Eocene Brachiopods 

From Eua, Tonga

GEOLOGICAL SURVEY PROFESSIONAL PAPER 640-F
Eocene Brachiopods 

From Eua, Tonga

By G. ARTHUR COOPER

fPith a summary statement on TELEOST OTOLITHS

By JOHN E. FITCH

LATE EOCENE FOSSILS FROM EUA, TONGA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 640-F

Brachiopods representing six 

venera are recognized from 

tuffaceous limestone

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS G. B. MORTON, Secretary

GEOLOGICAL SURVEY 

W. A. Radlinski, Acting Director

Library of Congress catalog-card No. 72-176117

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

Washington, D.C. 20402 - Price 45 cents (paper cover)

Stock Number 2401-2022
LATE EOCENE FOSSILS FROM EUA, TONGA FOREWORD

One of the most widespread units of the Cenozoic 

section in the islands of the open Pacific is a series of 

limestones assigned to the upper Eocene (Tertiary 6). 

Such limestones, containing diagnostic larger Foraminifera, have been reported in many parts of an area 

spreading 4,000 miles across the tropical Pacific (fig. 1), 

from Palau and the Mariana Islands on the northwest 

through the Marshall Islands (Eniwetok) to Fiji and 

Tonga on the southeast (Whipple, in Hoffmeister, 1932, 

p. 79-86; Asano, 1939; Cole, 1950, 1957a, 1957b, 1960). 

In almost all the islands the limestones are dense and 

crystalline. Foraminifera and algae are abundant locally, but in most places fossils cannot be extracted and 

must therefore be studied in random thin sections. On 

the little island of Eua, Tonga, a locality was recently 

found where the Eocene limestone is tuffaceous, considerably weathered, and richly fossiliferous. Abundant 

fossils that represent a dozen organic groups were found. 

Such abundance and diversity signaled the find as a 

remarkable one that would add greatly to our knowledge of life in the western Pacific during the Eocene.

The island of Eua measures only 12 by 5 miles but 

it rises 1,000 feet above sea level. It occupies an interesting position tectonically, as its steep eastern side 

faces the Tonga Trench. In addition, Eua is the oldest 

island in the Tonga group that has a plutonic core 

(Guest, 1959) and a series of associated volcanic rocks, 

which are partly blanketed by thick limestones of late 

Eocene age. Younger volcanic rocks and sediments of 

late Tertiary age are also present (Hoffmeister, 1932).

This series of reports is concerned with one facies of 

the upper Eocene limestone. After the limestone series 

was deposited, Eua was uplifted periodically and a 

sequence of six terraces was cut in the limestones on 

the windward (eastern) side. Hoffmeister was the 

first to recognize the Eocene age of the main limestone 

of the terraces, three of which have veneers of Pliocene 

reef corals. He made a planetable map of the terraced 

eastern ridge and recorded the average altitudes of the 

terraces as 100, 200, 340, 400, 550, and 760 feet. The 

east-facing "rocky backbone" of Eua thus looks in 

profile like a giant staircase facing the Tonga Trench. 

The Eocene limestone may once have covered all of Eua

but is now largely limited to the eastern ridge (Hoffmeister, 1932; the Eocene Foraminifera were described by Whipple in this same report, p. 79-86).

The fossils described in this series of reports were 

obtained from an outcrop on he 400-foot tern.ce 

about a quarter of a mile north of Vaingana (fig. 2). 

At this locality, the limestone lies close to the underlying volcanic rock and is tuffaceous and partly 

weathered; almost everywhere else on Eua the limestone 

is pure, hard, and crystalline.

In 1943, Harold T. Stearns, then of the U.S. Geological Survey, also served as a consultant to the 

Armed Forces at Pacific bases and made a brief 

visit to Eua. He collected a sample that contained 

half a dozen fossil brachiopods from the 400-foot 

terrace on the eastern side of the island. Stearns recorded the locality as: "Tele-a-hiva at elevation 

of 400 feet about % mile north of army lookout tower, 

at the second stream north of Vaigana [sic]." The 

brachiopods were examined by G. A. Cooper of the 

U.S. National Museum. Some years later when I 

was studying other island fossils collected by Stearns, 

Cooper showed me the brachiopods and expressed 

a desire for additional specimens so that he could 

continue his study of their internal structures.

In 1966,1 learned that Yoshio Kondo of the Berrice 

P. Bishop Museum in Honolulu intended to visit Eua in 

connection with his studies of living Pacific island land 

snails (under National Science Foundation grant 

GB-3974). I sent Stearns' locality data and mar\ed 

copy of Hoffmeister's Eua map to Kondo, and I informed Stearns of the plan to collect additional 

material.

Late in August 1967, Kondo reached Eua and, aided 

by a Tongan guide, Tomiki, and an interpreter, Morose 

Vea, spent 2 days searching for the fossil locality. The 

lookout tower mentioned by Stearns no longer exists 

and Kondo found that Tele-a-hiva translates to "Nine 

Gulches." Traveling northward from "Vaigana" (Otu 

Vaingana) through heavy brush on exceedingly rugged 

karst topography for about 1,000 feet, he reached the 

first of the gulches. There he found a soft fossiliferous 

layer between two harder limestones and collected a

in
40-pound sample of the material. This gulch locality 

is probably not the exact spot visited by Stearns. The 

two collections have minor differences in nature of 

preservation, but they obviously came from the same 

formation.

In 1969 Wilfred Bryan of the Carnegie Institution 

of Washington collected additional material from the 

locality sampled by Kondo. Bryan's material was 

taken from soft calcareous tuffs 2-3 feet in thickness 

that dipped 30°-40° E. These calcareous tuffs were

FIGURE 1. Location of Tonga and other island groups in the southwest Pacific where upper Eocene limestone has been identified. Dashed line marks structural boundary of the Pacific Basin (andesite line). Islands shown include the surrounding reefs.

IV
directly underlain by several feet of harder fossiliferous material that, in turn, lay above agglomerate 

with truncated dikes. The horizon sampled was at an 

altitude of about 355 feet in a gully notched into the 

400-foot terrace.

The exact extent of the richly fossiliferous bed is 

not known. In 1926, when Hoffmeister made his

FIGURE 2. Map of Eua, Tonga, showing the location of the 

recently discovered fossil outcrop (x) and the main mass 

of Eocene limestone (patterned area) on the east side of 

the island, as mapped by Hoffmeister (1932).

map of the terraces, he did not come upon this facies, 

and in 1928 when I spent 2 weeks on Eua with Hoffmeister, reviewing his mapping, no exposures of this 

zone were seen although we visited Vaingana. Additional fieldwork in the area of the rugged "Nine 

Gulches" would be worthwhile.

