___ _ _ 36

legrandi 37

patula 36

(Minopa) hoffmeisteri __ 12, 16, 20, 37; pi. 4

foveolatus, angulatus, Euchelus 34

G

Gabrielona 64

nepeanensis ____ _ _ 54

raunana ______ _ 13, 17, 54; pi. 10

gardnerae, Iravadia 13, 17, 60; pi. 11

Gastropods 25

Gena rosacea ___-_ _ _ _ _ 42

gervillei, Delphinula _ _ _ 46

Gibbula _____________________ 36

gradata __ 36

magus 36

pisum 36

(Gibbula) engebiensis _____ 12, 16, 36; pi. 4 

gigantea, Rissoina _ _ _ _ _ 65 

glabrata, Rissoa 62 

glareosa marshallensis, Leptothyra - ____ 13,

17,20,52; pi. 9

Monilea ______ __ __ __-_ 52 

Globularia berauensis _ _____ _ _ 8 

gloriosa, Cynisca _ 50 

goikulensis, Putilla (Parvisetia) ______ 13,

18, 60, 61; pi. 11

Rissoina (Rissoina) 14, 18, 71; pi. 13

Schizochiton incisus ____ 12, 16, 2/, 22; pi. 1

gracilis, Rissoa _____ _____ _ 66

Rissoina _ _ _ _ 66 

(Schwartziella) ______ 14, 18, 66; pi. 12

gradata, Gibbula 36 

Rissoa _ ______ __ _______ 63, 64

graeca, Patella _ _ _ __ ____ 31 

granifera, Diodora _ _ _ _ 32
INDEX 95

J)iodora (Elegidion) ___

qranulata, Cynisca ___.

f/ranulosa, Collonia ___.

Cynisca ___________

Delphinula ________

Merelina ________.

grayana, Assiminea ____.

qruneri, Turbo (Ocana) 

(iyraulus __ _______

12, 16, 3

Page

I Pi-3 

49 

52 

50 

49 

63 

75

H

Haliotidae ___________________ 12, 16, 25 

Haliotis ____________________________ 25, 26, 41

asinina _____________________ 25

ovina ________________________ 25, 26

tuvuthaensis _____________________ 12, 16, 26

(Padollus) dathrata _____ 12, 16, .6; pi. 2

ovtna ______________ 12, 16, _5; pi. 2

sp. ______________________ 12, 16, 26

Haplocorhlias ____________________ 19

cyclophoreus __________________ 76

minutissimus ___________________ 77

(Lophocochhas) minutissimus ________ 77

sp. A _______________ 14, 18, 76; pi. 14 

harlani, Leptothyra ________13, 17, 51; pi. 9

harti, Rissoina (Rissolina) _ 14, 18, 74; pi. 14 

Helcioniscus sagittata ________________ 32

sp. _________ 33 

helicoidea, Vitrinella ________________ 81

heliotropium, Trochus ___________________ 43

Hemitoma ______________________ 29 

austmlis _____________________ 29

ossea _ ______________ 29, 30 

(Hemitoma) sp. _________ 12,16,29; pi. 2 

(Montfortia) bikiniensis __ 12, 16, 29; pi. 2 

sp. A ________ 12, 16, SO; pi. 2 

(Montfortista) excentrica ____ 12,16,30; pi. 2

Herpetopoma _____ 33

herringi, Rissoina (Rissolina) ___ 14, 18, 74; pi. 14 

JTOoa _______________________ 54 

histrio histrio, Trochus ______________ 37

Trochus ____________________________ 37

histrio ____________________ 37

(Trochus) ___________ 12, 16, 20, 37; pi. 4

Turbo _____________________________ 37

hoffmeisteri, Fossarina (Minopa) ________ 12,

16, 20, 37; pi. 4

holmesi, Astraea _________________ 45 

Astraea (Vitiastraea) ______13, 17, 45; pi. 6

Hybochelus _________________ 34 

cancellatus orientalis _____ 12,16,34,35; pi. 3

kavoricus _______________ 12,16,35; pi. 3

Hydrocena nitida __________________ 75

I

iinperialis, Trochus ________________ 43

inca, Rissoina _____________________ 70

incisus, Chiton _________________ 21

goikulensis, Schizochitori _ 12, 16, 21, 22; pi. 1

Schizochiton __________________ 21, 22 

inclusus, Amphithalmus __________ 61 

incrassatus creniferus, Trochus _______ 38

Trochus -___________________ 38 

(Trochus) ____________________ 12,16,38

indrai, Rissoina _______________ 20, 67

(Schwartziella) _________ 14, 18, 66; pi. 12

inepta. Leptothyra _______ 13, 17, 50, 51; pi. 8

Monilea ____________________ 50

mfensa, Liotina __________________ 46

insculpta, Nerita _______________ 55

Nerita (Amphinerita) __ 13, 17, 20, 55; pi. 10 

instrictus, Euchelus ____________________ 33, 34

Euchelus (Herpetopoma) _ 12, 16, 20, 33; pi. 3

suvaensis, Euchelus (Herpetopoma) __ 12,

16, 33; pi. 3

Troctnis (Moiwdonta) _______________ 33

Page

Iravadia -------- 59

annulata ____ _ 60

gardnerae 13, 17, 60; pi. 11

ornata _________ __ 60

trochlearis _ _ 60 

Iravadiidae __________________- 13, 17, 59 

iredalei, Cerostraca __ 62 

Isanda _______ 39

coronata __________ 39

(Parminolia) apicina 12,16,20,39; pi. 5 

invisibilis, Rissoa ______ 64

J

jeficoati, Amphithalmus _ _ 62

Amphithalmus (Cerostraca) _ 13, 18, 62; pi. 11

jirikana, Rissoina (Schwartziella) 14,18,67; pi. 12

joffjacartensis, Neritina __ _ 20, 58

Smaragdia (Smaragdia) 13, 17, 58; pis. 10, 11

K

kavoricus, Euchelus (Hybochelus) 35

Hybochelus ____________ 12, 16,35; pi. 3

kenneyi, Alvania (Taramellia) __ 13, 18, 63; pi. 12

kesteveni, Bellastraea _________________ 44

kickarayana, Rissoina 74

Rissoina (Rissolina) _ _ 14, 18, 74; pi. 14 

killeblebana, Zebina (Morchiella) 14,18,65; pi. 12

L 

laeta, Leptothyra _______ 13, 17, 51; pi. 9

laevigata, Scissurella 26

laevis, Rissoa __________________ 61 

lampra, Cingula _______ ____ 61 

larvae-formis, Chiton __ _ 24 

legrandi, Fossarina _ _ 37 

lekalekana, Synaptocochlea ______12, 17, 4%\ pi. 5

lekalekanum, Sinum ___________________ 42

Leptothyra ____________________________ 50, 52

balnearii ______._ 13, 17, 20, 51, 52; pi. 9

Candida 13, 17, 51; pi. 9

costata 50, 52

emenana ____________ 13, 17, 53; pi. 9

glareosa marsh aliens in 13, 17, 20, 52; pi. 9 

harlani 13, 17, 51; pi. 9

inepta 13, 17, 50, 51; pi. 8

laeta ______ 13, 17, 51; pi. 9

maculosa 13, 17, 20, 50; pi. 8 

picta 13, 17, 53; pi. 9

wellsi ________________ 13, 17, 52; pi. 9

sp. A _______________ 13, 17, 53; pi. 9

Leucorhynchia ________________ 76, 77

caledonica 14, 18, 76; pi. 14

crossei 14, 18, 76; pi. 14 

lilli 14, 18, 77; pi. 15

stephensoni _________ 14, 18, 76, 77; pi. 14 

tricarinata _________ _________ 79

/ifuana, Monilea ________ _____ 40 

Monilea (Monilea) ________ 12,16,40; pi. 5

lifuanus, Trochus (Monilea) 40

lilli, Leucorhynchia 14, 18, 77; pi. 15 

lineata, Nerita ___________________ 56

Linernera __________________________ 63

Liotia botanica ____ _______ 46

loculosa --______________ 46

Liotina __________________________ 4^

botanica ___________________ 46

chitienensis __________________ 46

cri'nata ________ _______ 46

cyrloma ______________________ 46

infensa ______________________ 46

loculosa _____________ __i______ 47

(Austroliotia) botanica 13,17,46; pi. 7

(Dentarene) cycloma _ ___ ___ 20

loculosa 13, 17, 46; pi. 7

sp. A ____________ 13, 17, 47; pi. 7

sp. B ____________ 13,17,47; pi. 7

sp. A,_____________________ 47

Page

Littorinidae 13, 17, 59 

loculosa, Liotia 46

Liotina 47

(Dentarene) 13, 17, 46; pi. 7

Lodderia 77

lomaloana, Rissoina (Rissoina) 14, 18, 71; pi. 13

Lophocochlias 77

minutissimus 14, 18, 20, 77; pi. 15

paucicarinatus 14, 18, 77; pi. 15

Lorica angasi 22

Loricella 22

sp. A ______________ 12, 16, 22; pi. 1 

Lucia 23

lucida, Putilla _______ 60

Lucilina 23 

confossus 23, 24 

picta _ .. 24 

russelli 12, 16, S3; pi. 1

sp. A _______________ 12, 16, «; pi. 1

sp. B _______________ 12, 16, «; pi. 1

sp. ________________ 12, 16, 24; pi. 1

Lydiphnis __ ______ 79, 80

eniwetokense __________ 14, 18, 79; pi. 16 

euchilopteron 80

M

maculata, Emarginula __- _ 28

Pseudostomatella (Pseudostomatella) 12,

17, 20, 41; pi. 5

Stomatella 41 

maculatus, Trochus 37

Trochus (Infundibulum) _ _ 37

(Trochus) 12, 16, 20, 37; pi. 4

maculosa, Collonia 50

Leptothyra 13, 17, 20, 50; pi. 8

magus, Gibbula 36

Trochus 36

mandralisci, Rissoa 62

Marmarostoma ______ _ _ 4#> &9

argyrostoma _______ ____ 48

chrysostomus _ 48 

marshallense, Teinostoma (Esmeralda) 14,

18,78; pi. 15

marshallensis, Assiminea nitida _ 75 

Diodora 32

(Elegidion) 12, 16, 31; pi. 3

Leptothyra glareosa ___ 13, 17, 20, 52; pi. 9 

Monilea (Monilea) ____ 12, 16, 40; pi. 5

Rissoina _ 73, 74

(Rissolina) 14, 18, 73; pis. 13, 14

Schizochiton 12, 16,22; pi. 1

Synaptocochlea, 12, 17,42; pi. 5

mateana, Monilea 40

Monilea (Monilea) ______ 12, 16, 40; pi. 5

materinsulae, Rissoina 71

mauritianus, Tectus (Tectus) 12,16,38; pi. 4

Trochus 38

meiauhana, Barleeia (Barleeia) 14, 18, 75; pi. 14 

mcjilana, Rissoina (Schwartziella) 14,

18, 67; pi. 12

Melanoides 5, 15 

menkrawitensis, Cryptoplax 12, 16, 20, 24, 25; pi. 1 

Merelina 63

cheilostoma - 63 

granulosa 63

(Linemera) telkibana _____ 13, 18, 64; pi. 12

(Merelina) pisinna ____ 13, 18, 20, 63; pi. 12

mctalttlana, Arene (Arene) 13, 17, 4s ', pi-7

Zebina (Cibdezebina) 14, 18, 20, 64; pi. 12

Rissoina (Rissoina) ____ 14, 18, 70; pi. 13

mineata, Arene 46

Mineola agapeta _ 39

Minopa _ 37

minutissimus, Haplocochlias 77

Haplocochlias (Lophocochlias) _____ 77

Lophocochlias 14, 18, 20, 77; pi. 15

Monilea 40
96 INDEX

agapeta . 

