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UNITED STATES DEPARTMENT OF THE INTERIOR

SPECIES AND GENERA OF 

TERTIARY NOETINAE

GEOLOGICAL SURVEY PROFESSIONAL PAPER 189—A
UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Professional Paper 189—A

SPECIES AND GENERA OF 

TERTIARY NOETINAE

BY

F. STEARNS MAcNEIL

Shorter contributions to general geology, 1937

(Pages 1-50)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1938

For sale by the Superintendent of Documents, Washington, D. C. ------- Price 20 cents
CONTENTS

Page

Introduction _____________-__-__-_-__--__________________..__________--_--____----_-_---___--_--__--______--__-_ 1

Acknowledgments. ______________________________________________________________________________________________ 1

Classification _ ________________________________________________________________________________________________ 1

Geographic and stratigraphic occurrence of the Noetinae___________________________________________________________ 2

Atlantic group.________-____-_____-_-_________________________-_-__..________----_-_--_-_-___---______--_-__ 2

Pacific group,______________________________________________________________________________________________ 4

Characters in which the Atlantic and Pacific groups differ.______________-___-______--___-_____----______-_____-____ 5

Differences in sculpture___________________________________________________________________________________ 5

The ligament_______---_____--__-_---_______________________--____--____-___-_-----_-_---_-_-___-__----_- 7

Crenulations of the inner margin.___________________________________________________________________________ 8

Descriptions of species..________________________________________________________________________________________ 8

Atlantic group______-____________-__.____-_____-__________-_-----__-_____--__----__---_-____-_______----_- 8

Pacific group,_____________________________________________________________________________________________ 25

Index____ ____-_________---_-__-_______-___-______-__________________-______--_-_-----_-_-----_---__-_-___ 49

ILLUSTRATIONS

Page 

PLATE 1. Tertiary and Recent species of Scapularca, Sheldonella, Paranoetia, and £Joniia_______________________________ 42

2. Miocene and Pliocene species of Eontia _________________________________________________________________ 43

3. Pliocene, Pleistocene, and Recent species of Eontia, ___-_______________________________________„__________ 44

4. Eocene species of Protonoetia, Noetiopsis, Arginopsis, Arginella, and Noetia- _________________________________ 45

5. Miocene species of Noetia. ___________________________________________________________________________ 46

6. Miocene, Pliocene, Pleistocene, and Recent species of Noetia______________________________________________ 47

FIGURE 1. Diagrams showing relation of adult sculpture to nealogic sculpture-________________________________________ 6

2. Diagram showing supposed relationships of North American species of Eontia _______________________________ 25

ii
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

SPECIES AND GENERA OF TERTIARY NOETINAE

By F. STEARNS MACNEIL

INTRODUCTION

The purpose of this paper is to treat systematically 

all the species and genera that are referable to the subfamily Noetinae. A redefinition of the subfamily based 

on the critical morphology and developmental trends 

of the type genus includes some forms not previously 

regarded as Noetinae and excludes some genera referred 

to this subfamily by previous authors. .Emended 

descriptions are provided for described species and 

genera, for the purpose of reducing the expressions of 

many writers to a common terminology, and some new 

species and genera are described. In addition the 

relationships and migration of the genera involved 

during Tertiary time are discussed.

The synonymy and references are probably not complete, although it is hoped that all the important references are given and that the nomenclature is reasonably 

correct.

ACKNOWLEDGMENTS

Appreciation is hereby expressed to the many persons 

whose generous aid made the completion of this paper 

possible—to Dr. Paul Bartsch, of the United States 

National Museum, for placing the Museum collections 

at my disposal; to Dr. O. B. Hopkins for permission to 

publish on the collections of the International Petroleum 

Co., deposited in the National Museum; to Dr. Axel 

Olsson for the loan of specimens from his personal 

collection; to Messrs. Wendell P. Woodring and 

Wendell C. Mansfield, of the United States Geological 

Survey, for valuable discussion concerning the stratigraphy of South and Central America and the Atlantic 

Coastal Plain, respectively; to Mr. Ralph Stewart, of 

the United States Geological Survey, for frequent 

advice and encouragement; to Miss Julia Gardner, of the 

United States Geological Survey, for information 

regarding the stratigraphy of the Gulf Coastal Plain; 

to Dr. Katherine V. Palmer, of the Paleontological 

Research Institution, for access to the institution's type 

collections and for supplying numerous photographs, 

and to Dr. Pearl Sheldon, of the same institution, for her 

opinions; to Dr. Charles W. Merriam and his assistants 

for access to specimens in the Cornell Museum; to Dr.

L. R. Cox, of the British Museum, for photographs and 

topotypes from Nigeria; to Dr. Takumi Nagao, of the 

Hokkaido Imperial University, for photographs of 

his homonym and permission to rename it; to Prof. 

Jan Nowak, of the Jagiellonian University at Krakow, 

for photographs of Grzybowski's Peruvian types; 

to Dr. B. G. Escher, of the Rijksmuseum van Geok^ie 

en Mineralogie, for supplying photographs of t;Tpe 

specimens from Java; to Dr. Horace G. Richards, of 

the New Jersey State Museum, for the loan of Pliocene 

and Pleistocene specimens from the Atlantic cor,st; 

to Dr. Henry A. Pilsbry, of the Academy of Natural 

Sciences of Philadelphia, for the loan of some of Conrad's 

types; to the Geological Department of Johns Hopkins 

University for the loan of the types of Noetia cholana 

Spieker; to Mr. Herman Gunter, State geologist of 

Florida, for the loan of specimens from the Florida 

State Museum; to Dr. S. F. Blake, of the United States 

Department of Agriculture, for the loan of specimens 

from his private collection; to Dr. Hollis Hedberg for 

specimens from Venezuela; and to Dr. Philip W. 

Reinhart for forwarding photographs of the type of 

Noetia triangularis Gray which he obtained from Dr. 

Cox, of the British Museum.

CLASSIFICATION

With our increasing knowledge of the structure £.nd 

phylogeny of the Pelecypoda it becomes more and more 

obvious that their supergeneric classification is short 

of satisfaction, the principal defect being that not 

enough groups of high ordinal rank have been recognized. I agree with Stewart * that an elaboration of the 

classification of Pelseneer is in most respects the most 

satisfactory and natural. The arrangement here presented was arrived at as a result of some researches in 

the structure and evolution of the ligament of the ar^id 

pelecypods and will be supported more fully in a paper 

on ligament structure to be published soon. Under 

this arrangement the order Filibranchia is divided into 

suborders represented by the genera Pecten, Anomia, 

Mytilus, and Area. The true taxodonts, of course, 

represented by the genera Nucula, Nuculana, etc.,

i Stewart, Ralph, Acad. Nat. Sci. Philadelphia, Special Pub. 3, p. 26,1930.
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 193t

belong to the order Protobranchia. This classification, 

insofar as it concerns the Noetinae, is given below:

Suborder Prionodonta:

Cyrtodontacea, Parallelodontacea, Glycymeracea, Arcacea. 

Superfamily Glycymeracea:

Cucullaeidae, Glycymeridae, Naviculidae, Limopsidae,

Noetidae. 

Family Noetidae:

Striarcinae, Trinacriinae, Noetinae. 

Subfamily Noetinae.

The subfamily Noetinae includes all the species 

generally referred to the genus Noetia and, in addition, 

some Eocene forms which are regarded either as prototypical or as closely related to them. These forms have 

vertically striated ligaments, as do all the Noetidae. 

The earliest members are orthogyrate or prosogyrate, 

but the later members are all opisthogyrate.

Their sculpture consists of well-defined secondary 

ribs, frequently alternating with small interstitial 

primary ribs. The species here included in the Noetinae 

are referred to eight genera and one subgenus. The 

genera can be divided into two well-defined supergeneric groups, an Atlantic group and a Pacific group, 

according to the region in which their species predominate. Although, heretofore, the majority of the 

species of the later Tertiary (called Neogene by European geologists) have been placed in the same genus, 

the geologic history of the two groups and the dissimilarity of the earlier members leaves it still to be proved 

that they are related at all. A new subfamily may 

ultimately be erected for one of them.

Several important nomenclatorial changes will be 

noted in this paper. Scapularca Cossmann is included 

in this subfamily but is treated as a genus, not as a 

subgenus of Arcopsis, which is referred to the Striarcinae. Sheldonella Maury is raised to the rank of genus 

and is made to include Paranoetia Thiele as a subgenus. 

Noetiella Thiele and Jaeckel 2 is not included but is 

referred to the Striarcinae. The recognition of the 

Peruvian Eocene and Oligocene species of "Argina" 

as belonging to the Noetinae is probably the most 

unexpected change set forth in this paper. Trigonodesma Wood is clearly a member of the Striarcinae.

GEOGRAPHIC AND STRATIGRAPHIC OCCURRENCE OP 

THE NOETINAE

The broader contribution of this paper is to show that 

the genera referable to the Noetinae are divisible into 

two distinct supergeneric groups. These are here called 

the Atlantic and Pacific groups, according to the region 

in which they obtain their maximum development. 

The Atlantic group comprises three genera and a subgenus—Eontia, n. gen., which has for its genotype

2 These authors made Barbatia pectunculiformis Dunker the type of this section, 

but their species Area (Noetiella) congoensis is more like Area (Barbatia) interplicata 

Qrabau and King (Shells of Peitaiho: Peking Soc. Nat. History Handbook 2, p. 161, 

pi. 1, fig. 9, 1928) and Area bataciana Martin and Wichmann (Geol. R. Mus. Leiden 

Samml., Ser. 1, Band 3, p. 253, pi. 13, fig. 257, 1885) than the type. In all these forms 

the ribs are primary and not secondary as in the N oetinae.

Area ponderosa Say; Sheldonella Maury, typified by 

Noetia (Sheldonella) maoica Maury, and its subgenus 

Paranoetia Thiele, for which the genotype is Area 

lateralis Reeve; and the prototypical Eocene genus 

Scapularca Cossmann, for which the genotype is Area 

scapulina Lamarck. The Pacific group consists of five 

genera—Noetia Gray, typified by Area reversa Sowerby; 

the prototypical Eocene genus Protonoetia, n. gen., 

having for its genotype Anadara nigerier,sis Newton; 

and three aberrant genera: Noetiopsis, n. gen., for which 

the genotype is N. woodringi, n. sp.; its terminal genus, 

Arginopsis, n. gen., for which the genotype is Scapharca 

(Argina) sullanensis Woods; and a rented genus, 

Arginella, n. gen., having for its genotype Area (Argina) 

samanensis Olsson.

ATLANTIC GROUP

The genera and species according to this classification 

fall into an orderly geologic and geographic arrangement.

Scapularca occurs in the Eocene of England, France, 

and Belgium and exhibits a series ranging from the 

limopsiform S. subglobulosa (Wood), from the Bracklesham and Bartonian, to the more extreme French 

forms, the carinate S. interposita (Deshayea), the prototype of Eontia, on the one hand, and thQ- posteriorly 

rounded S. scapulina (Lamarck), the prototype of 

Sheldonella, on the other hand.

The genus Sheldonella is, so far as known, the smallest 

group of late Tertiary Noetinae. Only one species, 

the genotype, Sheldonella maoica Maury, appears to 

have reached America, where it occurs in the Cercado 

formation, of early middle Miocene age, of the Dominican Republic. It has not been found elsewhere in 

America and may have become extinct before the advent 

of Eontia in late Miocene time, unless, as discussed 

beyond, the southern species tentatively referred to 

Eontia (E. centrota, E. bisulcata, and E. olssoni) are to 

be regarded as representing a subgenus of it. The 

other two species for which the subgeneric name 

Paranoetia is available are Recent from the Southern 

Hemisphere and Indo-Pacific, P. cafria (Bartsch) 

occurring off South Africa, and P. lateralis (Reeve) in 

the Philippines.

The genus Eontia exhibits great diversity and contains some of the largest members of tie subfamily. 

The last occurrence of the Noetinae in Europe and the 

earliest known Neogene species is E. oktni (Mayer), 

from the Aquitanian, Burdigalian, and Helvetian. 

Eontia is next known in America, where it occurs as 

E. incile (Say) in the (7Aama-bearing bed of the Yorktown formation, of upper Miocene age, of Virginia; and 

as E. incile mansjieldi, n. subsp., in the equivalent or 

slightly older Ecphora zone of the Choctavhatchee formation of Florida. One small valve of the southern 

group tentatively referred to Eontia, E. cf. E. centrota, 

has been reported from the Springvale Miocene of
SPECIES AND GENERA OF TERTIARY NOETINAE

Trinidad by Maury. Species reported from earlier 

Caribbean Miocene formations belong to the genus 

Noetia and are discussed below.

In the southern province there were derived from 

the Springvale species E. centrota (Guppy), from 'the 

Pliocene of Trinidad; and two Recent species—E. bisulcata (Lamarck), from the Atlantic and Caribbean 

coasts of South America; and E. olssoni (Sheldon and 

Maury), from the Pacific coast of Panama, an Atlantic 

shell which somehow gained access to Pacific water.

Along the Atlantic coast of North America we find 

in the progeny of E. incite some of the most conspicuous 

elements in the uppermost Miocene to Recent faunas. 

In the upper part of the CTwma-bearing bed of the Yorktown formation the variety E. incite yorkensis, n. var., 

occurs with typical E. indie. In the next higher beds, 

equivalent to those exposed at Yorktown, a more robust 

form of E. incite occurs. This gives rise to another 

varietal series in the next higher beds, the beds at 

Suffolk, containing as an end member E. incite suffolkensis, n. var.

Eontia trigintinaria (Conrad) occurs in the Duplin 

marl of central North Carolina; the Darlington and 

Maysville districts in South Carolina; in the equivalent 

part of the Yorktown formation of Virginia and North 

Carolina; and specimens from the Cancellaria zone of 

the Choctowhatchee formation ot western Florida are 

referred to it. This form appears to have been derived 

from E. indie during middle Yorktown time, as it is distinct from the forms occurring in the beds at Suffolk, Va.

In the Miocene in the vicinity of the Chowan River 

in northeastern North Carolina, which may be higher 

than the typical Duplin, is found the form E. carolinensis (Conrad). In Greene County, N. C., which lies 

between this region and the area of the typical Duplin, 

a varietal series occurs which approaches E. carolinensis on the one hand and E. trigintinaria on the other. 

These appear to be the forms which Conrad named 

Noetia Jilosa and Noetia protexta, respectively. The 

former is regarded as a variety, E. trigintinaria Jilosa; 

the latter is placed in synonymy.

In southern North Carolina, around Lumberton 

and Fairmont, occurs E. lumberensis, n. sp., which has 

more the form of some Pliocene specimens from the 

Waccamaw formation but remains small. The upper 

bed at Colerain Landing, on the Chowan River, differs 

from the bed beneath in that it contains a varietal series 

which seems to foreshadow the extremely variable form 

found in the Pliocene Waccamaw formation of the 

Carolinas and the Pliocene of eastern Florida.

In the Pliocene, as in the Miocene, both very regular 

and very variable species are found. Eontia limula 

(Conrad), a remarkably constant species, related to 

E. carolinensis, occurs only in the Croatan sand along 

the Neuse River and in Onslow County, N. C., and 

possibly in east-central Florida near Melbourne. 

Another form, E. tillensis, n. sp., from Tilly's Lake, on

the Waccamaw River, S. C., seems to represent the 

E. carolinensis or the E. trigintinaria Jilosa stock. The 

Waccamaw formation of North Carolina in the vicinity 

of the Cape Fear River contains the variable form 

E. variabilis, n. sp., which appears to be a mixture of 

several Miocene stocks as well as other Pliocene species. 

One of its varieties, E. variabilis guadrata, n. var., 

from the Walkers Bluff locality on the Cape Fear 

River, appears to be closely related to E. lumberensis. 

The Caloosahatchee marl of east-central Florida in the 

vicinity of De Land and De Leon Springs contain^ a 

form which resembles E. variabilis less than it resembles the form occurring in the Caloosahatchee marT of 

southwestern Florida. Two forms, which from their 

preservation occur in different beds, are found in the 

spoil along the Hurricane dike of Lake Okeechobee 

near Clewiston, Fla. One, E. caloosana, n. sp., a very 

constant form, is apparently from the lower bed. ^he 

less leached shells consist of a varietal series ranging 

from fairly typical E. variabilis to a large, rotund fo^m, 

E. variabilis clewistonensis, n. var., which may b<? a 

hybrid of E. variabilis and E. caloosana.

In the Caloosahatchee marl of southwestern Florida, 

at the Alligator Creek and Shell Creek localities, another varietal series occurs which contains forms not 

found elsewhere. The name Eontia platyura (D.^ll) 

is available for this species. This form seems to be 

related to E. caloosana, but whether the E. variabilislike form farther east contributed anything to it is 

uncertain.

Higher in the Caloosahatchee marl of southwestern 

Florida, near Bermont, a form indistinguishable from 

the De Leon Springs form is found, which may have invaded from the east at this time. The uppenrost 

Pliocene near Murdock, Fla., contains a shell comparing 

almost exactly in shape with the recent E. ponderosa 

but differing somewhat in sculpture. This appears to 

represent a coalescence of E. variabilis and E. platyura.

During Pleistocene time this pie-ponderosa stock 

persisted on the Florida west coast. Along the Atlantic 

coast several distinct types are found, two of them 

recognized as species—one in the vicinity of Vero, in 

east-central Florida, called Eontia veroensis, n. sp., and 

the other north of Cape Hatteras, described as E. 

palmerae, n. sp. The former may be related to an 

E. limula-iike Pliocene form from the same region; the 

latter is probably directly descended from E. tillensis 

or possibly E. limula in the north. In the intervening 

area, from Cape Hatteras to the vicinity of Daytona, 

Fla., a robust, variabilis-like form occurs which approaches both the northern and the southern forms. 

When the Florida west, coa^t stock joined with the 

Atlantic stocks is not certain, but in the late Pleistocene 

the union appears to be complete, and in the Recent 

there remains the single long-ranging, remarkably 

constant species E. ponder osa. This has been obtained 

living from Cape Hatteras to Yucatan.
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Eontia ponderosa migrated at least as far as Louisiana 

during Pleistocene time, very typical specimens having 

been obtained from a well in Plaquemines Parish at a 

depth of 740 feet and another well in Cameron Parish 

at a depth of 912-972 feet. Owing to the rapid deposition in this region, even these depths represent fairly 

late Pleistocene. Attention is called to the possibility 

of confusing young specimens of Eontia ponderosa from 

the Pleistocene of the northern Gulf region with the true 

Noetia, N. gardnerae, n. sp., specimens of which have 

been obtained from the upper Miocene or Pliocene 

near Houston, Tex., at a depth of 1,700 feet. The 

specimens obtained from the deep well at Galveston, 

Tex., at a depth of 2,552 to 2,871 feet and identified by 

G. D. Harris as Area ponderosa var. carolinensis 

Conrad, are probably Noetia gardnerae. (See p. 37.)

Just what processes are involved in the history of the 

North American Eontias may be a debatable question, 

but the suggestion is strong that both geographic 

speciation and later hybridization have taken place. 

Some stocks may have become extinct, but the persistence of certain strains in later varietal series and the 

gradual evolution of a constant form from an almost 

hopeless complex strongly suggests that most of the 

forms remained interfertile and gradually interbred to 

produce hybrid series from which a true breeding 

species emerged.

PACIFIC GROUP

The Pacific group, for the most part, occupied geographic areas different from those of the Atlantic group. 

Unlike the Atlantic group, which did not reach its 

maximum development until Pliocene time and still 

survives in three seas, the Pacific group is far in the 

decline. Only a single, relatively restricted species 

survives.

This group was already a complex of five related 

genera in middle and upper Eocene time. Of these, 

three did not survive the Eocene, one culminated in the 

Oligocene, and the most abundant, Noetia, gave rise 

to a large number of upper Eocene to Recent species, 

attaining its maximum development in the middle 

Miocene. The genus Noetiopsis, n. gen., typified by 

N. woodringi, n. sp., from the middle Eocene of the 

Tonosi Valley, Los Santos Province, Panama, although 

strikingly Noetia-like in general appearance, appears 

to be the predecessor of the aberrant genus Arginopsis, 

n. gen., typified by A. sullanensis (Woods) from the 

late Eocene Saman and Talara formations of Peru. 

Arginella, n. gen., another aberrant genus, for which 

the genotype is A. samanensis (Olsson), likewise from 

the Saman and Talara formations, is known from two 

species besides the genotype—A. puntabravoensis (Olsson), from the middle Oligocene Mancora grits of 

Peru, and the end member, A. ovalis, n. sp., from supposed Oligocene beds of Colombia.

Protonoetia, n. gen., for which the genotype is P. 

nigeriensis (Newton)f is found in beds of Lutetian age

near Ameki, Nigeria. This genus is less like Noetia 

in general appearance than Noetiopsis is, but it is more 

closely related to Noetia in some fundamental characters and is regarded as representing the stock from 

which the true Noetias of the upper Eocene of the 

Indo-Pacific were derived.

The upper Eocene forms from the Indo-Pacific appear 

to be congeneric with the later American forms. Of 

the former are known Noetia pondaungensis Cotter, 

from Burma; Noetia molengraffi (Martin), from Java; 

and Noetia nagaoi, n. name, from Japan. It cannot 

be said with full certainty that the American Miocene 

to Recent species of Noetia were descended from these 

upper Eocene Indo-Pacific forms. So far only the 

aberrant genus Arginella has been found in the American Oligocene. Although the time interval was ample 

for the migration of Noetia to America, a fuller knowledge of the Pacific Oligocene is needed to show whether 

the genus was present previously, or, if a migrant, 

what course its migration took.

The oldest occurrences of Noetia in America are in 

beds generally considered to be of lower Miocene age. 

Unfortunately none of the species are represented by 

sufficient specimens to show variation to any great 

extent, so that the relationships of the species are not 

always clear. Knowledge of the stratigraDhy of the 

regions in which they occur is still largely in. the reconnaissance stage and, owing to the covering of dense 

vegetation in most of the areas, will probp.bly remain 

so for a long time to come. It is not possible, therefore, 

to attempt as detailed a study of these species as was 

made of the North American species of Eontia, and 

little more can be done than to recognize species and 

varieties and to make simple comparisons with supposedly related forms.

The earliest known species are Noetia stewarti, n. sp., 

from the lower Zorritos formation and the underlying 

transitional beds of Peru, and two species, N. trinitaria 

(Guppy) and N. manzanillae Maury, from the Manzanilla beds of Trinidad. The species N. manzanillae 

is aberrant, whereas the other two are somewhat 

related. The diversity of these forms, as veil as their 

separated occurrence, provides considerable ground for 

hope that their predecessors will be found in more 

than one earlier Central and South American formation.

Higher, in the middle Miocene, are found Noetia 

mundonuevensis Maury and N. mayensis Maury, in the 

Brasso beds of Trinidad. Noetia mauryae, n. sp., from 

northern Colombia is related to N. mayensis. The 

middle Zorritos of Peru contains the form N. cholana 

Spieker, of uncertain affinities. N. ecuad-oria, n. sp., 

from Ecuador, appears to be related to N. trinitaria 

and to several contemporaneous and later species as 

well. In Colombia occur two forms, N. atratoensis, 

n. sp., and N. Colombians, n. sp., the former related to 

a variety of N. macdonaldi, whereas the latter appears
SPECIES AND GENERA OF TERTIARY NOETINAE

to be related to N. ecuadoria and N. trinitaria, on the 

one hand, and to typical N. macdonaldi Dall, on the 

other hand. N. retractata (Hanna and Israelsky) 

(=N. modesta Grzybowsld) occurs in the upper Zorritos of Peru.

Noetia macdonaldi Dall occurs at several horizons in 

the Gatun formation of Costa Rica, and a specimen is 

at hand from far up the Atrato River Valley, in western 

Colombia. This species may not be identical in all 

beds along the Banana River in Costa Rica, and a 

subspecies, N. macdonaldi alta, n. subsp., is named, 

which resembles the Colombian species N. atratoensis. 

Another form, N. macdonaldi truncata, n. subsp., is 

recognized in northern Colombia. N. turbacensis, n. 

sp., from northern Colombia may be upper Miocene.

The upper Miocene Tumbez formation of Peru contains a gigantic form which may not be distinct from 

N. mag-na, n. sp., from the Mancora Tablazo beds, of 

Pleistocene age, of Peru.

Noetia gardnerae, n. sp., obtained from an oil well 

near Houston, Tex., at a depth of 1,700 feet in sediments of upper Miocene or Pliocene age, is the only 

species of the Pacific group to gain a foothold in the 

northern Gulf region. The Pliocene species N. sheldoniana Maury is known from the upper Pliocene of 

Trinidad and appears to be related to N. gardnerae and 

possibly to N. turbacensis. N. reversa, the genotype, is 

the only surviving species of the group and occurs along 

the west coast from the Gulf of California to Peru.

CHARACTERS IN WHICH THE ATLANTIC AND PACIFIC 

GROUPS DIFFER

It has been suggested by several writers that certain 

of the species referred to the genus Noetia. were more 

closely related to one another than to other species. 

So far as I am informed, however, no one has previously suggested that these species constitute two 

groups of genera which have been independent of each 

other throughout most of Tertiaiy time. On the contrary, owing to the remarkable example of homeomorphy that some Pliocene and Recent species show, 

such a suggestion may seem ill advised to workers who 

are familiar with many of the species involved.

That such a condition exists, however, can be shown 

in several ways. First, only the more recent of the 

two groups, Noetia sheldoniana, N. gardnerae, N. reversa, 

and Eontia ponder'osa, are at all liable to be confused, 

and the farther back their progenitors are traced 

the less alike they are seen to be; second, the periods 

of maximum development and the geographic areas 

in which the species are concentrated differ for the 

two groups; third, regardless of the great similarity 

which the homeomorphic species show, the groups to 

which they belong are characterized by certain morphologic differences, developmental tendencies, or 

known differences in evolution that distinguish them. 

These may be listed as differences in sculpture, in the

nature of the postero-ventral crenulations of the inner 

margin, and in the distribution and evolution of the 

cardinal area and ligament.

DIFFERENCES IN SCUIPTURE

The sculpture found in the genera of the Noetinae 

may take a variety of forms, but its relation to the 

juvenile sculpture shows that it is all of the same type. 

The ribs are of two kinds, primary and secondary, 

according to the time of their appearance in the ontogeny of individuals of most genera. Whether they have 

the same order in their phylogeiiy is unproved, but it 

is suggested as a hypothesis that they have, and that 

the primary ribs correspond to the lirate ribs of other 

members of the Noetidae. The primary ribs are 

referred to in the descriptions as the interstitial rbs, 

whereas the secondary ribs are the principal ribs in the 

adult sculpture. The primary ribs are of varying importance and may be well developed or obsolete in 

adults. The secondary ribs are always well developed 

and furnish the strong sculpture of the Noetinae. In 

fact, the subfamily might be defined as including 

Noetidae with strong secondary ribs.

Both the primary and secondary ribs vary in surface 

and cross section. The primary ribs are usually lirate 

in juveniles and beaded in adults but may remain lirate 

throughout. The secondary ribs may be smooth and 

rounded throughout but generally are beaded in juveniles. In adults they differ within the same genus, in 

different genera, and in different parts of the same si all. 

They may divide or remain single. They may tend to 

become more elevated or less elevated, or even submerged below the level of the interspaces with shell 

growth. In cross section they may range from low and 

broadly rounded to high and flat-topped.

In the accompanying text figure (fig. 1) are shown 

diagrams of the sculpture of the genera of the Noetinae 

in which the nealogic sculpture 3 is known. The scale 

is of course exaggerated, and no attempt is made to 

show the actual number of ribs. Likewise, an arbitrary 

beaded line is used to designate the primary ribs, wlich 

may be finely lirate, especially in the juvenile stages

In Scapularca the sculpture consists of alternate targe 

and small ribs. No difference is to be observed between 

the juvenile and adult sculpture, the ribs having their 

origin almost simultaneously at the end of the unsculptured iiepionic stage. The shell of Scapularca is small, 

and a nealogic stage comparable in size to that of the 

other genera to be discussed would occupy most of the 

shell. It is inferred, therefore, that the nealogic stage 

is so short in duration as to be practically unobsorvable. The important fact regarding the initial sculpture of Scapularca is that the ribs are subequal in

3 Jackson defined four stages in shell growth succeeding, the embryonic or p-odissoconch stage—the nepionic stage, or the unsculptured first stage in the format'on of 

the true shell; the nealogic stage, or the stage of initial sculpture, which may differ 

considerably from the adult sculpture; the ephebolic stage, or the adult stage; ar d the 

geratologic stage, or the period of decline and irregularity.
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

strength at that stage and that the secondary ribs become more prominent with shell growth.

The sculpture of Sheldonella, following the nepionic 

stage, consists of well-defined nealogic and adult stages. 

The primary ribs are lirate in the nealogic stage and 

become delicately beaded in adults. The secondary 

ribs do not make their appearance until the end of the 

nealogic stage, and at that time they appear first along 

the umbonal ridge. Those along the umbonal ridge 

become divided into two equal parts in adults and, like 

the primary ribs, are neatly beaded. Anteriorly they 

may or may not be beaded, a condition which varies 

with individuals. It will be noted that in Sheldonella 

the primary or interstitial ribs usually persist throughScapularca Sheldonella

Noetia and Protonoetia Eontia 

FIGUBE 1.—Diagrams showing relation of adult sculpture to nealogic sculpture.

out the adult stage, although in some individuals they 

may be obsolete medially.

Eontia, the most important genus in the Atlantic 

group, exhibits the most varied sculpture in the subfamily. Like Sheldonella it has three well-defined 

stages—the unsculptured nepionic stage, the primaryribbed nealogic stage, and the adult stage. The primary ribs are very well developed in the nealogic stage, 

and frequently additional primary ribs may appear, as 

shown medially in the diagram. With the appearance 

of the secondary ribs the primary ribs are transformed 

abruptly from coarse lirae to finely beaded interstitial 

threads which from then on may behave in various ways. 

