UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary 

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director 

Professional Paper 189-F 

THE VENERICARDIA PLANICOST_L~ GROUP 

IN THE GULF PROVINCE 

BY 

JULIA GARDNER AND EDGAR BOWLES 

Shorter contributions to general geology, 1937 

(Pages 143-215) 

UNITED STATES I 

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1939 

For sale by the Superintendent of Documents, Washington, D. C. - - - Price 40 cents 
CONTENTS 

Page 

Abstract------------------------------------------------------------------------------------------------------ 143 Introduction and acknowledgments __________________________________________________ -- _______ --------------_--_- 143 

Stratigraphic background of the Venericardia planicosta group on the American continent ______________ -_----------_____ 143 

Eoceneepoch--------------------------------------------------------------------------------------------- 143 

~idway grouP---------------------------------------------------------------------------------------- 143 

VVilcoxgrouP------------------------------------------------------------------------------------------ 148 

ClaibornegrOUP--------------------------------------------------------------------------------------- 151 

Jackson grouP----------------------------------------------------------------------------------------- 156 

World distribution of early Eocene species comparable to Venericardia planicosta_______________________________________ 160 

Hinge inversion in pelecypods___________________________________________________________________________________ 163 

BibliographY-------------------------------------------------------------------------------------------------- 165 Systematic descriptions_________________________________________________________________________________________ 167 

Index________________________________________________________________________________________________________ 213 

ILLUSTRATIONS 

Page 

PLATE 29. The occurrence of species of the Venericardia planicosta group in the Eocene of Alabama _______________ -_____ 148 

30. The occurrence of species of the Venericardia planicosta group in the Eocene of the Atlantic and Gulf se:J.board 

exclusive of Alabama_______________________________________________________________________________ 148 

31. Areas of outcrop of marine beds of probable early Eocene age_____________________________________________ 164 

32. Diagrammatic representation of diagnostic characters of the A:nierican species of the Venericardia planicosta group_ 164 

33-46. Fossils of the Venericardia planicosta group_____________________________________________________________ 198 

FIGURE 27. Distribution of species of the Venericardia planicosta group in the Eocene of the Gulf Embayment and eastern 

Atlantic ffiope------------------------------------------------------------------------------------ 160 

INSERTS 

Page 

CHART 1. Correlation of east coast and Gulf Eocene formations in the United States___________________________________ 144 

2. Stratigraphic distribution of east coast and Gulf species of the Venericardia planicosta group _____ -_-------_---- 144 

3. Possible phylogenetic relationships in the east American Venericardia planicosta group ____________ -------_---- 144 

II 
THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

By JuLIA GARDNER and ·EDGAR BowLES 

ABSTRACT 

Venericardia planicosta of authors is considered as a monophyletic group of species rather than as a single specific 

unit. This group is restricted stratigraphically to the Eocene, 

but it is world-wide in geographic distribution. Each of the 

included species is generally confined to a single formation or 

member, but within its zone each is widely distributed, abundant, 

and conspicuous by reason of its size and ornamentation. As 

guide fossils the members of the plan·icosta group are therefore 

among the most significant of the Mollusca. Although no 

ancestral types have been recognized in the Cretaceous of the 

Gulf region, two virile branches of the planicosta group were 

already established in the region at the beginning of the Eocene 

epoch, and the present study is an attempt to trace their progress 

and development through the Eocene. Both of the branches, 

represented in the Midway deposits by V. smithii and V. mediaplata, are abundantly represented in the Wilcox deposits, particularly in the eastern Gulf province, by descendants of the 

Midway species. During the deposition of the middle Wilcox 

Tuscahoma and Bashi formations the planicosta group probably attained its greatest prominence in the size and abundance 

of individuals and in the diversification of the species, but 

their development is provincial. The faunas of the lower Claiborne deposits, on the other hand, especially those from the 

upper part of the lower Claiborne, are the most cosmopolitan of 

all the Eocene venericard faunas. The transgressional seas 

were not confined to the Gulf province but invaded Mexico, the 

Isthmus of Panama, and northern South America. So far as 

the venericards are concerned, the marine upper Claiborne, 

best represented by the Gosport sand, contains nothing more 

than a greatly reduced lower Claiborne fauna. After the 

widespread emergence at the end of Claiborne time, the venericards failed to regain their former prominence. Several species 

are known in Jackson deposits, but none of them are abundant, 

and the decline in the number of individuals and species during 

the Jackson epoch heralded the extinction of the group at the 

end of the Jackson. The occurrences of the planicosta group in 

western North America, South America, and the Old World are 

briefly considered. For the Asia-European representatives of 

the planicosta group, the life cycle was essentially the same as in 

America. In this paper 44 species and subspecies are deffcribed 

and illustrated; of these, 24 are new. 

INTRODUCTION AND ACKNOWLEDGMENTS 

A study of the distribution of the Eocene faunas of 

the Mexican border has been made possible by· extensive collections submitted by the petroleum companies 

of Mexico and by funds for their investigation granted 

through the generosity of the National Research 

Council and the Penrose Bequest of the Geological 

Society of America. To the donors of the collections, 

to those who have financed thi<s investigation, to W. H. 

Twenhofel and Albert L. Barrows, to L. W. Stephenson 

and John B. Reeside, Jr., of the Geological Survey, for 

their sustained and lively interest and their ever timely 

suggestions, and to Nell L. Bowen, who has done our 

secretarial work, we are deeply grateful. 

The present paper is concerned only with the Veneri .. 

cardia of the P.lanicosta group and their geographic and 

stratigraphic distribution, particularly in the e:1.st 

coast and Gulf regions, but the results have been pq,rtially checked against other members of the fauna. 

(See pis. 29 and 30 and correlation chart.) 

Timothy Abbott Conrad, the leader of the early 

coterie of malacologists in Philadelphia, characterued 

Venericardia planicosta as "the finger post of the 

Eocene", for no true planicosta had been recognized 

below the base of the Midway, and it has been very 

doubtfully identified above the top of the Jackson. 

No other group of Eocene pelecypods, for planico<:!ta 

as it has been commonly used on the American Continent is a group rather than a specific name, is so widespread nor, in its manifold variations, of greater stra,tigraphic significance. On the Western Hemisphere 

conventional members have been recovered from New 

Jersey to Argentina and west to the Pacific coast. 

The wide distribution of a fauna is commonly interpreted as indicating an ancient origin, and the 

wider the distribution of a given restricted group the 

deeper, presumably, are its roots in geologic tune. 

Although the focus of origin and the strand lines of 

dispersal of Venericardia planicosta are largely speculative, there is reason to believe that the group is r0t 

definitely foreshadowed in the Gulf Cretaceous but in 

more remote regions, and that the development and 

general distribution in the Western Hemisphere wnre 

largely acc01nplished between the end of the fossiliferC'us 

Upper Cretaceous and the beginning of the Eocene. 

STRATIGRAPHIC BACKGROUND OF THE VENERICARIIA 

PLANICOSTA GROUP ON THE AMERICAN CONTINENT 

EOCENE EPOCH 

The general relationships of the Eocene formations 

of the east coast and Gulf regions are indicated in the 

correlation chart. 

MIDWAY GROUP 

The name "Midway", first used by Smith and 

Johnson/ was derived from Midway Landing, on the 

1 Smith, E. A., and Johnson, L. C., Tertiary and Cretaceous strata of the Tuscaloosa, Tombigbee, and Alabama Rivers~ U.S. Geol. Survey Bull. 43, p. 62, 1887. 

143 
European Generalized New Jersey I Maryland, North 

American Virginia Carolina 

Ludian. 

Missing? 

Upper. Jackson group. Missing? 

Castle Hayne marl. 

Bartonian. 

Auversian. 

Middle. Claiborne group. Shark River marl Not exposed. (probably middle 

Eocene). 

Lutetian. 

Manasquan marl. Nanjemoy 

formation. 

Lower. Ypresian. Wilcox group. Not exposed. 

Rancocas group. A quia formation. 

Thanetlan. 

Basal. Midway group. Missing? Missing? 

Montlan. 

, lla!nt Ma11rlce of Spooner~ }~~. ~ }'o;;;;lbly of lower Ml<lwa,- age. 

CHART I.-Correlation of east coast and Gulf Eocene formations in the United States 

South Carolina I Georgia I Florida I Alabama I Mississippi Ten· I 

Ken- Missouri Arkansas I Louisiana Texas nessee tucky 

_I 

~ Cooper Yazoo clay marl. member. 

Barnwell Ocala limestone. Jackson Missing? Not ex- Jackson formation. Jackson group. sand. formation. posed. 

Santee Moodys marl 

limestone. member. 

Gosport sand.• I Yegua formation. Yegua formation. 

Cook Mountain forma· Cook Mountain formation. 

Lisbon I Kosciusko sand· tion.• 

formation. stone member. Sparta sand. Sparta sand. 

McBean formation. Not ex- __ Winona sand Missing? Weches greensand member"! posed. I member. Cane River formation. -1 Queen City sand member Mount S!!lman --_1 _ · formatiOn. 

Reklaw member. 

Tallabatta fonnation.d 

I Tallahatta 

formation. I Carrizo sand. 

Hatchetlgbee 

I Grenada formation. 

formation. 

Bash! formation. _.g Bash! 

o:g forma- Not exposed. z~ tlon. 

Undifferentiated Not ex· Tuscahorna sand. Not ex· Undifferentiated Wilcox. 

Wilcox. posed. Holly Springs sand. posed. 

N anafalla formaBlack Mingo forma- tion. 

tion.• 

Ackerman forma- Ackerman formation. I 

tion. __ Tippah sandstone 

I member. I ;.:. Wills Point formation. --I .. Naheola formation. --_1 __ !l 

Undifferentiated. ~ Sucarnoochee Porters Creek clay. "d Not ex- 3 Undifferentiated Not exposed. posed. ~ clay. ~ Midway. i:l 

Midway. f 

<D Kincaid formation. 

Clayton formation. Clayton formation. 11:1 

:a 

= t:> 

• Probably a facies equivalent to the Moodys marl member. 4 Equivalent In part"to the Winona send member of Misalssippl and the Mount Selman formation of Texas. 

20412-39 {Face p. U4) No.1 
144 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

Alabama River, where the basal Eocene is well exposed. 

Synchronous deposits were laid down across Alabama 

into Georgia (with possibly an mnbayment in central 

New Jersey) and to the west through northeastern 

Mississippi into Tennessee and Kentucky, down across 

southeastern Missouri, through central Arkansas, and 

in a great sigmoidal curve across eastern and southern 

Texas into Mexico. 

The Midway group is ren1arkably uniform in general 

make-up and is characterized throughout the greater 

part of its extent by a lower glauconitic sand and sandy 

lilnestone series overlain by clays and fine sandy clays. 

Both in the Alabama sections and in those of the western 

Gulf region the highly calcareous and fossiliferous beds 

are succeeded by a relatively barren series of clays and 

sands. Many sections in both the eastern and the 

western Gulf regions show no perceptible break between 

Midway and Wilcox sedin1entation, and consequently 

confusion in the correlation has arisen. After the long 

Cretaceous-Eocene quiescence the early Midway was 

apparently a tilne of rather marked erosional activity. 

The strean1s were rejuvenated and cut deeply into the 

Cretaceous sands and limestones, so that the lower 

Midway, like its lithologic antecedents, is a dominantly 

calcareous series. At the end of the lower Midway 

there was a fairly abrupt change in the character of 

sedimentation. The strean1s were restricted in their 

activities largely to the finrr argillaceous sedilnents of 

the Upper Cretaceous, and the resultant ecology was 

much less favorable, especially to the larger bivalves. 

Not only was the source of the coarse sands apparently 

cut off, but also the source of the abundant lime, and it 

seems probable that the upper Midway nmds and silts 

were transported largely by old, sluggish streams meandering through a low hinterland of Upper Cretaceous 

clays and were laid down in waters of no considerable 

depth. 

The Midway is divisible in Alabama into three fornlations-the Clayton formation, the Sucarnoochee clay, 

possibly in part contemporaneous with the Clayton, 

and the N aheola formation. The oldest of these, the 

Clayton,2 resting with marked unconformity upon the 

Cretaceous, extends from the Chattahoochee River on 

the Georgia border to the Alabama River, west of 

which it is overlapped by the Sucarnoochee clay. The 

Clayton formation consists largely of limestone, grading 

from a hard stone to unconsolidated sandy limestone 

and calcareous sand. The name is derived from the 

town of Clayton, in Barbour County, near which it is 

admirably exposed. The Sucarnoochee clay 3 takes its 

name from Sucarnoochee Creek, in Sun1ter County, 

although the most characteristic outcrop is in Black 

s Langdon, D. W., Jr., Variations in the Cretaceous and Tertiary strata of Alabama: Geol. Soc. America Bull., vol. 2, p. 594,1891. Smith, E. A., Langdon, D. W., 

Jr., and Johnson, L. C., Report on the geology of the Coastal Plain of Alabama, 

p. 192, Alabama Geol. Survey, 1894. 

I Smith, E. A., Sketch of the geology or Alabama, p. 28, Birmingham, Roberts 

& Son, 1892. 

Bluff, on the Tombigbee River below the mouth of 

Sucarnoochee Creek. This formation is exrnsed from 

Butler County westward to the Mississippi State line 

in Sumter County. East of Butler County the sedi .. 

ments are either missing, overlapped by the N aheola, 

or represented by clay, but the base is in some places 

calcareous, making an exact distinction between this 

formation and the Clayton difficult. Cooke 4 said of 

this relation: 

The two formations appear to be conformable and were laid 

down during one epoch in which the deposition of limestone and 

calcareous clay was succeeded by the deposition of clay, the 

change taking place first in the west and gradually proceeding 

eastward. As a result of this the boundary between the two 

formations transgresses several zones. In other words, the 

Sucarnoochee clay and the Clayton formation in different areas 

are partly of the same age. 

The Naheola formation 5 derives its name from 

N aheola Landing on the Tom big bee River. The constituent sands and clays in varying propc.,.tions are 

exposed from the Mississippi State line almost to the 

Chattahoochee River, although only in tt~ western 

portion are they fossiliferous. The nonfossiliferous 

clays and sands of the Chattahoochee River area have 

not been definitely correlated with the fossiliferous 

western beds, but as they occupy a similar sti·atigraphic 

position they are tentatively considered 6 to be the 

equivalent of the Naheola on the Tombigbee. 

In Georgia the deposits n1apped as undivided Midway formation appear to be equivalent to tl'~ Clayton 

formation. 7 The Midway formation has not been 

definitely recognized northeast of the Ocmulgee Valley. 

In the calcareous deposits of the lower Midway two 

virile races of Venericardia planicosta we:--e already 

established. The present study will be focused upon 

them and their progress and developn1ent tlTough the 

Eocene (chart 3). The "Turritella rock" of Aldrich, 

1886 (Clayton formation), at Allenton, Wilcox County, 

Ala., is the type locality for both Venericardia mediaplata, n. sp., and Venericardia smithii, -but for V. 

mediaplata it is the upper stratigraphic limit of distribution, while for V. smithii it is the lower limit. There 

is thus an overlap in the range of V. mediaplata, a 

characteristic species of the lower fossiliferou~ Midway, 

particularly of the limestone, and of V. smithii, which 

is best developed in the higher glauconitic zo:'le. Venericardia mediaplata averages about 48 mill~meters in 

width and is characterized by the low, bro".d outline 

and flat, close-set ribs, 29 to 31 in a short series, persisting without modification to the ventral border. 

The beaks are not weU preserved, but there is no 

perceptible trace of serration or lateral ridging. The 

posterior area is well defined both by the angulation of 

the whorl and by the narrower cordlike ribs. The 

'Cooke, C. W., Geology of Alabama; The Cenozoic formations: Alabama Geol. 

Survey Special Rept. 14, p. 255, 1926. 

a Smith, E. A., and Johnson, I~. C., op. cit. (Geol. Survey Buii. 43), p. 57. 

e Cooke, C. W., op. cit., p. 257. 

7 Cooke, C. W., oral statement. 
STRATIGRAPHIC BACKGROUND OF THE VENERICARDIA PLANICOSTA GROUP 145 

hinge plate is broad and low, adequate though not conspicuously heavy. Harris 8 figured an exceUent specinlen of this species from the basal limestone at the old 

river landing on the Chattahoochee River at Fort 

Gaines, Ga. The species has not been recognized north 

of Marshallville, Macon County, Ga. 

Venericardia smithii indjcates in the rudely quadrate 

inflated outline and the ridged serrate ribs a closer relatipnship to the v·. alticostata group than that shown 

in 1lenericardia mediaplata. The charac\ers to be 

noted in V. smithii are the rather small and not very 

heavy, highly inflated valves, the rather obscure 

definition of the posterior area, the numerous (30 to 33) 

very high and narrow ribs with serrate crests, and the 

narrow hinge plate. The species is represented in the 

lower Midway fron1 Wilcox County, Ala., eastward to 

Ellaville, Schley County, Ga. A single mold of the 

interior of the double valves of a sin1ilar Venericardia a 

little more than 50 n1n1 high and almost equally wide 

and 40 n1m in diameter was recovered by Cooke and 

Stephenson from the Hornerstown marl of New Jersey, 

which they consider to be of Wilcox age. 

Venericardia antiquata Whitfield, from the Shark 

River marl, is a con1pressed rounded trigonal species 20 

to 25 millimeters in height and width, suggesting in its 

outline the Yenericardia rotunda group. The ribs are 

crested and sharply serrate, with well-developed lateral 

terracing, and the affinities of the species are probably 

with the smaller species of Venericardia of the middle 

Eocene faunas rather than with those of the lower 

Eocene. 

West of the Alabama line the Midway outcrops 

occupy a wide belt extending through Mississippi northward across Tennessee and the extreme southwestern 

tip of I{entucky. The Clayton, the lowest of the three 

Midway formations in the Alabama section, is definitely 

recognizable and the nB.me has been adopted both in 

Mississippi and in Tennessee. 9 The overlying clays 

and sandy clays, the Porters Creek, have not yet been 

studied in great detail. Many of the older reports 

include in the Porters Creek both deposits of lower and 

upper Midway ages, but the typical Porters Creek clay 

is sin1ilar to the Wills Point of Texas and is of upper 

Midway age. 

The Clayton is rather poorly developed in the Mississippi outcrops, but it unconformably overlies the 

Owl Creek formation at the type locality on Owl Creek. 

The reconnaissance geologic map of Mississippi 10 represents it as outcropping discontinuously in Kemper and 

N oxubee Counties and continuously, in a north-south 

belt about 3 miles wide, from Houston, in Chickasaw 

County, to the State line, about 75 miles to the north. 

s Harris, G. D., The Midway stage: Bull. Am. Paleontology, vol. · 1, no. 4, pl. 

4, fig. 13, 1896. 

9 Roberts, J. K., Tertiary stratigraphy of west Tennessee: Geol. Soc. America 

Bull., vol. 39, p. 436, 1928. 

10 Stephenson, L. W., Logan, W. N., and Waring, G. A., The ground-water 

resour.ces of Mississippi: U. S. Geol. Survey Water-Supply Paper 576, geologic map, 

1928. 

• 

Lowe 11 reports a very pure basal limestone overlain by 

sandy glauconitic marl and micaceous sands, carrying 

fossils in considerable abundance locally but very poorly 

preserved. The fauna contains several species not 

reported from the Clayton of Alabama but present in 

the Midway of Texas. Superimposed upon the Clayton is th~ Porters Creek clay, typically an unctu'lus 

gray joint clay, very fine grained and slightly micaceous, 

breaking with a conchoidal fracture and exfoliating: as 

it dries. Locally it is lignitic or sandy and thin-bedded 

and exceedingly difficult to separate from the overlying 

Wilcox. Fossils are rare, and it is probable that mr,ny 

of the species reported in the earlier observations from 

the Porters Creek came from the Clayton formation 

beneath. The name was proposed by Safford 12 for a 

clay which "has the usual characters, contains mica 

scales, is dark when wet and whitish gray when dry." 

He also observes that "I have met with hard layers 

(rocks) in this series containing shells, but as yet have 

found no determinable ones." 13 It is probable that the 

"hard layers" are properly referable to the Clay~on 

rather than to the present conception of Porters Creo.k. 

Plant remains have been recorded from a few localit~,~s. 

At or near the top of the Porters Creek in northern 

Mississippi is the Tippah sandstone member, interpreted by Lowe as representing "a period of shallow, 

turbulent, swift-flowing water bearing great quantities 

of coarse sand.m4 

Good fossil localities are rare both in Mi~sissippi fl.nd 

in Tennessee. In Mississippi, from beds of Midway 

age near New Albany, Union County, Venericardia 

francescae, n. sp., has been described. It is a V~3ry 

eompact little form with a subquadrate outline and 

relatively few but .prominent radials. V. jrancescae is 

known only from the holotype. Venericardia mediaplata has been recognized in the Clayton near Ripl~y, 

and it is possibly present at a similar horizon in 

Tennessee. 

Venericardia hijuana, n. sp., is described from the 

vieinity of Middleton, in Hardeman County, Tenn. 

The umbonal region is broadly inflated, the ventral 

and posterior margins are flattened, and there if a 

distinct sculptural break between the disk and the 

posterior. region. The radial sculpture is very cham.cteristic, the simple juvenile ribbing followed by the 

laterally ridged adolescent costae and these in turn 

succeeded by a return to the simple ribbing in the 

adult portion of the sh~ll. This form seems most 

closely allied to V. jewelli, from southern Texas. 

An internal mold of a large Venericardia probaPy 

related closely to V. smithii was recovered from .tbe 

Tippah sandstone member exposed 2}~ miles south11 Lowe, E. N., Coastal Plain stratigraphy of Mississippi. Midway and WPoox 

groups: Mississippi Geol. Survey Bull. 25, pt. 1, p. 3, 1933. 

u Safford, J. M., On the Cretaceous and superior formations of west Tenne!'•: 

Am. Jour. Sci., 2d ser., vol. 37, pp. 361, 368, 1864. 

13 Idem, p. 369. 

u Lowe, E. N.,.op. cit., p. 4, 1933. 
146 · THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

southwest of Walnut, Tippah County, Miss. Similar 

molds were collected east of Bolivar, north and west 

of Crainesville, and near Middleton, Hardeman County, 

Tenn. 

No venericards are reported among the few impressions in the clays from the vicinity of Paducah, McCracken County, l{y. The beds were referred by 

Roberts 15 to the Porters Creek, because of their field 

relations and their characteristic lithology. 

Overlying the Porters Creek clay of Mississippi is a 

wide band of nonfossiliferous sediments known as the 

Ackerman formation. This series of cross-bedded sands 

and lignite were correlated by Cooke 16 in 1925 with the 

Nanafalia formation (basal Wilcox) of Alabama. In 

his later discussion of the formation, 17 however, he 

postulated a correlation of the Ackerman formation 

with the Coal Bluff beds, placed by SII?-ith,18 Langdon,I9 

and Brantley/0 at the base of the Nanafalia formation 

of Alabama. 

Cooke 21 in 1926 followed Smith 22 in giving the 

Nanafalia formation a threefold division, but in 1933 

he stated: "I followed Smith's threefold division of the 

Nanafalia formation in the 'Geology of Alabama,' 

although I suspected that the lower member [tCoal 

Bluff beds 23] does not logically form part of the N anafalia." Adams u thought that the tCoal Bluff stratum 

could not be properly included in the Nanafalia, and 

he found that the beds could be traced westward across 

the Alabam~-Mississippi State line into the Ackerman 

formation. 

The general lithology and field relations of the Porters Creek clay and the Ackerman formation are 

strongly reminiscent of the Wills Point forn1ation and 

the upper sand exposed near New Hope, Tex. There 

is, unfortunately, no faunal evidence to sustain the 

argument. 

The west side of the Mississippi embayment has 

been the scene of an uncmnmonly interesting series of 

recent observations and collections. Greenish glauconitic clays carrying molds of marine shells were 

discovered and collected by F. E. Matthes in Crowleys 

Ridge, near Ardeola, Stoddard County, Mo., in the 

course of his geomorphologic studies of the lower 

Mississippi Valley, and an additional collection was 

13 Roberts, J. K., Cenozoic fauna and flora: Kentucky Geol. Survey ser. 6, vol. 36, 

p. 412, 1931. 

u Cooke, C. W., Correlation of the Eocene formations in Mississippi and Alabama: 

U. S. Gaol. Survey Prof. Paper 140, pp. 133, 134, 1925. 

17 Cooke, C. W., Ackerman formation in Alabama: Am. Assoc. Petroleum Geolo· 

gists Bull., vol. 17, no. 2, pp. 192-195, 1933. 

IS Smith, E. A., Report on the geology of the Coastal Plain of Alabama, p. 170, 

Alabama Geol. Survey, 1894. 

10 Langdon, D. W., Jr., in Smith, E. A., 'op. cit. p. 421. 

• 2o Brantley, J. E., Petroleum possibilities of Alabama, pt. 2, Southern Alabama: 

Alabama Geol. Survey Bull. 22, p. 149, 1920. 

21 Cooke, C. W., Geology of Alabama; The Cenozoic formations: Alabama Geol 

Survey Spec. Rept. 14, p. 258, 1926. 

22 Smith, E. A., op cit., p. 170. 

23 A dagger (t) preceding a geologic name indicates that the name bas been aban· 

do ned or rejected for use in classification in the publications of the Geological Survey. 

H Adams, G. I., quoted by Cooke in 1933 from an unpublished manuscript sub· 

mitted to him just prior to the death of Professor Adams. 

made by W. Farrar, of the Missouri Geological Survey 

and Water Resources. The fauna was reported to be 

lower Midway with mechanically introduced Cretaceous fossils (identified by L. W. Stephenson). 

Further investigations by Stephenson, of the Geological 

Survey, in company with W. Farrar and H. S. McQueen, 

of the Missouri Bureau of Geology and ~1ines, revealed the Owl Creek clayey sand underlying the 

glauconitic clays. Still further investigations disclosed aboye the glauconitic bed some 35 to 40 feet of 

gray clay, apparently barren and referred to the Porters 

Creek. Two species of venericards are included in the 

small fauna from the glauconite bed of probable Clayton 

age. These are small internal molds, less thr,n a centimeter in width and similar in a general wa~ to those 

found north of Cumby, in Hopkins County, Tex., and 

south of Greenville, in Hunt County, Tex. There are 

also fragments of a larger form with relativel~r few and 

wide tripartite ribs separated by linear irterspaces. 

The crests of the ribs are sharply defined an-i strongly 

and evenly nodose. No relationship to any 1nember of 

the V. planicosta group is indicated, but it is hoped 

that future collections may include some representative 

of the widespread group. It may not seem irrelevant 

to repeat Matthes' observations: 25 

This simple conception of the structure of Crowleys Ridge is, 

of course, in harmony with the general conception of the arrangement of the Cretaceous and Tertiary strata in the Mississippi 

embayment in the form of a spoon-shaped geosyncline, the beds 

all dipping gently from the periphery inward, disturbed only by 

minor flexures. The eastern half of the geosy:1.cline very 

probably has a simple spoon-shaped structure, to judge from 

the concentric arrangement of the outcrops, more especially 

of the Upper Cretaceous formations, which forn'. the outer 

border. These formations crop out in an almost continuous 

belt extending northward through Misbissippi and Tennessee 

and curving northwestward through Kentucky ard westward 

and southwestward through southern Illinois. The western 

half of the geosyncline, however, is decidedly moce irregular. , 

This fact was already somewhat evident from the varying depths 

at which the Cretaceous has been reported in deep wells, but it 

is now suddenly made conspicuous by the discovery of Ripley 

and overlying Clayton beds in Crowleys Ridge at a I ~ight of 160 

feet above the plain of the Mississippi. 

In Arkansas the lower Midway limestore forms a 

prominent topographic feature along the western 

margin of the Coastal Plain. The outcrop occupies a 

narrow and interrupted belt in southeastern Independence County, western Jackson County, f,nd northeastern White County, and from Little Rock southwestward through Pulaski and Saline Counties nearly to 

Rockport, in Hot Springs County. The lunestone is, 

locally at least, highly fossiliferous, but the shells are 

not preserved, and Venericardia is indicated in our 

collections only by specifically indeterminate molds. 

In southwestern ·Arkansas the expression of the Midway 

is quite different. The basal beds in Nevada and 

Hempstead Counties are highly glauconitic, frequently 

2s Matthes, F. E., Cretaceous sediments in Crowleys Ridge, scutheastern Mis· 

souri: Am. Assoc. Petroleum Geologists Bull., vol. 17, no. 8, p. 1006, 1933 . 

• 
STRATIGRAPHIC BACKGROUND OF THE VENERICARDIA PLANICOSTA GROUP 147 

phosphatic, soft dirty chalks or sandy clays, abounding 

in Foraminifera. Molluscan remains, however, are 

uncommon and where present, imperfectly preserved. 

Hull 26 reports a Venericardia, determined by H. V. 

Howe, from a locality 3 miles north of Emmet, in 

Nevada County. The Wills Point formation (upper 

Midway) extends from northeastern Texas into Arkansas, but no detern1inable n10lluscan remains have been 

reported from the Arkansas outcrops. In Louisiana 

the Midway is exposed only by doming, and no venericards from the few exposures of this sort have been 

recorded. 

Two formations of the Midway group have been 

recognized in Texas. The IGncaid, outcropping, with 

some interruptions, from Hopkins County to the Rio 

Grande, includes a series of basal glauconitic and fossiliferous sands and clays, calcareous glauconitic sands 

characteristically indurated with a calcareous cement, 

and highly fossiliferous loosely indurated sands similar 

both lithologically and faunally to the Clayton, with 

which they are probably synchronous, and the Wills 

Point formation, which crops out less co:qspicuously 

but more persistently from the Arkansas linel to the Rio 

Grande. The name "Basal or Wills Point clays" was 

introduced by Penrose 27 in 1890 to cover the entire 

Midway section. His description, written 40-odd 

years ago, is still adequate: 

They consist of a stiff laminated clay,. yellow, gray, blue, or 

bluish green in color, frequently interbedded with seams and 

laminae of s'and, containing many concretionary masses of gray 

nonfossiliferous limestone, the latter much cut up by veins of 

brown crystalline calcite and varying in size from a few inches to 

6 feet in diameter. They are generally of a flat elliptical shape 

and of a gray color. Large quantities of gypsum are also found 

in places in the clay. 

Although the formations and members of the Midway 

in Texas are fairly constant in general character, the 

lithologic and faunal variations are sufficiently great to 

preclude any assumption of the existence in the lvlidway 

epoch of an unbroken shore line, especially during early 

Midway time. Streams much like those of the present 

day were probably existent during the Tertiary and 

may have formed barriers, possibly of fresh water, 

between the faunal provinces. In all the Tertiary 

deposits a marked change in the character of the 

sediments.and in the contained fauna is coincident with 

the change in strike of the outcrops south of San 

Antonio. The general conditions of sedhnentation were 

probably the same in southern Texas and in Limestone 

County, but there was no direct communication between 

the embayments. The species common to both faunas 

20 Hull, J. P. D., Guide notes on the Midway in southwestern Arkansas: Am. 

Assoc. Petroleum Geologists Bull., vol. 9, p. 169, 1925. 

21 Penrose, R. A. F., Jr., Preliminary report on the geology of the Gulf Tertiary of 

Texas: Texas Geol. Survey 1st Ann. Rept., pp. 19-22, 1890. Kennedy, w. A., 

A section from Terrell, Kaufman County, to Sabine Pass, on the Gulf of Mexico: 

Texas Gaol. Survey 3d Ann. Rapt., p. 49, 1892. Deussen, Alexander, Geology and 

underground waters of the southeastern part of the Texas Coastal Plain: U.s. Gaol. 

Survey Water-Supply Paper 335, pp. 36-37, 1914; Geology of the Coastal Plain of 

rexas west of Brazos River: U. S. Geol. Survey Prof. Paper 126, p. 40, 1924. 

are pelagic forms such as the Bryozoa, or forms that 

pass through a pelagic larval stage, or cosmopolitan 

types. None of the heavy-shelled in-shore spedes 

such as the large Venericardia of the Rio Grande 

fauna have been recognized north of ,Bexar Cour.ty. 

For their nearest kin we must look to the south. 

The invading sea apparently entered the Rio Grande 

embayment from the south and east and withdrew in 

the same direction. Certainly the Midway section in 

Mexico is enormously thickened and includes Midv-ray 

both lower and higher than any recognized in southo,rn 

Texas. Although the Rio Grande section may be 

thinned by overlap, the wells on the Farias ranch, n~ar 

the Dimmit-Maverick County line, revealed o~ly 

300 feet of Midway, and those drilled along the same 

structural feature farther east less than 200 feet, while 

the Mexican Midway probably exceeds 1,500 feet in 

thickness. 

One of the most striking features of the Kincaid 

faunas is the abrupt appearance of the Venericardia. 

Only feebly foreshadowed in the Late Cretaceous of 

the western Gulf, the two major groups of probably 

the dominant genus in the Eocene pelecypods are 

represented in the limestone by eight described species 

and several other species too imperfectly represented 

to name. Among these, four are peculiar to the ~.io 

Grande embayment, all of them coarse, heavy-sheJled 

forms suggesting in-shore waters. 

Venericardia mediaplata has a meager representation 

in the Kincaid formation through Texas to the P.io 

Grande. V. smithii is widely distributed, both in the 

Kincaid formation and in the Wills Point formathn, 

and is locally abundant from Kaufn1an County, Tex., 

south to the Rio Grande. A float specimen carrying 

a fine example of V. smithii was picked up on the Mexican side. 

In addition to these two nmjor races of Venericar-lia 

in the Gulf and Rio Grande Midway, we have recorded 

other species of doubtful relationships. These are all 

of local occurrence, V. smithii and V. mediaplata be~_ng 

the only members of the basal Eocene faunas that are 

at all cosmopolitan in their distribution. 

Venericardia moa is present in the Kincaid of Maverick County, Tex. This form is probably ~loser to 

the V. alticostata group than to the V. planicc~ta 

group, but it is included in this discussion because of 

the possibility of its constituting a link between the 

two major races of the east American Eocene venericards. ·Th~ radials number about 19 and are tripartHe, 

the large central riblet being bordered on each side by a 

smaller riblet. This tripartite condition of the ribr is 

much 1nore characteristic of the alticostata group, l1ut 

the few ribs, their rather low serrations, and the lr.ck 

of strong inflation, especially in the umbonal regi'Jn, 

suggest a fairly close relationship to the planiccsta 

group. 

Venericardia hesperia Gardner, from the Kincaid of 
GEOLOGICAL SURVEY 

10 0 10 '20 30 40 MILES ~~~§§§§~~~~~~~~ 

THE OCCURRENCE OF SPECIES OF THE VENERICARDIA PLANICOSTA GROUP IN THE EOCENE OF ALABAMA. 

PROFESSIONAL PAPER 189 PLATE 29 

EXPLANATION 

D . 

. 

Post-Eocene 

m 

Jackson 

Lisbon and Gosport 

Tall 

~ a hatta 

Hatchetigbee ~ 

B 

Bashi 

Tuscahoma 

Nanafalia 

F7l 

l2d 

Naheola 

Sucarnoochee 

-

Clayton 

20412-39 (Face p. 148) No. 1 
148 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

Medina and Uvalde Counties, is a rather close approach 

to some of the higher variants of V. moa. V. hesperia 

is, however, decidedly larger, much more inflated, and 

less produced posteriorly. This species is probably 

another link in the chain of venericards that flourished 

in the lower Midway but that became extinct with the 

changing ecologic conditions of the upper Midway. 

Venericardia jewelli, also from the Kincaid formation, 

may be related to the Tennessee form V. hijuana. 

V. jewelli is characterized by a ma.rked flattening of 

the shell toward the ventral margin by the few broad, 

simple radials, and by an absence of any well-defined 

sculpture on the posterior area. Some molds of 

V. hijuana suggest a relationship with the Texan species 

much better than the shells themselves. In both species 

the posterior region has very feeble sculpture, and the 

general outline of the shells of the two forms is similar. 

A trace of the early Midway faunas has been noted 

by Miss Maury 28 in the Soldado Rock, off the extreme 

southwest corner of Trinidad, and by Harris 29 in the 

Marac quarry, on the island of Trinidad, and possibly 

2 miles southeast of Poonah, Trinidad. Both the 

planicosta and the alticostata groups are apparently 

represented in these faunas, but from the figures they 

cannot be determined more definitely. Rutsch 298 

records Venericardia parinensis Olsson of the Peruvian 

lower Eocene from the Marac Quarry. 

Liddle30 has recorded "Venericardia planicosta" from 

the basal Eocene at many Venezuelan localities, often in 

association with "Turritella mortoni." In the absence 

of figures, it is impossible to be sure of the identity of the 

shells so named, but it is very possible that the early 

Eocene beds outcropping in Trinidad are present in 

Toas, on the mainland. The one species of Venericardia 

that we have seen from Venezuela is new but has more 

in common with those of the lower Eocene than with 

those of the upper Eocene. 

The correlation of the n1ainland deposits in Brazil and 

Argentina is still in the controversial stage. Our single 

species, Venericardia austroplata, from the generalized 

locality Point Malaspina, cannot be correlated closely 

with any of the North American forms, but it suggests a 

middle Eocene stage of development rather than a 

lower stage. 

The microfaunas and macrofaunas are to a certain 

extent mutually exclusive. In the Wills Point, from 

which so fine a foraminiferal fauna has been described, 

the Mollusca are for the most part rare and little more 

than a greatly reduced Kincaid fauna. This relation 

to the Kincaid fauna is no doubt due in part to the 

28 Maury, C. J., A contribution to the paleontology of Trinidad: Acad. Nat. Sci. 

Philadelphia Jour., 2d ser., vol.15, pp. 28-39,48-53, 57-58,60-68,85-102, pls. 5-13,1912. 

29 Harris, G. D., in Waring, G. A., Notes on the paleontology, in Geology of the 

Island of Trinidad, B. W. I.: Johns Hopkins Univ. Studies in Geology, no. 7, pp. 

99-101, pl. 18, 1926. 

2Da Rutsch, Rolf, Beitrage zur Kenntnis tropisch-amerikanischer Tertiarmollusken, 

4, Die stratigraphische Bedeutung der Venericardia planicosta und ihrer Verwandten: 

Eclogae gaol. Helvetiae, vol. 29, p. 177, 1936. 

ao Liddle, R. A., The geology of Venezuela and Trinidad, p. 182, 1928. 

restriction of the known molluscan fauna of the Wills 

Point virtually to the glauconitic clays directly above 

the contact and in part to the scarcity of mollu?ks in the 

higher beds. With the apparent shallowing of the seas 

and the finer sedimentation in n1iddle and ]ate Wills 

Point time, living conditions may have becc"tJ!e more 

difficult for the mollusks. Whatever may rave been 

the retarding factors, molluscan remains are exceedingly 

rare. The record of the very late Wills Point faunas is 

less incomplete, but no venericards are included in the 

fauna from New Hope, in Freestone County, Tex. 

WILCOX GROUP 

A discussion of the orogenic movements associated 

with the depression of the Gulf of Mexico anc1 with the 

Sabine uplift may seem rather irrelevant to a d~scription 

of the development of the Venericardia planico<Jta group; 

but it is a relevant fact that, whatever the cause, there 

is a marked increase in complexity in Tertiary sedimentation in passing from the east to the west. The 

Alabama area, the site of such intense activity during 

the Paleozoic era, was relatively quiescer.t during 

Tertiary time, and the Eocene formations were laid 

down in more orderly sequence and now exhibit relatively uniform lithology, dip, and width of outcrop. 

On the west side of the Mississippi embaymC3nt, however, there is a conspicuous lack of uniformity in 

materials, thickness, dip, and width of outcrop. 

1'Ioody,31 in his stratigraphic history of the Eocene of 

Louisiana and contiguous territory, has str~ssed the 

variation in the thickness of the Wilcox sediments and 

their close correlation with the structure. His contour 

map 32 of the thickness of the Wilcox sedimo.nts from 

Texas to Alabama also records the anticlinal and synclinal areas. The nomenclature accepted for the Wilcox 

section in Alabama will be followed here, because that 

was the first to be studied with care, and although the 

Wilcox group in this section is thin, it includeR the most 

important marine deposits that are known ncrth of the 

Mexican border. Along the Atlantic ser.board in 

Georgia the shore line was advanced beyond the Midway strand and the marine sediments buriei beneath 

the later nonmarine deposits. The head of the Mississippi embayment was also silting up during this epoch, 

and in Mississippi, as in Georgia and west of the embayment in Louisiana, the Wilcox is for the most part nonmarine; in Texas the marine beds were orly locally 

developed, for the most part at the beginning and near 

the end of Wilcox time. South of the l1<:lrder, in 

Mexico, a superb section, in part marine, in part nonmarine, is strikingly exposed. 

The Wilcox of Alabama has a fourfold, or, if the nonmarine Ackerman formation and the Salt Mountain 

at Moody, C. L., Tertiary history of region of Sabine uplift, La.: Am. Assoc. Petro· 

leum Geologists Bull., vol. 15, no. 5, pp. 531-551; 1 pl., 5 text figs., ccrrelation chart, 

1931. 

12 Idem, fig. 1. 
STRATIGRAPHIC BACKGROUND OF THE VENERICARDIA PLANICOSTA GROUP 149 

limestone are included, a sixfold division. Blanpied 328 

from a study of well logs placed the Salt Mountain limestone in the Wilcox group between the Nanafalia fornlation and the Tuscahoma sand. Cooke 32b corroborated 

this correlation and explained its anomalous position 

adjacent to the Vicksburg group by upthrusting along 

the Jackson fault. At the base of the marine Wilcox is 

the Nanafalia formation, first described by Aldrich 33 

as the "Nanafalia and Coal Bluff section." It is significant that the earliest studies of the Alabama Eoeene 

in sections that have long since become dassic were 

inspired by the interest in the fossils that they carried. 

The Nanafalia fauna is restricted largely to the lower 

20 feet of the Ostrea thirsae bed, the middle arenaceous 

member characterized by the small, plump, and relatively smooth oyster that is abundant through the 60 

feet of sand. Below the Ostrea thirsae reef is the tCoa.I 

Bluff bed of Brantley 84 (the Ackerman of Cooke), a 

series of cross-bedded sands and sandy and lignitic clays, 

for the most part nonmarine and of debatable age. 

Above the Ostrea thirsae reef are 40 to 50 feet of clays 

and sandy clays that tend, particlilarly in west-central 

Alabama, to indurate into a pseudobuhrstone. The 

Nanafalia has been traced from Choctaw County on the 

western line eastward to the Chattahoochee River, 

where, in the bluff at Fort Gaines, Ostrea thirsae beds 

overlie the Clayton formation. 0. thirsae has not, however, been followed beyond Webster County in western 

Georgia. The synchronous deposits in Mississippi are 

nonmarine, but Ostrea thirsae :Qas been found near 

Marthaville, La., on the southern side of the Sabine uplift, possibly also near the border southeast of Eagle Pass 

and on the Mexican side of the Rio Grande. Marine 

sedimentation in the lower Eocene was apparently unbroken in northern Mexico, but there are no venericards 

associated with the abundant Ostrea which so elosely 

resemble 0. thirsae. All along the ancient Gulf shore 

line a deeper-water falma must have been developing contemporaneously with the Ostrea fauna, but only at a few 

localities is it recorded, notably at Nanafalia Bluff, on the 

Tombigbee River, the type locality for the formation. 

Three species of the Venericardia planicosta group 

have been recognized in the glauconitic shell marl 

overlying the Ostrea thirsae beds at Nanafalia Landing. 

The possible descendant of Venericardia mediapl~ta of 

the lower Midway is Venericardia nanaplata, n~ sp., 

a species similar in dimensions and outline to the Midway form, though rather more compressed. The 

general type of ribbing is the san1.e in both, althpugh 

the ribs of V. mediaplata are more numerous by 1 four 

or five and consequently more closely spaced. The 

umbonal sculpture in the Nanafalia forn1 is apparently 

a2a Blanpied, B. W., Guidebook of the Ninth Annual Fieldtrip of the Shreveport 

Geological Society, p. 9, 1932. . 

s21o Cooke, C. W., Notes on the Vicksburg group: Am. Assoc. Petroleum Geologists 

Bull., vol. 19, no. 8, p. 1163, 1935. 

33 Aldrich, T. H., Alabama Geol. Survey Bull. 1, p. 12, 1886. 

"Brantley, J. E., Petroleum possibilities of Alabama, part 2, Southern Alabama: 

Alabama Geol. Survey Bull. 22, p. 148, 1920. 

not so simple as that of the Midway species, but n~des 

at the intersections of the ribs and the growth lines are, 

for the n1ost part, restricted to the five or six anterior 

and the three or four posterior ribs. There is alS'o a 

stronger tendency in the Nanafalia species tovrard 

disappearance of the ribs near the ventral margin and 

a higher, heavier hinge. 

Venericardia aposmithii, the form figured under the 

Greek letter beta in Harris' discussion of the t Lig?Jitic 

faunas, 35 is in its early stages a replica of Venericardia 

smithii, its probable progenitor. The tips of the 

umbones are serrated like those of V. 8mithii, but at a 

later growth stage, in V. aposmithii, lateral ridges are 

developed which unfortunately are not clearly shown 

in the Harris figure. The ·type of V. smithii shows 

nothing of the sort-only high, acutely V -shaped ridges 

cresting the ribs. The number of ribs in aposmithii 

runs 28 to 36, the highest of all the members of the 

smithii stock. The hinge plate is adjusted to the righ, 

heavy shell, and the heavy right cardinal is a scimitar 

in shape. A third species, Venericardia pilsbryL on 

which Stewart founded his Leuroactis, may have arisen 

from some remote mediaplata radical, but the relationships are by no means certain. In any case, V. pil~bryi 

is an uncommonly well characterized species, with 

compressed beaks and narrow hinge plate, with a rib 

count running as high as 39, and with these numw~ous 

ribs separated by linear interspaces. 