apicina 

glareosa _.._ 

inepta __ 

lifuana ____ 

mateana _

Page

 39

39

 52

 ____ 50

40

 40

(Monilea) belcheri ______ 12, 16, 41; pi. 5 

lifuana ______________ 12, 16, 40; pi. 5

marshallensis ___________ 12, 16, 40; pi. 5

mateana ____________ 12, 16, 40; pi. 5

monilifera, Turcica ______________ 35 

moniliformis, Neritopsis __________ 55

Monodonta angulifera ____________ 36

cornea _ ________________ 35 

montaqui, Rissoa ________________ 62

Montfortia ____________________ 29 

excentrica _______________________ 30

(Montfortista) excentrica ____________ 30

Montfortista ___________________________ 30

montrouzieri, Stomatella ________________ 41

morana, Putilla (Pseudosetia) _ 13,18,60; pi. 11 

Morchiella _______________________ §5

morrisoni, Euchelus _______________ 36

Turcica (Perrinia) ____ 12, 16, 20, 36; pis. 3, 4

multozona, Rissoina _________________ 69

Munditiella __________________ 77

ammonoceras _________________ 78 

archeri ____________________ 78

parryensis ___________ __ 14, 18, 78; pi. 15

qualum _______________ 14, 18, 77; pi. 15

myersi, Amphithalmus (Cerostraca) ______ 13,

18, 6S; pi. 11

N 

Xacella cernica ________________ 32

Nunnoscuttirn ________________ 30

forsythi ______________________ 30, 31

Neoloricata __________________ gi

nepeanensis, Gabridona _________________ 54

Phasianella _____________________ 54

Nerita _________________________ 55 

albicilln ____________________________ 56

corona __________________ 57

exuvia ___________________ 57

insculpta _______ ____________ 55

lineata _____________________ 56 

peloronta ___________________ 55

plicata _______________________ 56

polita __________________________ 56

pulligera ________________________ 57

radula _______ ____________ 55

umlaasiana _________________ 55 

undata ________________________ 56

virginea ________________________ 57

viridis . ___________ 58

(Amphinerita) insculpta _ 13, 17, 20, 55; pi. 10

polita _______________ 13, 17, 58; pi. 10

(Ritena) palauensis ______ 13,17,56; pi. 10 

undata ______________________ 13, 17, 58

(Theliostyla) semirugosa ______ 13, 17, 58

sp. A ____________ 13,17,56; pi. 10

sp. B ___________ 13,17,57; pi. 10

sp. _ ' 56

sp. ____ 57

Neritidae __________ 13, 17, 55 

Neritilia 14, 57

rubida _ __ ____________ 58 

traceyi ________________ 13, 17, 57; pi. 10

Neritina _______________________ 57

brevispina _____ ____________ 57

jogjacartensis _________________ 20, 58

oualaniensis _ ____________ 57 

pulligera __ _ _____ ____ 57 

rubida _______ _ _ 57

ulanensis ____________________ 57

(Vitta) oualaniensis _____ 13,17,57; pi. 10

Page 

Neritopsidae _____ _______ 13, 17, 55

Neritopsis _______________________ 55

moniliformis ____ ______ 55

radula _______________ 55

(Neritopsis) radula ______ 13, 17, 20, 55; pi. 10

niloticus, Tectus (Rochia) ______ 12, 16, 39; pi. 4

Trochus ________-______ 39 

(Rochia) __________________ 39

intida, Assiminea nitida _______ _ 75 

eniwetokensis, Assiminea __ 14, 18,75; pi. 10 

Hydrocena _______________ 75

marshallensis, Assiminea -__ 75 

nitida, Assiminea _____ 75

Nodularia _______ _ 4

vitiensis _ _ 4 

novem-carinattim, Cyclostrema __________ 80

tiovemcannatum, Vitrinella (Lydiphnis) ___ 80

novemcarinatus, Cyclostremiscus ___ _ 20

Cyclostremiscus (Ponocyclus) 14,

19, 20, SO; pi. 16

O 

oheliscus, Tectus _______________________ 39

Trochus 39

(Ttctus) 39

octoradiata, Patella _ _ 29 

urientalis, Euchelus (Hybochelus) cancellatus ____ 34

Hybochelus cancellatus ___ 12,16,34,35; pi. 3 

Ormastralium ___________ 45

urnata, Iravadia ________ 60

ossea, Hemitoma __ 29, 30 

oualaniensis, Neritina ______ 57

(Vitta) 13, 17, 57; pi. 10 

ovina, Haliotis 25, 26

(Padollus) ______________ 12,16,25; pi. 2

Ovinotis _________ ____ 25

Ovinotis ovina __ _ 25

pactfica, Cynisca __ __ _ 13, 17,49; pi. 8 

Padollus _____ 25 

rubicundus _______________- - 25 

pagodalis, Tectus _ 38 

palauensis, Nerita (Ritena) ___ 13, 17, 56; pi. 10 

panamemis, Vitrinella __________ - 80 

papyrncea, Stomatella __________ 41

Parashiela _____ __ - 64

ambulata _ _ _ 64

beetsi ______________ 13, 18, 64; pi. 12

parasitica, Cochliolepis _______- 81

Parminolia ______ ___ 39

parryensis, Cingula _ _ 61

Cingula (Peringiella) _____ 13, 18, 61 ; pi. 11

Munditiella ___________ 14, 18, 78; pi. 15

Rissoina (Rissoina) ambigua 14, 18, 72; pi. 14

Parvisetia ________________- 60

Patella ________________________ 32

apertura ____ __ 31

barbara _______________ - 32

fissura ______ -__ 27 

graeca _____ 31 

octoradiata 29

plicata _____ 32 

stellaefonnis 32

tricostata 29

vulqata _______________ 32

(Scutellastra) stellaeformis __ 12, 16, 32; pi. 3

Patellidae ___________________- 12, 16, 32

patula, Fossarina _________ _ 36

paucicarinatus, Lophocochlias 14,18,77; pi. 15

peasei, Emarginula 28

petholatus thanus, Turbo (Turbo) 13,

17,47; pi. 7

Turbo _________-__ 47

(Turbo) _________ 13, 17, 20, 47; pi. 7

petrosum, Astralium (Cyclocantha) 43

Page

petrusutn virescens, Astralium 43

pharaonius, Trochus _ 38

Phasianella __ 53

nepeanensis 54

thaanumi 54

variabUis 54

sp. _________________ 13, 17, 53; pi. 10

Phasianeilidae 13, 17, 53

Phosinella 68

phymotis, Stomatia 12, 17, 41; pi. 5

Emarginula (Emarginula) 12, 16, 28; pi. 2

Pecten _________ - 4, 8

peloronta, Nerita 55

Peringiella _ 61

perlatus, Turbo (Marmarostoma) 13, 17, 49

(Senectus) 49

Perrinia S6

petholatus, Turbo (Turbo) __ 13, 17, 20, 47; pi. 7

petrosum, Astralium (Cyclocantha) 43

petrusum virescens, Astralium 43

pharaonius, Trochus 38

picta, Collonia __ 53

Leptothyra _ 13, 17, 53; pi. 9

Lucilina - 24

pictus, Trochus 35 

Pisinna __ 62 

pisinna, Alvania 63 

Merelina (Merelina) 13, 18, 20, 63; pi. 12 

Pisulina 19, 59

adamsiana 59

subpacifica _____ ___ 13, 17, 59; pi. 11 

pisum, Gibbula 36

Plesiotrochus 59

plicata, Nerita 56

Patella - 32

Rissoina 74

(Rissolina) 14, 18, 20, 74; pi. 14

plicatula, Rissoina - 72

polita, Nerita 56

Nerita (Amphinerita) 13, 17, 56; pi. 10

politum, Teinostoma 78

polyps, Schizochiton 22

Ponocyclus SO

Pseudosetia 60

Pseudostomatella 4^

(Pseudostomatella) maculata 12,

17, 20, 41; pi. 5

Ptychodon 3, 14

sp. A _____ 3 

pulchra, Rissoa 68

pulligera, Nerita 57 

Neritina 57

pullus, Turbo 54

punctulum, Rissoa 62

Putilla ________ 60

lucida 60

scillae - 61

semistriata 60

suvaensis 61

(Parvisetia) goikutensis 13, 18, 60, 61; pi. 11

suvaensis 13, 18, 61; pi. 11

(Pseudosetia) morana __ 13, 18, SO; pi. 11 

Pyramidella ambigua 71

pyramis, Tectus (Tectus) ____ 12,16,39 

Trochus 39

Q

quadricarinatus, Euchelus 34 

Euchelus (Euchelus) 12, 16, 33; pi. 3 

Trochus 33

qualum, Munditiella _ _____ 14,18,77; pi. 15 

Teinostoma 77

R

radiatus, Turbo

radula, Nerita .