They may increase in size throughout the life of the shell, 

or they may become obsolete, especially medially, or 

they may die out temporarily and reappear near the 

ventral margin.

The secondary ribs appear near the end of the nealogic stage, first along the umbonal ridge, and rapidly 

become larger tnan the primary ribs. They present 

considerable variation. They may be single throughout or double only in the region of the umbonal ridge, or

on the medial and anterior parts of the disk as well. 

They may be rounded or square in cross section. They 

may be smooth or evenly beaded or roughened by irregular growth varices. In several respects the sculpture of 

Eontia is the most extreme in the Noetinae; the primary 

ribs are stronger in the nealogic stage than in other 

genera, the secondary ribs are more varied, and the 

break between the nealogic and adult stages is much 

more abrupt.

In the genera Noetia and Protonoetia tl e nealogic 

sculpture is very similar to that of SheMonella and 

Eontia, but the primary ribs are not as strong. In a 

few species of Noetia the interstitial ribs persist to the 

ventral margin, but usually only in the posterior region. 

In many species the primary ribs become 

obsolete at some time during the adult stage, 

so that there is really a young r.dult stage 

characterized by both primary and secondary 

ribs and a later adult stage having secondary 

ribs only. In a few species (Noetia sheldoniana, 

N. gardnerae} the weak primaries persist into 

the adult stage scarcely at all, and the regular 

secondaries can be traced to a very young stage. 

The secondary ribs make a mc^e gradual 

appearance in Noetia than in Sheld,onella and 

Eontia, and therefore there is not PO abrupt a 

break between the nealogic and adult sculpture. One outstanding difference between the 

Atlantic and Pacific groups is the regularity 

of the secondary ribs. Those of the Pacific 

group are never divided and are usually of the 

same size and spacing all over the di^k and posterior slope, but in a few species—N. reversa, N. 

colombiana, and typical N. macdonaldi—those 

on the anterior part of the disk may be wider, 

lower, and broadly rounded. In the genera Sheldonella 

and Eontia the ribs along the umbonal ridge are always 

the largest and usually double or irregular'y divided. 

Those on the medial and anterior part of the disk are 

smaller and may or may not be divided.

What conclusions should be drawn from the relation 

of the nealogic sculpture to the adult sculpt\ire in these 

genera may be a matter of considerable controversy, 

but it is suggested that they are not interdependent, 

either being capable of developing independently of the 

other. The suggestion of independent evolution for 

the juvenile and adult sculpture is not an orthodox idea, 

but it seems that in the Atlantic group there was a 

change through geologic time, from a type (Scapularca) 

in which the adult sculpture was a surple magnification of the juvenile sculpture to a type (Eontia} 

in which both juvenile and adult sculpture? differed in 

different respects from that of the geologically earlier 

type. This might, of course, be explained as a progressively later appearance of the secondary ribs, 

allowing the primary ribs in the nealogic stage greater 

opportunity for development.
SPECIES AND GENERA OF TERTIARY NOETINAE

THE LIGAMENT

Any discussion of the ligament of the arcid Pelecypoda 

must consider two features'—(a) structure and (&) 

distribution on the cardinal area.

The so-called vertically striated ligament, which 

characterizes the Noetidae, consists of two layers— 

(1) a multiple elastic layer, the elements of which grow 

normal to the hinge line and are suspended within (2) 

a fibrous layer that is in contact with the shell. With 

shell growth the active portion of the ligament is 

severed, and the cardinal area of each valve retains 

half of the defunct ligament. The distribution of this 

inactive ligament thus determines the so-called ligament area, and its form, of course, varies with the 

structure and location of the active ligament along 

the hinge line. As all the Noetinae have essentially 

the same structure, it does not seem necessary to discuss 

anything but the actual distribution of the inactive 

ligament on the cardinal area. Before passing on, 

however, a few remarks should be made concerning the 

vertical grooves.

In the Noetinae are found two kinds of vertical, 

grooves. The larger grooves, to which alone attention 

has been called, indicate the position of the nonfibrous 

vertical elements. These are not attachment grooves, 

for the elastic layer is suspended within the fibrous 

layer, but areas in which the fibrous layer has become 

more deeply impressed in the shell to accommodate the 

vertical elements. The smaller and less regular vertical 

grooves are small cavities between the fibrous layer and 

the shell. These contained minute lobes of the mantle 

which apparently extended for a short distance up the 

cardinal area under the fibrous layer. Their purpose 

and function are unknown. These fine grooves, which 

are easily seen with a hand lens, have not been observed 

elsewhere in the Prionodonta but are found in some 

genera of both the Atlantic and the Pacific Noetinae. 

They are particularly developed in adults of Arginopsis, 

Protonoetia, Noetia, Paranoetia, and Eontia. So far they 

have not been observed in Scapularca or Sheldonella s. s., 

although many specimens of the latter have been examined. They are not well developed in the young 

stages of Eontia and frequently do not appear until 

the shell is well into the juvenile stage. This character, 

together with the well-developed secondary ribs, is 

further evidence that the Atlantic and Pacific groups 

constitute a natural subfamily, despite the dissimilarity 

of their earliest known members.

The ligament pattern of the Atlantic group is more 

nearly equilateral throughout than that of the Pacific 

group, in which both completely anterior and completely 

posterior ligaments are found. In the earliest genus 

of the Atlantic group, Scapularca,, the ligament area 

ranges in shape from that of a nearly isosceles triangle to 

that of a triangle somewhat more produced posteriorly, 

but in all forms a considerable portion of the area 

at both ends is left bare. In the late Tertiary genera

145333—38——2

Eontia and Sheldonella s. s. the ligament filh the 

anterior portion of the area completely and in progressively later forms tends to occupy more and more of the 

posterior portion. This can be observed both as an 

evolutionary tendency and as a feature in the development of individuals, the posterior extension cf the 

ligament being shorter in juveniles than in adults. 

In adults of the Recent subgenus Paranoetia the ligament extends from the anterior to the posterior terminus 

of the cardinal area. Nearly the same development 

occurs in the Eontia ponderosa group, but in this group 

it is aided by a secondary posterior shortening of the 

hinge line.

In the Pacific group Protonoetia, an Eocene genus, 

has a ligament area that fills the anterior part of its 

cardinal area completely and extends about half as far 

posteriorly as well. In the upper Eocene to Eecent 

genus Noetia the ligament likewise fills the anterior 

part of the area but is more restricted posteriorly. 

Noetia includes a series from high-beaked forms in 

which the cardinal area and ligament are wider beneath the beaks, with the ligament extending a short 

distance posteriorly, to low-beaked forms in which the 

cardinal area is narrowest beneath the beaks and the 

ligament area is entirely anterior. Supposedly the 

primitive type of the Pacific Noetinae had a E early 

equilateral ligament similar to that of Scapularca, and 

the early genera of the Striarcinae, particularly Bremarca, Arcopsis and Striarca. Development fron? this 

symmetrical type produced on the one hand the type 

with chiefly anterior ligament, as described for Protonoetia and Noetia, and on the other hand the opposite 

extreme, with chiefly posterior ligament, such as is 

found in the genus Noetiopsis, in which the ligament 

completely fills the posterior part of the area and about 

half of the anterior part, just the opposite of the condition in Protonoetia. Arginopsis carries this process to 

the extreme in that the ligament is entirely posterior 

to the beaks. Arginella, a genus similar to Arginopsis 

in having its ligament area wholly posterior to the 

beaks, differs from Arginopsis in that the beaks are 

nearly central rather than anterior, and that a portion 

of the cardinal area anterior to the beaks is lunuHike.

The vertical ligament elements are more uniform in 

size and spacing in the Pacific group than in the A tlantic group, although in the strongly opisthogyrate members of both groups they tend to be stronger anteriorly. 

Moreover, in the Pacific group the vertical elements are 

distributed throughout the length of the ligament, no 

part being without them. In the Atlantic group considerable variety occurs. In Scapularca the grooves 

are evenly distributed anteriorly and posteriorly, but 

the initial groove, the one originating at the ap«,x of 

the area, is stronger than the others. In juveniles of 

Sheldonella and Eontia equally strong grooves are 

added anterior to the initial groove, but the posterior 

part of the ligament consists of fibrous ligament only.
8 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

The South American Eontia centrota and E. bisulcata 

do not progress beyond this stage. Among the North 

American species of Eontia a series of forms shows all 

degrees of development of the vertical elements, from 

forms in which only one or two anterior elements are 

added to the initial groove (E. incite mansfieldi) to 

forms in which vertical elements are evenly distributed 

throughout the length of the ligament (E. limula).

CRENUIATIONS OF THE INNER MARGIN

The nature of the posteroventral crenulations of the 

inner margin is a character that at first suggestion 

might be ignored, but I have yet to see a specimen that 

could not be correctly assigned to its proper group by 

this character alone. In the Atlantic group the crenulations are short, broad, and comparatively shallow. 

In the Pacific group they are deep, narrow, and roundbottomed and are two to three times as long as in 

Atlantic shells of the same size.

DESCRIPTIONS OF SPECIES

ATLANTIC GROUP 

Genus SCAPULARGA Cossmann

Scapularca Cossmann, in Cossmann and Peyrot, Conchologie 

n§og6nique de TAquitaine, tome 2, livr. 1, p. 192, 1913.

Scapularca Cossmann, Catalogue illustr6 des coquilles fossiles 

de 1'Eocene, app. 5, p. 100, 1913.

Type species: Area scapulina Lamarck.

Shell ranging in shape from sublimopsiform to 

modioliform or carinate arciform. Beaks straight or 

slightly prosogyrate, moderately high to low. Ligament area ranging from nearly symmetrical in the more 

limopsiform species to more elongate posteriorly in the 

modioliform species. The anterior part of the area is 

never completely covered with ligament, as in the later 

opisthogyrate genera. Sculpture consists of larger 

ribs alternating with smaller, beaded ribs which may be 

reduced to mere beaded lirae. Teeth of variable 

number—as few as 9 in the shorter species, as many as 

20 in the longer species.

Although recognized here for the first time, there 

seems to be little to dispute the thesis that this genus is 

the forerunner of the later genera Eontia and Sheldonella and that they are already foreshadowed in its extreme species. Scapularca differs from them, however, 

in its small size, the restriction of its ligament anteriorly, 

and the almost simultaneous appearance of the primary 

and secondary ribs in the nealogic sculpture. The 

subequilateral ligament area in Scapularca shows its 

relation to earlier members of the Noetidae, but it 

differs from them in the possession of secondary ribs.

EOCENE SPECIES

Scapularca sub globulosa (Wood) MacNeil

Plate 1, figures 1-4

Area globulosa? Wood, Pal. Soc. Mon., p. 84, pi. 15, figs. 9a, 

9b, 1864 (subglobulosa proposed in text).

Shell obliquely limopsiform, somewhat globular or 

gibbous; beaks moderately low, just anterior of central;

ribs alternately large and small, the larger nearly smooth, 

the smaller distinctly beaded; ligament confined to a 

small triangular central part of the area beneath the 

umbo; teeth divided into two rows, four anteriorly and 

five posteriorly, the posterior teeth much inclined. 

(Emended description.) 

Length 3 millimeters, height 2 + millimeters 

This species, with its nearly equilateral cardinal 

area, median beaks, and central ligament, mcst nearly 

approximates the hypothetical ancestor for the Atlantic 

Noetinae. Its typical noetine sculpture, however, 

still isolates it from any of the other groups of early 

Tertiary Noetidae.

Distribution: Bracklesham and Bartonian, England. 

Type locality: Highcliff, Barton, England.

Scapularca globulosa (Deshayes) Cossmanr

Area globulosa Deshayes, Coquilles fossiles des enviror** de Paris,

tome 1, p. 209, pi. 33, figs. 4, 5, 6, 1829; Animaux sans

vertebres dans le bassin de Paris, tome 1, p. 803, 1860. 

Area (Anadara) globulosa. Cossmann, Catalogue i'"ustre"j*des

coquilles fossiles de 1'Eocene, fasc. 2, p. 141, 1887. 

Area (Anadara) globulosa. Cossmann and Pissarro, Iconographie

des coquilles fossiles de 1'Eocene de Paris, vol. 1, pi. 36,

fig. 110-46, 1904. 

Fossularca (Scapularca) globulosa. Cossmann, Catalogue illustrS

des coquilles fossiles de 1'Eocene, app. 5, p. 101, 1913. 

Trigonodesma (Scapularca) globulosa. Glibert, Mus. Roy. histoire

nat. Belgique Mem. 53, p. 123, 1933.

Shell subrhomboidal, inflated, higher posteriorly than 

anteriorly; broadly rounded posteroventrally, more 

angulate anteroventrally; beaks moderate^ high, 

situated just posterior to the anterior quarter of the 

shell; ribs alternately large and small, tl °- larger 

smooth except for growth lines, the smaller scarcely 

more than beaded lirae; umbonal ridge broadly rounded; 

ligament area triangular, the posterior side about twice 

as long as the anterior; teeth often obsolete directly 

beneath the beak, the posterior ones inclined, about 8 

anteriorly, about 12 posteriorly. (Emended description.)

This species differs from S. subglobulosa in its longer 

hinge line and more arciform shape. The interstitial 

ribs are not as much developed.

Distribution: Lutetian and Bartonian of France ani Belgium.

Scapularca interposita (Deshayes) Cossmann 

Plate 1, figures 5, 6

Area interposita Deshayes, Animaux sans vertebres dans le 

bassin de Paris, tome 1, p. 892, pi. 67, figs. 11-13, 1860.

Area (Anadara) globulosa var. interposita. Cossmann and 

Pissarro, Iconographie des coquilles fossiles c1 ^ 1'Eocene 

de Paris, vol. 1, pi. 36, fig. 110-46-1, 1904.

Fossularca (Scapularca) interposita. Cossmann, Catalogue illustr^ 

des coquilles fossiles de 1'Eocene, app. 5, p. 101, 1913.

Shell subrhomboidal, inflated, the posteric^ margin 

longer than the anterior, somewhat angulate both 

posteroventrally and anteroventrally; beaks high, 

located at the anterior quarter of the shell or just
SPECIES AND GENERA OF TERTIARY NOETlNAE 9

posterior to it; ribs alternately large and small, the 

larger marked by growth varices, the smaller somewhat 

beaded; umbonal ridge rounded but well defined; 

ligament area longer posteriorly, about twice as long 

as anterior in young specimens, about four times as 

long in adults; teeth usually continuous, vertical centrally, inclined terminally, about 7 to 9 anteriorly, 

about 12 to 15 posteriorly. (Emended description.)

Figured specimen (U.S.N.M. 496506), length 6.5 

millimeters, height 4.5 millimeters, convexity 1.5 

millimeters.

This species differs from S. globulosa in being about 

twice as large and in having a more carinate umbonal 

ridge and accentuated sculpture. It may be only a 

variety of S. globulosa, but a decision cannot be made 

from the few specimens at hand. The interesting 

features of this shell are its tendency to form a carinate 

umbonal ridge and the increasing extension of the ligament toward the posterior with shell growth. It 

differs from S. scapulina, in which the umbonal ridge 

is broad and rounded.

Distribution: Lutetian and Bartonian, France.

Scapularca scapulina (Lamarck) Cossmann

Plate 1, figures 7, 8

Area scapulina Lamarck, Mus. histoire nat. Annales, vol. 6, p.

221, 1805; vol. 9, pi. 18, fig. 10, a, b. 

Deshayes, Coquilles fossiles des environs de Paris, tome 1,

p. 216, pi. 33, figs. 9, 10, 11, 1829; Animaux sans vertebres

dans le bassin de Paris, tome 1, p. 898, 1860. 

Area (Anadctra) scapulina. Cossmann, Catalogue- illustre" des

coquilles fossiles de 1'Eocene, fasc. 2, p. 142, 1887. 

Area (Anadara) miliacea Cossmann, idem, p. 141. 

Area (Anadara) scapulina. Cossmann and Pissarro, Iconographie des coquilles fossiles de 1'Eocene de Paris, vol. 1,

pi. 36, fig. 110-48, 1904. 

Area (Anadara) miliacea. Cossmann and Pissarro, idem, fig.

110-47.

Area scapulina. Lamy, Jour, conchyliologie, vol. 52, p. 138,1904. 

Fossularca (Scapularca) scapulina. Cossmann, Catalogue illustre"

des coquilles fossiles de 1'Eocene, app. 5, p. 100, 1913. 

Fossularca (Scapularca) miliacea. Cossmann, idem, p. 101. 

Trigonodesma (Scapularca) scapulina. Glibert, Mus. roy. histoire

nat. Belgique Mem. 78, p. 27, 1936.

Shell modioliform, inflated along the umbonal rostrum; beaks moderately low, situated at about the 

anterior fifth of the shell; ribs alternately large and 

small, the larger nearly smooth posteriorly but somewhat granular centrally, the smaller ribs well developed 

and beaded; both large and small ribs stronger posteriorly; ligament area much longer posteriorly than 

anteriorly but less so in younger stages; teeth crowded 

and more vertical anteriorly, more separated and inclined posteriorly, often obsolete along the central part 

of the hinge line, 6 to 7 anteriorly, 8 to 12 posteriorly. 

(Emended description.)

Figured specimen (U.S.N.M. 496505), length 6.5 millimeters, height 5 millimeters, convexity 2 millimeters.

This species is readily distinguished from the other 

species of Scapularca by its modioliform shape. S.

subglobulosa most nearly approaches it in the perfection 

of its sculpture.

"Area" miliacea Cossmann, "de la forme d'un grain 

de millet", is almost too small to be an adult specimen. 

Juvenile specimens of S. scapulina are less elongate 

than adults and conform to the description of this 

species.

Diversification within the genus Scapularca appears 

to have proceeded in two directions from the subcvate 

form—to the carinate arciform type of S. interposita 

on the one hand, and to the modioliform S. scapvlina 

with its rounded umbonal region on the other land. 

The similarity of the former to Eontia and of the latter 

to Sheldonella suggests that these two late Tertiary 

genera were already foreshadowed among the species 

of Scapularca.

Lamy appears to be the only author to have called 

attention to the similarity of Area scapulina and Kecent 

Indian Ocean species of Paranoetia. He compared 

Lamarck's type with specimens from the Persian Gulf 

identified by Fischer as Area venusta Dunker and ether 

specimens of the same species from Madagascar and 

Zanzibar. The species Lamy had in mind is here 

treated as Sheldonella (Paranoetia) cafria (Bartsch).

Distribution: Lutetian and Bartonian, France. 

Genus SHELDONELLA Maury

Noetia (Sheldonella) Maury, Bull. Am. Paleontology, vol. 5, no. 

29, p. 166, 1917.

Type species: Noetia (Sheldonella} maoica Maur^.

Miss Maury proposed the "new section Sheldonella 

to contain thin, small, trigonal Noetias without the 

angular umbonal ridge."

Aside from the species of Scapularca with rounded 

umbonal areas, only three species of Atlantic Noetinae 

have been described which conform to this definition, 

and two of them appear to be at least subgenerically 

removed from the type. Sheldonetta maoica occurs in 

the lower middle Miocene of the Dominican Republic. 

The other two species, for which the subgeneric rame 

Paranoetia Thiele is available, are Recent from the 

Southern Hemisphere—Area lateralis Reeve, the type of 

Paranoetia, from the Philippines; and Barbatia cafria 

Bartsch, from South Africa.

All these forms have a very neat sculpture. The 

ribs along the inflated umbonal region are prec;«ely 

divided and beaded. The interstitial ribs remain well 

developed posteriorly but may, in some individuals, 

become obsolete medially. I recognize Sheldonella as 

a genus distinct from Eontia because of my belief that 

they are derived from different species of the prototypical genus, Scapularca. The rounded umbonal 

region might not, in itself, be considered sufficient 

reason for treating the three species mentioned as constituting a separate genus, but none of them appears to 

be very closely related to any of the species of Eontia. 

Adults of some species of Eontia have rounded umbonal
10 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

areas, but the juvenile shells are carinate, so that shells 

of the same size are not likely to be confused.

The genotype of Sheldonella possesses a secondary 

ridge on the posterior slope, called the anal ridge. This 

ridge is not present in the subgenus Paranoetia and is 

found only as an occasional individual variation in 

adults of a few of the North American species of Eontia, 

but it is constant and strongly developed in the three 

southern species referred to Eontia—E. centrota, E. 

bisulcata, and E. olssoni. Thus, though these species 

are referred to Eontia on the basis of the angulate 

umbonal ridge, they also agree with Sheldonella in 

possessing an anal ridge, and it may be that they really 

constitute a subgenus of Sheldonella. In that event the 

nature of the umbonal ridge would prove to be inconsistent as a generic character. Unless the group of 

E. centrota-bisulcata can be definitely proved to be 

derived from Sheldonetta, however, it seems best to refer 

this group to Eontia.

MIOCENE SPECIES

Sheldonella maoica Maury

Plate 1, figures 13, 14

Noetia (Sheldonella) maoica Maury, Bull. Am. Paleontology, vol.

5, no. 29, p. 166, pi. 30, figs. 17, 18, 1917. 

Area cuneolus Pilsbry and Johnson, Acad. Nat. Sci. Philadelphia

Proc., 1917, p. 191. 

Area maoica. Pilsbry, Acad. Nat. Sci. Philadelphia Proc., 1921,

p. 407, text fig. 36.

Shell subpteriiform or modioliform, posterior large 

and high, anterior small, shell sulcated and margin 

constricted just anterior of the umbonal region; beaks 

moderately high and opisthogyrate, situated just anterior of the anterior third of the shell; umbonal region 

very large and inflated; posterior slope larger than the 

portion anterior to the ridge in some specimens; anal 

ridge usually well developed; ribs 33 to 38, averaging 

about 35, alternating with small interstitial ribs, large 

ribs double posteriorly, both large and interstitial ribs 

beaded by growth varices; ligament area filling the 

anterior part of the cardinal area completely and 

extending about an equal distance posteriorly, a broad 

strip of the area devoid of ligament posteriorly; teeth 

vertical and very small centrally, inclined terminally. 

(Emended description.)

Holotype (in Paleontological Research Institution, 

Ithaca, N. Y.), length 12 millimeters, height 6 millimeters, convexity 4 millimeters; figured topotype 

(U.S.N.M. 496507).

This species is unique because of its much-inflated 

umbonal ridge. It differs from Scapularca in having a 

different ligament pattern and in being larger, with a 

more alate hinge line and more inflated ridge.

This is the only species with a rounded umbonal 

ridge and modioliform shape known from America. It 

occurs in deposits of early middle Miocene age, whereas 

the carinate type does not make its appearance until

the upper Miocene. The carinate type is known from 

the Aquitanian, Burdigalian, and Helvetian, and the 

inference is strong that we need not look to this early 

American form for the ancestor of Eontia. Furthermore, Eontia incile mansfieldi, nearest to Sheldonella 

maoica both stratigraphically and geographically, is the 

most unlike it of all the species of Eontia.

The structure referred to in the description as the 

anal ridge appears fairly high on the posterior slope and, 

although weakly developed in some specimens, is 

usually quite distinct. Three species that are referred 

to the genus Eontia on the basis of the carinate umbonal 

ridge—E. centrota, E. bisulcata, and E. olssoni—also 

have the anal ridge, and it may be that the affinities of 

this smaU group are really with Sheldonella rather than 

with Eontia:

Distribution: Lower middle Miocene, Cercado formation, 

Dominican Republic.

Type locality: Cercado de Mao, Provincia de Santiago, Dominican Republic. Topotypes, U.S.G.S. 8525.

Subgenus PARANOETIA Thiele

Paranoetia Thiele, Handbuch der systematischer Weichtierkunde, 3. Teil, p. 793, 1934.

Type species: Area lateralis Reeve.

This subgenus was proposed as a subgenus of Noetia 

but in my arrangement falls nearest to the genus 

Sheldonella and is accordingly made a subgenus of it. 

It might be the opinion of some that Paranoetia is 

entitled to stand as an independent genus. If the 

present arrangement is correct, the genotype species, 

Sheldonella maoica, is probably aberrant to the stock 

which produced Paranoetia.

The species of Paranoetia do not have the anal ridge.

RECENT SPECIES

Sheldonella (Paranoetia) lateralis (Reeve) M^cNeU

Plate 1, figures 21, 22

Area lateralis Reeve, Conchologia iconica, vol. 2, Area, sp. 115,

pi. 17, fig. 115, 1844. 

Barbatia venusta Dunker, Novitates conchologica 0-, Mollusca

marina, p. 91, pi. 31, fig. 1, 1870. 

Area (Barbatia) venusta. Kobelt, Conchy lien-Cabinet von

Martini u. Chemnitz, Area, p. 189, pi. 46, fig. 6, 1891. 

Area (Barbatia) lateralis. Kobelt, idem, p. 192, p1 . 46, fig. 12

(Reeve's figure). 

Area venusta. Hedley, Linnean Soc. N. S. Wales, vcf. 30, p. 545,

1905. 

Area (Noetia) lateralis. Lamy, Jour, conchyliolofde, vol. 55,

p. 303 (in part), 1907.

Shell subrhomboidal, considerably narrovrer anteriorly than posteriorly; beaks moderately high, relatively 

higher in adults, situated at about the anterior third 

of the hinge line; umbonal region broadly rounded; 

ribs 33 to 36, averaging about 34, alternating large and 

small, the larger double posteriorly, both large and 

small ribs conspicuously beaded by growth varices; 

ligament almost completely covering the cardinal area
SPECIES AND GENERA OF TERTIARY NOETINAE 11

in adults, but more restricted posteriorly in juveniles; 

teeth vertical centrally, inclined terminally, somewhat 

L-shaped anteriorly. (Emended description.)

Figured specimen (U.S.N.M. 248983), length 16 

millimeters, height 12 milUmeters, convexity 5 millimeters; a larger, worn specimen, length 31 millimeters, 

height 23 millimeters, convexity 10 millimeters.

This species compares somewhat with Sheldonella 

maoica, but is a much larger species and less constricted 

anteriorly. In addition, its ligament covers more of 

the cardinal area. Like S. maoica, which appears to 

have been strongly byssated, P. lateralis apparently 

attaches to objects by means of a byssus, and two 

adults of this species are distorted and worn in spots, 

indicating that some individuals, at least, are rock 

nes tiers.

The identification of Barbatia venusta Dunker as Area 

lateralis Reeve rather than Barbatia cafria Bartsch is 

based on the number of ribs (38) given in the description. It thus compares with A. lateralis, of which the 

number of ribs on specimens in the U. S. National 

Museum ranges from 33 to 36, rather than with B. 

cafria, which has about 30 or 31. It may be that Dunker counted both parts of the bifid ribs on the posterior 

ridge separately or included the interstitial ribs in the 

count, which would give a larger number. If this is 

so it may prove that B. venusta is the east African 

species and not the Indo-Pacific species, in which case 

the synonomy here given would need revision.

The two species were treated together by Lamy as 

A. lateralis but the dimensions and locality records 

which he gives, including unpublished museum records 

and personal communications, makes them easily 

delimitable into a small west Indian Ocean species and a 

larger Indo-Pacific species.

Distribution: Recent, Ceylon, East Indies, Australia, Philippine Islands, and China Sea.

Type locality: Philippine Islands.

Other occurrences: Galle, Ceylon (a specimen from this locality is the largest on record, having a length of 42 millimeters), 

Penang, Malacca Straight (Calcutta Museum); Gulf of Carpentaria, Queensland (Hedley); Manila Bay, Amoy, Formosa 

Strait (U. S. National Museum).

Sheldonella (Paranoetia) cafria (Bartsch) MacNei,!

Plate 1, figures 17, 18

Area venusta. Fischer, Jour, concbyliologie, vol. 39, p. 228,1891. 

Area (Noetia) lateralis. Lamy, Jour, conchyliologie, vol. 55,

p. 303 (in part), 1907. 

Barbatia cafria Bartsch, U. S. Nat. Mus. Bull. 91, p. 183, pi. 38,

figs. 1, 5, 1915.

Shell subrhomboidal, somewhat narrower anteriorly 

than posteriorly, both anterior and posterior ends about 

equally rounded; beaks moderately high, situated at 

about the anterior third of the shell; umbonal region 

very broadly rounded; ribs about 30 or 31, alternating 

with smaller, interstitial ribs, the larger ribs double 

posteriorly, smaller ribs conspicuously beaded by growth

varices; ligament covering nearly the entire cardinal 

area; teeth vertical centrally, inclined termirally. 

(Emended description.)

Holotype (U.S.N.M. 249849), length 14.2 millimeters, height 8.5 millimeters, double convexity 8.6 

millimeters.

This species has a simpler outline than P. lateralis, 

the hinge line being shorter and the dorsal extremities 

more rounded. The medial sulcus is less pronounced, 

and the anterior end of the shell is comparatively larger. 

Of a number of specimens at hand all approximate 14 

millimeters in length, showing that it is a smaller 

species than P. lateralis.

Distribution: Recent, west Indian Ocean from South Africa 

to the Persian Gulf and India.

Type locality: Port Alfred, South Africa.

Other occurrences: Durban, Natal (Amsterdam Museum); 

Madagascar (?), Zanzibar (Paris Museum); Aden (Jousseaume); 

Persian Gulf (Fischer); Goa (U. S. National Museum).

Genus EONTIA MacNeil, n. gen.

Type species: Area ponderosa Say.

The separation of the Area ponderosa group fronr the 

Noetia reversa group necessitates the proposal oi a new 

generic name for the former. Eontia, an anagram of 

Noetia, is proposed.

Although related to the genus Sheldonella, Eontia 

differs from it in being less modioliform, with a betterdefined, often carinate umbonal ridge. The sculpture 

is coarser and less regular, and there is a greater break 

between the nealogic and adult sculpture. The 

characteristics of sculpture that distinguish Eontia 

from the Pacific genus, Noetia, are fully described on 

pages 2-8.