William Melson of the Smithsonian Institution 

examined hand specimens and thin sections of the 

tuffaceous limestone and noted that the volcanic constituents are highly altered, making it difficult to 

determine their original nature. The rock is composed of 50 percent or more of volcanoclastic debris, 

much of which has been replaced by calcite. The 

predominant volcanic fragments are of porphyritic 

pumiceous glassy material; most of the phenocrysts 

are plagioclase, now largely replaced by calcite. The 

original groundmass of pumiceous glass is row 

devitrified and dark brown. Fragments of tuff are 

rare. There appears to be a large and varied assemblage of secondary minerals. The volcanic fragments 

are mainly porphyritic andesitic rocks, or possibly 

plagioclase-bearing dacites. The presence of abundant fossils suggests that the volcanic material has 

been reworked.

The soft tuffaceous limestones collected on Fua 

were treated with a wetting agent and penetrant in 

the laboratory. The material broke down easily, revealing a variety of fossil remains: Foraminifera, 

discoasters, corals, hydrozoans, brachiopods, bryozoans, annelids, crinoids, echinoids, ostracodes, 

barnacles, decapod crustaceans, mollusks, shark 

teeth, otoliths, and spores and other plant microfossils.

W. Storrs Cole has described the larger Foraminifera ; these fossils suggest to him a depth of deposition of about 200 feet, but other groups notably the 

smaller Foraminifera, the corals, brachiopods, bryozoans, mollusks, ostracodes, and barnacles point to 

a considerably greater depth of deposition.

Material representing a total of 17 organic groups 

was distributed to paleontologists for study and report. Seven of these collections were small or were 

made up of incomplete specimens leading only to 

summary reports, but the others, except for the 

larger Foraminifera, contained much new material. 

The brachiopod, bryozoan, ostracode, barnacle, rnd 

mollusk collections contained the first identifiable 

Eocene species from the islands of the open Pacific, 

an area extending 4,000 miles from Palau to Tonga.

HARRY S. LADD

CONTENTS

Page

Foreword ____________________-_ _ in

Abstract ________________________________ Fl

Introduction ______________________ _ _ _ 1

Systematics __________________ ___ _____ _ _ _ 2

Teleost otoliths, by John E. Fitch _______________________________ 7

References cited ________________ ______________________ 8

Index ________________________________________________ 9

ILLUSTRATIONS

[Plate follows index]

PLATE 1. Eocene brachiopods from Eua, Tonga.

Page

FIGURE 1. Map showing the location of Tonga and other island groups in the

southwest Pacific where upper Eocene limestone has been identified iv

2. Map of Eua, Tonga, showing the location of recently discovered fossil

outcrop and the main mass of Eocene limestone ______ ___ v

VII

LATE EOCENE FOSSILS FROM EUA, TONGA

EOCENE BRACHIOPODS FROM EUA, TONGA

BY G. ARTHUR COOPER

ABSTRACT

Six genera of brachiopods are recognized in Eocene strata 

from Eua in the Tonga Group. Three of the genera are uncertainly identified because of difficulties in obtaining interior 

details from the few specimens available. One genus, Aenigmathyris, proves to be new. All the genera, except the new one, 

have living descendants in the Pacific. Evidence as to the environment in which these brachiopods lived is inconclusive. 

Probably each had its own niche and they were swept together 

as a death assemblage.

INTRODUCTION

Any Eocene brachiopods are important, especially 

when they come from the Pacific from which few of 

them are known.

The details concerning the collecting of the specimens here described and a map of Eua showing the 

position of the locality are given in the "Foreword" 

(figs. 1, 2). Dating of the fossiliferous bed as late 

Eocene (Tertiary 6) was accomplished by identification of Foraminifera (Todd, 1970; Cole, 1970).

The importance of the brachiopods from Eua cannot be overemphasized because they indicate the 

presence of stocks hitherto thought to be largely 

restricted to areas outside the Pacific. Although 

Thecidellina is known in the Miocene of New Zealand 

(Thomson, 1927, p. 141), it has hitherto not been 

reported from Eocene rocks in the Pacific realm. The 

same is true of Argyrotheca which is very rare in 

the Pacific today and, except for a species found in 

the Gulf of California, Mexico (Hertlein and Grant, 

1944, p. 105), is represented only by minute specimens similar to those described from Eua.

The two terebratulinids suggest a Cretaceous 

rather than an Eocene age as indicated in the systematic discussion. A variety of small to minute 

terebratulinids appears in the Upper Cretaceous of

1 U.S. National Museum of Natural History, Smithsonian Institution, 

Washington B.C. 20560.

Europe and some are known from the Upper Cretaceous of Cuba.

Great interest is now attached to interpretation of 

ecological conditions which might have obtained 

during the life of any fossils newly described. 

Modern brachiopods are often deceptive in this respect because some species have an exceptionally 

wide tolerance of depth and temperature. Terebratulina septentrionalis (Couthuoy), for example, is 

common in shallow Atlantic waters ranging from 5 

to 100 fathoms, but this species has also been taken 

from 1,976 fathoms (Ball, 1920, p. 297-299). 

Another species, T. unguiculata (Carpenter) from 

Pacific waters, also has a fairly great depth range 

of 15 to 576 fathoms. Some species appear to be 

restricted to great deeps, such as Abyssothyris 

ivyvillei (Davidson) and Neorhynchia strebvli 

(Ball). Both species of Chlidonophora, which resemble the terebratulinid sp. indet. described below, 

are also confined to great deeps. Others, such as all 

species of Lingula and Glottidia, are confined to 

tidal waters or depths of a few (0-23) fathoms. 

Actually, so little is known of modern brachiopods 

and their ecological tolerances that generalizations 

concerning them are unwise, and deductions concerning the kinds of fossils referred to modern 

genera are difficult to make. Generally, sound deductions must be based on criteria other than generic 

identity and comparison with modern species.