Neritopsis _.
INDEX 97

Page 

(Xeritopsis) ________ 13, 17, 20, 55; pi. 10

rangiana, Smaragdia ____________________ 59

Smaragdia (Smaragdia) ____13, 17, 58; pi. 11

raunana, Gabrielona __________ 13, 17, 54; pi. 10

rehderi, Tectarius _________________ 21

Tectarius (Subdltotectarius) __________ 13,

17, 59; pi. 11 

rhodostoma, Astraea _______________ 43

Astraea (Astralium) ________ 13, 17, 43; pi. 6

rhodostomus, Trochus ___________ 43

rilebana, Rissoina, (Schwartziella) 14, 18, 67; pi. 12 

Rimula _______________________ 30

blainvilli _________________ 30

exquisita _______ __ 12, 16, 20, SO; pi. 2

sp. ____________ 12,16,30; pi. 2 

Rissoa ambigua _________________ 71

cheilostomn ______________ 63

glabrata ___________________________ 62

gracilis _____________________ 66 

gradata ______________________ 63, 64

invis/bilis ________________ 64

laevis __________________ 61

mandralisci _________________ 62

montaqui ____________________ 62

pulchra ___________________ 68

punctulum ________________ 62

rubra _________________ 75

sabulum ________________ 62

sardea ______________________ 62

scillae ____________________ 60

seminulum ______________ 62

subfusca ________________ 62

turgida ______________________ 60

Rissoidae __..__________ 13, 14, 18, 60 

Rissoina ________________ 60, 66, 70, 72

ailinana ______________________ 8, 71

ambigua _________________ 71

balteata ____________________ 69

browniana ________________ 64

bryerea _____________________ 66

cerithiformis _________________ 69

clathrata _______________________ 68, 69

concinna ________________ 72

coronata __________________ 64

cogtulata _______________ 69

decussata ________________ 67

ephamilla ________________ 73

yigantea _________________ 65

gracilis _______ _ __ _____ 66

inca _______________ 70

indrai ______________________________ 20, 67

kickarayana _______________ 74

marshallensis ______________ 73, 74

materinsulae ________________ 71

multozona __________________ 69

plicata _______________________ 74

plicatula ___________________ 72

gralariformis ________________ 73

semari ____________________ 73

supracostata _____________ 68

tenuistriata ~ ________________ 68

transenna ________________ 69

triticea ___________________ 67

turricula _________________________ 20, 72

(Phosinella) alexisi ________14, 18, 70; pi. 13

balteata ____________ 14, 18, 20, 69; pi. 13

bikiniensis _____________ 14, 18, 69; pi. 13

briggsi ____________ 14, 18, 68; pi. 13 

rlathrata ________ 14, 18, 20, 68; pis. 12, 13

transenna ___________ 14, 18, 20, 69; pi. 13

(Rissoina) abbotti _________ 14,18,70; pi. 13

ailinana _______________ 14, 18, 70; pi. 13

ambigua _______________ 14, 18, 71; pi. 14

parryensis __________ 14, 18, 72; pi. 14

roncinna _______________ 14, 18, 72; pi. 13

ekkanana ______________ 14, 18, 71; pi. 13

qoikulensis _________ 14, 18, 71; pi. 13 

lomaloana _____________ 14, 18, 71 ; pi. 13

Page 

mijana -_______________ 14, 18, 70; pi. 13

wahtensis ______________ 14, 18, 71; pi. 13

sp. A __________ 14, 18, 72; pi. 13 

(Eissolina) bourneae _______ 14, 18, 74', pi. 14

ephamilla ___________ 14, 18, 20, 73; pi. 14

harti __________________ 14, 18, 74; pi. 14

herringi _______________ 14, 18, 74; pi. 14

kickarayana _______ 14,18,74; pi. 14 

marshallensis _______ 14, 18, 73; pis. 13, 14

plicata _____________ 14, 18, 20, 74; pi. 14

turricula _________ 14, 18, 20, 72; pi. 13

sp. B ____________ 14, 18, 75; pi. 14

(Schwartziella) flexuosa __ 14, 18,66; pi. 12

gracilis ________________ 14, 18, 66; pi. 12

indrai ________________ 14, 18, 66; pi. 12

jirikana _______________ 14, 18, 67; pi. 12

mejilana _______________ 14, 18, 67; pi. 12

rilebana _______________ 14, 18, 67; pi. 12

(Zebinella) emnanana _ 14,18,67; pi. 12 

supracostata ___________ 14, 18, 68; pi. 12

tenuistriata _________ 14, 18, 20, 68; pi. 12

Rissolina ____________________ 72, 74

Ritena ________________________________ 56

Rochia _____________________ SS

rosacea, Gena __________ _ 42

Synaptocochlea __________ 12, 17, 20, 42; pi. 5

ruseocincta, Cingula ____________ 61

Cmgula (Peringiella) _______ 13, 18, 61; pi. 11

rotatum, Teinostoma _________________- 78

rubicundus, Padollus ____________ 25

rubida, Neritilia __________________ 58

Neritina _____________ _ _ 57

rubra, Barleeia _______________ 75

Rissoa ______________________ 75

russelli, Lucilina _______________12, 16, 23; pi. 1

sabulum, Kissoa ________________ 62

sagittata, Cellana ___________________ 12, 16, 32

Hclcioniscus _______________ 32

sarcina, Dentarene ___________ __ 46 

sardea, Rissoa ________________ 62

scabriusculus, Euchelus ________ 33

scalanformis, Rissoina _____ 73

Schizochiton _________________________ 1, 19, 21

incisus _____________________________ 21, 22

goikulensis __________ 12, 16, 31, 22; pi. 1

marshallensis _______________ 12, 16, 22; pi. 1

polyps ___________ 22

Schizochitonidae ________________ 12, 16, ./

Schwartziella ___________________________ 66, 67

scillae, Putilla ___________________ 61

Rissoa ___________ ____ 60

Scissurella _____________________________ 26

aedonia _______________ 27

coronata __________ 27

crispata ________ 27

declinans _______ __ 26

equatoria _______ 27

laevigata _______ 26

(Anatnma) equatoria ________ 12, 16,27; pi. 2

(Scissurella) coronata _______12, 16, 27; pi. 2

declinans ____________ 12, 16, 20, 26; pi. 2

Scissurellidae __________________ 12, 16, 20 

Scuteltastra _________________ _________ 32

Scut us ________________________________ SO, 31

antipodes ______ 30

(Xannoscutum) sp. A _____ 12, 16, 31 ; pi. 2

sp. B _____________ 12, 16, 31; pi. 2

tK'mari, Rissoina _ _ _ 73

Smaragdia ________ 59

seminulum, Rissoa ____ _ _ 62

semirugosa, Xerita (Theliostyla) 56 

semistriata, Putilla _______ 60 

setosus, Turbo __________________ 48, 49 

Turbo (Marmarostoma) ___ 13,17,^9; pi. 7 

Sinum lekalekanum ____________ 42

Page

Smaragdia 20, 58

rangiana ___________________ 59 

semari __ ________ 59

(Smaragdia) colei ______ 13, 17, 58; pi. 11

jogjacartensis _ 13, 17, 58; pis. 10, 11

rangiana __________ 13, 17, 58; pi. 11

sp. A ___________ 13, 17, 59; pi. 11

Solariorbis __ _____ - 79

tricarinata _________ 14, 18, 20, 79; pi. 16

sp. _________________ 14, 18, 79; pi. 16

souberbiana, Emarginula 28

souverbiana, Emarginula 28

Emarginula (Subzeidora) 12, 16, 28; pi. 2

stellaeformis, Patella _____ 32

Patella (Scutellastra) _____ 12, 16, 32; pi. 3

stellata, Euchelus __ _ 36

stephensoni, Leucorhynchia 14, 18, 76, 77; pi. 14

Stomatella __ 41

cancellata 34

concinna ______ 41 

maculata 41 

montrouzieri _____ _ 41 

papyracea 41

(Synaptocochlea) concinna _ 42

Stomatellidae _________________ 12, 17, 41

Stomatia _ ___ 41

phymotis _____________ 12, 17, 41; pi. 5

striatus, Cryptoplax 25

subcarinatus, Trochus 37 

Subdltotectarius _________ _ 21, 59 

subfusca, Rissoa ____ 62 

sublathrata, Emarginula __ _ 29 

subpacifica, Pisulina 13, 17,53; pi. 11 

Subzeidora _ 28 

supracostata, Rissoina 68

Rissoina (Zebinella) _____ 14, 18, 68; pi. 12 

suvaensis Euchelus (Herpetopoma) instrictus 12,

16, S3; pi. 3

Putilla (Parvisetia) _____ 13, 18, 61; pi. 11 

Synaptocochlea __ 1^1

concinna ______________ 12, 17, Ifl; pi. 5 

lekalekana ____________ 12,17,42; pi. 5 

marshallensis ___________ 12, 17, 4®', pi- 5 

rosacea ____________ 12, 17, 20, 42; pi. 5

Taramellia _ 63

Tectarius .._______________ _ 21, 59 

coronatus ___ _ 59 

rehderi _ 21 

(Subdltotectarius) rehderi __ 13, 17, 59; pi. 11

Tectus __ 38

bomasensis _____ 20, 39

fenestratus ______ 39

obeliscus _____ 39

pagodalis ___ 38

(Rochia) niloticus __ 12, 16, 39; pi. 4

(Tectus) bomasensis 12, 16, 39; pi. 4

mauritianus 12, 16, 38; pi. 4

pyramis ____ 12, 16, 39

Teinostoma 78

cngebiense _ _ 78

esmeralda _______ 78

politum __ 78

qualuni __ 77

rotatum _ 78

(Esmeralda) engebiense 14, 18, 78; pi. 15

marshallense ________ 14, 18, 78; pi. 15

sp. A ___________ 14, 18, 78; pi. 15

(Leucorhynchia) caledonicum 76

crossei ___ _ 76

telkibana, Merelina (Linemera) _ 13, 18,64; pi- 12

tenuistriata, Rissoina 68 

Rissoina (Zebinella) - 14, 18, 20, 68; pi. 12

Thalotia _____________ 20, 35 

berauensis 19 

elon-gatus 35
98 INDEX

Page 

erinuicus _____________________ 20,35

(Beraua) sp ___________ 12, 16, 35; pi. 3

(Thalotia) berauensis ____ 12,16,35; pi. 3

elongatus _______________ 12,16,35; pi. 3

thanus, Turbo (Turbo) petholatus 13,17,47; pi. 7 

Thatcheria ____________________ 5

vitiensis _________________________ 5

Thcliostyla 56

Tlieodoius corona __________________ 57

(Clithon) corona _____________ 57 

traceyi, Neritilia __________ 13, 17, 57; pi. 10 

transenna, Rissoina _______________ 69

(Phosinella) ________ 14, 18, 20, 69; pi. 13

tncarinata, Leucorhynchia __________ 79 

Solariorbis _____________ 14, 18, 20, 79; pi. 16

Tricolia _______________________________ 54

variabilis ___________________ 55 

(Hiloa) variabilis __________13, 17, 54; pi. 10

sp. A ____________ 13, 17, 55; pi. 10 

tricostata, Patella ________________ 29 

Tridacna ________ __________ 4 

tridentata, Zebina ____________ _ 65

triticea, Rissoina __________________ 67

Trochidae ___________________ 12, 16, 33 

trochlearis, Iravadia _________________ 60

Trochus _______________________ 37 

acutangulus _________________ 39

belcheri ______________________ 41

calcaratus ___________________ 37 

cailiferus _ _________________ 40

conus ______ ___________ 39

heliotropium ____________________ 43

histrio ______________._ 37

histrio ___________________ 37

imperialis __________________ 43

incrassatus ________________ 38

creniferus _________ __ 38

inaculatus ______________________ 37

magus ____________________ 36

mauritianus __________________ 38

niloticus ______________________ 39

obeliscus __________________ 39

pharaonnis ____________________ 38

pictus ___________________ 35

pyramis _ ____________ 39 

quadricarinatus _______________ 33 

rhodostomug ________________ 43

Page

subcurinatus ______ ___ _ 37

tubiferus ___________________ 38

(Infundibulum) calcaratus 43

maculatus _____________________ 37

(Monilea) lifuanus _________ 40

(Monodonta) instrictus __ 33

(Rochia) niloticus ______- _ 39

(Tectus) obeliscus _ ___ _ 39

(Trochus) histrio _____ 12, 16, 20, 37 ; pi. 4

incrassatus 12, 16; 38

maculatus ________ 12, 16, 20, 37; pi. 4

tubiferus 12, 16, 38; pi. 4

tubiferus, Trochus __ ____ _ 38

Trochus (Trochus) 12,16,38; pi. 4

Turhinidae _______ __ 13, 17, 4$

Turbo ____________________________ 43, 47, 66

arqyrostomus ____ __ 27, 48, 49

calcar ______________ __ _ 43 

canaliculatus ____ __- _ 49 

chrysostomus _ 48, 49 

eingillus ________ 61

crassus ____ 49

delphinus ____ _ 42

histrio _____ 37 

petholatus ______ 47

pullus ________________ 54

radiatus ________ 49

setosus ____ 48, 49

zetlandica _ 63

(Marmarostoma) argyrostomus 13,

17, 20, 48; pi. 7

chrysostomus ________ 13, 17, 20, 48; pi. 7

crassus - 13, 17, 49; pi. 8

perlatus -__ 13, 17, 49 

setosus 13, 17, 49; pi. 7

sp. A ____________ 13, 17, 49; pi. 8 

(Ocana) gruneri 49

(Senectus) perlatus ". 49

(Turbo) chrysostomus __ 48

petholatus __ _ 13, 17, 20, 47; pi. 7

thanus ___________13, 17, 47; pi. 7

sp. a . 

sp. b -_. 