The genus Eontia is predominantly American. Only 

one species is known to occur elsewhere—Eontia olmi, 

in the lower Miocene of France. This-species not only 

occurs at a lower stratigraphic horizon than any of the 

American forms but is properly located to support my 

hypothesis that the genus is descended from the E-iropean Eocene genus Scapularca. Two sections of 

Eontia appear to exist in America—one the Caribbean 

and South American group of E. centrota, bisvlcata, and 

olssoni, and the other the North American group of 

E. incile and ponderosa. The first group is characterized by a well-developed anal ridge recalling Sheldordla 

maoica, and possibly its affinities are with Sheldonella. 

Because of their carinate umbonal ridge, however, these 

species are tentatively referred to Eontia.

A study of this group involves investigation of the migration of stocks and the development of geographic 

species and subspecies. Several varietal series are 

known, the end members of which are represented 

by purer strains elsewhere or at lower horizons. The 

question arises whether such conditions represent 

speciation or interbreeding. I believe that at least 

some preexisting species or varieties have intermingled 

to produce varietal series from which emerged a single,
12 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

more uniformly breeding species. In other words, so 

far as this group is concerned, hybridization is regarded 

as a factor that tends to limit diversification.

The North American group is represented in the 

collection of the United States National Museum by 

many specimens from numerous localities of each horizon at which the series occurs, and it is hoped that my 

interpretation of these forms will prove to be of value 

in correlating the stages of the upper Miocene and 

Pliocene of the Atlantic Coastal Plain.

EUROPEAN SPECIES

MIOCENE SPECIES

Eontia okeni (Mayer) MacNeil 

Plate 1, figures 9, 10

Area okeni Mayer, Jour, conchyliologie, vol. 6, p. 185, pi. 14,

figs. 7, 8, 1857. 

Dollfus and Dautzenberg, Soc. geol. France Me"m., Pale"ontologie, vol. 20, Me"m. 27, p. 337, pi. 27, figs. 19-27, 1913. 

Area (Anadara) okeni. Cossmann and Peyrot, Conchologie neoge"nique de 1'Aquitaine, tome 2, livr. 1, p. 162, pi. 9, figs.

5, 6, 1913.

Shell subrhomboidal, rounded anteriorly, produced 

posteroventrally; beaks high, situated between the 

center and the anterior third of the hinge line; umbonal 

region carinate; ribs alternately large and small, the 

larger often double posteriorly, ribs beaded by growth 

varices; cardinal area wide; ligament filling the anterior 

part of the area completely and extending almost an 

equal distance posteriorly, leaving a wide strip of the 

area bare posteriorly; teeth small and vertical or nearly 

obsolete centrally, inclined terminally, the posterior 

row slightly longer than the anterior row. (Emended 

description.)

Length 20 millimeters, height 13 millimeters, 

convexity 6.5 millimeters.

The vertical ligament elements in this species appear 

to be confined to the portion of the ligament anterior 

to the beaks. It thus differs in ligamental characters 

from Scapularca interposita, in which the ligament is 

more restricted anteriorly and the vertical elements are 

more evenly distributed, although occasionally specimens of that species are found in which the posterior 

grooves are very weak.

As all the species vary considerably, it is difficult to 

say which of the first American species most nearly 

resembles this European form, although perhaps specimens of E. centrota can be selected that appear more 

like it in shape. None of the published figures of the 

species show any indication of the anal ridge, however, 

and it may be that the resemblance of E. okeni to E. 

centrota and E. bisulcata is homeomorphic. Probably 

E. incile is its nearest American relative.

Distribution: Lower Miocene, Aquitanian and Burdigalian 

pf Aquitainej middle Miocene, Helvetian of Touraine, France.

SOUTH AMERICAN SPECIES

PLIOCENE SPECIES

Eontia centrota (Guppy) MacNeil

Plate 1, figures 11, 12

Area centrota Guppy, Sci. Assoc. Trinidad Proc., p. 175, 1867 

(Harris reprint, Bull. Am. Paleontology, vol. 8, no. 35, 

p. 54, 1921); Geol. Mag., London, new ser., vol. 1, pi. 18, 

fig. 23, 1874 (this plate was prepared for th^ 1867 paper 

but was not issued with it.)

Area (Noetia) centrota. Ball, Wagner Free Inst. Sci. Trans.,

vol. 3, pt. 4, p. 617,1898.

Maury, Bull. Am. Paleontology, vol. 10, no. 42, p. 38, pi. 8, 

figs. 10,12, 1925.

Shell subrhomboidal, wider posteriorly than anteriorly, somewhat produced and angulate posteroventrally; more modiolifonn in young stages; be^.ks moderately high, situated just posterior to the anterior third 

of the hinge line; umbonal ridge carinate but not much 

inflated; anal ridge well developed; ribs about 34, 

alternating with small interstitial ribs, the larger ribs 

frequently double posteriorly, both large and small 

ribs beaded by growth varices; ligament extending 

about as far posteriorly as anteriorly, leaving a wide 

strip of the area bare posteriorly; vertical ligament 

elements weak or absent posterior to the b?-aks; teeth 

small and vertical centrally, inclined tenrinally, the 

posterior row about twice as long as the arterior row. 

(Emended description.)

Lectotype (U.S.N.M. 496508), length 26 millimeters, 

height 16 millimeters, convexity 7 millimeters; paratypes (U.S.N.M. 115682).

Many specimens of this species are shorter and higher 

than the specimen from Guppy's type lot figured here. 

As in E. okeni, the vertical ligament elements are weak 

or absent posteriorly, but E. centrota differ? from that 

species in being more elongate along the hinge line and 

less produced posteroventrally, in having a loss elevated 

umbonal ridge but a well-developed anal ridg^ and more 

anterior beaks. The shell is less inflated, and the 

umbones do not appear to be as high.

The anal ridge on the posterior slope, which this 

species, E. bisulcata, and E. olssoni possess distinguishes 

them from the North American species of Eontia, and 

it may be that they are not as closely related to 

the North American species as the carinate umbonal 

ridge would indicate. The anal ridge is also found in 

Sheldonella maoica, and it remains for a fuller knowledge 

of the ancestry of E. centrota to show whether the South 

American group is related to the North American group 

or should be treated as a subgenus of Sheldonella.

Distribution: Upper Miocene, Springvale formation, Trinidad 

(Maury); Pliocene, Matura Bay deposits, eastern Trinidad. 

Type locality: Matura Bay, Trinidad.
SPECIES AND GENERA OF TERTIARY NOETINAE 13

RECENT SPECIES

Eontia bisulcata (Lamarck) MacNeil 

Plates 1, figures 15, 16

Area bisulcata Lamarck, Animaux sans Vertebres, vol. 6, p. 45, 

1819.

Area (Byssoarca) martinii Recluz, Jour, conchyliologie, vol. 3, p. 

409, pi. 12, figs. 3-5, 1852.

Area martinii. Dunker, Novitates conchologicae, Mollusca 

marina, p. 133, pi. 45, figs. 1-4, 1870.

Area centrota Guppy, Sci. Assoc. Trinidad Proc., vol. 2, pi. 3, 

figs. 4a, 4b, 1873 (Harris reprint, Bull. Am. Paleontology, 

vol. 8, no. 35, pi. 1, figs. 4a, 4b, 1921); Annals and Mag. 

Nat. History, 4th ser., vol. 15, p. 51, pi. 7, figs. 4a, 4b, 

1875 (except for the addition of a few lines, this paper is a 

reprint of the 1873 paper).

Area (Noetia?) martinii. Kobelt, Conchylien-Cabinet von Martini u. Chemnitz, Area, p. 60, pi. 17, figs. 7, 8, 1891.

Area (Noetia) martinii. Von Ihering, Jour, conchyliologie, vol. 

43, p. 214, 1895.

Area bisulcata. Dall, Wagner Free Inst. Sci. Trans., vol. 3, pt. 4, 

p. 617, 1898.

Area (Noetia) martini. Lamy, Jour, conchyliologie, vol. 55, 

p. 301, 1907.

Shell subrhomboidal, rounded anteriorly, angulate 

posteroventrally; beaks high, situated between the middle and anterior third of the hinge line; umbonal region 

carinate and inflated; anal ridge well developed; ribs 

about 33 or 34, alternating with small interstitial ribs, 

the large ribs wider but not showing any great tendency 

to be doubled posteriorly; both large and small ribs 

beaded by growth varices; ligament not as long posteriorly as anteriorly, leaving a wide area bare posteriorly, 

vertical elements coarse anteriorly but absent posterior 

to the beaks; teeth small and vertical centrally, inclined 

posteriorly,inclined or L-shaped anteriorly; the posterior 

row slightly longer. (Emended description.)

Figured specimen (U.S.N.M. 496509), length 23 millimeters, height 15 millimeters, convexity 7.5 millimeters; 

an eroded, larger specimen, length 30 millimeters, 

height 19.5 millimeters, convexity 10.5 millimeters.

This species with its high beaks and short hinge line 

has more the aspect of E. okeni than the more elongate 

specimens of E. centrota. It differs from E. okeni, 

however, in having a well-developed anal ridge. It has 

much coarser vertical ligament elements than E. 

centrota, is more inflated, and the ribs do not have as 

great a tendency to divide posteriorly. Future collections may show that these two species pass insensibly 

into one another.

Lamy expressed doubt concerning the suggestion of 

Dunker, Kobelt, and Dall that Area martinii and A. 

bisulcata were the same species, but his reason that a 

specimen of another species in the collection of Defrance 

was labeled "Area bisulcata var." in the hand of 

Lamarck does not prove his point. Bather, it seems 

to indicate that Lamarck recognized the specimen in 

Defrance's cabinet as different from his species.

Distribution: Recent, Caribbean and Atlantic coasts of South 

America from Colombia to Uruguay.

Eontia olssoni (Sheldon and Maury) MacNeil 

Plate 1, figmres 19, 20

Area sp. indet. o, Adams, Lyceum Nat. History New York

Annals, vol. 5, p. 488, 1852. 

Carpenter, Zool. Soc. London Proc., p. 364, 1863. 

Noetia olssoni Sheldon and Maury, Paleontographica americana, vol. 1, no. 4, p. 10, pi. 1, figs. 6, 9, 1922.

Shell subrhomboidal, as high anteriorly as poHeriorly, anterior rounded, posteroventral margin argulate; 

beaks of about medium height, situated at about the 

center of the hinge line; umbonal ridge carinate; anal 

ridge well developed; posterior slope deeply sweated 

between the two ridges, especially in young sheUs; ribs 

alternately large and small with a slight tendency for 

the larger ribs to become double posteriorly, ribs 

delicately beaded by growth varices; ligament nearly 

as long posteriorly as anteriorly; teeth small and vertical centrally, inclined terminally, rows subequal in 

length. (Emended description.)

Holotype (in Paleontological Research Institution, 

Ithaca, N. Y.), length 19 millimeters, height 11 millimeters, convexity 5 millimeters.

This species occurring in the Pacific is clearly a 

member of the E. centrota-bisulcata group but differs 

from the Recent Caribbean species in being longer 

posteriorly and in having more central beaks and nearly 

equal rows of teeth. Its vertical ligament grooves are 

finer, the posterior slope is more sulcated between the 

umbonal and anal ridges, and the ribs are finer and more 

delicately beaded.

A study of the Pacific genus Noetia and Central and 

South American faunas as a whole strongly suggests 

that there has been no free passage between the Pacific 

and Caribbean since Miocene time, so that the separation of this species from the Caribbean stock is probably 

not of very late date. It is easily distinguished from 

E. bisulcata, and it is not likely to be merely an introduced form of that species. This species should b°. compared with the Springvale Miocene form from Trinidad. 

If these two forms are related, the genus should be 

present in some of the upper Miocene or Pliocene beds 

of northern South America or Central America.

Distribution: Recent, Pacific coast of Panama, Negritos and 

Salinas, Peru (Olsson).

Type locality: Bucaru, Los Santos Province, Panama.

NORTH AMERICAN SPECIES

MIOCENE SPECIES

Eontia indie (Say) MacNeil 

Plate 1, figures 25-28, 30, 31

Area incile Say, Acad. Nat. Sci. Philadelphia Jour., 1st ser.,

vol. 4, p. 139, pi. 10, fig. 3, 1824.

Conrad, Fossils of the Tertiary formations, p. 16, pi. 2, fig. 1, 

1832; Fossils of the medial Tertiary, p. 56, pi. 29. fig. 5, 

1840. 

Area (Noetia) incile. Dall, Wagner Free Inst. Sci. Trans., vol. 3,

pt. 4, p. 632 (in part), 1898.

Sheldon, Paleontographica americana, vol. 1, no. 1, p. 25 

(in part), pi. 5, figs. 18-25, 1916.
14 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Shell subrhomboidal and elongate, anterior rounded, 

posterior usually emargin&te, angulate posteroventrally; hinge line of variable length, sometimes greater 

and sometimes less than the middle length of the shell; 

beaks high, situated at about the anterior quarter or 

fifth of the hinge line; umbonal ridge sharply rounded 

and moderately inflated; posterior slope with a median 

sulcus which is more pronounced the longer the hinge 

line; ribs about 27, alternating with'small interstitial 

ribs which may be obsolete in some specimens, the larger 

ribs tending to be double or irregularly divided posteriorly; ribs slightly beaded or roughened by growth 

varices, more beaded in young stages; ligament extending posteriorly about as far to twice as far as anteriorly, 

leaving a large part of the area bare posteriorly; vertical 

ligament elements absent posteriorly in young specimens but appearing weakly and irregularly posterior to 

the beaks in specimens about half grown; teeth numerous and mostly vertical, the terminal teeth inclined, 

anterior and posterior rows practically continuous, 

about four-fifths of the teeth posterior to the beaks. 

(Emended description.)

Figured specimens: C%ama-bearing bed (U.S.N.M. 

496510), length 22 millimeters, height 17.5 millimeters, 

convexity 8.5 millimeters; bed a (U.S.N.M. 496512), 

length 31 millimeters, height 20 millimeters, convexity 

10 millimeters; bed c or Crepidula bed (U.S.N.M. 

496513), length 36.5 millimeters, height 25.5 millimeters, 

convexity 12 millimeters; Crepidula, bed at Bellefield 

(U.S.N.M. 496517), length 39.5 millimeters, height 23 

millimeters, convexity 11 millimeters; bed/ (U.S.N.M. 

496511), length 45.5 millimeters, height 27 millimeters, 

convexity 13.5 millimeters.

The development of the posterior ligament elements 

in this species and its progeny is in contrast to the great 

rarity or absence of these structures in the E. centrotabisulcata group. Specimens of E. incite can be selected 

which approach E. centrota in shape but lack the anal 

ridge. In both E. centrota and the European species 

E. okeni the hinge line is always shorter than the greatest length of the shell, whereas in E. incite it is commonly 

equal to the greatest length and frequently is the region 

of the greatest length. The sculpture of E. incile is 

more irregular than that of E. centrota, and the ribs are 

less beaded. E. centrota is usually less inflated, and the 

young stages are more modioliform.

The specimen figured by Say, which he believed to 

have come from Maryland, is the short, inflated, longhinged type found in the lower part of zone 2 of the 

Yorktown formation, the C%amo-bearing bed at Grove 

Wharf and King's Mill Wharf on the James River, and 

in all probability Say's specimen came from there. 

This form grades into larger, longer, and less inflated 

specimens. In the upper part of the C%ama-bearing 

bed the more rotund variety, E. incile yorkensis, n. var., 

is found as the end member of a varietal series.

In the lowest bed at Yorktown, the Turritella-bea,rmg 

bed or bed a, which is probably equivalent to the next

higher bed above the C%ama-bearing bed, is found a 

medium-sized form which is similar to the more elongate 

type of the C%ama-bearing bed but which, on the average, has more central beaks than specimens from 

either the underlying or overlying beds. The short 

type is rare, and the variety yorkensis has not been 

found. In the next overlying zone, bed 6, the genus 

appears to be absent, at least at Yorktown, although 

considerable search was made for specimens.

The middle and upper beds at Yorktown, the 

Crepidvla-be&TUig bed, or bed c, and higher, contain 

a form which averages considerably larger than those 

in the Turritella- and CTwma-bearing beds, and some 

specimens approach the Duplin species E. trigintinaria 

in size. Considerable variation is displayed by this 

form from bed c, but it consists mostly of irregularity 

of shape and does not constitute a well-defined varietal 

series as in the C%ama-bearing bed. Most individuals 

from bed c are more elongate and have moro anterior 

beaks than the forms in bed a and thus compare less 

with the Duplin species E. trigintinaria than specimens 

from bed a in this respect. It may be that these robust 

forms should be considered a subspecies, but no definition except size and irregularity seems possible, and for 

the time being they will be left in E. incile, s. s It may 

be pointed out, however, that on the basis of varieties 

and size any collection containing a number of specimens can usually be assigned to its correct horizon.

A condition occurring in this species, the cause of 

which has not been determined, although it may be 

due to muscle parasites, is that of the raised or swollen 

muscle scars, especially anteriorly. Occasional specimens showing this condition are found in th<\ Chamabearing bed, and also in E. trigintinaria from the Carolinas, but if caused by parasites, it reached epidemic 

proportions at certain localities in the middle part of 

the Yorktown formation of Virginia. Specimens from 

the Crepidula-besbTUig bed at Yorktown, in a vrell 1 mile 

east of Wareham, Gloucester County, and at Bellefield, 

just below Felgates Creek on the York Eiver, are unaffected. In the continuous layer, bed /, immediately 

overlying the fragmental zone at Yorktown, and in 

what is probably the same zone at the site of tt.e colonial 

limekiln below Indian Field Creek, above Yorktown, 

every specimen has greatly swollen and deformed muscle 

scars. They are also found in specimens from Rushmere Wharf, on the James River; from a locality 2 miles 

below City Point, on the James River; from Petersburg; 

and from the Dismal Swamp.

Whether this condition is of any lateral extent and 

represents the same stratum throughout is uncertain. 

If the present zoning of the Yorktown formation 4 is 

correct, it occurs at a lower horizon along the James 

River than along the York River, and I corolude for 

the present, therefore,.that this is a diseased condition 

and not a genetic character.

* Mansfield, W. C., 16th Internat. Geol. Congress Guidebook 5, Chesapeake Bay 

region, p, 32,1932, and unpublished notes.
SPECIES AND GENERA OF TERTIARY NOETINAE 15

Dall and the Maryland Geological Survey reported 

E. incite in the Burns and Harris collection from the 

Choptank formation at Jones Wharf, Md. This was 

evidently an error, as the specimens of this species in 

the Burns and Harris collection in the United States 

National Museum are recorded in the locality cataldg 

as having come from Virginia and are like specimens 

from Rushmere Wharf in form and preservation. No 

collections from Maryland have contained any •specimens of Eontia, to my knowledge.

Distribution: Upper Miocene, zone 2, Yorktown formation, 

Virginia.

Type locality: Unknown, but the specimen figured by Say 

appears to be the type found in the CTmwa-bearing bed, the 

basal bed of zone 2.

Occurrence: This species occurs abundantly at localities too 

numerous to mention along the York River from a point below 

Yorktown to a point above Felgates Creek; in Gloucester 

County; along the James River from a point below Sinithfield 

to City Point; at Petersburg; and in southern Virginia at Sycamore Church on the Ifottoway River, Southampton County, 

U. S. G. S. 10216. It occurs with the variety E. incile yorkensis 

in the CTmraa-bearing bed in the York-James Peninsula, at 

Dinwiddie, and near Powcan, in King and Queen County, and 

with E. incile suffolkensis in the upper part of the Yorktown 

formation north of Smithfield, at Chuckatuck and Suffolk.

Eontia incile mansfleldi MacNeil, n. subsp.

Plate 1, figures 23, 24

Area (Noetia) incile. Mansfield, Florida Geol. Survey Bull. 8, 

p. 45, pi. 6, 1932.

Shell subrhomboidal and elongate, anterior rounded, 

posterior strongly emarginate, angulate anterodorsally, 

alate posterodorsally, angulate posteroventrally; beaks 

moderately high, situated at about the anterior fifth 

of the hinge line; umbonal ridge carinate and narrowly 

inflated; posterior slope deeply sulcated; ribs about 27; 

interstitial ribs small or absent, ribs beaded in young 

stages; ligament extending about as far posteriorly as 

anteriorly, but leaving a wide strip of the area bare 

posteriorly, vertical ligament elements rare or absent 

posterior to the beaks; teeth numerous and mostly) vertical, the posterior teeth slightly inclined, the anterior 

teeth L-shaped, anterior and posterior rows continuous, 

about four-fifths of the teeth posterior to the beaks.

Holotype (U.S.N.M: 371122), length 25.5 millimeters, 

height 15.5 millimeters, convexity 7.5 millimeters.

This species is well characterized by its alate posterior 

and pronounced sulcus. The figured holotype is the 

largest specimen known of this species but does not 

appear to be a full-grown adult. Occasional specimens 

of E. incile from Virginia and more commonly of E. 

trigintinaria from the Carolinas are found with a 

sub alate posterior, but never so pronounced nor of the 

constant character of the Florida subspecies.

If the present correlation of the Ecphora zone of the 

Choctawhatchee formation of Florida with zone 1 of 

the Yorktown formation is correct, E. incile mansfieldi 

is the earliest American occurrence of Eontia, the

145333—38———3

northern form making its appearance at the base cf the 

6%ama-bearing bed, the lowest horizon of zone 2 of the 

Yorktown formation. The possibility remains, however, that the Ecphora zone is equivalent to some part 

of zone 2 of the Yorktown formation.

Distribution: Upper Miocene, Ecphora zone, Choctawhftcb.ee 

formation, Florida.

Type locality: Jackson Bluff, Ocklocknee River, Leon County, 

Fla., U.S.G.S. 3423.

Eontia incile yorkensis MacNeil, n. var.6 

Plate 1, figures 34-36.

Area (Noetia) incile. Dall, Wagner Free Inst. Sci. Trans. vol. 3,

pt. 4, p. 632 (in part), 1898.

Sheldon, Paleontographica americana, vol. 1, no. 1, p. 25 

(in part), 1916.

Shell subrhomboidal to subovate, not much inflated, 

anterior rounded, posterior straight or broadly rounded, 

posteroventral margin rounded, not angulate; I saks 

high, situated at about the anterior third of the hinge 

line; umbonal ridge rounded and not well defined in 

adults; posterior slope narrow and moderately steep, 

sometimes with a shallow depression; ribs 26 to 30, 

averaging about 28, alternating with weak interstitial 

ribs, tending to be slightly double posteriorly; ribs 

slightly beaded in young stages; ligament over twi°e as 

long posteriorly as anteriorly, leaving a small strp of 

the area bare posteriorly, vertical elements appearing 

when the shell is about one-third grown; teeth numerous 

and mostly vertical, the posterior teeth slightly inclined 

and the anterior teeth tending to be L-shaped, anterior 

and posterior rows continuous.

Holotype (U.S.N.M. 496515), length 29.5 millimeters, 

height 23.5 millimeters, convexity 9.5 millimeters. 

Paratype (U.S.N.M. 496518).

Eontia incile yorkensis differs from the typical form 

in being less inflated, higher, and more rounded, with a 

broadly rounded ridge in adults. It has a more equilateral cardinal area tftian typical E. incile and a relatively larger ligament area. As in that species, the 

posterior ligament elements do not appear until the 

shell is one-third or more grown and remain weaker 

than the anterior ones ?tliroughout.

The variety has notlbeen found in the lowest part of 

the 6%ama-bearing bed^in the York-James Peninsula, 

but in the upper part of the (7/iama-bearing bed it occurs 

as the end member of a varietal series which grades into 

typical E. incile. In this area the variety is outnumbered by the more typical specimens, but farther north, 

at a locality about half a mile southwest of Powcan, 

King and Queen County, which is the northernmost 

outlier of the Yorktown formation known, it greatly 

outnumbers the typical form.

Distribution: Upper Miocene, upper part of the CTiawa-bearing 

bed, zone 2 of the Yorktown formation, Virginia.

s In this paper subspeciflc forms geographically or stratigraphically isolated from 

the typical form are made subspecies, whereas extreme forms that grade nto the 

typical form in the same bed are made varieties.
16 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Type locality: Upper part of the CTiama-bearing bed exposed 

in the fourth tributary on the south of Queen Creek, about 300 

to 400 feet south of the Yorktown-Williamsburg Parkway about 

\% miles east of Williamsburg, York County, Va., U.S.G.S. 

13817,

Other occurrences: Paratype, Dinwiddie, Dinwiddie County, 

U.S.G.S. 1623; about half a mile southwest of Powcan, King 

and Queen County, U.S.G.S. 8205; on the headwater of a 

branch of Garnett Creek, about 1 mile southwest of Miller's 

Tavern, King and Queen County, U.S.G.S. 8206.

Eontia incile suffolkensis MacNeil, n. var.

Plate 1, figure 29

Occurring with more or less typical specimens of 

E. incile in the upper part of the Yorktown formation 

of southern Virginia, the beds at Suffolk and their 

nearby equivalents, are occasional specimens of a 

variety which at first glance appears quite distinct. It 

is distinguished by its very sharp umbonal ridge and 

deep sulcus on the posterior slope. The hinge line is 

long, so that the shell is angulate both anterodorsally 

and posterodorsally. The beaks are high and strongly 

opisthogyrate, causing the posterior part of the cardinal 

area to appear very broad. The ribs are high and very 

well defined, perhaps more so anteriorly than in the 

typical form.

Holotype (U.S.N.M. 496514), length 36 millimeters, 

height 24 millimeters, convexity 13.5 millimeters.

The beds at Suffolk have been correlated with the 

Duplin marl of North Carolina, but the species of 

Eontia in them are quite distinct. This may be due 

primarily to a difference in faunal provinces, but the 

existence of beds equivalent to the Duplin marl near 

Franklin, Va., indicates that the Duplin marl may 

be-mostly younger as well. If anything, the young of 

the Duplin species more nearly resemble the middle 

Yorktown forms, particularly those occurring in the 

Turritella bed, or bed a, at Yorktown, than forms from 

the beds at Suffolk, and it may be that the two stocks 

became separated at that time and developed independently thereafter.

There is no evidence that the upper Yorktown stock 

in Virginia contributed anything to the Pliocene forms, 

and the supposition is that the latter were descended 

from Miocene forms farther south and that,the Virginia 

stock became extinct, possibly owing to a sudden cooling 

of the water in their province. The Yoldia bed that 

occupies the uppermost position in the shallow trough, 

a few miles upstream from Yorktown carries a distinctly 

cold-water fauna and contains no Eontias. This bed is 

probably the cold-water equivalent of Ebra^a-bearing 

beds farther south.

Distribution: Upper Miocene, upper part of the Yorktown 

formation; the beds at Suffolk and their equivalents and possibly , next underlying beds, Virginia. , i

Type locality: Highest bed at Rock Wharf, 4 miles north of 

Smithfield, Isle of Wight County, Va., U.S.G.S. 10207.

Other occurrences: One mile east of Chuckatuck, Nansemond 

County, U.S.G.S. 13826; Suffolk, Nansemond County, U.S.G.S. 

10201.

Eontia trigintinaria (Conrad) MacNeil . 

Plate 1, figures 32, 33, 37, 38; plate 2, figures 3, 4

Area incile. Tuomey and Holmes, Pleiocene fosnls of South

Carolina, p. 35, pi. 14, figs. 6, 7, 1857.

Emmons, North Carolina Geol. Survey Rept., p. 284, 1858. 

Anomolocardia trigintinaria Conrad, Acad. Nat. Sci. Philadelphia

Proc., vol. 14, pp. 289, 580, 1862.

Noetia protexta Conrad, Kerr's Geol. Rept. North Carolina, app. 

- A, p. 19, pi. 3, fig. 5, 1875.

Shell subrhomboidal, moderately, elongate, anterior 

rounded, posterior margin emarginate or nearly straight, 

angulate posteroventrally; beaks moderately high, situated at about the anterior third of the hinge line; 

umbonal ridge bluntly carinate, moderately inflated; 

posterior slope wide, somewhat sulcated; medial sulcus 

sometimes, weak; ribs 28 to 33, averaging about 31; 

large and usually alternating with smaller interstitial 

ribs, especially posteriorly; larger ribs double posteriorly 

and tending to divide anteriorly in full-grcwn adults, 

beaded in young stages; posterior part cf ligament 

about one and a half times as long as anterior part 

but relatively shorter in young shells, leaving a wide 

strip of the area bare posteriorly; vertical elements 

appearing posteriorly when about one-third grown 

and about evenly distributed along the length of the 

ligament in adults, the posterior grooves remaining 

mostly vertical, weaker than the anterior ones; teeth 

numerous and the terminal ones inclined, \ those at 

the anterior end tending to be L-shaped. (Emended 

description.)

Holotype in Philadelphia Academy of Natural 

Sciences. Figured specimen from South Carolina 

(U.S.N.M. 496583), length 52 millimeters, height 38 

millimeters, convexity 16 millimeters; specimen from 

Florida (U.S.N.M. 49652'!), length 34 millimeters, 

height 21 millimeters, convexity 10 millimeters.

This form appears to initiate "the subdivision of the 

anterior ribs, which in the foregoing forms remained 

undivided. It is considerably larger and relatively 

higher, and the beaks are more central and less opisthogyrate 'than in E. incile. >ft

Eontia trigintinaria probably represents a geographic 

subspecies derived from typical E. incile. The transition between E. incile and E. trigintinaria is not sharp, 

and specimen's from the lowest bed, bed a, at Yorktown 

and young specimens from the Duplin marl in Duplin 

County, N. ,C., cannot always be identified with certainty. This has already been discussed with reference 

to E. incile suffolkensis (p. 16). Full-grown specimens 

of E. trigintinaria, from1 the Carolinas are readily distinguishable from specimens from the Yc^ktown of 

Virginia, however.