Another factor makes ecological deductions bas^d 

on the assemblage from Eua quite hazardous. T" e 

brachiopods occur together in a death assemblage 

which may have brought together specimens frcm 

several varying ecological niches. For example the 

numerous specimens of Dallitkyris! are all jumbled 

together as single valves, many being broken and all 

being badly worn. Because no dorsal valve pr^-

Fl
F2 LATE EOCENE FOSSILS FROM EUA, TONGA

serves the cardinalia or even the hinge plates, certain identification of the genus is prevented. These 

shells, obviously not in their original environment, 

were probably swept into their present state by 

strong currents. The small specimens, such as 

Argyrotheca, have both valves intact, but their 

small size would prevent them from being torn apart 

by vigorous currents. Small Argyrotheca are known 

from Bikini (Cooper, 1954) where they come from 

50 fathoms and are associated with Thecidellina, 

which is usually found in fairly shallow water (less 

than 100 fathoms). All species of modern Dyscolia, 

the closest genus to Aenigmathyris, are deepwater 

dwellers (500 to 1,051 fathoms). Thus we have a 

hodge-podge of conflicting data based on brachiopods 

so that sound unequivocal decisions cannot be made. 

Cole (1970, p. B3) concluded from an analysis of 

the Foraminifera that his fossils occupied warm, 

shallow waters "about 200 feet in depth." Ladd 

(1970, p. C2) concluded that although it is "difficult 

to evaluate the molluscan evidence, ... it seems 

probable that the limestone represents offreef deposition at a depth of about 100 fathoms." Todd 

(1970, p. Al) concluded that the "great predominance of planktonic specimens in the Tonga sample, 

as much as 20 to 1, implies deposition at probably not 

less than 200 meters and in an area fairly distant 

from land." P. M. Kier (in Todd, 1970, p. A18) 

stated that the "echinoderm fragments indicate that 

the echinoderms lived in water deeper than 80 

meters." These divergent views based on different 

animal groups indicate the present youthfulness of 

paleoecology, yet each of these authors might be 

right. Conceivably, the Eua deposit is a result of 

slide, or shifting debris on a slope front, that has 

come to rest in deeper water whose bottom is replete 

with planktonic Foraminifera. Such a death assemblage could include echinoderms, brachiopods, and 

other invertebrates from many separate niches.

SYSTEMATICS

The systematics of the specimens described herein 

are not entirely satisfactory because of scarcity of 

material and because of difficulty of preparation of 

interior details. No trouble was experienced in developing the loop of Aenigmathyris but the two terebratulinids defied all effort at development of their 

cardinalia. The family identity is largely based on 

exterior details, especially those of the hinge region, 

which are very distinctive in the Cancellothyridae.

Aenigmathyris Cooper, n. gen.

About medium size, biconvex, the ventral valve

having the greater convexity; subpentagonal to ovate 

in outline; anterior commissure rectimarginate but 

with a tendency toward sulcation; beak short, truncated by a fairly large, strongly labiate, submesothyridid foramen; symphytium solid, visible. Surface 

marked by strong concentric lines of growth, crossed 

by very fine elevated radial lines especially on the 

flanks. Strongly punctate.

Ventral valve interior with stout te?th but no 

dental plates; pedicle collar narrow, elevated. Other 

details not known.

Dorsal valve with short but wide cardinal process, 

strong thick socket ridges and steep, flattened inner 

hinge plates. Descending lamellae and crural processes combined and attached directly to the hinge 

plate; loop narrowly compressed, loop length equal 

to about one-third the valve length; anterior narrowly rounded; transverse ribbon broad and narrowly folded medially; no anterolateral extensions. 

Other details not known.

Type species. Aenigmathyris stearr-si Cooper, 

n. sp.

Diagnosis. Ovate shells with dyscoliiform loop.

Comparisons. The narrow and elongated form of 

the loop with its narrowly rounded anter'or and lack 

of anterolateral extensions separates this genus from 

several of its homeomorphs such as Liothyrella, Gryphiis, Dallithyri-s, and Abyssothyris. Its nearest 

affinities seem to be with Dyscolia but a number of 

significant differences exist, not only in the interior 

but also in the exterior. The beak region of Aenigmathyris is very much like Dyscolia with a fairly large 

foramen truncating the beak which is strongly labiate. Dyscolia has a very characteristic ornament of 

interrupted, wavy radial lines. The shell of Aenigmathyris, especially on its flanks, has very fine, elevated 

radial lines but they are direct and not wavy and 

interrupted. Dyscolia commonly is thickened anteriorly, especially in old shells, and this feature 

appears in some specimens of Aenigmathyris. Thus 

the exterior of Aenigmathyris is similar to that of 

Dyscolia but differs in the character of the microornament.

The cardinalia of Dyscolia resemble those of 

Aenigmathyris but important differences are apparent. The socket ridges and hinge plates of the 

two genera are very close and the cardinal processes 

are essentially the same, but the loop of Aenigmathyris is laterally compressed whereas that of 

Dyscolia is usually broadly rounded and fairly thin. 

A feature of the loop shared by the two genera is 

the combination of the descending branches with the 

crural processes so that the latter, which are not very
EOCENE BEACHIOPODS F3

pointed in either genus, appear to come directly from 

the hinge plate. The part of the Dyscolia loop anterior to the crural processes is wide and rounded but 

that of Aenigmathyris is narrow and the ribbon 

forming the loop is broad. The median part of the 

loop of Dyscolia is generally not strongly folded but 

that of Aenigmathyris has a strong, narrow, and 

angular fold. Although the two loops are very different in shape, that of Aenigmathyris is clearly dyscoliiform and the new genus is placed in the Dyscoliidae Fischer and Oehlert 1891.

At present four other genera are placed in the 

family Dyscoliidae: Dyscolia Fischer and Oehlert, 

Moraviatura Sahni, Trigonithyris Muir-Wood (with 

a query), and Waisiuthyrina Beets. All have a fossil 

record but only Dyscolia is living today in the Atlantic and Indian Oceans. Trigonithyris, doubtfully 

placed in the family, is from the Jurassic. Moraviatura is from the Cretaceous and Waisiuthyrina is 

from the upper Oligocene. Dyscolia is represented by 

a species in the Pliocene of Sicily but Liothyris 

gravida (Suess) from Ototaran beds at Momoe-aToa, Chatham Islands, as represented by specimens 

in the national collection, is definitely a Dyscolia with 

all of the characteristic wavy ornament. This places 

the genus in the Miocene and in the Pacific where 

hitherto it has not been known. Aenigmathyris in the 

Eocene may thus be an early relative of Dyscolia and 

was quite at home in the Pacific where Dyscolia is 

now not known to live.