The faunal integrity of the lower Wilcox is indicated 

by the continuation into the Tuscahoma of each of the 

three Nanafalia species of venericards. They are, 1' ~wever, restricted in their known distribution to AlabtLma. 

The Tuscahoma sand, described by Langdon 36 from 

Tuscahoma Landing, on the Tombigbee River, is a 

series of shallow-water sands and sandy clays, in large 

part nonmarine, extending entirely across the State 

and including the two classic outcrops at Greggs and 

Bells Landings on the Alabama River. These two 

1narl beds have received member names, and in the 

early sections taken at Bells Landing the Greggs Landing marl was reported to crop out at the water's edge 

about 25 feet below the Bells Landing marl. In the 

later sections, however, this member is reported to be 

concealed. The faunas are very similar, but there are 

facies differences, and only three out of the five venericards present at Greggs Landing have been recovered 

from the higher Bells Landing member. The only 

abundant species common to both is the ponde"'ous 

V. aposmithii, enormously plentiful at both Greggs and 

Bells Landings but not recognized in the western Gulf. 

Although three of the Tuscahoma species ,~Tere 

already present in the Nanafalia, there are in the 

Tuscahoma race modifications not sufficiently marked 

to be recognized in the taxonomy nor of consist.ent 

36 Harris, G. D., The Lignitic stage, pt.1, Stratigraphy and Pelecypoda: Bur. Am. 

Paleontology, vol. 2, no. 9, p. 55, pl. 9, fig. 1, 1897. 

36 Langdon, D. W., Jr., Variations in the Cretaceous and Tertiary strata of Alabama: Geol. Soc. America Bull., vol. 2, p. 596, 1891. 
150 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

value in determining single individuals but of a certain 

weight in a long series. The rib count in the Tuscahoma nanaplata is higher by 2 or 3 than in the N anafalia, the noding pattern of the umbonal ribs is continued over a greater extent, and there is a much 

stronger tendency toward the evanescence of the ribs 

near the ventral margin. There are, however, intermediate forms that would be of no aid in interpreting 

a stratigraphic section. 

One of the most abundant forms in the Tuscahoma 

sand at Greggs Landing is a small variant of the nanaplata race that has been designated Venericardia nanaplata nanna. This differs from the true nanaplata in 

the greater number of ribs, smaller si.?;e, and more 

compressed outline. 

Venericardia aposmithii from the Tuscahoma is 

larger, higher, and heavier than the form from the 

Nanafalia, and the tendency toward the evanescence 

of the anterior and medial ribs is stronger, but the 

pattern of the ribbing is similar both on the disk and 

on the posterior area, and in both the Nanafalia and 

Tuscahoma individuals the umbones are ridged and 

serrate and carry at least obscure traces of lateral terracing. The apparent restriction of this form to the 

Alabama sections may be due to the burial in other 

regions of the deposits in which it would be preserved, 

or it may be that Alabama represents the southern 

and western extension of its range. This is suggested by the prominence of the very similar species 

Venericardia regia Conrad in the probably synchronous 

greensands of the Aquia formation of Maryland and 

Virginia. There are . differences in the outline and 

sculpture of Venericardia aposmithii and V. regia that 

justify the retention of distinct names for the two 

forn1s, but the resemblances are sufficiently striking to 

suggest a basis for correlation. 

Another distinctive descendant of the smithii stock 

at both Greggs and Bells Landings is Venericardia 

greggiana Dall, a species that exhibits a more ornate 

ribbing than its progenitor in the Midway. This species has a very narrow stratigraphic range, apparently 

having reached its culmination and extinction in the 

Tuscahoma sea. . 

Plant fragments are com1non throughout tlie Tuscahoma, and the first recorded deposits of the Bashi formation on the Alabama River are carbonaceous. Thin 

seams of lignite record continued lagoonal conditions 

during middle Bashi time, but the 15 to 20 feet of 

glauconitic marl at the top is packed with the remains 

of a prolific shallow-water fauna. In this formation, 

as in the Tuscahoma, the outcrop most renowned 

faunally is not that which has given an accepted name 

to the formation. The Bashi, named by Langdon 37 

from Bashi Creek, a tributary of the Tombigbee River 

in northern Clarke County, was best known among 

the earlier paleontologists as the tWoods Bluff beds, 

37 Langdon, D. W., Jr., op. cit., p. 596. 

from Woods Bluff, 1 mile in an air line below the nwuth 

of Bashi Creek. The outcrop that has furnisr~d prized 

material for collections all over the world is now covered by backwater from a recently constructed dam. 

The marl beds tend to indurate and weather into 

characteristic pillow-shaped 1nasses of Inarlstone, by 

which they can be recogmzed even in the absence of 

diagnostic fossils. 

Although nonn1arine conditions were prevalent in 

Alabama during a large part of Bashi time, the Bashi 

marked elsewhere a period of expansion of tl'A. Wilcox 

seas, particularly to the south, and a very considerable 

change in the make-up of the molluscan faunas. Deposits of Bashi age are recognizable by their Vfnericards 

from western Georgia to Souwashee Creek anc1

. Purd ues 

Cut, south and southeast of 1\.1eridian, 1\.1iss., and fron1 

Sabinetown, on the Texas side of ~he Sabine River, to 

northern Nuevo Le6n, Mexico. It is possible that 

embayments of ·the Bashi sea existed on the Atlantic 

side of the mid-Americas and that there were synchronous marine deposits in northern Peru. 

Venericards of the planicosta group related to those 

from the Nanafalia and Tuscahoma have be-:m determined from the Bashi, but no identical sper:-.ies have 

been recognized. 

Venericardia bashiplata, n. sp., the dominant representative of the group, is apparently in the direct line 

of descent from Venericardia mediaplata of the lower 

Midway. The species is generally larger than V. 

nanaplata of the Tuscah01na, the un1bones are high 

and broad, the posterior area is rather obscurely defined, and the ribs are elevated but not ridged upon 

their summits and show no trace of lateral terracing. 

The valve with the reversed dentition (pl. 34, fig. 4) is 

an example of this species. Venericardia bashiplata has 

been recognized near the Alabama line in Stmvart 

County, Ga.; at numerous localities in Alaban1a; near 

Meridian, Miss.; on the Texas side of the Sabine River; 

and in northern 1\tlexico. Venericardia ascia of the 

Nanjemoy of Maryland and Virginia may be a northern 

relative. 

A species commonly associated with Ver~ricardia 

bashiplata but less widely distributed is that figured by 

Harris 38 under the Greek letter gamma and described 

by the senior author from Sabinetown, Tex., under the 

name "V. horatiana." The ancestry is rather obscure, 

though it may perhaps be related to Ve1"ericardia 

pilsbryi Stewart, a possible lateral offshoot C'f mediaplata of the early Eocene. The extreme tir~ of the 

umbones of horatiana show no trace of radial sculpture, only a strong concentric rippling suggesting 

Astarte or Crassatellites. Not only are the r?.dials of 

horatiana absent in the initial stages, but they evanesce 

usually about one-third of the distance from the umbones to the anterior margin of the adult she1l. They 

number no more than 22 to 25 and are separated by 

as Harris, G. D., Bull. Am. Paleontology, vol. 2, no. 9, p. 55, pl. 10, figs. 1-4, 1897. 
STRATIGRAPHIC BACKGROUND OF THE VENERICARDIA PLANICOSTA GROUP 151 

linear interradials. There is a probable descendant of. 

horatiana in the lower Claiborne, but the Bashi species 

may be separated fr01n its descendants by the less 

inflated tips and less pronounced twist of the umbones. 

The V. aposmithii stock apparently left no direct 

descendants in the upper Eocene of the eastern Gulf. 

Venericardia potapacoensis, from the Nanjemoy of 

Maryland and Virginia, has no close analog an1ong the 

described species from the eastern Gulf. The ribbing 

is tripartite in its early stages, and the form is perhaps 

more closely related to V. smithii than to the mediaplata stock. The curiously lop-sided outline of potapacoensis is shared by the diga of northern Mexico. 

The end of the Bashi epoch was marked by continued 

emergence and by a withdrawal of the planicosta fauna 

fr01n much of the Gulf province. Even in Alaban1a, 

the Hatchetigbee formation is in large part nonmarine. 

The type locality for which Langdon 39 named the 

formation is Hatchetigbee Bluff, on the Tombigbee 

River, 3 miles south of the Choctaw County line. The 

fossil-bearing bed is a sandy n1arl about 5 feet thick 

underlain by 15 feet of clay and overlain by about 70 

feet of clays and sands, some of them marine and 

sparsely fossiliferous, some of them lignitic. The 

general color of the clays is brown rather than gray. 

In the eastern part of the State the outcrop of the 

Hatchetigbee is interrupted by overlap. To the west 

it is continued across the State line into Lauderdale 

County, Miss. 

Three species of the Venericardia planicosta group 

are recorded from the shallow Hatchetigbee sea-the 

abundant Venericardia hatcheplata, n. sp., of the simpleribbed stock; Venericardia horatiana, first recorded 

fron1 the Bashi; and Venericardia turneri, n. sp., 

poseibly of the same stock. Venericard-ia hatcheplata 

possesses rnore ribs than its probable Bashi ancestor, the 

outline is usually more cordate, and the hinge plate is 

higher and heavier. The species is abundantly represented at Hatchetigbee }3luff,- but single valves occur 

only rarely. The hinge teeth are so large and so closely 

interlocked that they are usually broken in forcing the 

valves apart. Venericardia turne1·i is a curiously 

quadrate form with evanescent. ribbing, having no 

known progenitors, descendants, or synchronous related 

species. 

In recapitulation, the intimate relation between the 

faunal distribution and the distribution of the sea and 

the land cannot be too strongly stressed. The Wilcox 

faunas of the eastern Gulf are essentially provincial. 

They lived and died and were buried in shallow waters 

that were in sOine manner and to some degree isolated. 

Because of the greater interest in the marine beds, 

attention has been focused largely upon them, and it is 

easy to be indifferent to the minor role that they fill 

in a general section that was during Wilcox time, even 

in Alabama, dominantly nonmarine. Even those beds, 

39 Langdon, D. W., Jr., op. cit., p. 597. 

such as the Greggs and Bells Landing members of the 

Tuscahoma, which in western Alabarna carry exce~lent 

faunas are nonmarine in eastern Mississippi, and 

indeed the Mississippi Tertiary deposits are in htrge 

measure the discharge from an ancestral MissisE"1opi 

River. The volun1e of fresh water poured out nust 

have been an important factor in the ecology along 

the nearby shores, and the in-shore faunas, depending 

for their continuity upon a moderately stable salinity, 

led a precarious existence. The struggle in that section 

was not so much between the sea and the land as 

between the sea and probably the greatest of the 

eastern rivers and was carried on along an exceedingly 

narrow front. A slight advance of the fresh water 

involved the destruction of the fauna within the 

restricted area recorded in the sections open to us. 

Only in the Middle Wilcox is there evidence that the 

faunas of the eastern Gulf, represented fairly by the 

venericards, were anything more than faunules S€,~egated in some circumscribed bit of lagoonal shore and 

not in long-continued direct communication with those 

of the western Gulf or the Atlantic seaboard. 1\1ore 

cosmopolitan assemblages must have been flourishing 

off shore, but of these we have no record. 

CLAIBORNE GROUP 

From more than one point of view the Claiborre is 

the most important of the four Eocene groups. The 

rnarine faunas of the Lisbon, the middle formation, 

mark in many areas the outposts of the transgreEsive 

Eocene sea. Barriers, both land and fresh wr,ter, 

which had been in existence since early Eocene time 

were eliminated and, in sharp contrast to the few late 

Wilcox faunas recorded, the Lisbon takes on a coEmopolitan air. It is, however, the fauna of a local~zed 

lens of sand at the extreme top of the Claiborne that 

has been world-renowned since the days of the Conrad-

-Lea struggle for prior publication in the early 1830's. 

This remarkable sand was trenched by the Alab.<~,ma 

River and in recent years has been well exposed at 

another locality by a highway, so that optimum conditions for collection prevail-indeed, have prevdled 

since the beginning of geologic investigations in the 

Gulf Coastal Plain. Both of these justly famous fossiliferous zones may fall within the upper third of the 

Claiborne section in Alabama. The lower two-thirds of 

the section is largely nonmarine. A fairly well marked 

erosion interval is postulated between the Wilcox and 

the Claiborne, and the Tallahatta formation, at the 

base of the Claiborne, thins from several hundred feet 

near the axis of the Mississippi embayment to not 

more than 20 feet at the Georgia line. It has little to 

offer in the way of a fauna, 39a for even the marine phases 

are made up largely of barren sands. In Alabama the 

break in the records of life includes not only the break 

39a Rerent investigations indicate that the fauna or the Tallahatta of e'lstern 

Alabama is larger than has been commonly supposed. 
152 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

between the Wilcox and the Claiborne but also most of 

Tallahatta time. 

The Tallahatta buhrstone of Smith 40 was so called 

from the Tallahatta Hills, in Choctaw County, which 

owe their existence to the aluminous quartzitic sandstones that make up a large part of the Tallahatta formation. The indurated sands cropping out in northwestward-facing scarps are most prominent in the 

western part of the State. To the east the beds are 

not so hard, are more argillaceous, and carry a higher 

calcareous content. Oysters have been reported fron1 

a number of localities but our faunal records from the 

Tallahatta formation are meager and inconclusive. 

Smith remarked that "they are always poor in fossils 

except the microscopic siliceous shells of marine diaton1s 

and Radiolaria." However, glauconite is a fairly rare 

constituent in Alabama and still rarer in Mississippi. 

In Mississippi "the prevailing rocks of the Tallahatta 

formation are white, gray, or cream-colored brittle 

claystone or diatomaceous earth, interbedded with hard 

gray sandstone or quartzite. A peculiar breccialike 

rock composed of patches of claystone enclosed in 

coarse sandstone is not uncommon. " 4J The strike of 

the Tallahatta swings up the Delta, and in Grenada 

County the formation is buried beneath the loess. No 

certainly determinable venericards have been recognized in the Tallahatta. 

The succeeding Lisbon formation of Smith was described from Lisbon Bluff on the Alabama River, a 

few miles above Claiborne. 

Between the Buhrstone and the base of the Gosport sand are 

the Lisbon beds, consisting of about 115 feet of calcareous clayey 

sands and sandy clays, generally fossiliferous. The lower half of 

these beds contains a great number and variety of well-preserved 

shells; in the upper half the shells of Ostrea sellaeformis and several 

species of Pecten greatly preponderate over other forms. 42 

It is interesting that the first definition of the fornlation so clearly establishes the relationship of the two 

most characteristic and wide-ranging Lisbon bivalvesOstrea sellaeformis and Venericardia densata. Both of 

these species can be traced westward across Mississippi 

and Louisiana, through Texas, and well into northern 

Mexico. 

The Lisbon and its time equivalents represent the 

maximum extension of the Claiborne sea, and the extent 

of that sea is reflected in the widely distributed faunas, 

in marked contrast to the provincial aspect of the Hatchetigbee. The abundantly fossiliferous bed both in 

the Lisbon of Alabama and in the equivalent beds to 

the west is near the top of the formation as it is exposed 

along the Alabama River. Venericardia densata Conrad, a heavy but rather small species with strong dentition and ribs well noded along the summits and strongly 

to Smith, E. A., Underground water resources of Alabama, p. 17, Alabama Geol. 

Survey, 1907. 

u Stephenson, L. W., The ground-water resources of Mississippi: U. S. Geol. 

Survey Water-Supply Paper 576, p. 50, 1928. 

42 Smith, E. A., Underground water resources of Alabama, p. 18, Alabama Geol. 

Survey, 1907. 

undercut laterally, is the most common venericard in 

the Lisbon and the most widely recorded. This may 

be a descendant in the V. smithii line. Although intermediate forms have not been observed in th~ Wilcox 

of Alabama, they are suggested in forms from the 

Pendleton Ferry section on the Sabine River, beds probably synchronous with the Tuscahoma. · In r.ny case, 

the stunted look and heavy hinge of V. densata suggest 

an advanced stage of development rather thr.n a new 

stock. In the long interval between the Tuscahoma 

and Lisbon epochs, the evolutionary lines were obscured, 

and with the material available the line of descent is 

speculative. The simple ribbed stock seems to be 

represented in the Lisbon by Venericardia ckiboplata, 

a higher and more inflated species than ha.tcheplata 

and of all the American forms, the one mort nearly 

approaching planicosta s. s. of the Paris Basin. This 

stock is characterized in the lower Eocene by simple 

ribbing, but in some individuals there is a shar) change 

in direction of the incren1ental striae along th~ side of 

the rib, especially on the anterior surface or the inflated umbonal area. A faintly raised thrrad n1ay 

sometimes, even in the lower Eocene forms, be developed along these successive angles in the incremental 

striae. In the Lisbon species this raised laterr.l thread 

is a not uncommon but incidental character, but in the 

later Gosport it con1monly persists from the juvenile 

serrate stage through the adolescent. The clo~e of the 

adolescent stage is usually indicated by a prominent 

resting stage, and the adult ribbing is simple. In 

V. densata, however, the ribbing pattern is uniform and 

a constant specific character, whereas in Venericardia 

claiboplata there is much more individual var:~fttion. 

A less conspicuous but well-characterized and. widely 

distributed group is that which is apparently in the 

line of descent from Venericardia horatiana of the 

upper Wilcox. V. stewarti, like its possible progenitor, 

has been recovered both from the western Alabama 

sections and from that on the Sabine River. It is not 

easy to understand why it should be more readily recognizable and separable from V. horatiana by its juvenile 

sculpture than by any adult characters. Venericardia 

tonosiensis from strata of presumable Claiborn~ age on 

the Isthmus of Panama, represents a souther."l extension of the group and is in turn remarkably like 

V. pacifica Olsson, from the Salina formation of northern 

Peru, a species compared by Stewart to his V. cala.fia, 

from the Domengine of the Simi Valley of southern 

California. Venericardia pilsbryi may be continued 

in the rare V. angustoscrobis from Lisbon Land:.ng. 

The history of the Claiborne north and eat:'t of the 

Alabama section is n1uch more simple than thtt west 

and south of it. The characteristic Tallahatta deposits 

feather out near the Chattahoochee River, and the 

Gosport sand has been recognized only in western Alabama. The McBean forn1ation, which includes all of 

the Claiborne of eastern Georgia and South Carolina, 
STRATIGRAPHIC BACKGROUND OF THE VENERICARDIA PLANICOSTA GROUP 153 

is the approximate equivalent of the Lisbon of Alabama, 

thus indicating that only during middle Claiborne time 

was the Atlantic seaboard submerged, and although the· 

sea encroached ahnost to the Fall Line on the west, to 

the north it extended only as far as the Santee drainage 

basin. It is possible that there was also during middle 

Claiborne time a short marine invasion in east-central 

New Jersey and that the record is contained in the Shark 

River marl. The McBean formation, so called from 

the town of McBean, near the Savannah River in 

east-central Georgia, was named and defined by 

Veatch and Stephenson in 1911.43 

Th~ formation consists mainly of clays in the nature of fuller's 

earth, shell marls, sandy limestones, and calcareous glauconitic 

sands. The marls are for the most part massive-bedded and 

friable, but hard, compact, and even partially silicified beds 

were noted on Savannah River. They may also be represented 

by alternate layers of marl or calcareous sand and laminated 

clay. 

In South Carolina, according to Cooke,434 the McBean 

extends eastward as far as Calhoun County. 

The McBean formation, which includes the fossiliferous Claiqorne of eastern Georgia, is best developed 

in the northeastern area of the Tertiary outcrop near 

the South Carolina line/3b and even there very few 

detern1inable specimens of the Venericardia planicosta 

group have been recovered. The species most commonly represented, V. claiboplata, though rare in 

Georgia, is abundantly represented in South Carolina, 

particularly in the vicinity of Orangeburg and of 

Cawcaw Swamp. These South Carolina venericards 

show certain constant differences from the Alabama 

forms, differences which may, however, be unduly 

exaggerated by the character of preservation in the 

South Carolina species. The limy shells have been 

invariably replaced by silica, and certain details in the 

sculpture have been exaggerated while others have been 

obscured. However, the umbones are less prominent 

and less incurved, and the shell as a whole is more compressed in the South Carolina specimens than in those 

from Alabama; the posterior area is more sharply cut 

off both by the contour and by the sharper, narrower 

costals persistent to the margin. The larger individuals show certain senile characters, such as the 

obsolete anterior and medial ribbing. From Venericardia hatcheplata, which some of the larger individuals 

resemble in both the transverse and the verti-cal outline of the valves, the South Carolina race is separable 

by the much more sharply and persistently ribbed 

posterior area. 

The Claiborne and Jackson sedimentation west of 

the standard Alabama section was more sandy than 

that to the east and offered on the whole a more favoru Veatch, J. 0., and Stephenson, L. W., Preliminary report on the geology of the 

Coastal Plain of Georgia: Georgia Geol. Survey Bull. 26, p. 238, 1911. 

cao Cooke, C. W ., Geology of the Coastal Plain of South Carolina: U. S. Geol. Survey Bull. 867, pl. 2.,1936. 

m Cooke, C. W., op. cit., pp. 55-72. 

able environment to the larger bivalves. In Mississippi 

the succession is similar in a general way to thr.t in 

Alabama. The Lisbon includes the ola tWautubbee 

marl, characterized faunally by an abundance of 

Ostrea sellaejormis. 

There is no faunal evidence that the Claibornr. sea 

extended up the embayment to the present site of 

Arkansas, but matine Jackson beds have been rf"}ognized as far north as Crowleys Ridge, across the river 

from Memphis, Tenn. The head of the embay1nent 

was silting up in the meantime, and no marine middle 

or upper Eocene· has been recorded from Tennesst'~ or 

Kentucky. 

The available material that covers the plani~osta 

group in Louisiana is not representative. In the 

glauconitic sands of the Cane River,44 the lowest of the 

Claiborne deposits in Louisiana, no determir.q,ble 

planicosta were observed. The sea, after the s1ight 

advance indicated by the Cane River, again withdrew, 

but in the succeeding lower Claiborne time 46 a marine 

invasion synchronous with that of the Lisbon of 

Alabama swept along the east side of the Sabine uplift 

but did not isolate it. The scattered representr.tion 

of the two most common Lisbon members of the 

planicosta group, V. densata and V. claiboplata, reflects 

the inadequacy of our collections rather than the 

absence in Louisiana of good fossiliferous outcrops of 

Cook Mountain (St. Maurice of Spooner). In Texas 

the distribution of venericards is much more gen~ral, 

both stratigraphically and areally, but we have been 

disappointed that we have not been able to correlate 

more closely the wide range of individual variaticn in 

densata, the most abundant and widely distrib,lted 

species, with the established sections. In the Rio 

Grande e1nbayment, on the other hand, possibly because the section thickens and ecologic conditions were 

less uniform, the variations make much better tool" for 

excavating in the past. In his study of the Lutetian 

of the Paris Basin, with which the Lisbon is comm<)nly 

correlated, Abrard 46 believed that he had in Venericcrdia 

planicosta an exceedingly valuable indicator of a transgressing sea, that the abundant occurrence of the sp~cies 

was evidence of the base of the stage, whether of the 

lower or of the upper Lutetian, but that he had never 

found it in the upper Lutetian at a locality in whicl' the 

lower Lutetian was present-in other words, that it 

played no part in a recurrence of the fauna. 47 We 

have no records in the Texas outcrops, at least in those 

north of the Rio Grande embayment, of such extraordinary abundance as that of densata at Lisbon I~luff, 

nor do we have, except in the Mexican part of the Rio 

Grande embayment, the association, also reminiE'cent 

u Spooner, w. C., Interior salt domes of Louisiana: Am. Assoc. Petroleum Geolo· 

gists Bull., vol. 10, no. 3, p. 235, 1926. 

46 Harris, G. D., Pelecypods of the St. Maurice and Claiborne stages: Bull. Am. 

Paleontology, vol. 6, p. 6, 1919. 

46 Abrard, Ren6, Le Lut6tien du bassin de Paris, 388 pp., 32 text figs., 4 pis., .4 

maps, Angers, 1925. 

n Idem, p. 210. 
154 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

of Lisbon Bluff, with Ostrea sellaeformis. The lower 

Claiborne of Texas, which includes the Mount Selman 48 

and Cook Mountain,49 records three major submergences 

of the land below the salt water. These diastrophic disturbances are involved with the Sabine uplift, and in 

fact the history of the lower Claiborne in north and 

east Texas is the story of the loading of the trough 

to the north and west of the Sabine ,uplift and the progressive emergence of this trough from the north to the 

south. The early Claiborne sea lapped the shores of 

the present Sabine uplift but did not advance over it. 

North of the uplift the beds are for the most part 

nonmarine, for that area suffered only two short 

invasions of the sea-one near the beginning of the 

Claiborne epoch, the other toward the end of the 

Mount Selman epoch. The Reklaw 50 is characteristically a coarse, highly oxidized glauconitic sand or a 

blackish-brown micaceous pyritiferous clay, with or 

without fine sand and commonly with stringers of 

glauconite. The coarseness of the glauconite and the 

high oxidation are evidence of a long-continued period 

of equilibrium, and along the northern and western 

margins of the Sabine uplift reworked balls of the Wilcox clays beneath are associated with the contact. 

The basal contact, especially in northeastern Texas, is 

coincident with an abrupt change from the relatively 

low relief of the Wilcox to the more rugged topography 

of the Claiborne. The Reklaw roughly parallels the 

Cretaceous-Eocene contact and shares with it the 

abrupt change in strike. It has been correlated with 

the lower part of the Cane River of Louisiana and 

traced south to the latitude of San Antonio and correlated with the Bigford 51 of the Rio Grande embayment. The Reklaw venericards are rare and imperfectly preserved. V. claiboplata was identified from a 

mold of the exterior recovered from the indurated 

ferruginous sandstones east of the Capote IIills, in 

Gonzales County. The venericards from northeastern Atascosa County, near Leming, are probably identical with V. claiboplata, but they are all juveniles, and 

the molds are not very sharp. In the locality which 

has furnished by far the best lower~Mount Selman fauna, 

the section across the river from Upton, on the Colorado 

in Bastrop County, small gastropods dominate the 

fa1,1na; the environment was obviously unfavorable to 

the venericards, and only a few young V. densata have 

been observed. Not even a fragment of a planicosta 

rib was recovered, however, in the extensive collections 

of marine Bigford material made by James R. Day in 

Webb County. Both the clays near Upton and those 

of the Bigford of Webb County indicate soft-bottom 

lagoonal or in-shore conditions, an ecology unsuited to 

48 Kennedy, William, Texas Geol. Survey 3d Ann. Rept., pp. 52-54, 1892. 

o Idem, pp. 54-57. 

~o Wendlandt, E. A., and Knebel, G. M., Lower Claiborne of east Texas, etc.: 

Am. Assoc. Petroleum Geologists Bull., vol. 13, p. 1352, October 1929. 

BI Trowbridge, A. C., A geological reconnaissance in the Gulf Coastal Plain of 

Texas near the Rio Grande: U. S. Geol. Survey Prof. Paper 131-D, p. 92, 1923. 

shells so heavy as those of the large venericar-ls. The 

Queen City 52 records the accumulation, in the east 

·Texas trough and on the emergent shores, of fine sandy 

materials, for the 1nost part derivatives from the 

Wilcox sedin1ents. It is largely nonmarine and rarely 

fossiliferous. 

In southern Texas nonmarine conditions persisted 

through early Claiborne time at the head of the Rio 

Grande embayment, but in northern and eastern Texas 

the so-called East Texas syncline suffered a second 

early Claiborne invasion, from waters that left their 

record in the thin, highly ferruginous cappirg of the 

Quee~ City Hills, the northern outpost of the W eches 

sea. 

The Weches,53 the upper marine beds of th'-1 Mount 

Selman, are the most in1portant beds of the formation 

in point of thickness and composition, con1IJ1.ercially, 

scenically, and faunally. They carry an extnwrdinary 

an1ount of glauconite, most of it oolitic, which by the 

leaching out of the potash and the concentrll.tion of 

the iron has been altered to a low-grade but commercially promising iron ore. These indurated ar<l highly 

resistant ferruginous beds cap the Queen City Hills on 

the dissected divides in eastern Texas and giYe rise to 

the long red slopes so closely associated with the area. 

The section of more than 200 feet exposed east of the 

town of Mount ·Selman, in Cherokee County, is not 

excelled in t,he Claiborne of Texas. The W eches 

thickens abruptly in the latitude of Henderson, Rusk 

County, both on the Texas side of the Sabine uplift 

and, to a lesser degree, on the western n1.arg:n of the 

bordering syncline. Though the formation ranges in 

thickness from 5 feet on the northern flank of fhe uplift 

to almost 400 feet on the southern flank, the general 

character of the sediments remains the same-a 

ferruginous sandstone, commonly oolitic and glauconitic, with occasional lenses and stringers of intercalated clays-a shallow-water deposit laid down for 

the n10st part south of the uplift on a sinking bottom. 

South of the Colorado River the W eches is not so well 

individualized, and in the Rio Grande en1bayment it 

is largely estuarine and lagoonal. On the Mexican 

border the Mount Selman is largely a gypsife:rous clay 

with interbedded sands and sandstones and a few thin 

lenses of gray concretionary limestone, and the sequence 

comprehends over 1,150 feet in maxinlum thickness. 

A. few poorly preserved Mollusca, but no ver~ricards, 

have been collected in Webb County directly above 

the Bigford. The Mount Selman is for the most part 

nonmarine on the Texas side of the Rio Grr.nde embayment, but in northern Mexico V. densata may be 

present. The Mexican material, though fairly abundant, is poorly preserved and inconclusive. Molluscan 

imprints are common in the eastern Texas iron ores, 

but well-preserved shells have been recovered C'nly from 

u Kennedy, William, Texas Geol. Survey 3d Ann. Rept., p. 50, 1892. 

11 Wendlandt, E. A., and Knebel, G. M., op. cit., p. 1356. .. 
STRATIGRAPHIC BACKGROUND OF THE VENERICARDIA PLANICOSTA GROUP 155 ja 

the softer unindurated layers, notably in San Augustine 

and Nacogdoches Counties and at Smithville, on the 

Colorado. Both Venericardia densata and V. claiboplata have a scattered representation in the greensands from the Sabine to the Colorado and, though 

widely distributed, are nowhere conspicuously abundant. The shells of both species are relatively thin 

and not large. The W eches epoch was followed by a 

short emergent period in which the Sparta sand,S4 

probably in large part a derivative of the Carrizo and 

Queen City, was deposited by wind and stream action 

and rolled along by the advancing waves of the Cook 

Mountain sea. . The Sparta ha.~ a more limited extent 

than the Queen City-largely, perhaps, because it is 

a loose sand, readily blown by the wind, over which 

no protective cover has been laid down and which has 

suffered greatly fron1 the destructive forces of erosion. 

It has not been followed beyond eastern Atascosa 

County, and it carries no established record of marine 

life. 

By the beginning of Cook Mountain time the emergence of the former East Texas syncline had so far progressed that the Cook Mountain sea did not enter it; 

at least, no trace of the Cook Mountain 55 has yet been 

observed north of the somewhat inadequate type 

locality, Cook Mountain, 2 miles west of Crockett, in 

Houston County. Marine deposits of Cook Mountain 

age flank the south side of the Sabine uplift, however, 

and extend westward along the normal line of outcrop 

to the Rio Grande and into Mexico. The glauconitic 

sands and marls, which make up a large part of the 

formation, both in the Brazos River and Wheelock 

outcrops and in the breaks of the Rio Grande, have 

furnished paleontologic type specimens for most of those 

who were working during the early years on the Tertiary beds of Texas. Many of Gabb's types, and quite 

possibly Conrad's Venericardia moorei, came from the 

vicinity of Wheelock, in Robertson County. Those 

described in the Southern Pacific Railroad reports by 

Conrad came from the glauconitic sandstone below 

Laredo. Ostrea sellaeformis has been observed in a 

reef outcrop only at Stone City, although there is no 

obvious reason why the depositional conditions of the 

Cook Mountain, particularly of the Rio Grande section, should not have been favorable for oyster growth. 

In Mexico Ostrea sellaeformis is found in abundance. 

Venericardia claiboplata has not been recorded from 

the Cook Mountain in Texas, although it is probably 

present in northern Mexico. Specin1ens of V. densata 

indistinguishable from those recovered from the W eches 

of Anderson and Houston Counties are not uncommon 

at Wheelock and Moseleys Ferry, on the Brazos. Both 

at Wheelock and at Moseleys Ferry small gastropods 

are particularly abundant, and the relationship of the 

64 Vaughan, T. W., A brief contribution to the geology and paleontology of north 

western Louisiana: U.S. Geol. Survey Bull. 142, pp. 25, 26, 1896. 

u Kennedy, William, op. cit., pp. 54-57,1892. 

Claiborne faunas at these localities to the faunas r.bove 

and below them have been greatly clarified by the careful study of Renick and Stenzel. ~ The cornmon 

V. densata of the Rio Grande section is larger, more 

trigonal, more compressed, and resembles more closely 

the densata from Lisbon Landing than those fron the 

W eches. In both the Brazos and the Rio Grande sections the occurrence of densata is apparently rest1·icted 

to the lower half of the Cook Mountain, so that the 

differences between the forms from the Cook Mountain 

and from the Weches probably indicate two basi"lls of 

deposition, each isolated from the other by a barrier 

that was at least intermittently effective. The Brazos 

River embayment seems to have been the greater loser 

by the isolation, for the Cook Mountain fauna of tha"t 

area is more remote from the faunas of the ea~tern 

Gulf and more largely a development in place £ron the 

W eches fauna. No veneri~ards except those pres€.nt in 

the Weches have been reported even in the high Cook 

Mountain of the Brazos, while in the Rio Grande embayment two and possibly three new venericards are 

present in the later Cook Mountain sandstones. Both 

V. zapatai and a small unnamed variant, also fron1 

Zapata County, Tex., are related to V. densata, but 

V. cacamai more probably sprang from the claiboplata 

stock. There is not yet any record of any n1embQ,r of 

the V. horatiana group in the Rio Grande embayr.ent, 

although it is represented on the Isthmus of Panama. 

In Chiapas, Mexico, less than 10 miles behind the 

mountain front, a fauna extraordinarily sin1ilar to that 

of the Simi Valley of southern California is clearly 

recorded. A north Peruvian fauna includes a Venericardia pacifica closely approaching V. tonosiensis. A 

California species, V. calafia Stewart, also from the 

Simi Valley, was considered comparable with V. 

pacifica by Stewart. The eastern shore line of S')uth 

An1erica, however, had apparently emerged, for no 

marine Claiborne fauna is recorded in Brazil or Argentina. The Venericardia plar.icosta reported by Liddle 57 

from local limestone lenses of the Misoa-Trujillo fol'rnation in both eastern and western Venezuela suggest';' the 

lower Eocene rather than the middle. 

The Gosport 758 was described by Smith as the Gorl)ort 

greensand. It seems particularly fortunate that the 

man whose name was so long and so honorably as~oci.:. 

ated with the State of Alabama should be the author 

of the best-known Alabama Tertiary formation. 

This division, which, so far as yet known, does not appear in 

any other of the Gulf States, embraces the strata of Claiborne 

group lying between the top of the Lisbon and the base cf the 

St. Stephens. The beds are in general highly glauconitic sands 

about 30 feet in thickness at the Claiborne and Gosport Hluffs 

56 Renick, B. C., and Stenzel, H. B., The lower Claiborne on the Brazos River, 

Texas: Texas Univ. Bull. 3101, pp. 73-108, 1931. Stenzel, H. B., A new formation 

in the Claiborne group: Texas Univ. Bull. 3501, pp. 267-279, 1936. 

57 Liddle, R. A., The geology of Venezuela and Trinidad, p. 182, 1928. 

67a Shown by latest work or C. W. Cooko to be a facies of the Moodys marl. 
156 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

and include the fossiliferous greensands which have made the 

name Claiborne famous and which have furnished the greater 

part of the Claiborne fossils described and figured by Conrad 

and Lea. While this division, as above mentioned, is not known 

in Mississippi, Louisiana, or Texas, yet its importance in Alabama, from the historical point of view and because of the great 

number and variety and beautiful state of preservation of its 

fossils, is such as to compel mention and a distinct name. * * * 

The name is from Gosport, a landing on the Alabama River a 

few miles below the Claiborne Bluff.ss 

The upper Claiborne fauna is remarkable for the 

abundance and diversity of the smaller gastropods. 

The environn1ent was not, however, particularly favorable to the venericards, and their representation is 

relatively unimportant. 

The only n1ember of the planicosta group clearly 

recorded from the Gosport sand is a form so closely 

allied to V. claiboplata that it does not seen1 reasonable to recognize differences so inconsequential in 

taxonomy. It -1s notable, however, that the tendency 

toward a lateral threading in the youthful stages is a 

character much n1ore fixed in the Gosport individuals 

than in those from the Lisbon. Upper Claiborne 

marine deposits are known at only a very few localities, 

and from none of them except in Alabama and possibly 

in northern Mexico have venericards been recovered. 

The implication carried in the tern1s upper and lower 

Claiborne is not fortunate, for certainly the lower Claiborne accounted for a much longer period of time than 

the upper Claiborne. In any case the upper Claiborne 

has not been recognized east of the Chattahoochee; 

and west of Alabama, in the presumably equivalent 

Yegua, the sediments seem to have been brought down 

by sluggish streams and deposited. in n1arshes and 

lagoons and estuaries. This type of sedimentation, 

though inconstant in detail, shows a remarkable uniformity in general character on each side of the Mississippi embayment and as far south as the Rio Grande 

embayment. Reef oysters (Ostrea alabamiensis) characterize the base of the Y egua toward the Mexican border, 

and on the Mexican side true marine conditions are 

recorded. 

JACKSON GROUP 

·In the eastern Gulf region the Jackson is given formational status; in the western Gulf region it is a group. 

The Jackson formation was named by Timothy Conrad 59 in 1856, hls determination being based on collections of shells made by Benjamin Leonard Covington 

Wailes at Jackson, Miss. Wailes described this deposit in 1854,60 referring even then to the obvious differences between the fauna of this locality and the collections from Vicksburg, Miss. 

Jackson, in Hinds County, Miss., is the type locality 

of the formation. Deposits of this age are exposed in 

AS Smith, E. A., Underground water resources of Alabama, pp. 18-19, 1907. 

sg Conrad, T. A., Observations on the Eocene deposit of Jackson, Miss., with 

descriptions of 34 new species of shells and cGrals: A cad. Nat. Sci. Philadelphia Proc., 

vol. 7, p. 257, 1856. 

6o Wailes, B. L. C., Agriculture and geology of Mississippi, 1st Rapt., p. 274, 1854. 

a wide band across the State from Clarke County to the 

east edge of the alluvium of the Mississippi Delta at 

Yazoo City. Its widest exposure is near Yazoo City 

on the west, and it is here that the deepest section may 

also be found, where a bluff face near the city exposes 

at least 180 feet of Jackson, overlain by about 100 feet 

of loess of a much later date. The deposits r,re probably even thicker at son1e localities in the vicinity. 

In Mississippi the formation has been divided by most 

authors into two members, the Moodys marl and the 

Yazoo clay; Lowe, 61 however, included a thiri, called 

the Madison sands, a preoccupied name later changed 

by Cooke 62 to Forest Hill sand. These beds are now 

referred to the Vicksburg. 

The lowest n1en1ber of the Jackson is the Moodys 

marl, lying with local unconformity on the Y egua 

formation of the Claiborne.63 It takes its name from 

Moodys Branch, a small creek flowing into the Pearl 

River at Jackson, Hinds County, from which \Valles' 

early collections were made. That pioneer of Mississippi geology said of the outcrop :

64 

This latter deposit is seen most advantageously in the bed of 

the creek emptying into Pearl River immediately below the 

crossing of the Jackson & Brandon Railroad. The bed lies 

about 15 feet below the level of the adjacent plain, and about 

4 feet of its thickness are exposed in the banks of the c-eek. Its 

entire depth has not been ascertained. 

The marl is of a bluish-green color in its moist state, and in 

the bed is of considerable toughness and tenacity. Upon exposure, and becoming thoroughly dried, it parts witl· much of 

its color, crumbles to a granular sandlike substance, anrl assumes 

a grayish appearance, owing to the large proportion of finely 

comminuted shell contained in it. 

The quantity of entire shells embedded in it is very great, 

lying almost in contact with each other, and forming perhaps 

one-sixth of the volume of the deposit. 

Later observers have given us accounts tl·at tally 

well with this first report of the outcrop. The locality 

has received the enthusiastic attention of all Tertiary 

paleontologists, as the specin1ens are usually in a nearly 

perfect state of preservation and are easily removed 

from the crumbling matrix. The Moodys n1arl also 

crops out near Shubuta, Clarke County, and at 

several points in Scott, Jasper, Smith, and Clarke 

Counties. 

At the base of the Yazoo clay, the upper member of 

the Jackson forn1ation in Mississippi, is a disco:-:ttinuous 

layer of indurated marl or impure limestone that has 

been called the "Zeuglodon beds",65 for it carrio,s many 

bones of Zeuglodon, a cetacean which serves 2 s one of 

&! Lowe, E. N., Mississippi, its geology, geography, soils, and mine:-al resources: 

Mississippi Geol. Survey Bull. 12, pp. 79, 82-84, 1915. 

&2 Cooke, C. W., Correlation of the deposits of Jackson and Vicks-burg ages iri 

Mississippi and Alabama: Washington Acad. Sci. Jour., vol. 8, pp. 18t'-198, 1918. 

63 Lowe has the order of the Jackson members reversed in the par<.~r just cited 

(Mississippi Geol. Survey Bull. 12), placing the Moodys Branch marl at the top of 

the Jackson instead of at the base, but the correct order was given by Cooke (op. cit., 

p. 188). 

u Wailes, B. L. C., op. cit., pp. 274-275. 

65 Scbuchert, Charles, U. S. Nat. Mus. Proc., vol. 23, p. 328, 1901. Lowe, E. N., 

op. cit., p. 79, 1915. 
• 

S'rRATIGRAPIIIC BACKGROUND OF THE VENERICARDlA PLANlCOSTA GROUP ib1 

the best guide fossils of the lower Yazoo clay in the 

Gulf States. 

The bulk of the Yazoo clay, as exposed at Yazoo 

City, consists of drab or yellowish calcareous clays, 

showing heavy bedding. The fossils are usually rather 

poorly preserved, and the molluscan fauna is not particularly rich. The upper n1ember is much thicker in 

western Mississippi than in the eastern part of the 

State, and in Alabama it thins rapidly and n1erges into 

the underlying member. 

Deposits of Jackson age extend across Alabama fron1 

Choctaw County to Georgia and Florida. They were 

formerly. united with the overlying Vicksburg group 

under the name "St. Stephens white limestone." The 

"white limestone" was first supposed to be Cretaceous; 

then it was transferred to the Eocene; and later Smith, 

Johnson, and Langdon, who first applied the name St. 

Stephens to it, recognized that it included deposits of 

Jackson and Vicksburg (Oligocene) ages. The name 

"St. Stephens limestone" was abandoned by the United 

States Geological Survey when Cooke 66 in 1918 divided 

it into several formations. West of the 88th meridian 

the Eocene part of the St. Stephens is called the 

Jackson formation; east of that meridian it is called 

the Ocala limestone. In November 1933 Cooke 67 

defined the Cocoa sand men1ber and correlated it with 

the lower part of the Yazoo clay. 

Dall 68 in 1892 correctly referred the Ocala to the 

Eocene but Dall 69 in 1903 and Matson and Clapp 70 

in 1909 placed the Ocala at the top of the Vicksburg, 

following Heilprin's earlier correlation.71 

The Ocala limestone rests conformably on the 

Gosport sand or is separated from it, according to 

Cooke/2 only by local unconformities. The white 

Marianna limestone of the Vicksburg group, which 

overlies it in western Florida, may be conformable with 

it, and there appears to be no sharp break between the 

Ocala and the Red Bluff clay, which overlies it in 

Alabama. However, the Zeuglodon remains, mnong 

the most reliable of the guide fossils of the Jackson in 

Mississippi, have been found in the Ocala limestone, 

and in 1915 Cooke 73 correlated the Ocala with the 

upper Jackson. 

There is a marked paucity of n1acrofossils in the 

Alabama Jackson, in sharp contrast with the extremely 

rich faunas of Mississippi. The Ocala is commonly 

66 Cooke, C. W., op. cit. 

67 Cooke, C. W., Definition of Cocoa sand member of Jackson formation: Am. 

Assoc. Petroleum Geologists Bull., vol. 17, pt. 2, pp. 1387, 1388, 1933. 

68 Dall, W. H., Correlation papers-Neocene: U. S. Geol. Survey Bull. 84, pp. 103, 

104, 1892. 