The Cancellaria zone of the Choctawhatchee formation of western Florida contains a form thf.t is tentatively referred to Eontia trigintinaria because of the 

position of its beaks (pi. 1, figs. 32, 33), tut it may 

warrant a subspecific name. No specimens have been
SPECIES AND GENERA OF TERTIARY NOETINAE

thus far collected wlUch approach the Carolina form 

in size, so that this form might be compared quite as 

justifiably with specimens of E. incite from bed a at 

Yorktown. The remainder of the fauna iri'dicates a 

later age for the Cancellaria zone, however, so that this 

zone probably represents a faunal province in which 

the Eontias did not keep pace in evolution with those 

of provinces farther north. This alternative is plausible 

in view of the Florida Pliocene species discussed on 

page 20.

Noetia protexta Conrad is probably the end member of the varietal series which occurs in Greene 

County, N. C. (pi. 2, figs. 3, 4), and is placed in 

synonymy with E. trigintinaria, from which it cannot be 

distinguished.

Distribution: Upper Miocene, Duplin marl of North and South 

Carolina, and the Yorktown formation of North Carolina and 

Virginia; Cancellaria zone, Choctawhatchee formation, -western 

Florida.

Type locality: "South Carolina."

Occurrence: The Biggs farm, 3 miles west of Franklin, Southampton County, Va., and: many localities in the Carolinas, some 

of the most important of which are Natural Well, 2 miles southwest of Magnolia, Duplin County, .N. C., U.S.G.S. 2279, 2280, 

13827; Rock Landing, Neuse River, 16 miles above New, Bern, 

Craven County, N. C., U.S.G.S. 10898; Shell Branch near 

Darlington Courthouse, Darlington, S. C., U.S.G.S. 2024; 

Davis Landing, Pee Dee River, 6% miles northwest of the mouth 

of Lynches River, Florence County, S. C., U.S.G.S. 5302; 

Muldrow estate, 0.7 mile northeast of Brick Church on Black 

River Road 5 miles southeast of Mayesville, Sumter County, 

S. C., U.S.G.S. 4000. At Sullivan's marl pits, 8 miles east of 

Snow Hill, Greene County, N. C., U.S.G.S. 2298, and at Darlington Courthouse it occurs with the variety E. trigintinaria filosa. 

In Florida forms referred to this species occur at the borrow pit, 

Jackson Bluff, Ochlockonee River, Leon County, U.S.G.S. 

11732; and 1 mile west of Holland post office, Leon County, 

U.S.G.S. 4993.

Eontia trigintinaria filosa (Conrad) MacNeil

Plate 2, figures 1, 2

Noetia flosa Conrad, Kerr's Geol. Rept. North Carolina, app. A,

p. 20, pi. 4, fig. 3, 1875. 

Area (Noetia) limuLtt var. filosa. Dall, Wagner Free last. Sci.

Trans., vol. 3, pt. 4, p. 632, 1898. 

Sheldon, Paleontographica americana, vol. 1, no. 1, p. 27

(in part), 1916.

Shell subrhomboidal, inflated, medially depressed, 

varying from moderately elongate to medium length, 

rounded anteriorly, emarginate to nearly straight 

posteriorly, bluntly angulate posteroventrally; breaks 

high, situated between the anterior third and center 

of the hinge line; umbonal ridge carinate in younger 

stages, more rounded in adults; posterior slope sulcated, 

varying from moderately expanded to moderately 

steep; ribs 29 to 35, averaging about 32, usually alternating with smaller interstitial ribs, larger ribs double 

posteriorly and tending to be double anteriorly in

adults, beaded in younger stages; ligament about trace 

as long posteriorly as anteriorly in adults but less pro^ 

duced posteriorly in juveniles, leaving a moderately 

jvide strip of the area bare posteriorly, vertical ligament 

elements appearing posteriorly when.about one-third 

grown, evenly distributed but weaker than the anterior 

grooves in adults; teeth nearly vertical centrally, inclined 

terminally. (Emended description.)

Figured specimen (neotype) (U.S.N.M. 496516), 

length 45 millimeters, height 33.5 millimeters, convexity 

14.5 millimeters. The specimen figured by Conrad is 

a juvenile. i

In Greene County, N. C., a varietal series is found 

which compares with E. trigintinaria on the one band 

and approaches a more northern form, E. oarolinensis 

(Conrad), on the other hand. Conrad gave no locality 

for his species Noetia protexta and Noetia Jilosa, and the 

types have probably been lost, but they conform perfectly to the extremes of this series and presumably 

came from this region. As all subsequent references 

to this form have been based on Ball's interpretation of 

it, it seems desirable to designate one of the specirr"?.ns 

which Dall had before him as neotype and accept its 

locality as the type locality. .

Dall considered E. Jilosa a variety of the Pliocene 

species E. limida, and Miss Sheldon expanded it to 

include all the Pliocene, forms except the Florida variety, 

E. limvla platyura (Dall). The dissimilarity between 

filosa and the Pliocene species, as well as its gradation 

into a typical Miocene species, leads me to regard Jilosa 

as little more than an extreme variety of E. trigintinaria, 

Although the name Jilosa is retained as vindicating a 

variety, there does not appear to be any good reason 

for perpetuating all the names which Conrad appUed 

to this series, especially as the Noetia protexta end is 

not definitely separable from E*- tvigintwaria. < E,. 

trigintinaria occurs abundantly at the type locality and 

is known elsewhere only at Darlington, S. C., where it 

is apparently rare.

Distribution: Upper Miocene, upper 'beds of the Yorktown 

formation in Greene County, N. C. • < -

Type locality: Sullivan'g marl pits, 8 miles east of Snow HilJ, 

Greene County, N. C., U.S.G.S. 2298. , _,.,

Other occurrences: Shell Branch near Darlington courthouse, 

Darlington, S. C., U.S.G:S. 2024.

Eontia carolinensis (Conrad) MacNeil > 

Plate 2, figures 5, 6 ' : '

Noetia ponderosa Say var. carolinensis Conrad, Acad. Nat. Sci 

Philadelphia Proc., vol. 14, p. 290, 1862; Noetia (Area) 

carolinensis, p. 580 [not Area carolinensis Wagner, 1847].

Area carolinensis Heilprin, Acad. Nat. Sci. Philadelphia Px>c., 

vol. 33, p. 450,18,81.

Area (Noetia) limula var. Jilosa. Dall, Wagner Free Inst. Sci.

Trans., vol. 3, pt. 4, p. 632, 1898.

Sheldon, Paleontographica americana, vol. 1, no. 1, p. 27 

(in part), 1916.
18 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Shell subrhomboidal or subtrigonal, inflated, varying 

from moderately elongate to medium length, rounded 

anteriorly, slightly emarginate to broadly rounded posteriorly, bluntly angulate to rounded postero-ventrally; 

beaks high, situated between the anterior third and 

center of the hinge line; umbonal ridge carinate in 

younger stages, more rounded in adults; posterior slope 

varying from expanded to moderately so, rarely sulcated; 

ribs 31 to 36, averaging about 33, usually alternating 

with smaller interstitial ribs, larger ribs double posteriorly and tending to be double anteriorly in adults, 

ribs beaded in younger stages; ligament occupying 

nearly the entire cardinal area in adults but leaving a 

wider strip of the area bare posteriorly in juveniles, 

vertical ligament elements appearing irregularly posteriorly when about one-quarter or one-third grown but 

stronger and evenly distributed in adults; teeth nearly 

vertical centrally, inclined terminally.

Lectotype in Philadelphia Academy of Natural 

Sciences. The largest of the three cotypes is here so 

designated. Figured specimen (U.S.N.M. 496519), 

length 48 millimeters, height 40 millimeters, convexity 17.5 millimeters.

This species, found in the uppermost Miocene in the 

vicinity of the Chowan River, differs from E. trigintinaria jilosa in being larger, averaging one or two more 

ribs, rarely, if ever, having the minimum number found 

in Jilosa, and in being rounded posteriorly. The sulcus 

on the posterior slope and emarginate posterior always 

found in Jilosa are almost never found in E. carolinensis. 

Furthermore, E. carolinensis exhibits very little variation in the lower part of the bluffs along the Chowan 

River or at Tar Ferry on Wicocon Creek.

In the uppermost bed at Colerain Landing, however, 

some variations occur, consisting principally of a more 

quadrate form and greater subdivision of the anterior 

ribs, which forecasts some of the North Carolina Pliocene 

forms. This may represent an intermingling with E. 

lumberensis, the next species to be described.

There can be but little doubt that E. carolinensis is 

closely related to E. trigintinaria Jilosa, but whether the 

latter represents the production of E. carolinensis from 

E. trigintinaria or is a hybrid of two distinct strains is 

still uncertain. The rounded umbonal region and full 

ligament of E. carolinensis recalls, to a certain extent, 

the Yorjttown form E. incite yorkensis, and it may be 

that the latter was perpetuated, but there is no record 

of the persistence of this strain above the horizon of the 

upper Chama-bearmg bed.

Distribution: Upper Miocene, uppermost part of the Yorktown formation in the vicinity of the Chowan River, N. C.

Type locality: If Conrad's locality, "Dauphin County, N. C.", 

is a mistake for Duplin County, it is an error, as this form is not 

found in Duplin County. The middle bed at Colerain Landing, 

Bertie County, N. C. (U.S.G.S. 13829), might be regarded as 

the type locality.

Other occurrences: Half a mile below Mount Gould Landing, 

Bertie County, N. C., U.S.G.S. 11999; Tar Landing Ferry, 

Wicocon Creek, 1 mile north of Harrellsville', Hertford County. 

N. C., U.S.G.S. 13830.

Eontia lumberensis MacNeil, n. sp.

Plate 2, figures 7, 8

Shell subrhomboidal, thickened, moderately elongate 

and inflated, rounded anteriorly, subemarginate or 

straight posteriorly, angulate posteroventrally; beaks 

moderately high, situated just anterior of the center 

of the hinge line; umbonal ridge carinate; posterior 

slope flat or somewhat sulcated, moderately steep; 

ribs 30 to 33, averaging 31, alternating with small 

interstitial ribs, especially posteriorly, the larger ribs 

double or irregularly divided posteriorly g,nd tending 

to become double anteriorly; ribs beaded in young 

stages; ligament about as long or slightly longer 

posteriorly than anteriorly, vertical elements absent 

posteriorly but appearing when about one-third grown; 

a moderately wide strip of the area left bare posteriorly; 

teeth vertical centrally, inclined posteriori;^ L-shaped 

anteriorly.

Holotype (U.S.N.M. 496520), length 39 millimeters, 

height 28 millimeters, convexity S13 millimeters.

This species differs from E. triaintinaria in being relatively shorter and higher and in having more central 

beaks and a more equilateral ligament arex It more 

closely resembles the Pliocene forms, particularly E. 

variabilis, than any other Miocene species, and the 

young of E. variabilis cannot be separated from it with 

certainty. All the largest specimens are o* about the 

same size, however, and the shells are thickened, more so 

than is common in shells of the same size in other species. 

E. lumberensis, therefore, is probably a smaller shell than 

the Pliocene forms which it most resembles. Were it 

not.for the fact that E. lumberensis is associated with 

an undoubted Miocene fauna it would1 most certainly 

be regarded as a Pliocene species.

Distribution: Upper Miocene, upper part of the Duplin marl 

in the vicinity of Lumberton and Fairmoht, Rot^son County, 

N.-C.

Type locality: 4 miles southeast of Lumbermen, Robeson 

County, N. C., U.S.G.S. 11824.

Other occurrences: 2}i miles east of Fairmort, U. S. G. S. 

11832; 2 miles east of Fairmont, U.S.G.S. 13828a; road cut just 

north of bridge over Lumber River, 2 miles southeast of 

Lumberton, U.S.G.S. 13828.
SPECIES AND GENERA OF TERTIARY NOETINAE

Correlation of uppermost Miocene Eontia-bearing beds in the Carolinas and Virginia

19

o3

a

.g

3

Q

South Carolina

'

Beds in the 

vicinity of 

Darlington and 

Mayesville. 6

North Carolina

Southern

Beds around 

Lumber-ton."

South central North central

Beds in Duplin 

and Sampson 

Counties. 6

C! .2-4J

«-l

O

C! 

O

«H

Highest beds in 

Greene County. rf

Beds in Pitt, Greene, 

and Craven 

Counties. 6

'

Northern

Beds in the vicinity 

of the Chowan 

River. 6

'

'

Virginia

Beds near 

Franklin.*

?

Beds at 

Suffolk/

0 Carries E. lumberensis. 

1 Carries E. carolinensis. 

« Carries E. trigintinaria.

d Carries E. trigintinaria and variety ftlosa.

' Carry E. trigintinaria.

Variety filosa at Darlington. f Carries E. incite and variety suffolkensis.

The lowest questioned beds in central and northern North Carolina may be mostly older than those at Suflolk.

PLIOCENE SPECIES

Eontia limula (Conrad) MacNeil

Plate 2, figure 9

Area limula Conrad, Fossils of the Tertiary formations, pi. 15,

pi. 1, fig. 1, 1832; Fossils of the medial Tertiary, p. 60,

pi. 31, fig. 3, 1845. 

Noetia (Area) limula. Conrad, Acad. Nat. Sci. Philadelphia

Proc., vol. 14, p. 580, 1862. 

Area (Noetia} limula. Dall, Wagner Free Inst. Sci. Trans., vol.

3, pt. 4, p. 631 (in part), 1898. 

Area (Noetia) limula var. filosa. Sheldon, Palaeontographica

americana, vol. 1, no. 1, p. 26 (in part), pi. 5, fig. 26, 1916.

Shell subrhomboidal and elongate, rounded anteriorly, 

posteroventral region produced and subangulate in 

young shells, but rounded in adults; beaks high and 

situated at about the center of the hinge line but at 

about the anterior third of the shell; umbonal ridge 

carinate and moderately inflated in juveniles but becoming broadly rounded in adults; ribs 29 to 33, averaging about 31, usually alternating with small interstitial 

threads; ribs usually double all around, the posterior 

ribs so much so that a small riblet may appear in the 

furrow between the two parts; ribs in juveniles single 

and beaded anteriorly; ligament area nearly symmetrical and covering the cardinal area except for a 

narrow strip posteriorly, vertical ligament elements 

appearing posteriorly when about one-quarter grown; 

teeth small and vertical centrally, inclined posteriorly 

and often L-shaped anteriorly, the posterior row slightly 

longer. (Emended description.)

Figured specimen (topotype?) (U.S.N.M., 496522), 

length 76 millimeters, height 52 millimeters, convexity 21.5 millimeters.

This species is considerably larger and more produced 

posteriorly than the uppermost Miocene form, E. carolinensis. The ribs are fewer and become double at a

much earlier stage in shell growth. The vertical ligament elements appear posterior to the beaks at an earlier 

age and in adults are distributed along the entire length 

of the ligament.

Eontia limula is a remarkably constant species, showing little or no variation. Its occurrence is restricted to 

the Croatan sand of northeastern North Carolina. It 

differs from E. variabilis, the form occurring in the 

Waccamaw formation, in both form and variability, the 

nature of which is discussed under that species. Eontia 

limula is probably directly descended from E. carolinensis.

The Croatan sand of United States Geological Sur^&y 

usage is of Pliocene age. Dall's original material from 

the "Croatan beds" is a mixture of Pliocene and Pleistocene and was probably collected along the river for a 

distance of several miles. No Pliocene is exposed in the 

bluffs of the Neuse Kiver nearest Croatan itself, so that 

the type section for the Croatan sand cannot be recognized there. Perhaps the best section of the Pliocene 

in this region is exposed on the property of Mr. Hastings 

on the right bank of the Neuse Kiver 2 miles beT ow 

James City, Craven County, N. C., and this miglit be 

regarded as the type section of the Croatan sand. This 

is probably the exact spot from which a number of 

species described by Conrad as from "New Berne" were 

obtained. Of the specimens figured by Miss Sheldon as 

from the "Croatan beds" only one, that shown on her 

plate 5, figure 26, is the typical Pliocene species E. limula. All the others are from the Pleistocene and are 

discussed under the species E. palmer ae, n. sp., described 

below.

Distribution: Pliocene; Croatan sand, Craven and Onflow 

Counties, N. C.

Type locality: "New Berne, N. C." Conrad's locality is 

probably the bluff on the property of Mr. Hastings, 2 rriles 

below James City, Craven County, N. C., U.S.G.S. 13812.
20 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Other occurrences: Brices Creek about \% miles west of 

Croatan station, Craven County, N. C.; marl pits on the farm 

of Jackson Jones on the north side of Grants Creek on the old 

road from Jacksonville to Maysville, about 5 miles west of Silverdale, Onslow County, N. C., U.S.G.S.; 11996.

Doubt-ful identifications: Some specimens found near Melbourne, Fla., resemble this species and are discussed under E. 

variabilis.

Eontia tillensis MacNeil, n. sp.

Plate 2, figure 10

Shell subrhomboidal, moderately inflated, medium to 

moderately elongate, rounded anteriorly, usually 

broadly rounded posteriorly but occasionally slightly 

emarginate, more sharply rounded posteroventrally; 

valves thin; beaks moderately high, situated at about 

the center of the hinge line; umbonal ridge well defined 

in young stages but rounded in adults; medial sulcus 

usually present but not well defined; posterior slope 

varying from slightly sulcate to broadly rounded; ribs 

29 to 32, averaging about 31, double or irregularly 

divided posteriorly, usually double anteriorly; ligament usually longer anteriorly than posteriorly, a 

moderately wide strip of the area left bare posteriorly, 

vertical elements weak or absent posteriorly in young 

stages but usually well developed in full-grown adults; 

teeth vertical centrally, inclined posteriorly, L-shaped 

anteriorly.

Holotype (U.S.N.M. 496527), length 54 millimeters, 

height 45 millimeters, convexity 19.5 millimeters.

This species differs from E. limula in being considerably shorter and more inflated, with a less developed 

medial sulcus and a more sharply rounded posteroventral margin. Eontia tillensis resembles the Miocene 

form E. carolinensis, more so than E. limula. Some 

specimens are emarginate posteriorly, suggesting relationship with E. trigintinaria jilosa, and the species 

may be descended from that form.

Eontia tillensis is typically developed in northeastern 

South Carolina, being known from Tillys Lake and the 

Intracoastal Waterway 3 miles west-southwest of 

Little River. At Tillys Lake it occurs with individuals 

resembling E. variabilis, but so far no specimens 

referable to E. tillensis have been seen from the region 

of the Cape Fear River in North Carolina, where E. 

variabilis predominates. E. tillensis may represent 

one of the purer strains that contributed to the E. 

variabilis complex, but it also appears to be related 

to the Pleistocene E. palmerae, n. sp., so that although 

it may intergrade with E. variabilis at some localities, 

it seems best not to consider it a variety of that species.

Distribution: Pliocene, Waccamaw formation, northeastern 

South Carolina.

Type locality: Tillys Lake, Waccamaw River, Horry County, 

S. C., U.S.G.S. 4400.

- Other occurrences: Intracoastal Waterway 3 miles westsouthwest of Little River, Horry County, S. C., U.S.G.S. 13377. 

The Pleistocene species is present in great numbers at this 

locality, but only one specimen with the Pliocene pmestgne 

matrix.adhering was obtained from the dump.

Eontia caloosana MacNeil, n. sp.

Plate 3, figure 4

Shell subrhomboidal and elongate, usually broadly 

rounded anteriorly and posteriorly, sharp] v rounded 

posteroventrally, inflated between the medial sulcus and 

the ridge; beaks moderately high, situated at about the 

anterior third of the hinge line; hinge line long, making 

the shell subangulate at both ends; umtonal ridge 

moderately well defined; posterior slope expanded; ribs 

31 to 39, averaging about 34, double posteriorly, but 

rarely so anteriorly, interstitial ribs usualK well developed and stronger anteriorly; anterior ribs tending 

to be less elevated in adults; ligament abont one-half 

to twice as long posteriorly, leaving a wide strip of the 

area bare posteriorly; vertical ligament elements appearing posteriorly when about one-third grown and 

well developed thereafter; teeth vertical centrally, 

inclined posteriorly, L-shaped anteriorly.

Holotype (U. S. N. M. 496531), length 57 millimeters, 

height 42 millimeters, convexity 18 millimeters.

Eontia caloosana is not particularly varied in shape, 

but the number of ribs shows a considerable range, the 

maximum being greater than in any other species of the 

Atlantic group. It differs from E. limula, in being 

smaller, with a much longer hinge line and more anterior beaks. The ligament is considerably longer 

posteriorly, and the anterior ribs rarely show any 

tendency to divide. The shell is more angulate at the 

dorsal extremities.

Certain features of this species, such as its long 

hinge line, distinguish it from other Pliocene types. 

It may be that E. caloosana, was isolated in development from E. trigintinaria at the southern extent of its 

range, possibly from the form occurring in the Cancellaria zone of the Chocta^vhatchee formation.

This species is believed to occur at a lov^er horizon 

than E. variabilis clewistonensis from the same area.

Distribution: Pliocene, Caloosahatoh.ee marl ner.r Clewiston, 

Fla.

Type locality: 6 miles northwest of Clewiston, Hendry 

County, Fla., U.S.G.S. 13834.

Eontia variabilis MacNeil, n. sp.

Plate 2, figures 12-16

Area (Noetia) limula. Ball, Wagner Free Inst. Scf. Trans., vol.

3, pt. 4, p. 631 (in part), 1898. 

Area (Noelia) limula var. filosa. Sheldon, Paleontographica

americana, v.. 1, no. 1, p. 26 (in part), pi. 6, fks. 1, 2, 1916.

Shell subrhomboidal, moderately elongate to elongate, 

rounded anteriorly, angulate to sharply rounded posteroYentrally; medial sulcus present in longer individuals; beaks high, situatedi just anterior of the center 

of the hinge line but in longer individuals being more 

nearly at the anterior third of the shell; umbonal ridge 

well jdefined, often carinate but more commonly sharply 

rounded; posterior slope rarely sulcated; riH 28 to 33,
SPECIES AND GENERA OF TERTIARY NOETINAE 21

averaging about 31, double or irregularly divided posteriorly, single and rounded to double anteriorly; 

interstitial ribs frequently absent medially; ribs somewhat beaded in young stages; ligament about as long 

posteriorly as anteriorly, leaving a moderately wide 

strip of the area bare posteriorly; posterior vertical 

elements variable in strength and time of appearance, 

but generally well developed in adults; teeth vertical 

centrally, inclined posteriorly, L-shaped anteriorly.

Holotype (U.S.N.M. 496524), length 67 millimeters, 

height 49 milHmeters, convexity 23.5 millimeters. Paratype (U.S.N.M. 496525), length 55 millimeters, height 

37.5 millimeters, convexity 14.5 millimeters; paratypes 

(U.S.N.M. 496578, 496579).

In striking contrast to E. limula, E. variabilis is 

is marked by great irregularity in form. The umbonal 

ridge is never so broad and perfectly rounded, tending 

more often to be subcarinate, and the shell is less 

elongate posteriorly and relatively higher in most 

individuals. E. variabilis is found in typical form along 

the Cape Fear Biver in North Carolina, but varieties 

that appear quite distinct are met at the extremities of 

its range in this region. At Walkers Bluff, the locality 

farthest inland at which it has been found, a form having 

a sharp umbonal ridge and long hinge line occurs which 

resembles the Miocene form E. trigintinaria. A short, 

subquadrate type from this locality is named as a 

variety, E. variabilis quadmta, and resembles the 

Miocene species E. lumberensis.

Farther east, at Neills Eddy Landing, near Acme, 

and at Wilmington,7 a larger, less carinate form occurs, 

some specimens of which approach E. limula but are 

easily separated from it on the basis of irregularity. A 

specimen near the middle of this varietal series is taken 

to represent typical E. variabilis, which is probably a 

hybrid of the more western stock and E. limula and 

possibly E. tUlensis, although no typical specimens of 

either of these species have been found in this region.

E. variabilis differs from E. tillensis hi being less 

inflated, with a less rounded umbonal ridge and a thicker 

shell. The doubling of the anterior ribs is less uniform 

and advanced. E. variabilis has a shorter hinge line 

than E. caloosana, giving the shell a less angulate 

appearance at the dorsal extremities. It is considerably 

less elongate posteriorly and broader anteriorly, with 

more, central beaks and a shorter ligament.

Fairly typical specimens of E, variabilis have been 

dredged from Pliocene deposits hi the Brunswick Biver 

at Brunswick, Ga. The Caloosahatchee marl of eastcentral Florida around De Land and De Leon Springs 

contains a varietal series that more nearly conforms 

with that of typical E. variabilis in North Carolina but

7 The abundantly fossiliferous marl encountered in building and sewer Construction 

in Wilmington, N. C., was considered by Ball to>be of Miocene age. W. C. Mansfield 

recently reidentifled this material to verify conclusions reached by me as to its Pliocene 

age, and reported that at1 least some of the material appears to be undoubtedly Pliocene (Jour. Paleontology, vol. 10, no. 7, p. 668, 1936). Very typical specimens of 

Eontia variabilis indicate that the Pliocene beds underlying Wilmington are to be 

referred to the Waccamaw formation.

! may be of somewhat different composition. Some individuals in this series appear to be dwarfs and are" characterized by short shells, high umbonal ridges, and very 

little inflated anteriors, resembling E. platyurdj, horn 

southwestern Florida. Although a large collection is 

at hand, certain common varieties of typical E. platwura 

appear to be absent. Specimens which can be matched 

perfectly with specimens from North Carolina 1 ave 

been obtained near Clewiston, Fla., at a horizon that 

is probably above that of E. caloosana.

Some specimens dredged from a canal near Melbourne, 'Fla., approach specimens of E. limula from 

Onslow County, N. C., more closely than any known 

specimens of #. variabilis from the Cape Fear region of 

North Carolina. This might be taken as evidence that 

while E. limula contributed to the E. variabilis complex 

in North Carolina and was smothered up by it in ^hat 

region, it migrated as a less contaminated strain to 

Florida and participated in the E. variabilis flux in that 

region as well.

It appears certain that E. variabilis is a hybrid 

species. Its varieties include Miocene as well as truebreeding Pliocene types, and at some localities there is 

clear evidence of hybrid vigor. An inescapable fact is 

that from a large number of homogeneous species, 

varietal series, and local varieties there has evolved the 

consistent, long-ranging Recent species E.ponderosa. It 

is improbable, and the evidence is unsupporting, that 

E. ponderosa represents only a single surviving strari of 

this complex, and I therefore conclude from the role 

that E. variabilis must have played in the process that 

E. variabilis is polyphyletic but should be considered a 

unit, inasmuch as it represents the bringing together of 

related but diverse forms. (See p. 25.)

, Distribution: Pliocene, Waccamaw formation of North Carolina and South Carolina (?); Pliocene of Brunswick, Ga.; Ciloosahatchee marl of east-central Florida.

Type locality: Neills Eddy Landing, 5 miles northeart of 

Acme, Columbus County, N. C., U.S.G.S. 4276.

Other occurrences: Paratype, Walkers Bluff, 18 miles eastsoutheast of Elizabethtown, Bladen County, N. C., TJ.S.G.S. 

,11817; North shore of Lake Waccamaw, Columbus County, 

N. C., U.S.G.S. 13379; paratypes, Wilmington, N. C., U.S. 

G.S. 6104, 2295. Upper Pliocene horizon 6 miles northwest of 

Clewiston, Hendry County, Fla., U.S.G.S. 13834.

Doubtful identifications: 3% miles west of i Melbourne, Brevard 

County, Fla., U.S.G.S. 11140; Fellsmere, St. Lucie County, 

Fla. These specimens appear to be closely related to E. limula. 

Half a mile south of De Land, Volusia County, Fla.; just south 

of the airport at De Leon Springs, Volusia County, Fla., U.S.G.S. 

13832. A specimen obtained from a marl pit 1 mile north of 

Bermont, Charlotte County, Fla., U.S.G.S. "13835, is discussed 

'under E. platyura.

Eontia variabilis quadrata MacNeil, n. var.

Plate 2, figure 11

: This form is the end member of the varietal series 

'occurring at the Walkers Bluff locality on the Cape 

Fear Kiver, N. C., and grades into the typical form 

through the long-hinged, carinate type figured *\s a
22 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

paratype (pi. 2, fig. 15). Occasional specimens referable 

to it are found farther east, but at the type locality it 

may constitute as many as a fifth of the individuals. 

It resembles the Miocene species.E. lumberensis.

This variety is characterized by its short posterior 

end and carinate umbonal ridge. The shell is angulate 

posteroventrally, and the posterior margin is nearly 

straight. The disk is inflated without a medial sulcus. 

The number of ribs varies from 25 to 31, averaging 

28 or 29, so that it has fewer ribs than is typical for the 

species.

Holotype (U.S.N.M. 496523), length 51.5 millimeters, height 43 millimeters, convexity 19.5 millimeters.

Distribution: Pliocene, Waccamaw formation,*North Carolina.

Type locality: Walkers Bluff, Cape Fear River, 18 miles eastsoutheast of Elizabethtown, Bladen County, N. C., U.S.G.S. 

11817.

Eontia variabilis clewistonensis MacNeil, n. var.

Plate 3, figure 5.

Shell subquadrate to subovate, inflated, rounded anteriorly and ventrally, straight to broadly rounded posteriorly; beaks moderately high, situated at about the 

center of the hinge line; umbonal ridge well defined in 

young stages but of less prominence than the inflated 

medial area in adults; posterior slope broad and nearly 

flat, but in some specimens an anal ridge is developed; 

ribs 29 to 35, averaging about 33, double posteriorly 

but usually single and rounded anteriorly; interstitial 

ribs usually well developed, heavier anteriorly; ligament of about equal length anteriorly and posteriorly 

but in very large shells somewhat longer posteriorly, 

filling the cardinal area except for a strip of decreasing 

width posteriorly; vertical elements weak or absent 

posteriorly until about one-third or half grown but well 

developed thereafter; teeth vertical centrally, inclined 

posteriorly, L-shaped anteriorly.

Holotype (U.S.N.M. 496532), length 51.5 millimeters, height 47 millimeters, convexity 20 millimeters.