Aenigmathyris steamsi Cooper, n. sp.

Plate 1, figures 25-48

Approximately an inch (25 mm) in length, oval to 

subpentagonal in outline; longer than wide with the 

maximum width at about midvalve; sides strongly 

rounded; anterior margin broadly rounded to subtruncate. Apical angle ranging between 80° and 90°. 

Anterior margin rectimarginate to slightly sulcate. 

Beak erect to slightly incurved. Surface with numerous strong lines of growth and fine elevated radial 

lines concentrated on the flanks and anterior, 

stronger on the dorsal valve and poorly preserved 

or absent on median and umbonal parts of both 

valves. Punctae crowded.

Ventral valve evenly and moderately convex in 

lateral profile with the maximum convexity in the 

umbonal region; anterior profile broadly domed with 

short but steep slopes; beak region tapering; median 

region swollen; anterior slope short and rather steep.

Dorsal valve gently but unevenly convex in lateral, 

profile, the umbonal region the most convex, the

Dorsal 

valve 

length

16.2

24.0

19.5

19.2

Maximum 

width

15.4

23.4

20.0

20.2

Thickness

11.4

14.6

12.3

14.1

Apicc 

angh

87°

87°

87°

84°

median region somewhat flattened, and the anterior 

region moderately sloped; anterior profile broadly 

and very gently convex; beak inserted under symphytium; umbonal region slightly inflated; lateral 

and anterior slopes gentle.

Ventral valve interior poorly known but with a 

short elevated pedicle collar marginal to the inside 

of the foramen; muscles deeply inserted.

Dorsal valve interior with narrowly rounded and 

laterally compressed loop socket ridges thick; inner 

hinge plates reduced; crural processes blunt forming 

a part of the descending branch of the loop; anter'or 

part of loop with broad transverse band having 

a narrow, angular median fold. Other details of the 

interior not known.

Measurements in millimeters. 

USNM No. Length

549414b ________ 18.3

549415 _________ 26.8

550447a ________ 22.3

550447b ________ 22.1

Diagnosis. Subpentagonal Aenigmathyris w'th 

flanks and anterior marked by fine radii and w^'th 

stout laterally compressed loop.

Types. Holotype: USNM 550447a. Figured 

paratypes: USNM549414a, b; 549415; 550447b; 

549414d, e.

Discussion. This genus and species is based on 

seven complete specimens in varying stages of preservation and two dorsal valves that were prepared 

to show the loop. One of the dorsals preserved part 

of the pedicle valve which was also cleaned and revealed the short pedicle collar. Only the holotype is 

an undamaged specimen. All the others have the 

valves displaced to a varying degree and one specimen has a fractured dorsal valve. The smallest specimen measures only 13.5 mm but is badly crushed. 

Although younger than all the others, it seems to be 

an adult.

It is hazardous to postulate the conditions unc^r 

which these specimens lived. The matrix filling them 

and in which they occur is a nearly white marl w:th 

small brown pellets. Whether they lived where they 

were entombed is an unanswered question. The 

foramen suggests a strong, stout, probably short 

pedicle which attached the bearer to its fellows and 

other shells.

The species is named for Dr. Harold T. Stearns 

who discovered the locality and collected the first 

specimens.
F4 LATE EOCENE FOSSILS FROM EUA, TONGA

Dallithyris? sp.

Plate 1, figures 23 and 24

About medium size for the genus, elongate trigonal 

in outline with straight sides and broadly rounded 

anterior margin; greatest width in the anterior third; 

anterior commissure rectimarginate to faintly uniplicate. Beak narrow, truncated by a small narrowly 

labiate foramen which is permesothyridid. Surface 

appearing smooth but marked by concentric lines of 

growth and a micro-ornament of very fine, crowded 

radial lines visible only in oblique light and seen 

chiefly on the flanks.

Pedicle valve moderately convex in lateral profile 

with the strongest convexity in the umbonal region 

and the anterior flattened; anterior profile narrowly 

domed and with long steep slopes; umbonal and 

median regions narrowly swollen; anterior slope 

long, moderately steep. Ventral muscle field elongate, 

anteriorly truncated.

Dorsal valve shallower than the ventral valve, 

moderately convex in lateral profile but broadly and 

moderately domed in anterior profile. Median region 

swollen.

Measurements in millimeters. 

Dorsal

valve Maximum Apical 

USNM No. Length length width Thickness angle

550446a __________ 20.2 ? 15.8 10.2 56°

550446b __________ 19.5 ? 16.7 7.6 60°

550446c __________ 18.7 ? 15.5 9.6 70°

Diagnosis. Dallithyris strongly tapered posteriorly and with triangular outline.

Figured specimens. USNM 550446a, b.

Discussion. The above description is based on a 

few good valves out of a large number of fragmentary specimens. The collection consists of numerous 

specimens but all the dorsal valves are badly broken 

and only a half dozen of the ventral valves are in 

good condition. The specimens are nearly all discolored, the discoloration ranging from rich chocolate 

to black. The matrix is a cream-colored marl with 

brown pellets. Not a single specimen was collected 

with both valves in place; consequently the loop is 

unknown. Furthermore, the few dorsal valves that 

show any of their cardinalia have only damaged 

hinge plates with no trace of a loop. The hinge plates 

are shallow and concave and no trace of a cardinal 

process was seen.

The jumbled character of the specimens in matrix, 

the separation of the dorsal from the ventral valves, 

and the presence of very few dorsal valves suggest 

reworked, dead specimens piled together from some

other environment than that in which they were 

ultimately entombed.

The exterior of this species suggests the form of 

Dallina or Gryphus sphenoidea (Philippi) of the 

Mediterranean Tertiary and Dallithyris murrayi 

Muir-Wood of the Indian Ocean. The anterior folding 

is not in accordance with Dallina but th? unequally 

convex and shallow dorsal valves suggest the other 

two species.

Terebratulina? sp. 

Plate 1, figures 20-22

Very small, trigonal in outline with the greatest 

width anterior to the middle; sides and anterior well 

rounded; hinge narrower than midvalve width and 

with small ears; delthyrium large and open; beak 

narrowly rounded; valves subequally convex. Surface marked by closely crowded, strongly beaded 

costellae. Interior not known.