69 Dall, W. H., Contributions to the Tertiary fauua of Florida: Wagner Free Inst. 

Sci. Trans., vol. 3, pt. 6, pp. 1556-1558, 1903 . 

1o Matson, G. C., and Clapp, F. G., Preliminary report on the geology of Florida: 

Florida Geol. Survey 2d Ann. Rept., p. 51, 1909. 

71 Heilprin, Angelo, On the occurrence of nummulitic deposits in Florida and the 

association of Nummulites with a fresh-water fauna: Acad. Nat. Sci. Philadelphia 

Proc. for 1882, pp. 189-193, 1882. 

n Cooke, C. W., Alabama Geol. Survey Special Rept. 14, p. 275, 1926. 

:.!0412-39-2 

nonfossiliferous, and even where fossils other than 

echinoids and Pecten perplanus are present they are 

usually indicated by molds. 

In Florida the Jackson is represented by exten~ive 

outcrops of the Ocala limestone. The base of the formation has not been found in the State, but it is overlain with apparent conformity by the Vicksb1.trg, 

· except where the Oligocene deposits have been overlapped by Miocene or younger beds. The formation is 

fairly uniform in lithology, consisting for the most part 

of rather fine grained white limestone. 

The Jackson deposits in Georgia extend in a southwest-northeast band completely across the State f:"om 

the Florida and Alabama boundaries to the S<Juth 

Carolina line at Burke County. The greatest area of 

outcrop is in the southwestern part, where the Ocala is 

represented over a wide surface area; in the middle of 

the State the deposits are partly overlapped by the 

later Flint River forn1ation; and between the Ocmulgee 

River and the South Carolina State line the Oeala 

limestone is replaced by the Barnwell formation. 

The Ocala limestone, presumably contemporaneous 

with the Barnwell, was probably laid down in a region 

more abundantly supplied with calcareous material and 

farther from the eroding land surface. The transition 

between· the sands and muds of the Barnwell and the 

limestone of the Ocala is oscillatory, and the Ti,·rola 

tongue of Cooke and Shearer,74 a tongue of calcarr0us 

material extending far into the Barnwell area, probF.bly 

indicates an arm of the early Ocala sea in which calcareous deposition prevailed. 

Sloan 75 first named the Barnwell sand frmn the type 

locality in Barnwell County, South Carolina, and 

correlated it with the Claiborne group. StepheiJ son 

and Veatch 76 followed Sloan in referring the sane. to 

the Claiborne, and Cooke and Shearer 78 in 1918 included under the Barnwell the so-called tCongaree 

clay member of Veatch and Stephenson 79 and the 

Ostrea georgiana zone of their McBean formation. 80 

Cooke ·in 1925 proposed the present correlation of the 

Barn well sand with the Ocala limesto~e of western 

Georgia. The name tCongaree clay in Georgia was 

changed by Cooke and Shearer 81 to Twiggs clay m <)mber, because they found that the beds in Geo:rgia 

occupied a much higher stratigraphic position than 

73 Cooke, C. W., The age of the Ocala limestone: U.S. Geol. Survey Prof. Paper 

95, p. 108, 1915. 

74 Cooke, C. W., and Shearer, H. K., Deposits of Claiborne and Jackson a.ge in 

Georgia: U.S. Geol. Survey Prof. Paper 12Q-C, p. 53, 1918. 

75 Sloan, Earle, Handbook of South Carolina: South Carolina Dept. Agr., Com· 

merce, and Immigration, pp. 86, 90, 1907. 

76 Veatch, J. 0., and Stephenson, L. W., Preliminary report on the geology of the 

Coastal Plain of Georgia: Georgia Geol. Survey Bull. 26, p. 285, 1911; Underground 

waters of the Coastal Plain of Georgia: U.S. Geol. Survey Water-Supply Paper 341, 

p. 79, 1915. 

78 Cooke, C. W ., and Shearer, H. K., op. cit., p. 52. 

7D Veatch, J. 0., and Stephenson, L. W., Georgia Geol. Survey Bull. 26, p. 267, 

1911: U.S. Geol. Survey Water-Supply Paper 341, p. 77, 1915. 

so Stephenson, L. W., and Veatch, J. 0., op. cit. (Water-Supply Paper 341), p. 76. 

st Cooke, C. W., and Shearer, H. K., op. cit. (Prof. Paper 120-C), p. 52. 
158 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

Sloan's original tCongaree shales of South Carolina. 82 

This Twiggs clay n1en1ber is found at the base of the 

Barnwell and occupies a position near the landward 

margin of the for1nation. 

In South Carolina the Jackson is represented by 

the Barnwell formation in the south and west, and the 

Santee limestone and Cooper marl toward the north 

and east. The most recent work on this region is 

that by Cooke.83 

In North Carolina the upper Eocene is represented 

only by isolated outcrops of the Castle Hayne marl, 84 

the equivalent of the Santee marl of South Carolina 

and of the Ostrea georgiana zone of the Barnwell sand 

and the Tivola tongue of the Ocala limestone of 

Georgia. The molluscan fauna is known chiefly from 

molds, and these do not include determinable Venericardia planicosta. North of the Hatteras axis only 

the lower Eocene has been certainly recognized in the 

outcrop. 

At the head and on the west side of the Mississippi 

embayment, also, the beginning of Jackson sedimentation was heralded by an invasion of the sea covering 

lands that had been above the surface of the water 

since the end of the Midway. The gr~up is exposed 

along the base of Crowleys Ridge from Cross County 

to Phillips County in northeastern .Arkansas, resting 

upon earlier Eocene deposits and overlain with marked 

unconformity by the so-called Lafayette. In both 

northern and southern Arkansas it is a shallow-water 

marine series of clays and marly cross-bedded sands 

grading into lignitic days. The beds are fossiliferous, 

though not abundantly so, and leaf remains here and 

there bear witness to nearby vegetation. 

In the southern part of Arkansas the formation has 

been mapped from Jefferson to Ashley County, although 

the outcrops are interrupted by the tributaries of the 

Ouachita River. Many of the outcrops are highly 

fossiliferous, especially in the Crowleys Ridge region 

and in the vicinity of Rison, in Cleveland County, and 

Pine and White Bluffs, in Jefferson County. 

The earliest report on these beds that are known to 

be of Jackson' age is Owen's discussion 85 in 1860, in 

which at the end of the description of the section at 

White Bluff he made the statement that "The fossils 

found in the above section * * * belong to the 

Eocene Tertiary.'' 

Harris 86 in 1894 referred the White Bluff section to 

the Claibornian, following in this correlation the earlier 

12 Sloan, Earle, Catalogue of the mineral localities of South Carolina: Soutti Carolina Gaol. Survey, ser. 4, Bull. 2, p. 454, 1908; Handbook of South Carolina: South 

Carolina Dept. Agr., Commerce, and Immigration, p. 89, 1907. 

83 Cooke, C. W., Geology of the Coastal Plain of South Carolina: U. S. Gaol. 

Survey Bull. 867, 196 pp., 18 pis., 2 figs. 1936. 

84 Kellum, L. B., Paleontology and stratigraphy of the Castle Hayne and Trent 

marls in North Carolina: U. S. Gaol. Survey Prof. Paper 143, pp. 1-42, 11 pis., 1926. 

Si Owen, D. D., Second report of a geological reconnaissance of the middle and 

southern counties of Arkansas, p. 152, 1860. 

86 Harris, G. D., The Tertiary geology of southern Arkansas: Arkansas Gaol. 

Survey Ann. Rapt. for 1892, vol. 2, pp, 87-89, 1894. 

87 Heilprin, Angelo, The Tertiary geology of the eastern and southern United 

States: Acad. Nat. Sci. Philadelphia Jour., vol. 9, p. 151, 1884. 

determinations of Heilprin 87 and Call.88 Hcwever, in 

discussing the White Bluff fauna, 89 he . qualified his 

correlation by the observation that although "The 

general aspect of this fauna is indeed Claib<)rnian as 

was suggested by Heilprin and maintained n10re confidently by Call, yet the presence of such forms as 

Solarium bellastriatum, Mitra millingtoni, and Bullinella 

jacksonensis var., shows that the fauna is uppermost 

Claibornian or perhaps transitional between that and 

the Jackson." 

In 1902 Harris 90 definitely recognized the Jackson 

age of these deposits: 

At the time of writing my report on the Tertiary of Arkansas 

(1892), I felt strongly inclined to refer the fossiliferous bed~ at 

White Bluff on the Arkansas River to the Jackson; yet they had 

always been referred to the Claiborne, and there reemed not 

enough positive evidence in favor of the Jackson r.ffinities to 

entirely warrant the change. Since then some of the new or 

supposedly new species from White Bluff have bee:'1 found in 

abundance at Jackson, Miss., and at well-developed Jackson 

beds throughout Louisiana and east Texas. 

Later investigations of the Coastal Plain dBposits of 

Arkansas include those by Veatch 91 in 190~ and by 

Stephenson and Crider 92 in 1916. 

The Jackson formation in Louisiana exte"'l.ds from 

Wyants Bluff, on the Ouachita River, to tl'e Sabine 

River in Vernon Parish, on the Texas line, interrupted 

in Natchitoches Parish by the alluvium of the Red 

River. Conrad 93 first recognized the Eocene in Louisiana from a collection of Jackson fossils. He wrote: 

"We know of no locality west of this [Claiborne] in 

Alabama or Mississippi, of the Eocene, but on the 

Washita River it occurs near the town of Monroe." 

He also made, in a footnote to the reference cited above, 

a rather interesting reference to the Zeuglodon bones 

that are commonly found in these deposits: "Some 

Jarge saurian vertebrae from this place have been 

erroneously supposed to belong to the Eocer~ period. 

They doubtless occur only in the Cretaceous beds, as 

Judge Bry inforn1s us that Ammonites and other · 

Cretaceous fossils abound in the vicinity." This is 

especially interesting, as the characteristic Zeuglodon 

of the upper Jackson formation was described from 

this locality in the same year as the publi~ation of 

Conrad's comments.94 The Jackson deposits in the 

vicinity of the Ouachita River 95 and along th~ Sabine 

88 Call, R. E., Geology of Crowleys Ridge: Arkansas Gaol. Survey Ann. Rept. for 

1889, vol. 2, p. 3, 1891. 

89 Harris, G. D., op. cit., p. 93. 

90 Harris, G. D., Report on the geology of Louisiana, for 1902, pt. 1, The Tertiary 

geology of the Mississippi embayment, p. 22, Louisiana Gaol. Survey, 1902. 

91 Veatch, A. C., Geology and underground water resources of north1rn Louisiana 

and southern Arkansas: U.S. Gaol. Survey Prof. Paper 46, p. 39, 1906 

92 Stephenson, L. W., and Crider, A. F., Geology and ground water.• of northeastern Arkansas: U. S. Gaol. Survey Water-Supply Paper 399, pp. 79-81, 1916. 

93 Conrad, T. A., Observations on the Tertiary and more recent fcrmations of a 

portion of the Southern States: Acad. Nat. Sci. Philadelphia Jour., vol. 7, p. 120, 

1834. 

114 Harlan, Richard, Notice of fossil bones found in the Tertiary formation of the 

State of Louisiana: Am. Philos. Soc. Trans., new ser., vol. 4, pp. 397-403, 1834. 

96 Veatch, A. C., Notes on the geology along the Ouachita: Louisiana Gaol. Survey 

Rapt. for 1902, no. 4, p. 164, 1902. 
\ 

STRATIGRAPHIC BACKGROUND OF THE VENERICARDIA PLANICOSTA GROUP 159 

River at the Texas State line 96 were described by 

Veatch in 1902. He stated then that beds of Jackson 

age had but recently been discovered in Texas. 

The Jackson group is exposed intermittently from 

the Sabine River at the Louisiana-Texas State line to 

the Rio Grande in Starr County, Tex. The upper 

Eocene in Texas has been comn1only known under the 

name Fayette sandstone, a name proposed by Penrose 97 

in 1890 from a locality in Fayette County. .He included 

in this division deposits that range in age from Claiborne to Miocene. Dumble 98 in 1892 divided the 

Fayette of Penrose into two forn1ations, calling the 

lower one the Y egua and the upper one the Fayette. 

In 1903 99 he separated from the Fayette the Oakville 

sandstone and the clay that inm1ediately underlies it. 

Trowbridge 1 in 1923 used Fayette as defined by 

Dumble, and he was followed in this usage by Deussen 2 

and Bailey.3 Later, however, Dun1ble 4 again divided 

the Fayette into two units, the lower of whieh he said 

was the "true Fayette" and eorrelated it with the 

Claiborne group. The upper division he ealled the 

"Whitsett", and this was correlated by Trowbridge,5 at 

least in part, with the Frio clay. The Frio clay, 

originally described by Dumble 6 as upper Eocene but 

later correlated with the Claiborne group/ ineluded 

higher beds of Catahoula age. Deussen 8 correlated 

these deposits at least tentatively with the Jackson 

formation, and Trowbridge 9 also tentatively with the 

Oligocene, and so it stands on the reconnaissance map 

of Texas (March 1Q34). Berry 10 recorded the flora 

and discussed the general stratigraphy in 1924. Plummer 11 made a threefold division-Whitsett, McElroy, 

and Caddell -in eastern Texas, and a twofold division-

!hitsett and Lipan--in central and southern Texas. 

J¥1-iss Ellisor 12 regarded the Whitsett, McElroy, and 

!vs Veatch, A. C., The geography and geology of the Sabine River: Idem, p. 131. 

t7 Penrose, R. A. F., Jr., A preliminary report on the geology of the Gulf Tertiary 

of Texas from Red River to the Rio Grande: Texas Geol. Survey 1st Ann. Rept., pp. 

47-58, 1890. 

:•a Dumble, E. T ., Report on the brown coaland lignite of Texas, pp. 148-157, Texas 

G;eol. Survey, 1892. 

:" Dumble, E. T., Geology of southwestern Texas: Am. Inst. Min. Eng. Trans., 

vol. 33, pp. 953-957, 1903. 

1 Trowbridge, A. C., A geologic reconnaissance in the Gulf Coastal Plain of Texas 

nllar the Rio Grande: U. S. Geol. Survey. Prof. Paper 131, p. 97, 1923. 

I Deussen, Alexander, Geology 'of the Coastal Plain of Texas west of Brazos River: U:. S. Geol. Survey Prof. Paper 126, p. 80, 1924. 

a Bailey, T. L., The Gueydan, a new middle Tertiary formation from the southwestern Coastal Plain of Texas: Texas Univ. Bull. 2645, p. 38, 1926. 

'Dumble, E. T., A revision· of the Texas Tertiary section with special reference to 

the oil-well geology of the coast region: Am. Assoc. Petroleum Geologists Bull., vol. 

8; pp. 431-434, 1924. 

16 Trowbridge, A. C., Tertiary and Quaternary geology of the lower Rio Grande 

r~gion, Texas: U. S. Geol. Survey Bull. 837, pp. 141-142, 1932. 

j• Dumble, E. T., The Cenozoic deposits of Texas: Jour. Geology, vol. 2, pp. 554-

5$5, 1894. 

,7 Dumble, E. T., Geology of southwestern Texas: Am. lust. Min. Eng. Trans., 

vol. 33, pp. 953-956, 1903. 

s Deussen, Alexander, op. cit. (Prof. Paper 126), p. 92. 

• Trowbridge, A. C., op. cit. (Bull. 837), pp. 156-157. 

10 Berry, E. W., The middle and upper Eocene floras of southeastern North .America: U.S. Geol. Survey Prof. Paper 92, 1924. 

u Plummer, F. B., Geology of Texas, vol. 1, Stratigraphy, pt. 3, Cenozoic systems 

in Texas: Texas Univ. Bull. 3232, p. 685, 1933. 

, u Ellisor, A. C., Jackson group of formations in Texas, with notes on Frio and 

Viicksburg: Am. Assoc. Petroleum Geologists Bull., vol. 17, no. 11, p. 1298, November 

u}a3. 

Caddell as formations and carried them across the 

State. Each of the units was subdivided for the ID<)st 

part on micropaleontologic evidence. The marine 

macrofaunas are local in their distribution in Texas 

and are. limited to the embayments of the Sabine River 

and the Rio Grande. 

Three species of the Venericardia planicosta stock 

have been found in deposits of Jackson age in the Mississippi and Rio Grande embayments, V. apodensata, 

n. sp., V. klimacodes, n. sp., and V. cookei, n. sp. 0"'ly 

one of these, however, V. apodensata, is at all cosmopolitan in its distribution. This species is found in 

deposits of low.er Jackson age, the Moodys marl member, in Mississippi, and it is abundantly representec1 in 

the western embayment in Arkansas and Louisiana. 

It has been recorded from a few outcrops in Alaba1na, 

but it is unknown north and east of the Tombigl:>ee 

River. V. apodensata is an obvious descendant of 

V. densata Conrad of the Claiborne, but it differs fron1 

that species in its more rounded outline, lighter shell 

structure, much lower hinge plate with shorter and ID<)re 

arcuate teeth, and lower umbones. The shell is sn1all 

and compact, as in the Claiborne form, and the umbonal 

ribs are serrate and slightly terraced. The statemo,nt 

has frequently been made that the average rib count of 

the venericards increases from the Midway to the Jackson. In our counts, which included about 1,500 vah,.es, 

the Tuscahoma counts center about 29; the Bashi, 29 

and 30; the Lisbon, 26 and 27; the Gosport, 29; and the 

Jackson, 31 and 32. The rib count of the Moody~ marl 

species runs higher by one or two than that of the succeeding Yazoo clay species. Apparently within a certain stock the rib count tends to be higher with a rise in 

· the section, and the relatively low rib count of the Lisbon 1s due to the abundance of the aberrant densata. 

In the upper Jackson of Mississippi, the Ya.zoo clay 

men1ber, V. apodensata is replaced by Y. Himacodes, a 

more trigonal forn1 with a smaller hinge plate, more 

sharply incised intercostals, and more distinct lateral 

terracing, extending over a greater area. This forrn is 

. found only in Mississippi in the upper beds in the 

vicinity of Yazoo City. In Alabama, in the vicinity 

of the Conecuh River, the third species, V. cookei, is 

found, restricted apparently to the sandy depo"'its 

underlying the Ocala limestone. This forn1 appears 

to be the culmination of the V. pilsbryi stock of the 

Wilcox that was represented in the Claiborne by 

V. angustoscrobts, from which it differs in its rr0re 

posteriorly produced ventral margin, more numerous 

costae, and the different shape of the median cardinal 

tooth. 

There is a new, rather small and well-characterized 

species of Venericardia in the Jackson of Robinsons 

Ferry. It is also well represented in northern Polk 

County, but for most of the species of the lower and 

middle Eocene of Alabama the Sabine River is the 

western outpost. 
160 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

In the Ocala limestone of eastern Alabama, Florida, 

Georgia, and the contemporaneous deposits of the 

Carolinas no venericards are found. The Ocala was 

possibly laid down in waters too deep for inshore 

faunas, as only echinoids, pectens, and similar forn1s of 

less shallow water have been recovered fron1 these 

sediments. 

The Venericardia planicosta stock ends with the 

Jackson. The rise, en1inence, and decline of an organic 

gr6up, whether it be the titanotheres, the ancient 

Greeks and Mayans, or Venericardia planicosta, seein 

to be so governed that, with an independence of physical conditions that is not understood, they run their 

course as individuals do and are finished. The pl(lniJACKSON 

UPPER CLAIBORNE 

LOWER 

CLAIBORNE 

UPPER 

WILCOX 

LOWER WILCOX 

UPPER MIDWAY 

LOWER MIDWAY 

FIGURE 27. -Distribution of species of the l'"enericardia planicosta group in the Eocene 

of the Gulf embayment and eastern Atlantic slope. 

costa group survived during early and mid-Eocene time 

under conditions apparently almost as severe as those 

which befell them toward the end of the Eocene. 

Between the end of Wilcox tin1e and the beginning of 

Claiborne time there was a widespread restriction of 

marine life, but with the advance of the Lisbon sea the 

venericards of the planicosta group returned to their 

former position of pron1inence in the molluscan faunas. 

The retreat of the n1iddle Claiborne sea covered perhaps 

a wider front than that which took place at the end of 

Wilcox time. In any case, the venericards did not 

regain their former position with the advance of the 

late Claiborne and Jackson seas, and their approaching 

decline and extinction was foreshadowed in tl'e decrease 

in the number of individuals and species. The life 

cycle was the same for Eurasian representatives of the 

genus as it was for the An1erican planicostas and might 

1nore readily be explained by diastrophic movements, 

for at the end of the Eocene epoch the European 

marine faunas were withdrawn farther and for a longer 

period than those of the American waters. The relative abundance of the species of the planicosta group in 

the successive stages of the Eocene is in~icated in 

figure 27. 

WORLD DISTRIBUTION OF EARLY EOCENE SPECIES 

COMPARABLE TO VENERICARDIA PLANIC·'lSTA 13 

On the assumption that a con1n1on origin for the 

men1bers of the Fe·nericardia plan·icosta group is less 

difficult to accept than the 1nultiple origin of a group 

so specialized, we may speculate,· possibly with more 

interest than profit, upon the focus of di';'tribution. 

Because of the "abundance in varieties, individuals, 

and their wide distribution in America" Dall u was 

"persuaded that America is the center from which the 

group has been distributed." Such a postulate is also 

strengthened by the abrupt development of the group 

during the early Eocene upon the An1erican Ehores, and 

by the absence of any recorded abundance in the 

European deposits until the medial Eocene. However, 

there are too many unknown factors to r.rgue convincingly for any given source, and no theory is ade-: 

quately supported by the known facts. 

The present records of the lower Paleoce"'le nlollusean faunas are exceedingly few, scattered, and fragn1entary. (See pl. 31.) An attempt is here made to include 

all those that are relevant and significant. Venericards which frmn the printed descriptions r.nd figures 

seem to be allied with the pla.nicosta group are registered 

fron1 a few widely separated outcrops. 

1. 1v1iss Maury 15 has recorded fron1 bed 2 of the supposed 1-fidway in the Soldado Rock, off the southwest 

corner of Trinidad, in La Boca de la Sierpe, a Venericardia planicosta which from the figure ahne seen1s 

very closely related to ouF Gulf mediaplata. There 

are other allied shells, both bivalve and univalve, and 

the ensemble of the Soldado fauna suggests a relationship to the Midway faunas of the Gulf similar to that 

existing between the Gulf and Trinidad faunas today. 

Other outcrops were later discovered on Trinidad by 

Waring 16 and were included by him under the Marac 

formation. Their contained faunas were di~cussed by 

ta The excellent paper of R. Rutsch upon "Die stratigraphische Bedeutung der 

v'enericardia planicosta und ihrer Verwandten" (Eclogae geologicae Helvetiae, vol. 

29, no. 1, pp. 151-186, June 1936) was received after this paper had befln submitted for 

publication. 

uDall, W. H., Contributions to the Tertiary fauna of Florida: Wagner Free lnst. 

Sci. Trans., vol. 3, pt. 6, pp. 1418, 1419, 1903. 

ts Maury, C. J., A contribution to the paleontology of Trinidad: Acad. Nat. Sci. 

Philadelphia Jour., 2d ser., vol. 15, p. 51, pl. 8, figs. 15, 16, 1912. 

16 Waring, G. A., The geology of the Island of Trinidad, B. W. I.: Johns Hopkins 

Univ. Studies in Geology, no. 7, pp. 40, 41, 1926. 
DISTRIBUTION OF EOCENE SPECIES COMPARABLE TO VENERICARDIA PLANICOSTA 161 

Harris. 17 A small planicostate species with a few low 

ribs, evanescent toward the ventral margin, resembles 

Venericardia diga of the Me:xican faunas and V. potapacoensis of the Maryland and Virginia Nanjemoy. 

The hinge, however, which is one of the best characters 

of the Mexican and Maryland forn1s, is not figured, 

and it is quite possible that the resemblance is by no 

rneans so close as the single figured exterior might 

suggest. The Trinidad form is associated with a 

venericard suggesting V. hesperia, with Calyptraphorus 

cf. C. velatus, and with Hercoglossa, all species of pronounced Midway affinities. The horizon has been 

reported in Toas, on the mainland in Venezuela, but 

the report is not confirmed iu the few and inadequate 

collections accessible to us. As 1-1iss Maury observed, 

never before its discovery off Trinidad had Yenericardia 

planicosta been found so close to the Equator. 

2. Venericardia duponti, described by Cossmann 18 

from the type locality of the Montian of Belgium, is 

without question a member of the planicosta group. 

In outline and general aspect it most closely suggests 

Y. mediaplata. Cossn1ann in his thoroughly adequate 

description remarks that at first sight one might think 

it nothing more than an ancestral mutation of Venericardia planicosta, and a close comparison might be 

made even more truly to Fenericardia media-plata. 

Fortuitous or not, the relatively low rib count and the 

low, broad hinge plate are characteristic, though not 

universally present, in the early Eocene venericards 

both of Belgium and of the Gulf. The occurrence of a 

species of this character in the 11ontian has a broad 

significance, for the Montian fauna is generally accepted 

as one of the parent faunas of the Lutetian of the Paris 

Basin. One may more readily assume that these two 

early Eocene venericards can1e from a con1n1on fatherland and that Yenericardia planicosta of the Paris 

Basin developed in place from the duponti stock than 

that the mid-Eocene European form arose frorn a 

lower Eocene n1id-American parentage. However, it 

is only fair to remember in this connection the Trechmann .record 19 that the Tethyan sea apparently 

reached Jamaica and that certain elements in the 

Gulf faunas may have returned by the same route by 

which the large Tethyan lucinoids and cerites, Carolia 

and Gisortia, arriYed. 

3. On some of the later paleogeographic maps the 

North Sea-Baltic Paleocene gulf is extended across 

northern Europe to the lower Volga. The direction of 

such an embayment has, incidentally, a much stronger 

east-west component when viewed on a globe than it 

does on most of the flat projections, and is based upon 

t 7 Harris, G. D., Notes on the paleontology, in Waring, The geology of the Island 

of Trinidad, B. W. I.: Johns Hopkins Univ. Studies in Geology, no. 7, pp. 99, 100, 

1926. 

18 Cossmann, Maurice, P~ll'cypodes du Montien de Belgique: Mus. royale histoire 

nat. Belgique M~m., vol. 5, p. 52, pl. 5, figs. 12-17; pl. 6, figs. 1-3, 1908. 

u Trechmann, C. T., Yellow limestone of Jamaica and its Mollusca: Geol. Mag., 

vol. 60, no. 710, pp. 337-367,1923. 

very meager records of a northern fauna not quite as 

old as the Montian. One ecologic phase of this fauna 

is best recorded in the excavations made for the ~f:ts 

works at Copenhagen. 20 In it the gastropods, particularly the smaller gastropods, are dominant, and the 

turrids are conspicuously abundant in species. There 

are very few of the larger bivalves and no venericards. 

A similar early Eocene fauna is also recorded at Klagshamm, in southen1 Sweden/1 and in Swedish and nm·th 

German erratics and wells, but in. erratics from Ysted, 

Skania, larger Turritellas of the T. mortoni and T. 

humerosa types are particularly common. The most 

remarkable fauna, not only intrinsically but also because 

of its extraordinary likeness, considering the distance 

involved, to our own Gulf faunas, is that from the 

Paleocene of the lower Volga. 22 Four horizons hz.ve 

been recognized at which Volutocorbis, Levijusus, 

several familiar Turritellas, and Enclimatoceras hr.ve 

been found. Three species of simple-ribbed venerica:rds 

are included, and among them Cardita longa, from the 

upper Syzranian, invites the closest comparison. In 

none of the South Russian venericards, however, is the 

individual resemblance to the Gulf venericards so 

strong as that of V. duponti of the Montian to V. 

mediaplata, although the general set-up and balance of 

the Volga and Gulf faunas is as close if not closer. 

There may also have been a transgression of the nor~hern sea over the low lands of northen1 Siberia, but the 

records of that area are very imperfectly known. T'1e 

major transgression, which united the Arctic and t-he 

Mediterranean seas through the broad Turgai Straits 

and made an archipelago pf the IGrghiz Steppes, ~~as 

an event of middle or late Eocene time. The fauna of 

the Thanet sands of the old Thames Valley is a dmninantly bivalve fauna resembling in the abundance of a 

few species that of the Aquia formation of Maryland 

and Virginia, but there are no venericards included in 

the collections from the Thanet sands that have b£'~n 

available for study. The Paleocene of Limbour::r,23 

which is also a little younger than the Montian, carries 

Cucullaea, Ostrea, and a few lucinoids, but the faunr. is 

for the most part one of brackish waters. The greater 

part of western Europe was drained before the beginning of the Tertiary period. There are a very few 

fragmentary Paleocene records in the Paris Basin, m0st 

of them in fresh- or brackish-water deposits. 

4. At some time during the early Eocene, probably 

the Thanetian, the boreal sea penetrated as far south 

zo Von Koenen, A., Uber eine Paleocane Fauna von Kopenhagen: K. G'1sel1. 

Wiss. Gottingen Abh., vol. 32, pp. 3-128, pis. 1-5, 1885. 

21 Holst, N. 0., and Gronwall, K. A., Paleocen vid Klagshamm: Sveriges geol. 

undersoknings Skrifter, ser. C, no. 208, pp. 1-27, 1907. 

22 Archangelsky, A. D., D~p6ts pal~ocenes de la r~gion volgienne du gouverner1ent 

de Saratov et leur faune: Materialien zur Geologie Russlands, vol. 32, pp. l-207, 

12 pis., 1904. Netschaew, A. V., Die Fauna der Eoc!inablagerungen an der V\·olga 

unterhalb Saratow: Trudui Obschestva Kazan, vol. 32, pt. 1, pp. 1-247, pis. 1-10, 

1897. 

23 Vincent, Emile, Mollusques des couches a Cyrenes (Pal~ocene du Limbo·1rg): 

Mus. royale histoire nat. ]\Iem. 43, 43 pp., 7 fossil pis., portrait of Emile Vincent and 

his bibliography, 1930. 
162 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

as Kressenberg 24 in Bavaria, and left in the coarse 

glauconitic sands at the base of the Kressenberg section 

the remains of a rich boreal fauna, which, however, was 

soon replaced by one in which Gisortia, one of the 

characteristic elements in the old Tethyan fauna, 

became increasingly abundant. The shores of the old 

Tethyan sea are not sharply defined. There was 

probably communication between the Mediterranean 

and the Atlantic, and the French Pyrenees were 

apparently engulfed from the late Cretaceous into the 

Paleocene. Probably later in the Eocene the Adriatic 

was extended northward across Italy and eastward to 

the Vienna Basin. The Pyrenean Gulf opened in the 

direction of the Bay of Biscay. The assemblage of 

fossil forms is distinct from any recovered to the north, 

and in the sequence of fossiliferous deposits with no 

perceptible break the lower beds carry rudistids suggesting the Maestrichtian and the upper beds yield 

Paleocene Foraminifera. Venericards or carditas are 

con1mon, and several species have been separated, but 

they are known from molds only, and none of thmn are 

strikingly suggestive of planicostate forn1s. As in the 

l{ressenberg series, the lower Paleocene fauna is more 

closely allied with that of the Montian, and the Foraminifera of the uppermost bed are more clo~ely 

associated with the Tethyan fauna. A border-line 

deposit has also been recorded from the Vienna Basin, 

but for the most part the Upper Cretaceous and 

Paleocene of southern Europe is, macrofaunally, a lost 

interval. Cox 25 emphasized our ignorance of this 

area, for we have no wa.y of knowing the extent to 

which the compressional folding in the Alpine synclinorium and all the attendant earth movements affected 

the physiography of the Euro-African Continent. 

5. The Tethyan sea, extending eastward as far as 

the Cathaysia of Grabau, 26 the old land mass which 

united the East Indies with Malaysia and isolated the 

Pacific, filled the Atlas syncline and washed unknown 

shores possibly far to the west of the African coast. 

India was almost cut off by a sea which occupied the 

Himalayan synclinorium through late Cretaceous and 

early Eocene time and in which was laid down our 

finest record of a little-known interval-a record, however, which is not relevant to the present discussion, for 

no venericards of the planicosta group are included in it. 

The eastern Tethyan shores were for some reason inhospitable to the group, for neither are members of 

this group included in the remnants of early Eocene 

faunas nor are they foreshadowed in the late Cretaceous, which is uncommonly well represented in the area. 

The shores of the Tethyan sea have not been defined. 

21 Schlosser, Max, Die Eocaenfaunen der bayerischen Alpen: Bayer. Akad. Wiss. 

Abh., Math.-naturwiss. Abt., Band 30, Abh. 7, 1. Teil, Die Fauna des Unter- und 

Mitteleocaen, 207 pp., pis. 1-6; 2. Teil, Die Obereocaenfauna, 68 pp., pis. 7, 8, 1925. 

25 Cox, L. R., The Mollusca of the Hangu shales: India Geol. Survey Mem., 

Palaeontologia Indica. new ser., vol.. 15, pt. 8, pp. 136, 137, 1930. 

2

6 Grabau, A. W., Summary of the Cenozoic and Psychozoic deposits with special 

reference to Asia: Geol. Soc. China Bull., vol. 6, pp. 151-264, 1927. 

The Eocene section has been recognized but not adequately studied and interpreted in Persia/7 Arabia, and 

Palestine. The upper part at least of the Paleocene is 

developed in Eg-:rpt, and later developments include 

the nummulitic limestone of which the Py-ramids are 

built. The late Cretaceous is exceptionally well developed in the Libyan Desert 28 but altl''lugh the 

lithology remains similar there is apparently a time 

break at the base of the Eocene section. The lower 

Eocene is also responsibly reported from both the 

eastern 29 and western 30 coasts of Africa south of the 

Equator and along the Guinea coast from Cameroon to 

Senegal. That these marine deposits are something 

more than a wash along the old African shore lines is 

indicated by the Nigerian deposits, in which the deepwater sediments lie to the north and their landward 

extensions toward the south. Oardita-like forms with 

tripartite ribs, the dose descendants, perchance, of 

Oardita beaumont·i, are widely seattered through the 

north African deposits, but unhappily there are no 

reeorded African descendants of the smooth and simpleribbed Oardita baronetti of the Tunisian Up:'Jer Cretaceous or of the possibly identieal form, Oardita libyca 

Zittel. A genetic relationship to Gardit.a duponti of the 

Montian is suggested, although the Montian gulf was 

probably not in direct communication with the Tethyan 

sea, and none of the characteristic Tethyan univalves 

are recorded in the Montian fauna. 

6. The Paleocene of the Pacific is so little l~nown and 

its few representatives are separated by so vast expanses of sea or land or both that an attem])t to focus 

speculations as to its history would be futile. All the 

recognized fossiliferous marine sections of Japan are 

now considered later than Paleocene, and the most 

recent work of Nagao 31 indicates that even the marine 

27 De Morgan, J ., Mission scientifique en Perse, vol. 3, pts. 2 and 4, 1904. DouvilM 

H., in DeMorgan, J., Mission scientifique en Perse, vol. 3, Etudes goologiques, It. 

4, Paleontologie Mollusques fossiles. pt. 2, pp. 191-380, pis. 25-50, 1£':'4. 

2s Quaas, A., Die Fauna der Overwegischichten und der Blattertl one in der liby· 

schen Wiiste, in Beitrag zur Kenntniss der Fauna der obersten Kreidebildungen in 

der libyschen Wiiste: Palaeontographica, vol. 30, pt. 2, 4th. sec., pp. 153-334, plf. 

20-33, correlation tables. 1902. 

2u Schlosser, Max, Uber Tertiar und obere Kreide aus Portugiesisch-Ostafrika: 

Bayer. Akad. Wiss. Abh., Math-naturwiss. Abt., Band 32, Abh. 2, pp. 1-25, pis. 

1-3, bibliography, 1928. 

ao Bohm, J., Eo1:ane und miozane Versteinerungen aus Angola: Deutsche geol. 

Gesell. Zeitschr., Band 81, p. 450, 1929. Douvill~. H., La limite en';re le Ort\taoo et 

l'E'>Cime en Aquitaine, aux Indes et au Soudan:·Acad. sci. Paris Comptes rendus, 

vo1. 170, pp. 154-159, 1920; Douville, H., L'Eocene au Soudan et at' Senegal: Com. 

etudes hist. et sci. Afrique occidentale fran~aise Bull. 2, pp. 113-17L pis. 1-5, 2 text 

mapq, correlation table, 13 text figures of fossils, 1920. Newton, R. I' , On the lower 

Tertiary Mollusca of the Fayum province of Egypt [presidential ad~ress]: Malaool. 

Soc. London Proc., vol. 10, pp. 56-89, pis. 3, 4, 1912; Eocene Mollus,~a from Nigeria: 

Nigeria Geol. Survey Bull. 3, 1922. Oppenheim, Paul, Zur Kenntnis alttertiarer 

Faunen in Agypten: Palaeontographica, Band 30, Abt. 3, Lief. 1, Der Bivalven, 

erster Teil (Monomyaria, Heteromyaria, und Siphonida intergripalliata), pp.1-164, pis. 

1-17, 1903; Idem, Lief. 2, Der Bivalven, zweiter Teil, Gastropoda., Cephalopoda, 

pp. 165-348, pis. 18-27, 1906; Die eocil.ne Invertebraten-Fauna des Kalksteins in Togo: 

Beitr. geol. Erforsch. deutschen Schutzgebiete, Heft 12, 126 pp., 5 pl•, bibliographic 

footnotes, 19Hi. Pervinquiere, Leon, Etudes de pal~ontologie tunisienne, vol. 2, 

p. 241, pl. 18, figs. 1-3, Direction g~n. travaux publics, 1912. Vincent, Emile, 

La faune paleocene de Landana: Mus. Congo beige Annales de geologie, ser. 3, vol. 1, 

fasc. 1, pis. 1-10, pp. 1-92, 1913. 

a1 Nagao, Takumi, Palaeogene coal-bearing formations of the island of Kyilshfi: 

Tohoku Imp. Univ. Sci. Repts., 2d ser., Geology, vol. 11, no. 1, pp. 1-21, 1 text map, 1 

correlation table, Sendai, Japan, 1927. 
HINGE INVERSION IN PELECYPODS 163 

lenses in the Miike coal field are probably of Lutetian 

age. The old Cathaysia apparently extended eastward 

beyond the present coast line of Japan. Along some 

unknown shore, however, the group perhaps pushed 

southward and left a seemingly authentic record in the 

Wangaloa beds in Canterbury and Otago, on the south 

island of New Zealand,32 the farthest outpost in the 

Southern Hemisphere. A large venerica,rd was determined by Marshall as lTenericardia patagonica Sowerby, 

and although the specific identity is highly improbable, 

the possible occurrence of the group in the Antipodes 

is significant. lTenericardia patagonica Sowerby, with 

which the Wangaloa species was identified, was described by G. B. Sowerby from material recovered by 

Darwin on the voyage of the Beagle. The locality is 

the gravel-capped cliff at the mouth of the Santa Cruz 

River, Patagonia, the type locality of the Santa Cruz 

beds, a formation now referred to the upper Miocene. 

The hinge of the W angaloan-species is not figured, and 

no specimens are included in the collections available 

for study. 

7. The one sure early Eocene venericard in the 

Pacific fauna is lTenericardia ~,enturensis Waring,33 from 

the Martinez formation at the base of the Eocene section in north-central California. The route by which 

it arrived is not known, but in the light of our present 

information a temporary entrance from the mid-Atlantic 

seems more plausible than a migration along Pacific 

shores either northward through the length of South 

America or along the north Asiatic and Alaskan shores 

southward, areas in which no record has yet been discovered. The resemblance, furthermore, between the 

Midway Venericardia mediaplata of Wilcox County, 

Ala., and the probably synchronous Martinez lTenericardia venturensis Waring is surprisingly close. It is 

interesting if not relevant in this connection to recall 

the remarkable similarity between the middle Eocene 

fauna from the Simi Valley, in southern C~lifornia, 

and a small fauna collected several years ago on the 

Isthmus of Tehuantepec, less than 10 miles behind the 

mountain front facing the Gulf of Mexico. We do not 

know that there was an intermingling of the Atlantic 

and Pacific faunas at that time, but we do know that 

the barrier separating them must have been exceedingly 

narrow. If those conditions existed during the middle 

Eocene, it is possible that they prevailed during son1e 

short part of the late Cretaceous or in the invasion that 

heralded the Tertiary. At such a time a few species 

by reason of some unusual adaptability in either the 

larval or the adult stages may have been able to establish 

themselves on the Pacific coast. 

Although widely scattered and not clearly related 

occurrences do not indicate the focus of distribution, 

32 Marshall, P., The Wangaloa beds: New Zealand Inst. Trans. and Proc. for 1916, 

vol. 49, pp. 4ro-460, pis. 34-37, 1917. 

33 Waring, C. A., Stratigraphic and faunal relations of the Martinez to the Chico 

and Tejon of southern California: California Ar.ad. Sci. Proc .. ser. 4, vol. 7, no. 4, 

p. 80, pl. 11, figs. 6-9, 1917. 

they tend to push it backward in geologic time. S•1ch 

a group may be reasonably supposed to have its roots 

deeper in the past than one in which the developrn.ent 

is localized. Although the representation of the 

l'enericardia planicosta group on the Gulf and nlidAtlantic shores is the most extensive among the recorded faunas, the occurrence of members of the group 

in European, possibly Antipodean, and certa.jnly 

west coast American faunas of possibly syncbron"lus 

age renders highly improbable the evolution of the 

entire group in mid-American waters during the per;od 

i1nmediately preceding the Tertiary. 

HINGE INVERSION IN PELECYPODS 

In his study of a long series of venerica.rds the junior 

author noted one left valve of lTenericardia bashiplata 

in which the hinge dentition is the 1nirror image of that 

of the normal right valve. This specimen was collected 

from the headwaters of Beaver Creek, Clarke County, 

Ala. · 

In this abnormal lTenericardw {pl. 34, fig. 4) several 

points are of. interest. The hinge armature incluies 

three cardinal teeth radiating from the tip of the un1bo 

to the margin of a hinge plate which is not symmetrical 

but obliquely produced behind the umbo, thus offering 

a more effective support for the ligament. The anterior 

of the three cardinals has, unfortunately, been worn 

down, probably upon the old Bashi beach. The middle· 

cardinal is very heavy and deltoid. This, too, is worn 

toward the beaks, but a reconstruction can be made 

with assurance. The posterior cardinal is laminar rnd 

extends from the tip of the umbo to the ventral mar-sin 

of the hinge plate. The dorsal portion of this left val-rre; 

the ligament, and the hinge plate and teeth are norn1al 

for the right; it is a fair inference that the missing right 

valve must have exhibited the normal left dentithn, 

for otherwise thP hinge teeth could not have function~d. 

The muscle impressions, the pallial line, and the lateral 

and ventral margins are norn1al for the left valve. It 

is again a fair inference that the orientation of the Eoft 

pa.rts must have been normal. The ollly suggestiou of 

an anatomical anon1aly is in the pedal scar, which, 

though occupying its normal position between the 

lunule and the anterior retractor, is abnormally long 

and slightly more dorsal and more marginal. ~he 

·differences are not sufficiently great, however, to occasion published comment were it not for the remarkable 

dentition. The rather considerable thickening of the 

shell over the area of the adherent mantle indica-tes 

that the shell reached full maturity and probably old 

age. It has attained a height of 80 millimeters and an 

almost equal breadth and offers no indication of an 

unusually severe or unsuccesc;;ful struggle for existence. 