Turcica _. 

monilifera

(Perrinia) morrisoni ___ 12, 16, 20, 36; pis. 3, 4 

turgida, Rissoa ___ 60

Page

turrirula, Rissoina 20, 72

Rissoina (Rissolina) __ 14, 18, 20, 72; pi. 13

tuvuthaensis, Haliotis 12, 16, ZS

U

ulanensis, Neritina _ 57

umlaasiana, Nerita - 55

undata, Nerita 56

\trita (Ritena) 13, 17, 56

Vaceuchelus 34

variabilis, Collonia 54

Phasianella 54

Tricolia __ 55

(Hiloa) ___________ 13, 17, 54; pi. 10

virescens, Astralium petrusum 43

virginea, Nerita 57

viridis, Nerita 58

Vitiastraea 21, 45

4

5

81

80

81 

80 

80

pi .16 

75 

57

vitiensis, Nodularia 

Thatcheria 

Vitrinella 

cingulifera 

helicoidea 

panamensis 

(Lydiphnis) novemcarinatum _ 

sp. A _______________ 14, 19, 81

Vitrinellidae 

Vitta -

vulgata, Patella 32

W

waluensis, Astraea (Astralium) 13, 17, 43; pi. 6

Rissoina (Rissoina) 14, 18, 71 ; pi. 13

wellsi, Leptothyra 13, 17, bZ; pi. 9

Z

Zebina 21, 64, 66

abrardi - 21 

tridentata. 65

(Ailinzebina) abrardi .. __ 14, 18, 20, 65; pi. 12

(Cibdezebina) metaltilana, 14, 18, 20, 64 ; pi. 12

(Morchiella) cooperi 14, 18, 65; pi. 12

killeblebana 14, 18, 65; pi. 12

sp. A _______________ 14, 18, 66; pi. 12

Zebinella 67 

zetlandica, Turbo 63

. S. GOVERNMENT PRINTING OFFICE : 1966 O - 212-807
PLATES 1-16
PLATE 1

FIGURES 1-3. Schizuchitott iacinus goikulenxis Ladd, n. subsp. (p. 21).

Holotype, a tail valve, length 10.0 mm, X 5. Palau; late Miocene (Tertiary g). USNM 648208.

4 9. Schizochiton mar^hallensis Ladd, n. sp. (p. 22).

4-6. Holotype, a tail valve, length 8.2 mm, X 5. . E-l, Eniwetok, 870-880 ft; early Miocene (Tertiary /) 

USNM 648209.

7. Paratype A, a head valve, length 5.5 mm, X 5. F-1, Eniwetok, 740-750 ft; late Miocene (Tertiary g). 

USNM 648210.

8. Paratype B, a second valve, length 7.2 mm, X 5. F-1, Eniwetok, 750-760 ft; late Miocene (Tertiary g). 

USNM 648211.

9. Paratype C, a second valve, length (incomplete) 3.4 mm, X 8. 2A, Bikini, 1,030-1,034 ft; early Miocene

(Tertiary /). USNM 648212. 

10-12. Loricella sp. A (p. 22).

10. 11. A head valve, length 1.6 mm. X 8. F-1, Eniwetok, 55-60 ft; Recent. USNM 648215.

12. An intermediate valve, length (minus insertion plates) 2.0 mm, X 8. E-l, Eniwetok, 35-40 ft; Recent.

USNM 648216. 

13 15. Lucilina russelli Ladd, n. sp. (p. 23).

Holotype, a tail valve, length 4.1 mm, X 8. K-1B, Eniwetok, 537-548 ft; probably Pliocene (Tertiary h).

USNM 648217.

16. Lucilina sp. A (p. 23).

A tail valve, length (insertion plates missing) 2.1 mm, X 8. Palau; late Miocene (Tertiary g). USNM 648219.

17. Lucilina sp. B (p. 23).

A tail valve, length 6.5 mm, X 4. Fiji; probably Pliocene (Tertiary h). USNM 648218. 

18,19. Lucilina sp. (p. 24).

An intermediate valve, length 0.9 mm, X 15. Funafuti, 70 ft; Recent. MCZ 28020. 

20, 21. Acanthochitona sp. (p. 24).

An intermediate valve, length 1.1 mm, X 15. E-l, Eniwetok, 770-780 ft; late Miocene (Tertiary g).

USNM 648220. 

22. Cryptoplax cf. C. menkrawitensis Beets (p. 24).

An intermediate valve, length (incomplete) 1.7 mm, X 15. Fiji (sta. 160); Miocene. USNM 648221.

23-27. Cnjptoplax sp. A (p. 24).

23, 24. Head valve, length 1.4 mm, X 20. E-l, Eniwetok, 750-760 ft; early Miocene (Tertiary /). USNM

648222. 

25. Intermediate valve, length 2.1 mm, X 15. 2B, Bikini, 1,891-1,902 ft; early Miocene (Tertiary e). USNM

648223.

26,27. Tail valve, length 1.1 mm, X 20. 2B, Bikini, 1,870-1881 ft); early Miocene (Tertiary e). USNM 648224. 

28-30. Cryptoplax sp. B (p. 25).

28. Intermediate valve, length 7.3 mm, X 5. F-1, Eniwetok, 800-810 ft; late Miocene (Tertiary g). USNM

648225. 

29,30. Tail valve, length 5.5 mm, X 5. F-1, Eniwetok, 720-730 ft; late Miocene (Tertiary g). USNM 648226.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 1

CHITONS
PLATE 2

FIGURES 1,2. Haliotis (Padollnx) ovina Gmelin (p. 25).

Guam specimen, length 58.2 mm, X 1- USGS 20489, Reef facies, Mariana Limestone; Pliocene and Pleistocene. USNM 648227. 

3-5. Haliofa (Padollm) cf. H. clathrata Reeve (p. 26).

3,4. Guam specimen, length 24.8 mm, X 1- USGS 20994, detrital facies, Mariana Limestone; Pliocene and

Pleistocene. USNM 648228. 

5. Tinian specimen, length 15.9 mm, X 2. USGS 21611, limestone terrace probably equivalent to Mariana

Limestone of Guam; Pliocene and Pleistocene. USNM 648229. 

6. Scixsurella (Scismrella) declinanx Watson (p. 26).

Height 0.7 mm, X 20. Drill hole 2B, Bikini Atoll, depth 884-894 ft; late Miocene (Tertiary g). USNM

648230. 

7,8. Scifixurrlla (Scitwiirclla) coronatn Watson (p. 27).

Height 1.3 mm, X 15. Drill hole E-l, Eniwetok Atoll, depth 30-35 ft; Recent. USNM 648329. 

9, 10. .Scm-.'nrMrt (Anatoma) cquatovia Hedley (p. 27).

Height 0.6 mm, X 20. Drill hole on Funafuti Atoll, depth 65 ft; Recent. MCZ 28021. 

11,12. Emarginula (Emarginula) bicanccllata Montrouzier (p. 27).

Height 2.5 mm, X 10. Drill hole on Funafuti Atoll, depth 65-74 ft; Recent. British Mus. 1964, 23. 

13,14. Emarginula (Emaryivnla) cf. E. peazei (Thiele) (p. 28).

Length 3.3 mm, X 10. Drill hole E-l, Eniwetok Atoll, depth 90-110 ft; Recent. USNM 648231. 

15,16. Emarginula (Emarginula) aff. E. clypens A. Adams (p. 28).

Length 4.3 mm, X 10. Drill hole F-l, Eniwetok Atoll, depth 60-70 ft; Recent. USNM 648232. 

17,18. Emarginula (Subzeidorn) xouverbinna Pilsbry (p. 28).

Length 3.0 mm, X 10. Drill hole E-l, Eniwetok Atoll, depth 10-20 ft; Recent. USNM 648233. 

19,20. Emarginula (Xiibzeidnm) sp. A (p. 28).

Length 2.1 mm, X 15. Drill hole 2B, Bikini Atoll, depth 1,807-1,819 ft; early Miocene (Tertiary e). USNM 

648234.

21, 22. Emarginula (Subzcidora) sp. B (p. 29).

Length 2.2 mm, X 15. Drill hole F-l, Eniwetok Atoll, depth 20-45 ft; Recent. USNM 648235.

23. Hemitoma (Hemitoma) sp. (p. 29).

Length 28.8 mm, X 1- Sta, HOB, Vanua Mbalavu, Fiji; Ndalithoni limestone; probably Pliocene (Tertiary

h). USNM 648449. 

24, 25. Hemitoma (Montjortia) bikiniensis Ladd, n. sp. (p. 29).

Holotype, length 4.8 mm, X 6. Drill hole 2, Bikini Atoll, depth 105 ft; Recent. USNM 648236. 

26, 27. Hemitoma (Moutjortia) .sp. A (p. 29).

Length 3.0 mm, X 10. Drill hole E-l, Eniwetok Atoll, depth 35-40 ft; Recent. USNM 648237. 

28,29. Hcmitoma (Monlfortixta) I'xcenlrica (Iredale) (p. 30).

Length (incomplete) 9.2 mm, X 3. From coral pit (USGS 21029) on Espiritu Santo, New Hebrides; Pleistocene or Recent. USNM 648238. 

30, 31. Kimula eocquiifita A. Adams (p. 30).

Length 4.4 mm, X 8. Drill hole 2A, Bikini Atoll, depth 447-453 ft; probably Pliocene. USNM 648239.

32,33. Kimula sp. (p. 30).

Length 1.9 mm, X 15. Drill hole E-l, Eniwetok Atoll, depth 10-20 ft; Recent. USNM 648240.

34,35. Scutus (Nanrwscutum) sp. A (p. 31).

Width 7.1 mm. X 4. Drill hole F-l, Eniwetok Atoll, depth 720-730 ft; late Miocene (Tertiary g). USNM 

648241.

36,37. Sent us (Nannoxcutum) sp. B (p. 31).

Length (incomplete) 5.3 mm, X 4. Drill hole K-1B, Eniwetok Atoll, depth 768-779 ft; late Miocene (Tertiary g). USNM 648242.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 2

 if

GASTROPODS: HALIOTIDAE, SCISSURELLIDAE, AND FISSURELLIDAE
PLATE 3

FIGURES 1,2. Diodora (Elegidion) marshallensis Ladd, n. sp. (p. 31).

Holotype, length 3.4 mm, X 15. E-l, Eniwetok, 700-710 ft; late Miocene (Tertiary g). USNM 648243. 

3,4. Diodora (Elegidion) aff. D. granifera (Pease) (p. 31).

Length (incomplete) 3.0 mm, X 15. Mu-4, Eniwetok, 8 ft; Recent. USNM 648244.

5,6. Diodora (Elegidion) sp. A (p. 32).

Length 14.8 mm, X 3. Palau; late Miocene (Tertiary g). USNM 648245.

7. Patella (Scutellastra) stellaefwmis Reeve (p. 32).

Length 9.1 mm, X 5. F-23-C, Eniwetok, 85-88 ft; probably Recent. USNM 648246.

8. Cellanasp.A (p. 32).

Length 28.2 mm, X 1. USGS 17891, Saipan; probably Recent. USNM 648247. 