Eontia variabilis clewistonensis is characterized by its 

rotund outline, inflated disk and broadly rounded posteroventral margin. It is the end member of a varietal 

series that grades into more elongate, subrhomboidal 

individuals of E. variabilis.

The beds at the type locality of this variety are not 

exposed, the material having been thrown out by the 

dredge in the construction of the hurricane dike on the 

south shore of Lake Okeechobee. Specimens of Eontia 

from this locality appear to have come from two beds, 

to judge from their form and preservation. The more 

elongate form described as E. caloosana has its shells 

bleached and opaque, whereas the shells of the E. variabilis type are gray and glassy and are supposedly from 

a higher bed. This variety may be a hybrid of E. variabilis and E. caloosana.

Distribution: Pliocene, Caloosahatchee marl, south-central 

Florida.

Type locality: Six miles northwest of Clewiston, Hendry 

County, Fla., U.S.G.S. 13834.

Eontia platyura (Ball) MacNeil

Plate 3, figures 1-3

Area (Noeiid) limula var. platyura Dall, Wagner Fr^e Inst. Sci.

Trans., vol. 3, pt. 4, p. 632, 1898.

Sheldon, Palaeontographica americana, vol. 1, no. 1, p. 26, 

1916.

Shell subrhomboidal, rounded anteriorly, often angulate anterodorsally, broadly rounded to slightly emarginate posteriorly, sharply rounded to angulate posteroventrally; posterodorsal region rounded to subalate, 

sometimes forming an angle of nearly 90°; b°-aks high, 

situated between the center and anterior third of the 

hinge line; umbonal ridge sharply rounded and moderately inflated; posterior slope expanded to rioderately 

steep; medial sulcus weak; ribs 29 to 33, averaging 

• about 31, usually alternating with small interstitial riblets; ribs double posteriorly but variable in this respect 

anteriorly, beaded in young stages, anterior ribs frequently tending to be less elevated or leve? with the 

interspaces in adults; ligament usually shorter posteriorly than anteriorly except in very large individuals, 

leaving a wide strip of the cardinal area bare posteriorly; posterior vertical ligament elements weak and 

irregular in shells one-third to one-half grown, but well 

developed thereafter; teeth vertical centrally, inclined 

posteriorly, L-shaped anteriorly, the posterior row 

slightly longer. (Emended description.)

Lectotype (U.S.N.M. 496529), length 46 irillimeters, 

height 36 millimeters, convexity 15 millimeters. Paratype (U.S.N.M. 496528), length 55.5 millimeters, height 

43 millimeters, convexity 17.5 millimeters. Paratype 

(U.S.N.M. 496530), length 64.5 millimeters, height 45 

millimeters, convexity l&TJ&llimeters.

The specimens on which Dall based the "variety" 

platyura are extreme or even abnormal shell ^ but the 

name is available for the varietal series which occurs 

in the Caloosahatchee marl of southwestern Florida. 

It is much shorter than E. caloosana from localities 

farther east and has a more carinate and le^s inflated 

umbbhal ridge. The anterodorsal region of E. platyura 

tends to be more angulate than in E. variabilis, giving 

the shell the effect of being higher anterior1 y, with a 

more nearly horizontal border and a mc^e nearly 

vertical posterior margin, especially when viewed from 

the inside. The shell of E. platyura tends to be little 

inflated anteriorly, sloping evenly from the umbonal 

ridge to the anterior margin, and the anterior ribs show 

a strong tendency to become less elevated with shell 

growth.

None of the adult varieties of E. platyura particularly 

resemble any of the varieties of E. variabilis or E. 

caloosana farther east, but the younger stages of the 

typical form—that is, specimens comparing with the 

lectotype—are very similar to the young stages of E. 

caloosana, and the two are probably related. The 

varieties of E. vanabUis resemble Miocene forms from 

the Carolinas, whereas the varieties of E. platyura have 

no known Miocene equivalents and appear to be the
SPECIES AND GENERA OF TERTIARY NOETINAE 23

result of Pliocene variation. It is probable that E. 

caloosana and E. platyura are typically southern species, 

not related to E. variabilis except through ancestral 

upper Miocene forms. There is evidence that at some 

later time in the Pliocene, however, the E. variabilis 

stock invaded southwestern Florida and merged with 

E. platyura to produce a pre-ponderosa stock. At one 

of the upper Pliocene localities near Bermont, Fla., a 

form is found which resembles E. variabilis more than 

it resembles E. platyura, at the Alligator Creek and 

Shell Creek horizons. At a horizon penetrated in a 

ditch 1.6 miles northwest of Murdock, which probably 

represents the uppermost Pliocene of Florida, the 

Myakka Elver stage, a short, subtrigonal form which 

is hardly distinguishable in shape from typical E. 

ponderosa was found.

The genetic composition of the Pliocene forms is not 

as simple as the treatment of former authors would 

indicate, but unfortunately the data are still not entirely 

at hand. It appears that the ancestry of all the Pliocene forms may be traced, either directly or through 

some uppermost Miocene species, to E. trigintinaria, 

or to its southernmost representative in the Choctawhatchee formation. Some species appear to be monophyletic (E. limula, E. caloosana}, whereas others appear 

to be composed of several Miocene stocks as well as 

strains of other Pliocene species (E. variabilis). The 

more variable species, E. variabilis and E. platyura, 

produced a large number of varieties; indeed, each 

locality has furnished some particular type that is 

rare or unduplicated at others, such as the extreme 

form from Prairie Creek (pi. 3, fig. 3). Nothing of 

value seems to be gained from naming any but the most 

characteristic of these forms, however, especially as 

their differences appear to have been ironed out later 

on. Until their phylogeny is perfectly known, the 

last word on their nomenclature cannot be pronounced, 

but for the present the arrangement adopted here 

seems to be the most satisfactory.

Distribution: Pliocene, Caloosahatehee marl of southwestern 

Florida.

Type locality: West bank of Alligator Creek, just north of 

Acline, Charlotte County, Fla., U.S.G.S. 13833.

Other occurrences: Near the head of Prairie Creek, a tributary 

of Shell Creek, Charlotte County, Fla., U.S.G.S. 3300.

PLEISTOCENE SPECIES

Eontia palmerae MacNeil, n. sp.

. Plate 3, figures 7, 8

Shell subrhomboidal, medium elongate, rounded anteriorly, sharply rounded posteroventrally and moderately produced; beaks moderately high, situated just 

posterior of center; umbonal ridge sharply rounded; 

posterior slope moderately steep; medial sulcus weak or 

absent; ribs 29 to 32, averaging about 30, double or 

irregularly divided both anteriorly and posteriorly, interstitial ribs sometimes fairly strong medially; liga145569—38——1

ment shorter posteriorly than anteriorly, leaving a strip 

of the area of moderate length bare posteriorly, vertical 

elements appearing posteriorly when about one-third or 

half grown; teeth vertical centrally, inclined posteriorly, 

L-shaped anteriorly.

Holotype (U.S.N.M. 496533), length 59 millimeters, 

height 45 millimeters, convexity 20 millimeters.

This Pleistocene form has usually been identified as 

E. ponderosa but differs from it in being more elorgate, 

with ribs more doubled and with little tendency for 

them to be flat-topped. The beaks are relatively lower 

and the umbonal ridge less carinate. The sholl is 

thinner, and there is also a tendency for the media] area 

to be flattened or weakly sulcate.

Eontia palmerae is typically developed north of Cape 

Hatteras and became less distinct during Pleistocene 

time, owing first, apparently, to interbreeding with the 

relict variabilis stock farther south, and later to what 

probably represents a warm interglacial or postglacial 

stage, an invasion of the robust southern stock j\s far 

north as Marthas Vineyard and Nantucket, a northern 

record for the genus.

Eontia palmerae appears to be related to E. tillensis and 

possibly to E. limula. Thin-shelled specimens from deposits of probably not very late Pleistocene age at Heislerville, Cumberland County, N. J. (pi. 3, fig. 8), are 

similar to the holotype of E. tillensis from TiUys Lake, 

S. C. Dall considered the Heislerville fauna to be 

Pliocene. At Wailes Bluff on the Potomac River, St. 

Marys County, Md., typical E. palmerae occurr as a 

heavier but still moderately thin-shelled, true-breeding 

species. The region farther south, from Cape Hatteras 

to the Florida east coast, exhibits a varied, robust, 

thick-shelled form that is believed to identify it r,s the 

region in which the E. variabilis stock survived. This 

form is tentatively referred to E. ponderosa but is not 

regarded as typical.

In the late Pleistocene the robust, ponderosi-like 

form migrated as far north as Marthas Vineyard and 

Nantucket. That these heavy, subquadrate shells are 

not very old is evidenced by their slight amount of 

leaching. This northern advance was followed by a 

retreat, and at the present time no living shells, as shown 

by adhering periostracum, can be found north of Cape 

Hatteras. The collection in the United States National 

Museum contains one small specimen, supposedly taken 

living off Marthas Vineyard, but so far this record has 

not been verified. Dr. Horace G. Richards, of the New 

Jersey State Museum, who has been checking the Pleistocene and Recent ranges of Atlantic coast Mollusca, 

concurs in this statement. The Marine Biological Laboratory at Woods Hole, Mass., has not obtained a single 

living specimen in all its dredgings for the last 40 rears.

Distribution: Early and middle Pleistocene north of Cape 

Hatteras.

Type locality: Wailes Bluff, near Cornfield Harbor, Potomac 

River, St. Marys County, Md.; U.S.G.S. 10902.
24 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Other occurrences: Heislerville, Cumberland County, N. J., 

U.S.G.S. 2110; Dismal Swamp Canal, about 8)2 miles south 

of the Virginia-North Carolina line, Camden County, N. C., 

U.S.G.S. 11995.

Doubtful identifications: Variable forms which may be hybrids of E. palmerae and a relict E. variabilis stock occur in the 

Pleistocene along the Neuse River near Croatan, Craven County, 

N. C., U.S.G.S. 10893, and along the Intracoastal Waterway 

between the Little River and Myrtle Beach, Horry County, S. C., 

U.S.G.S. 13424, 13425, and are referred to E. ponderosa.

Eontia veroensis MacNeil, n. sp.

Plate 3, figure 6

Shell subovate and inflated, moderately elongate, 

rounded anteriorly, more sharply rounded and produced posteroventrally; beaks moderately high, situated 

at about the center of the hinge line; umbones not very 

high; umbonal ridge rounded and moderately sharp; 

posterior slope moderately steep; medial sulcus rarely, 

if ever, noticeable; ribs averaging about 32 or 33, double 

or irregularly divided along the umbonal ridge and 

anteriorly as well in some specimens, interstitial ribs 

present posteriorly and to a lesser extent anteriorly, 

but usually obsolete medially, larger ribs tending to be 

flat-topped; ligament shorter posteriorly than anteriorly, leaving a narrow strip of the area bare posteriorly, vertical elements appearing posteriorly when 

about one-quarter grown; teeth vertical centrally, 

inclined posteriorly, L-shaped anteriorly.

Holotype (U.S.N.M. 496580), length 52 millimeters, height 35 millimeters, convexity 17 millimeters.

This species occurs in a restricted area in the vicinity 

of Vero, St. Lucie County, Fla. It is smaller, is somewhat more elongate and inflated, and has several more 

ribs than the more robust form farther north. E. 

veroensis appears to be connected by intermediate 

forms with the E. limula-like form occurring in the 

Pliocene near Melbourne and Fellsmere, in Brevard 

and St. Lucie Counties, but is smaller and more inflated 

and lacks the medial sulcus. E. veroensis is probably 

not veiy late Pleistocene and represents an uncontaminated strain.

Distribution: Lower (?) Pleistocene, St. Lucie County, Fla. 

Type locality: Vero, St. Lucie County, Fla., U.S.G.S.'7853.

RECENT SPECIES

Eontia ponderosa (Say) MacNeil

Plate 3, figures 9-12

Area ponderosa Say, Acad. Nat. Sci. Philadelphia Jour., 1st ser.,

vol. 2, p. 267, 1822.

Area contraria Reeve, Conchologia iconica, Area no. 55, 1844. 

Area elegans Philippi, Zeitschr. Malacozoologie, p. 92, 1847;

Abbildungen und Beschreibungen Conchylien, vol. 3, p. 86,

Area tab. 5, fig. 5, 1849 [not Area elegans Perry, 1811;

Roemer, 1836; D'Orbigny, 1844; Wood, 1846, or De

Koninck]. 

Noetia contraria. Dunker, Novitates conchologicae, Mollusca

marina, p. 122, p. 40, figs. 4, 5, 1870. 

Area (Noetia) contraria. Kobelt, Conchylien-Cabinet voii

Martini und Chemnitz, Area, p. 23, pi. 7, figs. 4, 5, pi. 8,

figs. 3, 4, 1891. 

Area (Noetia) ponderosa. Kobelt, idem, p. 123, pi. 32, figs. 1,

2, 1891.

Area (Scapharcaf) elegans. Kobelt, idem, p. 184, jl. 45, figs.

5, 6, 1891. 

Area (Noetia) ponderosa. Dall, Wagner Free Inst. Fci. Trans.,

vol. 3, pt. 4, p. 633, 1898. 

Sheldon, Palaeontographica americana, vol. 1, no. 1, p. 28,

pi. 6, figs. 6-10, 1916. 

Lamy, Jour, conchyliologie, vol. 55, p. 299, 1907.

Shell obliquely trigonal or subrhomboidel, short; 

anterior rounded, posteroventral margin bluntly angulate and moderately produced; hinge line short posteriorly; beaks high, situated just posterior to the center 

of the hinge line; umbonal ridge carinate; posterior 

slope steep; ribs 25 to 30, averaging about 2°, double 

or irregularly divided posteriorly, frequently double 

anteriorly but when remaining single usually flat-topped, 

beaded in very young stages; interstitial riblets usually 

present posteriorly; ligament longer anteriorly than 

posteriorly, leaving a moderately narrow strip of the 

area bare posteriorly; teeth small and vertical centrally, 

inclined posteriorly, L-shaped anteriorly, anterior and 

posterior rows subequal in length. (Emended description.)

Figured specimens: Murdock form (U.S.N.M. 

496534), length 47 millimeters, height 39 millimeters, 

convexity 18 millimeters. Pleistocene form, from 

Bradenton, Fla. (U.S.N.M. 496535), length 44 millimeters, height 37.5 millimeters, convexity 17.5 millimeters. Recent, Florida (U.S.N.M. B1055), length 

67.5 millimeters, height 58 millimeters, convexity 27.5 

millimeters.

Considerable has already been said concerning this 

well-known species under its related forms. The living 

species is quite constant in form, and nowhere throughout its long range does it show any consistent local 

variation. During the Pleistocene epoch, however, 

several local varieties as well as two Atlartic coast 

forms regarded as separate species existed, all of which 

contributed to typical E. ponderosa. This condition 

makes it difficult to decide the limits to whicl the specific name should be applied, inasmuch as none but the 

most recent of the Pleistocene forms can be regarded 

as representing the sum total genetic composition of the 

Recent species. Possibly all the early Pleistocene varieties should be recognized, but until the stages of the 

Pleistocene of the Atlantic and Gulf Coastal Plains are 

worked out in more detail, it seems better to designate 

them as local forms of E. ponderosa.

The form occurring in beds believed to be Pliocene, 

because of the occurrence of Conus adversarius Conrad, 

near Murdock, Fla., is indistinguishable from the Recent 

form in shape and is referred to E. ponderosa. The 

possibility exists, however, that these beds are Pleistocene. Elsewhere along the Florida west coast undoubted Pleistocene beds carry a medium-sized shell 

which, although somewhat variable, is predominantly 

of the short, E. ponderosa type. The species is less 

variable in Pleistocene beds in Louisiana.

Along the Atlantic coast two Pleistocene species have 

been recognized, one in the north, E. palmerae and the
SPECIES AND GENERA OF TERTIARY NOETINAE 25

E.platyura

E.caloosana

E. trigintinaria 

(Choctawhatchee form)

Other in the south, E. veroensis. In addition, a relict 

of the E. variaMlis stock existed in the intervening area 

that gradually absorbed the E. palmerae stock and migrated as far north as Nantucket. This vigorous 

southern stock was probably supplemented by the more 

quadrate pre-ponderosa stock from the Florida west 

coast during this time, resulting in complete absorption 

of E. veroensis and finally in the homogeneous, longranging Recent species.

A specimen that undoubtedly belongs to this species 

is in the Japanese collection in the United States National 

Museum, supposedly from the 

Ryukyu Islands. It was acquired along with other specimens from the United StatesFish 

Commission. I am inclined to 

doubt the correctness of this - 

label, but it is not impossible 

that this species has been introduced in Japanese waters, just 

as many Japanese species have 

been introduced into California 

waters along with the spat of 

the edible Japanese oyster.

Distribution: Upper Pliocene (?) of 

western Florida, Pleistocene and 

Recent.

Range: Upper Pleistocene, Nantucket to Louisiana and west (?); 

Recent, Cape Hatteras to Yucatan.

Louisiana well records: All the 

known Pleistocene specimens from 

Louisiana were obtained from wells. 

Specimens are in the United States 

National Museum from a well in lower 

Plaque-mines Parish at a depth of 

740 feet, and from Cameroii Parish

at a depth of 912 to 972 feet. Miss Maury 8 lists other records 

as follows: "Grand Chenier, New Orleans pumping station no. 7, 

New Orleans artesian well of 1856 at 480 and 560 feet (Hilgard), 

Lake Borgne borings; Knapp's wells, Terrebonne Parish, no. 2, 

at 1,519-1,542, 1,632-1,726, 1,719-1,842, no. 3 at 670, 1,579- 

1,618, 1,700, Crowley well no. 4, Jennings, at 1,663-1,670 feet." 

The rapid accumulation of sediments in the region of the Mississippi Delta makes it probable that all these depths are within 

Pleistocene strata. Care should be exercised in the future in 

delimiting the stratigraphic and geographic ranges of Eontia 

ponderosa and Noetia gardnerae in the northern Gulf region.

In the accompanying diagram (fig. 2) are shown the 

supposed relationships of the North American species 

of Eontia. The general plan of the evolution of these 

organisms does not appear to be one of continual 

branching out, but rather one in which the tendency 

to diversification is limited by hybridization. Once 

long-ranging species appear to have been broken up, 

by whatever process, into various geographic species 

and subspecies, some of which persisted in isolated 

regions practically unchanged. There is evidence that 

later two or more of these true-breeding species were 

brought together and produced an extremely heterogeneous series of forms, individuals of which cr,n be 

selected that recall either or any of the contributing 

species and all stages in between. From this hybrid 

series there emerged not further modifications of the 

original species but a single, less variable form, unlike 

any of the earlier species. This emergent probably 

does not represent the sum total genetic composition 

of all the parent species, nor a simple linear descendant of one of them, but rather a partial recombination 

of the characters of all of them. Other recombinations 

of the same parentage did not survive. Thus, whatE. ponderosa

E.palrr«?r-i

\

E.tillensis

E.ponderosa 

(Murdock form)

E. incile yorkensis

E. incile

s Maury, C. J., Bull. Am. Paleontology, vol. 8, no. 34, p. 15, 1920.

E. incile mansfieldi •*-" """•

FIGURE 2.—Diagram showing supposed relationships of North American species of Eontia.

ever extinction takes place during the process of hybrid 

synthesis, it does not appear to be a wholesale extinction of any of the contributory strains but ratl °r of 

uiisuited phenotypes resulting from the union. The 

emergent thus traces its ancestry not to any one of the 

original strains but to all of them, and its familv tree 

takes the form of two or more species converging to 

produce a single species.

PACIFIC GROUP 

Genus PROTONOETIA MacNeil, n. gen.

Type species: Anadara nigeriensis Newton.

Shell subquadrate, inflated, subangulate posteroventrally; hinge line long, beaks nearly central and orthogyrate; umbonal ridge subcarinate; sculpture consisting of regular ribs of about equal size all over the 

disk and posterior slope, and interstitial ribs in young 

stages which may persist into the adult stage; interstitial ribs lirate in nealogic stage, beaded later; principal ribs beaded in nealogic stage, smooth in adults; 

ligament extending both anteriorly and posteriorly, 

covering the entire anterior part of the cardinal area; 

teeth short and vertical centrally, inclined and tending 

to be L-shaped terminally.
26 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

This genus exhibits a combination of characters 

which distinguishes it from all others and yet has single 

characters which definitely link it with other genera. 

Its ligament entirely fills the anterior part of the area, 

as in Noetia, but the posterior portion of the ligament 

is more produced, and the hinge line is longer than in 

any known species of that genus. In addition the 

beaks are orthogyrate and just anterior of the center, 

rather than opisthogyrate and well into the posterior 

half of the hinge line, or terminal as in Noetia.

The sculpture of the young stages shows the primary 

and secondary ribs characteristic of the Noetinae. 

Adults of Protonoetia do not particularly resemble any 

species of Striarcinae but rather bear a superficial 

resemblance in shape to some Miocene to Recent species 

of Area, which led the author of the type species to refer 

it to Gray's genus Anadara. Protonoetia is intermediate 

in hinge, beak, and ligament characters between Noetia 

and early members of the Noetidae. Protonoetia 

represents in ligament evolution from its hypothetical 

ancestor a step comparable to that between Eontia and 

Sheldonella and the genus Scapularca in that the anterior 

part of the cardinal area is completely covered with 

ligament.

EOCENE SPECIES

Protonoetia nigeriensis (Newton) MacNeil 

Plate 4, figures 1-3

Anadara nigeriensis Newton, Geol. Survey Nigeria Bull. 3, p. 70, 

pi. 8, figs. 4-7, 1922.

Shell subquadrate, inflated, broadly rounded anteriorly, straighter posteriorly, sharply rounded or subangulate posteroventrally; hinge line long, making the 

shell subangulate at its dorsal extremities; beaks low, 

orthogyrate, situated just anterior of the center of the 

hinge line; umbonal ridge subcarinate; ribs 25 to 32, 

averaging 27 or 28, rounded posteriorly, slightly wider 

and flatter anteriorly, interstitial ribs frequently persisting into the adult stage on the posterior slope and 

in the anterodorsal region; ligament about twice as long 

anteriorly as posteriorly, covering the entire anterior 

part of the cardinal area; teeth short and vertical 

centrally, inclined and tending to be L-shaped terminally, anterior and posterior rows subequal in length. 

(Emended description.)

Lectotype, refigured (pi. 4, fig. 2), in British Museum. 

Topotype (U.S.N.M. 496536), length 29 millimeters, 

height 25 millimeters, convexity 11.5 millimeters. Newton's largest specimen, length 42 millimeters, height 35 

millimeters, double convexity 32 millimeters.

Little need be said concerning this species except that 

it represents a genus which is regarded as prototypical 

to Noetia. Not enough is known to say whether it is 

or is not in the direct line.

Distribution: Eocene, upper Lutetian of Nigeria.

Type locality: Ameki, Omobialla district, southern Nigeria.

Genus NOETIOPSIS MacNeil, n. gen.

Type species: Noetiopsis woodringi, n. sp.

Shell subrhomboidal or subtrigonal, rounded anteriorly, sharply rounded and produced posteroventrally; 

hinge line moderately short; beaks prosogyrate, situated 

well anterior of the center of the hinge line; umbonal 

ridge subcarinate; sculpture consisting of mar y regular 

ribs of about equal size; interstitial ribs may H present 

in adults on the posterior slope; ligament well produced 

posteriorly and anteriorly, completely covering the posterior part of the cardinal area; teeth arranged in an 

arc, vertical and shorter centrally, inclined posteriorly, 

tending to be L-shaped anteriorly, the posterior row 

slightly longer.

Noetiopsis differs from Protonoetia principally in the 

position and orientation of the beaks and in tiN part of 

the cardinal area covered by the ligament. In Noetiopsis 

the beaks are prosogyrate and well into the anterior 

half of the hinge line. The ligament completely fills the 

posterior part of the area and leaves only a narrow strip 

uncovered anteriorly. It thus differs from Protonoetia, 

in which the beaks are about central and orthogyrate 

and the ligament fills the anterior part of the area, 

leaving much of the posterior part bare. Juveniles of 

Noetiopsis have a longer hinge line and more expanded 

posterior slope, comparing more closely with Protonoetia 

than adults. It is possible that in future discoveries 

the length of the hinge fine may not be found to contrast 

as much as in the species now known.

Noetiopsis bears a striking resemblance to Noetia, 

principally because of its short hinge line and truncate 

posterior slope. If Protonoetia had a hinge line comparable in length to that of adults of Noetiopsis it 

would be even more Noetia-like owing to its beak and 

ligament characters. Noetiopsis approaches mc^e closely 

the genus Arginopsis, described below, occurring in the 

upper Eocene of Peru.

EOCENE SPECIES 

Noetiopsis woodringi MacNeil, n. sp.

Plate 4, figures 4-8

Shell subrhomboidal or subtrigonal, inflated, rounded 

anteriorly, sharply rounded and produced posteroventrally; hinge line moderately short; beaks prosogyrate and of medium height, situated at about the 

anterior third of the hinge fine; umbones full; umbonal 

ridge subcarinate; ribs 30 to 33, usually 31 or 32, of 

about equal size all over the disk and poster or slope, 

the posterior ribs rounded, the anterior rib^1 flatter; 

tending to be more in relief in young and middle 

adult stages; interstitial ribs sometimes persisting on 

the posterior slope; ligament about twice as long posteriorly as anteriorly, completely covering the posterior 

part of the cardinal area, leaving a narrow strip bare 

anteriorly; teeth arranged in an arc, vertical and shorter
SPECIES AND GENERA OF TERTIARY NOETINAE 27

centrally where they are cut off by the cardinal area, 

inclined posteriorly, tending to be L-shaped anteriorly, 

the posterior row somewhat longer.

Holotype (U.S.N.M. 496537). Paratype (U.S.N.M. 

496538). Figured topotype, the largest specimen seen 

(in Axel Olsson collection, Gloversville, N. Y.), length 

33 millimeters, height 27 millimeters, double convexity 

26 millimeters.

This species is very constant in the number of ribs, 

most specimens differing by only one rib. It thus 

differs from Protonoetia nigeriensis, in which the number 

ranges from 25 to 32. The maximum number of ribs in 

P. nigeriensis, however, is the normal number for N. 

woodringi. The shorter hinge line makes the demarcation of the cardinal area from the anterodorsal part of 

the disk less distinct, and the growth lines in that 

region pass onto the cardinal area with little interruption, except that they pass from a rounded to a flat 

surface.

Noetiopsis woodringi is a very conspicuous element in 

the fauna in which it occurs and, like all the upper 

Eocene Pacific Noetinae, has the aspect of Miocene or 

later arcid shells. This species may be the direct 

ancestor of the genus Arginopsis.

Distribution: Middle Eocene, Tonosi River, Panama.

Type locality: Bucaru, Port of Tonosi, Los Santos Province, 

Panama, U.S.G.S. 8414 (Axel Olsson collection); U.S.G.S. 

6586a (Donald MacDonald collection).

Genus ARGINOPSIS MacNeil, n. gen. 9

Type species: Scapharca (Argina) sullanensis Woods.

Shell subovate or rounded, inflated, all margins of 

about the same rotundity; beaks low, strongly prosogyrate, situated at the anterior end of the hinge line; 

hinge line moderately long; umbonal ridge rounded but 

distinct; sculpture consisting of many very regular ribs 

which tend to become low and flat-topped ventrally; 

interstitial ribs sometimes present posteriorly; ligament 

wholly posterior to the beaks, filling that part of the 

cardinal area completely; only a very short part of the 

cardinal area anterior to the beaks, and that sharply 

rounded and nearly atrophied; teeth vertical centrally, 

the anterior row inclined with the teeth, tending to be 

L-shaped, the posterior row long and extending away 

from the hinge line on an arcuate or more abruptly 

curved cardinal plate.

Arginopsis represents the opposite extreme in orientation to Noetia and is regarded as an aberrant genus. 

In Arginopsis the beaks are strongly prosogyrate, the 

ligament posterior, and the umbonal ridge rounded. 

In Noetia the beaks are opisthogyrate, the ligament 

anterior, and the umbonal ridge usually carinate, owing 

to twisting. These two genera illustrate remarkably

9 Arginopsis and Arginella take their names from the familiar name Argina, although they are not related to that group, and it might furthermore be pointed out 

that Argina is not available for Mollusca, because it is preoccupied in Lepidoptera 

by Argina Hubner, 1816. The valid name for Area pexata Say is probably Lunarca 

Gray.

well the way in which the entire aspect of a shell can 

be altered by a change in the position and orientation 

of the beaks.

This genus is closely related to Noetiopsis and probably was derived from it, although the genotype species 

may not form a linear series. It is not expected that 

many species of these two genera will be discovered, as 

one is regarded as a transitional and the other a terminal genus, both of relatively short geologic range.

Arginopsis cannot be regarded as ancestral to the 

Pliocene to Recent genus Lunarca (=Argina), a relationship which has been almost universally accented, 

because of its perfectly developed vertical ligament 

elements.

EOCENE SPECIES

Arginopsis sullanensis (Woods) MacNeil

Plate 4, figures 9-11

Scapharca (Argina) sullanensis Woods, in Bosworth, Geology 

and paleontology of northwest Peru, p. 62, pi. 1, fig. 5, 

1922.

Shell suborbicular and much inflated, anterior, posterior, and ventral margins about equally curved; I ^aks 

strongly prosogyrate and low, situated at about the 

anterior terminus of the hinge line; umbones moderately 

full; hinge line of moderate length; ribs about 40, 

smooth and tending to be flat-topped anteriorly, 

rounded posteriorly, becoming less elevated in fullgrown adults; interstitial ribs present on the posterior 

slope; ligament area narrow and partly obscufed by the 

overhanging margins, completely covering the part of 

the cardinal area posterior to the beaks; cardinal area 

very short anteriorly, with the border not well defined; 

teeth small centrally, somewhat crowded anteriorly, the 

hinge plate swinging ventrally at the posterior erd of 

the hinge line to form a short row of nearly horizontal 

teeth. (Emended description.)