Sinistral shells are not uncommon an1ong the gastropods. Certain genera, such as the con1n10n fresh-water 

Physa, are eharacteristically sinistral; normally dextral 

genera, such as Fulg-u.r of the east coast and Gulf Ter-
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164 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

tiary and Recent, include sinistral species-for example, species from the Eocene of the Paris Basin, the large 

Fulgur perversum-and pathologic sinistral individuals deltoid cardinal is usually in the left valve. In this 

like the sacred Chank shells of India have been recog- group, however, the anterior end of the shell is produced 

nized in a large number of species and genera among and there are still vestiges of an anterior cardinal, 

the univalves. In the Chanks, which have been rather which is obsolete in the later Goodallia. Tho, relative 

fully recorded because of their ethnographic interest, position and prominence of the cardinals se~m much 

the estimated proportion of sinistral to dextral shells less stable than in the other astartids, and it is hard to 

is 1 to 6,000,000. be sure whether the irregularities are of the same 

Abnormalities in pelecypods have been much more nature as those occurring in groups in which the dentirarely observed, and their records are confined to rela- tion has not yet been fully adjusted and established or 

tively few groups. However, as Popenoe and Findlay 34 whether the A1,icrosta.gon hinge offers a true "inversion" 

suggest (p. 312): "Inverse coiling in gastropods involves of the cardinal teeth. Hanna 40 noted and adequately 

the whole shell and hence is usually at once apparent. figured "a very interesting pair of valves belonging to 

On the other hand, a transposed lamellibranch hinge the low-beak variety of l7enericardia hornii. * * * 

is seldom readily apparent, even in wel1-preserved The hinge characters of the right valve are found in the 

specimens, and is to be found only by careful search." left and vice versa." The only published rrcords we 

They prove their point by finding "transposed" hinges have noted of transposition in the east coast and Gulf 

among the normal in a ratio of 1 to 180 in the veneri- Fenericardia are those by Popenoe and Findlay, 41 who 

~ards and 1 to 130 among the astartids. Short papers observed an apparent inversion in the cardinals and 

by 1\1orley-Davies 35 and that by Popenoe and Findlay anterior laterals of 6 right and 2 left valves of V"enericover the most that has been published on the abnor- cardia parva Lea fron1' the Claiborne sand, in 2 left 

malities of the bivalve hinge. The hinges cited oceur valves of Venericardia granulata from the Pliocene of 

for the most part in the fresh-water groups, in the more North Carolina, and also in 7 right and 2 left valves of 

primitive of the Teleodesn1acea, the astartids, the ven- Venerica.rdia ventricosa from the Pleistocene of Caliericards, the ehamids, the rudistids, the lucinoids, the fornia. In all these valves "the cardinals and anterior 

carditids, and a single venerid, the genus Transenella. laterals are found to be completely transposed, leaving 

Unfortunately, few of the earlier references to abnor- only the posterior laterals normal to the hinge in which 

malities are accompanied by figures and for that reason they occur." 

are difficult to evaluate. However, Vest 36 figures A transposition of the cardinals and the anterior 

a right valve of the Recent Astarte corrugata Brown laterals is recorded in a left valve of Asta,rte concentrica 

which indicates a true hinge "inversion", and Reynell 37 from the upper Miocene at Yorktown, Va., and in a left 

figures a left valve of Astarte mutabilis Searles Wood valve of Astarte sima from the middle Miocene Shoal 

from the Coralline Crag (Pliocene) of Suffolk, England, River formation of Florida. In the Astartes, as in the 

in which the cardinals and anterior lateral are reversed. venericards, the posterior laterals remain normal. A 

In both of these forn1s, as in the valve of Venericardia similar transposition of cardinals and anterior laterals 

bashiplata, there is almost no evidence of abnonnality with the posterior laterals absent was noted in Transenin the shell characters exclusive of the hinge. ella stimpsoni, a Recent species found off the Florida 

Dall 38 observed that Keys. Abnormalities in the posterior late1·als were 

a peculiarity which has been noticed in several of the genera noted in a right and a left valve of Venericardia 

of Astartidae is the tendency to reversal of the hinge teeth in parva frmn Claiborne Bluff in which the cardinals and 

relation to the valves, the dentition normal to the right valve anterior laterals remained normal. A curious conI being found in the left, and vice versa. This peculiarity is dition is also noted in two paired Unio japanensis in 

especially notable in Goodallia, where, out of one lot examined, 

nearly one-third had the hinge reversed. which the cardinals are normal, the anterio:r latrrals 

The genotype of Goodallia is a Recent species of which absent, and the posterior laterals transposed. 

every individual examined by us presented a normal . No shell was found in which the transpos:~tion was 

hinge. N 0 abnormalities were observed in any of the complete, nor any in which the transfer of the anterior 

Recent or of the later Tertiary species, but in the sub- laterals was unaccon1panied by that of the cardinals. 

genus Microstagon Cossmann,ag founded on several By way of explanation, Popenoe and Findlay cite the 

close genetic relationship of the cardinals and anterior 3t Popenoe, W. P., and Findlay, W. A., Transposed hinge structures in Iamellibranchs: San Diego Soc. Nat. History Trans., vol. 7, no. 26. pp. 299-318, pl. 19 (17 laterals and the independent development of the 

fig3~·~~~~!~-Davies, A., L'inversion de la cbarniere chez les lamellibranches: Soc. posterior laterals. In 25 . of the 26 abnormal valves 

geol. France Compte rendu, 8 juin, 1925, pp. 156-158. which they studied the posterior laterals are a specific 36 Vest, w. von, Ueber die Bildung und Entwicklung des Bivalven-Schlosses: character. In 21 of the 25 the posterior laterals are 

Siebenbiirg. Ver. Naturwiss .. Verb. u. Mitt., Banrl48, pp. 25-150, 1898 [1899]. 

37 Reynell, A., On Astarte mutabilis witn reversed hinge dentition: Malacol. Soc. normal but the cardinals and anterior laterals are transLondon Proc., vol. 8, pp. 4, 5, text figure, 1908. 

aa Dall, W. H., Contributions to the Tertiary fauna of Florida: Wagner Free Inst. 

Sci. Trans., vol. 3, pt. 6, p. 1482, 1903. 

ag Cossmann, Maurice, Catalogue illustre des coquilles fossilE'.S de !'Eocene aes 

environs <le Paris, app. 2, p. 11, 1896. 

fo Hanna, M. A., Notes on the genus l-7enericardia from the Eocene of the west 

coast of North America: California Univ. Dept. Geol. Sci., Bull., \"O}, 15, no. 8, 

p. 287, pl. 36, fig. 4, pl. 38, fig. 4, 1925. 

u Popenoe, W. P., and Findlay, W. A., op. ~it., p. 306. 
GEOLOGICAL SURVEY 

Height Width Clntlil'lt> r.f .., n.,.n 

Low High Average Low High Average 

Venericardia planicosta Lamarck 75 84 80 75 82 79 Trigonocordate 

mediaplata Gai·dner and Bowles, n. sp. 34 58 45 35 60 48 Ovate-trigonal 

nanaplata Gardner and Bowles, n. sp. 41 60 49 40 61 52 Trigonocordate 

nanaplata nanna Gardner and Bowles, n. subsp. 21 39 30 21 40 30 Quadrocordate 

negritensis Olsson Not given Obliquely subtrigonal 2 

bashiplata Gardner and Bowles, n. sp. 58 79 65 56 76 63 Trigonocordate 

ascia Rogers 80 3 803 ·Transversely ovatetrigonal 

hatcheplata Gardner and Bowles, n. sp. , 59 85 70 59 78 63 Obliquely cordate 

claiboplata Gardner and Bowles, n. sp. 55 78 72 55 72 70 Trigonocordate 

c·acamai Gardner and Bowles, n. sp. ,55 70 65 55 65 61 Ovate-trigonal 

restinensis Olsson Rarely exceeding 5'0 mm. 2 Well-rounded to 

subquadrate 2 

gulielmi Gnrdnet· ·and Bowles, n. nante 14 17.6 Broad ovate4 

pilsbryi Stewart 83 93 87 82 103 93 Trigonal 

angustoscrobis Gat·dnet· and Bowles, n. sp. 30 32 Transversely ovate 

to obliquely trigonal 

cookei Gardner and Bowles, n. sp. 37 40 38 39 41 40 Transversely ovatetrigonal 

claviger Gardner and Bowles, rr. sp. 62 74 66 61 75 67 Transversely ovatetrigonal 

horatiana Gardner 60 86 74 63 90 77 Ovate-trigonal to 

hatchet-shaped 

stewarti Gardner and Bowles, n. sp. 69 94 79 72 97 80 Ovate-trigonal to 

hatchet-shaped 

tenosiensis Rutsch 48 90 55 48 86 00 Rounded to transversely ovate 

pacifica Olsson 49 50 49 52 53 52 Rounded to subquadrate 

turneri Gardner and Bowles n. sp. 66 85 70 73 94 77 Quadrate 

peruviana Olsson 66 80 Subquadrate 

potapacoensis Clark and Martin 27 43 36 26 42 35 Obliquely trigonal 

labreaensis Olsson 34 41 38 34 40 37 Obliquely trigonal 

d iga Gardner and Bowles, n. Sl>· 59 7·1 63 51 65 58 Obliquely trigonal 

to ovate-trigonal 

80-100 2 75-94 2 0 

clavidens Grzybowski Hatchet-shaped -

parinensis Oh;son 130 115 Obliquely trigonal 

francescae Gardner and Bowles, n. sp. 28 27.5 Trignnoquadrate 

jewelli Gardner 60 67 65 63 70 68 Transversely ovateI 

trigonal 

bijuana Gardner and Bowles, n. sp. Specimens incomplete 

smithii Aldrich. 40 53 50 43 56 

aposmithii Gardner and Bowles. n. sp. 70 117 95 64 113 

regia Conrad 75 90 85 82 95 

austroplata Gardner and Bowles, n. sp. ' 64 105 90 65 103 

densata pendletonensis Gardner and Bowles, n. subsp. 22 29 27 22 30 

densata Conrad 21 47 37 21 49 

zapatai Gardner and Bowles, n. sp. 65 70 66 52 68 

apodensata Gardner and Bowles, n. sp. 45 71 55 45 70 

klimacodes Gardner and Bowles, n. sp. 33 53 47 33 49 

greggiana Dall 52 55 53 47 53 

mingoensis Gardner and Bowles, n. sp. Specimens incomplete 

hesperia Gardner 

moa Gardner 

37 

30 

1 For each species the upper part of the drawing shows the 

vertical section and the lower part the Ionghudinal section. 

2 ,A.ccording to Olsson. 

~According to Clark and Martin. 

4 According to Dall. 

37 

34 

I 

52 In Hated-cordate 

93 Hatchet-shaped 

90 Hatchet-shaped 

95 Obliquely cordate 

28 Transversely ovate 

38 Obliquely cordate 

64 Trigonocordate 

55 Trigonocordate 

45 Trigonal 

50 Subglobose 

Outline incomplete 

Transversely ovate 

Transversely ovate 

FBOl"ESBIONAL PAPER 11!9 PLATE U 

. 

Outline of l'ihs; \. Rib QQQOt 

Juvenile Adult Low High Average 

--

-

M ~ 27 34 31 High, heavy 

~ 

--

-

A/\ ~ 29 31 30 Low, light 

~ 

/V\ 

--

- ~ 25 29 26 Rather low ~ 

M ~ 

~ 

27 31 29 Low, broad 'S0- --

Unknown 22-24 2 Not described Not figured 

M ~ 

--

~ 24 31 27 High, wide 

~ M 

""""" 

~ 

27 29 28 Low, wide ~ -

./1./'v ~ 

---

- 27 32 29 High, massive 

~ 

--

IV\. 

--

~ 

29 32 31 High, heavy 

~ .J\.1\, 

~ 

-- ~ 

27 32 30 Very high, heavy 

~ Unknown 22-23 2 Not described Not figured 

~ ~ 

25 Low, light Unknown ----

JV\11. -------- 35 High, heavy, ~ 

32 

~ 38 

-- trigonal 

JV'V'- ~ 

- 32 Low, rather light ~ -- . ~ ~ 

~ 

37 40 38 Low, rather light ~ 

JV1, ~ 

~ ""'- ~6 28 27 Low, narrow ----

/\./\. 

- Obsolete 21 25 24 High, heavy 

~ .A./\. 

---- Obsolete 24 29 27 High, heavy ~ 

/\/'-

-- Obsolete 27 30 28 Low, narrow ~ 

/V\ 

---

~ 

Obsolete 28 32 31 Low, narrow ~ 

~ ......-...-__ 

~ 

--- 28 28 23 Low, wide 

~ 

A/\. Obsolete 24 High, heavy Not figured 

--- - ../V\.. 

---

~ 

Obsolete 21 24 22 Very high, heavy 

~ 

---

./'A 

~ 

~ 19 .20 19 High, heavy ~ 

Not 

served 

pre- ~ Obsolete 24 27 25 High, 

trigonal 

heavy, 1\ 

About 21 Unknown 2 V 

massive

cry wide 

2 

and 

~ 

Not preserved 22 High, wide, 

Not preset·ved ~ 

---------------. 19 ·Low, 

massive 

narrow "'-

~ 

Not preserved ~ 18 20 19 Unknown. Unknown 

./V\. 

~ 

~ 

--------- 20 .23 21 ·Heavy, narrow Unknown --

--

-

M 

-

-

nn 

25 36 29 Low, wide, light ~ 

JUL 

--

""""'" 

~ 

28 36 .32 High, 

massive 

narrow, )\ 

.IV\.. / v \. 

JlJl 

--

~ 28 30 29 Rather 

heavy 

high. 

~ 

~ 

/'./\. ~ 

22 22 22 Low. very heavy 

~ 

~ 

27 30 29 Low, wide '5'-. --

~ 

/'v-... ~ 

23 29 27 High, wide, heavy ~ 

~ 

JV\. ~ 24 26 25 High, narrow Unknown --

--

./\./'.. 

~ 

~ 

27 34 31 Low, wide ~ 

--

~ 

/\!\. ~ 

27 31 29 Medium, narrow 

~ 

.1\A Jl.JL 

--

- ~ 33 35 34 Low, light ~ 

Not preserved 

~ 

26 28 27 High, light Unknown 

Not preserved ~ 

~ 

20 Low, rather heavy Unknown 

A...A. 

Not preserved ' .A....A...A_ 18 22 19 Unknown Unknown .. 

DIAGRAMMATIC REPRESENTATION OF DIAGNOSTIC CHARACTERS OF THE AMERICAN SPECIES OF THE VENERICARDIA PLANICOSTA GROUP. 
BIBLIOGRAPHY 165 

posed. The other 4 show transposed posterior laterals, 

tho ugh the rest of the hinge is normal. They believe 

thatthe abnormal hinges * * * represent examples of a systematic abnormality, not pathologic in its origin, in which 

certain of the primary lamellae from which hinge teeth are 

derived have developed in the opposite valve from that in which 

they are normally found. The fact that teeth become transposed in groups corresponding to these primary lamellae and 

that these teeth are precisely similar to those occurring in a 

normal hinge are considered as evidence for this opinion. The 

fundamental causes bringing about this transposition are 

unknown. 42 

BIBLIOGRAPHY 

Abrard, Rene, Le Lutetien du bassin de Paris; Essai de rronographie stratigraphique, 388 pp., 32 text figs., 4 pls., 4 maps, 

Angers, 1925. 

Ameghino, Florentino, L'age des formations sedimentaires de 

Patagonie, pp. 1-2311 faunal and correlation tables, no iJls., 

Buenos Aires, 1903. 

Archangelsky, A. D., Depots paleocenes de la region volgienne 

du gouvernement de Saratov et leur faune: Materialier zur 

Geologie Russlands, vol. 32, pp. 1-207, 12 pls., 1904. 

Archangelsky, A. D., Sur quelques Ostrea du Paleoc{me e.t du 

Cretace superieur de La Russie: Annuaire geol. et min3ral. 

Russie, vol. 7, pt. 7, pp. 1-27, pl. 4, 1905. 

Bede, Paul, sur une nouvelle espece de Nautile des ter~ains 

This paper of Popenoe and Findlay is the most ex- phosphates du Sud Tunisien: Soc. sci. nat. Maroc Bull., vol. 

haustive in its treatment of a restricted subject; they 12, pp. 281-287, 2 text figs., 1932. 

assembled the published material, added a large amount Bohm, J., Eozane und miozane Versteinerungen aus An.~ola: 

of new material, and made a successful attempt to Deutsche geq_l. Gesell. Zeitschr., Band 81, P· 450, 1929. 

Boswell, P. G. H., Tertiary group, in Handbook of the geology 

rationalize it. of Great Britain, xii, 556 pp. incl. illus., maps, tables, 1929. 

0dner 43 reported an apparent hinge inversion in a Bosworth, T. 0., Geology of the Tertiary and Quaternary pe~iods 

Pisidiurri which carried normal young in its gills, thereby in the northwest part of Peru, pp. 1-434, pls. i-xxvi; fo'·1ers 

indicating to him that the character was not heritable. i-xi; figs. 1-150, 1922. 

This is dubious proof, however, for Crampton 44 in his Boussac, Jean, Etudes stratigraphiques et paleontologique~ sur le nummulitique de Biarritz: Annales Hebert, tome 5, 96 pp., study of the land gastropod Partula found that, with 5 24 pls., bibliography, 1911. 

exceptions out of more than 3,000 shells examined, the Bruggen, J., Grundzuge der Geologie und Lagerstattenk'mde 

young produced at a given time were similarly coiled Chiles, 1934. 

but that they might or might not inherit this character' Burckhardt, Carl, Le gisement .supracretacique de Roca (Rio 

from the parent. A more significant observation is that Negro): Museo de la Plata Rev., tomo 10, pp.1-16, 4pls., 1901. 

Children, J. G., Lamarck's genera of shells: Jour. Sci., Lit., and 

in the subsequent dissection of the anin1al of Pisidiu.m h A 2 298 322 1823 t e rts, vol. 14, no. 8, pp. - , . 

the organization of the soft parts was proved to be Cooke, C. \V., and Stephenson, L. W •• The Eocene age of the 

normal. supposed late Upper Cretaceous greensand marls of New Jer· 

Although shell abnormalities have been observed and sey: Jour. Geology, vol. 36, PP· 139-148, 1928. 

d d f h h b I Cossmann, Maurice, Sur quelques grandes venericarder de 

recor e or years past, t ey ave never een exp ained. l'Eocene: Soc. geol. France, 4e ser., tome 1, pp. 652_656, l901. 

0dner 45 in commenting upon Reynell's "assumed" Cossmann, Maurice, Pelecypodes du Montien de Belgique: Mus. 

inversion of Astarte mutabilis and of smne Pisidium royale histoire nat. Belgique Mem., tome 5, 76 pp., 8 pls. 

hinges is incl:iJ;led to treat them as displaying "a mere Bruxelles, 1908. 

displacement of the hinge elements", and Bernard ,46 Cox, L. R., The Mollusca of the Hangu shales: Geol. Survey 

who devoted his professional life to the observation of India, Palaeontologia Indica, new ser., vol. 15, pt. 8 of The 

fossil fauna of the Samana Range and some neighboring areas, 

the lamellibranch hinge, stated in his last paper that pp. 129-222, pis. 17-22, bibliography, 1930. 

he knew of no true inversions among the lamellibranchs, Dareste de la Chavanne, Jr., La region de Guelma- E'ude 

that each tooth had its own individuality, and that speciale des terrains tertiaires: Service carte geol. Algerie B,,n., 

there was no record of its being transferred from one pp. 1-263, pls. 1-5, 20 text maps and figs., 1910. 

valve to the other. Davies, A. M., Tertiary faunas, vol. 1, 406 pp., 565 figs., 1935; 

. vol. 2, 252 pp., 28 figs., 1934. 

This may very possibly be true of Pisidium, for the De Morgan, J., Mission scientifique en Perse, vol. 3, pts. 2 ar1 4, 

hinge characters in that group of fresh-water bivalves 1904. (See Douville, H., 1904.) 

are notably unstable, but in Vest's and in Reynell's Dickerson, R. E., Climatic zones of Martinez Eocene time: 

figured Astarte, in the shells figured by Popenoe and California Acad. Sci. Proc., 4th ser., vol. 7, no. 7, pp. 193-196, 

Findlay, and in the Venericardia under observation a 1 text fig., July 1917· Dixon, Frederick, The geology of Sussex, 1st ed., 1850; nev-r ed. 

"mere displacement", which is the mirror image of the (revised by T. R. Jones), 469 pp., 64 pls., 1878. 

normal hinge of the opposing valve, is more difficult to Douville H., in J. DeMorgan, Mission scientifique en P')rse, 

accept. vol. 3, Etudes geologiques, pt. 4, Paleontologie, Mollus-:.ues 

fossiles, pt. 2, pp. 191-380, pls. 25-50, 1904. u Popenoe. W. P., and Findlay, W. A., op. cit., p. 312. 

.a 0dner, N.H., Studies on the morphology, the taxonomy, and the relations of 

Recent Chamidae: K. svenska Vetensk. akad. Hand!., Band 59, no. 3, pp. 7, 8, 1919. 

"Crampton, H. E., The coincident production of dextral and sinistral young in 

the land gastropod Partula: Science, new ser., vol. 59, pp. 558-559, June 20, 1924. 

f5 0dner, N. H., op. cit., p. 8. 

f6 Bernard, Felix, Sur le developpement et la morphologie de la coquille chez les 

Jamellibranches: Soc. geol. France Bull., 3• ser., vol. 23, pp. 104-154, 28 text figs., 1895; 

rol. 24, pp. 54-82, 15 text figs., pp. 412-449, 15 text figs., 1896; vol. 25, pp. 559-566, 1897. 

Douville, H., La limite entre le Cretace et l'Eocene en Aquitaine, 

aux In des et au Soudan: Acad. sci. Paris Comptes rer dus, 

vol. 170, pp. 154-159, 1920. 

Douville, H., L' Eocene au Soudan et au Senegal: Com. etudes 

hist. et sci. Mrique occidentale fran«;aise Bull. 2, pp. 113-171, 

pls. 1-5, 2 text maps, correlation table, 13 text figs. of fofl~ils, 

1920. 
166 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

Gerhardt, K., Beitrag zur Kenntniss der Kreideformation in 

Venezuela und Peru: Neues Jahrb., Beilage-Band 11, pp. 65-

117, pis. 1, 2, 6 figs., 1897. 

Grabau, A. "\\.- ., Summary of the Cenozoic and Psychozoic 

deposits with special reference to Asia: Geol. Soc. China Bull., 

vol. 6, pp. 151-264, 1927. 

Gronwall, K. A., and Harder, Poul, Paleocaen ved Rugaard 1 

Jydland og dets Fauna: Danmarks geol. Unders~gelse, ser. 2, 

no. 18, 102 pp., 1 pl., 1 text map, resume, 1907. 

Grossouvre, A. de, Recherches sur la Crai Superieure: Mem. 

expl. carte geol. detaillee France, fasc. 2, pp. 561-1013, 39 

t~bles, 33 figs., 3 pls., 1891. 

Hanna, M.A., Notes on the genus Venericardia from the Eocene 

of the west coast of North America: California Univ., Dept. 

Geol. Sci., Bull., vol. 15, no. 8, pp. 281-306, pis. 36-44, 1925. 

Harris, G. D., in Waring, G. A., Notes on the paleontology in 

Geology of the Island of Trinidad, B. W. I.: Johns Hopkins 

Univ. Studies in Geology, no. 7, pp. 87-112, pis. 16-20, 1926. 

Hedberg, H. D., Stratigraphy of the Rio Querooual section of 

northeastern Venezuela: Geol. Soc. America Bull., vol. 48, 

no. 12, pp. 1971-2024, pis. 1-9, 2 text figs., 1937. 

Holst, N. 0., and Gronwall, K. A., Paleocen vid Klagshamm: 

Sveriges geol. undersoknings Skrifter, ser. C, no. 208, pp. 1-27, 

1907. 

von Ihering, Hermann, Les Mollusques des terrains cretaciques 

superieurs de 1' Argentine orientale: Mus. nac. Buenos Aires 

Anales, tomo 9, pp.193-229, 2 pls., 1903. 

von lhering, Hermann, Nuevas observaciones sabre moluscos 

cretaceos y terciarios de Patagonia: Mus. La Plata Rev., tomo 

11, pp. 1-17, 2 pls., 1904. 

von Ihering, Hermann, Les mollusques fossiles du Tertiare et du 

Cretace superieur de 1' Argentine--!, Les mollusques fossiles 

de l'etage rocaneen: Mus. nac. Buenos Aires Anales, tomo 14, 

pp. 1-36, 3 pis., 1905. 

von Ihering, Hermann, Les mollusques fossiles du Tertiaire et du 

Cretace superieur de I' Argentine: Mus. nac. Buenos Aires 

Anales, ser. 3, tomo 7, pp. i-xiii, 1-608, 611, 18 la.m., 16 figs., 

bibliography, 1907. 

von Ihering, Hermann, Die Umwandlungen des amerikanischen 

Kontinentes wahrend der Tertiarzeit: N eues Jahrb., BeilageBand 32, pp. 134-176, pl. 5, 1911. 

Kennard, A. S., Salisbury, A. E., and Woodward, B. B., The types 

of Lamarck's genera of shells as selected by J. G. Chi.ldren in 

1823: Smithsonian Misc. Coil., vol. 82, no. 17, pp. 1-40, 1931. 

von Koenen, A., fiber eine Paleocane Fauna von Kopenhagen: 

K. Gesell. Wiss. Gottingen Abh., vol. 32, pp. 3-128, pls. 1-5, 

1885. 

Kuhn, Othmar, Das Danien der Aussern Klippenzone bei Wien: 

Geol. und Pal. Abh., neue Folge, Band 17, Heft 5, pp. 1-84, 15 

text figs., 2 pls., bibliography, 1930. 

Lamay, Ed., Revision des Carditacea vivants du Museum national d'histoire naturelle de Paris: Jour. conchyliologie, tome 

66, pp. 218--276, 289-368, 1921. 

Leriche, M., Observations sur les terrains tertiaires des environs 

de Reims et d' Epernay: Soc. geol. Nord Annales, tome 36, p. 

367, 1907. 

Leriche, M., Surles relations entre bassins beige et parisien pendant l'epoque tertiaire: Soc. geol. Nord Annales, tome 38, p. 

350, 1909. 

Leymerie, A., Description geologique et paleontologique des 

Pyrenees de la Haute Garonne, 1,010 pp., 30 pls. of fossils, 

1881. 

Lukovic, 1\L T., The Eocene molluscan fauna from the area 

between the Aral Sea and Lake Chalkar and its importance: 

Annales geol. Peninsule balkanique, vol. 8, fasc. 2, pp. 19-82, 

pls. 2-4, correlation chart, distribution tables, Belgrade, 1926. 

Marshall, P., The 'Vangaloa beds: New Zealand Inst. Trans. and 

Proc. for 1916, vol. 49, pp. 45o-460, pls. 34-37, 1917. 

Matthew, W. D., Patagonia and the Pampas Cenozofc of South 

America-A critical review of the correlations o~ Santiago 

Roth, 1908: New York Acad. Sci. Annals, vol. 19, ro. 7, pt. 2, 

pp. 149-160, 1910. 

Maury, C. J., A contribution to the paleontology of Trinidad: 

Acad. Nat. Sci. Philadelphia Jour., 2d ser., vol. 15, pp. 25-112, 

pls. 5-13, 1912. 

Maury, C. J., The bearing of recent discoveries of earJy Tertiary 

shells near Trinidad Island and in Brazil on hypotb~ticalland 

routes between South America and Africa: South Af-ican .Tour. 

Sci., vol. 10, no. 4, pp. 92-96, 1913. 

Nagao, Takumi, Occurrence of Orthaulax in the PalaeogEne of 

Japan: Japanese Jour. Geology and Geography, vol. 3, no. 1, 

pp. 13-1~, 1 text map, 1 pl., 11 figs., 1924~ 

Nagao, Takumi, Palaeogene coal-bearing formations of the island 

of Kyilshti: Tohoku Imp. Univ. Sci. Repts., 2d ser., Geology, 

vol. 11, no. 1, pp. 1-21; 1 text map, 1 correlation table, Sendai, 

Japan, 1927. 

Nagao, Takumi, A summary of the Palaeogene stratigraphy of 

Kytishti, Japan, with some accounts on the fossiliferous zones: 

Tohoku Imp. Univ. Sci. Repts., 2d ser., Geology, vol. 12, pp. 

1-10, correlation table, 1 pl., Sendai, Japan, 1928. 

Nagao, Takumi, Palaeogene fossils of the island o'!' Kytishti, 

Japan: Tohoku Imp. Univ. Sci. Repts., 2d ser., Ge'llogy, vol. 

9, pp. 97-128, pls. 18-22; vol. 12, pp. 11-140, pis. 1-17, Sendai, 

Japan, 1928. 

N etschaew, A. V ., Die Fauna der Eocanablagerung~n an der 

Wolga unterhalb Saratow: Trudui Obschestva Kazan, vol. 

32, pt. 1, pp. 1-247, pls. 1-10, 1897. 

Newton, R. B., On -the lower Tertiary Mollusca of the Fayum 

province of Egypt [presidential address]: ·Malacol. Soc. 

London Proc., vol. 10, pp. 56-89, pis. 3, 4, 1912. 

Newton, R., Eocene Mollusca from Nigeria: Nigeria Geol. Survey Bull. 3, 148 pp., 12 pis., 1922. 

Obrutschew, W. A., Geologie von Sibirien, vol. 15, 572 pp., 10 

pls., 60 text figs., bibliography, 1926. 

Olsson, A. A:, Contributions to the Tertiary paleontology of 

northern Peru: Bull. Am. Paleontology, vol. 14, D'). 52, 154 

pp., 26 pis., 1928; vol. 15, no. 57, 50 pp., 8 pis., 1929; vol. 17, 

no. 62, 96 pp., 12 pis., 1930. 

Oppenheim, Paul, Die Eocaenfauna des Monte Postale bei 

Bolca im Veronesischen: Palaeontographica, vol. 4~, pp. 125-

221, pls. 12-19, 1896. 

Oppenheim, Paul, Zur Kenntnis alttertiarer Faunen ir 'Agypten: 

Palaeontographica, Band 30, Abt. 3, Lief. 1; Der Bivalven, 

erster Teil (Monomyaria, Heteromyaria und Siphonida integripalliata), pp. 1-164, pls. 1-17, 1903. 

Oppenheim, Paul, Zur Kenntnis alttertHLrer Faunen iu Agypten: 

Paleontographica, vol. 30, Abt. 3, Lief. 2, Der Bivalven, 

zweiter Teil, Gastropoda, Cephalopoda, pp. 165-348, pls. 

18-27, 1906. 

Oppenheim, Paul, Die eocane Invertebraten-Fauna des Kalksteins in Togo: Beitr. geol. Erforsch. deutschen Scbutzgebiete, 

Heft 12, 126 pp., 5 pls., bibliographic footnotes, 1915. 

Pervinquiere, Leon, Etudes de paleontologie tunisienne, vol. 2, 

p. 241, pl. 18, figs. 1-3, Direction gen. travaux publics, 1912. 

Quaas, A., Die Fauna der Overwegischichten und der Blatterthone in der libyschen Wuste, in Beitrag zur Kenntniss der 

Fauna der obersten Kreidebildungen in der libyschQ,n Wuste: 

Palaeontographica, vol. 30, pt. 2, 4th sec., pp. 153-334, pls. 

2o-33, correlation tables, 1902. 

Ravn, J. P. J., Molluskfaunaen i Jy11ands Tertiaerr.tlejringer: 

Acad. royale Sci. Danemark Mem., 7e ser., Sci., tome 3, pp. 

217-384, 1 map, 8 pls. of fossils, resume (French) of 6 pp., 

1907. 

Recluz, M. C., Sur laplace que doivent occuper dans h methode 

les genres Solemye, Venericarde et Leda: Jour. conchyliologie, 

vol. 10, 3d ser., pp. ~09-124, 1862. 
SYSTEMATIC DESCRIPTIONS 

I 

167 

Rutsch, R., Die stratigraphische Bedeutung der Venericardia 

planicosta und ihrer Verwandten: Eclogae geologicae Helvetiae. vol. 29, no. 1, pp. 151-186; pl. 16, June, 1936. 

Schlosser, Max, Die Eocaenfaunen der bayerischen Alpen: 

Bayer. Akad. Wiss. Abb., Math.-naturwiss. Abt., Band 30, 

Abh. 7, 1. Teil, Die Fauna des Unter- und Mitteleocaen, 207 

pp., pls. 1-6; 2. Teil, Die Obereocaenfauna, 68 pp., pls. 7, 8, 

1925. 

Schlosser, Max, Uber Tertiar und obere Kreide aus PortugiesischOstafrika: Bayer. Akad. Wiss. Abh., Math.-naturwiss. Abt., 

Band 32, Abh. 2, pp. 1-25, pls. 1-3, bibliography, 1928. 

Schwetzoff, M. S., Die Kreide-PaHiozanschichten von Schum: 

Soc. naturalistes Moscou Bull., vol. 40, nouv. ser., vol. 10, 

no. 2, pp. 211-250, 1932. 

SJodkewitsch, W. S., The mollusk fauna of Mandrykovka, 

Venericarditidae: United Geol. and Prospecting Service U. S. 

S. R. Trans., fasc. 258, pp. 1-31, 6 text figs., .3 pls., 1933. 

Trechmann, C. T., The yellow limestone of Jamaica and its 

Mollusca: Geol. Mag., vol. 60, pp. 337-367, pls. 14-18, 1923. 

Vaughan, T. W., The biologic character and geologic correlation 

of the sedimentary formations of Panama in their relation to 

the geologic history of Central America and the West Indies: 

U. S. Nat. Mus. Bull. 103, pp. 547-612, 1919. 

Vaughan, T. W ., Correlation of the later Mesozoic and Cenozoic 

formations of New Zealand: First Pan-Pacific Sci. Conf. (under 

auspices Pan-Pacific Union) Proc. (Bishop Museum Special 

Pub.), pt. 3, no. 7, pp. 713-743, correlation tables, ·bibliography, text map, 1921. 

Vaughan, T. W., Basis of the correlation of post-Cretaceous 

formations in the Pacific region: First Pan-Pacific Sci. Conf. 

Proc. (Bishop Museum Special Pub.), pp. 866-873, 1921. 

Vincent, Emile, La faune. paleocene de Landana: Mus. Congo 

beige Annales, Geologie, ser. 3, vol. 1, fasc. 1, pp. 1-92, pls. 

1-10. 1913. 

Vincent, Emile, Mollusques des couches a Cyrenes (Paleocene 

du LimbourgJ: Mus. royal hist. nat. Mem. 43, 43 pp., 7 fossil 

pls., portrait of Emile Vincent and his bibliography, 1930. 

Waring, G. A. (with notes on the paJeontology by G. D. Harris), 

The geology of the island of Trinidad, B. W. I.: Johns Hopkins 

Univ. Studies in Geology, no. 7, 180 pp., 20 pls., 1 text fig., 

1926. 

Windhausen, A., The problem of the Cretaceous-Tertiary boundary in South America, and the stratigraphic position of the 

San Jorge formation in Patagonia: Am. Jour. Sci., 4th ser., 

vol. 45, pp. 1-53, 3 text figs., invertebrate distribution table, 

1918. 

Wood, S. V., Monograph of the Eocene bivalves of England, 

vol. 1, 182 pp., 25 pls. 1861-1871; Supplement, 24 pp., 2 pis., 

Palaeontographical Soc., 1871. 

Woods, Henry, A monograph of the Cretaceous Lamellibranchia 

of England: London Palaeontographical Society, vol. 2, pt. 

3, pp. 121-128, 1906. 

Yabe, Hisakatsu, Cretaceous stratigraphy of the Japanese 

islands: Tohoku Imp. Univ. Sci. Repts., 2d ser ., Geology, vol. 

11, no. 1, pp. 27 (1)-100 (74), 15 text figs., 1 correlation table, 

7 quarto pls., Sendai, Japan, 1927. 

Zittel, K. A., Beitrage zur Geologie und Palaeontologie der 

Libyschen Wiiste und der angrenzenden Gebiete von Aegypten, 

Teil 1: Palaeontographica, Band 30, pt. 1, pp. 1-147, text 

sketches, 1883. 

SYSTEMATIC DESCRIPTIONS 

Genus VENERICARDIA Lamarck, 1801 

1801. Lamarck, Systeme des animaux sans vert.ebres, p. 123. 

Type by subsequent designation Venericardia imbricata Lamarck= Yenus imbricata Gmelin (Schmidt, C. F., Versuch 

i.iber die besle Einrichtung zur Aufstellung, Behandlung 

und Aufbewahrung der verschiedenen Naturkorper und 

Gegenstande der Kunst, vorziiglich der Conchyliensammlungen; nebst kurzer Beurtheilung der conchyliologische Systeme, pp. 57, 176, 1818). 

Shell of moderate dimensions, from 25 to 40 'm.illimeters high and slightly wider; diameter more than 

two-thirds the height; shell not very heavy, evenly but 

not strongly inflated. Umbones anterior, not consr;~uous]y prominent, but well rounded to their tips, which 

are turned inward and forward and are almost in contact, the right umbo slightly higher than the left. 

Lunule exreedingly small, subumbonal, slightly less 

narrow in the right valve than in the left. Escutcheon 

not defined. Anterior extremity short, roun<iing 

smoothly into the arcuate base line. Posterior extremity obtusely truncate. Posterior area indic."',ted 

only by the obscure truncation, a slight flattening o~ the 

shell, and a slightly closer spachig of the rac1

ials. 

Sculpture of 30 to 33 narrow A -shaped radials, sharply 

crenate near the tips of the umbones, outlined on the 

adolescent and adult stages by a heavy, sharply noded 

cord. Ligament opisthodetic, deeply inset, produced 

for more than half the length of the dorsal margin. 

A short thin laminar anterior cardinal, an obliquely 

produced cuneate medial, and a much-produced larrinar 

posterior cardinal in the right valve; a moderr.tely 

heavy anterior cardinal and a produced laminar posterior cardinal in the left valve; a faint grooving br,rely 

perceptible on the lateral surfaces of the heavier tr~th; 

no true laterals developed but a slight pucker in the 

shell at the extremity of the lunular groove possibly 

analogous to an anterior lateral. Pedal scar smalJ but 

deeply impressed, close to the margin just above the 

dorsal extremity of the deeply impressed pyriform r.nterior adductor scar. Posterior adductor less de.epJy 

impressed, semielliptical. Pallial line obscure, sjn1ple. 

Inner margins deep]y crenate. 

The description is based upon genotypes from the 

Paris Basin. 

The type is one of a rather large group of closely 

related species abundantly represented in the Paris 

Basin. Venericardia rotunda, from the Gulf Eorene, 

especially the larger individuals from the Gosport fand, 

has very much the same general aspect and more closely 

resembles V. imbricata than does the· coarse!-, more 

inflated V. alticostata, with which imbricata has been 

commonly compared. 

Venericardia is separated from Oardita by the dentition of the right valve. In Oardita there is a hr.q,vy, 

. more or less cuneate, subumbonal cardinal, and behind 

it an obliquely produced, often laminar posterior cardinal; in Venericardia there is, in addHion to these two 

teeth, a third right cardinal, whlch is short, thin, and 

anterior to the heavy subumbonal tooth. 

Cox, in "The fossil fauna of the Samana Range" 

(Palaeontologia indica, new ser., vol. 15, p. 206), cites 

Oardita variegata Bruguiere as the genotype, l:ttsed 
168 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

upon Fleming's reference to it in the Encyclopedia 

Britannica supplement to the 4th, 5th, and 6th editions, vol. 3, p. 305, probably February 1818. Under 

the subject heading "Linnaean genera," Fleming writes 

of "the genus Cardita of Bruguiere, represented by C. 

variegata Lister, tab. 344, fig. 84." This does not seem 

to constitute a type designation. Cardita variegata is 

a mytiliform species distinct generically from Venericardia imbricata Lamarck of the Paris Basin. The 

acceptance of variegata as the type of Cardita would 

necessitate the realinement of Venericardia as well as 

Card ita. 

Subgenus VENERICOR Stewart 

1930. Venericor Stewart, Gabb's California Cretaceous and Tertiary type Lamellibranchs; Acad. Nat. Sci. Philadelphia 

Special Pub. 3, p. 153. 

Type by original designation: Yenericardia planicosta Lamarck 

(Eocene of the Paris Basin and of the Bracklesham beds 

of England). 

Shell large, heavy, its apparent inflation increased by 

the thickness of the shell. Outline trigonocordate, 

strikingly cordate in the profile of the double valves. 

Umbones inflated, turned inward and forward, that of 

the right valve a little higher and fuller than the left, 

placed well forward. Lunule narrow, deep, slightly 

wider in the right valve than in the left and deeper in 

the left valve than in the right, delimited by a groove 

that strongly dents the inner margin. Escutcheon not 

defined. Anterior extremity short, rounding obliquely 

into the upcurved base; posterior lateral margin obscurely truncate. Posterior area indicated by the 

obtuse flattening of the shell and a change in the 

character of the radial sculpture. Radials 26 on the 

anteromedial portion of the left valve, possibly 1 more 

· on the right and 7 on the posterior area; the earliest 

ribbing very narrow, sharply crested and finely crenate, 

the adolescent and early adult ribs on the anteromedial 

portion simple, flat-topped and slightly wider than the 

U-shaped channels that separate them; the ribs upon 

the posterior area narrow, crenate, and crowded; 

radial sculpture overrun by the incremental toward the 

margins of the adult shell, most persistent anteriorly; 

no trace of lateral cording but a slight tendency toward 

on und~rcutting of the ribs discernible. Ligament 

deeply inset, marginal, mounted on heavy nymphs. 

Hinge plate high, trigonal. A short thin laminar 

anterior cardinal, a heavy, somewhat scimitar-shaped 

medial cardinal, and a laminar posterior cardinal produced along the inner margin of the nymph in the 

right valve; a short anterior and produced posterior 

cardinal, both of them moderately heavy and separated 

by a deep and obliquely produced ligan1ent pit, in the 

left valve. Inner surface thickened over the area of 

the adherent mantle. Pedal pit very deep. Anterior 

adductor scar also very deep and obliquely produced; 

posterior scar broader, not quite so deep. Pallial line 

ragged and rather far removed from the deeply crenate 

inner margins. 

The description is based on the subgenotype, U. S. 

National Museum no. 12704 (pl. 35, figs. 1, 2; pl. 36, 

figs. 5, 6), from Grignon, in the Paris Basin, th~ locality 

from which Lamarck received his type material for the 

species. 

Specimens in our collections from the Brackleshan1 

beds of Selsey, Sussex, differ from those from the Paris 

Basin in the higher, more anterior beaks, higher hinge 

plates, slightly lower rib count, and less persistent 

ribbing. 

The diagnostic characters of some of. the specjes 

considered are diagrammatically represented on plate 

32. 

VENERICARDIA MEDIAPLATA stock 

Venericardia (Venericor) mediaplata Gardner and Bowles, n. sp. 

Plate 33, figures 1, 3 

1894. Venericardia planicosta Lamarck. Aldrich, Report on 

geology of Coastal Plain of Alabama, p. 242, pl. 12, 

fig. 3. Not Venericardia planicosta Lamarck~ 1806. 

1896. Venericardia planicosta Lamarck [part]. Harris, Bull. 

Am. Paleontology, vol. 1, no. 4, p. 58, pl. 4, fig. 13. 

1903. Venericardia mooreana Conrad [part]. Dall, Wagner 

Free Inst. Sci. Trans., vol. 3, pt. 6, p. 1422. 

1909. Venericardia planicosta Lamarck [part]. Grabau and 

Shimer, North American index fossils, Inv~rtebrates, 

vol. 1, p. 545, fig. 747 (left valve). 

Shell of moderate dimensions for the genus. Umbones low, anterior, pointed forward toward the. small 

and not very conspicuous lunule. Valves n10st inflated 

anteriorly, flattening toward the posterior ventral 

margin. Posterior area delimited both by the sculpture and by an obtuse rostrum. Sculpture worn but 

probably retaining its original character, excepting upon 

the decorticated umbones; radials simple, flattening 

away from the umbones; 20 upon the anterior and medial 

portions of the valve, separated by only linear interspaces; the 9 posterior radials not so wide nor so flattened as those upon the disk. Hinge plate low and 

broad. Dentition ·normal for the group but not conspicuously heavy. 

Dimensions of holotype: Height 58.0 millimeters, 

width 60.0 millimeters, convexity 25.0 millimeters. 

Holotype, a left valve: U. S. National Museun1, 

no. 137241. 

Type locality: Geological Survey station.281, Prairie 

Creek, Wilcox County, Ala. Clayton formathn of the 

Midway group. 

Venericardia mediaplata differs from V. smithii 

Aldrich in the he a vier, less inflated shell and the lower, 

broader, and more closely spaced radials. The rib 

counts run about the same. V. mediaplata is probably 

n1ore limited in its distribution both in time and in 

space. 

The description and figures of Yenericardia duponti 
SYSTEMATIC DESCRIPTIONS 169 

Cossmann 47 suggest a relationship to V. mediaplata 

much closer than that usually indicated by two species 

separated by an oceanic basin. ·No examples of 

duponti, unfortunately, are available for comparison. 

Distribution:47a 

Midway group undifferentiated: 

Georgia, Houston County, 4956P, Robert Sappy's 

place, 4 miles east of Marshallville on the east side 

of a branch of Spring Creek in a ravine below negro 

cabins. Clay County 5488P, Fort Gaines, Chattahoochee River, limestone at the base of the bluff. 

Midway group, Clayton formation: 

Alabama, Wilcox County, 264P and 28iP, Prairie 

Creek. 

Mississippi, Tippah County, 6497r, Bluff on south 

side of Owl Creek, 2% miles northeast of Ripley 

and about one-fourth mile east of the Ripley-Troy 

road, near the base of the formation. 

Tennessee, Hardeman County, 2141r, Porters Creek. 

Midway group, Kincaid formation: 

Texas, Limestone County, 6560r, near Horn Hill. 

Maverick County, 6575P, White Bluff, Rio Grande 

River, 4~ miles west of south of Windmill (Jacal) 

ranch house. 

Venericardia (Venericor) nanaplata Gardner and Bowles, n. sp. 

Plate 33, figures 2, 7 

Shell small, solid, cordate-trigonal, not, as a rule, very 

highly inflated. Posterior area defined by the modified 

sculpture rather than by the contour. Lunule small, 

deep-set, wider in' the right valve than in the left. Liganlent marginal and external; no true escutcheon. Ribs 

in the holotype, 21 on the anterior and medial portions 

of the left valve, 6 on the posterior; 20 on the anterior 

and medial portions of a right valve, 6 on the posterior; umbonal ribbing narrow and fairly strong, the 

ribs broadening both relatively and absolutely toward 

the ventral margin, so that at the margin in the types 

the interradials are linear; posterior ribs low, increasingly obscure toward the margin, the 3 nearest the 

dorsal margin, nodose near the umbones and broadening away from the umbones, the remaining 3 narrower 

and cordlike. Growth lines crowded and fairly strong 

ventrally. Hinge plate wide, fairly high. Medial 

cardinal in right valve obliquely cuneate and heavy, 

the remaining teeth adequate. Ligament groove deep; 

the nymph rather heavy for the size of the shell. Interior thickened over the area of the mantle attachment. 