9,10. Euchelus (Euchelus) cf. E. quadricarinatus (Dillwyn) (p. 33).

Height 3.7 mm, X 8. K-1B, Eniwetok, 663-674 ft; late Miocene (Tertiary g). USNM 648253.

11 13. Euchelus (Herpetopoma) instrictus (Gould) (p. 33).

Eniwetok specimen, height 4.1 mm, X 8. E-l, 30-40 ft; Recent. USNM 648254. 

14 16. Euchelus (Herpetopoma) instrictus suvaensis Ladd, n. subsp. (p. 33).

Holotype, height 3.6 mm, X 8. Viti Levu, Fiji (sta. 160); early Miocene (Tertiaiy /). USNM 648255.

17-19. Euchehis (Vaceuchelus) angulntus Pease (p. 34).

Eniwetok specimen height 3.0 mm, X 8. E-l, 40-50 ft; Recent. USNM 648256.

20-22. Euchelus (Vaci-uchelufi) sp. A (p. 34).

Eniwetok specimen, height 2.8 mm, X 8. E-l, 30-40 ft; Recent. - USNM 648257.

23,24. Hybochelux cnnccllatus orientalis Pilsbry (p. 34).

Eniwetok specimen, height^incomplete) 3.6 mm, X 8. E-l, 50-60 ft; Recent. USNM 648258.

25,26. Hybochelus kavoricus Ladd (p. 35).

Holotype, height 102 mm. Diameter (incomplete) 12.2 mm, X 2. Ndalithoni Limestone, sta. HOB. Vanua 

Mbalavu, Fiji; probably Pliocene (Tertiary h). Rochester Univ. Mus. Nat. History 13045.

27,28. Thnlotin (Thalotia) berauensis (Beets) (p. 35).

Eniwetok specimen, height 5.2 mm, X 5. K-1B: 1,070-1,081 ft; early Miocene (Tertiary /). USNM 648259.

29. Thnhitin (Thalotia) aff. T. clongatus (Wood) (p. 35).

Guam specimen, height 22.2 mm, X 2. Mariana Limestone; (USGS 20574); probably Pleistocene. USNM 

648260.

30. Thalotia (Beraua) sp. (p. 35).

Saipan specimen, height 9.7 mm, X 3. Inequigranular facies, Tagpochau Limestone (USGS 17904); Miocene. 

USNM 648261.

31. Tnrcica (Perrinia) monisoni Ladd, n. sp. (p. 36).

Holotype, diameter 2.8 mm, X 10. Bikini reef; Recent. USNM 648262.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 3

26 31

GASTROPODS: FISSURELLIDAE, PATELLIDAE, AND TROCHIDAE
PLATE 4

FIGURES 1-5. Turcica (Perrinia) monisoni Ladd, n. sp. (p. 36).

1,2. Holotype, height 3.3 mm, X 10. Bikini reef; Recent. USNM 648262.

3-5. Drill hole 2B, Bikini, 1,461-1,472 ft; early Miocene (Tertiary /). USNM 648263, X 10.

6,7. Gibbida (Gibbula) engebiensis Ladd. n. sp. (p. 36).

Holotype, height 2.9 mm, X 10. K-1B, Eniwetok, 926-936 ft; early Miocene (Tertiary /). USNM 648264.

8 10. Fossarina ( Minopa) hoffmeisteri Ladd, n. sp. (p. 37).

Holotype, height 4.1 mm, X 8. Mu-4, Eniwetok, 40 ft; Recent. USNM 648265. Fig. 10 uncoated to show

color pattern. 

11-13. Astele (Callistele) engebiemsis Ladd, n. sp. (p. 37).

Holotype, height 2.7 mm, X 10. K-1B, Eniwetok, 968-978 ft; early Miocene (Tertiary /). USNM 648266. 

14.15. TrochuK (Truchus) maculatus Linnaeus (p. 37).

Guam specimen, height 20.2 mm, X 2. USGS 20636; Mariana Limestone; Pliocene and Pleistocene. USNM

648248. 

16-18. Trochus (Trochus) hisLiio (Reeve) (p. 37).

Height 11.2 mm, X 2. F-l, Eniwetok, 110-120 ft; probably Recent. USNM 648249. 

19. Trochus (Trochus) tubiferus Kiener (p. 38).

Height (incomplete) 20.8 mm, X 2. Tongatabu, Tonga (sta. 2); probably Pleistocene. B. P. Bishop Mus.

geology No. 1339. 

20-22. Clnnculus (Clanculus) clnnguluides fijie.nftis Ladd (p. 38).

Holotype, height 9.6 mm, X 3. Vanua Mbalavu, Fiji (sta. HOB); Ndalithoni Limestone; probably Pliocene 

(Tertiary h), Rochester Univ. Mus. Nat. History 13044.

23. Tecluit (Tectm) mauritianus (Gmelin) (p. 38).

Height (incomplete) 16.5 mm, X 2. Espiritu Santo, New Hebrides (USGS 21028); probably Pleistocene. 

USNM 648250.

24. TectuK (Tectm) cf. T. bomnxemd* (Martin) (p. 39).

Holotype, height 15.1 mm, X 2. Viti Levu, Fiji (sta. MR-20); probably Pliocene (Tertiary h). USNM 

648251.

25. TcctiiK (Rochin) iiilolicxx (Linnaeus) (p. 39).

Height (incomplete) 100 mm, X 0.75. Espiritu Santo, New Hebrides (USGS 21029); Pleistocene or Recent. 

USNM 648252.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 4

GASTROPODS: TROCHIDAE
PLATE 5

FIGURES 1-4. lucnida (Parminolia) apicina (Could) (p. 39).

I,2. Height 3.9 mm, X 6. Eniwetok speciment, E-l, 60-70 ft; Recent. USNM 648267. 

3,4. Height 4.9 mm, X 6. Gould's type from Australia; Recent. USNM 24159. 

5-8. Monilea (Monilea) mateana Ladd (p. 40).

5,6. Holotype, height 7.0 mm, X 4. Viti Levu, Fiji, (sta. 160); Miocene (Tertiary /). B. P. Bishop Mus.

Geol. 1196.

7,8. Specimen from type locality, height 6.7 mm, X 4. USNM 648392. 

9-12. Monilea (Monilea) murshallensis Ladd, n. sp. (p. 40).

9,10. Holotype, height 3.9 mm, X 6. K-1B, Eniwetok, 1,248-1,259 ft; early Miocene (Tertiary e). USNM 

648270.

II,12. Paratype A, height 4.1 mm, X 6. Bikini, core from depth 235 ft; post-Miocene. USNM 648268. 

13,14. Monilea (Monilea) lijuana Fischer (p. 40).

Eniwetok specimen, height 5.2 mm, X 4. En-4, 2ft; Recent. USNM 648269. 

15,16. Monilea (Monilea) belcheri (Philippi) (p. 41).

Fiji specimen, height 8.6 mm, X 4. Sta. 320, Viti Levu, Fiji; Miocene. B. P. Bishop Mus., geology No. 1235. 

17,18. Pseudostomatella (Pseudostomatella) maculata (Quoy and Gaimard) (p. 41).

Fiji specimen, height 10.5 mm, X 3. Sta. HOB, Vanua Mbalavu; Nadalithoni Limestone; probably Pliocene

(Tertiary h). USNM 648271. 

19. Slomatia cj. S. phymotis Helbling (p. 41).

Guam specimen, height 7.3 mm, X 3. USGS 20534; probably Mariana Limestone; Pliocene and Pleistocene.

USNM 648272. 

20-23. Synaptocochlea concinna (Gould) (p. 41).

Eniwetok specimen, height 3.0 mm, X 10. F-l, 60-70 ft; probably Recent. USNM 648273. Figures 21 and

23 are uncoated and show color pattern. 

24. Synaptocochlea rosacea (Pease) (p. 42).

Eniwetok specimen, length 4.5 mm, X 12. E-l, 30-35 ft; Recent. USNM 648274. 

25,26. Synaptocochlea lekdlekana (Ladd) (p. 42).

Holotype, diameter 11.5 mm, X 3. Sta. HOC, Vanua Mbalavu, Fiji, Nadalithoni Limestone; probably Pliocene (Tertiary h). Rochester Univ. Mus. Nat. History 13051. 

27,28. Synaptocochlea marshallensis Ladd, n. sp. (p. 42).

Holotype, height 1.5 mm, X 12. Eniwetok, K-1B, 757-769 ft; late Miocene (Tertiary g). USNM 648275.

29,30. Anyaria delphinus (Linnaeus)? (p. 42).

Guam specimen, height 30.2 mm, X 1- USGS 20720; Alifan Limestone; (Tertiary g or h). USNM 648276.

31 34. Angaria. delphinus (Linneaus) (p. 42).

Fijian specimens: 31, height 24.6 mm, X 1-7. 32-34, height 13.9 mm, X 2. Both specimens from sta. 160 on 

Walu Bay, Viti Levu; Suva Formation; (Tertiary /). Fig. 31 is B. P. Bishop Mus., geology No. 1216; figs. 

32-34 are USNM 648393.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 5

GASTROPODS: TROCHIDAE, STOMATELLIDAE,AND ANGARIIDAE
PLATE 6

FIGURES 1-5. Astraea (Astralium) rhodostoma (Lamarck) (p. 43).

1,2. Saipan specimen, height 29.1 mm, X 1%. USGS 21407; Tanapag Limestone; probably Pleistocene.

USNM 648285.

3-5. New Hebrides specimen, height about 25 mm, X !% Unapong, Eromanga; Quaternary. 

6. Astraea (Astralium) aff. A. rhodostoma (Lamarck) (p. 43).

Rubber cast, height 19.7 mm, X Wz. From dolomitic limestone at depth of 1,006 ft, Main boring, Funafuti

Atoll; probably Pleistocene. USNM 648286. 

7 9. Astraea (Astralium) eniwetokensis Ladd, n. sp. (p. 43).

Holotype, height 7.9 mm, X 3. Drill hole F-l, Eniwetok. 790-800 ft; late Miocene (Tertiary g). USNM

648290. 

10 12. Astraea (Axtralium) walucjisis Ladd, n. sp. (p. 43).

Holotype, height 12.9 mm, X 3. Viti Leva, Fiji (sta. 160); early Miocene (Tertiary /) USNM 648291. 

13 15. Astraea (Astralium) sp. A (p. 44).

Eniwetok specimen, height (incomplete) 11.2 mm, X 3. F-l, 840-850 ft; late Miocene (Tertiary g). USNM

648292. 

16-18. Astraea (Astralium) sp. B (p. 44).

Bikini specimen, height 1.8 mm, X 15. Drill hole 2, from core at 115 ft; Recent. USNM 648293. 

19,20. Astraea (Astralium) sp. C (p. 44).

Eniwetok operculum, height 2.8 mm, X 5. K-1B, 937-947 ft; early Miocene (Tertiary /). USNM 648294.

21-23. Astraea (Bellastraea) sp. D (p. 44).

Holotype. height 1.1 mm, X 10. K-1B, Eniwetok, 841-853 ft; late Miocene (Tertiary g). USNM 648295. 

24-26. Astraea (Bellastraea) sp. E (p. 44).

Eniwetok specimen, height 1.2 mm, X 10. K-1B, 1,196-1,207 ft; early Miocene (Tertiary e). USNM 648296. 