Measurements in millimeters.-

USNM No. Length

550443a _____________ 2.9 

550443b _____________ 2.1

Dorsal

valve 

length

2.2 

1.8

Width Thickness

2.3

1.9

1.2 

0.9

Discussion. These small specimens possess the 

characters of an immature Terebratulina: open foramen with no deltidial plates and stror<?ly beaded 

costae. These features are also the extenal characteristics of Rugia Steinich (1963) from Upper Cretaceous sedimentary rocks in Denmark. The collection contains only four specimens, one of which is a 

fragmentary ventral valve with interior details. But 

this does not help with generic definition. Even if 

the interior of the dorsal valve were l~nown it is 

doubtful whether it would be possible to distinguish 

Rugia from immature Terebratulina in which the 

crural processes had not yet fused. Consequently it 

seems best to refer the Eua specimens tc Terebratulina which has a long geological history and occurs in 

all parts of the world. These little specimens do not 

tell an ecological story with our present knowledge 

of the genus. Terebratulina is usually a shallowwater genus. The deepest record given by Dall (1920, 

p. 299) who lists most of the Holocene species, is for 

T. septentrionalis (Couthouy) from 1,976 fathoms 

off Martha's Vineyard, Mass. Most of the records are 

above 500 fathoms and many are les" than 100 

fathoms.

These little shells are almost identical to small but 

fairly wide-hinged terebratulinids in the Eocene of 

Cuba which also are suggestive of Rugia. I have been
EOCENE BRACHIOPODS F5

unable to expose the loops of any of these tiny 

brachiopods.

Terebratulinid, gen. and sp. indst.

Plate 1, figures 14-19

Minute, pentagonal in outline with the sides nearly 

straight and the anterior margin broadly rounded; 

posterolateral margins converging to form an angle 

of about 100°. Valves unequal in depth, the ventral 

valve being much deeper than the dorsal one; hinge 

straight, wide, nearly equal to the maximum shell 

width which is near midvalve; anterior commissure 

rectimarginate. Beak incurved, foramen large, triangular. Surface marked by costellae, strongest in 

the anteromedian region but fading out on the posterolateral extremities. Costellae about six on a side 

with a median one the strongest of all.

Ventral valve strongly convex in lateral profile; 

strongly domed and with long steeply sloping sides 

in anterior profile; umbonal region narrowly swollen, 

the swelling continuing medially to the anterior margin. Dorsal valve flatly convex in lateral profile but 

broadly and very gently convex in anterior profile; 

fold marked by the single costa stronger than the 

others which opposes a narrow groove on the ventral 

valve.

Interior not known except for an apical plate in 

the pedicle valve against which the pedicle rested.

Measurements in millimeters. 

USNM No. Length

550445a ____________ 1.55 

550445b _____________ 1.7

Dorsal 

valve, 

length

1.2 

1.4

Width Thickness

1.4 0.75

1.55 0.9

Figured specimens. USNM 550445a, b.

Discussion. These little specimens have the external characters of several genera and, in absence of the interior details, it is impossible to say 

to which one they belong. They suggest Eucalathis 

but that genus is usually more triangular and has a 

narrower hinge. Chlidonophora has a wide hinge like 

the Eua specimens but has a less incurved beak, 

smaller foramen, and a more finely costellate shell. 

Furthermore, the dorsal valve is somewhat keeled 

medially and has a swollen umbonal region. Orthothyris of the Cuban Cretaceous is similarly shaped 

and wide hinged, but it is costate rather than costellate. Only by discovery of the loop will it be possible 

to assign this interesting minute brachiopod to its 

proper genus. Several specimens were destroyed in 

an effort to determine the loop. The collection is too 

limited in numbers to sacrifice more specimens.

Argyrotheca anomala Cooper, n. sp.

Plate 1, figures 7-13

Minute, longer than wide and having a subtrigonal 

or subpentagonal outline; widest anteriorly; sides 

slightly rounded to straight; anterior margin gently 

rounded to moderately indented medially. Lateral 

profile lenticular; valves uneven in depth, the pedicle 

valve having the greater depth. Beak elongated; foramen large, triangular, open, margined by rudimentary deltidial plates. Surface smooth.

Ventral valve gently convex in lateral profile, 

broadly and flatly domed in anterior profile; f anks 

slightly swollen but median and anterior regions 

flattened to form a gentle sulcus of varying depth in 

different specimens.

Dorsal valve in lateral profile varying from very 

gently convex to slightly concave; convexity st~ongest at the umbo; interior profile forming a broad 

dome, gently concave medially but with convex sides; 

umbonal region swollen, the swelling continuing to 

midvalve where a shallow but broad sulcus is formed 

to indent the anterior margin. Flanks moderately 

convex. Lateral slopes fairly steep.

Ventral interior with a low median ridge, all other 

details obscure. Dorsal valve interior with strong, 

elevated socket ridges; median septum originating 

slightly posterior to midvalve, forming a crest at 

about two-thirds of the valve length and with r. concave anterior slope which is crudely serrate. No trace 

of a loop.

Measurements in millimeters. 

USNM No. Length

550442a _____________ 2.2 

550442f _____________ 2.0

Dorsal

valve Maximum 

length width Thickness

1.8 

1.5

2.0 

1.8

0.8 

1.0

Diagnosis. Elongate, smooth Argyrotheca.

Types. Holotype: USNM 550442a. Figured paratypes: USNM 550442b-e. Unfigured paratype: 

USNM 550442f.

Comparison and discussion. Argyrotheca is a 

very prolific genus with a range into the Cretaceous. 

Nearly all the known species of Argyrotheca ar^ plicated but a few such as A. akymatophora Stenzel 

and A. power si Gardner are smooth or nearT y so. 

I know of only one species, A. mayi (Blochmann), 

having the characters of the Eua species. Most 

specimens of Argyrotheca are wider than the.v are 

long or have length and width nearly equal, but none 

are terebratuliform as is A. anomala. The small size 

and nudity of A. anomala might suggest that the
F6 LATE EOCENE FOSSILS FROM EUA, TONGA

species is an immature form, but all of the many 

specimens are nearly of the same size; they do not 

show enlarged punctae as is common in all immature 

punctate terebratulids or terebratellids and the shells 

and septa are thick, not delicate as in immature 

specimens.

Argyrotheca is not well known in the Pacific but 

three species have been described: A. mayi (Blochmann) and A. australis (Blochmann) are from the 

southern hemisphere and A. loivei Hertlein and Grant 

is from the Gulf of California. A. loivei is a large, wide, 

plicated form and does not compare with A. anomala. 