Pedal scar small, deep-set; adductor scars, relatively 

large, sunken. Inner margins coarsely crenate. 

Dimensions of holotype: Height, 49.0 millimeters; 

width, 52.0 millimeters; convexity, 18.3 millimeters. 

Ho1otype, a left valve: U. S. National Museum, 

no. 137226. 

•7 Cossmann, Maurice, Pelecypodes du Montien de Belgique: Mus. royal histoire 

nat. Belgique Mem., tome b, pp. 52-53. pl. 5, figs. 12-17, pl. 6, figs. 1-5, 1908. 

t7 a r Rare; P present; • common; a abundant; pr prolific. 

Type locality: Geological Survey station 271, Nanaa 

falia Bluff, Tombigbee River, Marengo County, Alabama. Wilcox group, Nanafalia formation. 

Venericardia nanaplata of the N anafaJja and Tu<:'eahoma formations is apparently descended from V. 

mediaplata, from which it differs in the slightly lcwer 

rib count, the less distinct posterior area, and the 

higher anterior and medial costae. The umbonal ribbing in some of the younger individuals is well preserved and shows a very distinct crenation. 

Venericardia nanaplata includes the smallish trigonocordate species with rib counts running usually f~om 

25 to 27, the half dozen upon the posterior area d:-ring 

out away from the umbones. The characters that 

show variation to a marked degree are the. umbonal 

inflation and the persistence of the ribs anteriorly and 

merually. This variation has been recognized in the 

taxonomy. Only in the more compressed forms do 

the ribs die out toward the anterior and ventral margin, 

while inflated individuals of the same or greater dimensions show ribbing as strong at the margins ar on 

the medial part of the disk and have an immature 

aspect. While the persistence of the ribbing and the 

convexity do not vary independently, they do show an 

unbroken sequence, so that any taxonomic break is 

more or less arbitrary. However, a certain racial 

fixity is indicated, for the more compressed individuals 

have not been recognized in the later formations, while 

the inflated race apparently persists in the Baslu in the 

form of the much larger bashiplata. The compressed 

race, the V. nanaplata nanna With evanescent anterior 

and medial'ribbing, has much the general appearr,nce 

of V. densata of the Claiborne, but the later form 1nay 

be definitely recognized by the nodose and laterally 

ridged umbonal costals. Both the Nanafalia and the 

Tuscahoma carry compressed and inflated races but 

the inflated individuals are less rare in the later formation. 

Distribution: 

Wilcox group, Nanafalia formation: 

Alabama, Marengo County, 2716 and 56416 , Nanafalia Bluff, Tombigbee River. 

Wilcox group, Tuscahoma sand: 

Alabama, Monroe County, 3118P, Greggs Landing, 

Alabama River. 

Venericardia (Venericor) nanaplata nanna Gardner and Bovles, n. subsp. 

Plate 33, figures 4, 5, 10, 11 

Shell small, solid, evenly but not strongly inflated, 

the beaks not very prominent and the resultant outline 

rather squarish. Posterior extremity obtusely trunc1',te. 

Ribbing close and regular, crenate at the umbones, low 

and broad and overridden by the incrementals near the 

ventral margin; ribs 20 upon the medial and anterior 

areas, 9 upon the posterior area of the co types; poste~or 

ribs cordate and persistent, with some loss of strength, 
170 'l'HE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

to the border. Hinge area low and broad, the cardinals 

inflected to be rudely parallel to the dorsal margin. 

Muscle scars not conspicuous. Inner ventral and 

lateral margins crenate. 

Dimensions of cotypes: Right valve, height 28.0 

n1illimeters, width 31.0 millin1eters, convexity 11.8 

millimeters. Left valve, height 30.6 millimeters, width 

31.3 millimeters, convexity 12.5 millimeters. 

Cotypes, a right and a left valve of different individuals: U.S. National Museum, no. 373028. 

Type locality: Geological Survey station 5604, Greggs 

Landing, Alabama River, Monroe County, Ala. Wilcox group, Tuscahoma sand. 

The subspecies nanna from the Tuscahoma differs 

from the Nanafalia nanaplata in the smaller size, less 

trigonal and more uniformly compressed outline, and 

higher rib count. Among 388 rib counts from Greggs 

Landing, 118 earried 29 ribs; 85 carried 30; 82 carried 28; 

ribs on the ren1aining valves numbered more than 30 or 

less than 28. This increase over the nanaplata rib 

count is due to the increase in number of the posterior 

ribs from six or seven to nine, the number of medial 

and anterior ribs running about the same in the Nanafalia species and the Tuscahoma subspecies. Although 

the shells do not have the aspect of adolescents, the 

tendency toward an obsolete ribbing at the ventral 

margins, particularly upon the posterior area, is less 

pronounced in the subspecies. The subspecies apparently died out at the end of the Tuscahoma epoch, 

while nanaplata species strictu, which persist.s in greatly 

reduced numbers in the Tuscahon1a, may have given 

rise to V. bashiplata n. s~, a prominent Fenericardia 

of the Bashi. 

Distribution: 

Wilcox group, Tuscahoma sand: 

Alabama, Monroe County, 268Pr, 3118Pr, and 5604Pr, 

Greggs Landing, Alabama River. 

Venericardia (Venericor) negritensis Olsson 

Plate 33, figure 6 

1922. Venericardia planicosta Lamarck (group), form A. Woods, 

Geology of northwest Peru, pp. 66-67, pl. 4, fig. 1. 

1928. Venericardia planicosta var. negritensis Olsson, Bull. Am. 

Paleontology, vol. 14, no. 52, p. 26, pl. 5, figs. 1, 2. 

1930. Venericardia planicosta var. negritensis Olsson. Stewart, 

Acad. Nat. Sci. Philadelphia Special Pub. 3, p. 172. 

1936. Venericardia negritensis Olsson. Rutsch, Eclogae geol. 

Helvetiae, vol. 29, pp. 169, 170, 177. 

This variety is the common and characteristic type in the 

Negritos formation. The usual form is obliquely subtrigonal 

with low, flattened umbos and with erect or but slightly 

curved or inclined beaks. The shells are but slightly convex, 

sometimes appearing flattened or depressed, especially near the 

ventral or basal margins. The sculpture is strong, with relatively few, heavy persistent ribs, widening out very noticeably 

spaces. From the anterior extremity to the umbonal slope the 

ribs number from 17 to 19. 

The umbonal slope or ridge is usually well defined, and the 

sculpture of the dorsal-posterior submargins is quite different 

from the rest of the shell disk. Except in the very earliest 

stages, the ribbing of the dorsal margins is weak, the ribs quickly 

fading out distally, and the surface becoming smooth or sculptured simply by crowded growth lines. The low ribs of the 

posterior-dorsal submargin number 4 or 5, so th~.t the total 

number of ribs over the whole surface is 22 to 24. 

Localities and geologic occurrence.-Negritos formr.tion, Negritos La Brea.-Olsson, 1928. 

Woods says of this form: "The latter [specimens 

from the Turritella series] approach closely the North· 

American form named V. planicosta va:r. Conrad 

(1865), from the Aquia formation of Mar:.,.land and 

the Wilcox group of the Southeastern States. Near 

the umbo the ribs are narrower than the grooves, but 

they soon broaden, and at the ventral Inargin are 

much broader than the grooves." 

Stewa.rt rema.rks: ''V. planicosta negritensis, from the 

Negritos formation, resembles V. planicosta, from the 

Wilcox, particularly those from ThomasYille. The 

Alabama specimens have the weaker dorsal ribs 

described by Olsson." 

No specimens of the Peruvian species are available 

for comparison. The outline of the individual figured 

by Woods 48 and its clean-cut ribs recall Venericardia 

bashiplata of the fauna at Woods Bluff, the species 

which Stewart probably had before him fron1 Thomasville. Olsson's figures suggest a less inflated form than 

the con1mon Bashi species. The rib count runs lower 

in the Peruvian negritensis than it does in V. bashiplata, 

but the character of the ribs is apparently the same in 

both. Venericardia regia, which Woods suggested as a 

possible analog, is now restricted to the heayy trigonal 

species from the Aquia formation of Mar:;land and 

Virginia, a species characterized in the early stages by 

crested ribbing.49 

48 Woods, Henry, op. cit., pl. 4, fig. 1. 

4g A very fine suite of Peruvian vimericards has been described by Henry Woods 

and by Olsson, and although we have very little comparative material from the 

Peruvian Eocene, it is tempting to speculate upon the possible anruogies with the 

Gulf species. Olsson (Olsson, A. A., Contributions to the Tertiary paleontology or 

northern Peru, pt. 1; Bull. Am. Paleontology, vol. 14, no. 52, p. 9, 1Y?S) suggests the 

following correlation for the Eocene of northern Peru: 

American time Formations Bosworth's divisions subdivisions 

Saman formation ... 

Upper. Talara formation." Lobitos formation. 

Restin} Parinas group. Parinas 

Middle. Clavilithes 

Negritos series. 

Pale Greda} formation. 

Salina group. Salina 

Lower. Negritos. Turritella series. 

toward the ventral margins. On the umbos the ribs are· .. Olsson, A. A., Contributions to the Tertiary paleontology of nortl em Peru, pt. 3; 

high and narrower than the deep, groovelike interspaces, but Bull. Am. Paleontology, vol. 17, no. 62, pp. 5-18' 1930. 

they broaden rapidly and near the ventral margin flatten and A rew of the planicostate forms have been introduced for possible comparison with 

become 5 or 6 times the width of the shallow but distinct inter- East American species. 
SYSTEMATIC DESCRIPTIONS 171 

.Venericardia (Venericor) bashiplata Gardner and Bowles, n. sp. 

Plate 33, figure 9; plate 34, figures 3-6 

1897. Venericardia planicosta (of authors). Harris, Bull. Am. 

Paleontology, vol. 2, no. 9, pl. 10, fig. 5. 

1917. Venericardia planicosta var. 5 [error foro], Harris. Waring, 

California Acad. Sci. Proc., 4th ser., vol. 7, no. 4, p. 54. 

1930. Venericardia planicosta (of authors). Stewart, Acad. Nat. 

Sci. Philadelphia Special Pub. 3, pp. 157, 161. 

Shell moderately large and heavy, cordate-trigonal, 

truncate posteriorly, the umbones prominent and inflated, the tips incurved and turned slightly forward. 

Lunule sharply delimited, wider in the right valve than 

in the left. Ligament area prominent but no defined 

escutcheon. Ribs coarse, simple, serrated by the incrementals at the extreme tips, persistent anteriorly 

and medially to the ventral margin; 19 in number exclusive of the posterior area; posterior cording close 

and even near the umbones, dying out away from the 

umbones and obscured towa.rd the ventral margin by 

the overriding incrementals; cords 8 in the right va.lve 

of the type, 6 in the left, distinct from the angular 

1ibs upon the disk. Hinge plate moderately high and 

broad, the medial right cardinal scimitar-shaped. 

Interior thickened over the area of the adherent 

mantle. Muscle scars unusually large. Pallial line 

rather distant from the margin. Inner ventral and 

anterior margins coarsely crenate. 

Dimensions of cotypes: Right valve, height 77.2 

millimeters, width 75.2 Jnillimeters, convexity 27.0 

millimeters. Left valve, height 75.8 millimeters, width 

71.5 millimeters, convexity 27.0 millimeters. 

Cotypes, a right and a left valve of different individuals: U. S. National Museum, no. 371914. 

Type locality: Geological Survey station 7153, Choctaw Corners, Clarke County, Ala. Wilcox group, Bashi 

formation. 

Venericardia bash~plata includes the coarsely ribbed, 

moderately large and inflated individuals, in tile probable line of media plata and nanaplata. It is decidedly 

larger than its probable ancestors, and the ribbing is 

more angular and more vigorous than in the majority 

of the nanaplata. The n1ore inflat~d of the nanaplata 

have a similar sculpture, but they do not approach 

bashiplata in weight and dimensions. 

An abnormal left valve of this species was noted at 

locality 7153. (See discussion on pages 163-165.) It is 

recorded as U. S. National Museum no. 371914. 

Distribution: 

Wilcox group, Bashi formation: 

Alabama, Dale County, 110936 , Hillside at swimming pool, near A. C. L. R. R. station, Ozark. 

Coffee County, 10781P, Pea River at Churchwell's 

Bridge, NE}{ sec. 12, T. 4 N., R. 19 E. Clarke 

County, 10770c, roadside and corner SE}{ sec. 4, 

T. 11 N., R. 21 E., 1.6 miles south of Bashi; 3100c, 

beds at Woods Bluff, near Choctaw Corners and 

Thomasville; 7153°, headwaters of Beaver Creek 

about a quarter of a mile east of Choctaw Corners 

(lower bed); 7155c, gully near middle of sec. 7, T. 

11 N., R. 3 E., about 3 miles west of Cho~taw 

Corners; 262a, 3099a, 5470a, Woods Bluff, ':':'omhigbee River. 

Mississippi, Lauderdale County, 2134°, McLemare's 

Hill, near Meridiar; 10055P, southeast outskirts of 

Meridian; cut on M. & M. R. R. near overhead 

0rossing of M. & 0. R. R.; 7267P, cut on I•C & 

M. R. R. 300 yards south of Seymour's Hill and 

1~ miles south of Meridian (fossils from lower 12 

inches of basal yellow sand); 2105P, McKay's marl 

bed, Souwashee Creek, 2 miles south of Meridian. 

Texas, Sabine County, 5120P, 200 yards below Sabinetown Ferry; 10728P, a quarter of a mile downst:~~am 

from Sabinetown Ferry. 

Venericardia (Venericor) ascia Rogers 

Plate 35; figures 3-7 

1839. Venericardia ascia Rogers, H. D., and W. B., Am. PI i.los. 

Soc. Trans., vol. 6, pp. 374-375, pl. 29, fig. 2. 

1848. Venericardia ascia Rogers. Lea, H. C., Acad. Nat. Sci. 

Philadelphia Proc., vol. 4, p. 107. 

1848. Venericardia ascia Rogers. Lea, Henry, Catalog of Tertiary Testacea, p. 15. 

1865. Venericardia ascia Rogers. Conrad, Am. Jour. Con~hology, vol. 1, p. 7. 

1884. Venericardia ascia Rogers. Rogers, H. D., and Ro~ers, 

W. B., Geology of the Virginias, p. 671, pl. 4, fig.~. 

1891. Venericardia ascia Rogers. Heilprin, Acad. Nat. Sci. 

Philadelphia Proc. for 1890, p. 402. 

1896. Venericardia ascia Rogers. Harris, Bull. Am. Paleo"l.tology, vol. 1, no. 4, p. 58. 

1896. Venericardia ascia Rogers. Clark, U.S. Geol. Survey Bull. 

141, p. 80. 

1901. Venericardia ascia Rogers. Clark and Martin, Maryland 

Geol. Survey, Eocene, p. 177. 

1901. Venericardia marylandica Clark and Martin, Maryland 

Geol. Survey, Eocene, p. 179, pl. 40, figs. 7, 7a. 

1903. Venericardia ascia Rogers. Dall, Wagner Free Inst. Sci. 

Trans., vol. 3, no. 6, pp. 1419, 1422. 

1903. Venericardia marylandica Clark and Martin. Dall, Wr.gner 

Free Inst. Sci. Trans., vol. 3, no. 6, pp. 1419, 1423. 

1917. Venericardia marylandica Harris. Waring, California 

Acad. Sci. Proc., 4th ser., vol. 7, no. 4, p. 54. 

1922. Venericardia ascia Rogers. Woods, Geology of northwest 

Peru, p. 69. 

1922. Venericardia marylandica Clark and Martin. Woods, 

Geology of northwest Peru, p. 69. 

1930. Venericardia ascia Rogers. Stewart, Acad. Nat. Sci. 

Philadelphia Special Pub. 3, pp. 163, 164. 

1930. Venericardia marylandica Clark and Martin. Stewart, 

Acad. Nat. Sci. ·Philadelphia Special Pub. 3, p. 151. 

1936. Venericardia ascia Rogers. Rutsch, Eclogae geol. Helvetiae, vol. 29, p. 164. 

Shell subovate, subcordate, not thick; costae much deprAssed 

except on the beak, about 30; transverse striae numerous from 

the margin to the umbones, nearly obliterating some of the 

longitudinal sulci; lunule profound, subcordate, triangular and 

equilateral; anterior muscular impressiol} rather remote from 

the hinge; cardinal teeth arcuated, oblique; inferior and posterior 

margins crenulated. Length 3.2 inches, breadth 3.6 inch':\s. 

Locality, King George County, Virginia, near the Potomr~, in 

the Eocene. 

Remarks.-This shell can be confounded only with tha. V. 

planicosta, to which it is possible we ought to refer it as a variety. 

They are readily distinguished, however, by the greater length 
172 THE VENER1CARD1A i>tANICOSTA GROUP IN THE GUtF PR6VlNCE 

and curvature of the whole anterior margin, especially the portion 

along the ligament; the hinge is broader and longer, and the 

teeth are less prominent and more arcuated; the muscular 

impression, on the anterior side, is farther from the hinge; and 

the whole valve is wider, flatter, and thinner. These differences, 

with the flatness of the costae, appear to warrant us in regarding 

this shell as a distinct species from Venericardia planicosta. 

That shell also is found in the Eocene of Virginia, but usually 

not in the same bed with V. ascia.-H. D. and W. B. Rogers, 

1839. 

The Venericardia planicosta of the Rogerses was 

almost certainly V. regia, which occurs in the Eocene 

of Virginia but at a lower horizon than ascia. 

Sixty-two years later Clark and Martin described 

from an equivalent horizon in Maryland a species 

which they called V. marylandica but which probably 

is specifically identical with V. ascia. 

Shell thin; outline rircular; valves shallow; about 27 ribs, 

broad and flat on top, with deep, narrow interspaces near the 

beaks, but very flat, and separated by narrow, impressed line 

toward the periphery. 

This species resembles very closely in outline V. pectuncularis 

from the Paris Basin. It is restricted to the Woodstock substage. 

Length 80 millimeters, width 80 millimeters-Clark and 

Martin, 1901. 

Collections from the Nanjemoy formation both in 

~faryland and in Virginia reveal only the one species 

of simple-ribbed, subcircular to subovate venericard. 

The Maryland and Virginia forms have in common a 

broad hinge plate, shallow valves with only feebly 

inflated umbones and about 27 or 28 simple flat-topped 

ribs that remain distinct to the ventral margin and are 

separated by rather wide interspaces. There is no 

evidence in the material at hand to indicate that more 

than one species is involved. Venericardia potapacoensis, the only other member of the group that is coexistent with ascia, is a lop-sided, very high deltoid or 

subcordate little species with less than 25 ribs, which 

are strongly noded in the early growth stages and 

evanesce in the later. 

Distribution: 

Wilcox group, Nanjemoy formation: 

Maryland, Charles County, 12541P, bluff on Potomac 

River, 1 mile below Popes Creek; (Maryland 

Geological Survey), 2 and 2Yz milE's above Popes 

Creek. 

Virginia, King George County (Maryland Geological 

Survey), Woodstock. County unknown, 1453P, 

Pamunkey River. 

Venericardia (Venericor) hatcheplata Gardner and B.owles, n. sp. 

Plate 33, figures 8, 12; plate 34, figures 1, 2 

1886. Venericardia planicosta Lamarck. Aldrich, :Alabama Geol. 

Survey Bull. 1, pt. 2, p. 50 [name only]. 

1897. Venericardia planicosta var. o Harris [part], Bull. Am. 

Paleontology, voJ. 2, no. 9, p. 55 [figures excluded]. 

1903. Venericardia planicosta var. laticardo Wood. Dall, Wagner Free Inst. Sci. Trans., vol. 3, pt. 6, p. 1422. Not 

Venericardia planicosta var. laticardo Wood, Monograph of the Eocene bivalves of England, vol. 1, p. 150, 

pl. 21, fig. 5d. 1871. 

1903. Venericardia planicosta form o Harris [part]. Dall, Wagne::t: 

Free Inst. Sci. Trans., vol. 3, pt. 6, p. 142~. 

1926. Venericardia planicosta Lamarck. Cooke, Alr.bama Geol. 

Survey Special Rept. 14, pl. 94, fig. 7. (Specimen 

figured from Hatchetigbee and not from Nanafalia.) 

1930. "Venericardia planicosta form o Harris [part]. Stewart, 

Acad. Nat. Sci. Philadelphia Special Pub. 3, p. 156. 

Shell not very large relatively but hea'Ty, rather 

compressed, high cordate with well-roundec margins' 

and remarkable for its senile aspect both in tlo. external 

and the internal views. Umbones very high but not 

strongly inflated, inclined forward. Lunule unusually 

deep and n10derately wide, the shell of the adults 

flattened in front and sunulating an outer lunular area. 

Ligan1ent area very prominent, but no define':l escutcheon. Posterior area indicated by a chan-;e in the 

character of the radial sculpture. Ribs r.~rlged and 

crenate in the un1bonal region, low and broad away from 

the umbones and separated by only lino.ar interradials, evanescent toward the ventral and lateral 

margins. Ribs in the double paratype, 23 upon the 

medial and anterior areas, 8 upon the posterior; in the 

single right cotype, 22 upon the medial and anterior 

areas; 8 upon the posterior; in the single left co type, 22 

upon the medial and anterior areas, 8 upon the posterior. Posterior ribs more cordlike and not so high as 

those upon the disk but by no means sharply distinct 

from them. Growth lines conspicuous toward the 

outer margins. Ligament attachment adjusted to an 

unusually heavy ligament. Hinge plate very high, 

trigonal. Dentition unusually heavy, and tl~ teeth so 

closely locked that in only about 1 out of every 10 could 

the valves be forced apart without breaking the hinge. 

Pedal scar deeply impressed. .Adductor sc".rs rather 

narrow but sunken. Pallial line ragged. Interior 

thickened over the area of the adherent mantle. 

Inner margins feebly crenate. 

Dimensions of cotypes: Right valve, height 70.0 

Inillimeters, width 68.0 millimeters. Left valve, height 

73.0 millimeters, width 69.5 millimeters. 

Cotypes, a right and a left valve of different individuals and a paratype, a locked pair of valves: U.S. 

National Museun1, no. 372173. 

Type locality: Geological Survey station 261, Hatchetigbee Bluff, Tombigbee River, Washington County, 

Ala. Wilcox group, Hatchetigbee formation. 

Venericardia hatcheplata is remarkable for the high, 

rather compressed valves with rounded outFnes, worn 

and not very prominent ribbing, which tend~ to become 

obsolete in the adult and gives to the shell a senile look, 

the very high deltoid hinge plates, the strong, closely 

interlocked teeth, and the very distinct scars r.nd ragged 

pallial line. The species is probably in line with 

V. nanaplata and V. bashiplata. It is not so inflated 

as its Bashi progenitor; the ribs are not so strong but 

more numerous and much more inclined to become 

obsolete ventrally. The hinge plate is higher and not 

so wide, the scars are not so large but more distinct, 
SYSTEMATIC DESCRIPTIONS 173 

and the pallial line is nearer the margin. The species 

is exceedingly common in the early collections from 

Hatchetigbee Bluff and is restricted to the Hatchetigbee 

formation of the Wilcox group. 

Distribution: 

Wilcox group, Hatchetigbee formation: 

Georgia, Stewart County, 12097P, 1}i miles northeast 

of Troutman, spring west of Georgia, Florida & 

Alabama Railroad, fossils from weathered yellow 

clay about 5 feet above level of spring. 

Alabama, Washington County, 547P, 261Pr, and 

5873Pr, Hatchetigbee Bluff, Tombigbee River; 

10768P, roadside half a mile west of Butler. 

Venericardia (Venericor) claiboplata Gardner and Bowles, n. sp. 

Plate 36, figures 1-4 

1919. Venericardia planicosta Lamarck form o [part]. Harris, 

Bull. Am. Paleontology, vol. 6, no. 31, p. 77, pl. 27, 

figs. 5 and 6, pl. 28, figs. 1 and 2. 

1936. Vener·icardia claiboplata Gardner and Bowles, nude name. 

Cooke, U. S. Geol. Survey Bull. 867, pp. 61, 62, 63, 64. 

Shell moderately large and solid, high trigonoeordate 

with broadly rounded margins and elevated, broadly 

inflated umbones, the tips ineurved over the deeply 

sunken lunule. Posterior area defined by the change 

in sculpture rather than by the contouring of the valve. 

Ribs elevated, ridged and serrate near the tips of the 

umbones, high and angular away from the umbones, 

flattening and tending to becon1e obsolete near the 

ventrr~l margin, 24 upon the anterior and medial portion 

of the cotypes, 6 upon the posterior area of each. Hinge 

area high, dentition heavy; cardinals produced, the 

posterior cardinal of each valve following the curve of 

the dorsal margin; middle right cardinal flattened, 

arcuate-cuneate. Pedal scar deeply inset; adductor 

sears large, distinct. Pallial line distinct but not 

conspicuous, rather close to the ventral margin. 

Dimensions of cotypes: Right valve, height 73.0millimeters, width 70.0 millimeters, convexity 26.0 millimeters. Left valve, height 73.0 millimeters, width 

72.0 millimeters, convexity 26.5 millimeters. 

Cotypes, a right and a left valve of different individuals: Right valve, U. S. National 1-fuseum, no. 11365; 

left valve, U.S. National 1-fuseum, no. 1434. 

Type locality: (U. S. N. M. 11365) Claiborne, 

Monroe County, Alabama. (U. S. N. M. 1434) 

Clarksville, Clarke County, Ala. 

Venerica.rdia claiboplata is elosely allied to its probable 

ancestors. From V. ha.tcheplata it n1ay be separated by 

the more convex outline, the lower average rib count, 

and the relatively smaller, lower hinge plate. 

The rib count upon the anteromedial portion is 

higher by four or five than upon v·. ba8hiplata, and the 

umbones are higher. and more inrolled. The dentition 

is, however, very similar in the Bashi and the Claiborne 

forms. V. claiboplata differs from Venericardia den8ata 

Conrad in the less sharply beaded umbonal riblets, 

the narrower anterior ribs, and the lesser tendency 

20412-39-3 

toward the undercutting of the ribs away from the 

umbones. V. den8ata is appreciably smaller in the 

adult state. The two species have the same ger~ral 

distribution, but V. claiboplata is less common and not 

so widespread. In Texas it is most commonly rrnresented in the Weches greensand member of the Mount 

Selman formation in Anderson and Houston Counties. 

Specimens from southeastern Atasco-;a County near 

Leming, Tex., from concretionary beds probably of 

Reklaw age, indicate a common species closely related 

and possibly specifically identical with claiboplata. 

The shells are preserved in the form of n1olds only and 

are apparently all imn1ature. The large inflated species 

occurring near Magnolia Crossing on the Trinity River 

in southern Anderson County is not V. claiboplata but 

probably a new species more closely allied to some of 

the Mexican forms. Associated with it are roundish, · 

rather heavy venericards linearly grooved somevrhat 

after the manner of sOine of the variants of 17. diga.. 

If the Magnolia Crossing outcrop is lower Claibc~ne, 

it is extremely difficult to understand why in the rridst 

of a fossiliferous lowerClaibornesequenceitshouldcr,rry, 

without apparent lithologic change, a fauna so dis6nct. 

Distribution: 

Claiborne group, McBean formation: 

South Carolina, Lexington County, 7731 P, 7 miles 

east of Swansea. Orangeburg County, 7724P, 

Bull Swamp Road east of Limestone Creek. 6% 

miles northwest of Orangeburg Court House; 

4579c, 4580c, Bull Swamp road, 5.1 miles northwest 

of Orangeburg Court House; 2012e, Pooser's Hill, 

5 miles northwest of Orangeburg Court House; 

2013c, Cawcaw Swamp, 4~~ miles northweE't of 

Orangeburg Court House; 2011P, Cawcaw Swr.mp, 

3% miles northwest of Orangeburg Court House; 

7723P, Bull Swamp road east of Cawcaw Swamp, 

2% miles northwest of Orangeburg Court House; 

2009P, Cawcaw Swamp, 2 miles west of Orangeburg Court House; 7992P, 4 miles east of Springfield. 

Claiborne group, Lisbon formation: 

A1abama, Monroe County, 2396c, 31Q5c, Li,"1bon 

Bluff, 1 mile below Lisbon Landing, Alabama 

River. Clarke County, 278P, Coffeeville; ?Clr.rksvilleP. 

Claiborne group, Mount Selman formation, Re:ti:law 

member: 

Texas, Gonzalez County, 12468?r, half a mile b~low 

Willow Springs ra~ch house on Capote Hills road. 

Claiborne group, Mount Selman formation, W€.ches 

greensand member: 

Texas, Anderson County, 9968r, half a mile wec<t of 

Palestine; 2054r, Colgins Hill, 1 mile sout'-1 of 

Palestine; 9265 P, 1 mile south of Elkhart. H ouston County, 9255P, 9258P, Percilla. Leon County, 

13058P, half a mile east of Robins on the Centerville road. Bastrop County, 5284P, near the 

county line in the southernmost part of the county. 

Claiborne group, Cook Mountain formation: 

Louisiana, Bienville Parish, 2911P, near Mount 

Lebanon. 

Texas, Houston County, 10735r, Trinity River, 

Alabama Crossing, bed no. 1. 
174 1.'HE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

Claiborne group, Gosport sand: 

Alabama, Monroe County, 263P, 2391P, 2867P, 

13044P, 13086P, Claiborne Bluff, Alabama River. 

Covington County, 1010r, Conecuh River, 3 miles 

west of Andalusia; 6737r, Sepulga River, 6}~ miles 

north of Brooklyn. 

Venericardia (Venericor) cacamai Gardner and Bowles, n. sp. 

Plate 37, figures 4, 5, 8, 11 

Shell large and heavy, inflated, eordate. Umbones 

full and prominent, twisted forward over the narrow 

but rather high lunule. Posterior region clearly differentiated not only by the obtuse flattening of the shell 

but also by a marked ehange in the ribs, wbieh beeon1e 

narrow and closely spaeed with linear intercostals and 

overridden by the inerementals, which cut sharply into 

them, obscuring their outline. Sculpture on the extreme tips not preserved in the cotypes, but costals 

sharply noded near the tips, flat and simple on the disk 

and separated by narrower U-shaped intercostals; 

traces of lateral threading preserved in the adolescent 

stage of the shell, but preservation too poor to determine its importance; ribs relatively narrow and eordlike anteriorly, 23 on the anteromedial portion, 7 on the 

posterior. Ligament marginal, supported on prominent 

nymphae. Hinge very high and heavy. Right anterior eardinal alnwst vertical; the middle eardinal 

heavy, deltoid, arched obliquely forward toward the 

tips; posterior cardinal produced parallel to the ligament groove; left anterior and posterior cardinals high, 

rather heavy and bent slightly forward toward the tips 

of the umbones. Characters of the rest of the interior 

concealed by the matri~, but the adduetor and pedal 

scars probably deep and large to function adequately 

in so heavy a shell. 

Dimensions of cotype: Left valve, height (estimated) 

7 5.0 millimeters. 

Cotypes, an incomplete right and left valve of 

different individuals: U.S. National Museun1, no. 373032. 

Type loeality: Geological Survey station 13142, on 

the west side of the Lorna Guajardo road to Dr. Coss, 

Zacate, Nuevo Le6n, Mexico. 

"Venericardia cacamai is the heavy-shelled and heavyhinged venericard most widely distributed in the upper 

part of the Cook Mountain of northern Mexico. It 

oecupies in the faunas above the Arroyo Chacon 

assemblage the same position which 1/'enericardia densata occupies in the faunas carrying Ostrea sellaejorm1~s. 

F. cacamai is a more n1assive shell than V. densata, 

and the average dimensions and the rib eount are 

higher than in V. claiboplata or V. zapata1~. 

The species has not been reeognizcd on the Texas side, 

but in northern Mexieo it is sufficiently common to be 

of stratigraphic value. . 

Venericardia (Venericor) restinensis Olsson 

Plate 37, figure 6 

1928. Venericardia planicosta var. restinensis Olsson, Bull. Am. 

Paleontology, vol. 14, no. 52, p. 27, pl. 6, fig. 2. 

1930. Venericardia planicosta restinensis Olsson. Stevrart, A cad. 

Nat. Sci. Philadelphia Special Pub. 3, p. 172. 

1936. lTenericardia restinensis Olsson. Rutsch, Ec1 ogae geol. 

Helvetiae, vol. 29, p. 172. 

During the Restin or the upper middle Eocene the conditions 

for the growth and evolution of this series of Venericardia do not 

appear to have been specially favorable, and the shells are generally small, rarely exceeding 50 millimeters in length. They 

vary from well-rounded to subquadrate in form, strongly convex, 

with heavy ribs extending over two-thirds of the surface, becoming obsolete or fading over the central portion. The ribs number about 17 to the umbonal angle, with 5 or 6 additional ones on 

the dorsal-posterior submargins. The umbos are full, convex, 

with small, curved beaks and small, deeply sunk lunule. The 

posterior submargin is somewhat ridged' in the middle., bordered . 

with a depressed or concave zone on the outer side. 

An interesting Venericardia, probably belonging to the planicardia [planicosta] stock, was described by Grzybm1rski as V. 

clavidens, and he lists the fossils both from Zorritas and Rica 

Playa. From Grzybowski's Zorritas records one would pre~ume 

the fossil to be of Miocene age, but the species is not mentioned 

by Spieker in his studies on the Zorritas fauna, nor have any 

specimens been found in the course of our own extensive collecting in the Miocene rocks of northern Peru. It is therefore most 

probable that Grzybowski's specimens were collected only at 

Rica Playa, where Miocene beds are found overlapp;ng on the 

upper Restin and lower Saman Eocene. V. clavidens resembles 

variety restinensis by its small size and in sculpture but differs 

by its strongly pointed posterior extremity and by its liinge. 

The hinge of clavidens shows in the right valve a s•uall tooth 

rising from the posterior end of the nymphs. In this feature 

clavidens shows an approach to samanensis, occupyin'! an intermediate position between that variety and restinensis: which its 

stratigraphic position at Rica Playa would also indicate. 

Localities and geologic occurrence.-Restin formation 1 Negritos, 

Pozo Valley near Lagunitas and Lower Verdun, Jabonillal, 

Restin.-Olsson, 1928. 

Olsson figured only the exteriors of his venericards. 

Unless the species shows some striking individuality 

externally, which this one does not, comparison~ without 

comparative material are of little value. 

POSITION UNCERTAIN 

V enericardia gulielml Gardner and Bowles, n. name 

Plate 42, figure 4 

1903. Venericardia simplex Dall, Wagner Free Inst. E'ei. Trans., 

vol. 3, pt. 6, p. 1426, pl. 56, fig. 12 [not V. simplex 

Wood, 1864]. 

Shell inequilateral, broad ovate, with small, rather low beaks; 

anterior end short, rounded, posterior longer, arcuate dorsally, 

broadly rounded behind; base gently arcuate; sculpture of about 

25 simple, low, subequal ribs, separated by wider, sbl.llow, unchanneled interspaces; lunule small, impressed; hinge normal, 

basal margin internally fluted. Length 17.5, height 14.0, 

diameter 9.0 millimeters. 

Chickasawan (or Lignitic) Eocene of Woods Bluff, Clarke 

County, Ala., Frank Burns. 

At first glance this species recalls a very much worn young 

alticostata, but an examination shows the surface to be intact and 

the sculpture naturally as described.-Dall, 1903. 

Holotype, a left valve: U. S. National MuF~um, no. 

154725. 

Type locality: Geological Survey station 3101, Woods 

Bluff, Clarke County, Ala. Wilcox group, Bashi 

formation. 
SYS'l:EMATIC DESCRIPTIONS 175 

Dall described this species originally under the name 

V. simplex, a name preoccupied by Wood's species fron1 

the British Tertiary described in 1864. The type of 

the species, a left valve, is unique, and the affinities are 

doubtful. 

The cardinals, particularly the anterior, are remarkably slender and laminar. 

Distribution: 

Wilcox group, Bashi formation: 

Alabama, Clarke County, 3100 r, Woods Bluff, 

Tombigbee River. 

Section LEUROACTIS Stewart 

1930. Stewart. Gabb's California Cretaceous and Tertiary 

type lamellibranchs: Acad. Nat. Sci. Philadelphia 

SpeciaJ Pub. 3, p. 154, 158-160. 

Type by original designation: Venericardia pilsbryi Stewart, 

lower Wilcox (Nanafalia and Tuscahoma formations) 

of Alabama. 

An apparently new species is described from Yellow Bluff 

(Wilcox) which is believed to be rdated to V. horatiana rather 

than to V. planicosta, and these two species are given a new 

section name Leuroactis.-Stewart, p. 154, 1930. 

The short straight right cardinal of V. pilsbryi resembles the 

corresponding tooth in the hinge of V. horatiana, and the species 

seem more closely related to that species than to V. planicosta 

and its allies. In V. planicosta the right cardinal curves anterodorsally. The difference is best shown in immature specimens 

(25 to 50 millimeters in length), ar'd there also the resemblance 

to V. horatiana may be seen. While this difference is not very great 

it indicates that V. pilsbryi is off the main stem of V. planicosta. 

The new section name Leuroactis is here proposed, with V. pilsbryi as type species. V. horatiana and its Pacific relative V. 

aragonia are placed in this section because they have the straight 

right cardinal. While all the adult specimens of V. pilsbryi 

have the straight cardinal, the character is not so well marked 

on some of the large specimens of V. horatiana particularly when 

compared to the hinge of large specimens of V. regia, which appears to belong with V. planicosta in Venericor. V. pilsbryi has 

the most unique hinge, while that of V. horatiana approaches the 

hinge of Venericor.-Stewart, p. 160, 1930. 

Venericardia (Venericor) pilsbryi Stewart 

Plate 38, figures 9,·10 

1930. Venericardia pilsbryi Stewart, Acad. Nat. Sci. Philadelphia, 

Special Pub. 3, pp. 158-160, pl. 9, figs. 4, 5; pl. 10, figs. 

1, 2. 

1936. Venericardia pilsbryi Stewart. Rutsch, Eclogae geol. 

Helvetiae, vol. 29, p. 164. 

Shell large, heavy, rather flat, with prominent umbo, wellrounded anterior end and the posterior end produced ventrally; 

ventral margin almost straight; 38 close-set radiating ribs, those 

over the central portion being smooth and flat, while those on 

the dorsal slopes are slightly rounded and crossed by prominent 

growth lines; lunule wide and deep, escutcheon not defined; internal callus heavy and the ventral and anterior margins coarsely 

crenulated internally; the prominent cardinal tooth in the right 

valve straighter and shorter than is usual for this genus. Length 

103 millimeters, height 93 millimeters, thickness of right valve 

32 millimeters; type no. 12510 * * *. 

Horizon, Eocene, Lignitic-Sabine-Wilcox; locality, Yellow 

Bluff, on the Alabama River * * *· 

This species occurs with V. planicosta and V. regia in the lower 

Wilcox of Alabama, and in contrast to the abundance of those 

species, only 28 specimens have been recognized. The number 

of ribs varies from 32 to 38, a plurality (6) having 35 ribs. The 

species may be easily recognized by its smooth, flat central ribs 

and linear interspaces * * *. 

The short, straight light cardinal of V. pilsbryi resembles the 

corresponding tooth in the hinge of V. horatiana, and the srecies 

seems more closely related to that species tht,tn to V. plam:costa 

and its allies. In V. planicosta, the right cardinal curves anterodorsally. The difference is best shown in immature specimens 

(25 to 50 millimeters in length), and there also the resemb1,q,nce 

to V. horatiana may be seen. While this difference is not very 

great, it indicates that V. pilsbryi is off the main stem of V. 

planicosta. * * *.-Stewart, 1930. 

Venericardia pilsbryi does not seem to bear any close 

relationship to the other lower Wilcox forms, Apparently it arose from some ancestor common with the 

mediaplata stock but probably left the main strain 

prior to Midway time. It is found in both the Nanafalia and the Tuscahoma, but no descendants of the 

stock are encountered throughout the upper Wihox. 

In the Claiborne two possible descendants have l~~en 

recognized-V. ang·ustoscrobis n. sp. from the LiFhon 

forn1ation in Alabama, and V. claz:iger n. sp., from the 

South Carolina and Alabama undifferentiated Claiborne. V. cookei n. sp., fron1 the Jackson of Alabanla, is a very similar type and is probably the culmination of the race. 

Distribution: 

Wilcox group, Nanafalia formation: 

Alabama, Marengo County, 271~>, Nanafalia Landing, 

Tombigbee River. 

Wilcox group, Tuscahoma san<;i: 

Alabama, Wilcox County, Acad. Nat. Sci. Philadelphia no. 12510, Yellow Bluff, Alabama Wver; 

· 10779r, descent to Lower Peachtree Ferry, Alabama River. Monroe County, 3118r, Greggs 

Landing (lower bed), Alabama River. 

Venericardia (Venericor) angustoscrobis Gardner and Bo~les, 

n. sp. 

Plate 38, figures 4, 7 

Shell small, solid, inflated, ovate-trigonal in outline. 

Umbo low, not prominent. Lunule relatively vride 

and shallow. Anterior margin broadly rounded, posterior n1argin obscurely truncate and slightly produced 

ventrally. Umbonal ribs relatively wide, separr.ted 

by deep, narrow intercostals and bearing prominent 

serrations. Ribs 32, wide, flat-topped, and separr.ted 

by deeply incised, narrow intercostals; 8 of these on 

the posterior region, 24 on the anteromedial, co~plete 

and distinct to the ventral margin. Nymph narrow 

and not prominent. Hinge plate low and rather wide; 

median cardinal of right valve asymmetrically trigonal. 

Adductor scars small and not deeply incised. Pallial 

line simple, indistinct, and close to the ventral margin. 

Inner ventral margin crenulate. 

Dimensions of holotype: Height 30.0 millin1eters, 

width 32.5 millimeters, convexity 12.0 millimeters. 

Holotype, a right valve: U. S. National Muse'lnl, 

no. 372691. 

Type locality: Geological Survey station 13060, 

Lisbon Bluff, Monroe County, Ala. Claiborne group, 

Lisbon formation. 
176 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

The holotype was collected by Dr. Earl Turner, who 

generously presented it to the United States Geologieal 

Survey. 

Venericardia angustoscrobis is known only fron1 the 

type, which is probably not fully adult. A doubt.ful 

right valve (pl. 38, figs. 3, 8), which presents some 

characters of extren1e old age, is possibly related to this 

species and probably from the Gosport sand. The 

young form suggests, in the eompact outline and fine, 

crowded, but very regular ribbing, Venericard'l·a cookei 

fron1 the Jackson. The Jackson species differs superficially in the more transversely ovate outline and the 

higher rib eount and fundamentally in the trigonal 

right n1iddle cardinal, in which the posterior leg is 

longer than the anterior, but both margins are straight 

as in r. pilsbryi, while in ang·ustoscrob·is the right 

n1iddle eardinal is cuneifol'ln and bent forward near 

the un1bones. The hinge of the gerontic right valve 

questionably allied to ·v. angustoscrobis is very 

similar to that of l·'. densata but the costals are more 

numerous and less ornamented. 

Distribution: 

Claiborne group, Lisbon formation: 

Alabama, Monroe County. 13060•, Lisbon Bluff, 

Alabama River. 

Claiborne group, Gosport sand: 

Alabama, Monroe County, ?Claiborne Bluff•, Alabama River (F. E. Turner). 

Venericardia (Venericor) cookei Gardner and Bowles, n. sp. 

Plate 38, figures 5, 6 

Shell small, con1paet, inflated, ovate-trigonal; the 

anterior lateral n1argin Inerging smoothly into the upeurved base, the posterior obscurely truncate. Un1-

' bones broad, low, with inconspicuous tips turned 

inward and forward. Lunule wide and not at all deepset. Posterior area indieated by a flattening of the 

shell and by the nwre narrow, eordlike costals and 

stronger incrmnental wrinkling. Radial sculpture 

close and crowded over the entire shell, the costals, 

39 in all, 30 on the anteromedial portion, 9 on the posterior; sharply noded in the early growth stages, low, 

flat, and simple in the later and separated by deeply 

ineised linear intereostals, which remain distinct to the 

ventral n1argin. Ligament n1arginal, deeply inset, the 

nynrph narrow but expanded slightly toward the 

. un1bones. Hinge plate low but rather broad. Anterior 

right cardinal very short; the middle right cardinal 

an asyn1metric triangle with the posterior dorsal margin 

straight and not bent forward as in the great n1ajority 

of-. the group; posterior right eardinal a slender lan1ina 

produced beyond the extren1ity of the ligan1ent nymph; 

anterior left cardinal short, the posteri9r more produced 

and slightly expanded ventrally. Interior thickened 

slight.ly over the area of the adherent mantle. Pedal 

scar a deep dent at the dorsal extremity of the anterior 

adductor. Adduetor sears very large for the size and 

weight of the shell, sunken, and distinct. Fallial line 

rather far ren1ovecl fron1 the ventral margin. Inner 

n1argins sharply erenate from the lunule to the ligament 

groove. 

Din1ensions of holotype: Height 38.0 n1illin1eters, 

width 41.5 millinwters, eonvexity 15.2 n1illir~eters. 

Holotype, a right valve: U. S. National Museum, 

no. 129767. 

Type locality: Geological Survey station 269, Catons 

Bluff, Conecuh River, Covington County, Ala. Rocks 

of Jackson age. 