27 29. Astraea (Vitiastraea) holmesi Ladd, n. sp. (p. 45).

Holotype, height 2.4 mm, X 10. Viti Levu, Fiji (sta. 160); early Miocene (Tertiary /). USNM 648297.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 6

20

GASTROPODS: TURBINIDAE
PLATE 7

FIGURES 1 6. Arene (Arene) metaltilana Ladd, n. sp. (p. 45).

1-3. Holotype, height 1.2 mm, X 20. 2B, Bikini, 1,702-1,713 ft; early Miocene (Tertiary e). USNM 648298. 

4-6. Paratype, height 1.2 mm, X 20. 2B, Bikini, 2,297-2,307 ft; early Miocene (Tertiary e). USNM 648299. 

7,8. Arene (Arene) sp. A (p. 45).

Bikini specimen, height 2.3 mm, X 15. 2A, 742-747 ft; late Miocene (Tertiary g). USNM 648300. 

9 11. Liotina (Austroliotia) cf. L. botanica (Hedley) (p. 46).

Holotype, height 1.4 mm, X 10. F-4-A, Elugelab, Eniwetok, 6-12 ft; Recent, USNM 648301. 

12-14. Liotina (Dentarene) loculosa (Gould) (p. 46).

Eniwetok specimen, height 3.6 mm, X 6. E-l, 110-120 ft: probably Recent. USNM 648302. 

15 17. Liotina (Dentarene) sp. A (p. 47).

Eniwetok specimen, height (incomplete) 1.9 mm, X 8. E-L 2,590-2,600 ft; early Miocene, (Tertiary e).

USNM 648303. 

18 20. Liotina (Dentarene) sp. B (p. 47).

Bikini specimen, height (incomplete) 1.4 mm, X 8. 2B, 1,629-1,639 ft; early Miocene (Tertiary /). USNM

648304. 

21,22. Turbo (Turbo) petholatus Linnaeus (p. 47).

21. Guam specimen, height (incomplete) 23.8 mm, X 1%. USGS 20653; Agana Argillaceous Member of Mariana 

Limestone; Pliocene and Pleistocene. USNM 648277.

22. Guam specimen, height 29.4 mm, X !% USGS 20720; Alifan Limestone; (Tertiaiy g or h). USNM 

648278.

23. Turbo (Turbo) petholatus thanus Ladd (p. 47).

Fiji specimen, height 23.2 mm, X 2. Sta. 160, Viti Levu; early Miocene (Tertiary /). USNM 648279.

24. Turbo (Marmarostoma) chrysostomus Linnaeus (p. 48).

Guam specimen, height 22.0 mm, X 2. USGS 20636, Agana Argillaceous Member of the Mariana Limestone;

Pliocene and Pleistocene. USNM 648280. 

25,26. Turbo (Marmarostoma) argyrostomus Linnaeus (p. 48).

25. Saipan specimen, height (incomplete) 59.5 mm, X 1. USGS 17387; Tanapag Limestone; Pleistocene. USNM 

648281.

26. Guam specimen, height (incomplete) 62.6 mm, X 1- USGS 20679; Agana Argillaceous Member of Mariana Limestone; Pliocene and Pleistocene. USNM 648282. 

27. Turbo (Marmarostoma) setosus Gmelin? (p. 49).

Rubber cast from Funafuti, height 24 mm, X 1%- Made from core piece 276 from depth of 526-546 ft; 

post-Miocene. USNM 648283.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 7

25

GASTROPODS: TURBINIDAE
PLATE 8

FIGURES 1,2. Turbo (Marmarostoma) crassus Wood (p. 49).

Tonga specimen, height 79.3 mm, X 1- Near Houma, Tongatabu; probably Pleistocene. 

3,4. Turbo (M armarostoma) sp. A (p. 49).

Fiji rubber cast and internal mold; height (of internal mold) 25.0 mm, X 1%. Sta. 295, Viti Levu; Suva Formation; early Miocene (Tertiary /). B. P. Bishop Mus., geology No. 1228. 

5-7. Cynisca pacifica Ladd, n. sp. (p. 49).

Holotype, height 4.1 mm, X 8. E-l, Eniwetok, 1,000-1,010 ft; early Miocene (Tertiary /). USNM 648284.

8 13. Lcptothyra maculosa (Pease) (p. 50).

Eniwetok specimen, height 1.7 mm, X 20. E-l, 40-45 ft; Recent. USNM 648305. Figs. 9, 11, 13 uncoated

to show color pattern. 

14-22. Lcptothyra inepta (Gould) (p. 50).

14-18. Eniwetok specimen, height 2.8 mm, X 10. Mu-4, 40 ft, 6 in. to 41 ft; Recent. USNM 648306. Figs. 15

and 17 uncoated to show7 color pattern.

19-22. Gould's type USNM 1372, height 2.3 mm, X 10. Kagoshima, Japan; Recent, Fig. 20 uncoated to 

show7 color pattern.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 8

18

GASTROPODS: TURBINIDAE
PLATE 9

FIGURES 1-3. Leptothyra harlani Ladd, n. sp. (p. 51).

Holotype, height 1.9 mm, X 12. K-1B, Eniwetok, 663-674 ft; late Miocene (Tertiary g). USNM 648307.

4-6. Leptothyra aff. L. laeta Montrouzier (p. 51).

Eniwetok specimen, height 2.9 mm, X 10. K-1B, 957-968 ft; early Miocene (Tertiary /). USNM 648312.

7-9. Leptothyra aff. L. Candida (Pease) (p. 51).

Eniwetok specimen, height 1.7 mm, X 15. BO-2-1, depth 7 in.; Recent. USNM 648308.

10-12. Leptothyra balnearii Pilsbry (p. 51).

Eniwetok specimen, height 0.7 mm, X 15- F-l, 55-60 ft; Recent. USNM 648309. 

13-15. Leptothyra wellsi Ladd, n. sp. (p. 52).

Holotype, height 0.9 mm, X 25. F-l, Eniwetok, 690-700 ft; late Miocene (Tertiary g). USNM 648310.

16 20. Leptothyra glareosa marshallensis Ladd, n. subsp. (p. 52).

16-18. Holotype, height 2.3 mm, X 12. USNM 648313;

19-20. Operculum from paratype, USNM 648314, maximum diameter 1.1 mm, X 12; both Recent; Bikini lagoon,

depth 30 fathoms. 

21-23. Leptothyra picta (Pease) (p. 53).

Eniwetok specimen, height 2.1 mm. X 12. E-l, Eniwetok, 35-40 ft; Recent. USNM 648315.

24-26. Leptothyra emenana Ladd, n. sp. (p. 53).

Holotype, height 2.7 mm, X 12. F-l, Eniwetok, 940-950 ft; early Miocene (Tertiary /). USNM 648316.

27-29. Leptothyra sp. A (p. 53).

Eniwetok specimen, height 2.0 mm, X 12. K-1B, 642-653 ft; late Miocene (Tertiary g). USNM 648318.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 9

26 27 " ' 28

GASTROPODS: TURBINIDAE
PLATE 10

FIGURES 1-5. Gabrielona raunana Ladd, n. sp. (p. 54).

1,2. Holotype, height 1.4 mm, X 30. F-l, Eniwetok, 20-45 ft; Recent. Fig. 2 uncoated to show color pattern.

USNM 648319.

3. Paratype A, height 2.0 mm, X 15. F-l, Eniwetok, 20-45 ft; Recent. USNM 648320. 

4,5. Operculum, paratype C, maximum diameter 0.8 mm, X 40. F-15-A, Eniwetok, 26-29 ft; Recent. USNM

648322. 

6,7. Tricolia (Hiloa) variabilis (Pease) (p. 54).

6. Eniwetok specimen, height 1.4 mm, X 15. E-l, 30-40 ft; Recent. USNM 648323.

7. Eniwetok specimen, height 1.9 mm, X 15. E-l, 40-45 ft; Recent. USNM 648324.

8. AsNiminea nitida pniivetukensis Ladd, n. subsp. (p. 75).

Holotype, height 1.8 mm, X 15. K-1B, Enwetok, 831-842 ft; early Miocene (Tertiary /). USNM 648325.

9. Tricolia (Hiloa) sp. A (p. 55).

Fiji specimen, height 0.9 mm, X 30. Viti Levu (sta. 160); early Miocene (Tertiary /). USNM 648326.

10,11. Phasianella sp. (p. 53).

Eniwetok specimen, maximum diameter 3.4 mm, X 8. K-1B, 841-853 ft; late Miocene (Tertiary g). USNM

648327. 

12 14. Neritopsis (Neritopsis) radula Linnaeus (p. 55).

Eniwetok specimen, height 2.8 mm. F-l, 960-970 ft; early Miocene (Tertiary /). USNM 648238. Figs. 12 and

13 are X 10; fig. 14 is X 15. 

15,16. Nerita (Amphinerila) insculpta Recluz (p. 55).

Eniwetok specimen, height 4.6 mm, X 5. F-l, 690-700 ft; late Miocene (Tertiary g). USNM 648332.

17,18. Nerita (Amphinerita) aff. N. polita Linnaeus (p. 56).

Holotype, height 3.4 mm, X 8. F-l, Eniwetok 930-940 ft; early Miocene (Tertiary /). USNM 648333.

19. Nerita (Ritena) palauensis Ladd, n. sp. (p. 56).

Holotype, height (incomplete) 17.3 mm, X 2. Auluptagel, Palau (USGS 23642); base of Palau Limestone;

late Miocene. USNM 648330. 

20,21. Nerita (Theliostyla) sp. A (p. 56).

Fiji specimen, height 11.3 mm, X 3. Viti Levu (sta. 95); probably Miocene. B. P. Bishop Mus., geology

No. 1195. 

22. Nerita (Theliostyla) sp. B (p. 57).

Fiji specimen, diameter 31.0 mm, X 1- Mango (sta. M2D); probably Miocene. USNM 648331. 

23-25. Neritina (Vitta) oualaniensis Lesson (p. 57).

23,24. Guam specimen, height 6.3 mm, X 5. USGS 21377. USNM 648334.

25. Guam specimen, height (incomplete) 5.0 mm, X 5. USGS 20600; both specimens from Mariana Limestone; Pliocene and Pleistocene. USNM 648335.

26,27. Neritilia traceyi Ladd (p. 57).

Holotype, height 1.9 mm. X 12. 2B, Bikini, 2,154-2,165 ft; early Miocene (Tertiary e). USNM 648336.

28-31. Smnragdia (Smaragdin) jugjacartensis (Martin) (p. 58).

28,29. Eniwetok specimen, height 5.2 mm, X 6. F-l, 830-840 ft; late Miocene (Tertiary g). USNM 648337. 

30,31. Two specimens from hole K-1B on Eniwetok to show variation in color pattern.

30. From a depth of 841-853 ft; late Miocene (Tertiary g). USNM 648401, X 10.

31. From a depth of 873-884 ft; early Miocene (Tertiary /). USNM 648402, X 10.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 10

31

GASTROPODS: PHASIANELLIDAE, NERITOPSIDAE, NERITIDAE, AND ASSIMINEIDAE
PLATE 11

FIGURES 1,2. Smaragdia (Smaragdia) jogjacartensis (Martin) (p. 58).

Palau specimen, height 2.6 mm, X 10. Goikul Peninsula, Babelthuap (USGS 21308); late Miocene (Tertiary

g). USNM 648403. 