A. australis is also a ribbed form and not comparable 

with the Eua species. A. mayi is an elongated and 

smooth species strongly suggestive of A. anomala. 

It is 2.5 mm long, 2 mm wide, and 1.0 mm thick. Its 

measurements are thus almost exactly like those 

from Eua but Blochmann's species is subrectangular 

longitudinally, its foramen much more strongly indented anteriorly than the Eua species. Although 

the exterior of the two species is similar, the interiors 

are entirely unalike. The septum of the dorsal valve of 

A. mayi is less well developed than that of A. anomala but that of the ventral valve is more strongly 

developed. It is remarkable that a species living today should be externally so like the Eocene species 

of Eua.

Cooper (1954) described a small Argyrotheca 

from the Holocene at Bikini but this is differently 

shaped than the Eua species and A. mayi. It is transversely rectangular in outline rather than elongate 

and has incipient costae.

The Eocene of Cuba and other Tertiary deposits 

in the Caribbean region are rich in species of Argyrotheca. This is true also of the Tertiary of the Gulf 

States of the United States. In the Caribbean region 

all described species are moderately large for the 

genus and are costate. They certainly represent a 

more advanced state of development than those of 

Eua. The few species known from the Cretaceous 

are also costate and more advanced than those of 

Eua. The Pacific, like the Indian Ocean, so far as 

present knowledge goes, is not prolific in this genus. 

The same may be said of the Pacific Tertiary as the 

only Argyrothecas reported are from New Zealand 

and Australia. None has been reported from Japan. 

The restriction of the genus at present to the tropical 

regions on either side of the equator, north to the 

Mediterranean and south to Australia, suggests 

warmer waters as a requirement for their well-being.

Thecidellina sp.

Plate 1, figures 1-6

Small, nearly circular in outline, but with the 

posterior margin made irregular by the cicatrix of 

attachment. Hinge width about half of the valve 

width. Ventral valve larger than the dorsal valve and 

forming a flattened triangle in lateral profile; attachment cicatrix fairly large, occupying on^-third to 

two-thirds of the valve length. Dorsal valve shallow 

and gently convex in lateral profile and with a short 

interarea. Maximum convexity at about midvalve.

Ventral valve interior with stout teetl; pseudodeltidium short, leaving a large gap for reception of 

the cardinal process; hemispondylium not visible. 

Dorsal valve interior with long squarish cardinal 

process, hollow internally and with a small median 

septum; rim narrow and strongly pustulous; median 

ridge slender not widening strongly anteriorly.

Measurements in millimeters. 

USNM No. Length

550444a _____________ 1.8

550444b _____________ 2.5

550444c _____________ 1.9

Brachial 

valve 

length

1.6

2.1

Width Thickness

1.8 1.0

1.9

Diagnosis. Very small, nearly circular Thecidellina with slender median ridge in dorsal valve which 

has a narrow pustulose marginal rim.

Comparison and discussion. The proportions and 

interior development of the four specimens in the 

collection suggest that they are adults of a very 

small species. The interior of the dorsal valve has all 

the features of an adult in the well-developed median 

ridge and the strongly pustulose marginal rim. Compared with small specimens of T. congregata Cooper 

from Bikini Atoll, the Eua specimens are much 

rounder in dorsal aspect and are much more convex. 

No young of T. maxilla (Hedley) of comparable size 

to the Eua specimens are available for comparison.

This is the earliest representative of Thecidellina 

in the Pacific. It is known in the Miocene of New 

Zealand (T. hedleyi Thomson, 1915, p. 463) and 

from sediments of the same age from drill holes in 

Bikini and Eniwetok. Thecidellina is known from 

the Eocene of the United States (T. cooperi Toulmin, 

1940, p. 228) and from specimens not yet described. 

It is also known from undescribed specimens from 

the Eocene of Cuba. Thus the genus has an ancient 

lineage but its roots in the Cretaceous are still to be 

found.
EOCENE BRACHIOPODS F7

Thecidellina is fairly common in present seas 

around the West Indies and in the Pacific around 

Bikini, Fiji, and Guam. In the Indian Ocean it was 

found at Christmas Island. Throughout this vast 

range its deepest record is 150 fathoms from the 

Caribbean. The deepest record in the Pacific is from 

Bikini Atoll where it was taken from 133 fathoms 

although the specimens were ventral valves on coral 

and may not have lived at this depth.

TELEOST OTOLITHS

By John E. Fitch 2

Fifty-two recrystallized otoliths and otolith fragments were available for study. These bore the collection number USGS 24745 and had been gleaned from 

material collected in 1969 by Wilfjred Bryan of the 

Geophysical Laboratory of the Carnegie Institution 

of Washington. The locality of collection on Eua, 

Tonga, was the same as that sampled in 1967 by 

Yoshio Kondo of the Bernice P. Bishop Museum 

(Harry S. Ladd, written commun., 1970).

For determining family relationships, the most 

important single feature of any teleost sagitta is 

the sulcus (that is, an imprint or channeled groove 

on the inner face of the otolith), but details of the 

sulcus had been obliterated, presumably during recrystallization, on all but one of these 52 otoliths. 

In spite of this, sufficient characters were observable 

on 26 of the otoliths to determine that these represented 10 kinds of fish, but only six of these "species" 

could be placed in "families" with any feeling of 

certainty: two in flatfish, one in Macrouridae, and 

three in Myctophidae.

Flatfishes, of which there are six families, generally are associated with a marine environment and 

flat bottom topography. Various genera and species 

range from the shallow subtidal region into depths 

exceeding 1,080 fathoms. A few species are known 

from polar seas, but all families are represented in 

tropical waters where flatfishes have attained their 

greatest generic diversity. No fossil flatfishes are 

known from the Cretaceous, but several modern 

families were well established by middle Eocene. 

Weiler (1968), on the basis of otoliths, lists nine 

Eocene species in three families, and skeletal remains 

of the same age are known from several European 

localities. None of the flatfish otoliths from Eua 

could be assigned to a definite family but since the

2 Marine biologist, California State Fisheries Laboratory, Long Beach, 

California 90802.

sulcus of one did not appear to reach the otolith 

margin, it probably was from a bothid (Bothidae). 