"'{.Tenerica·rdia cookei is the last known descendant of 

the pilsbry'l: stock. From Venericardia ang·ustoscrobis 

of the Lisbon fauna, it is separated by the more ovate 

outline, the slightly higher and less anterior umbones, 

the laek of curvature in the middle right eariinal, and 

the ribs nwre numerous by 5 or 6. 

The species is known only from the typo, locality. 

It is named in honor of C. Wythe Cooke, who has so 

generously shared with us his intimate knowledge of the 

upper Eoeene of the Gulf. 

Distribution: 

Rocks of Jackson age: 

Alabama, Covington County, 269", Catons Bluff, 

Conecuh River. 

Venericardia (Venericor?) claviger Gardner and BCJ'~les, n. sp. 

Plate 38, figures 1, 2 

1936. renerica1·d·£a claviger Gardner and Howles, nude name. 

Cooke,U. S. Geol. Survey Bull. 867, p. 58. 

Shell moderately large and heavy; roundei ovate to 

trigonal with broadly arcuate anterior and ventral 

margins and obtusely truncate posterio:" margin. 

Umbo inflated; prosogyrate. Lunule narrow and deep. 

Posterior area defined by the truncation of the posterior 

extremity and by the costae, which becon1e rfl.rrow and 

elose-set, and wrinkled by many fine, coneentric ineremental striae. Umbonal seulpture eonsisting of narrow, high Iibs, serrate on the extreme umbonal tips, 

partieularly on the more anterior eostae. Adult sculpture eonsisting of 27 wide, gently arched costae, 21 on 

the an teromedial portion of the disk and 6 on the posterior area, separated by deeply ineised intercostals 

which are little n1ore than narrow lines but which 

remain distinct and eomplete to the ventral n1argin. 

Hinge platA very sn1all; the teeth coarse and concentrated; median cardinal tooth of right valve peglike, 

extremely high and heavy, although very short, forming a trigonal wedge that is almost as high as it is long. 

Pedal sear very large and elose to anterior adductor 

scar. Adduetor musele sears large but not deeply incised; pallial line simple and relatively far from the 

ventral margin. 

Dimensions of holotype: Height 74.0 Inillimeters, 

width 75.0 millimeters, conve:\.'ity, 27.5 millimeters. 

Hoiotype, a right valve: U. S. National Museum, 

no. 136973. · 
SYSTEMATIC DESCRIPTIONS 177 

Type locality: Geological Survey station 2666, Jackson, Clarke County, Ala. Undifferentiated Claiborne 

group. 

This species seems to be most closely related to the 

Venericardia pilsbryi stock of the lower Wilcox, although the ribs are n1uch fewer in nun1ber than in l 1

• 

pilsbryi, the hinge is not so high, and the right middle 

cardinal is less produced. V. cla?-''l~ger may be distinguished from V. claiboplata by its wide, arched ribs, 

separated by almost linear intercostals, as contrasted to the narrower, higher flat-topped ribs of 

claiboplata, which are separated by distinct, comparatively wide intercostals. The more rounded or transversely ovate outline and the differences in the dentition will also readily separate the two species. 

Distribution: 

Claiborne group, undifferentiated: 

South Carolina, Aiken County, 4600r, Kennedy's 

scarp, half a mile west of Cox's Bridge, south side 

of Tinker's Creek (base of Cooke section, stratum 

no. 1). 

Alabama, Clarke County, 2666r, Selma & Mobile 

R. R. cut near Jackson. 

Venericardia (Venericor) horatiana Gardner 

Plate 39, figures 1-3, 5; plate 40, figures 1, 2, 5 

1897. Venericardia planicosta form 1' Harris [part], Bull. Am. 

Paleontology, vol. 2, no. 9, p. 55, pl. 10, figs. 1-4. 

1903. Venericardia hornii Gabb [part]. Dall, Wagner Free 

Inst. Sci. Trans., vol. 3, pt. 6, p. 1422. [Not Cardita 

hornii Gabb, Paleontology of California, vol. 1, sec. 4, 

pp. 174, 232, pl. 24, fig. 157, 1864.1 

1903. Venericardia planicosta form 1' Harris [part]. Dall, Wagner Free lnst. Sci. Trans., vol. 3, pt. 6, p. 1422. 

1917. Venericardia plmdcosta Harris [not Lamarck'?] [part]. 

Waring, Ca1iforuia Acad. Sci. Proc., 4th ser., vol. 7, 

no. 4, p. 54. 

1927. Venericardia horatiana Gardner, Washington Acad: Sci. 

Jour., vol. 17, no. 14, p. 369, figs. 28, 29. 

1928. Venericardia planicosta form 1' Harris [part]. Olsson, 

Bull. Am. Paleontology, vol. 14, no. 52, p. 27. 

1930. Venericardia horatiana Gardner. Stewart, Acad. Nat. 

Sci., Philadelphia Special Pub. 3, p. 180, pl. 9, figs. 1, 

2, 3; pl. 10, fig. 3. 

1936. Venericard-ia horat1'ana Gardner. RutE'ch, Eclogae geol. 

Helvetiae, vol. 29, pp. 163, 171, 174. 

1936. Venericardia aragom'a Arnold and Hannibal [part]. 

Rutsch, Eclvgae geol. Helvetiae, vol. 29, pp. 163, 164, 

168, 170, 171, 174, 177, 180. Not Venericardia aragonia Arnold and Hannibal, 1914. 

Shell rather small, thin, rudely quadrate, moderately inflated; 

obscurely flattened posteriorly. Umbones quite small, incurved, 

prosogyrate, acutely tapering, placed a little in front of the 

median vertical. Lunule minute, deeply impressed. Anterior 

end very broadly rounded; posterior dorsal margin obliquely 

sloping, rounding into the vertically truncate lateral extremity; 

base line feebly arcuate. Tips of umbones reticulately sculptured; radials, excepting on weathered specimens, restricted to 

the dorsal posterior portion of the shell, most closely spaced 

posteriorly, not developed on the extreme half or third of the 

shell; radials usually 20 or 21 in number, moderately elevated 

near the umbones and showing a slight tendency to be nodose; 

interradials near the umbones broadly U-shaped, the incrementals very fine and sharp and evenly developed in the channels 

but not overriding the radials; radial sculpture away from the 

umbones subcutaneous; the interradials appearing as very 

feebly incised lines, least feeble posteriorly; a scalloped incremental sculpture showing faintly upon the ventral portion of 

the shell. Hinge plate moderately heavy. Ligament exte'"Ilal, 

the area narrow and much produced. Dentition normal; E.nterior cardinal of right valve nearly obsolete; medial cardinal 

heavy, asymmetrically cuneate, posteriorly produced, feebly 

striated transversely; posterior right cardinal slender, elevEted; 

anterior left cardinal short, stout; posterior cardinal much produced, relatively slender, the inner surface of the anterior and 

both the lateral surfaces of the posterior cardinal t.ransve:-:-sely 

striated. Characters of interior sharply defined by the s1ight 

thickening of the shell over the surface of the adherent mantle. 

Adductor scars very distinct, the anterior rudely reniform, the 

posterior semielliptical; pedal scar small but deeply impre~"3ed, 

directly dorsal to the anterior adductor. Pallial line simple, 

rather far removed from the ventral margin; inner margins 

strongly crenate. 

Dimensions: Altitude 25 millimeters, latitude 27 millimeters, 

semidiameter 9 millimeters. 

Holotype: U. S. National Museum, no. 369238. 

Type locality: 1% miles "'est of Sabinetown, Sabine County, 

Tex. 

Geologic horizon: Wilcox formation. 

Yenericardia horatiana is remarkable for the quadrate outline 

and the character of the sculpture. Beneath the outer shell 

layer the radials are angulat" and persistent to the ventral margin; 

but in perfectly preserved specimens they are almost entfrely 

concealed by the epidermal veil. This epidermis is produced, at 

the lower margin, a trifle beyond the layers beneath, and the 

scalloping of this thin edge is remarkably sharp.-Gardner, 1927. 

This species, unfortunately, was described from. a 

young form. The adult outline is not quadrate but 

cordate-trigonal. However, l-renericard1.:a horai'i~na is 

a. species well c.ha.racterized both in its youthful and in 

its adult stages and restricted in its known distribution 

to the upper Wileox formations. The peculiar bulbous, 

strongly ineurved tips separate the young of V. stewarti 

of the Lisbon formation; and the adult V. horatiana 

differs from the Claiborne species in the higher, rr0re 

trigonal outline. V. hor·atiana shares with V. pota,pacoensis Clark and Martin an obsolete radial sculpture 

in the adult stages, but it seems in1probable that an 

intimate relationship is indicated by this comnon 

character. There is, on the eontrary, much in the 

sin1ple umbonal sculpture, the ill-defined postw·ior 

ar~a., the high hinge plate, a.nd the pa.llial line rather 

distant fron1 the ventral margin to suggest for V. horatiana a line of descent from "'V. p'ilsbry·i Stewart of the 

lower Wileox. 

Distribution: 

Wilcox group, Bashi formation: 

Alabama, Coffee County, 10012~> and 10781~>, Pea 

River at Churchwell's Bridge, NE~ sec. 12, T. 4 N., 

R. 19 E., about 5~·2 miles south of Elba; 10')13~> 

and 10780~>, power plant, Pea River, 4 miles below 

Elba. Clarke County, 10770~>, roadside and 

SE~ sec. 4, T. 11 N., R. 21 E., 1.6 miles south of 

Bashi; 3100~>, beds at Woods Bluff near Choctaw 

Corners and Thomasville; 7155~>, gully near mi1dle 

of sec. 7, T. 11 N., R. 3 E., about 3 miles west of 

Choctaw Corners; 262~>, 2667P, and 3099P, Woods 

Bluff, Tombigbee River. 
178 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

Texas, Sabine County, 4789° and 11100°, Sabinetown Bluff, 300 feet to a quarter of a mile below 

Sabinetown Ferry; 5142", 1% miles west of Sabinetown. 

Wilcox group, Hatchetigbee formation: 

Alabama, Choctaw County, 13051•, Hatchetigbee 

Bluff, Tombigbee River (F. E. Turner). 

V enericardia (Venericor) stewarti Gardner and Bowles, n. sp. 

Plate 39, figures 4, 6, 7 

1930. Venericardia horatiana Gardner [part]. Stewart, Acad. 

Nat. Sci. Philadelphia Special Pub. 3, p. 161. 

Shell large, heavy, roundly ovate in outline. Umbo 

inflated and beginning with a curiously characteristic 

bulbous tip. Lunule very deeply set. Anterior margin 

broadly rounded; posterior margin rounded and only 

slightly produced ventrally. Umbonal ribs high and 

narrow, with slight serrations, particularly on the 

extreme anterior ribs. Posterior region very well 

defined by the abrupt rounding of the ventral margin 

and bearing 6 ·indistinct, wrinkled costae; anterior 

region not distinctly separated from the medial portion; 

anteromedial portion of disk bearing above the first 

strong growth line 16 wide, rounded costals separated 

by linear intercostals, which, however, become obsolete 

over the major portion of the disk. Ligament marginal 

and external, but no true escutcheon developed; 

nymphae low and hea·vy. Hinge plate high and heavy; 

teeth high, narrow, and curved. Pedal and adductor 

muscle scars prominent. Pallial line distinct and 

simple. Inner and outer margins very faintly crenulate. 

Dimensions of paratype: Height 78.0 millimeters, 

width 96 millimeters, convexity 54 millimeters. 

Holotype, a left valve: U. S. National Museum, 

no. 154933; para type, the right and left valves of a 

single individual, U. S. National Museum, no. 116027. 

Type locality: Geological Survey station 3105, bed 

4 of Cooke section, Lisbon Bluff, Monroe County, Ala. 

Claiborne group, Lisbon formation, associated with 

Ostrea lisbonensis. 

Venericardia stewarti is abundantly represented in the 

Ostrea lisbonensis zone at Lisbon Bluff and is restricted 

apparently to that zone. It is close to 1/". horatiana 

Gardner, of the Bashi formation, and is probably in 

the line of descent. The two species may be most 

readily distinguished by the characteristic bulbous 

tips of V. stewarti. 

Stewart 50 spoke of a form similar to V. horatiana 

being found in the Lisbon of Alaban1a, and suggested 

that it be considered a distinct species, but because of 

the paucity of his material he did not definitely separate it. 

The species is restricted in its known distribution to 

the lower Caliborne of Alabama and Texas. 

10 Stewart, R. B., Gabb's California Cretaceous and Tertiary type Iamellibranchs: 

Acad. Nat. Sci. Philadelphia Special Pub. 3, p. 161. 1930. 

Distribution: 

Claiborne group, Lisbon formation: Ostrca lisbonen~is 

zone and its time equivalents: 

Alabama, Monroe County, 2668", 3105", and 5511", 

Lisbon Bluff, a short distance below Lisbon Landing, Alabama River. 

Claiborne group, Mount Selman formation, Weches 

greensand member: 

Texas, Sabine County, 11107•, Sulphur B.~anch near 

Sabinetown. 

Venericardia (Venericor) tonosiensis Rutsch 

Plate 40, figures 6, 7 

1919. Venericardia planicosta var. horni (Gabb) Vau~han, U. S. 

Nat. Mus. Bull. 103, p. 548. Not Cardita hC'rnii Gabb, 

Paleontology of California, vol. 1, sec. 4, Pf· 174, 232; 

vi. 24, fig. 157, 1864. 

1919. Venericardia planicosta Lamarck. Vaughan, U. S. Nat. 

Mus. Bull. 103, p. 577. Not Venericardia planicosta 

Lamarck, Mus. hist. nat. Paris Annales, vol. 7, p. 55. 

1806. 

1936. Venericardia tonosiensis Rutsch, Eclogae geologicae Helvetiae, vol. 29, pp. 168, 169, 170, pl. 16, figs. 2-4. 

Shell relatively small, not very heavy, e'"·enly but 

not strongly inflated, approaching much mo:"e closely 

to the rotund than the usual venericard. Umbones 

moderately prominent, broadly expanded, full to the 

ineurved, prosogyrate and proximate tips. Lunule 

very small and sunken, defined by a deeply impressed 

line. A false escuteheon suggested by shallow grooves 

extending from the umbones to about 1nidway along 

the truncated posterior n1argin, the narrovr cordate 

area thus enclosed occupying. more than hf'lf of the 

posterior area. Anterior Jateral margin bowed and 

rounding s1noothly into the up-curved br.<;;e. Posterior lateral margin obscurely truncate, the posterior 

area indicated by a flattening of the shell and a change 

in the character of the ribbing. Sculpture feeble and 

restricted largely to the early growth stages. Ribs on 

the umbones narrow, high, and finely ·noded but with 

no trace of lateral threading, fading out in the adolescent shell and almost or entirely obsolete in the adult, 

the 20 ribs on the anteron1edial portion sep'\rated by 

linear interspaces and tending to arch sligl'tly as in 

V. stewarti, the 8 low cords on the posterior r,rea evanescing even more rapidly than those upon the disk. 

Incremental sculpture rarely preserved but anparently 

unusually sharp and crowded. Ligament marginal, 

sunken, the nymphae heavy. Hinge plate rather short, 

the ventral margin curved slightly upward and the 

dentition concentrated. Anterior ·cardinal of right 

valve very short and slender, the medial deltoid, 

obliquely produced and moderately heavy, the posterior produced and rather slender; left cardinah laminar, 

almost equally heavy, the posterior the more produced. 

Interior thickened slightly over the area of the adherent 

mantle. Pedal and adductor sears deeply sunken in 

the adult shell. Pallial line distinct, normrl in position. Extreme ventral and lateral inner margins feebly 

crenate. 
SYS'I'EMATIC DESCRIPTIONS 179 

Dimensions of figured spechnen: Height 71.0 millimeters, width 70.0 millimeters, convexity 26.0 

millimeters. 

Holotype, Mus. Basel, no. 211. Figured specimen, 

a left valve, U. S. National Museun1, no. 372923. 

Type locality: Between Bucaru, at the mouth of the 

Rio Tonosi, and Punta Guanico, Province of Los Santos, Panama. Figured specimen, Geological Survey 

station 6586, mouth of the Rio Tonosi. Eocene 

(middle?). 

The figured specimen is one of a number collected 

by Donald MacDonald. 

Vaughan quotes Cooke as saying, "A species of 

Venericardia from this locality is scarcely distinguishable fron1 a specimen labeled Venericardia planicosta 

var. horni from Claiborne, Ala., but it does not closely 

resemble specimens that I have seen from the Eocene 

of California, Washington, and Oregon." The specimens in question in the Museum collections are now 

referred to Venericardia stewarti, a larger shell with 

a higher hinge plate and with more prominent and 

prosogyrate umbones terminn.ting in a curiously characteristic bulbous tip. v·. horatiana of the Bashi, 

another n1ember of the group, is also larger, more 

hatchet-shaped, with higher hinge plate n.nd umbones 

turned more strongly inwn.rd and forward and with a 

slightly lower rib count. The resembln.nce of Fenericardia tonosiensis to Venericardia pacifica Olsson, from 

the Salinn. formation of northern Peru, is remarkable. 

The Panan1n.nian species runs a little higher than the 

Peruvian, and there are slight differences in the character of the lunule, but in the general size and shape 

and sculpture pattern the two forms might very well 

be conspecific. The holotype of V. tonosiensis is 

unusually large. 

Distribution: 

Eocene (middle?): 

Panama, 6586P, Mouth of Tonosi River; 8414P, 

Bucaru; 8282° and 8295P, Guaniquito River. 

Venericardia (Venericor) pacifica Olsson 

Plate 37, figure 12; plate 41, figure 8 

1928. Yenericardia pacifica Olsson, Bull. Am. Paleontology, vol. 

14, no. 52, p. 30, pl. 6, figs. 3-5. 

1930. Venericardia pacifica Olsson. Stewart, Acad. Nat. Set 

Philadelphia, Special Pub. 3, pp. 172, 173. 

1936. ll enericardia pacifica Olsson. . Rutsch, Eclogae geol. 

Helvetiae. vol. 29, pp. 170, 171. 

Shell small or moderate size, rounded or subcircular in outlines 

and rather strongly convex; the beaks are situated about the 

anterior one-fourth; the dorsal margin is straight, while the 

anterior and posterior extremities are well rounded and together 

with the base or ventral margin form part of a curve which is 

nearly circular; umbos full and quite prominent with small, 

slightly prosogyrate, adjacent beaks; lunule very small; sculptured with about 28 ribs (about 19 to the umbonal slope); on 

the umbos, the ribs are narrow, elevated and beaded, and with 

deep U-shaped interspaces fully three times the width of the 

ribs themselves; the ribs change abruptly at a resting mark and 

below this point become wide, flattened or rounded on top, and 

separated simply hy incised lines. 

Length 41 millimeters, height 42 millimeters, diameter 31 

millimeters. 

Remarks.-This species .:>ccurs with the preceding [l'enericardia peruviana Olsson] and from which it is recognized by its 

circular form and character of its ribs. 

Locality and geologic occurrence.-Salina formation, Negri~os.­

Olsson, 1928. 

Stewn.rt compares l' .... pacifica to his V. hornii s11bsp. 

calafia of the Don1engine formation of the Pacific rnast, 

a comparison suggested by their common subcircular 

or almost quadrate outline. However, he further 

observes that "it [V. pacifica] also has noded ribs, but 

the deep U-shaped interspaces and larger numb~r of 

rihs tend to indicate that the two forms are not elosely 

related, the similarity in outline being fortuitous. 

However, the possibility that V. pacifica is relat~d to 

the California form rather than to any of the Gulf 

species is not excluded, since the development of the 

ribs of the subsp. calafia is practi,cally unknown." 

Venericardia pacifica is, to the stratigrapher, the most 

interesting species in the Peruvian series. Ther') are 

in the eollections of the Johns Hopkins University two 

valves, a right and a left, in which all the essential 

characters are preserved, both external and internal. 

They indicate the farthest outpost of a small, prot"'.bly 

never abundant group which includes V. horatiana of 

the Bashi and Hatchetigbee, possibly V. turneri of the 

Hatchetigbee; V~ stewarti of the Lisbon, and V. tonosiensis of the lower middle Eocene of Panama. It is 

indeed interesting to be able to extend the range of this 

group confidently to the lower middle Eocene of northern Peru and to quote Stewart's suggestion that there 

may be a Pacific ally. The Peruvian and Pananu'.nian 

species are extren1ely close. The Panamanian form is 

a little higher, the umbones are fuller, and in ar our 

exan1ples the lunule is wider and deeper than ir the 

two Peruvian valves. The growth sculpture upon V. 

pac·ifica is remarkably strong. Something of the snrt is 

indicated on V. tonosiensis but the surface is not well 

preserved, and we cannot be sure that the two s:r: ~cies 

are similar in this detail. The stratigraphy is still 

rather sketchily known, but there is no reason to 

assume that the Peruvian and Panamanian forms were 

not contempo:taneous. 

Venericardia (Venericor) turneri Gardner and Bowles, n. sp. 

Plate 41, figures 1, 2 

Shell large, heavy, remarkably quadrate, not strongly 

inflated. Dor£al and posterior lateral margins ap:r:roximately at right angles, but rotmding smoothly into one 

another. Anterior lateral margin shorter than the 

posterior, broadly arcuate, merging into the base; 

ventral margin pulled down at the posterior lateral 

extremity. Beaks within the anterior fourth, infated 

at the tips, involute and prosogyrate, broadly but 

rather feebly arched away from the tips. Lunule 

exceedingly small. Umbones badly eroded but s~ulptured with 28 narrow ribs, 6 of which are posterior; 

obseure traces of a serrate cresting preserved; ribs 
180 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

dying out on the adolescent shell, the adult sculpture 

reduced to incised lines separated by scarcely perceptible arches. Incremental lines strongest and most 

crowded toward the anterior ventral margin. Ligament marginal, deeply sunk. Hinge of right valve 

only known. Anterior cardinal short and oblique, the 

medial and posterior cardinals strong, the posterior 

cardinal produced parallel to the dorsal n1argin, the 

medial produced at a low angle to it. Muscle impressions strong, the interior slightly thickened over the 

area of the adherent 1nantle. Pedal sear a small but 

deep pit between ti1e anterior eardinal and the anterior 

adduetor sear. Pallial line sin1ple, rather far removed 

fron1 the base. Ventral margin rather feebly crenate 

within, the crenations corresponding to the in1pressed 

lines whieh n1ark tbe interradials. 

Dhnensions of holotype: Height 66.0 millin1eters, 

width 73.5 n1illin1eters, convexity 20 .. !5 millin1eters. 

I-Iolotype, a right valve: U. S. National Museun1, 

no. 372921. 

Type loeality: Geologieal Survey station 13051, 

Hatehetigbee Bluff, Tombigbee River, Washington 

County, Ala., 3 miles south of the Choctaw Count:v 

line. Wileox group, Hatchetigbee forn1ation. 

This speeies is nan1ed in honor of Dr. F. Earl Turner, 

of the Agricultural and ~feehanieal College, College 

Station, Tex., who eolleeted the type speein1en and 

generously donated it. 

Fenericardia tu.rnen~ is known only from two specin1ens, the holotype and a left valve (paratype) larger 

by a third than the holotype but with the entire hinge 

missing. It suggests, in the bulbous umbonal tips, the 

un1bonal ribbing, and the obsolete adult seulpture, the 

coexistent F. horat·iana; in the impressed lines whieh 

demark the interspaees it suggests r. p·z:lsbryi. In the 

quadrate outline, the horizontal dorsal rrmrgin, the 

narrow hinge plate, and the greatly produced medial 

and posterior teeth it is unique among deseribed Gulf 

species and exeeptionally well charaeterized. 

The closest approach to Trener-icardia turneri is, 

strangely enough, renen~card~·.a peruviana Olsson, of the 

Peruvian lower middle Eocene. The southern forn1 is 

more rounded, but both species are remarkable in their 

approximation to a quadrate outline. The umbones of 

F. frltrneri are eonstrieted, especially posteriorly, and 

the posterior region is wide, flattened, and flaring. 

Neither species is n1ueh inflated, and the body eavity in 

both is shallow. The hinge plate of the Peruvian form 

is higher than that of the Alabama species, an adjustment doubtless to the n1ore rounded outline of the shell 

of peru.viana. Both speeies run about 28 ribs, separated 

by n1ere linear iutercostals, but eontinuing cmnplete to 

the ventral n1argin as in v·. pilsbryi. 

Distribution: 

Wilcox group, Hatchetigbee formation: 

Alabama, Washington County, 13051, Hatchetigbee 

Bluff, Tombigbee RiYer. · 

Venericardia (Venericor) peruviana Olsson 

Plate 41, figure 9 

1928. V'enericardia peruviana Olsson, Bull. Am. Pahontology, 

vol. 14, no. 52, pp. 29, 30, pl. 6, fig. 1. 

1930. Ti"enericardia peruviana Olsson. Stewart, Acad. Nat. Sci. 

Philadelphia Special Pub. 3, pp. 151, 173. 

1936. Venericardia perzwiana Olsson. Rutsch, Eclogae geol. 

Helvetiae, vol. 29, p. 170. 

Shell rather large, inequilateral, broadly ovate or subelliptical 

in form and with the low beak situated very close to tl ·~ anterior 

extremity; posterior side widely rounded, the dorsal somewhat 

arched, the ventral gently rounded or nearly straight, anterior 

margin shorter; the shell is moderately convex, gre.atest just 

about the center of the disk, the umbos are low and not conspicuous with small, prosogyrate, and closely adjacent beaks; 

the lunule is very small; there is a faint depression or sinus, 

extending across the dorsal side of the umbos to the posterior 

margin and serves to separate the faintly sculptured posteriordorsal submargins from the heavier-sculptured surfs.ce below; 

sculpture consists of moderately heavy V-shaped ribs which 

cover most of the shell surface; on the umbos the ribs are heavy 

and strongly V -shaped or ridged but become rounded and wider 

toward the posterior-ventral extremity; the ribs number about 

19 from the anterior margin to the faint umbonal s~nus, with 

5 very faint additional ribs on the posterior-dorsal slor:e; interior 

concealed. 

Length 80 millimeters, height 66 millimeters, dianeter 41.5 

millimeters. 

Remarks.-There appear to be no closely related species to 

which this shell need be compared. It differs from the p1anicosta 

group by its form and V -shaped ribs. The umbonal surface is 

somewhat weathered in our specimens, but the ribs appear to 

have been slightly beaded and keeled. 

Locality and geologic occurrence.-Salina formation, ~T8gritos.­

Olsson, 1928. 

Stewart suggests that this form may be close to 

V. pectuncularis Lamarck, frmn the Thanetia n of the 

Paris Basin, a Vener£cardia. in the strict sense. 

A single left valve in the colleetions of tl'~ Johns 

Hopkins University shows the characteristic quadrate 

outline and ribbing pattern described by Olsson. 

The umbonal sculpture on that valve is ver~·r similar 

to that of V. pacifica. and V. stewarti, and the Leuroactis 

group is further suggested by the fairly high hinge 

plate, the eardinal dentition, and a pallial line remote 

from the margin as in V. pil.rsbryi. The quadrate outline is duplicated in V. tu-rneri, from the Hatchetigbee, 

but the hinge plate in the Wilcox speeies is mueh more 

narrow, and its dorsal and.ventral margins p;i'e more 

nearly pa.rallel. 

Venericardia (Venericor) potapacoensis Clark and Martin 

Plate 41, figures 3, 4, 6 

1896. "Venericardia planicosta Lamarck [part]. Clark, U. S. 

Geol. Survey Bull. 141, p. 80, pl. 23, figs. la, lb; pl. 

24, figs. la, lb. 

1901. Yenericardia potapacoensis 9lark and Martin, Geol. 

Survey Maryland, Eocene, p. 179, pJ. 40, figs. 4, 5, 5a, 

6, 6a. 

1903. Yenericardia potapacoensis Clark and Martin. Dall, 

Wagner Free Inst. Sci. Trans., vol. 3, pt. f, p. 1423. 

Not Yenericardia aff. potapacoensis, Dumble, Tertiary 
SYSTEMATIC DESCRIPTIONS 181 

deposits of northeastern Mexico, Science, new ser., 

vol. 27, p. 273, 1908. Not Venericardia potopacoenses?, 

Dumble, Eogene history of Mexican Gulf coastal area: 

Jour. Geology, vol. 23, p. 490, 1915. Not Venericardia 

potopacoensis, Dumble, Tertiary deposits in Northeastern Mexico: California Acad. Sci. Proc., 4th ser., 

vol. 5, p. 182, 1915. 

1917. Venericardia potapacoensis Harris. Waring, California 

Acad. ~ci. Proc., 4th ser., vol. 7, no. 4, p. 54. 

1919. Venericardia potapacoensis Clark and Martin. Harris, 

Bull. Am. Paleontology, vol. 6, no. 31, p. 77. 

1922. Yenericardia potapacoensis Clark and Martin. Woods, 

Geology of northwest Peru, p. 69. 

1930. Yenericardia potapacoensis Clark and Martin. Stewart, 

Acad. Nat. Sci. Philadelphia Special Pub. no. 3, pp. 

158, 160. 

1936. Venericardia potapacoensis Clark and Martin. Rutsch, 

Eclogae geol. Helvetiae, vol. 29, pp. 164, 169 [not 

p. 167, = V. digal. 

Shell small, very thick; valves relatively deep, and elongate 

along the line of the beak and posterior basal margin; beak 

anteriorly situated; lines of growth strong; ribs 20 to 24 in 

number, elevated and crenulated toward the beak and obsolete 

toward the periphery; lunule deeply impressed; muscular scars 

deeply impressed; margin strongly crenulate. 

This form is restricted to the Nanjemoy formation, and is most 

typically developed in the lower or Potapaco substage * * *. 

Length, 40 millimeters, width, 33 millimeters.-Clark and 

Martin, 1901. 

Venericardia potapacoensis is distinct from the Gulf 

species, V. diga, by reason of the solid dwarfish adult 

shell with the radial sculpture obsolete upon the final 

two-thirds, and the 19 to 22 rather strongly and regularly corrugated ribs upon the early part of the shell. 

They have in common the high hinge plate and scimitarshaped right cardinal. The strong umbonal noding suggests that the affinities of this species may possibly be 

not with the mediaplata stock and the section Le·uroactis but with some lateral branch of TT. smithii. 

Distribution: 

Pamunkey group, Nanjemoy formation: 

Maryland, Prince Georges County, 2489e, Piscataway 

Creek; (Maryland Geological Survey) Upper 

Marlboro, gully southwest of town; 1 mile southeast of Piscataway. Charles County (Maryland 

Geological Survey), La Plata, east and west of Port 

Tobacco, head of Nanjemoy Creek, half a mile 

below Chapel Point, 2 and 2~ miles above Popes 

Creek, river bluff below Popes Creek, Potomac 

River. 

Virginia, King George County, 13159c, Woodstock, 

about half to three-quarters of a mile west of 

Mathias Point, Potomac River; (Maryland Geological Survey), Potomac Creek, 50 feet from top 

of bluff. 

Venericardia (Ven~ricor?) labreaensis Olsson 

Plate 42, figure 5 

1929. Venericardia planicosta var. labreaensis Olsson, Bull. Am. 

Paleontology, vol. 15, no. 57, pp. 7, 8, pl. 3, figs. 1, 2. 

In this form the shell is small or medium-sized, moderately 

convex or inflated and with 19 or 20 strong, persistent ribs; 

umbos prominent, with strongly curved, adjacent beaks; 

lunule cordate, moderate in size and deeply sunken; on the 

umbos the ribs are high, narrow, and knifelike with deep, 'vide 

and flat interspaces; ventrally the ribs become wider and on the 

medial portion of the valve are broad and flat-topped, with the 

interspaces remaining deep but only about one-half the width 

of the ribs themselves; the first 5 anterior ribs are tripartite with 

a central, larger riblet bordered on each side by a smaller ril ~t; 

on the next 3 or 4 ribs (8-9) the central riblet increases rapidly 

in size, becoming wide and flat, while the lateral riblet is very 

small and threadlike, or simply a low, vanishing terrace; the 

following 5 ribs (to 14) lie across the medial portion of the valve 

to the umbonal ridge; the remaining ribs (to 19 or 20) on the 

posterior-dorsal submargins are low, narrow, with wide iderspaces. 

Length 36.50 millimeters, height 34 millimeters, diam"'ter 

27 millimeters. 

Remarks.-This variety is the dominant form in the Negritos 

formation or the Turritella beds of La Brea. It is distinguished 

from the other members of the planicosta group by its constantly 

tripartite anterior ribs. It is always a small or medium-sized 

shell, our largest specimen being about 45 millimeters in len?:th. 

Locality and geologic occurrence.-Negritos formation, La 

Brea.-Olsson, 1929. 

The hinge plate and dentition of Venericardia lab:.,.eaensis are very similar to that of Tlenericardia potc.:pa-

. coensis from the Nanjemoy of Maryland and Virg::nia 

and to Venericardia diga fron1 possibly a time equivalent 

formation in northeastern MeJ..ico. The ribs of the 

northern species are noded but not tripartite; those of 

the Mexican form are very imperfectly preserved but 

apparently have no conspicuous ornan1entation. In 

both of the North American species there is a ~ide 

variation in the number of the ribs and in their persistence. 

Venericardia (Venericor) diga Gardner and Bowles, n. S". 

Plate 41, figures 7, 10-12 

1908. Yenericardia a:ff. potapacoensis Dumble, Tertiary deposits 

of northeastern Mexico: Science, new ser., vol. 2'r, p. 

273. Not Venericardia potapacoensis Clark and Martin, 1901. 

1915. Yenericardia potopacoenses? Dumble, Eogene history of 

Mexican Gulf coastal area: Jour. Geology, vol. 2f. p. 

490. Not Yenericardia potapacoensis Clark and Martin, 

1901.] 

1915. Yenericardia potopacoensis Dumble, Tertiary deposit11 of 

northeastern Mexico: California Acad. Sci. Proc., 4th 

ser., vol. 5, p. 182. Not Yenericardia potapacoensis 

Clark and Martin, 1901. · 

1936. Venericardia potapacoensis Clark and Martin. Rutsch, 

Eclogae geol. Helvetiae, vol. 29, p. 167, not pp. 164, 

169. 

Shell large, solid, heavy, trigonal, hunched posteriorly, 

very slightly inflated; anterior margin almost verti~aJ, 

the tips of the umbones being almost in a line with 

the anterior extremity; posterior margin obliquely produced, making the shell very high and nar-row. Anterior region not distinguished from the medial portion 

by any marked change in ribbing but merely b~ a 

gradual narrowing of the costae and a greater curvature of the shell margin; posterior region indicated by 

a flattening of the contour of the shell and by a change 
182 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

in the rib characters, the concentric incremental lines 

traversing and wrinkling the narrowed, close-set 

costae. Earliest ribbing not well preserved at tips of 

any of the specimens but distinct in the cotypes within 

7 or 8tnillimeters of the extreme summit and low, broad, 

and fiat-topped, the intercostals being about as wide 

as the costae. Anteromedial region of the disk bearing 

17 ribs, the posterior region 8. Ribs broad and fiattopped in the adult portion, separated by narrow intercostals, evanescing on the ventral portion of the disk, 

ultimately disappearing at the ventral margin. Ligament external, set in a rather narrow and deep groove; 

no true escutcheon present; lunule long, narrow, and 

rather deep-set. Hinge plate very high and asynlmetrically trigonal, between one-third and one-half the 

altitude of the shell in the adult form. Dentition of 

right valve only known; all three of the cardinal teeth 

much produced vertically, the anterior cardinal laminar, 

the middle cardinal relatively slender and scimitarshaped, the posterior laminar, arcuate, and produced 

more than half the distance from the tips of the umbones 

to the posterior ventral margin. Body cavity unusually 

shallow. Pedal scar small and very close to the narrow, 

deep-set anterior adductor sear. Pallial line simple. 

Dimensions of cotypes: U.S. National Museum, no. 

373030, height 63.0 ± millimeters, width 57.0 ± millimeters, convexity 22.0 millimeters. U. S. National 

Museum, no. 373029, height 71.0 millimeters, width 

65.0 millimeters, convexity (double valves) 40.0 millimeters. 

Co types, a. pair of locked valves: U. S. National 

Museum, no. 373029 (Geological Survey station 13139) 

and a single right valve, U. S. National Museum, no. 

373030 (Geological Survey station 13140). 

Type localities: Geological Survey station 13139, 

left bank of Rio San Juan at Er1nita Abajo, Nuevo 

Le6n, Mexico; Geologieal Survey station 13140, Arroyo 

Ermita at crossing of main road from Ermita to La 

Arena, Nuevo Le6n, Mexico. Wilcox group. Probably middle Wilcox. 

In 1908 Dumble reported that "Among these [l\1e:\.'ican 

fpssils] is * * * a Venericardia, which Dr. Dall 

states is allied to potapacoensis of the Maryland 

Eocene, in beds that· are stratigraphically the continuation of the marine stage of the Texas section." Dall's 

statement must have been made in a personal communication; at least, no published record of it can be 

found. In the fall of 1915 Dumble wrote: "In the 

San Juan region, associated with the Venericardia planicosta, there are found vast nun1bers of a varietal form 

very similar to if not identical with V. potopacoenses of 

the Maryland Eocene." In Decen1ber of the san1e 

year he cited the occurrences of Venericardia potopacoensis, from the Lorna Larga escarpment, 2 miles north 

of Herreras; from a railroad cut 1 mile east of Herreras; 

from a hill half a mile west of La Ciga (Dumble, 1915; 

La Ceya on the field labels in the. collections of the 

U. S. N ationall\1useum); and at the Jaboncillos ranch 

20 miles south of San Juan, all in northeastern Mexico. 

Specimens obtained at "La Ceya" are still ir the collections of the United Sta.tes National Musemn. 

Venericardia diga has the general lop-sided outline 

. and the high hinge plate of Venericardia potapacoensis 

Clark and Martin, of the Nanjemoy Eoceno, of Maryland. The shells are laTger, however, and the young 

forms have a much more quadrate outline. The surface sculpture is for the n1ost part obliterated, but there 

is no suggestion retained of the strong and r~~gular noding such as that which characterizes the early stages of 

V. potapacoensis. There is no doubt that V. diga· is 

specifically distinct from the Maryland spe~ies, but it 

may be a southern analog and the two specie3 may have 

lived contemporaneously. The Volutocorbis which is 

commonly associated with V. diga is of the type abundantly represented at Woods Bluff, the classic collecting 

ground of the Bashi fauna. 

Most of the specimens of V. diga are pr~served as 

double valves, the strong teeth effectively locking the 

shells even in death. The shell itself is exceedingly 

thick, and the body cavity within very small, forming 

the rather incongruous picture of a very sn1all animal 

with a very large shell. It seems impossible for this to 

have been at all an active forn1, and any· moYement was 

probably accomplished only with the greatest difficulty. 

The two pairs of locked valves figured on plate 37, 

figures 1-3, may represent the diga which has not yet 

assumed senile characters. 

Distribution: This species is abundantly represr.nted in the 

Wilcox group of northeastern Mexico. 

Venericardia (Venericor) clavidens Grzybororski 

Plate 41, figure 5 

1899. Venericardia clavidens Grzybowski, Neues Jahrb., BeilageBand 12, p. 636, pl. 19, figs. 1, 1a. · 

1922. Venericardia planicosta Lamarck (group), form D. Woods?, 

Geology of north west Peru, pp. 68, 69, pl. 4, :fig. 4. 

1922. Venericardia clavidens Grzybowski. Woods, Geology of 

northwest Peru, p. 69. 

1928. Venericardia clavidens Grzybowski. Olsson, Bull. Am. 

Paleontology, vol. 14, no. 52, pp. 27, 28. 

Schale dreieckig, mit bogenformigem, nach hinten abfallendem 

Schlossrand, kurzem, fast geradem Vorderrand und zugerundetem Stirnrand. Sie ist sehr dick, auf der OberfHi.che verlaufen 

17-18, in der Whbelgegend tiefe, dann seichtere rurchen, die 

ebensovjele :flache Rippen begrenzen. In der Mitte der Schale 

verschwinden dieselben, und von da an wird die S':lhale his zu 

ihrem Ieicht gekerbten Rande nur mit concentrischen Zuwachsstreifen versehen. Das ungemein starke Schloss besteht aus 

· drei Zahnen, von denen der vordere ganz klein, der mit~lere der 

starkste, und der hintere von der Mitte gespalt~n ist. Hohe 

45 mm, Lange 50 mm, Dicke (einer Klappe) 18 mm. 

Diese Art ist der V. planicosta aus dem Pariser Eodi.n zum 

Verwechseln ahnlich. Der einzige Unterschied liegt nur darin, 

dass die Wirbel bier weniger hervorragen und der Hntere Zahn 

erst von der Mitte gespalten ist. 

Vorkommen: Zorritos, Rica Playa.-Grzybowski, 1899. 
SYSTEMATIC DESCRIPTIONS· 183 

There are no examples of this species available for 

comparison, but the figures and descriptions and the 

laws· of chance indicate that the specin1ens collected 

on a reconnaissance trip over 30 years ago represent 

the same species as that described much later by Olsson 

under the name V. samanensis and reported common 

over a wide area and through several formations of the 

higher Eocene. 

Venericardia clavidens may perhaps be a later Peruvian analog of V. diga, of the lower Eocene faunas of 

northeastern Mexico. 

Venericardia (Venericor) samanensis Olsson 

Plate 40, figure 4 

1928. Venericardia planicosta var. samanensis Olsson, Bull. Am. 

Paleontology, vol. 14, no. 52, pp. 26, 28, 29, pl. 5, figs. 

4, 5; pl. 6, fig. 6. 

1930. Venericardia samanensis Olsson. Stewart, A cad. Nat. 

Sci. Philadelphia Special Pub. 3, p. 172. 

1930. Venericardia planicosta var. samanensis Olsson, Bull. Am. 

Paleontology, vol. 17, no. 62, pp. 6, 9, 12, 21; pl. 1, 

fig. 1. 

1936. Venericardia samanens1's Olsson. Rutsch, Eclogae geol. 

Helvetiae, val. 29, pp. 168, 169, 171, 172. 

In this variety we have the final and culminating product of 

evolution of the Peruvian group of V. planicosta. It occurs rarely 

in the Restin rocks but becomes at once common and typical 

in the succeeding Saman. The shells are often very large, massive, typically hatchet-shaped with height exceeding the width. 

They are moderately or strongly convex, with wide, full umbos 

and strongly coiled beaks (but less than .in parinensis). The 

ribbing is strong in young shells and on the umbos of larger 

specimens, and persists over a larger area than usual in var. 

parinensis. Usually in large shells the ribbing extends over the 

upper half, leaving the lower part smooth ,or simply marked by 

faint radiating lines representing the faded-out ribs and by 

the growth lines. The usual number of ribs is about 21, those on 

the posterior-dorsal submargins being low and subobsolete. 

On the Restin specimens the ribbing is heavier and persists over 

a relatively larger area, and the interspaces are deeper and 

more groove-like (see fig. 4), while the ribbing on the Saman 

shells is more rounded, and the interspaces are much narrower. 

The hinge of the full-grown shell is very wide and massive. 

Its most striking feature is the development of wi:le, high, and 

vertically flattened· nymphs, which project upward and around 

which the ligament is attached. This adaptation is a natural 

one, as the area of ligamenta! attachment must be increased to 

care for the increased size and weight of the mature shell. In 

rare cases the ligament itself has been preserved and shows as a 

large, massive plug, projecting above and in a posterior direction along the dorsal area of two valves. A similar development of the nymphs, but to a much less degree, is seen amongst 

the typical planicosta of the Parisian basin. V. planicosta from 

the southern United States do not show this condition, and the 

nymphs are relatively small and narrow. 

Length 94 mi1limeters, height 100 millimeters, diameter 65 

millimeters (type), Saman sandstone; length 75 millimeters, 

height 80 millimeters, diameter 63 millimeters, Restin specimen. 

Localities and geologic occurrence.-Restin formation; Que. 

Salado. Saman formation.; horizon of the Saman conglomerate, 

Negritos, near Lagunitas, etc. Very abundant and large in the 

Saman sandstone of the Chira Valley, Paita, Bayovar, etc.-

Olsson, 1928. 

In the light of our sketchy information upon this 

species, we do not find adequate evidence for sepr.rating it from Venericardia clwvidens Grzybowski, 189~. 

Venericardia (Venericor) parinensis Olsson 

Plate 40, figure 3 

1922. Venericardia planicosta Lamarck (group), form B. Woods, 

Geology of northwest Peru, p. 67, pl. 3, fig. 2. 

1922. Venericardia planicosta Lamarck (group), form C. Woods, 

Geology of northwest Peru, pp. 67, 68, pl. 3, fig. 3 

1928. Venericardia planicosta var. parinensis Olsson, Bull. Am. 

Paleontology, vol. 14, no. 52, pp. 26, 27, 28; pl. 5, f~. 3. 

1930. Yenericardia parinensis Olsson. Stewart, Acad. Nat. Sci. 

Philadelphia Special Pub. 3, p. 172. 

1936. Venericardia pan·nensis Olsson. Rutsch, Eclogae geol. 

Helvetiae, vol. 29, pp. 168, 169, 170, 176, 177, 178, 180, 

pl. 16, figs. 1, 5. 

This variety begins in the Salina formation, continues up 

through the Pale Gredas into the Parinas, or characteristic of 

the group of rocks placed by Bosworth in his Clavilithes Sl'!ries. 