3,4. Smaragdia, (Smaragdia) aff. S. rangiana (Recluz) (p. 58).

Palau specimen, height (incomplete) 3.2 mm, X 10. Goikul Peninsula, Babelthuap (USGS 21308); late Miocene (Tertiary g). USNM 648338. 

5 7. Smaragdia (Smaragdia) colei Ladd, n. sp. (p. 58).

5,6. Holotype, height 5.6 mm, X 6. F-l, Eniwetok, depth 880-890 ft; early Miocene (Tertiary /). USNM

648339.

7. Paratype, height 3.8 mm, X 8. F-l, Eniwetok, depth 830-840 ft; late Miocene (Tertiary g). USNM 648405. 

8,9. Smaragdia (Smaragdia) sp. A (p. 59).

Eniwetok specimen, height 1.4 mm, X 20. K-1B, 715-727 ft; late Miocene (Tertiary g). USNM 648340. 

10. Pisulina subpacifica Ladd, n. sp. (p. 59).

Holotype, height 1.2 mm, X 20. 2B, Bikini, 789-799 ft; late Miocene (Tertiary g). USNM 648341.

11 13. Tectarius (Subditotectarius) rehderi Ladd, n. sp. (p. 59).

Holotype, height 2.8 mm, X 12. 2A, Bikini, 1,051-1,057 ft; early Miocene (Tertiary /). USNM 648342.

14,15. Iravadia gardnerae Ladd, n. sp. (p. 60).

Holotype, height 3.3 mm, X 10. K-1B, Eniwetok, 831-842 ft; late Miocene (Tertiary g). USNM 648343.

16,17. Putilla (Pseudosetia) morana Ladd, n. sp. (p. 60).

Holotype, height 1.1 mm, X 25. E-l, Eniwetok, 1,805-1,835 ft; early Miocene (Tertiary e). USNM 648344.

18 20. Putilla (Parvisetia) goikulensis Ladd, n. sp. (p. 60).

18,19. Holotype, height 1.1 mm, X 30. USNM 648345.

20. Paratype, height 0.9 mm, X 30. Both specimens Goikul Peninsula, Babelthuap, Palau (USGS 21308);

late Miocene (Tertiary g). USNM 648346. 

21,22. Putilla (Parvisetia) suvaensis, Ladd, n. sp. (p. 61).

Holotype, height 0.9 mm, X 30. Suva formation (sta. FB-20), Viti Lcvu, Fiji; early Miocene (Tertiary

/). USNM 648347. 

23,24. Cingula (Peringiella) parryensis Ladd, n. sp. (p. 61).

Holotype, height 1.7 mm, X 20. E-l, Eniwetok, 700-710 ft; late Miocene (Tertiary g). USNM 648348.

25,26. Cingula (Peringiella) cf. C. roseocincta (Suter) (p. 61).

Palau specimen, height 1.0 mm, X 30. Goikul Peninsula, Babelthuap (USGS 21304); late Miocene (Tertiary

g). USNM 648349. 

27-31. Amphithalmus (Cerostraca) jeffcoati Ladd, n. sp. (p. 62).

27,28. Holotype, a smooth shell, height 1.9 mm, X 15. E-l, Eniwetok, 840-850 ft; late Miocene (Tertiary g).

USNM 648350. 

29,30. Paratype A, a weakly ribbed shell, height 1.9 mm, X 15. K-1B, Eniwetok, 968-978 ft; early Miocene

(Tertiary /). USNM 648351. 

31. Paratype B, a strongly ribbed .shell, height 2.3 mm, X 15. E-l, Eniwetok, 1,010-1,020 ft; early Miocene

(Tertiary /). USNM 648352. 

32,33. Amphithalmus (Cerostraca?) myersi Ladd, n. sp. (p. 62).

Holotype, height 1.5 mm, X 20. E-l, Eniwetok, 770-780 ft; late Miocene (Tertiary g). USNM 648353.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 11

27

GASTROPODS: NERITIDAE, LITTORINIDAE, IRAVADIIDAE, AND RISSOIDAE
PLATE 12

FIGURES 1. Amphithnlmtm (Pisiniui) bikiriiensis Ladd, n. sp. (p. 62).

Holotype, height 1.7 mm, X 20. 2B, Bikini, 1,839-1,850 ft; early Miocene (Tertiary e). USNM 648354.

2. Alvania (Taramellia) corayi Ladd, n. sp. (p. 63).

Holotype, height 1.6 mm, X 20. Mu-4, Eniwetok, 35-36 ft; Recent. USNM 648355.

3. Alvania (Taramellia) kenneyi Ladd, n. sp. (p. 63).

Holotype, height 0.8 mm, X 30. E-l, Eniwetok, 1,746-1,777 ft; early Miocene (Tertiary e). USNM 648356. 

4,5. Merelina (Merelina) pisinna (Melvill and Standen) (p. 63).

Eniwetok specimen, height 1.9 mm, X 15. E-l, 850-860 ft; late Miocene (Tertiary g). USNM 648357. 

6,7. Merelina (Linemera) telkibana Ladd, n. sp. (p. 64).

Holotype, height 1.9 mm, X 15. USGS 21301, Goikul Peninsula, Babclthuap, Palau; late Miocene (Tertiary g).

USNM 648358. 

8,9. Parashiela beetsi Ladd, n. sp. (p. 64).

Holotype, height 1.4 mm, X 20. F-8-C, Eniwetok, 19-22 ft; Recent. USNM 648368. 

10. Zebina (Cibdezebina) metaltilana Ladd, n. sp. (p. 64).

Holotype, height 3.5 mm, X 10. 2B, Bikini, 1,860-1,870 ft; early Miocene (Tertiary e). USNM 648359. 

11,12. Zebina (Morchiella) cf. Z. cooperi (Oliver) (p. 65).

Eniwetok specimen, height 5.7 mm. E-l, 110-120 ft; Recent. USNM 648361. Fig. 11, X 6; fig. 12, X 12.

13,14. Zebina (Morchiella) killeblebana Ladd, n. sp. (p. 65).

13. Holotype, height 5.6 mm, X 6. E-l, Eniwetok, 960-970 ft; early Miocene (Tertiary /). USNM 648363.

14. Paratype, height 3.2 mm, X 8. F-l, Eniwetok, 930-940 ft; early Miocene (Tertiary /). USNM 648364.

15 18. Zebina (Ailinzebina) abrardi Ladd, n. sp. (p. 65).

15,16. Holotype, height 3.9 mm, X 8. Bikini lagoon at depth of 20 fathoms; Recent. USNM 648365.

17. Paratype A, height 2.9 mm, X 10. En-4, Eniwetok, 11 ft; Recent. USNM 648366.

18. Paratype B, height (incomplete) 2.3 mm, X 10. 2B, Bikini, 1,450-1,461 ft; early Miocene (Tertiary e). 

USNM 648367.

19. Zebina? sp. A (p. 66).

Bikini specimen, height 2.7 mm, X 12. 2B, depth 2,112-2,128 ft; early Miocene (Tertiary e). USNM 648370.

20. Rissoina (Schwartziella) gracilis (Pease) (p. 66).

Tongan specimen, height 3.0 mm, X 10. Tongatabu at altitude of 35 ft (B. P. Bishop Mus., geology No. 1340);

probably Pleistocene. 

21,22. Rissoina (Schwartziella) aff. R. flexuosa Gould (p. 66).

Eniwetok specimen, height 4.0 mm, X 8. E-l, 40-45 ft; Recent. USNM 648382.

23,24. Rissoina (Schwartziella) aff. R. indrai Beets (p. 66).

Eniwetok specimen, height 7.7 mm, X 5. F-l, depth 930-940 ft; early Miocene (Tertiary /). USNM 648383.

25,26. Rissoina (Schwartziella) mejilana Ladd, n. sp. (p. 67).

Holotype, height 2.8 mm, X 12. K-1B, Eniwetok, 831-842 ft; early Miocene (Tertiary /). USNM 648384.

27,28. Rissoina (Schwartziella) jirikana Ladd, n. sp. (p. 67).

Holotype. height 2.3 mm. X 15. 2B. Bikini. 1,440-1,451 ft; early Miocene (Tertiary e). USNM 648385.

29,30. Rissoina (Schwartziella) rilebana Ladd, n. sp. (p. 67).

Holotype, height 3.1 mm, X 10. 2B, Bikini, 778-789 ft; late Miocene (Tertiary g). USNM 648386.

31,32. Rissoina (Zebinella) emnanana Ladd. n. sp. (p. 67).

Holotype, height 4.8 mm, X 8. E-l, Eniwetok, 1,010-1,020 ft; early Miocene (Tertiary /). USNM 648387.

33,34. Rissoina (Zebinella) tenuislriata Pease (p. 68).

Eniwetok specimen, height 5.5 mm, X 8. En-4, 5% ft; Recent. USNM 648388. 

35,36. Rissoina (Zebinella) aff. R. supracostata Garrett (p. 68).

Eniwetok specimen, height (incomplete) 12.4 mm, X 5. E-l, depth 890-900 ft; early Miocene (Tertiary /).

USNM 648389. 

37. Rissoina (Phosinclla) clathmta A. Adams (p. 68).

New Hebredu specimen, described by Abrard, height (incomplete) 8.7 mm, X 4.6. Island of Malekula; Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 12

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GASTROPODS: RISSOIDAE

36

14

37
PLATE 13

FIGURES 1,2. Rissoina (Phosinella) clathrata A. Adams (p. 68).

Fijian specimen, height 7.2 mm, X 5. Suva Formation, Viti Levu, (sta. 160); early Miocene (Tertiary /).

USNM 648391. 

3,4. Rissoina (Phosinella) briggsi Ladd, n. sp. (p. 68).

Holotype, height 4.3 mm, X 8. Goikul Peninsula, Babelthuap, Palau (USGS 21301; late Miocene (Tertiary

g). USNM 648390. 

5-8. Rissoina (Phosinella) balteata Pease (p. 69).

5,6. Bikini specimen, height 3.7 mm, X 8. 2A, depth 38-40 ft; Recent. USNM 648394.

7,8. Eniwetok specimen, height 3.7 mm, X 8. E-l, depth 880-890 ft; early Miocene (Tertiary /). USNM

648395. 

9,10,17,18. Rissoina (Phosinella) bikiniensis Ladd, n. sp. (p. 69).

9, 10. Holotype, height 4.9 mm, X 8. 2A, Bikini, 1,056-1,063 ft; early Miocene (Tertiary /). USNM 648396. 

17,18.Paratype, height 3.6 mm, X 6. E-l, Eniwetok, 1.746-1,777 ft; early Miocene (Tertiary e). USNM

648400. 

11,12. Rissoina (Phosinella) transenna Watson (p. 69).

Eniwetok specimen, height 3.6 mm, X 10. Mu-4, 40 ft; Recent. USNM 648397. 

13-16. Rissoina (Phosinella) alexisi Ladd. n. sp. (p. 70).

13, 14. Holotypo, height 2.7 mm. X 12. F-l, Eniwetok, 1.110-1,120 ft; early Miocene (Tertiary e). USNM

648398. 

15,16. Paratype, height 2.5 mm, X 12. F-l, Eniwetok, 1,100-1,110 ft; early Miocene (Tertiary e). USNM

648399. 

19-21. Rissoina (Rissoina) abbotti Ladd, n. sp. (p. 70).