Holotype in British Museum. Figured specimen 

(U.S.N.M. 496539), length 34 millimeters, height 31 

millimeters, double convexity 27 millimeters.

This species is remarkable for the number of its ribs, 

which exceeds that of any other known forms of Pr.cific 

Noetinae except some species of Noetia, from which it 

differs greatly in orientation. The known species of 

the genus Arginella have about 15 less ribs. The 

extremely prosogyrate beaks, narrow ligament area, 

and rotund outline give this species a striking resemblance to the Pliocene to Recent species Lunarca pexata 

(Say) and led its author to refer it to that group.

Distribution: Upper Eocene, Talara and Saman formations, 

Peru.

Type locality: Ten miles west-northwest of Sullana, Peru.

Figured specimens: Hacienda Saman, south escarpment of 

mesa, 30 to 40 feet below top, at mouth of Rio Chira, 3 miles 

inland from the ocean, Piura Department, Paita district, Peru, 

U.S.G.S. 5556.
28 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Genus ARGINEIIA MacWeil, n. gen.

Type species: Area (Argina} samanensis Olsson.

Shell subrhomboidal to subovate, rounded anteriorly, 

more sharply rounded posteroventrally, often subangulate anterodorsally; beaks moderately low to very 

low, prosogyrate, situated at or near the anterior end 

of the hinge line; hinge line short to medium length; 

umbones high, narrow to moderately full; umbonal 

ridge conspicuous but rounded; sculpture consisting of 

very regular but comparatively few ribs that tend to 

become less elevated ventrally; interstitial ribs usually 

present on the posterior slope; ligament wholly or 

almost wholly posterior to the beaks, filling that part of 

the cardinal area completely; cardinal area narrow, the 

part anterior to the beaks plane or concave, forming a 

lunular area, to more rounded and indistinct; teeth 

numerous, small and vertical centrally, longer and inclined terminally, swinging away from the hinge line 

on a narrow, arcuate cardinal plate posteriorly, the 

short anterior row beginning beneath the beaks, offset 

from and diagonal to the posterior row.

The species included in this genus form a more or 

less linear series showing the transition of the anterior 

part of the cardinal area from a lunulelike area to a 

shorter, convex area which passes insensibly into the 

anterior part of the disk. Its ultimate form thus 

compares with Arginopsis in this respect, but it differs 

from that genus in being smaller, having less prosogyrate and more central beaks, a shorter hinge line and 

ligament area, and a more arcuate cardinal plate. The 

species of Arginella all have about 15 less ribs than the 

monotype of Arginopsis.

The developmental process that produced Arginopsis 

was an initial gyration and shifting of the beaks nearly 

to the anterior end of the cardinal area, resulting in a 

long posterior ligament area. In Arginetta the beaks 

were not shifted as far anteriorly, with the result that 

the anterior end of the cardinal area became lunular 

and then indistinct, whereas the posterior ligament 

area was comparatively short.

Noetiopsis differs from Arginella in being larger, with 

more ribs, and in having a wider cardinal area with 

about a third of the ligament anterior to the beaks. 

The hinge line coincides with the cardinal area throughout, whereas in Arginella the lunular anterior part is 

diagonal to the hinge line.

The genera Protonoetia, Noetiopsis, Arginopsis, and 

Arginella are all closely related. At the present time 

it is not possible to make positive statements regarding 

their phylogeny, or to say in which direction evolution 

proceeded. It is believed, however, that the ancestral 

form was intermediate between Protonoetia and Noetiopsis and that three subsequent groups were developed 

—the Protonoetia-Noetia group, the Noetiopsis-Arginopsis group, and Arginella.

No interstitial ribs have been observed in any specimens of Arginella thus far observed, although in some

specimens the sculpture is well preserved down to about 

the beginning of the adult stage. It remrms to be 

seen on specimens with the nealogic sculpture preserved 

whether or not the primary ribs are present in that 

stage.

EOCENE SPECIES

Arginella samanensis (Olsson) MacNeil

Plate 4, figures 12, 13

Area (Argina) samanensis Olsson, Bull. Am. Paleontology, 

vol. 15, no. 57, p. 5, pi. 1, figs. 4, 5, 1929.

Shell subrhomboidal, varying in inflation, rounded 

anteriorly, ventral margin sometimes contracted, sharply rounded posteroventrally, often subangulg.te anterodorsally; beaks strongly prosogyrate and moderately 

low, situated at about the anterior end of the hinge 

line; hinge line of medium length; umbones moderately 

narrow; ribs about 25, rounded posteriory, flatter 

anteriorly, becoming less elevated or level with the 

interspaces in adults; interstitial ribs present on the 

posterior slope; ligament area moderately narrow and 

posteriorly obscured by the overhanging margins, 

posterior to the beaks except for a very small anterior 

extension, completely filling the posterior pQ,rt of the 

cardinal area; the cardinal area anterior to th.3 ligament 

out of the plane of the ligament area, forming a plane 

or concave lunular area; teeth small and vertical 

centrally, inclined terminally, the posterior row long 

and arcuate, swinging away from the hinge line on a 

curved or arcuate cardinal plate, anterior row about 

half as long, diagonal to and offset from the hinge line. 

(Emended description.)

Holotype in Paleontological Research Institution, 

Ithaca, N. Y.; figured specimen (topotype?) (U.S.N.M. 

496540), length 23 millimeters, height 20.5 millimeters, 

double convexity 16 millimeters. A shorter and more 

inflated specimen, length 24 millimeters, height 23 

millimeters, double convexity 19.5 millimeters.

This species occurs with Arginopsis sullanensis, but 

the two do not intergrade, a fact which supports the 

morphologic reasons for placing them in different 

genera. It differs from Arginopsis sullanensis in being 

smaller and subrhomboidal rather than suborbicular 

and in having about 15 less ribs, less prosogyrate and 

more posterior beaks, narrower umbones, a mc^e sharply 

rounded umbonal ridge, and a lunulelike development 

of the anterior part of the cardinal area. This and 

the other species of Arginella have fewer ribs than 

either Noetiopsis woodringi or Arginopsis sullanensis, 

the number being about the minimum number found 

in Protonoetia nigeriensis.

The lunular area is a striking feature of this species 

and is probably better developed in it than in the 

Oligocene species. It dips to the anterior out of the 

plane of the ligament area, and when the valves are 

open there is a gape between its opposing margins, so 

that, while morphologically a part of the cardinal area,
SPECIES AND GENERA OF TERTIARY NOETINAE 29

its edges no longer form a part of the hinge line. Kotation of the beaks to the anterior was not as complete 

as in Arginopsis and is compensated for by a degeneration of the anterior part of the cardinal area.

Distribution: Upper Eocene, Talara and Saman formations, 

Peru.

Type locality: Casa Saman, Peru (Olsson).

Other occurrences: Lagunitas and Talara (Olsson).

Figured specimens (topotypes?), Hacienda Saman, south 

escarpment of mesa, 30 to 40 feet below top, at mouth of Rio 

Chira, 3 miles inland from ocean, Piura Department, Paita 

district, Peru, U.S.G.S. 5556.

OIIGOCENE SPECIES

Arginella puntabravoensis (Olsson) MacNeil

Plate 4, figure 14

Area (Argind) puntabravoensis Olsson, Bull. Am. Paleontology, 

vol. 17, no. 63, p. 38, pi. 2, figs. 1, 4, 1931.

Shell subrhomboidal, inflated, bluntly angulate 

anterodorsally, sharply rounded and often produced 

posteroventrally, ventral margin contracted; beaks 

prosogyrate; umbones moderately full; ribs regular, 

about 22 to 23, tending to be flat-topped or even 

concave ventrally; ligament area narrow and posterior 

to the beaks; cardinal area forming a lunular area 

anteriorly; teeth not visible on any of the specimens 

examined. (Emended description.)

Holotype in Paleontological Research Institution, 

Ithaca, N. Y. Olsson gives the following measurements for two specimens: Length 22 millimeters, 

height 19 millimeters, convexity 6 millimeters; length 

20.5 millimeters, height 18 millimeters, convexity 8 

millimeters.

This species is much like the more inflated and angulated variants of A. samanensis and differs from them 

principally in being more inflated; with fuller and 

higher umbones and a more contracted ventral margin. 

This is the only one of the known aberrant species 

which is not present in my collection, so that it is not 

compared with related species in very great detail. 

The type was examined at an early stage in the preparation of this paper, before the critical characters of 

the other species had been recognized.

Distribution: Middle Oligocene, Mancora formation, Punta 

Bravo grits of Punta Bravo, Peru (Olsson).

Arginella ovalis MacNeil, n. sp.

Plate 4, figures 15, 16

Shell subovate, inflated, rounded anteriorly and 

posteriorly, broadly rounded ventrally, more sharply 

rounded posteroventrally and anterodorsally; beaks 

very low, prosogyrate, situated at the anterior end of 

the hinge line; hinge line short; umbones high and 

moderately full; umbonal ridge rounded but well 

defined; ribs 23 to 25, very regular and rounded, less 

elevated ventrally; interstitial ribs usually present

on the posterior slope; interspaces neatly sculptured 

by raised growth varices; ligament very narrow and 

wholly posterior to the beaks, partly obscured by 

overhanging margins; anterior part of cardinal area 

somewhat lunular but not well defined; teeth very 

numerous, small and vertical centrally, longer and 

inclined posteriorly, swinging away from the hinge 

line on a long, narrow cardinal plate, anterior row 

beginning beneath the beaks, offset from and diagonal 

to those along the hinge line.

Holotype (U.S.N.M. 496541), length 18.5 millimeters, height 17.5 millimeters, convexity 5 millimeters. 

Paratype (U.S.N.M. 496542).

This is the smallest of the three species referred to 

the genus Arginella. It differs from the other two 

species in being more rounded, without any contraction 

of the ventral margin, and with broader and fuller 

umbones. The ligament area is smaller, and the 

lunular area is more indistinct in adults, although in 

young shells the anterodorsal region is more ang'ilate 

and the lunular area less rounded. Only about a 

third of the teeth of this species are along the 1 ; nge 

line, the entire anterior row and the posterior hrlf of 

the posterior row being situated on a cardinal plate 

diverging from it.

Distribution: Oligocene(?), Colombia.

Type locality: Between Arroyo Mancamajon and Ovejas, 

Bolivar Department, Colombia, U.S.G.S. 11482.

Genus NOETIA Gray

Type species: Area reversa Sowerby.

Shells ranging in shape from subrhomboidal to subtrigonal, usually produced or angulate posteroventrally; 

beaks opisthogyrate, varying from just posterior of the 

center of the hinge line and high to very posterior and 

low; cardinal area wide or very narrow posteriorly 

according to the position and height of the beaks; 

umbonal ridge well defined, usually carinate; sculpture 

consisting of rounded or flat-topped ribs, more in relief 

dorsally, becoming less elevated or even lower than 

the interspaces ventrally; ribs usually of equal sire all 

over, but larger anteriorly in some species; interstitial 

ribs frequently present, especially posteriorly; inner 

margin deeply crenulated by ribs posteroventrally; 

ligament area covering the entire anterior part of the 

cardinal area, extending a very short distance posteriorly in high-beaked species; teeth arranged in a troad 

arc, vertical centrally, inclined posteriorly, L-shaped 

anteriorly, the anterior and posterior rows subequal in 

length in species with more central beaks, the anterior 

row longer in species with posterior beaks. (Emended 

description.)

Although Noetia forms a recognizably compact 

genus, it can be seen from the descriptions that the 

species are rather variable. It can be distinguished 

from all other genera of the Pacific group by its beaks, 

which, while showing all stages in a series, are always
30 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

posterior of the center and opisthogyrate. Noetia 

differs from the Atlantic genus Eontia, with which it 

has usually been combined, in having decidedly more 

regular sculpture, the ribs smoother and never divided, 

and the interstitial ribs but weakly developed; deeper 

and longer posteroventral crenulations of the inner 

margin; and a more anteriorly restricted ligament 

area, the posterior extension never being as long as 

in Eontia.

Noetia has a range from the upper Eocene to Recent, 

three species being known from the upper Eocene of 

the Indo-Pacific and the rest from the lower Miocene 

to Recent of America. While the Pacific Noetinae are 

represented in the Eocene and Oligocene of America by 

the genera Noetiopsis, Arginopsis, and Arginella, there 

is reason to regard these as aberrant genera, and the 

American species of Noetia as derived from the IndoPacific stock.

Most of the American species are of middle or upper 

Miocene age and lived in Pacific waters, or in waters 

having free intercourse with or recently separated from 

Pacific waters. These species are distributed in Peru, 

Ecuador, Colombia, Panama, Costa Rica, Venezuela, 

and Trinidad. The genus survived the reseparation 

of the Caribbean and Pacific, one species being known 

from the upper Miocene or Pliocene of Texas, and 

another from the upper Pliocene of Trinidad, but it 

apparently became extinct after late Pliocene time in 

the Gulf and Caribbean region. The only Recent 

species lives in the Pacific from the Gulf of California 

to Peru.

INT>O-PACIFIC SPECIES

EOCENE SPECIES

Noetia molengraffi (Martin) MacNeil

Plate 4, figures 22, 23

Area (Anadara) molengraffi Martin, Geol. R. Mus. Leiden 

Samml., new ser., vol. 2, p. 184, pi. 7, fig. 191-2, 1915.

Shell subrhomboidal, moderately inflated, anterior 

rounded, posteroventral margin sharply rounded and 

somewhat produced; beaks of about medium height, 

situated at about the anterior fifth of the hinge line; 

umbones moderately high and full; umbonal ridge 

sharply rounded; ligament mostly anterior, extending 

only a short distance posteriorly; ribs small and regular, 

about 38 to 40, rounded posteriorly, flatter anteriorly, 

less in relief ventrally; teeth vertical centrally, Lshaped anteriorly, inclined posteriorly, the posterior 

row short and diagonal to the anterior row. (Emended 

description.)

Lectotype (hi Rijksmuseum van Geologic en Mineralogie, Leiden), length 42 millimeters, height 36 

millimeters.

The accompanying figures are the first published 

photographs of this species and show the details of the 

hinge and sculpture better than the original drawings. 

The ribs are very regular and comparatively small for

Noetia. The beaks, although well toward the posterior end of the hinge line, are high, so that the area is 

as wide beneath the beaks as it is more anteriorly. 

Distribution: Upper Eocene, Nanggulan, Java.

Noetia pondaungensis Cotter

Plate 4, figures 17, 18 -

Area (Noetia) pondaungensis Cotter, Paleontologia indica, 

new ser., vol. 7, no. 2, p. 20, pi. 5, figs. 1, 2, 1923.

Shell subrhomboidal, inflated, anterior rounded, posteroventral margin produced and angulate; b°,aks high, 

near the posterior end of the hinge line; uml ones high 

and narrow; umbonal ridge angulate; posterior slope 

steep; ligament area moderately wide ard mostly 

anterior to the beaks; ribs about 35, fat-topped 

anteriorly, rounded posteriorly and becoming submerged below the level of the interspaces in adults; 

teeth vertical centrally, inclined terminally, the anterior row much the longer. (Emended description.)

Holotype (hi Geological Survey of India, Calcutta), 

length 44 millimeters, height 34 millimeters, convexity 

15 millimeters.

This species has a more pointed posteroventral 

margin, a more angulate umbonal ridge, higher beaks, 

and a wider cardinal area than the Javanese species. 

The ribs are less numerous and wider in tl is species 

than in N. molengraffi and become distinctly submerged 

in adults. Cotter did not describe this condition in 

exactly these words but stated that "both ribs and 

furrows are crossed by fine, wavy lines of growth which 

[ventrally] curve downward on the ribs and upward in 

the furrows", the opposite of the condition with 

elevated ribs.

It is interesting to note that although the ribs in all 

the species of Pacific Noetinae tend to become less 

elevated in adults, actual submergence of tl ?,m below 

the level of the interspaces is attained in only a few 

species, the most outstanding of which are the Panama 

Eocene form Noetiopsis woodringi, the Burmese Eocene 

species Noetia pondaungensis, and the Trinidad Miocene 

species N. manzanillae and N. mundonuevensis.

Distribution: Upper Eocene, Pondaung sandstone". Burma.

Noetia nagaoi MacNeil, n. name

Plate 4, figures 19-21

Area (Noetia) pondaungensis Cotter var. transversa Nagao, 

Tohoku Univ. Sci. Rept., ser. 2, Geology, vo1 . 12, no. 1, 

p. 26, 27, pi. 6, figs. 8, 9, 1928.

Shell subrhomboidal, moderately inflated, elongate 

and sharply rounded anteriorly, angulate posteroventrally; beaks moderately high and near the posterior 

third of the hinge line; umbonal ridge sharp; posterior 

slope flattened; ribs about 40, apparently wider than 

the interspaces; ligament area wide and mostly anterior, 

but well extended posteriorly as well; teeth vertical
SPECIES AND GENERA OF TERTIARY NOETINAE 31

centrally, inclined terminally, but not well exhibited 

in the type. (Emended description.)

Holotype (Institute of Geology and Paleontology, 

Sendai, Japan, no. 36012), length 57 millimeters, height 

37 millimeters.

The elongate anterior end and angulate posterodorsal 

margin shown in the figure may be due to crushing, for, 

as Nagao states, "the shell is somewhat variable in 

shape, usually being as high as long." From the figures 

it appears to differ from the Burmese and Javanese 

species in being larger and in having more central beaks 

and a greater posterior extension of the ligament. In 

this respect it appears to be the most extreme of the 

known species of Noetia and approaches the genus 

Protonoetia.

The photographs here used were kindly furnished 

by Professor Nagao. As the name transversa is preoccupied in Area, Professor Nagao suggested that I 

take the opportunity to rename his homonym. I take 

great pleasure, therefore, in naming this species in honor 

of its discoverer.

Distribution: Upper Eocene, Doshi beds, Asakura coal field, 

Province of Chikuzen, Japan.

AMERICAN SPECIES

MIOCENE SPECIES

Noetia stewarti MacNeil, n. sp.

Plate 5, figures 1, 2

Area (Noetia) retractata. Olsson, Bull. Am. Paleontology, vol. 

19, no. 68, p. 76, pi. 4, fig. 8 [not fig. 2], 1932.

Shell subrhomboidal or subtrigonai, inflated, anterior 

rounded, angulate and produced posteroventrally; beaks 

high and situated just behind the posterior third of the 

hinge line; umbones high and narrow; umbonal ridge 

sharp; posterior slope steep; ribs about 42, narrow and 

of about equal width over the entire disk, more rounded 

on the posterior slope; ligament mostly anterior to the 

beaks but extending posteriorly a short distance, a wide 

strip of the area bare behind the beaks; cardinal area 

wider posteriorly; teeth nearly vertical centrally, 

L-shaped anteriorly, not preserved on the type posteriorly.

Holotype in Paleontological Research Institution, 

Ithaca, N. Y. A topotype loaned to me by Mr. Olsson 

measures, length 33 millimeters, height 29.5 millimeters, convexity 13 millimeters. The convexity is probably greater owing to crushing of the specimen.

This form was united with the upper Zorritos species 

N. retractata by Olsson but differs from that species in 

having narrower and more numerous ribs, higher beaks 

and umbones, a shorter disk, a wider ligament area, and 

a shorter hinge line posteriorly. In N. retractata the 

posterior row of teeth and dorsal margin are more 

nearly horizontal. Noetia stewarti is related to N. trinitaria in beak and ligament characters but differs from 

it in being larger and heavier and in being less produced

posteroventrally. Noetia ecuadoria, n. sp., is very similar in general form but is smaller, with a broader disk 

and lower and more posterior beaks.

It will be noted that N. stewarti and N. trinitaria have 

high beaks, with the cardinal area and ligament wider 

posteriorly, thus comparing with the upper Eocene 

Indo-Pacific forms in this respect rather than with later 

American forms, in which the beaks are lower and more 

posterior, making the area narrower posteriorly.

The exact age relationship of the lower Zorritos of 

Peru and the Manzanilla beds of Trinidad is not settled, but it is very probable that some specimens furnished to me by Mr. Olsson from the "transitions,1 beds 

between the Heath shales and the lower Zorritos" of 

Peru are the oldest specimens of Noetia thus far obtained 

from the Americas.

Distribution: Lower Miocene, lower Zorritos sandstone and 

underlying transitional beds between it and the Heath shales, 

Peru.

Type locality: Quebrada Boca Pan at Zapotal, just south of 

Vacura, Province of Tumbez, Peru.

Other occurrences: Quebrada La Cruz, north of Mr.l Paso 

and about 4 miles inland, Peru.

Noetia trinitaria (Guppy) Dall

Plate 5, figures 5, 6

Area trinitaria Guppy, Geol. Soc. London Quart. Jour., vol. 22,

p. 583, pi. 26, figs. 3a, 3b, 1866. 

Area (Noetia) trinitaria. Dall, Wagner Free Inst. Sci. Trans.,

vol. 3, pt. 4, p. 617, 658, 1898. 

Sheldon, Paleontographica americana, vol. 1, no. 1, p. 29,

pi. 7, figs. 1, 2, 1916.

Maury, Bull. Ana. Paleontology, vol. 10, no. 42, p. 35, pi. 3, 

figs. 1, 3, 4, 1925.

Shell subtrigonai, inflated, rounded anteriorly, very 

much produced posteroventrally; beaks high and situated at about the posterior third of the hinge line; 

umbones high and narrow; umbonal ridge sharp, curving outward; posterior slope very steep; ligament mostly 

anterior to the beaks, wider directly beneath the beaks; 

cardinal area wider posterior to the beajvs, wl °ire a 

moderately wide strip is uncovered by ligament; ribs 

about 40, becoming flat-topped and about leve? with 

the interspaces ventrally; teeth vertical centrally, inclined or L-shaped terminally, the anterior row sightly 

longer. (Emended description.)

Lectotype (U.S.N.M. 496543), length 26 millimeters, 

height 21.5 millimeters, convexity 11 millimeters,

Noetia trinitaria compares with N. stewarti in its high 

beaks, wide cardinal area, and rib texture. It has a 

sharper ridge and more produced posteroventra) margin, however, being one of the most extreme of the 

known species in this respect, and is considerably smaller 

than N. stewarti. Both of these species are probably 

related to N. ecuadoria, described below.

Distribution: Lower Miocene, Manzanilla formation, Trinidad.

Type locality: Northwest side of Manzanilla Point, Trnidad.
32 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Noetia manzanillae Maury

Plate 5, figures 3, 4

Area (Noetia} manzanillae Maury, Bull. Am. Paleontology, vol. 

10, no. 42, p. 41, pi. 8, figs. 13, 19, 1925.

Shell suboval or subtrigonal, much inflated, anterior 

short and rounded, posterior rounded from the posterior 

end of the ligament to the ventral margin, without any 

angulation posterodorsally, posteroventral margin more 

sharply rounded and slightly produced; beaks moderately high and divergent, situated at the posterior end 

of the hinge line, which is about central with respect to 

the shell as a whole; umbones high and moderately 

narrow; umbonal ridge rounded, not angular; ribs 

about 30, slightly narrower than the interspaces and 

becoming level with the interspaces or submerged ventrally; ligament entirely anterior to the beaks, 'not 

occupying any of the curved region posteriorly; teeth 

not well known. (Emended description.)

Holotype (in Paleontological Research Institution, 

Ithaca, N. Y.), length 10 millimeters, height 12 millimeters, convexity 6 millimeters.

This is the smallest known species of the genus and 

does not appear to be particularly related to any of its 

contemporaries. Miss Maury suggested that N. 

manzanillae might be entitled to subgeneric recognition, 

similar to that accorded to Sheldonella, because of its 

rounded umbonal ridge. In outline and convexity it 

is quite rotund, and the rounded posterior slope and 

posterodorsal margin are extreme for the genus. The 

types, although small, appear to be full-grown adults, 

inasmuch as the ribs become submerged, a condition 

which, though occurring in other species, has not been 

found in shells of this size.

Distribution: Lower Miocene, Manzanilla formation, Trinidad.

Type locality: North of Manzanilla Point, northeastern coast 

of Trinidad.

Noetia mundonuevensis Maury

Plate 5, figures 7-9

Area (Noetia) mundonuevensis Maury, Bull. Am. Paleontology, 

vol. 10, no. 42, p. 36, pi. 5, figs. 5, 7, 1925.

Shell subtrigonal, inflated, anterior broadly rounded, 

posterior margin nearly straight, posteroventral margin 

sharply rounded but not produced; beaks high, situated 

at about the posterior end of the hinge line; umbones 

high and moderately narrow; umbonal ridge sharply 

rounded; ribs about 30, flat-topped dorsally but becoming level or submerged ventrally, considerably so 

in the region of the umbonal ridge; ligament wholly 

anterior to the beaks, not constricted posteriorly; teeth 

nearly vertical centrally, L-shaped anteriorly, the posterior row oblique and the teeth inclined. (Emended 

description.)

Lectotype (in Paleontological Research Institution, 

Ithaca, N. Y.), length 40 millimeters, height 41 millimeters, convexity 19 millimeters. Paratype, length 27

millimeters, height 31 millimeters, convexity 14 millimeters. Figured topotype (in Museum of Geology, 

Cornell University, Ithaca, N. Y., no. 38635), if uncrushed, would measure about, length 31 millimeters, 

height 40 millimeters, convexity 15 millimeters.

This species has the high beaks and wide cardinal 

area characteristic of the early species of Noetic, as well 

as a very great submergence of the ribs along- the posterior part of the disk and umbonal ridge. It is well 

characterized by its relatively greater height than 

length and its high, narrow umbones. The submerged 

ribs, which coincide with the crenulations of the inner 

margin, form such deep indentations along the posteroventral margin in some specimens that the thick interspaces form toothlike, interlocking projections between 

the two valves.

The specimen figured is from the type lot and, although somewhat crushed, is better preserved internally than either of the figured cotypes. An enlargement of one of these to show the submergence of the 

ribs is reproduced on plate 5, figure 7. This specimen 

is here designated as lectotype of the species.

Distribution: Lower middle Miocene, Brasso beds, Trinidad. 

Type locality: Near the junction of the Mayo and C'ouva main 

roads, west-central Trinidad.

Noetia cholana Spieker

Plate 5, figures 21-23

Area (Noetia) cholana Spieker, Johns Hopkins Univ. Studies 

in Geology, no. 3, p. 95, pi. 5, figs. 2, 3, 1922.

Shell subrhomboidal or somewhat egg-shaped, elongate, not much inflated, anterior rounded, posterior 

broadly produced and somewhat angulate; b^aks low, 

situated near the posterior end of the area, bnt nearly 

central with respect to the shell, owing to the elongate 

posterior; umbones low and broad; umbonal ridge 

moderately carinate, curving outward so that the posterior angle is comparatively high; ribs about 35, slightly 

wider than the interspaces, tending to become flattopped, nearly level with the interspaces ^entrally; 

interstitial ribs developed all around in some specimens, 

absent anteriorly in others; ligament anterior to the 

beaks; a narrow strip of cardinal area posterior to the 

beaks but devoid of ligament; teeth vertical centrally, 

L-shaped anteriorly, inclined posteriorly, the posterior 

irow being nearly as long as the anterior row, and less 

.oblique to the hinge line than in most other species, 

owing to the more horizontal dorsal margin. (Emended 

description.)

Holotype (in Museum of Geology, Johns Hopkins 

University, Baltimore, Md.), length 34 ± millimeters, 

height 26 ± millimeters, convexity 10 ± millimeters. 

A less perfect specimen is larger.

, The relationship of N. cholana to other rt>ecies of 

Noetia is not clear. It does not appear to be particularly related to the lower Zorritos form N. stewarti, 

which is short and inflated, with high beaks whereas
SPECIES AND GENERA OF TERTIARY NOETINAE '

N. cholana is elongate, very little inflated, and with low 

beaks. It may prove to be related to N. retractata, which 

it more resembles in hinge and beak characters, although 

that species is much heavier and subquadrate rather 

than light and egg-shaped. The types of N. cholana 

are not well preserved, so that until better topotypes 

can be studied, its true relationships cannot be satisfactorily determined.

Distribution: Lower middle Miocene, middle Zorritos, Variegated bedSj Quebrada Tucillal, Zorritos, Peru.

Noetia retractata (Hanna and Israelsky) Olsson

Plate 5, figures 14, 15; plate 6, figures 5, 6

Area (Noetia) modesta Grzybowski, Neues Jahrb., Beilage Band 

12, p. 635, pi. 18, fig. 4, 1899 [not modesta Weinkel, 1863].

Area retractata Hanna and Israelsky, California Acad. Sci. Proc., 

4th ser., vol. 14, p. 61, 1925.

Area (Noetia) retractata. Olsson, Bull. Am. Paleontology, vol. 

19, no. 68, p. 76, pi. 4, fig. 2 [not fig. 8], 1932.

Shell subrhomboidal or subquadrate, inflated, high 

and rounded anteriorly, angulate posteroventrally; 

beaks moderately low, situated at about the posterior 

quarter or fifth of the hinge line; umbonesmoderately 

high and of medium breadth; umbonal ridge sharp and 

curving outward; posterior slope steep but frequently 

expanded at the margin; hinge line moderately long; 

ribs 35 or 36, wider than the interspaces and of about 

equal width all over the disk, very flat or even concave 

on the disk, more rounded on the posterior slope, less 

in relief ventrally; ligament almost wholly anterior; 

cardinal area produced a short distance behind the 

beaks but uncovered by ligament except for a small 

wedge under the beaks; teeth vertical centrally, Lshaped anteriorly, inclined posteriorly, the posterior 

row about two-thirds as long as the anterior row and 

gradually swinging away from the hinge line on a 

moderately broad plate. (Emended description.)

Holotype in Geological Institute of the Jagiellonian 

University, Krakow, Poland. Topotype (Axel Olsson 

collection, Gloversville, N. Y.), length 40 millimeters, 

height 33 millimeters, double convexity 28 millimeters.