In the family Cynoglossidae, the sulcus also fails to 

reach the otolith margin, but the angular outline of 

the Eua otolith precludes its placement with the 

tonguefishes. Although the other two flatfish otcliths 

represented a different species, they were impossible 

to identify except as flatfish.

Macrourids are the most characteristic and abundant of all benthic deep-sea fishes, being found in all 

seas and at all depths with the conspicuous exception 

of the Polar Basin (Grey, 1956). They generally inhabit muddy bottom areas at depths exceeding; 108 

fathoms, but on rare occasions macrourids are captured in shallower water. The family enjoys an extremely rich fossil record with otoliths being found 

as early as Paleocene in British deposits (Weiler, 

1968). The five macrourid otoliths from Eua were 

probably from a single species, but their exceedingly 

poor condition would not permit speculation as to 

generic affiliation.

Lanternfishes (Myctophidae) are typical nesopelagics which inhabit scattering layers throughout 

the world oceans. Most myctophids undertake diurnal migrations, moving upward at night, sometimes to the ocean's surface and returning to the 

depths during daylight hours. Most California species 

for which data are available have a center of diurnal 

distribution between 246 and 383 fathoms beneath 

the surface (Paxton, 1967). Temperature and light 

appear to be the most important ecologic determinants of vertical distribution, and there is no reason 

to suspect that conditions are different elsewhere in 

the world. Although solitary fish scales fourd in 

Cretaceous chalks of Alabama are thought to be from 

lanternfish, is no positive record of the family prior 

to the Eocene (Fitch, 1969). Myctophid remains, 

particularly otoliths, are extremely abundart in 

fossil deposits throughout the world (Weiler, 1968; 

Fitch, 1969, and unpub. data). The 13 myctophid 

otoliths from Eua represent three distinct species, 

with 11 being from a single species.

On the basis of knowledge of the preferred environments of the present-day relatives of these few 

faunal components, depth of deposition would almost 

certainly have exceeded 182 fathoms. Bottom sediments dredged from depths of 76 fathoms ir the 

Indian Ocean contained an admixture of otcliths 

from shallow- and moderate-depth species, whereas 

otoliths in sediments from depths exceeding 383
F8 LATE EOCENE FOSSILS FROM EUA, TONGA

fathoms in the Gulf of California showed a greater 

correlation with the Eua otoliths. Otoliths of myctophids frequently are found in sediments desposited at 

much shallower depths, but in these instances they 

seldom contribute more than a very minor portion 

to the total otolith yield, and rarely is there more 

than one species of myctophid. With additional sampling recognizable otoliths of congrids, bregmacerotids, berycids, and brotulids might be discovered in 

the tuffaceous limestone on Eua, which would 

strengthen the hypothesis of deposition at relatively 

great depth.

My work with fossil otoliths has been made possible by research grants (GB-1244 and GB-6490) 

from the National Science Foundation under the 

sponsorship of the Los Angeles County Museum of 

Natural History Foundation.

REFERENCES CITED

Asano, Kiyoshi, 1939, Limestones of the South Sea Islands 

under the Japanese Mandate: Yabe Jubilee Pub., v. 1, 

p. 537-550.

Cole, W. S., 1950, Larger Foraminifera from the Palau 

Islands: U.S. Geol. Survey Prof. Paper 221-B, p. 21-31.

 1957a, Larger Foraminifera, in Part 3, Paleontology, 

of Geology of Saipan, Mariana Islands: U.S. Geol. Survey 

Prof. Paper 280-1, p. 321-360.

 1957b, Larger Foraminifera from Eniwetok Atoll drill 

holes: U.S. Geol. Survey Prof. Paper 260-V, p. 743-784 

[1959].

 1960, Upper Eocene and Oligocene larger Foraminifera 

from Vitu Levu, Fiji: U.S. Geol. Survey Prof. Paper 

374-A, 7 p. [1961].

1970, Larger Foraminifera of late Eocene age from

Eua, Tonga: U.S. Geol. Survey Prof. Paper 640-B, 17 

p., 5 pis., 2 figs.

Cooper, G. A., 1954, Recent brachiopods, in Part 2, Oceanography (biologic), of Bikini and nearby atolls, Marshall 

Islands: U.S. Geol. Survey Prof. Paper 260-G, p. 315-318, 

pis. 80, 81.

Dall, W. H., 1920, Annotated list of recent Brachicpoda in the 

collection of the United States National Museum, with 

descriptions of thirty-three new forms: U.S. Natl. Mus. 

Proc., v. 57, p. 261-377.

Fitch, John E., 1969, Fossil lanternfish otoliths of California, 

with notes on fossil Myctophidae of North America: Los 

Angeles County Mus. Contrib. in Sci., no. 173, p. 1-20.

Grey, Marion, 1956, The distribution of fishes found below a 

depth of 2,000 meters: Fieldiana Zoology, v. 36, no. 2, 

p. 73-337.

Guest, N. J., 1959, Geological mapping, Tonga: Fiji Geol. Survey Dept., Ann. Rept. for 1958, Council Paper 17, p. 3.

Hertlein, L. G., and Grant, U. S., IV, 1944, The Cenozoic Brachiopoda of western North America: California Univ. 

Pub. Math and Phys. Sci., v. 3, p. 1-236, 21 pis., 34 figs.

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

Bishop Mus. Bull. 96, 93 p.

Ladd, H. S., 1970, Eocene mollusks from Eua, Tonga: U.S. 

Geol. Survey Prof. Paper 640-C, 12 p., 5 pis.

Paxton, J. R., 1967, A distributional analysis for the lanternfishes (Family Myctophidae) of the San Pedro Basin, 

California: Copeia, 1967, no. 2, p. 422-440.

Steinich, Gerhard, 1963, Drei neue Brachiopodengattungen der 

Subfamilie Cancellothyrinae Thomson: Geologic, Jahrg. 

12, H. 6, p. 732-740, 8 figs.

Thomson, J. A., 1915, A new genus and species of the Thecidiinae: Geol. Mag., decade 6, v. 2, no. 10, p. 461-464.

 1927, Brachiopod morphology and genera (Recent and 

Tertiary) : New Zealand Board Sci. and Art Manual, 

no. 7, 338 p., 2 pis., 103 figs.

Todd, Ruth, 1970, Smaller Foraminifera of late Eocene age 

from Eua, Tonga: U.S. Geol. Survey Prof. Paper 640-A, 

23 p., 8 pis., 4 figs.