19. Holotype, height (incomplete) 4.9 mm, X 6. 2A, Bikini, 1,061-1,067 ft; early Miocene (Tertiary /). USNM

648371. 

20.21. Paratype, height (incomplete) 8.1 mm, X 4. Goikul Peninsula, Babelthuap, Palau (USGS 21301); late

Miocene (Tertiary g). USNM 648372. 

22 25. Rissoina (Rissoina) mijana Ladd, n. sp. (p. 70).

22,23. Slender specimen, height 3.3 mm, X 10. K-1B, Eniwetok, 968-978 ft; early Miocene. (Tertiary /).

USNM 648373. 

24,25. Holotype, height (incomplete) 4.3 mm, X 8. E-l, Eniwetok, 880-890 ft; early Miocene (Tertiary /).

USNM 648374. 

26. Rissoina (Rissoina) ailinana Ladd, n. sp. (p. 70).

Holotype, height 3.0 mm, X 10. E-l, Eniwetok, 1,925-1,955 ft; early Miocene (Tertiary e). USNM 648375.

27,28. Rissoina (Rissoina) lomaolana Ladd, n. sp. (p. 71).

Holotype, height 4.1 mm, X 8. K-1B, Eniwetok, 842-852 ft; late Miocene (Tertiary g). USNM 648376.

29. Rissoina (Rissoina) goikulensis Ladd, n. sp. (p. 71).

Holotype, height' 3.7 mm, X 8. Goikul Peninsula, Babelthuap, Palau (USGS 21304); late Miocene (Tertiary 

g). USNM 648377.

30. Rissoina (Rissoina) waluensis Ladd, n. sp. (p. 71).

Holotype, height 3.8 mm, X 8. Walu Bay, Viti Levu, Fiji (sta. 160); Suva Formation, early Miocene (Tertiary

/). USNM 648378. 

31,32. Rissoina (Rissoina) ekkanana Ladd, n. sp. (p. 71).

Holotype, height 3.2 mm, X 10. Mu-4, Eniwetok, 35 ft; Recent, USNM 648379. 

33. Rissoina (Rissoina) concinna A. Adams (p. 72).

Eniwetok specimen, height (incomplete) 6.4 mm, X 6. E-l, 970-980 ft; early Miocene (Tertiary /). USNM

648380. 

34,35. Rissoina (Rissoina) sp. A (p. 72).

Fiji specimen, height (incomplete) 4.8 mm, X 6. Walu Bay, Viti Levu (sta. 160); Suva Formation, early 

Miocene (Tertiary /). USNM 648381.

36,37. Rissoina (Rissolina) turricula Pease (p. 72).

Eniwetok specimen, height 2.7 mm, X 12. F-l, 20-45 ft; Recent. USNM 648407. 

38-40. Rissoina (Rissolina) marshallensis Ladd, n. sp. (p. 73).

38,39. Holotype, height 5.0 mm, X 6. K-1B, Eniwetok, 894-905 ft; early Miocene (Tertiary /). USNM

648408.

40. Paratype A, height (incomplete) 3.8 mm, X 6. E-l, Eniwetok, 850-860 ft; late Miocene (Tertiary g). 

USNM 648409.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 13

18

34

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19

12

20

36 37 

GASTROPODS: RISSOIDAE

24
PLATE 14

FIGURES 1-4. Rissoina (Rissolina) marshallensis Ladd, n. sp. (p. 73).

1. Paratype B, height 7.4 mm, X 6. K-1B, Eniwetok, 1,049-1,060 ft; early Miocene (Tertiary /). TJSNM 

648410.

2. Paratype C, height 4.2 mm, X 6. K-1B, Eniwetok, 842-852 ft; late Miocene (Tertiary gr). USNM 648411.

3. Paratype D, height 3.8 mm, X 6. K-1B, Eniwetok, 936-947 ft; early Miocene (Tertiary /). USNM 648412.

4. Paratype E, height 5.2 mm, X 6. 2B, Bikini, 1,020-1,100 ft; early Miocene (Tertiary /). USNM 648413. 

5-8. Rissoina (Rissolina) ephamilla Watson (p. 73).

5,6. Eniwetok specimen, height 3.0 mm, X 10. E-l, 850-860 ft; late Miocene (Tertiary gr). USNM 648414. 

7,8. Bikini specimen, height 2.9 mm, X 10. 2A, 447-453 ft; Pliocene (Tertiary h) or Pleistocene. USNM

648415.

11,12. Slender Eniwetok specimen, height 3.0 mm, X 10. E-l, Eniwetok, 530-540 ft; probably Pliocene (Tertiary h). USNM 648417. 

9,10. Rissoina (Rissolina) kickarayana Ladd, n. sp. (p. 74).

Holotype, height 4.1 mm, X 10. Goikul Peninsula, Babelthuap, Palau (USGS 21301); late Miocene (Tertiary

0). USNM 648416. 

13,14. Rissoina (Rissolina) herringi Ladd, n. sp. (p. 74).

Holotype, height 4.8 mm, X 8. F-l, Eniwetok, 710-720 ft; late Miocene (Tertiary g). USNM 648418.

15,16. Rissoina (Rissolina) harti Ladd, n. sp. (p. 74).

Holotype, height 3.2 mm, X 10. 2B, Bikini, 1,555-1,566 ft; early Miocene (Tertiary e). USNM 648419.

17,18. Rissoina (Rissolina) bourneae Ladd, n. sp. (p. 74).

Holotype, hegiht 3.2 mm, X 10. Suva Formation, Viti Levu, Fiji (sta. FB-20); early Miocene (Tertiary /).

USNM 648420. 

19,20. Rissoina (Rissolina) sp. B (p. 75).

Fiji specimen, height (incomplete) 3.9 mm, X 8. Viti Levu (sta. 165); probably Miocene. USNM 648421. 

21,22. Rissoina (Rissolina) plicata A. Adams (p. 74).

Eniwetok specimen, height (incomplete) 6.9 mm, X 6. F-l, 870-880 ft; early Miocene (Tertiary /). USNM

648422. 

23,24. Rissoina (Rissoina) ambiyua (Could) (p. 71).

Eniwetok speciment, height 6.4 mm, X 6. Rujiyoru Island, Eniwetok; Recent. USNM 648423.

25,26. Rissoina (Rissoina) ambigua parryensis Ladd, n. subsp. (p. 72).

Holotype, height (incomplete) 6.8 mm, X 6. E-l, Eniwetok, 620-630 ft; late Miocene (Tertiary g). USNM

648425. 

27. Barleeia (Barleeia) meiauhana Ladd, n. sp. (p. 75).

Holotype, height 0.9 mm, X 30. Goikul Peninsula, Babelthuap, Palau (USGS 21301); late Miocene (Tertiary

g). USNM 648426. 

28,29. Haplocochlias sp. A (p. 76).

Eniwetok specimen, height 1.2 mm, X 25. K-1B, 831-842 ft; late Miocene (Tertiary g). USNM 648427.

30,31. Leucorhynchia caledonica Crosse (p. 76).

Eniwetok specimen, height 1.4 mm, X 15. Eb-2, 21-21V2 ft; Recent. USNM 648428. 

32,33. Leucorhynchia crossei Tryon (p. 76).

Eniwetok specimen, height 1.2 mm, X 15. E-l, 35-40 ft; Recent. USNM 648429. 

34,35. Leucorhynchia? stephensoni Ladd, n. sp. (p. 76).

Holotype, height 1.0 mm, X 15. K-1B, Eniwetok, 1,249-1,259 ft; early Miocene (Tertiary e). USNM 648430.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 14

JJ1

GASTROPODS: RISSOIDAE AND ADEORBIDAE
PLATE 15

FIGURES 1,2. Leucorhynchia? lilli Ladd, n. sp. (p. 77).

Holotype, height 1.6 mm, X 15. Drill hole 1, Bikini, 40 ft; Recent. USNM 648432. 

3 5. Lophocochlias minutissimus (Pilsbry) (p. 77).

Eniwetok specimen, height 0.5 mm, X 30. E-l, 710-720 ft; late Miocene (Tertiary g). USNM 648433.

6 8. Lophocochlias paucicarinatus Ladd, n. sp. (p. 77).

Holotype, height 1.0 mm, X 30. E-l, Eniwetok, 2,040-2,050 ft; early Miocene (Tertiary e). USNM 648434.

9 11. Munditiella qualum (Hedley) (p. 77).

Eniwetok specimen, height 1.0 mm, X 15. F-l, 280-290 ft; probably Pleistocene. USNM 648435. 

12-14. Munditiella parryetntis Ladd, n. sp. (p. 78).

Holotype, height 1.1 mm, X 15. E-l, Eniwetok, 35-40 ft; Recent. USNM 648436. 

15 17. Teinostoma (Esmeralda) engebiense Ladd, n. sp. (p. 78).

Holotype, height 2.4 mm, X 15. En-4, Eniwetok, 1 ft; Recent. USNM 648437. 

18 20. Teinostoma (Esmeralda} marshallense Ladd, n. sp. (p. 78).

Holotype, height 1.1 mm, X 15. K-1B, Eniwetok, 863-873 ft; early Miocene (Tertiary /). USNM 648438.

21-23. Teinostoma (Esmeralda) sp. A (p. 78).

Fiji specimen, height 0.7 mm, X 20. Suva Formation, Viti Levu (sta. 160); early Miocene (Tertiary /). USNM 

648439.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 15

GASTROPODS: ADEORBIDAE
PLATE 16

FIGURES 1-3. Solariorbis tricarinata (Melvill and Standen) (p. 79).

Eniwetok specimen, height 1.6 mm, X 15. E-l, 990-1,000 ft; early Miocene (Tertiary /). USNM 648440.

4,5. tiolariorbis'? sp. (p. 79).

Fiji specimen, height 1.3 mm, X 15. Suva Formation, Viti Levu (sta. 160); early Miocene (Tertiaiy /). B. P.

Bishop Mus. Geol. 1236. 

6-8. Lydiphnis eniwetokense Ladd, n. sp. (p. 79).

Holotype, height 1.8 mm, X 15. K-1B, Eniwetok. 936-946 ft; early Miocene (Tertiary /). USNM 648441.

9-11. Cyclostremiscus emeryi Ladd, n. sp. (p. 80).

Holotype, height 0.4 mm, X 30. E-l, Eniwetok, 780-790 ft; late Miocene (Tertiaiy g). USNM 648444. 

12-14. Cyclostremiscus (Ponocyclus) novemcarinatus Melvill (p. 80).

Eniwetok specimen, height 1.0 mm, X 15. K-1B, 873-884 ft; early Miocene (Tertiary /). USNM 648442.

15-17. Cycloxtremiscus (Ponocyclux) cingulifcra (A.Adams) (p. 80).

Palau specimen, height 2.4 mm, X 10. Goikul Peninsula, Babelthuap (USGS 21304); late Miocene (Tertiary

0). USNM 648443. 

18 20. Cochliolepis diangalana Ladd, n. sp. (p. 81).

Holotype, height 0.8 mm, X 15. Goikul Peninsula, Babelthuap, Palau (USGS 21301); late Miocene (Tertiary

g). USNM 648445. 

21-23. Vitrinella sp. A (p. 81).

Bikini specimen, height 0.9 mm, X 30. 2B, 1,723-1,734 ft; early Miocene (Tertiaiy e). USNM 648446.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 PLATE 16

GASTROPODS: ADEORBIDAE