Noetia retractata, is well characterized by its subquadrate outline, relatively long hinge line, and flat or 

concave ribs. It has been stated that N. retractata and 

N. macdonaldi would prove to merge into each other, 

but there is no evidence of this in any of the specimens 

examined. The ribs of N. macdonaldi are low and 

broadly rounded, with the anterior ribs frequently 

wider than the posterior ribs, and the interspaces very 

narrow and shallow. In N. retractata the ribs are flat 

or even concave, equisized, with the interspaces about 

half as wide and well denned. The umbones of N. 

retractata are lower and broader, the posteroventral 

margin less produced, the beaks less opisthogyrate, 

the break between the cardinal area and the adjoining 

part of the posterior slope less abrupt, and the posterodorsal margin more horizontal, with the posterior row

• of teeth less divergent from the hinge line. In addition, 

N. retractata probably does not attain the size of N.

\ macdonaldi.

Specimens furnished to me by Mr. Olsson from the

I upper Zorritos sandstone about 1 mile east of Punta

i Picos, Province of Tumbez, Peru (pi. 5, fig. 21), although not well preserved, appear to be more nearly 

related to N. ecuadoria than to N. retractata arid are

; referred to that species. It may be that these two 

species are connected by a series of intermediate forms. 

The relation of N. ecuadoria to N. macdonaldi is dis-

; cussed below, and if N. macdonaldi and N. retractata,

\ are related it may be through this intermediate species.

Grzybowski described this species as having 30 ribs,

but the photographs of the type obtained from the

University of Krakow show this statement to be an

error.

Distribution: Lower middle Miocene, upper Zorrito^ sandstone, Zorritos and Punta Picos, Peru.

Type locality: Zorritos.

Figured topotypes from a locality just southwest of Zorritos, 

Province of Tumbez, Peru.

Noetia ecuadoria MacNeil, n. sp.

Plate .5, figures 12, 13, 20

Shell subrhomboidal, moderately inflated, reminded 

anteriorly, sharply angulate posteroventrally, posterior 

margin nearly straight; beaks moderately low, situated 

at about the posterior fourth or fifth of the hinge line; 

umbones moderately high and of medium breadth; 

umbonal ridge carinate arid curving outward; posterior 

slope steep; ribs about 35, slightly wider than the interspaces, tending to be flat-topped arid level with the 

interspaces in adults, especially on the central ai d posterior part of the disk; interstitial ribs well developed 

on the ridge and posterior slope; ligament mostly anterior, extending a very short distance posteriorly, 

narrower beneath the beaks than centrally; cr.rdinal 

area extending a short distance posteriorly but mostly 

devoid of ligament; teeth inclined to the posterior, 

L-shaped anteriorly, the posterior row oblique to the 

hinge line and about three-quarters as long as the 

anterior row.

Holotype (in Axel Olsson collection, Gloversville, 

N. Y.), length 34 millimeters, height 27.5 millureters, 

convexity 12.5 millimeters.

This species appears to be related to and possibly 

descended from N. trinitaria or N. stewarti. It is intermediate in size between them arid similar to N. trinitaria 

in the sharpness of the ridge and elongation of tl a. posteroventral margin and in the anterior thickening of the 

shell. It differs from these two species in being broader 

across the disk, with lower umbones, more posterior 

beaks, and a narrower cardinal area posteriorly.

Noetia ecuadoria is probably closely related to N. macdonaldi on the other hand, although N. colombiana, next 

described, appears to be as closely related to that species
34 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

in some respects. The possibility of an intergradation 

between N. ecuadoria and N. retractata in the upper 

Zorritos has already been mentioned. N. ecuadoria 

may prove to be a key species which through interbreeding or direct evolution contributed to more than 

one contemporaneous or later species.

Distribution: Lower middle Miocene, Ecuador.

Type locality: Cueva de Angostura, Rio Santiago, Province of 

Esmeraldas, northern Ecuador.

Other occurrences: Miocene of Daule, Ecuador, near Estacada, 

Rio de la Balsa, Province of Guayas, Ecuador.

Doubtful identifications: Upper Zorritos formation, 1 mile 

east of Punta Picos, Province of Tumbez, Peru.

Noetia colombiana MacNeil, n. sp.

Plate 5, figures 10, 11

Shell subrhomboidal, moderately inflated, sometimes 

with a shallow medial sulcus, high and rounded anteriorly, angulate and considerably produced posteroventrally, posterior margin nearly straight; beaks low, 

situated at the posterior end of the hinge line; umbones 

low and full; umbonal ridge moderately sharp and 

curving strongly outward; posterior slope moderately 

expanded; hinge line of medium length; ribs about 32, 

ranging from 31 to 33, wider than the interspaces, low 

and rounded, becoming less elevated ventrally, those 

on the anterior part of the disk wider, sometimes 

much wider, than elsewhere; ligament wholly anterior, 

wider anterior to the beaks; a very narrow bare strip 

of the cardinal area posterior to the beaks; teeth inclined 

centrally and posteriorly, L-shaped anteriorly, the 

posterior row about half as long as the anterior row 

and oblique to the hinge line.

Holotype (U.S.N.M. 496544), length 31 millimeters, 

height 25.5 millimeters, convexity 12 millimeters.

This species, with its much-produced posteroventral 

region, has much the shape and size of N. ecuadoria 

but has lower and more posterior beaks, a shorter 

cardinal area posteriorly, and a tendency for the 

anterior ribs to be wider and lacks the anterior thickening of the shell. In beak and rib characters it approaches typical N. macdonaldi, but that form also has 

a much thickened anterior and is considerably larger 

and heavier. Thus N. ecuadoria has the thickened 

anterior and N. colombiana has the wide anterior ribs, 

both of which characterize the larger species N. macdonaldi and N. reversa, and when workable collections 

are obtained it will probably prove that both of these 

species contributed to the N. macdonaldi-reversa series.

Distribution: Middle Miocene, northern Colombia.

Type locality: Base of the Juan de Acosta, between Saco and 

Juan de Acosta, Atlantico Department, Colombia, U.S.G.S. 

11360.

Other occurrences: Between Piojo and Saco, half a mile south 

of Saco, Atlantico Department, Colombia, U.S.G.S. 11333.

Noetia mayensis Maury

Plate 5, figures 16, 17

Area (Noetia) mayensis Maury, Bull. Am. Paleontology, vol. 10. 

no. 42, p. 40, pi. 5, fig. 2, 1925.

Shell subrhomboidal and elongate, inflated, anterior 

rounded, posterior less sharply rounded and broadly 

produced, posteroventral margin angulate but not 

projecting; beaks low, situated at about the posterior 

quarter or fifth of the hinge line but about centrally 

with respect to the shell, owing to the elongate posterior; 

umbones low and broad; umbonal ridge moderately 

carinate; posterior slope expanded; ribs gbout 36, 

rounded and roughened by growth lines; interstitial 

ribs developed posteriorly; ligament wholly anterior 

to the beaks, narrower posteriorly owing to the low 

beaks; a moderate-sized portion of the cardinal area 

existing posterior to the beaks but uncovered by 

ligament; teeth vertical centrally, somewhat L-shaped 

anteriorly, smaller and sharper posteriorly, the posterior 

row about three-quarters as long as the anterior row 

and at first continuous with it but more posteriorly 

gently swinging away.

Holotype (in Paleontological Eesearch Institution, 

Ithaca, N. Y.), length 27 millimeters, height 17 millimeters, convexity 9 millimeters.

If the hinge of this species were not visible, it might 

be mistaken for a member of the Atlantic g^oup, because of its elongate shape and roughened rculpture. 

The hinge line is not produced posteriorly, and the 

ligament is extremely short posterior to tH beaks, 

however. N. mayensis is probably closely related to 

N. mauryae, n. sp., from Colombia, but the relationship 

of these two to other species is not clear. N. cholana 

is similar in its broad, elongate posterior and nearly 

horizontal posterior row of teeth and may or may not 

be related.

Distribution: Lower middle Miocene, Brasso beds Trinidad. 

Type locality: Near junction of Mayo and Couva main roads, 

west-central Trinidad.

Noetia mauryae MacNeil, n. sp.

Plate 5, figures 18, 19

Shell subrhomboidal and elongate, inflated, rounded 

anteriorly, produced posteroventrally, posterior margin 

arcuate; beaks low, situated at nearly the posterior end 

of the hinge line; umbones low, moderately l^oad and 

inflated; umbonal ridge carinate, curving slightly outward; posterior slope moderately expanded; hinge line 

of medium length; ribs about 34, of about the same 

width as the interspaces, low and rounded or with a 

slight tendency to be flat-topped ventrally; interstitial 

ribs well developed posteriorly; ligament wholly anterior to the beaks, wider anteriorly; a narrovr strip of
SPECIES AND GENERA OF TERTIARY NOETINAE 35

the cardinal area bare posteriorly; teeth inclined centrally and posteriorly, L-shaped anteriorly, the posterior 

row about two-thirds as long as the anterior row and 

moderately divergent, following the arcuate posterodorsal margin.

Holotype (U.S.N.M. 496545), length 29.5 millimeters, height 23.5 millimeters, convexity 11.5 millimeters.

Noetia mauryae is probably very closely related to the 

Trinidad species N. mayensis, from which it differs in 

being higher and having smoother ribs. The shells of 

these two species are comparatively thin, without any 

anterior thickening, thus differing from the majority 

of species of Noetia in this respect. N. colombiana, 

which likewise is unthickened anteriorly, is not very 

closely related, however. Both N. mayensis and N. 

mauryae have well-rounded posterior margins, and the 

posterior row of teeth is more nearly in line with the 

hinge line than in most other species, although N. 

cholana is likewise characterized by this condition.

Distribution: Middle Miocene, upper Saco, northern Colombia.

Type locality: "Lookout" point on road just north of Tubard, 

slightly below the formation exposed in Tubard and above the 

Piojo limestone, Atlantico Department, Colombia, U.S.G.S. 

11251.

Other occurrences: Road from Tubara to Los Perdices, 300 

feet southeast of "lookout" point north of Tubard, Atlantico 

Department, Colombia, U.S.G.S. 11346.

Noetia atratoensis MacNeil, n. sp.

Plate 5, figures 24, 25

Shell subtrigonal, short, much inflated, anterior 

rounded, angulate and produced posteroventrally, posterior margin nearly straight; beaks of medium height, 

divergent, strongly opisthogyrate and recurving over 

the cardinal area, situated at nearly the posterior end 

of the hinge line; umbones moderately narrow'but very 

high and inflated, accounting for over a third of the 

height of the shell; umbonal ridge sharp and curving 

outward, forming the most inflated part of the disk; 

posterior slope very steep; hinge line moderately short; 

ribs about 30, wider than the interspaces in1 adults, 

becoming flat and level with the interspaces ventrally, 

especially centrally; interstitial ribs fairly well developed posteriorly; ligament anterior except for a narrow 

posterior wedge; a very narrow strip of the cardinal 

area left bare posteriorly; teeth vertical or slightly 

inclined centrally, L-shaped anteriorly, long and 

inclined posteriorly, the posterior row diverging sharply 

from the hinge line.

Holotype (U.S.N.M. 496546), length 23 millimeters, 

height 21.5 millimeters, convexity 12.5 millimeters.

This interesting little species is characterized by its 

extremely high and inflated umbones. The large posterior teeth on the type may be somewhat abnormal. 

In shape and sculpture this species most closely 

resembles N. macdonaldi alta, described below, but it is

much smaller and less opisthogyrate and has a relatively 

longer hinge line. The umbones of N. atratoensis 

account for about a third of its height. This species 

has only about 30 ribs, which represents about the 

minimum number for Noetia.

Distribution: Middle Miocene, Atrato River district, Colombia.

Type locality: Quebrada Limon, Atrato River district, Antioquia Department, Colombia, U.S.G.S. 11570.

Other occurrences: Quebrada Mata Perro, U.S.G.S. 11556; 

Quebrada Mata Tigre, U.S.G.S. 11558, Atrato River district, 

Antioquia Department, Colombia.

Noetia macdonaldi Dall

Plate 6, figures 10-13

Area (Noetia) macdonaldi Dall, Smithsonian Misc. Coll., vol. 59, 

no. 2, p. 9, 1912; U. S. Nat. Mus. Proc., vol. 66, p. 5, pi. 

17, fig. 9, 1925.

Area (Noetia) macdonaldi subreversa Olsson, Bull. Am, Paleontology, vol. 9, no. 39, pt. 2, p. 194, pi. 25, figs. 6.. 7, 1922.

Shell subtrigonal, inflated, anterior high and rounded 

posterior margin nearly straight, posteroventral margin 

sharply angulate and produced; beaks low and situated 

at about the posterior end of the hinge line; umbones 

moderately high and of medium breadth; umbonal 

ridge curving outward, sharply carinate; posterior slope 

flattened and steep; ribs 38 to 39, rounded and higher 

and about as wide as the interspaces posteriorly, but 

much broader and lower on the anterior part of the 

disk, becoming less elevated and flatter ventrally; 

ligament wholly anterior to the beaks, higher at the 

center of the hinge line owing to the low beaks; a very 

narrow strip of bare cardinal area posterior to the beaks; 

teeth inclined centrally, becoming L-shaped anteriorly, 

inclined posteriorly, the posterior row about half as 

long, ventrally oifset from and diagonal to the, hinge 

line. (Emended description.)

Holotype (U.S.N.M. 214344), length 56 millimeters, 

height 44 millimeters, convexity 22.5 millimeters.

An error has crept into the literature concerning this 

species owing to the fact that the hinge was never 

figured. Specimens from the Banana River anel nearby 

in Costa Rica are varied and may form a uniformly 

graded series, but at present not enough specirr^ns are 

at hand to say definitely whether or not this is so. Two 

extremes can be selected which appear to be quite distinct—one with high beaks, narrow umbones, and a 

much produced posteroventral margin, and th°s other 

with low beaks, broader umbones, and a more expanded 

posterior slope, giving the shell a less produced appearance posteroventrally. In addition the ribs in the lowbeaked form are more rounded and less uniform in size, 

ranging from equisized all over the disk to broad, 

rounded, and much wider anteriorly than posteriorly. 

The relationship of these forms is not clear. It is probable that the width of the anterior ribs in the low-beaked 

forms is a matter of individual variation, as it is in the 

species N. colombiana, this character not being- of the 

fixed nature that it is in the Recent species N. reversa.
36 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Olsson believed that the high-beaked type was the typical 

form and gave the subspecific name subreversa to the 

low-beaked form. Actually, Ball's type has low beaks 

and wide .anterior ribs, so that the name subreversa is a 

synonym. The high-beaked form is here given the 

subspecific name alia.

The holotype of N. macdonaldi came from the lowest 

bed along the Banana River and is noteworthy in being 

by far the largest specimen in the MacDonald collection. 

Large numbers of smaller specimens from successively 

higher beds seem to indicate that there is a decrease in 

the number of ribs from the lower to the upper part of 

the section, although this must be proved by rib counts 

on shells of the same size. The type has 39 to 40 ribs, 

whereas specimens from successively higher beds 

gradually decrease to an average of about 32.

In addition, the holotype is the only specimen from 

the type locality which shows a good development of 

the wide anterior ribs, although this character is one 

which is not conspicuous until the shell is about half 

or two-thirds grown, so that the smaller specimens do 

not show much in this respect. A specimen somewhat 

larger than the holotype from a locality 40 miles northnorthwest of Quibdo, in the Atrato River Valley, western Colombia, has wide ribs and narrow interspaces on 

the central and anterior part of the disk. There is 

reason for considering the species with wide anterior 

ribs to be closely related, and if they are, N. colombiana, 

N. macdonaldi, and N. reversa form a more or less natural 

group. These are the only species in which this character has been observed, and in N. colombiana, and probably hi N. macdonaldi, it appears to be a matter of 

individual variation, but in N. reversa it is constant. 

Noetia ecuadoria is closely related to N. macdonaldi and 

might easily be confused with it. The beaks of N. 

ecuadoria are more central and less ppisthogyrate, the 

ribs are narrower and less rounded, and the posteroventral margin is .usually more produced.

Specimens from Colombia which have been previously 

identified as N. macdonaldi are not exactly typical, and 

it is thought desirable to recognize one of them by name. 

Whether this is really a subspecies of N.- macdonaldi 

remains to be proved, but for the time being it is so 

regarded. The specimen from the locality 40 miles 

north-northwest of Quibdo is the most typical specimen 

of N. macdonaldi seen from Colombia. Its hinge is 

identical .with that of the type, but the shell differs in 

being more elongate, with a less carinate umbonal ridge. 

Whether this is a matter of individual variation or is 

peculiar to specimens more than several hundred miles 

distant from the type- locality remains to be seen.

Distribution: Upper middle Miocene, Gatun formation and 

its equivalents in Costa Rica, Panama, and Colombia.

Type locality: About a quarter of a mile south of the Banana 

River and about 5J4 miles inland from the Caribbean (supposedly 

low in the fossiliferous beds that crop out in this region), Costa 

Rica, U.S.G.S. 5882m.

Other occurrences: At numerous localities along the.Banana 

River east of the type locality (supposedly from progressively 

higher beds), Costa Rica, U.S.G.S. 5&S2n-a; 2 miles east of Juan 

de Acosta, Atlantico Department, Colombia, U.S.G.S. 11321; 

Rio Tagachi, 18 miles west of its junction with Rio Atrato and 40 

miles north-northwest of Quibdo, Antioquia IN apartment, 

Colombia, U.S.G.S. 11560. Another specimen is labeled 

"coastal traverse, 2Yz miles west of Rio San Juan, .Antioquia 

Department", U.S.G.S. 11659. According to all available maps 

the Rio San Juan does not enter Antioquia Department, but if 

the specimen is from somewhere along the Rio San Juan it is the 

southernmost locality at which .1 have, been able to identify 

this species.

Noetia macdonaldi alta MacNeil, n. subsp. 

Plate 6, figures 1, 2, 8, 9

Area (Noetia) macdonaldi. Olsson, Bull. Am. Paleontology, vol. 9, 

no. 39, pt. 2, p. 194, pi. 25, figs. 4, 5, 1922.

This subspecies has an aspect quite different from 

that of the typical form, being much shorter, with higher 

beaks and narrower and higher umbones, a wider cardinal area posteriorly, and a much steeper and less 

expanded posterior slope. The ribs are about as wide 

as the interspaces, are rounded and well defined in the 

young stages, but become wider, flat, and low, being 

about level with the interspaces, in adults. There is 

some variety in the length of the hinge line in this form 

and also some variety in the angulation and extent to 

which the posteroventral region is produced.

Holotype in Paleontological Research Institution, 

Ithaca, N. Y. Figured specimen (U.S.N.M. 496548), 

length 30 millimeters, height 29 millimeters, convexity 

15.5 millimeters. A larger specimen (U.S.N.M. 

496549), length 36+miUimeters, height 35 +millimeters, 

convexity 20.5 millimeters.

The relationship of this subspecies to the typical form 

is not clear, and it seems to be more related to some 

Colombian forms than to the holotype and paratypes of 

TV. macdonaldi from the Banana River. Noetia atratoensis from western Colombia is closely related but considerably smaller, with a-, longer hinge line and higher 

umbones. It resembles in size and shape another subspecies from Colombia, AT. macdonaldi truncata, more 

than the typical form but differs from that subspecies 

in having wider and much less elevated ribs.

Type locality: "Hill No. 3", Banana River, Costa Rica 

(Olsson).

Other occurrences: Rio Bananito, about S% to 4 miles from the 

Caribbean (supposedly equivalent to some of the upper fossiliferous beds along the Banana River), Costa Rica, U.S.G.S. 

5883c; mouth of Cumbre Creek, Estrella River, El Porvenir 

station, Costa Rica, U.S.G.S. 8056.

Noetia macdonaldi truncata MacNeil, n. vrr.

Plate 6, figures 3, 4

This variety from Colombia differs from the typical 

form in being much shorter, with higher beaks, narrower 

umbones, and a more rounded umbonal ridge. The
SPECIES AND GENERA OF TERTIARY NOETINAE 37

ribs are very regular and comparatively narrow, being 

about as wide as the interspaces, rounded, and relatively 

high. The interstitial ribs are fairly well developed.

The beaks are not as high as in AT", macdonaldi alia, 

the posteroventral margin is not as produced, and the 

posterior slope is not as steep. The ribs of AT", macdonaldi truncata are narrower and higher than in N. 

macdonaldi alta.

Holotype (U.S.N. M. 496550), length 28 millimeters, 

height 27 millimeters, double convexity 25.5 millimeters. 

The paratype is less perfect but larger (U.S.N.M. 

496582).

Distribution: Middle Miocene, Colombia.

Type locality: Near San Andreas, Bolivar Department, 

Colombia, U.S.G.S. 10151.

Other occurrences: Quebrada Pajuil, west of Sinu River, 

Bolivar Department, Colombia, U.S.G.S. 11628.

Noetia turbacensis MacNeil, n. sp.

Plate 6, figures 14, 15

Shell subrhomboidal, thick, inflated, rounded anteriorly, more broadly rounded posteriorly; posteroventral 

margin sharply rounded and moderately produced; 

beaks low, situated at about the posterior fifth or sixth 

of the hinge line; umbones low and broad; umbonal 

ridge sharp but not curving outward, forming the most 

inflated part of the shell; posterior slope of moderate 

expansion; ribs about 37, slightly wider than the interspaces and very regular in size and spacing all over, 

rounded posteriorly, flatter and less elevated on the 

disk; interstitial ribs well developed posteriorly; ligament wholly anterior to the beaks, narrow throughout 

but slightly higher at the center, owing to the low beaks; 

cardinal area extending a short distance posteriorly but 

uncovered by ligament; teeth inclined and crowded 

centrally, L-shaped anteriorly, inclined posteriorly, the 

posterior row about three-fourths as long as the anterior 

row and slightly oblique to the hinge line.

Holotype (U.S.N.M. 496551),Iength21.5millimeters, 

height 18.5 millimeters, convexity 9.5 millimeters.

This species is characterized by its small, subquadrate form, considerable inflation, and very thick shell. 

The shell is much thicker than in any other species of 

this size, and the thickening is uniform rather than just 

anteriorly, as in many other species. The ribs are very 

uniform and smooth in appearance.

Distribution: Upper (?) Miocene, Colombia.

Type locality: Shale in creek bed just below dam, one-eighth 

of a mile northeast of mud volcanoes, Turbaco, Bolivar Department, Colombia, U.S.G.S. 8084.

MIOCENE OR PLIOCENE SPECIES 

Noetia gardnerae MacNeil, n. sp.

Plate 6, figures 16, 17

Shell subrhomboidal, thickened, moderately inflated, 

anterior rounded, posterior straight or slightly emarginate, sharply rounded but not produced posteroventrally,

less sharply rounded posterodorsally; beaks verr low, 

situated at about the posterior fifth of the cardinal area 

but just anterior of center with respect to the shell, 

owing to the extended posterior; umbones moderately 

low and not very full; umbonal ridge sharply rounded, 

curving gently outward; hinge line of medium length; 

ribs about 36 to 38, smooth, rounded, and very regular, 

of about the same width as the interspaces; interstitial 

ribs present posteriorly; ligament wholly anterior to the 

beaks, narrow, but wider centrally than beneath the 

beaks; a moderate portion of the cardinal area posterior 

to the beaks but devoid of ligament; teeth small and 

vertical centrally, L-shaped anteriorly, inclined posteriorly, the posterior and anterior rows subequal in 

length, and the posterior row almost horizontal and in 

line with the anterior row, owing to the high, elongate 

posterodorsal margin.

Holotype (U.S.G.S.496552),length 12.5± millimeters, 

height 10 ± millimeters, convexity 4 millimeters.

This species is closely related to AT", sheldoniana, from 

which it differs in being somewhat longer, with a tMcker 

shell and a tendency to emargination posteriorly. The 

hinge is heavier, a condition which can usually be 

correlated with the thickness of the shell.

Noetia gardnerae is of interest because of the fact 

that it is the only true Noetia to obtain a foothold in 

the northern Gulf region, the type having been obtained 

from an oil well near Houston, Tex., at a depth of 

1,700 feet in sediments of very late Miocene or early 

Pliocene age.

Especial attention is called to the possibility of 

confusing this species with young specimens of Eontia 

ponderosa that have been obtained from wells in Louisiana at depths of nearly 2,000 feet. Owing to the much 

more rapid sinking in this region, however, these beds 

are probably fairly late Pleistocene.

Distribution: Upper Miocene or Pliocene, Texas.

Type locality: From an oil well near Houston, Tex., at a 

depth' of 1,700 feet.

Doubtful identifications: Specimens obtained at a depth of 

2,552 to 2,871 feet, from the deep well at Galveston, Tex.,, in 

sediments believed to be of upper Miocene age, were identified 

by Harris 10 as Area ponderosa var. carolinensis Conrad, The 

specimens used for comparison came from Natural Well, North 

Carolina, which are here referred to Eontia trigintinaria (Conrad). 

It is not impossible that the form of E. trigintinaria occurring 

in the Cancellaria zone of the Choctawhatchee formation of 

western Florida ranged as far west as Galveston, but it i^ more 

likely that the Galveston form is a Noetia. This conclusion 

should, of course, be verified.

PLIOCENE SPECIES

Noetia sheldoniana Maury 

Plate 6, figures 18, 19

Area (Noetia) sheldoniana Maury, Acad. Nat. Sci. Philadelphia 

Jour., 2d ser., vol. 15, p. 43, pi. 8, figs. 10, 11, 1912; 

Bull. Am. Paleontology, vol. 10, no. 42, p. 39, pi. 8, fig. 11, 

1925.

10 Harris, O. D., Texas Geol. Survey 4th Ann. Kept., pp. 93, 94, 118, lf°2; Bull. 

Am. Paleontology, vol. 1, no. 3, p. 6,1895.
38 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1937

Shell subrhomboidal, thin, moderately inflated, anterior rounded, posterior straight and vertical, sharply 

rounded posteroventrally and less sharply posterodorsally; beaks low, situated near the posterior end of 

the hinge line but nearly centrally with respect to the 

shell; umbones low, moderately broad; umbonal ridge 

sharply rounded, curving gently outward; hinge line 

of medium length; ribs about 38, smooth, rounded, and 

very regular, of about the same width as the interspaces; ligament wholly anterior to the beaks, narrow 

but wider centrally than under the beaks; cardinal area 

extending a short distance posteriorly but bare; interstitial ribs present posteriorly; teeth small and nearly 

vertical centrally, L-shaped anteriorly, inclined posteriorly, the posterior row about three-fourths as long as 

the anterior row and diverging at a narrow angle from 

the hinge line. (Emended description.)

Holotype (in Museum of Geology, Cornell University, 

Ithaca, N. Y., no. 38296), length 15 millimeters, height 

13.5 millimeters, convexity 6 millimeters.

This species is probably the most perfect homeomorph 

of the Atlantic shell Eontia ponderosa, the adults of 

which it almost perfectly simulates in shape. Shells of 

this size, however, are quite distinct, juveniles of E. 

ponderosa being more elongate. Noetia sheldoniana 

has about 38 ribs, as opposed to 25 to 28 for Eontia 

ponderosa, and the usual characteristics which distinguish the Pacific group can be noted—the considerably 

shorter posterior portion of the ligament and the deeper 

and longer posteroventral crenulations of the inner 

margin.

Noetia sheldoniana is probably related to N. turbacensis, which it resembles somewhat in shape, but it 

has a much thinner shell. It is also related to the new 

species from Texas, N. gardneri, just described.

Noetia sheldoniana and N. gardnerae are the last 

known species of Noetia in the Gulf and Caribbean 

region, and they represent the extinction of a branch 

of the genus which gained access to this region in middle 

or late Miocene time. The difference between these 

species and the Noetia reversa stock and the absence 

of the latter from the Caribbean region druing the 

Pliocene epoch lend strong support to the theory that 

there has been no free passage between the Pacific and 

Caribbean since Miocene time.

Distribution: Upper(?) Pliocene, Trinidad. 

Type locality: Along shore 1,000 feet west of Brighton pier, 

in black asphaltic marl, Trinidad.

PLEISTOCENE SPECIES

Noetia magna MacNeil, n. sp.

Plate 6, figures 20, 21

Area (Noetia) reversa. Grzybowski, Neues Jahrb., Beilage-Band 

12, p. 134, pi. 17, figs. 1, la, 1899.

The form from Paita which Grzybowski referred to 

Noetia reversa is much like it in shape but differs in

size, being about twice as large, and in having more 

ribs, 40 to 42, as compared with 35 for N. reversa. 

Photographs of Grzybowski's specimen show it to have 

more elevated ribs, with less tendency to widen on the 

anterior part of the disk, although this might be a 

matter of individual variation. It compares with N. 

reversa in having strongly opisthogyrate, low, and very 

posterior beaks, these being at or even behind the 

posterior end of the cardinal area, the two species being 

extremes in this respect.

A Noetia figured by Olsson n as Area (Noetia} 

reversa, subsp., compares with Grzybowski's specimen 

in size and for the time being might be referred to the 

new species, although Olsson states that Grzybowski's 

specimen is from the Mancora Tablazo beds, of Pleistocene age, whereas his specimen from the mouth of 

Quebrada Tucillal is supposedly from the Tumbez 

formation, of late Miocene age.

Grzybowski's specimen measures over 80 millimeters 

in length, and Olsson gives lengths of 80 and 83 millimeters for two specimens of his form, whereas he reports 

the largest specimen of N. reversa seen by him to be 

45 millimeters. The average runs less than that, the 

largest specimen in the U. S. National Museum being 

only 40 millimeters. Such a length makes N. magna 

the largest shell in the Noetinae, the Recent Eontia 

ponderosa of the Atlantic group rarely attaining a 

greater length than 65 millimeters.

Holotype (in Geological Institute of the Jagiellonian 

University, Krakow, Poland), length 80 millimeters, 

height 72 millimeters, convexity 37 millimeters. The 

margins are eroded, so that only approximate measurements can be made.

Distribution: Pleistocene(?), Peru. 

Type locality: Mancora Tablazo beds, Paita, Peru. 