Usually the earlier forms. are but moderately convex, with 

stronger ribbing extending over the umbos onto the center of 

the shell disk but fading out rapidly nearer the ventral margins. 

(See Woods' fig. 2.) In the Parinas sandstone the shells are 

generally larger, heavy, with full convex umbos, curved beaks, 

and a heavy, high hinge. (See Woods' fig. 3.) The sculpture 

is weak and confined to the umbos and earlier portion of the 

shell disk, leaving the major part of the surface smooth, eYcept 

for growth lines. The umbonal slope is rounded as in the 

Parisien and Claibornian shells, and the dorsal submargin~ are 

but feebly differentiated. The ribs number as in negritensis, 

about 17 to the umbonal slope and 22 to 23 over the vrhole 

surface. 

In this type we find a close approach to the smoother forms of 

V. planicosta from the upper Wilcox and St. Maurice hor~.wns 

of Louisiana and Alabama, designated as variety gamm!:!. by 

Harris, and to V. ionensis Waring ( V. merriami Dickerson), 

from Oregon and California. In such case these smooth Vcnericardia are found in rocks of middle Eocene age.--Olsson, 1928. 

Olsson, Woods, and Stewart all agree that this form 

is comparable to the Iniddle Eocene forins of the V. 

horatiana and V. stewarti type. Stewart raises it to 

specific rank and places it at least tentatively in his 

subgenus Leuroactis, with V. horatiana, V. pilsbryi, 

and V. aragonia. 

v·enericardia parinensis is a higher and much nore 

massive species than any of the suggested analogs. 

The umbones are very· full, the hinge plate high, and 

the thin dorsal third of the medial cardinal of the 

right valve is bent forward almost at right angles; 

at least, that is the case in the single valve referrei to 

this species in the collections of the Johns Hopkins 

University, a valve 130 millimeters high and 110 TI'lillimeters wide. 

POSITION UNCERTAIN 

Venericardia (Venericor) francescae Gardner and Bowles, 1'. sp. 

Plate 46, figures 6, 7 

Shell small but sturdy, rounded-trigonal in ext~rior 

outline, quadrate in the interior, not strongly inflr.ted. 

Umbones Inoderately prominent, placed near the fl.nte-
184 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

rior third, their tips turned forward. Lunule small, 

deeply sunken. Anterior margin bowed in front of the 

lunule, the posterior squarely truncate, the dorsal and 

ventral margins subparallel. Posterior area delimited 

both by the oblique truncation of the shell and by the 

finer sculpture. Anterior and medial portion of the 

shell ribbed with 13 cordlike radials strongly wrinkled 

by the growth lines; the 6 posterior radials narrow but 

uniform and persistent to the margin. Growth lines 

strong over the entire shell. Hinge plate narrow; 

ligament n1arginal and deeply inset. Dental armature 

very imperfectly preserved; a short anterior, very 

obliquely produced medial and a laminar posterior 

cardinal in the right valve. Interior filled with matrix 

concealing the adductor and pedal scars. Inner margins crenate. 

Dimensions of holotype: Height 28.0 millin1eters, 

width 27.5 millimeters, convexity 12.5 millimeters. 

Holotype, a right valve: U. S. National Museun1, 

no. 372925. 

Type locality: Geological Survey station 6573, 1 

mile southeast of New Albany, Union County, Miss. 

Clayton formation of the Midway group. 

We have the pleasure of naming this little Midway 

species in honor of Miss Frances H. Walthall, formerly 

of Oxford, Miss., whose cordial kindness the senior 

author will always remember. 

Venericardia jrancescae is characterized by the conlpactness of its sinall, squarish outline and by the relatively few but prominent radials. 

It is known, unfortunately, only from the holotype. 

Distribution: 

Midway group, Clayton formation: 

Mississippi, Union County, 6573r, St. Louis-San 

Francisco Railroad cut, 1 to 1% miles southeast of 

New Albany. 

Venericardia (Venericor) jewelli Gardner 

Plate 42, figures 2, 3 

1935. Venericardia jewelli Gardner, Univ. Texas Bull. 3301, pp. 

1.57, 158-159, pl. 12, figs. 1, 2. 

Shell large, heavy, transversely ovate-trigonal in 

outline, rather strongly inflated in the umbonal region 

but flattening toward the margins, especially toward the 

posterior ventral margin. Posterior area defined less 

by the angulation of the shell than by the abrupt change 

from the coarse ribbing to a fine threading which tends 

to become obsolete away from the un1bones. Umbones 

prominent, broad and full, the tips incurved, proximate 

and prosogyrate; lunule sn1all, cordate. Costal sculpture very strong, the ribs exclusive of the fine posterior 

threading 13 to 14 in the types, separated by deep 

and squarely channeled interspaces which shallow a 

little toward the ventral margin; surface not preserved, 

but ribs apparently simple except for the strong concentric imbrication. Posterior threads 5 or 6 in the 

types, evanescent toward the ventral ma1gin. Characters of the interior not known. 

Djmensions of cotypes: Double valves, height 65 

millimeters, width 65 n1illimeters, convexity 45 millinleters. Right valve, height 65 n1illimeters, width 70 

millimeters. 

Cotypes, two pairs of locked valves: U. S. National 

Museum, no. 370914. 

Type locality: Geological Survey station 11758, 

limestone sca.rp near Indio Wells tank, about 29 1niles 

southeast of Eagle Pass, Maverick County, Tex. Midway group, Kincaid formation, Tehuacana member. 

ll'enericardia jewelli is remarkable for the flattening 

of the shell toward the ventral margin, the few broad, 

sin1ple radials, and the absence of any well defined 

sculpture on the posterior area. 

This species is nan1ed in honor of the late VTillia1n R. 

Jewell, who located the Indio Wells. We are indebted 

to him not only for the most interesting Wih~ox fauna 

that we have from Maverick County but alqo for his 

generous interest. His death was a great hss to all 

of us who were working in the Border country. 

Distribution: 

Midway group, Kincaid formation: 

Texas, Maverick County, 117 52P, Comanche Creek 

crossing on west road to Farias ranch; 11753?r, 

Bibora tank, 7 miles east of new Indio r-1.nch house; 

11755v, 3 miles north of Media tank; 11758v, near 

Indio Wells, about 29 miles southeast of Eagle Pass. 

Venericardia (Venericor) hijuana Gardner and Bowles, n. sp. 

Plate 42, figures 1, 6-10 

1860. Cardita subquadrata Gabb?, Acad. Nat. Sci. Fhiladelphia 

Jour., 2d ser., vol. 4, p. 395. Not Cardita subqltadrata 

Conrad, 1848. 

1896. Venericardia planicosta var. smithii Harris [part], Bull. 

Am. Paleontology, vol. 1, no. 4, p. 60. 

1896. Cardita subquadrata Gabb?, Harris, Bull. Am. Paleontology, vol. 1, no. 4, p. 60. 

Shell of moderate dimensions, crumbly and unusually 

thick; rounded in outline with broadly corvex, submedial umbones and a rather compressed ventral portion; posterior area flattened and sharply cut off from 

the disk by sculpture differences rather than by the 

contour of the shell. Lunule very short and deep. 

Ribbing coarse and persistent, the ribs numbering 15 

or 16 on the anteromedial portion and 6 to 8 on the 

posterior area; inverted V -shaped with serrate crests 

at the tips of the un1bones; lateral ridges st~ongly developed on the adolescent shell but dying out towa.rd 

the ventral margin of the adult, leaving a prominent 

but well-rounded ribbing upon the disk; rruch more 

persistent on the anterior eostals; posteri0r costals 

simple and relatively low. Incremental lan1ination 

obscure except upon the posterior area and toward the 

ventral margin of the adult. Ligament ma:rginal, the 

groove deep, opisthodetic. Hinge plate narrow but 

heavy. A laminar anterior, a short, narrovr, trigona 
SYSTEMATIC DESCRIPTIONS 185 

1nedial cardinal, and a much-produced, moderately 

heavy, oblique posterior cardinal in the right valve; a 

short deltoid anterior cardinal and a slender, somewhat 

crescentic posterior lan1ina in the left valve. Pedal 

and adductor n1uscle scars deep. Inner margins 

sharply crenate. 

Dimensions of adult cotype: Height and width, 

50.0 ± millimeters, convexity 20.0 millimeters. 

Co types: Two poorly preserved left valves; the 

dorsal portion of one cotype showing the juvenile and 

adolescent sculpture, U. S. National Museum, no. 

372919; the second cotype showing the adult sculpture, 

U. S. N ationall\1useun1, no. 372920. 

Type localities: U. S. Nationall\;luseum no. 372919, 

Geological Survey station 6091, n1ilepost 481, east of 

Middleton, Harden1an County, Tenn.; U. S. National 

lvfuseum, no. 372920, Geological Survey station 6495, 

cut on Southern Railway 1}~ miles east of Middleton 

and 200 feet east of ~ilepost 481, Hardeman County, 

Tenn. Lower Midway age. 

Gabb's reference to the species is as follows: 

Professor Safford sent me with the other species several fragments of specimens, which must have been at least 2 inches in 

diameter. They are of the same outline and, as far as I can 

ascertain, have the same markings as the above species [Cardita 

subquadrata Gabb]. In the larger specimens the intermediate 

radiating ribs die out, leaving the ribs of nearly the same shape 

as C. planicosta of the Eocene formation. 

Locality.-They are from Hardeman County, Tenn.-Gabb, 

1860. 

In the course of his discussion of Venericardia planicosta smithii Harris remarked: 

The specimens collected by Dr. Safford· and referred to by 

Gabb * * * as C. subquadrata? are a little different still; the tops 

of the ribs are rounded or flattened and are about as broad as the 

interspaces, near the umbones, or in young specimens each rib 

is placed upon a low, broader rib somewhat after the nature of 

~he costation in V. alticostata Conrad; this feature soon dies out, 

however, leaving the ribs, as Gabb has remarked, "of nearly the 

same shape as C. planicosta of the Eocene formation." To us 

the most remarkable feature of Dr. Safford's specimens is the 

paucity of ribs, numbering from 20 to 23 only. The compound 

ribbing and the crenulations on the superimposed ribs have been 

noticed in "ery young specimens of V. planicosia many times 

from different horizons and localities, but in these specimens it 

occasionally shows, though faintly, nearly to the margin.-

Harris, 1896. 

Venericardia h1juana is described with n1any misgivings because of the fragn1entary nature of the Inaterial. But it is so distinct and so well eharaeterized 

that, with the hope of better material long deferred, we 

have done the best we eould with imperfect speeimens 

that have been held for n1any years. The diagnostic 

features are the broad inflation of the umbonal region, 

the flattening toward the ventral and posterior margins, 

the sharp sculpture break between the disk and the 

posterior area, the simple juvenile ribbing followed by 

the laterally ridged adoleseent and later in the adult 

by a return to a sin1ple ribbing. The ribs are unusual 

in that they are so pro min en t and so sharply defined 

but without angularity. V. hijuana may be related to 

V. jewelli of the lower Midway of the Mexican border, 

a larger, heavier speeies with obsolete ribbing upou the 

posterior area. One interior mold probably of t~s 

speeies suggests sueh a relationship more strongly than 

the shells themselves. 

Distribution: 

Midway group, Clayton formation: 

Tennessee, Hardeman County, 6495 c, 1 ~ mileE' east 

of Middleton, 200 feet east of milepost 481; 6091 c, 

milepost 481, east of Middleton; 12028 c (:rrold), 

public road at northeast edge of Middleton. 

VENERICARDIA SMITHII stock 

V enericardia (V enericor) smithii Aldrich 

Plate 43, figures 2, 3 

1894. Venericardia planicosta Lamarck {part]. Harris, Arkansas Geo1. Survey Ann. Rept. for 1892, vol. 2, p. 42. 

1894. l"enericardia smithii Aldrich, Alabama Geol. Survey Report on geology of Coastal Plain of Alabama, p. 243, 

pl. 12, figs. la-b. 

1896. Venericardia planicosta var. srnithi Aldrich [part]. Harris, 

Bull. Am. Paleontology, vol. 1, no. 4, pp. 59-61, pl. 4, 

fig. 14; pl. 5, figs. 1, 2. 

1903. Venericardia smithii Aldrich. Dall, Wagner Free Inst. 

Sci. Trans., vol. 3, no. 6, pp. 1422, 1425. 

1909. Venericardia smithi Aldrich. Grabau ~nd Shimer, J\T orth 

American index fossils, Invertebrates, vol. 1, p. 544·, fig. 

747 (right valve). 

1922. Yenericardia planicosta va.r. smithi Aldrich. Woods, 

Geology of northwest Peru, p. 68. 

1933. Vener;cardia smithii Aldrich. Plummer, Univ. Texas 

Bull. 3232, pp. 543, 547, 551, 552, 811, 812, r:L 8, 

figs. 4a. 4b. 

1935. Venericardia smithii Aldrich. Gardner, Univ. Texas Bull. 

3301, pp. 16Q-161, pl. 12, figs. 3, 4. 

Shell large, solid, slightly transverse, inflated, inequilateral, 

strongly ribbed, beaks strongly recurved, elevated; ribs 32-25 on 

specimens figured, flat in central part, strongly tuberculated, 

both on the anterior and posterior, more faintly marked or the 

central part; teeth nearly transverse, cavity of shell deep, mmgin 

crenulate, cicatrices slightly impressed. 

The drawings are slightly larger than the shells. The general 

outline of this species is like V. planicosta Lamarck, with which 

it is associated and of which a figure is also given. 

Differs from V. alticostata Conrad (transversa Lea) in the flatness of the ribs. Figure 1 is from a specimen in my collec-l:ion, 

the other (lb) is in the State collection. Rather abunca.nt. 

Named in honor of Dr. Eugene A. Smith.-Aldrich, 1894. 

1\ir. Aldrich's eollection was purchased by the Johns 

Hopkins University, and one of the cotypes (figs. 1-1a) 

is now in the Paleontologie Laboratory in Baltimore. 

Dimensions of eotype: Height 40.5 n1illimeters, 

width 43.0 n1illimeters. 

Type locality: "Turritella roek near Allenton, Wilcox 

County, Ala." Midway group, Clayton fonnation. 

Venericardia smithi·i is widely distributed througl'')Ut 

the Midway from Georgia to the Mexican border, but 

rarely is it a particularly abundant member of the 

molluscan fauna. Although the type loeality if\ in 

Alabama, the speeies is most con1monly reeorded from 

the Midway of Texas. Its large inflated valves and 

the numerous high, narrow eostals without lateral 
186 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

terraces or intercalaries characterize the species. 

This form differs from V. mediaplata, the other widespread Midway species, in the character of the ribs and 

the inflation of the umbones. 

While the distinction between Stewart's Venericor 

and his Miocene group Glyptoactis typified by Venericardia hadra Dall is clear and striking in the type 

species, some of the early peripheral forn1s are difficult 

to aline. This is quite as it should be, for Venericardia 

was burgeoning in the early Midway, and the groups 

had not yet taken their later shapes. The character 

and inclination of the cardinal teeth in the Eocene 

forms is closely correlated with the outline of the shell 

and consequently, in many species, with the age of the 

shell. The small anterior pustule, cited by Stewart as 

a subgeneric character, is in many forms present at the 

base of the l~nular groove but seems to be, at least in 

these early species, analogous not to a lateral tooth 

but to the crenulations upon the inner margins at the 

bases of the interradial grooves. Venericardia smithii 

has much in con1mon with V. alticostata, the Eocene 

representative of Glyptoactis, and these two species are 

separated subgenerically with some misgivings. But 

Venericardia smithii is quite clearly genetically related 

.to V. aposmithii, one of the massive venericards that 

has been commonly identified with Venericardia 

planicosta, and for that reason this shell, which is 

characterized by its inflated umbones, the relatively 

low, broad hinge plate, and the inclination of the teeth 

adjusted to the hinge plate is placed among the V enericors. 

Distribution: 

Midway group, undifferentiated: 

Georgia, Schley County, 4032r, Wall's Crossing, 

4 miles west of Ellaville. 

Midway group, Clayton formation: 

Alabama, Wilcox County, 281P and 284P, Prairie 

Creek. 

Midway group, Kincaid formation: 

Texas, Kaufman County, 11665h, Water Hill, 5 

miles northeast of Kemp; 10744r, 2~ miles northeast of Kemp on public road. Limestone County, 

6559?r, Comanche Crossing, 6 miles west of Mexia; 

11935 ?r, 7H miles northwest of Groesbeck on the 

Thelma road; 11939r, 3 miles southwest of Thornton. Falls County, 11931 ?r, about 6 miles northwest of Kosse. Bastrop County, 11696P, Colorado 

River 1% miles below Travis-Bastrop County line; 

11899?P, 50 to 60 feet west of bridge over Cedar 

Creek on Austin-Red Rock road; 11909P, Cedar 

Creek 3?~ miles southeast of Williams' store. 

Caldwell County, 11707P, 5?'2 miles due north of 

Lockhart; 11706P, 5H miles southeast of Lockhart. 

Medina County, 6280?r, Hondo Creek one-eighth 

mile below road crossing east of Elstone; 6584?r, 

D'Hanis-Yancey road 7 miles southeast of D'Hanis; 

11872?r, 6.6 miles south of Dunlay, south of Noonan 

road. Uvalde County, 3180?r, Bluff on Frio 

River half a mile below Evans' (Myrick's) apiary; 

6279?r, 11 miles south of Sabinal, south of junction 

of Elm Creek with Sabinal Creek. Maverick 

County. 11752?P, Comanche Crossing on west 

road to Farias ranch; 11758P, Indio Wells, about 

29 miles southeast of Eagle Pass; 11761P, Tobar 

Arroyo 2?~ miles southwest of Tobar ta.nk, about 

35 miles southeast of Eagle Pass; 6275r, White 

Bluff on Rio Grande, 4% miles west of south of 

Windmill ranch house; 8792a, Rio Grande, Texas 

side, 1 mile below Cerrito Prieto ranch house on 

Mexican side; 6577", 6~ miles southweE't of Windmill ranch, Rio Grande, Mexican side. 

Midway group, Wills Point formation: 

Texas, Guadalupe County, 11883r, 9?~ Iriles northeast of Seguin. Maverick County, 11754", 6 miles 

below McFarland sheep pens, 27 mileE' southeast 

of Eagle Pass on Windmill (Jacal) rancl· road. 

Venericardia (Venericor) aposmithii Gardner and Bo,.-.•les, n. sp. 

Plate 43, figures 1, 6, 7; plate 44, figures 1, 2 

1897. Venericardia planicosta Lamarck, form (:J, Harris, Bull. 

Am. Paleontology, vol. 2, no. 9, p. 55, pl. 9, fi~. 1. 

1903. Venericardia regia Conrad [part]. Dall, W s.gner Free 

Inst. Sci. Trans., vol. 3, pt. 6, p. 1422. 

1930. Venericardia regia Conrad [part]. Stewart, Acad. Nat. 

Sci. Philadelphia Special Pub. 3, pp. 154, 155, 156. 

Shell1nassive, the maximum altitude more than 100 

millimeters. Outline cordate-trigonal, the u1nbones 

high, inflated, incurved, prosogyrate. Postrrior area 

flattened. Lunule s1nall, wider in the right valve than 

in the left. Un1bonal ribs high, with narrow serrate 

~rests. Adult ribs broad, the anterior costr.ls corrugated by the growth lines, the medial low and separated 

by little more than linear interspaces, the posterior 

area coarsely and rather closely corded; numr~r of ribs 

in the type, 20 upon the medial and anterior areas, 10 

upon the posterior, but as many as 36 in all in some 

individuals; later~l ridges frequently developed anteriorly but not persistent to the adult stage; rib~ tending 

to evanesce toward the anterior ventral margin, where 

the growth sculpture is strong. Ligament t.nd hinge 

armature adequately heavy for so ponderou~ a shell; 

hinge plate high and narrow, the middle cardinal in the 

right valve obliquely cuneate and massive. Muscle 

scars, especially the anterior and pedal, deeply impressed; the elliptical anterior and rotund posterior 

scars very large. Interior of shell slightly thickened 

over the area of the adherent mantle. Pallial line 

ragged, rather far ren1oved from the margin. Inner 

marginal crenations very coarse. 

Dimensions of holotype: Height 113 millimeters, 

width 117 millimeters. 

Holotype, the right and left valves of a single individual: U. S. National Museun1, no. 1434. 

Type locality: Bells Landing, Alabama River, sec. 

36, T. 10 N., R. 6 E., Monroe County, Ala. Wilcox 

group, Tuscahoma formation. 

The differences between the Nanafalia and Tuscahoma races have not been recognized in the taxonomy, 

because the small number of speciniens available for 

study from Nanafalia Bluff does not justify generalizations. The number of ribs in the Nanafalia irrlividuals 

apparently runs higher by 2 or 3 to the valrre, an in-
SYSTEMATIC DESCRIPTIONS JB7 

crease due to the closer cording upon the posterior 

area. The posterior cords in the Tuscahoma are usually 9 or 10, while in the Nanafalia they are more 

con1monly 11 or 12. Those nearest the posterior 

dorsal margin are wider and less elevated than the 

half dozen or so in front of them, a differentiation which 

is much less marked in the Tuscahon1a individuals tha~1 

in those of the Nanafalia. The Tuscahoma forms are 

larger, higher, and heavier than those collected fron1 

the Nanafalia, but the pattern of the ribbing is the 

same both on the .unbones and on the adult portion of 

the shell. The tendency toward the evanescence of 

the anterior and medial ribs has been noted only in 

the Tuscahoma representatives. · 

This species may well be descended from the ll. 

srnithii stock of the middle Midway. The outline of 

the early part of the shell in F. aposrnithii is very similar 

to the adult V. srnithii, and the ridged and serrate 

umbonal ribbing is siinilar in both. The lateral terracing in the Nanafalia and Tuscahoma species is, however, only vaguely foreshadowed in V. srnithii. There 

is an appreciable variation in the degree and persistence 

of lateral terracing both in the Nanafalia and in the 

Tuscahoma. The Tuscahoma forms approach V. regia 

of the Aquia n1ore closely than the Nanafalia forn1s. 

Distribution: 

Wilcox group, Nanafalia formation: 

Alabama, Marengo County, 271I> and 5642I>, Nanafalia Bluff, Tombigbee River. 

Wilcox group, Tuscahoma sand: 

Alabama, Monroe County, 2670", 3118", 5604", 

lower fossil bed, Greggs Landing, Alabama River; 

260", 3098", 5593", 5594", and U. S. National 

Museum, no. 1434", Bells Landing, Alabama River. 

Choctaw County, 5472", lower bed, Tuscahoma 

Landing, Tombigbee River. 

Venericardia (Venericor) regia Conrad 

Plate 46, figures 8, 10 

1830. Venericardia planicosta Lamarck. Conrad, Acad. Nat. 

Sci. Philadelphia Jour., 1st ser., vol. 6, p. 215. 

1832. Cardita planicasta Lamarck [part]. Conrad, Fossil shells, 

p. 20, pl. 5, fig. 2. 

1865. Venericardia planicosta var. regia Conrad, Am. Jour. 

Conchology, vol. 1, pp. 8, 364. 

1866. 1-r enericardia regia Conrad, Smithsonian Misc. Coli. no. 

200, p. 5. 

1891. Cardita regia Conrad Hei1prin, Acad. Nat. Sci., Philadelphia Proc. for 1890, p. 402. 

1894. Yenericardia planicosta var. regia Conrad. Harris, Am. 

Jour. Sci., 3d ser., vol. 47, p. 302. 

1896. Yenericardia planicosta var. regia Conrad. Harris, Bull. 

Am. Paleontology, vol. 1, no. 4, p. 58. 

1896. Venericardia planicosta Lamarck lpart]. Clark, U.S. Geol. 

Survey Bu1l. 141, p. 80, pl. 21, fig. 3; pl. 22, fig. 2; p1. 23, 

fig. lc; pl. 24, fig. lc; pl. 25, fig. lc. 

1901. Venericardia planicosta var. regia Conrad. Clark and 

Martin, Maryland Geol. Survey, Eocene, p. 178, pl. 38, 

figs. 1, 1a; pl. 39, figs. 1, la; pl. 40, figs. 1, 2, 3. 

1903. Venericardia regia Conrad. Dall, Wagner Free Inst. Sci. 

Trans., vol. 3, no. 6, pp. 1420, 1421, 1422. 

1909. Yenericardia planicosta var. regia Conrad. Grabau and 

Shimer, Index fossils, vol. 1, p. 545, fig. 746. 

1922. Venericardia planicosta var. regia Conrad. Wo':lds, 

Geology of northwest Peru, pp. 66, 69. 

1930. Venericardia r·egia Conrad. Stewart, Acad. Nat. Sci. 

Philadelphia Special Pub. 3, pp. 154, 155, 156, 157. 

1936. Venericardia regia Conrad. Rutsch, Eclogae geol. Helvetiae, vol. 29, pp. 162, 163, 164, 169, 180. 

Shell large, very heavy, broadly rounded to subovate, 

not very highly inflated. Anterior margin broadly 

rounded, posterior n1argin obliquely produced and 

obtusely truncate. Umbones strongly curved forward; un1bonal sculpture consisting of high, narrow ribs 

corrugated by large, regular serrations, which poEJ.teriorly and medially die out very close to the sumn1it but 

anteriorly persist to the first major incremental line, 

some 20 to 25 millimeters from the tip. Sculpture on 

disk consisting of broad, flat-topped ribs that persist 

strongly to the ventral margin. Ribs of anteronwdial 

portion 20; of the posterior region, 7. Posterior region 

well defined by a marked change in the character of the 

rib bing and by a decided change in the direction of the 

shell contouring. Posterior ribs .close-set and wrinkl~d, 

traversed by many fine incremental striae; anterior ribs 

also cut by concentric lines but more widely spaced r.nd 

le~s wrinkled than the posterior. Hinge plate rather 

high and very wide; dentition strong and prominent. 

Lunule very narrow and deep; nyn1phae high. Muf~le 

scars prominent and deep-set, especially the pedal pit. 

Inner margin strongly crenulate. 

Diinensions of probable holotype: Height about 100 

millimeters, width about 110 n1illimeters. 

Type: None designated by Conrad, but Stewart in 

1930 thought that the specimen so well illustrated by 

Clark in 1896 and by Clark and ·Martin in 1901 was the 

same as that figured by Conrad in 1832 and should be 

taken as the type, because the figure was the o:q}y 

description of the shell offered by its author. The 

specimen figured by Clark is no. 12508 in the collections 

of the Philadelphia Academy of Sciences. 

Type locality: Maryland(?), Pamunkey group, Aquia 

formation. 

Conrad never actually described this species, the £.rst 

mention of the name reg1.~a occurring in his check list 

of Tertiary fossils in 1865. He figured a form in 1832, 

however, which he called Venericardia planicosta a.nd 

which he said was from Maryland, a large species that 

is undoubtedly the same as that which he subsequently 

designated V. regia. He mentioned in 1865 that his 

species differed from V. planicosta s. s. only in hav~ng 

the ribs distinctly separated at the base. It is interesting to note that the first discovery of the V. planicosta stock in this country was made by Conrad in 

1830, when he found some large specimens in Maryland, 

undoubtedly V. regia, as it is the only large form 

recorded in the northern fauna. · 

Venericardia regia is restricted to the Aquia formation of Maryland and Virginia. It is the analog in 
188 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

the northern fauna of V. aposmithii of the southern, 

but the species are readily separable and less sin1ilar 

than might be supposed from the confusion in the literature. Both Dall and Stewart regard the Maryland form 

as conspecific with the "form beta" of Harris CF. 

aposmithi,i n. sp.), fron1 Greggs and Bells Landings, in 

Wilcox County, Ala. V. regia has a lower shell, however, the umbones are lower and less inflated, and the 

hinge plate broader. The character of the ribbing is 

the sanw in both, but in V. regia it runs a little stronger 

and is more strongly corrugated toward the margin by 

the incrementals. 

Distribution: 

Pamunkey group, Aquia formation: 

Maryland, Prince Georges County, 2489P, Piscataway 

Creek. 

Virginia, Stafford County, 1 mile east of 12974P, 

Stafford Courthouse; 2346", mouth of Potomac Creek. 

(And numerous localities in Maryland cited by Clark 

and Martin in 1901.) 

Venericardia (Venericor) austroplata Gardner and Bowles, n. sp. 

Plate 42, figures 11, 12 

Shell large, heavy, ovate cordate and inflated. 

Umbones high, full, and directed forward. Anterior 

margin bowed out in front of the small, deeply sunl&n 

lunule. Posterior margin produced ventrally, obtusely 

truncate laterally. Posterior area indicated both by a 

flattening of the shell and by an abrupt change in the 

character of the radial sculpture. Costals remarkably 

prominent; undercut and T -shaped in the umbonal 

region but without terracing or serrations; wide, high, 

and flat-topped on the medial portion of the disk; overridden toward the base by numerous concentric incremental lines but distinct and persistent to the margin; 

intercostals U-shaped, narrow, and deep; costals on 

the anterior part of the shell relatively high and slightly 

wrinkled, widening very rapidly and separated by little 

more than linear interspaces; posterior area hea·vily 

corded, 6 cordlike ribs in the left valve of the type, 

5 in the right; 15 upon the anteron1edial portion. 

Ligament marginal, the nyn1phs sunken, extending 

almost half the distance from the umbones to the 

posterior ventral margin, a part of the plug still remaining and indicating an extraordinarily powerlul and 

adequate attachment. Hinge plate low, wide, and 

heavy, the teeth badly broken in the separation of the 

valves. Anterior right cardinal seen1ingly rather narrow but n1uch produced obliquely; left cardinals relatively slender, produced and oblique rather than curved. 

Interior filled with n1atrix concealing the adductor and 

pedal scars. 

Din1ensions of holotype: Height, 91 millin1eters; width 

101 millimeters; convexity, 66 millimeters. 

Holotype, the right and left valves of a single individual: U. S. National Museum, no. 372924. 

Type locality: Geological Survey station 8077, Point 

Malaspina, Province of Chubut, Argentina. 

Three excellent exan1ples of this species are included 

in collections made by Bailey Willis and Chester W. 

Washburne. In all of then1 a replacement by crystalline gypsum is n10re or less complete. The hinge and 

ligament are very powerful in these forms. the specimens still being held together so tightly that the valves 

must be forced apart with great injury to the teeth. 

This large and distinctive species is the orly n1ember 

of the Venericardia planicosta group recordE,d from the 

Eocene of Argentina. The age of the source forn1ation 

is not known. The costal sculpture of V. a1J,stroplata is 

more vigorous than that adorning any of our Gulf 

venericards, and most of the Mid-An1erican and North 

American species show an umbonal serration of which 

there is no trace in V. austroplata. The associated 

fauna at Point Malaspina includes a Turritella and a 

Volutocorbis which suggest the lower Eocene, but the 

evidence for correlation within the Eocene is very slight. 

Distribution: 

Eocene series, undifferentiated: 

Argentina, Province of Chubut, 8077, Point Malaspina. The exact locality is in doubt, but the shell 

and its mode of preservation are so remarkable 

that it has been described in the hope that the 

locality may be more exactly defined later. 

Venericardia (Venericor) densata pendletonensis Gardner and 

Bowles, n. subsp. 

Plate 45, figures 12, 13 

Shell relatively small and thin, ovate-trigonal to subquadrate in outline; inflated strongly in th~ umbonal 

region but flattening toward the ventral margin. Umbones full, the tips incurved and prosogyrate, proximate 

and overhanging the short deep-s~t lunule, which is 

wider in the right valve than in the left. Porterior area 

set apart from the rest of the disk not only by the 

oblique flattening of the shell but also by the finer, 

c.loser ribbing. Ribs 28 or 29 in all, the posterior area 

bearing 7 of these. Umbonal ribs sharp-r~dged and 

serrate, the adolescent ones T -shaped and medially 

noded, the adult ribs simple and proximate, separated 

by linear channels; the adolescent nodes failing rather 

abruptly when the sh~ll is about n~ centimo,ters high. 

Hinge plate wide; anterior cardinal short u.nd almost 

vertical, the medial cardinal obliquely deltoid, the 

posterior produced and laminar. Interior thickened 

. slightly over the area of the adherent n1antle. Muscle 

scars distinct, especially the anterior adductor and the 

pedal scar. Pallial line simple; inner n1argins strongly 

crenate. 

Dimensions of holotype: Height 27.5 n1illimeters, 

width 29.5 millimeters, convexity 12.0 millineters. 

Holotype a right valve: U. S. National Museum, 

no. 372694. 

Type locality: Geological Survey station 10743, 

Pendleton Bluff, Sabine River, Sabine County, Tex. 

Wilcox group, Tuscahoma sand. 
i 

I 

SYSTEMATIC DESCRIPTIONS 189 

Venericardia densata pendletonensis is the only iforn1 

of densata which has been recognized below the :Claiborne. It differs from the species so abundaljlt at 

Lisbon Bluff in the lower average dimensions{ the 

stronger flattening of the shell toward the anterior 

margin, and the lower adult hj.nge plate. The I subspecies is recorded reluctantly, because aside fro:ril the 

occurrence at this single locality, Venericardia densat1

'a has 

served faithfully as a guide fossil of the lower Claiborne. 

The bluff from which these collections were mdde is 

about a quarter of a n1ile above the ferry which inl 1932 

was still the usual means of crossing from the Te:x;as to 

the Louisiana side. ' 

Distribution: 

Wilcox group, Tuscahoma sand: 

Texas, Sabine County, 107 43r, Pendleton Bluff, a 

quarter of a mile above Pendleton Ferry, Sabine 

R~e~ • 

Venericardia (Venericor) densata malinchae Gardner and Bowles, n. subsp. · 

Plate 43, figures 4, 5 

Shell heavy and compressed for the group. 0-ij_tline 

of the adult specimens incomplete but rounded-trigonal 

in the yotmg, with a broadly and smoothly rou'nded 

anteroventral n1argin and an obscurely truncate 

posterior extremity. Umbones very low, the! tips 

proximate and turned slightly forward, anteri@r in 

position. Lunule small, cordate, defined by a d~eply 

incised groove. Posterior area indicated byi the 

flattening of the shell and the narrowing and partial 

evanescence of the radials. Ribs 20 on the ariteromedial portion, 8 on the posterior, probably ! with 

noded crests in the early growth stages and a rather 

obscure lateral terracing; the adult ribs low and fiat 

1nedially, n1ore elevated anteriorly and n1ore co~dlike 

posteriorly; the intercostals narrow U-shaped channels. 

Ligament Inarginal, deeply inset. Hinge high: and 

heavy; anterior right cardinal very short and thiri; the 

m'edial massive, flattened along the vertical plane, 

broad at the base, with the posterior margin curved 

forward toward the tips of the un1bones; posterior 

right cardinal very slender and produced; dentitibn of 

left valve not preserved. Pedal scar deep. AddtiCtor 

scars and pallial characters lost. 

Dimensions of holotype: Height (estin1ated) ! 48.0 

millimeters. · 

Holotype, an incomplete right vn1ve: U. S. N a~ional 

~fuseun1, no. 373031. 

Type locality: Geological Survey station 13141, 

about 1 mile southwest of El Mirador, China, Qarlos 

Cantu, Nuevo Leon, Mexico. 

. A forn1 so imperfectly known is described or{ly because it represents a fauna rarely preserved. It seems 

I 

to be related on the one hand to the more strongly 

sculptured Venericardia diga, from which it diff~rs in 

the lower umbones and the higher rib count, and on 

the other hand to Venericardia densata, from which it 

20412-39--4 

differs in the more rounded outline, the lower umbones, 

and the less pronounced noding and terracing in the 

early and adolescent growth stages. 

Venericardia (Venericor) densata Conrad 

Plate 37, figure 7; plate 45, figures 1-11, 14 

1845. Cardita densata Conrad, Acad. Nat. Sc!. Philadehhia 

Proc., vol. 2, p. 173. 

1848. Cardita densata Conrad, Lea, Henry, Catalogue of Tertiary Testacea of the United States, p. 5. 

1848. Cardita densata Conrad. Acad. Nat. Sci. Philadel'1hia 

Jour., 2d ser., vol. 1, pt. 2, p. 130, pl. 14, fig. 24. 

1848. Cardita densata Conrad. Lea, H. C., Acad. Nat. Sci. 

Philadelphia Proc., vol. 4, p. 97. 

1850. Cardita densata Conrad. Tuomey, Alabama Geol. Su-vey 

1st Bienn. Rept., p. 153. 

1857. Venericardia planicosta Lamarck. Emory, Mexican 

Boundary Survey, Rept., p. 161, pl. 19, figs. 2a, 2b 

Not Venericardia planicosta Lamarck. Owen, Geological reconnaissance of Arkansas, 2d Rept., pl. 9, figs. 2, 2a. 2b, 

1860. 

Not Cardita densata Conrad. Owen, Geological reconnaiss1.nce 

of Arkansas, 2d Rept., p. 35, 1860. 

1865. l"'enericardia densata Conrad (Cardita), Am. Jour; Conchology, vol. 1, p. 8. 

1266. Venericardia densata Conrad, Smithsonian Misc. Coll .. no. 

200, p. 5. 

1867. Venericardia m.ooreana Conrad, Am. Jour. Conchobgy, 

vol. 3, p. 190. 

1867. Venericardia densata Conrad, Am. Jour. Conchology, vol. 

3, p. 190. 

1890. Cardita (Venericardia) densata Conrad. DeGregorio, 

Monographie dele faune eocenique d' Alabama, p. 214, 

pl. 32, fig. 11. 

1891. Cardita densata Conrad. Heilprin, Acad. Nat. Sci. P\iladelphia Proc. for 1890, p. 402. · 

1891. Venericardia rnooreana Conrad? Heilprin, Acad. Nat. Sci. 

Philadelphia Proc. for 1890, p. 402. 

L894. Cardita dorsata Conrad (obviously intended for densata). 

Cossmann, Notes comph~mentaires sur le faune eocenique 

· d' Alabama, p. 14. 

1896. Cm·dita densata Conrad. Harris, Bull. Am. Paleontohgy, 

vol. 1, no. 4, p. 58. Not Card ita densata Conrad. 

Harris, Arkansas Geol. Survey, Ann. Rept. for 1892, 

vol. 2, p. 150, 1894. 

1896. l'"enericardia mooreana Conrad. Harris, Bull. Am. Pal~ontology, vol. 1, no. 4, p. 58. 

1897. Cardita densata Conrad. Harris, Bull. Am. Paleontohgy, 

vol. 2, ·no. 9, pp. 54, 55. 

1901. Venericardia densata Conrad. Cossmann, Soc. geol. 

France, Bull., 4e ser., vol. 1, pp. 652-656, 2 text figf. 

1903. V enericardia densata Conrad. Dall, Wagner Free Inst. 

Sci. Trans., vol. 3, pt. 6, pp. 1420-1422. 

1903. V enericardia .mooreana Conrad. Dall, Wagner Free In st. 

Sci. Trans., vol. 3, pt. 6, p. 1422. 

1919. Yenericardia "densata" Conrad. Harris, Bull. Am. Paleontology, vol. 6, no. 31, p. 77. 

1919. v·enericardia rnooreana Conrad. Harris, Bull. Am. Pabontology, vol. 6, no. 31, p. 77. 

1922. Venericardia densata Conrad. Woods, ·Geology of north .. 

west Peru, p. 69, 70. 

1925. Cardita densata Conrad. Abrard, Le Lutetien du bassin de 

Paris, pp. 45Q-451. 

1930. Venericardia densata Conrad. Stewart, Acad. Nat. Sci. 

Philadelphia Special Pub. 3, pp. 154, 157, 158. 

1930. Yenericardia rnooreana Conrad. Stewart, Acad. Nat. 

Sci. Philadelphia Special Pub. 3, p. 158. 

I I; 

I: 
190 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

1933. Venericardia densata Conrad. Plummer, Univ. Texas 

Bull. 3232, p. 625. 

1936. Venericardia densata Conrad. Rutsch, Eclogae geol. 

Helvetiae, vol. 29, pp. 163, 164, 170, 180. 

1936. Venericardia mooreana Conrad. Rutsch, Eclogae geol. 

Helvetiae, vol. 29, pp. 161, 164. 

Obliquely cordate, ventricose, thick, with about 25 flattened 

costae, obsolete. toward the base, narrow, profound, elevated and 

crenulated on the umbo; umbo very prominent at the apex; 

anterior basal margin obliquely subtruncated; posterior extremity 

truncated, direct; cardinal area very thick, and dilated, the teeth 

oblique. Height 1% inches, length thE' same. 

Locality.-Claiborne, Ala. 

This pretty species abounds in ent~re specimens in the argillaceous stratum near low-water mark in the Claiborne Bluff. I 

found none in the upper beds. Compared with V. planicosta, 

it is much smaller, comparatively shorter, thicker, and may 

always be readily distinguished by the crenulated ribs on the 

umbo.-Conrad, 1846. 

Venericardia densata is a heavy, dwarfish shell with 

an average of 26 or 27 ribs, which become obsolete 

toward the ventral margin. The umbonal sculpture is 

very characteristic. The extreme tips of the umbones 

are sculptured with very narrow, sharply serrate ribs. 

When the shell is 2 or 3 millimeters high, the ribs upon 

the anterior and medial portions of the disk become 

shouldered on either side. These shoulders are smooth 

and horizontal and wedge out dorsally but broaden 

away from the umbones and overhang the interradials. The serration is continued as a broad and 

regular noding for usually a third to half the distance 

from the umbones to the ventral margin of the adult, 

where it disappears rather abruptly. The ribs on the 

later half of the shell are broad, flat-topped, and 

regular, except upon the posterior area, and are separated by little more than linear intercostals. The 

overhang that is so prominent upon the medial portion 

of the disk becomes less and less and disappears altogether near the ventral margin. 

Venericardia densata is the most widely distributed of 

the Claiborne planicosta group and is abundant from 

Alabama to Mexico. 

In 1867 Conrad described Venericardia mooreana 

from the Texas Eocene. His description read, "Cordate, thick, ventricose; ribs 27 or 28, flattened on the 

back, prominent, square, broader on the back than 

beneath, or the intersections are narrowed at the surface by a slight lateral carination of the ribs; ribs 

prominent on the ventral margin; narrow, close, and 

prominent on the anterior and posterior slopes; crenulated on the beak and umbo. Length 1~ inches." 

The only reference to a type locality is "Texas. Dr. 

Franc.is Moore. Eocene." He continued: "Distinguished from planicosta and densata by its size, by the 

prominence of the ribs on the margin of the valves and 

on the anterior and posterior slopes, and by the interior 

n1arginal teeth, which are not carinated on the margins." 

Although it would be difficult from the description 

given to say positively that this species is conspecific 

with his earlier form, V. densata, no forms approaching 

the description of V. mooreana, other than V. densata, 

have been found in Texas. 

Cossmann in 1901 compared V. densata with the 

V. planicosta of the Paris Eocene, pointing out the dissimilarities, and proposing to call all the American 

forms by Conrad's name. He disregarded the earlier 

descriptions of V. regia and V. ascia. Dall, in 1903, did 

not seem sure whether or not the American species 

could be specifically distinct from the French forms, 

and he held that there was some justification in retaining the Lamarckian name for the American f'~ well as 

the European forms. Stewart in 1930 said of this 

distinction of Cossmann: 

For those who wish to separate the forms, on geographical 

grounds at least, the name V. ascia has priority over V. densata. 

I shoulsl perhaps use the name V. ascia for the American forms 

and hold that the burden of proof rested upon those who claimed 

it was identical with V. planicosta. This is the attitude usually 

taken· for c1osely related forms which are widely separated 

geographically. * * * 

This common densata is probably the lower Claiborne 

descendant of the smithii stock of the Midway and 

Wilcox. It is closely related to the larger aposmithii 

form of the lower Wilcox, the sculpture and g1~neral rib 

characters of the two forms being very similar. 

Rather small and compressed venericards from Hays 

Creek at Bedsole's old mill, on the road fron1 Elba to 

Kinston, one of the very few Tallahatta outcrops from 

which fossils have been recovered, may be early densata, 

but the forms are too poorly preserved for definite 

determination. They differ from the Lisbon Landing 

individuals in their more compressed and thinner shells. 

The species as it occurs in Alabama, though varying 

widely in size, shape, and rib count, presents an ensemble of characters which is unusually diagno1tic. It is 

abundant and with ·ostrea sellaeformis makes one of the 

best horizon markers in Alabama of the Lisbon formation. In Mississippi, at least so far as repre:;'ented in 

our collections, the species is for the most part rare or 

poorly preserved. At a bluff on the Chickasawhay 

3 ~ miles southeast of Quitman the species is fairly 

common, but it is thinner-shelled and more inflated 

with a slightly higher rib count than in the usual 

run of the Li~bon and lower Claiborne Bluff individuals 

on the Alabama River. The St. Maurice of Louisiana 

is not adequately represented in the collections that 

we have studied, and it is probable that the species is 

fairly widespread on the east side of the Sabine uplift. 