Toulmin, L. D., 1940, Eocene brachiopods from the Salt Mountain limestone of Alabama: Jour. Paleontology, v. 14, 

no. 3, p. 227-233, pi. 28.

Weiler, Wilhelm, 1968, Otolithi Piscium (Neubearbeitung), 

Part 117 of Westphal, F., ed., Fossilium C^.talogus. I. 

Animalia: The Hague, W. Junk N.V., 196 p.
INDEX

[Italic numbers indicate major references and descriptions]

Page

Abyssothyris _ __ ___________ F2 

wyvillei ______________ __ 1

Aenigmathyris ________________ 2, 3

stearnsi -_-__ ____-__ 2, 3; pi. 1 

akymatophora, Argyrotheca _____________ 5

Annelids _ V 

anomala, Argyrotheca - ______ _5, 6; pi. L

Argyrotheca _ _1, 2, 5, 6 

akymatophora ___________________ 5

anomala ___ _ _ ___- 5, 6; pi. 1 

australis _____________________ _ 6

lowei _ _ _ _ _ _. 6 

mayi ______________________________ 5, 6

poiversi - __ _ - _ - 5 

australis, Argyrotheca _______ - - 6

Barnacles _ _ V 

Bibliography ____ _ _ _ _ _ 1 

Brachiopods III, V 

Bryozoans __ _ _ -- V

Chlidonophora __ - 

congregata, Thecidellina 

cooperi, Thecidettina 

Corals 

Crinoids 

1, 5 

6 

6 

V 

V

Dallina _____________________________ 4

Dallithyris __________ _____ __1, 2, 4

murrayi _-__ __ - 4

sp 4; pl. 1

Decapod crustaceans V

Page

Discoasters ____ ____ _ V

Dyscolia _______ 2, 3

Dyscoliidae _____________________________ 3

Echinoids _ V

Eua, geology of __________ ___ III

relation to Tonga Trench _ _ III

Eucalathis - _ 5

Foraminifera __ _ V

Foreword, by H. S. Ladd III

Glottidia _ 

gravida, Liothyris 

Gryphus _________

sphenoidea _-

hedleyi, Thecidellina 

Hydrozoans -_______

Ladd, H. S., Foreword ___________ III

Lingula _ _ 1

Liothyrella - - ___ 2

Liothyris gravida ___ _ 3

lowei, Argyrotheca ______ 6

'maxilla, Thecidellina _________ _ 6

mayi, Argyrotheca -- _ 5, 6

Mollusks . 

Moraviatura -___- 

murrayi, Dallithyris .

Neorhynchia strebeli

vowersi. Aravrotheca - ______

Page

. ____ _ 5

.__ ____ V

v

v

. ____ _ 5

Rugia

septentrionalis, Terebratulina __ _ _ 1, 4

Shark teeth ______ _ ____ V

sphenoidea, Gryphus -_____ _ _ _ 4

.Stearns, H. T., quoted _ _ _ III

stearnsi, Aenigmathyris __ _ 2

strebeli, Neorhynchia ___________________ 1

Terebratulina __ 4 

septentrionalis ______ 1, 4

unguiculata 1 

sp 4; pi. 1

Terebratulinid ________________________5; pl. 1

Thecidellina - 1, 2, 6

congregata _____ _ _ __ . 6

cooperi 6 

hedleyi ____________________________ 6

maxilla ___________-______ 6

sp _________ _ 6; pl. 1 

Trigonithyris 3

unguiculata, Terebratulina _____________ 1

Vaingana ___________ _ III

Waisiuthyrina _______

wyvillei, Abyssothyris

F9

PLATE 1

Contact photographs of the plate in this report are available, at cost, from 

U.S. Geological Survey Library, Federal Center, Denver, Colorado 80225.
PLATE 1

FIGURE 1-6. Thecidellina sp. (p. F6).

1-3. Ventral, side, and dorsal views of a complete specimen, X 10,

figured specimen USNM 550444a. 

4, 5. Exterior and interior of the dorsal valve, X 10, showing the strong

median ridge, figured specimen USNM 550444b. 

6. Interior of the ventral valve showing teeth and flat deltidial region,

X 10, figured specimen USNM 550444c. 

7-13. Argyrotheca anomala, Cooper, n. sp. (p. F5).

7-9. Dorsal, ventral, and side views of a complete specimen, X 10,

holotype USNM 550442a.

10. Dorsal view of a young individual with strongly emarginate anterior, 

X 10, paratype USNM 550442b.

11. Interior of the dorsal valve showing the strong median septum so 

characteristic of the genus, X 10, paratype USNM 550442c.

12. Interior of the ventral valve, X 10, showing the median ridge, 

paratype USNM 550442d.

13. Dorsal view of an adult showing open foramen, paratype USNM

550442e. 

14-19. Terebratulinid, gen. and sp. indet. (p. F5).

14-16. Anterior, side, and dorsal views, X 10, showing ornament, figured 

specimen USNM 550445a.

17-19. Side, anterior, and dorsal views, X 10, of another, larger specimen, figured specimen USNM 550445b. 

20-22. Terebratulina? sp. (p. F4).

Side, ventral, and dorsal views of a strongly beaded specimen, X 10,

figured specimen USNM 550443a. 

23, 24. Dallithyris? sp. (p. F4).

Dorsal and ventral valves, X 1, showing trigonal form of ventral valve,

figured specimens USNM 550446a, b. 

25-48. Aenigmathyris stearnsi Cooper, n. sp. (p. F3).

25-29. Dorsal, posterior, ventral, anterior, and side views of a young 

individual, X 1, paratype USNM 549414b.

30-33. Posterior, side, dorsal, and anterior views of an undistorted specimen, X 1, holotype USNM 550447a.

34-37. Ventral, dorsal, side, and anterior views of a larger but damaged 

specimen, X 1, paratype USNM 5494l4a.

38-41. Anterior, ventral, side, and dorsal views of another large but 

imperfect paratype, X 1, USNM 549415.

42-45. Anterior, side, dorsal, and posterior views of another paratype, 

X 1, USNM 550447b.

46. Dorsal view of preceding specimen, X 2, showing traces of radial 

ornament.

47. 48. Interior of two dorsal valves, X 3, showing the loop with rounded 

anterolateral extremities, paratypes USNM 549414e, d.
GEOLOGICAL SURVEY PROFESSIONAL PAP» 640-F PLATE 1

EOCENE BRACHIOPODS FROM EUA, TONGA