Doubtful identifications: Upper Miocene, Tumbez formation, 

Quebrada Tucillal, Tumbez, Peru (Olsson).

RECENT SPECIES

Noetia reversa (Sowerby) H. and A. Adams

Plate 6, figures 7, 22, 23

Area reversa Sowerby, Zool. Soc. London Proc., vol. 1, p. 20,

1833. 

Aroa hemicardium Koch, in Philippi, Abbildungen und Beschreibungen Conchylien, vol. 1, p. 43, Area, Tafel 1, fig. 1,

1849. 

Area reversa. Carpenter, Catalog of the Reigen collection of

Mazatlan mollusks, p. 136, 1857. 

Noetia triangularis Gray, Annals and Mag. Nat. History, 2d

ser., vol. 19, p. 371, 1857. 

Noetia reversa. H. and A. Adams, Genera of Recent Mollusca,

vol. 2, p. 536, v. 3, pi. 125, figs. 1, la, 1858. 

Area (Noetia) reversa. Lamy, Jour, conchyliolog'e, vol. 55,

p. 298, 1907.

Dall, U. S. Nat. Mus. Proc., vol. 37, p. 253, 1910. 

Maury, Paleontographica americana, vol. 1, no. 4, p. 9,

pi. 1, figs. 7, 11, 1922.

" Olsson, Axel, Bull. Am. Paleontology, vol. 19, no. 68, p. 77, pi. 3, fig. 1, 1932.
SPECIES AND GENERA OF TERTIARY NOETINAE 39

Shell subrhomboidal or trigonal, moderately inflated, 

rounded anteriorly, posterior margin nearly straight, 

sharply rounded and produced posteroventrally; beaks 

low and situated at the posterior end of the cardinal 

area, or even behind it; umbones low and moderately 

broad; umbonal ridge subcarinate and curving gently 

outward; posterior slope flat and steep; ribs about 35, 

higher and narrower posteriorly, much wider than the 

interspaces and about level with them on the anterior 

part of the disk in adults; ligament entirely anterior to 

the beaks, completely covering the cardinal area, which 

likewise is entirely anterior to the beaks; teeth inclined 

centrally, L-shaped anteriorly, inclined posteriorly, the 

posterior row short and ventrally offset from the 

anterior row and sharply diverging from it. (Emended 

description.)

Figured specimen (U.S.N.M. 101954), length 40 

millimeters, height 33 millimeters, convexity 16 millimeters.

This is the sole surviving species of the large genus 

Noetia, but despite its rather limited occurrence it is 

probably as well known as any other species in the 

Recent fauna because of the attention focused upon it 

by early systematists. It is not as large as some of its

nearest relatives, particularly N. magna and N. r>.acdonaldi. It appears to be less variable than N. wacdonaldi, especially in the width and low elevation of 

the ribs on the anterior part of the disk. It shares 

with N. magna the distinction of having the most 

posterior beaks in the genus.

Noetia trianguLaris Gray, the type of Noetia, has 

been variously interpreted as Area reversa Sowerby 

and Area ponderosa Say, a distinction which did not 

particularly matter until it became evident, as sh^wn 

in this paper, that the two species represent groups of 

long-standing independence. The photographs of N. 

triangularis, forwarded to me by Dr. Philip W. Rein] <vrt, 

who obtained them from Dr. L. R. Cox, of the Brtish 

Museum, show beyond doubt that N. triangularis is a 

synonym of Area reversa.

Distribution: Pleistocene (?) and Recent, Gulf of California 

to Peru.

ADDENDA

Area delgada Lowe (San Diego Soc. Nat. Hist. 

Trans., vol. 8, no. 6, p. 16, pi. 1, fig. 2, 1935), from 

Manzanillo, Colima, Mexico, may be an Eontia related 

to E. centrota, but as the hinge is not figured it is 

impossible to say.

PLATES 1-6

41
PLATE 1

FIGURES 1-4. Scapularca subglobulosa (Wood), X 5, Bartonian, Highcliff, Barton, England. (After Wood.)

FIGURES 5, 6. Scapularca interposita (Deshayes), X 3, lower Lutetian, Herouval, Seine-et-Oise, France, U.S.N.M. 496S06.

FIGURES 7, 8. Scapularca scapulina (Lamarck), X 3, Lutetian, Villiers, Seine-et-Oise, France, U.S.N.M. 496505.

FIGURES 9, 10. Eontia okeni (Mayer), X 1}£, Aquitanian, Merignac (Lorient), France. (After Cossmann and Peyrot.)

FIGURES 11, 12. Eontia centrota (Guppy), X 1%, lectotype, Pliocene, Matura Bay deposits, eastern Trinidad, U.S.N.M. 496508.

FIGURES 13, 14. Sheldonella maoica (Maury), X 1%, lower middle Miocene, Cercado formation, 3 miles above Cercado de Mao,

Santiago Province, Dominican Republic, U.S.N.M. 496507.

FIGURES 15, 16. Eontia bisulcata (Lamarck), X 1% Recent, Miranda district, State of Falcon, Venezuela, U.S.N.M. 496509. 

FIGURES 17, 18. Sheldonella (Paranoetia) cafria (Bartsch), X IK, topotype, Recent, Port Alfred, South Africa, U.S.N.M. 249849. 

FIGURES 19, 20. Eontia olssoni (Sheldon and Maury), X 2, holotype, Recent, Bucaru, Los Santos Province, Panama. 

FIGURES 21, 22. Sheldonella (Paranoetia) lateralis (Reeve), X lYz, Recent, Manila Bay, Philippine Islands, U.S.N.M. 248983. 

FIGURES 23, 24. Eontia indie mansfieldi MacNell, n. subsp., X 1, holotype, upper Miocene, Ecphora zone, Choctawhatchee formation, Jackson Bluff, Leon County, Fla., U.S.N.M. 371122. 

FIGURES 25-28, 30, 31. Eontia indie (Say), X 1, upper Miocene, zone 2> Yorktown formation, Virginia: 25, Chama-\ taring bed,

about \% miles east of Williamsburg, U. S. N. M. 496510; 26, bed a, iy2 miles below Yorktown, U.S.N.M. 496512;

27, bed c, Bellefield, just below Felgates Creek about 4^ miles above Yorktown, U.S.N.M. 496517; 28, bed /,

Colonial limekiln, about 3 miles above Yorktown, U.S.N.M. 496511; 30, interior, showing raised muscle scars, bed

/, half a mile below Yorktown; 31, hinge, bed c, 1 mile below Yorktown. 

FIGURE 29. Eontia indie suffolkensis MaoNeil, n. var., X 1, holotype, upper Miocene, Yorktown formation, upper bed at Rock

Wharf, 4 miles N. of Smithfield, Va., U.S.N.M. 496514. 

FIGURES 32,.33. Eontia trigintinaria (Conrad) subsp.(?), X 1, upper Miocene, Cancellaria zone, Choctawhatchee formation, borrow

pit, Jackson Bluff, Leon County, Fla., U.S.N.M. 496521. 

FIGURES 34-36. Eontia indie yorkensis MacNeil, n. var., X 1: 34, 35, holotype, upper Miocene, Yorktown formation, upper part of

C/iamo-bearing bed, about \% miles east of Williamsburg, Va., U.S.N.M. 496515; 36, paratype, Dinwiddie, Va.,

U.S.N.M. 496518. 

FIGURES 37, 38. Eontia trigintinaria (Conrad), X 1, upper Miocene, Duplin marl, Darlington Court House, Darlington, S. C.,

U.S.N.M. 496583. 

42
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 1

TERTIARY NOETINAE.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 2

11

TERTIARY NOETINAE.
PLATE 2

FIGURES 1, 2. Eontia trigintinaria filosa (Conrad), X 1, neotype, upper Miocene, Yorktown formation, Sullivan's marl pits, f miles

east of Snow HiU, Greene County, N. C., U.S.N.M. 496516. 

FIGURES 3, 4. Eontia trigintinaria (Conrad), X 1, upper Miocene, Duplin marl, Sullivan's marl pits, 8 miles east of Snoyr Hill,

Greene County, N. C., U.S.N.M. 497009. 

FIGURES 5, 6. Eontia carolinensis (Conrad), X 1, upper Miocene, uppermost part of Yorktown formation, middle bed at Colerain

Landing, Chowan River, Bertie County, N. C., U.S.N.M. 496519. 

FIGURES 7, 8. Eontia lumberensis MacNeil, n. sp., X 1, holotype, upper Miocene, upper part of Duplin marl, 2% miles east o* Fairmont, Robeson County, N. C., U.S.N.M. 496520. 

FIGURE 9. Eontia limula (Conrad), X 1, topotype (?), Pliocene, Croatan sand, 2 miles below James City, Craven County, N. C.,

U.S.N.M. 496522. 

FIGURE 10. Eontia tillensis MacNeil, n. sp., X 1, holotype, Pliocene, Waccamaw formation, Tillys Lake, Waccamaw River, Horry

County, S. C., U.S.N.M., 496527. 

FIGURE 11. Eontia variabilis quadrata MacNeil, n. var., slightly reduced, holotype, Pliocene, Waccamaw formation, Walkers Bluff,

Cape Fear River, 18 miles east-southeast of Elizabethtown, N. C., U.S.N.M. 496523. 

FIGURES 12-15. Eontia variabilis MacNeil, n. sp., X 1, Pliocene, Waccamaw formation: 12, holotype, Neills Eddy Landing, 5 miles

northeast of Acme, Columbus County, N. C., U.S.N.M. 496524; 13,14, paratypes, Wilmington, N. C., U.S.N.M.

496578, 496579; 15, paratype, Walkers Bluff, Cape Fear River, 18 miles east-southeast of Elizabethtown, N. C.,

U.S.N.M. 496525. 

FIGURE 16. Eontia cf. E. variabilis MacNeil, n. sp., X 1, Pliocene, Caloosahatchee marl, marl pit south of Airport, De Leon Springs,

Volusia County, Fla., U.S.N.M. 496526.

43
PLATE 3

FIGTJEES 1, 2. Eontia plaiyura (Dall), X 1, Pliocene, Caloosahatchee marl, Alligator Creek, just north of Acline, Charlotte County, 

Fla.: 1, lectotype, U.S.N.M. 496529; 2, paratype, U.S.N.M. 496528.

FIGTJEE 3. Eontia playtura (Dall) var., X 1, Pliocene, Caloosahatchee marl, near head of Prairie Creek, a tributary of Shell Creek, 

Charlotte County, Fla., U.S.N.M. 496530.

FIGTJEE 4. Eontia caloosana MacNeil, n. sp., X 1, holotype, Pliocene, Caloosahatchee marl, 6 miles northwest of Clewiston, Hendry 

County, Fla., U.S.N.M. 496531.

FIGTJEE 5. Eontia variabiKs clewistonensis MacNeil, n. var., X 1, holotype, Pliocene, Caloosahatchee marl, upper bed, 6 miles northwest of Clewiston, Hendry County, Fla., U.S.N.M. 496532.

FIGTJEE 6. Eontia veroensis MacNeil, n. sp., X 1, holotype, Pleistocene, Vero, St. Lucie County, Fla., U.S.N.M. 496580.

FIGTJEES 7, 8. Eontia palmeri MacNeil, n. sp., X 1, Pleistocene; 7, holotype, Wailes Bluff, near Cornfield Harbor, Potomac River, 

St. Marys County, Md., U.S.N.M. 496533; 8, HeislerviUe, Cumberland County, N. J., U.S.N.M. 496581.

FIGTJEE 9. Eontia ponderosa (Say) (Murdock form), X 1, Pliocene (?), 1.6 miles northwest of Murdock, Charlotte County, Fla., 

U.S.N.M. 496534.

FIGTJEE 10. Eontia ponderosa (Say), X 1, Pleistocene, Bradenton, Manatee County, Fla., U.S.N.M. 496535.

FIGTJEES 11, 12. Eontia ponderosa (Say), X 1, Recent, Florida, U.S.N.M. B1055. 

44
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 3

TERTIARY NOETINAE.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 4

22

TERTIARY NOETINAE.
PLATE 4

FIGURES 1-3. Protonoetia nigeriensis (Newton), X 1, middle Eocene, Ameki, Omobialla district, southern Nigeria: 1, 3, topot;*pe,

II.S.N.M. 496536; 2, lectotype, British Museum. 

FIGURES 4-8. Noetiopsis woodringi MacNeil, n. sp., X 1, middle Eocene, near mouth of the Tonosi River, Los Santos Province,

Panama: 4, topotype, Axel Olsson collection, Gloversville, N. Y.; 5, 6, paratype, U.S.N.M. 496538; 7, 8, holot;rpe,

TI.S.N.M. 496537. 

FIGURES 9-11. Arginopsis sullanensis (Woods), X 1, upper Eocene, Hacienda Saman, Rio Chira, Piura Department, Paita dist-ict,

Peru, TI.S.N.M. 496539.

FIGURES 12, 13. Arginella samanensis (Olsson), X 1/4, topotype (?), upper Eocene, Hacienda Saman, Rio Chira, Piura Department, Paita district, Peru, U.S.N.M. 496540. 

FIGURE 14. Arginella puntabravoensis (Olsson), X 1/4 holotype (after Olsson), Oligocene, Mancora formation, Punta Bravo grits of

Punta Bravo, Peru. 

FIGURES 15, 16. Arginella ovalis MacNeil, n. sp., X 3, Oligocene (?), between Arroyo Mancamajon and Ovejas, Bolivar Department,

Colombia: 15, holotype, U.S.N.M. 496541; 16, paratype, U.S.N.M. 496542.

FIGURES 17, 18. Noetia pondaungensis Cotter, X 1, holotype, upper Eocene, Pondaung sandstones, Burma. (After Cotter.) 

FIGURES 19-21. Noetia nagaoi MacNeil, n. name, fig. 19, slightly reduced; fig. 20, X 1; fig. 21, enlarged, holotype, upper Eoc?ne,

Doshi beds, Asakura coal field, Chikuzen Province, Japan.

FIGURES 22, 23. Noetia molengraffi, (Martin), X 1, lectotype (fig. 22 is printed in reverse), upper Eocene, Nanggulan, Java.

45
PLATE 5

FIGURES 1, 2. Noetia stewarti MacNeil, n. sp., X l/^, holotype, lower Miocene, transitional beds between Heath shales and lower

Zorritos sandstone, Quebrada Boca Pan, at'Zapotal, just south of Vacura, Tumbez Province, Peru. 

FIGURES 3, 4. Noetia manzanillae Maury, X 1 Yz, holotype, lower Miocene, Manzanilla formation, north of Manzanilla Po?nt, northeast

coast of Trinidad. 

FIGURES 5, 6. Noetia trinitaria (Guppy), X 1, lectotype, lower Miocene, Manzanilla formation, northwest side of Manzanilla Point,

Trinidad, U.S.N.M. 496543. 

FIGURES 7-9. Noetia mundonuevensis Maury, lower middle Miocene, Brasso beds, near the junction of Mayo and Couva main roads,

west-central Trinidad: 7, lectotype, X \%\ 8, 9, topotype, X 1. 

FIGURES 10, 11. Noetia colombiana MacNeil, n. sp., X 1%, holotype, middle Miocene, base of Juan de Acosta, between S-.co and Juan

de Acosta, Atlantico Department, Colombia, U.S.N.M. 496544. 

FIGURES 12, 13. Noetia ecuadoria MacNeil, n. sp., X 1, holotype, lower middle Miocene, Cueva de Angostura, Rio Santiago, Esmeraldas Province, northern Ecuador (Axel Olsson collection). 

FIGURES 14, 15. Noetia retractata (Hanna and Israelsky), X 1, topotypes, lower middle Miocene, upper Zorritos sandstone, just

southwest of Zorritos, Peru (Axel Olsson collection). ' 

FIGURES 16,17. Noetia mayensis Maury, X 1%, holotype, lower middle Miocene, Brasso beds, near junction of Mayo and Couva main

roads, west-central Trinidad. 

FIGURES 18, 19. Noetia mauryae MacNeil, n. sp., X 1& holotype, middle Miocene, upper Saco, "lookout" point on road just north of

Tubara, Atlantico Department, Colombia, U.S.N.M. 496545. 

FIGURE 20. Noetia ecuadoria (?) MacNeil, n. sp., X 1, lower middle Miocene, upper Zorritos formation, 1 mile east of Punta Picos,

Tumbez Province, Peru (Ar.el Olsson collection). 

FIGURES 21-23. Noetia cholana Spieker, holotype, lower middle Miocene, middle Zorritos formation, variegated bels, Quebrada

TuciUal, Zorritos, Peru: 21, 22, X 1; 23, X 2. 

FIGURES 24, 25. Noetia atratoensis MacNeil, n. sp., X 1%, holotype, middle Miocene, Quebrada Limon, Antioquia Department,

Atrato River district, Colombia, U.S.N.M. 496546. 

46
GEOLOGICAL SURVEY PROFESSIONAL PAPEE 189 PLATE 5

TERTIARY NOETINAE.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 6

TERTIARY NOETINAE.
PLATE 6

FIGURES 1, 2. Noetia macdonaldi alia MacNeil, n. subsp., X 1, middle Miocene, Gatun formation, Rio Bananito, 3)^-4 mil?.s from 

Caribbean Sea, Costa Rica, U.S.N.M. 496549.

FIGURES 3, 4. Noetia macdonaldi truncata MacNeil, n. subsp., X 1, middle Miocene, near San Andreas, Bolivar Department, Colombia: 3, holotype, U.S.N.M. 496550; 4, paratype, U.S.N.M. 496582.

FIGURES 5, 6. Noetia retractata (Hanna and Israelsky), X 1, holotype, Zorritos, Peru. This is the type of Area modesta Grzybowski, 

in the Jagiellonian University, Krakow, Poland.

FIGURE 7. Noetia triangularis Gray ( — N. reversa (Sowerby)). The holotype of the species on which the genus Noetia was based. 

British Museum.

FIGURES 8, 9. Noetia macdonaldi alia MacNeil, n. subsp., middle Miocene, Gatun formation, Costa Rica: 8, X 1, paratype, Cumbre 

Creek, Estrella River, U.S.N.M. 496548; 9, slightly reduced, holotype, "Hill No. 3", Banana River.

FIGURES 10, 12, 13. Noetia macdonaldi Dall, X 1, upper middle Miocene, Gatun formation, about a quarter of a mile soutl of the 

Banana River and about §>% miles from the Caribbean Sea, Costa Rica: 10, young topotype; 12, 13, holotype, 

U. S. N. M. 214344.

FIGURE 11. Noetia macdonaldi Dall, X 1, Rio Tagachi, 18 miles west of its junction with Rio Atrato and about 40 miles northwest of 

Quibdo, Antioquia Department, Colombia, U.S.N.M. 496547.

FIGURES 14, 15. Noetia turbacensis MacNeil, n. sp., X !}£, holotype, upper (?) Miocene, one-eighth mile northeast of mud volcanoes, 

Turbaco, Bolivar Department, Colombia, U.S.N.M. 496551.

FIGURES 16, 17. Noetia gardnerae MacNeil, n. sp., X 3, holotype, upper Miocene or Pliocene, from an oil well near Houston, Tox., at a 

depth of 1,700 feet, U.S.N.M. 496552.

FIGURES 18, 19. Noetia sheldoniana Maury, holotype, upper Pliocene, 1,000 feet west of Brighton Pier, Trinidad: 18, X 1^; 19, X 2. 

Museum of Geology, Cornell University, no. 38296.

FIGURES 20, 21. Noetia magna MacNeil, n. sp., X 1, holotype, Pleistocene, Mancora Tablazo beds, Paita, Peru. Jagiellonian University, Krakow, Poland.

FIGURES 22, 23. Noetia reversa (Sowerby), X 1, Recent, Guayamas, Gulf of California, U.S.N.M. 101954.

47

INDEX

Acknowledgments for aid..... _____ ....

Anadara. __ „ _ __ „ __________

nigeriensis— .— - ——— — — _ -...- ....

Anomia..---- __ ----- _ . ______ _ .

Area ________ __ ... _____ _ ------

bataviana— _____ ..--.. __ .- ....

congoensis.. —— — . — . —— — -.-- — —

delgada— — .-. _ -.-——. ___ ... ...

interplicata ____ .. _ ___ -- .......

lateralis ___________ __ .. ___ .

ponderosa _____ ... ____ __ .....

reversa —————— ---------- —— — — __

Arcopsis- — - ———— -------- __ __ --- ....

Argina.. ___ .-. —— --------- _ ..---. ....

Arginella... _ ._ — __ - __ __ ----------

ovalis ________ .- __ -- __ . ......

pimt.abravofinsis___ ._ .. . .

samanensiS-- — .-.-.- —— ___ —— . — -..

Arginopsis __ ------ _ — -..- _ ----------

sullanensis __ -------- _ ------ __ .-

Atlantic group, genera and species of ___ .

Barbatia ___ „ __ — —— -- —— --------- ...

pectnncnliformis ... „. .... .......

Breviarca. ___________ ____ .- ....

Classification, necessity for revision of. .-...

Eocene species ------ — — — — . — . — — -

Eontia— _ ———.—_ —— .- _ .. —— — —

bisulcata __ -.- —— — - ___ .. _ - _ -

caloosana.. _ __ -- ___ .-.. _ __ __

carol inensis-. __ -- _ . __ ---- ___ -

centrota— _ .-. __ . __ .- __ . _ . _ .

clewistonensiS--- ----------------------

contraria _ ____ — _-- — ...-.-..„.. ...

elegans--.--.- _ --------------- _ ..-..

filo?a_.. ............ — .................

incile.--.. _ __ --.- _ --- _ ------ ...

limula-. --- _ ---------- ___ -._- - .

lumberensis ——— . — — — ----- ------

mansfieldi _____ -------- __ .' __ —

martinii— — _ - _ ------- __ --------

okeni-. ___ „ __ _____ . _ __ ...

olssoni... ____ .... ___ __ ... _ ...

palmerae _ ------- __ __ __ .- __ -

platvura ___ ... __ . __ ____ ...

ponderosa- -. ——— - —— ---------------

protexta.- -..- _ __ .-. __ __ -- —

quadrata ______ _ ... ___ . _ ..-.

suffolkensis _____ ... ______ ...

tillensis.-.-- ____ _____ . -- ___ -

trigintinaria ____ __ _ _______

variabilis. __ ___ ..-- ______ ....

veroensis ___ ______ — _ ____ .

yorkensis- _______ ___ -- __ __

Geographic distribution. .. __ .. ___ ...--

Inner margin, crenulations of- _ ___ .....

Ligament, structure and distribution of. _ .

Lunarca ____________ . ______ _

pexata... _ __ .. —— _ ... __ .. ........

Miocene species.-- — ——- ________

Miocene or Pliocene species ___ _ ___ —

Mytilus.. ___ _ ... __ r ............... .-

Page

— ——— —————————— 1

— — — ——— ———————————— 2,26

-_ ——— — . — — ——— — — --.. 2

- — — — — — - — ___ ... . _ .. 1

— — —— —— ——— ————— 1,26,31

. ———— ————————— ————— _ 2

------------ ----- _ -. 2

— — — ——— ——— ——— — ———— 39

. ———— . — ... ———— ............ 2

----- — ... — ................ 2

... — ——— .. — — . — ————— .... 2

....———.. —————— ............ 2

. ——— ........———————— ...... 2,7

— — — .- — —— —— ——— — — . 2,27

---------------------- __ 2,7,27,38,30

--.-——- — — —— ———- 4,39

-- ————————— ——————— 4,39

-- — - —— — „—----—— 4,38,29

————— ———— 2,7,26,37,28,30

——————————————— 4,37,28

———— — —— — ————— ——— 2-4,8-25

— — —— — — — — —— —— — — 2

_ ........ ......... — .... _ .... 2

— — — — — — ... —————... 7

-- —— -. ——— ................... 1-2

.. — . — ....———...-. 8-10,36-29,30-31

— -- — — ___ 2,5,7,8,9,10,11,25,26,30

— .- — — — --- 2,3,8,10,11,12,13,14

- ——— ———- — . 3,30,21,22,23,35

.--- — . ———— - 3,4,17,18,19,20,25,37

— — — — — ——— 2,3,8,10,11,13,13,14

.-. — -.. ———— ...... — .. 3,20,33,25

———— ——— .. ————— ———— .... 24

.. ——— ————— ——— ... —— ——— . 24

— ——— ——— — —..- 3,17,18,19,20,25

— —— ... 2, 3, 11, 12, 13, 14, 15, 16, 19, 25

——— —— —— 3,8,17,19,20,21,23,24,25

- — — -- — - — __ — _ 3, 18, 19, 21, 22, 25

——— —— ————— ———— . 2,8,10,15,25

—— — —— — — — ——— ————— 13

— . — ...————— ............ 2,13,13

— — — — — — ——— 2, 3, 10, 11, 12, 13

-.— ——— ——— ———— 3,19,20,33,24,25

— —— —— ———— .—— 3,21,33,23,25

- — -.— 3, 4, 5, 11, 21, 23, 34,25, 37, 38, 39

- ——— — .—— — ————___._ 3, 1C, 17

— — ——— — —————— ————— 3,31

——————————— — — 3,15,16,19,25

- ——— _—————————— 3,30,21,23,25

.... 3, 14, 15, 16, 17, 18, 19, 20, 21, 23, 25, 37

------------ __ 3, 18,19,30,21,22,23,25

. — — ——— ——— ————— —— 3,34,25

— — — — — ———— — 3,14,15,18,25

— - — -.— — ———— ———— ... 2-5

. ____________ . . 8

——— ——— — ——— ——— ...... 7-8

—— — ——— — — ——— ——————— 27

. —— ————— —— — — —————. 27

— - — - — — .—-..- 10,12,13,31-37

—— — — ———— ——— ———— —— 37

——— — ————————————— 1

Page 

Noetia————————————————————— 2,5,7,11,13,26,27,39,30

alta—————————————————————— ————— 5,35,36,37

atratoensis—-----------—-———————.—————-——————-— 4,35,36

cholana——————————————————————- 1,4,33,33,34,35

colombiana. — .———-—————-————————— 4,6,33,5-4,35,36

ecuadoria.......----—.__ — -_---———-————-————- 4,5,31, F3,34,36

gardnerae—---.—---.__-______.——————-————— 4,5,6,25,37,38

hemicardium.__..____-----———— ————— ———————------ 38

macdonaldi-—.___——.——._—....__....__- 4,5,6,33,34, JT5,36,39

magaa— ————--- —————————————.———- 5,38,39

manzanillae__________-_____-————————————————-— 4,30,33 

mauryae_______----— — ————— ————— ——————— ——— 4,34,35

mayensis..___.___.-..- ————— ———— ———— ——— -——— 4,34,35

modesta._____————————————————————-——————————— 5,33 

molengraffi. -.__________._——————,—————————————— 4,30 

mundonuevensis.———-——. ——————.————————————-——— 4,30,33 

nagoL-__-------- ———————————————————— ——————————— 4,30

pondaungensis-.--—- ———————— —————————————————————— 4,30 

retractata._.„.--.____________———————.„__-------- 5,3",33,31

reversa. ———————————————_- — - 5,6,29,34,35,36,38,39

sheldoniana—— —— ——————— ———————————— 5,6,37,38

stewarti---____—_————-————————-———-————. 4,31,32,33 

subreversa___— —— ——————————————— ————— ———— --—— 35,36

transversa______--..———.—— — ———————————. ——————— - 30,31 

triangularis.-_..-.__------__.._.___——.———______ 1,38,39

trinitaria-______-_______._.__________________ 4,5,31,33 

truncata...--—— —— .-- ——— -—————————————. 5,36,37

turbacensiS--——— —— ————————————— —— ———— —— ——— 5,37,38

Noetiella-.---—--------------------.—-——----------------—.————— 2

pectunculiformis-. ——— —— ————— ——————— —————————————— 2

Noetiopsis—-____—————__————————-———— 2,36,27,28,30

woodringi...———————————.—————————— 2,4,36,27,28,30

Nucula—_——— ———— —— ——————— ——————————————————— 1

Nuculana..—————. ———————— - ——— —.————————————————— 1

Oligocene species. 29

Pacific group, genera and species of..- — — -----—_- — — ——— ———— 4-5,25-39

Paranoetia————————————————— —— ———————— 2,7,9,10,11

cafria—_——_—————— ——— ——————— .—. —— -. 2,9,11

lateralis—--------—.-----——-------————.———_—— 2,9,10,11

venusta____.-.-——— —————— ——— — - — ————— ——- - 9,10,11

Pecten___________..——————— —— ——— ——————————— —— 1

Pleistocene species_______._____________________..__ 23-24,38 

Pliocene species—..___.-—.-....-.————-.-„———-—.—— 12,19-23,37-38

Protonoetia.—.___.__————.————.———----- ——— —— 2,5,7,35,28

nigeriensis.————————————————————— 4,25,36, ?7,28,31

Purpose of the paper_——-———————— — - —— —————— ———————— 1

Recent species---____-----—-—.——.———.——-—— 10-12,13,24-25,38-39

Scapharca.._————— — —————— ——————— ———— —— ———————.. 2

Scapularca-———.———-———————————————- 2,5, 7, 8,9,11?, 11,26

globulosa._------__————————————.- —— -- —— — ————— -- 8,9

interposita..__—__._-_______—-___-_________ 2.8,9,12 

miliacea.-—-——— ———————————————— —— ———— ————.-.. 9

scapulina_„.—- ————————————————— ——————————————— 2,8,9 

subglobulosa——.-—————— ————————— ——————————————— — 2,8

Sculpture, differences in___...—————————————————————————— 6-6 

Sheldonella——————............. ... ........... ........ - 2,5,7,9,10,11,26,32

maoica————..——————————————-L——————— 2,9,10,11,12

cuneolus__-___.———————— —— ————— —————— — —————— 10

Stratigraphic occurrence of species. —————————— — ————— —————— 2-5

Striarca___-______-——-—-— ———— —— — —————————————— 7

Trigonodesma.

49

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