In Texas it is widespread and in many localities abundant. A number of variations are manifested both in 

the Weches faunas and in those of the Cook ~fountain, 

but we have been unable to use these variations as a 

stratigraphic criterion. The common form in northeastern Texas, both in the W eches around Palestine, 

Elkhart, and Augusta and in the Cook Mountain along 

Cedar Creek near Wheelock, is a smallish roundish cor-
SYSTEMATIC DESCRIPTIONS 191 

date species with broad, rather low radials. This was 

almost certainly the race that Conrad had before him 

when he described his mooreana. The same' type occurs 

at Mosleys Ferry on the Brazos River, but at Smithville the only individuals which we have studied are 

compressed, moderately large, and high cordatetrigonal forms with a partly obsolete decoration upon 

the ribs of the umbones. A cordate-quadrate, rather 

highly inflated little individual from Lee County, with 

uncommonly low and broad· ribs, is doubtfully referred 

to densata. Venericardia densata is common in the 

outcrops along the highway between Jourdanton and 

Pleasanton, in Atascosa County, and the form is similar to those in northeastern Texas. The concentric 

imbrication is unusually sharp on many of the individuals from these localities. The faunas of the Rio 

Grande embayment offer the widest range of variation 

and follow. more closely the lines of variation of the 

Alabama forms. In the lower Cook 1\tlountain in 

northern Webb County they are relatively large and 

coarse, with strongly decorated umbonal ribs. This is 

the race too that is commonly present in the faunas at 

the horizon exposed in Arroyo Chacon near Laredo. 

At Arroyo Valeiio, 3}~ miles southeast of Zapata, in 

Zapata County, there is another small variant, smaller 

even than those so commonly present in northeastern 

Texas but more cordate and n1ore compressed. We 

have them from tlll.s one locality only, and only in the 

form of double valves. Later material with good 

hinges may prove these forms to be new. 1\tfolds of 

small double valves which like those from Arroyo 

V alefio are 2 to 3 centimeters high but with more highly 

decorated ribs occur near China, Carlos Cantu, Nuevo 

Le6n, Mexico. This horizon is appreciably lower than 

that represented in Arroyo Valeiio, and it is quite 

possible that the China forms may be related to the 

rotunda group rather than to densata. Other not very 

well preserved individuals closely resembling the densata 

of Arroyo Chacon have been recovered from the lower 

Cook Mountain near China and near Doctor Coss, in 

Nuevo Le6n. In both these localities the venericards 

are associated with Ostrea sellaeformis. 

Well-preserved typically sculptured densata can be 

determined with more assurance than almost any 

other species, but there are variants which make it 

easily confusable with V. claiboplata. There is appreciable variation in the thickness of the shell and in 

its convexity, and the ribs in the umbonal region are 

decorated with a beaded crest that varies in relative 

width. If these crests are relatively narrow and the. 

ribbing not entirely exposed, they simulate the narrow 

serrate ribbing of the earlier stages of claiboplata. 

Ordinarily, however, claiboplata is a larger, thinner, 

more inflated shell with numerous ribs serrate on the umbones, but simple in the late adolescent and adult stages. 

Distribution: 

Claiborne group: 

Lisbon formation: 

Alabama, Monroe County, 2668, 3105, 5511, 1 

mile below Lisbon Landingt>r, Alabama Piver, 

263, 274, 2396, 6086, 1217, 13086; base of 

Claiborne Blufft>r, Alabama River. C'arke 

County, 278, 2870, Coffeeville c; 6157°, 1 mile 

southwest of Rockville. Choctaw County, 

7882t>, Okatuppa Creek half a mile f',bove 

crossing, 1~ miles north of Barrytown; 7887t>, 

Little Turkey Creek crossing on roll.d to 

Cullom burg. 

fWautubbee formation: 

Mississippi, Clarke County, 2627t>, Chickasawhay River, 3~i miles southeast of Quitman. 

tSt. Maurice· formation: 

Louisiana, Winn Parish, 2916t>, Saline P.<1you 

near St. Maurice. Webster· Parish 1f059t>, 

2 miles southeast of Minden. 

Mount Selman formation, Weches greensand member: 

Texas, Sabine County, 13158t>, 2 ± miles above 

Good,vin Ferry; 11106P, Dillon Shoalrr 3* 

miles south of Lows Creek, Sabine P.iver. 

San Augustine County, numerous locr.lities 

along the Nacogdoches-San Augustine road 

between Attoyac Bayou and San Aug·mtine. 

Nacogdoches County, 13057t>, west bank of 

Attoyac Bayou on the road from Chire:'lO to 

the town dump. Anderson County, 2154t>, 

Colgins Hill, 1 mile south of Palestine; 1Q<>,52v, 

cut in Boston road, 1V2 miles southea~t of 

Palestine; 9259t>, 9260P, three-quarters of a 

mile south of Elkhart; 9262t>, 1 mile south of 

Elkha.rt. Houston County, 9255t>, Percilla; 

9269t>, Augusta. Leon County, 13058t>, half 

a mile east of Robins on Centreville road. 

Lee County, 5283t>, Shaw's Branch, 17~ miles 

southwest of Lexington; 2133t>, and 7564t>, 

early collections from the county but no 

definite locality. Bastrop County, 5285P, 

6088P, 8810r, Colorado River near Smithville; 

5265r, and 5284r, near the county line in the 

southernmost part of Bastrop County. 

Cook Mountain formation: 

Texas, Robertson County, 2048t>, Montgomery's 

well, half a mile east of Wheelock; 2065t>, Collardstown Branch; (no number)t>, Wheelock. 

Brazos Cou~ty, 4786t>, 5473t>, 10343P, Mor~ley's 

Ferry, west bank of Bra.zos River near Stone 

City. Gonzales County, 4047?, well at Gonzales. Wilson County, 6141r, Bluff on San 

Antonio River 4 miles south-southea,st of 

:Floresville. Atascosa County, 6152t>, crossing of creek on Pleasanton-Jourdanton road 

about 1 H miles southwest of Pleasanton; 

8870t>, a quarter of a mile northwe~t of 

Jourdanton; 13056t>, 1 mile east of Jourdtt.nton 

on the Pleasanton road. La Salle Co'~nty, 

9168v, International-Great Northern F .. R. 

near milepost 350, south of Cotulla; f6Q2c, 

deep well 1 mile west of Fowlerton, 80~-823 

ft. Webb County, 9166t>, 5 miles nor~h of 

Laredo in bottom of arroyo; 7491°, 11 miles 

west of Espejo ranch; 10745t>, 2112°1 Arroyo 

Chacon, near Laredo; 7492t>, east side of 
192 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

arroyo, 1 mi1e east of Laredo; 8771P, 4 miles 

southeast of Laredo. Zapata County, 8836 P 

and 8837P, just above mouth of Arroyo El 

Burro, south of Jabali ranch; 9104°1 4 miles 

northeast of Zapata; 9117P, 3 miles southeast 

of Zapata on Roma road; 13170c, Arroyo 

Vele:fio, 3}~ miles southeast of Zapata, 1 mile 

above Laredo-Roma highway bridge. 

Venericardia (Venericor) zapatai Gardner and Bowles, n. sp. 

Plate 45, figure 17 

Shell moderately large and solid; ovate-cordate in 

outline; rather strongly, broadly, and evenly inflated 

in the umbonal region. Lunule small, deeply sunken. 

Anterior margin strongly bowed in front of the lunule, 

rounding obliquely into the ventral margin, which is 

straight medially but rather abruptly up-curved into 

the obliquely produced and truncate posterior margin. 

Posterior area indicated by a flattening of the shell and 

by sculpture differenees, but not sharply cut off from 

the disk. Tips of umbones very full and proximate, 

the ribs exceptionally high and narrow and probably 

sharply serrate. Radials 19 or 20 upon the anteromedial area, 5 or 6 upon the posterior region, total 25 

on the holotype; juvenile and adolescent ribs very 

high and narrow, gradually broadening and on the 

fully adult appearing as low, broadly rounded ribs 

separated by very narrow, almost linear intercostal 

grooves. Incremental striae laminated and crowding 

into prominent resting stages near the ventral margins 

of the older individuals. Ligament marginal, probably 

unusually powerful. Hinge characters very imperfectly 

preserved; hinge plate high and narrow. Characters 

of the interior lost or concealed. 

Dimensions of holotype: Height 68 millimeters, 

width 62 millimeters, convexity 42 millimeters. 

Holotype, geodic double valves: U. S. National 

Museum, no. 372692. 

Type locality: Geological Survey station 9109, 4.8 

n1iles southeast of Zapata on Roma road, Zapata 

County, Tex. Claiborne group, Cook Mountain 

formation. 

Venericardia zapatai is characterized by the high, 

'trigonal-cordate outline and the relatively few apparently simple ribs, persistent to the basal margin. 

The mechanics of the hinge must have been unusually 

well developed, for several individuals are preserved in 

the form of geodic double valves, indicating that they 

were laid down in quiet water and so quickly buried 

that the silty sand did not penetrate the interior. 

Later there was solution and recrystallization of the 

calcite over the entire inner surface. 

Inner molds of double valves occurring con1monly 

about a n1ile southeast of Mier n1ay very well be 

referable to this speeies. They are badly warped, 

however, and not suffieient characters are preserved 

for specific determination. . 

Distribution: 

Claiborne group, Cook Mountain formation: 

Texas, Zapata County, 9109°, 4.8 miles s-mtheast of 

Zapata on the Roma road. 

Mexico, Tamaulipas, Chillipin Arroyo, 7.9 miles from 

Roma on the Mier roadc. 

Venericardia (Venericor) apodensata Gardner and Bowles, n. sp. 

Plate 37, figure 13; plate 43, figure 8; plate 45, figures 15, 16 

Shell of mediun1 size for the group, inflated, rounded 

to cordate-trigonal in outline. Anterior margin broadly 

arcuate, merging into the upcurved base, the posterior 

margin obscurely truncate. Umbones prominent, full 

and high, the tips turned inward and forward over the 

small, relatively high, and deeply incised lunule. Posterior area defined both by the flattening of the shell 

and by the more cordate and incrementally wrinkled 

costals. Umbonal ribs high and narrow, with sharply 

noded crests and lateral terracing, strongest anteriorly 

and evanescing in the adolescent stage; adult sculpture 

of 23 high anteron1edial ribs, wider than tl'~ deeply 

incised intercostals and distinctly continuous to the 

ventral margin, .and on the posterior area 9 cordate 

costals. Ligament marginal, inset on a narrow nymph. 

Hinge plate wide and moderately low. Anterior right 

cardinal very short and laminar, medial cardinal cuneiform and bent forward near the u1nbonal extremity, 

posterior cardinal laminar and much producei parallel 

to the ligament groove; anterior left eardinal short and 

deltoid, the posterior bent forward obliquely and 

expanded toward the ventral extremity. Pedal scar 

deeply incised. Adductor muscle scars large and 

prominent, because of the slight thickening in the adult 

over the area of the adherent mantle. Pallial line 

simple. Inner margins crenate. 

Dimensions of cotypes: Ootype 369599, left valve, 

height 51 millimeters, width 51 millimeters. Cotype 

136644, right valve, height 68.0 millimeters, width 70.5 

millimeters. 

Cotypes: A left valve, U. S. National Museun1, 

no. 369599, and a right valve, U.S. National Museum, 

no. 136644. 

Type locality: Geological Survey station 6462, 

Moodys Branch, Jackson, Hinds Count~.,., Miss. 

Moodys marl men1ber of Jackson formation. 

The types are not fully adult, and the o~der individuals are n1ore trigonal and their hinge plates higher. 

Venericardia apodensata may be in the line of descent 

from V. densata, so common and so widespre".d in the 

Claiborne. The Jackson species is a larger but not so 

heavy shell, with a lower and not so heavy hinge plate 

and a more sharply defined and deeply inciEed costal 

sculpture. It is quite possible that a later~l line is 

represented, for Venericardia densata sugge<;lts more 

strongly the last of the line than an ancestral form. 

The early stages of the Claiborne and J ackscn speeies 

are, however, very similar, and there is pro btl bly some 

·, 
SYSTEMATIC DESCRIPTIONS 193 

genetic relationship. Fron1 Venericardia klimacodes of 

the Yazoo clay member, apodensata differs in the lower, 

less inflated umbones, the 1nore angular ribbing, and 

the more pronounced and more persistent lateral terracing. These differences have apparently a stratigraphic significance. 

Distribution: 

Jackson formation, Moodys marl member: 

Alabama, Clarke County, 7158P, 2-2~ miles southwest of Whatley; 6157P, 1 mile southwest of Rockville. 

Mississippi, Clarke County, 330P and 2630P, 4~ miles 

northeast of Shubuta. Hinds County, 54P, 61P, 

62P,2665P,3735P,3746P1 4250P,6458P1 6462P1 7386P1 

Moodys Branch, Jackson; 3734e, south of pump 

house, Jackson; 12178e, gully south of the road 

east of flag station on Yazoo & Mississippi Valley 

Railroad. 

Arkansas, St. Francis County, 4266e, Little Crow 

Creek, a quarter of a mile above Choctaw Bridge, 

Crowleys Ridge near Forrest City. Jefferson 

County, 2402e, White Bluff, Arkansas River. 

Cleveland County, 2231P, 2413P, Rison. Drew 

County, 2408r, Long Prairie, 9998P, Tennessee 

Spur, SW~SE%, sec. 30, T. 12 S., R. 7 W. Bradley 

County, 2411P, 3 miles east of Warren. 

Louisiana, Claiborne Parish, 2038P, Pittmans Mill, 

SW%,SE7~ sec. 19, T. 19 N., R. 7 W. Louisiana 

Meridian. Bienville Parish, 2033P, Holstun's 

place, sec. 17, T. 18 N., R. 5 W. Louisiana Meridian. Grant Parish, 2003P, 2638P, 4270P, and 

13085P, Creole Bluff, a quarter to a half mile below 

the Ferry Landing, Montgomery; 4271P, Bells 

·wood Landing, Red River 4 miles below Montgomery. 

Texas, Sabine County, 10742P, Sabine River, Robinson's Ferry, 2 miles north of Fairdale. 

Venericardia (Venericor) klimacodes Gardner and Bowles, n. sp. 

Plate 37, figures 9, 10 

Shell rather small for the group, light, only slightly 

inflated, ovate-trigonal in outline. Anterior margin 

broadly rounded, merging into the upcurved base. 

Posterior curvature n1ore decided. Un1bones high, 

narrow, the tips turned inward and forward oyer the 

small and deeply sunken lunule. Posterior area indicated by the flattening of the shell and by sculpture 

differences. Ribs 23 on the anter01nedial portion, 6 on 

the posterior; high, narrow, and noded on the umbones, 

flat-topped, and separated by deeply incised, sharpangled intercostals that continue distinct to the ventral 

margin of the disk; lateral rib lets well defined in the 

early and adolescent stages; posterior costals cordlike, 

those nearest the margin flattened and overridden by 

the incrementals, forn1ing a sort of false escutcheon. 

Ligament marginal, deeply inset. Hinge plate rather 

high and narrow. Anterior right cardinal very short 

and thin, the middle cardinal scimitar-shaped, the 

posterior slender and produced parallel to the ligament 

groove; anterior left cardinal short and wedge-shaped, 

the posterior slender and produced. Pedal scar s1nall 

and sunken; anterior adductor scar narrow, distinct, 

the posterior sen1i-elliptical and placed well down 

toward the ventral margin. Pallial line simple and 

well defined. Inner margins deeply crenate. 

Dimensions of holotype: Height 53 millimeters, 

width 49 millimeters, convexity of single valve 16 

millimeters. · 

Holotype, a left valve: U.S. National Museum, no. 

372693. 

Type locality: Geological Survey station 64 72, lr.rge 

ravine about 1 mile south of yazoo City, Yazoo County, 

Miss., along street-car line about a quarter of a 1nile 

north of the tile plant and just below the old reserYoir. 

The most closely related species is Venericardia 

apodensata, fron1 the Moodys marl. From that form 

Venericardia klimacodes is separated by its less inflated, 

usually smaller shell, more sharply incised intercost~.ls, 

and stronger and more persistent lateral terracing. 

V. klimacodes is restricted in its known distribution to 

the Yazoo Clay. 

Distribution: 

Jackson formation, Yazoo clay member: 

Mississippi, Yazoo County, 10118P, near the l·0ad 

of a ravine about three-quarters of a mile so·~theast of Free Run on the line between the SEX 

sec. 26 and the SWX sec. 25, T. 13 N., R. 1 W., 

about 10 miles northeast of Yazoo City; 7674P, 

roadside on hill at Sims station, Yazoo & Mi"l~issippi Valley Railroad, 10 miles north of Yazoo City 

and 2 miles south of Eden; 6474P, 1~ miles east of 

the Yazoo & Mississippi Valley Railroad station 

in the banks of a creek south of Broadway-Benton 

road; 6472e, 1 mile south of Yazoo City, along 

street-car line about a <}Uarter of a mile north of 

the tile plant and just below the old reservoir. 

V enericardia, n. sp. 

At two localities in the upper Eocene of northern 

Mexico remnants of a large venericard have been found 

which indicate a species quite unlike any now recognized 

in the Gulf. The shells are large, about 110 millimeters 

high and 90 millimeters wide, but the double valves 

are less than 50 millimeters in maximum thickn~ss. 

The lateral margins are broadly curved, and so is the 

base line. The umbones are low, broad, and placed 

well in front of the median horizontal. The characters 

of the young and adolescent sculpture have been lost, 

but the adult ribs are low, apparently simple, wider 

on the disk than the U-shaped intercostals, probably 

about 20 in all, and evanescent at a considerable distance fron1 the margins. The growth wrinkling toward 

the anterior and ventral margins is unusually strong and 

regular. The ligament seems to have been very pO'\Ferful, and the hinge high and massive. 

There is nothing remotely resembling these rounded, 

compressed, and few-ribbed forms in the Jackson of 

the Gulf. 
194 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

Venericardia (Venericor?) greggiana Dall 

Plate 46, :figure 9 

1897. Venericardia alticostata var. Harris, Bull. Am. Paleontology, vol. 2, no. 9, p. 55, pl. 11, :fig. 1. 

1903. Venericardia greggiana Dall, Wagner Free Inst. Sci. Trans., 

vol. 3, no. 6, p. 1425. 

Shell large but relatively thin, with high beaks, but the line 

of the inner margins suborbicular; the ribs are narrow and high, 

about 34 in number, flattish above and even overhanging a little 

laterally, with flat, dentiform imbrications directed toward the 

umbones; the interspaces are subequal or slightly narrower than 

the ribs and channeled. The ribs in the young shell are accompanied by a narrow, elevated riblet on each side, but the adult 

has the posterior riblet generally obsolete toward the ends of the 

shell and both riblets obsolete in the middle of the disk below; 

the beaks are prosogyrate, the lunule small and convex, the 

hinge rather light, and the inner margin sharply crenulate. It 

reaches a maximum height of 55 millimeters and a diameter of 

36 millimeters. 

Lower bed at Greggs Landing, Ala., in the Chickasawan or 

Lignitic stage of the Eocene. 

This form is rarely well preserved, but the sculpture, when 

perfect, is a clue to differentiate it from any other of our Tertiary species. It has a general resemblance to TT. smithii Aldrich, 

but is without the rostration or the minor sculpture of that 

species.-Dall, 1903. 

This species is unusually well characterized by its 

subglobose outline and elaborate sculpture and is 

geneticallyrelated to the V.smithii stock of the Midway; 

for that reason it is included under Venericor, although 

in general appearance it is far removed from the usual 

concept of that group. It has been recognized only 

in the Tuscahoma of Alabama. 

Distribution: 

Wilcox group, Tuscahoma sand:. 

Alabama, Monroe County, 5604P, Greggs Landing, 

Alabama River; 3908 r, Bells Landing, Alabama 

River. 

V enericardia (Venericor?) mingoensis Gardner and Bowles, n. sp. 

Plate 46, :figures 2, 3 

1936. Venericardia mingoensis Gardner and Bowles. Cooke, 

U.S. Geol. Survey Bull. 867, p. 44. 

1936. ? Venericardia "planicosta" Cooke, U. S. Geol. Survey Bull. 

867, pp. 43, 47, 49, 50, 51. 

Shell small for the group but rather heavy, high, 

rounded-trigonal in outline, compressed. Umbones 

small and pinched but full at the tips, submedial, prosogyrate. Margins broken but indicated by the incremental lines, the anterior and ventral margins broadly 

rounded, the posterior area sharply defined, and the 

margin probably obliquely truncate. Anterior area 

indicated by a very prominent, sharp, and regular corrugation of the 10 anterior ribs, the 10 upon the disk broad 

and flat and separated by deeply incised linear channels; 

the 6 posterior ribs much narrower, though apparently 

similar in character and persistence to those upon the 

disk. Hinge plate high; dentition very imperfectly 

indicated. Muscle scars deeply impressed, especially 

the anterior adductor and the pedal pit directly above it. 

Dimensions of holotype: Height 50.0±millimeters, 

width 45.0±millimeters, convexity 20.0±millimeters. 

Holotype, a right valve: U.S. National Museum, no. 

372922. 

Type locality: Geological Survey station 3981, Black 

River, Rhems field, near store, about 1 mile west of 

Steamboat Landing, Georgetown County, E. C. Collected by Frank Burns in 1904. Possibly from the 

undifferentiated Midway group. 

So imperfect a specimen would not deserve a name 

were it not for the very unusual characters Y'hich even 

the battered and worn holotype presents. T~,~ narrow, 

pointed beaks, the simple ribs, so strongly corrugated 

on the anterior portion of the shell, so flat r.nd closely 

spaced medially, so narrow but persistent posteriorly 

are uncommonly good diagnostics of a speci€.s collected 

more than 30 years ago and not observed in any subsequent collection. 

Venericardia mingoensis stands quite apart from all 

described species in the narrow, pinched umbones, the 

strongly corrugated anterior area, the narro"'V, sharply 

distinct posterior area, and the broad, simi= le, regular 

ribbing on the central portion of the disk. There is 

something in the general look of the pinched un1bonal 

region and the sculpture pattern that Sltggests V. 

hijuana, and it may be that a genetic relationship is 

thus faintly indicated. The Black Mingo formation, 

from which the shells were recovered, has beBn referred 

on field evidence to the Wilcox. The fossils indicate a 

lower Midway age. 

Distribution: 

Midway group, probably the lower Midway, undifferentiated: 

South Carolina~ Georgetown County, 7~*l9 r, Black 

River 12 miles northwest of Georgetown; 3481 r, 

Black River 1 mile west of Steamboat Landing. 

Subgenus GLYPTOACTIS Stewut 

1930. Stewart, Gabb's California Cretaceous and Tertiary type 

lamellibranchs: Acad. Nat. Sci. Philadelphia Special 

Pub. 3, pp. 151-152. 

Type by original designation: Venericardia hadra Dall. Lower 

Miocene (Chipola formation) of Florida. 

The American Miocene Venericardia are not so high as the 

typical or Venericor or Leuroactis. For this group the new subgeneric name Glyptoactis is proposed, with V. ha.dra. Dall as the 

type species (Dall, 1903, p. 1429, pl. 53, :figs. 11, 13, Chipola). 

The species differ from the typical in having a curred elongate 

right cardinal and a small anterior pustule or lateral. The right 

hinge of a closely related species has been figured by Dall (1903, 

p. 1430, pl. 53, :fig. 12), a:q.d his figures of both species have been 

reproduced by Gardner (U. S. Geol. Survey Prof. F>'.per 142-B, 

1926, p. 90, pl. 17, :figs. 11-13). The group is known from the 

Eocene--V. alticostata (Harris, Bull. Am. Paleontclogy, vol. 6, 

1919, p. 82, pl. 30, :figs. 1-5, Claiborne)-and is still living on the 

West Central American coast as V. cuvieri Broderip (Reeve, 

Conch. Iconica, vol. 1, 1843, pl. 5, :fig. 24, Cardit('.). Judging 

from the figures, V. acuticostata from the French Eocene is 

another member of this group (Coesmann and Pissarro, 1906, 

pl. 31, fig. 97-7, Lutetien-Bartonien). "Cardita" so.ndiegoensis 

from the Eocene of California may also be a Glyptoa~tis (Hanna, 
SYSTEMATIC DESCRIPTIONS 195 

California Univ. Bull. Dept. Geology, vol. 16, 1927, p. 283, 

pl. 37, fig. 1-2, 8-9). 

The hinge of Glyptoactis suggests ther minute Mediterranean 

Glans Megerle 1811 (Bucquoy, Dautzenberg, and Dollfus, Moll. 

Roussillon, vo1. 2, 1892, p. 231, pl. 38, figs. 21-25), which has 

more distinct laterals and a shorter right cardinal enlarged 

anteriorly. Were it not for the similarity of Glyptoactis with 

some of the species of Venericardia s. s., I should place Glyptoactis 

under Glans, but the resemblance may be fortuitous, and tempora'rily at least Glyptoactis is better left under Venericardia, since 

it is difficult if not impossible at the present time to recognize 

the two groups among immature Eocene specimens. These 

specimens may actually show the development of a su bg~mus, 

but such an interesting conclusion could only be accepted after 

a much more exhaustive study of them has been made.-

Stewart, 1930. 

The two species that follow, Venericardia hesperia 

and Venericardia moa, may be referable to this subgeneric group. Unfortunately, their hinge characters 

are little or not at all known. They are included in 

this study because of their possible relationship to some 

of the earlier, more generalized venericards. 

Venericardia ( Glyptoactis?) hesperia Gardner 

Plate, 46, figures 4, 5 

1896. Venericardia alticostata Conrad (part). Harris, Bull. Am. 

Paleontology, vo1. 1, no. 4, p. 57. Not Cardita alticostata Conrad, Am. Jour. Sci., 1st ser., vol. 23, p. 342, 

1833. 

1923. Venericardia alticostata subsp. hesperia Gardner, U.S. Geol. 

Survey Prof. Paper 131-D, p. 112, pl. 32, figs. 1, 2. . 

1933. Venericardia hesperia Gardner. Plummer, Univ. Texas 

Bull. 3232, pp. 547, 550. 

1935. Venericardia hesp8ria Gardner, Univ. Texas Bull. 3301, pp. 

157, 164-165. ' 

Shell of moderate dimensions, thick, porcelaneous, inflatedcordate in cross section; unbones prominent, wen rounded, 

slightly anterior in position; lunule very sma11, deep; anterior 

extremity strongly and evenly bowed in front of the lunule; 

posterior dorsal margin gently sloping, the posterior lateral 

margin obliquely truncate; base line feebly arcuate, strongly 

upcurved anteriorly, abruptly rounded posteriorly; general 

character of surface sculpture similar to that of V. alticostata 

s. s.; radials not far from 20 in number, normally tripartite on 

the anterior and medial portions of the shell, as in V. alticostata; 

crest of radials narrow and sharply serrate; lateral "terraces" 

well-defined; interradial channels broadly U-shaped; incremental 

sculpture very fine and sharp; hinge plate thick, heavy; adductor 

scars impressed, the anterior excavated; pallial line simple; 

inner margins deeply crenate. 

Dimensions: Altitude 37 millimeters, latitude 44 millimeters, 

diameter 37 mi11imeters. 

Type locality: Station 3180, bluff on Frio River half a mile 

below Myrick's apiary, Uvalde County [Texas].-Gardner, 1923. 

Although this form is undoubtedly much more closely 

allied with the V. alticostata group, it is included in this 

report, as it seems to be related to the earlier members 

of the planicosta group. It differs from V. moa in being 

more inflated and bearing more radials. 

Distribution: 

Midway group, Kincaid formation: 

Texas, Medina County, 10128?P, Verde Creek, 4~ 

miles northeast of Hondo; 6584P, . D'Hanisyancey road, about 7 miles south of D'Hanis. 

Uvalde County, 3181P, Frio River, just above 

water hole opposite apiary below Englem2 nn's 

ranch; 3180P, bluff on Frio River half a mile b~low 

Evans' (Myrick's) apiary. 

Venericardia (Glyptoactis?) moa Gardner 

Plate 46, figure 1 

1935. Venericardia rnoa Gardner, Univ. Texas Bull. 3301, pp. 

157, 168-169, 170, pl. 10, fig. 1. 

Shell rather small for the genus, transversely ovate in 

outline, not strongly inflated. Umbones anterior, the 

tips incurved and proximate. Characters of the lunule 

not preserved. Anterior margin bowed in front of the 

lunule. Posterior extremity obliquely produced and 

broadly rounded. Sculpture vigorous. Radials 1 P on 

the type-the 7 on the posterior slope less elevated than 

those upon the disk and mueh more crowded; tl'C\ 5 

anterior radials also erowded; the 7 radials upon the 

disk prominent and laterally terraced, with serrate 

crests. Charaeters of the hinge and muscle s~ars 

obscured by the mode of preservation. Inner vertral 

margins erenate. 

Dimensions of double valves of holotype from w:'lleh 

a part of the shell has been removed: Height 30.0 nllilimeters, width 34.0 millimeters, convexity 20.0. millimeters. 

Holotype, a pair of locked valves: U. S. National 

Museum, no. 370922. Allied form: U.S. National ~1useum, no. 370912. 

Type locality: Holotype, Geological Survey station 

4398, 18 miles south and east of Eagle Pass, Mave,rick 

County, Tex.; allied form, U.S. Geological Survey station 2439, 1 mile east of Webberville, Travis County, 

Tex. Midway 'group, Kincaid formation. 

The holotype is figured. 

Venericardia moa closely approaehes in some of its 

higher variants V. hesperia Gardner, so common on the 

Frio River in Uvalde County, Tex. It runs decid~dly 

smaller than V. hesperia, however, is normally much 

less inflated, and is more produced posteriorly. In 

general dimensions and outline it closely approaches 

V. whitei Gardner, but the radials are less cro"Tded 

upon the disk. The unnamed species from the l'~,sal 

greensands of north .and central Texas is doubtless 

closely related to it and may prove to be specifically 

identical, though the border form runs a little larger, 
196 THE VENERICARDIA PLANICOSTA GROUP IN THE GULF PROVINCE 

is n10re produced posteriorly, and apparently develops 

more radials upon the posterior and possibly the anterior 

area. 

Although this species is probably n1ore closely related to the V. alticostata group than to the planicosta 

strain, it has been included with V. hesperia, as it 

seems to fall between the two major Eocene types of 

the genus and to be a close approach to the rudimentary 

basal greensand form. 

Distribution: 

Midway group, Kincaid formation: 

Texas, Maverick County, 439811, 6583?11, and 1175311, 

Bibora Creek, just below Bibora tanL about 18 

miles southeast of Eagle Pass; 1175511, 3 miles north 

of Media tank; 1175711, hillside above small tank 2 

miles west of Lopez tank, about 29 miles southeast 

of Eagle Pass; 1186911, 1 mile northwest of Indio 

Wells; 6575, White Bluff on the Rio Grande, about 

4~ miles west of south of Windmill (J acal) ranch 

house. 
PLATES 33-46 

197 

2041:!-39--5 
PLATE 33 

[All figures natural size unless otherwise indicated] 

FIGURE 1. Yenericardia (Yenericor) mediaplata Gardner and Bowles, n. sp. (p. 168). Interior of holotype, a left valve (U. ~- N. M. 

137241) from Prairie Creek, Wilcox County, Ala. 

FIGURE 2. Yenericanha ( Vener·icor) nanaplata Gardner and Bowles, n. sp. (p. 169). Exterior of holotype, a left valve (U. S. N. M. 

137226) from Nanafalia Bluff, Tombigbee River, Ala. 

FIGURE 3. Yenericanlia (Yenericor) m.ediaplata Gardner and Bowles, n. sp. (p. 168). Exterior of holotype, a left valve (U. S. N. M. 

137241) from Prairie Creek, Wilcox County, Ala. 

FIGURES 4-5. 1,.-ene?'icardia (Fenericor) nanaplata nanna Gardner and Bowles, n. subsp. (p. 169). Cotypes (U. S. N. M. 373028) 

from Greggs Landing, Alabama River, Ala. 4, Exterior of left valve; 5, exterior of right valve. 

FIGURE 6. "Venericardia (Fenericor) negr1"tensis Olsson (p. 170). Exterior of holotype, a left valve, from Negritos, Peru; height 76.0 

millimeters; width 70.0 millimeters. (After Olsson.) 

FIGURE 7. l,..enericardia (1'"enen:cor) nanaplata Gardner and Bowles, n. sp. (p. 169). Interior of holotype, a left valve (U. S. N. M. 

137226) from Nanafalia Bluff, Tombigbee River, Ala. 

FIGURE 8. Venericardia (l'"enericor) hatcheplata Gardner and Bowles, n. sp. (p. 172). Exterior of cotype, a right valve (U.S.N. M. 

372173) from Hatchctigbee Bluff, Tombigbee River, Ala. 

FIGURE 9. l.,.enericm·dia (Yenericor) bashiplata Gardner and Bowles, n. sp. (p. 171). Exterior of cotype, a left valve (U.S. N. M. 

371914) from Beaver Creek a quarter of a mile east of Choctaw Corners, Clarke County, Ala. 

FIGURES 10-11. Yener·icardia (Yenen'cor) nanaplata narma Gardner and Bowles, n. subsp. (p. 169). Cotypes (U.S.N. M. 373028) 

from Greggs Landing, Alabama River, Ala. 10, Interior of left valve shown in figure 4; 11, interior of right 

valve shown in figure 5. 

FIGURE 12. Fener·icardia CVenericor) hatcheplata Gardner and Bowles, n. sp. (p. 172). Exterior of cotype, a left valve (U. S. N. M. 

372173) from Hatchetigbee Bluff, Tombigbee River, Ala. 

198 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 33 

2 

3 

6 7 8 

10 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUP. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 34 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUP. 
PLATE 34 

FIGURES 1-2. Venericardia (Venericor) hatcheplata Gardner and Bowles, n. sp. (p. 172). Cotypes and abnormal left valve (U. S. N. M. 

372173) from Hatchetigbee Bluff, Tombigbee Ri vcr, Ala. 1, Interior of left valve, shown on plate 33, figure 

12; 2, interior of right valve, shown on plate 33, figure 8. 

FrGURES 3- 6. Venericardia (Venericor) bashiplata Gardner and Bowles, n. sp. (p. 171). Cotypes (U. S. N. M. 371914) from locality 

a quarter of a mile east of Choctaw Corners, Clarke County, Ala. 3, Interior of left valve (cotype); 4, 

interior of abnormal left valve showing dentition apparently normal to right valve; 5, interior of normal 

right valve (cotype); 6, mirror image of interior of abnormal left valve shown in figure 4. 

199 
PLATE 35 

FIGURES 1-2. Venericardia (Venericor) planicosla Lamarck (p. 168). Subgenotype (U. S. N. M. 12704) from Grignon, Seine et 

Oise, France. 1, Interior of left valve; 2, interior of right valve. 

FIGURES 3-7. Venericardia (Venericor) ascia Rogers (p. 171). 3, Holotype of Venericard·ia marylandica Clark and Martin, from the 

Woodstock greensand marl member of the Nanjemoy formation, 2% miles above Popes Creek, Potomac 

River, Md. Interior of right valve: Height 80.0 millimeters, width 80.0 millimeters. (After Clark and 

Martin.) 4, Profile of double valves of holotype of Venericardia ascia Rogers from King George County, 

Va. (After Rogers.) 5, Exterior of right valve of holotype of Venericardia marylandica Clark and Martin 

shown in figure 3 (after Clark and Martin); 6, interior of right valve of holotype of Venericardia ascia Rogers 

from King George County, Va. (After Rogers.) 7, Exterior of right valve of holotype of Venericardia ascia 

Rogers shown in figure 6. (After Rogers.) 

200 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 35 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUP. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 36 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUP. 
PLATE 36 

FIGURES 1- 2. Venericardia (Venericor) claiboplata Gardner and Bowles, n. sp. (p. 173). Cotype (U.S.N. M. 11365) from Claiborne 

Bluff, Alabama River, Ala. 1, Exterior of right valve ; 2, interior of right valve. 

FIGURES 3-4. Venericardia (Venericor) claiboplata Gardner and Bowles, n. sp. (p. 173). Co type (U. S. N. M. 1434) from Clarksville, 

Clarke County, Ala. 3, Interior of left valve; 4, exterior of left valve. 

FIGURES 5- 6. Venericardia (Venricoer) planicosta Lamarck (p. 168). Subgenotype (U. S. N. M. 12704) from Grignon, Seine et 

Oise, France. 5, Double valves viewed from the front; 6, exterior of left valve. 

201 
PLATE 37 

FIGURES 1-3. Venericardia sp. cf. V. (Venericor) diga Gardner and Bowles, n. sp. (p 182). Two pairs of locked valves (U.S.N. M . 

497005), from Rio Alamo, west of Mier, Tamaulipas, Mexico. 1, Double valves viewed from the left; 2, 

double valves viewed from the front; 3, double valves (second pair) viewed from the left. 

FIGURES 4-5. Vener·icm·dia (Venericor) cacamai Gardner and Bowles, n. sp. (p. 174). Cotype, an incomplete left valve (U.S.N. M. 

373032), from Zacate, Nuevo Leon, Mexico. 4, Hinge of incomplete left valve; 5, exterior of incomplete 

left valve. 

FIGURE 6. Venericardia (Venericor) restinensis Olsson (p. 174). Exterior of holotype, a right valve, from the Pozo Valley, Restin 

formation, Peru; height 39.0 millimeters, width 42.0 millimeters. (After Olsson.) 

FIGURE 7. Venericardia (Venericor) densata Conrad (p.189). Exterior ofright valve (U.S.N. M. 497006), from Arroyo Chacon near 

Laredo, Tex. 

FIGURE 8. Venericardia (Venericor) cacamai Gardner and Bowles, n. sp. (p. 174) . Hinge of co type, an incomplete right valve 

(U. S. N. M. 373032), from Zacate, Nuevo Leon, Mexico. 

FIGURES 9-10. Venericardia (Venericor) klimacodes Gardner and Bowles, n. sp. (p.193). Holotype, a left valve (U.S.N. M. 372693), 

from 1 mile south of Yazoo City, Miss. 9, Interior of holotype; 10, exterior of holotype. 

FIGURE 11. Venericardia (Venericor) cacamai Gardner and Bowles, n. sp. (p. 174) . Exterior of cotype, an incomplete right valve 

(U.S.N. M . 373032), from Zacate, Nuevo Leon, Mexico. 

FIGURE 12. Venericardia (Venencor) pacifica Olsson (p. 179). Dorsal view of double valves of holotype from the Salina formation, 

Negritos, Peru; diameter 31.0 millimeters. (After Olsson.) 

FIGURE 13. Venericm·dia (Venericor) apodensata Gardner and Bowles, n. sp. (p. 192). Exterior of co type, a right valve (U. S. N. M. 

136644), from Jackson, Miss. 

202 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLATE 37 

6 

12 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUP. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 189 PLA'l'E 38 

1 2 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUP. 
.. 

PLATE 38 

FIGURES 1-2. Venericardia (Venericor?) claviger·Gardner and Bowles, n. sp. (p. 176). Holotype, a right valve (U.S. N. M. 136973), 

from Jackson, Clarke County, Ala. 1, Interior of holotype; 2, exterior of bolotype. 

FIGURE 3. Venericardia sp. cf. V. (Venericor) angustoscrobis Gardner and Bowles, n sp. (p. 176). Interior of right valve from 

Claiborne Bluff, Monroe County, Ala., from collection of F. E. Turner, College Station, Tex., showing abnormally high rib count and senile characters both externally and internally. 

FIGURE 4. Venericardia (Venericor) angustoscrobis Gardner and Bowles, n. sp. (p. 175). Exterior of holotype, a right valve (U.S.N. M . 

372691), from Lisbon Bluff, Alabama River, Ala. 

FIGURES 5-6. Venericardia (Venericor) cookei Gardner and Bowles, n. sp. (p.176). Holotype, aright valve (U.S.N. M. 129767), 

from Catons Bluff, Conecuh River, Ala. 5, Exterior of holotype; 6, interior of holotype. 

FIGURE 7. Venericard·ia (Venencor) angusloscrobis Gardner and Bowles, n. sp. (p. 175). Interior of holotype shown in figure 4. 

FIGURE 8. Venericardia sp. cf. V. (Venericor) angustoscrobis Gardner and Bowles, n. sp. (p. 176). Exterior of right valve shown in 

figure 3. 

FIGURES 9-10. Venericardia (Venericor) pilsbryi Stewart (p. 175). Right valve (U.S.N. M. 137225), from Nanafalia Bluff, Tomhigbee River, Ala. 9, Interior of right valve; 10, exterior of right valve. 

203 
PLATE 39 

FIGURES 1-3. Venericardia (Venericor) horatiana Gardner (p. 177). 1, Exterior of right valve (U.S.N. l\1. 373041), trom point 5)4 

miles southwest of Elba, Coffee County, Ala.; 2, exterior of left valve (U.S. N. l\1. 373042), from Woods Bluff, 

Tombigbee River, Ala.; 3, interior of left valve of holotype (U. S. N. l\1. 369238), from point 17~ miles west of 

Sabinetown, Sabine River, Tex., X 2. 

FrGURE 4. Venericardia (Venericor) stewarti Gardner and Bowles, n. sp. (p. 178). Front view of double valves of para type (U.S.N. l\1. 

116027), from Lisbon Bluff, Alabama River, Ala. 

FIGUJ~E 5. Venericardia (Venericor) horatiana Gardner (p. 177). Exterior of left valve of holotype shown in figure 3. 

FIGURES 6- 7. Venericardia (Veneric01) stewarti Gardner and Bowles, n. sp. (p. 178). Holotype (U.S. N. l\1. 154933), from Lisbon 

Bluff, Alabama River, Ala. 6, Interior of left valve; 7, exterior of left valve. 

204 
l'ItOFESSIONAL PAPEit 189 PT,ATE 39 

1 2 

5 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUP. 
GEOLOGICAL SUR VEY PROFESSIONAL P APER 189 PLATE 40 

5 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUI'. 
PLATE 40 

lhGURES 1- 2. Yenericardia (Yenericor) horatiana Gardner (p. 177). 1, Interior of right valve (U.S.N. M. 373041), from point 5}~ 

miles southwest of Elba, Coffee County, Ala.; 2, exterior of left valve of Venericardia planicosta form gamma 

Harris from Woods Bluff, Tombigbee River, Ala. (after Harris). 

FIGURE 3. Yener·icardia (Yenericor) parinensis Olsson (p. 183). Exterior of holotype, a left valve from Keswick Hills, Farinas formation, Peru; height 70 millimeters, width 85 millimeters (after Olsson). 

FIGUHE 4. Yenericardia (Venericor) samanensis Olsson (p. 183). Exterior of cotype, an immature left valve from the Saman conglomerate, N egritos, Peru (after Olsson). 

FIGURE 5. Venericardia (Venericor) horatiana Gardner (p. 177) . Interior of left valve (U. S. N. M. 373042), from Woods Bluff, 

Tombigbee River, Ala. 

FIGURES 6- 7. Venericardia (Venericor) tonosiensis Rutsch (p. 178). 6, Interior of left valve (U. S. N. M. 372923), from mouth of 

Tonosi River, Panama; 7, exterior ·of valve shown in figure 6. 

205 

20~1:.!-39--6 
PLATE 41 

FrGURES l-2. Vener'icardia (Venericor) turneri Gardner and Bowles, n. sp. (p. 179). Holotype, a right valve (U.S.N. M. 1!72921 ), 

from Hatchetigbee Bluff, Tombigbee River, Ala. 1, Interior of holotype; 2, exterior of holotype. 

FIGUR}iS 3- 4. Yenericardia (Venericor) potapacoensis Clark and Martin (p. 180) . Immature left valve of specimen typical of Woodstock greensand marl member, Nanjemoy formation, from collections of Academy of Natural Sciences of 

Philadelphia. 3, Exterior of left valve (after Clark and Martin); 4, interior of left valve (after Clark and 

Martin). 

FIGURE 5. Vene1·icardia (Venericor) clavidens Grzybowski (p. 182). Exterior of left valve, probably from Rica Playa, Peru (after 

Grzybowski). 

FIGURE 6. Venericardia (Venericor) potapacoensis Clark and Martin (p. 180). Exterior of left valve of type specimen from Potapaco 

clay member, Nanjemoy formation, west of Port Tobacco, Charles County, Md.; height 40.0 millimeters, 

width 33.0 millimeters (after Clark and Martin). 

FIGURE 7. Venericardia (Yenericor) diga Gardner and Bowles, n. sp. (p. 181). Interior of cotype, a right valve (U.S.N. M. 373030), 

from Arroyo Ermita at Ermita-La Arena road crossing, Nuevo Le6n, Mexico. 

FIGURE 8. Venericardia (Venericor) pacifica Olsson (p. 179). Exterior of holotype, a left valve from the Salina formation, Negritos, 

Peru; height 42.0 millimeters, width 41.0 millimeters (after Olsson). 

FIGURE 9. Venericardia (Venericor) peruviana Olsson (p. 180). Exterior of holotype, a left valve, from the Salina formation, Negritos, 

Peru; height 66.0 millimeters, width 80.0 millimeters (after Olsson). 

FIGURES 10-12. Venericardia (Venericor) diga Gardner and Bowles, n . sp. (p. 181). 10, Exterior of cotype, a right valve (0. S. 

206 

N. M. 373030), shown in figure 7; 11, double valves of cotype, viewed from the front (U.S. N. M. 373029), 

from the Rio San Juan at Ermita de Abajo, Nuevo Le6n, Mexico; 12, double valves of cotypc, viewed from 

the left (U.S. N. M. 373029). 
GEQT,OGICAI, SURVEY PROFESSIONAL PAPER 189 PLATE 41 

FOSSILS OF THE VENERICARDIA PLANJCOSTA GROUP, 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 180 PLATE 42 

FOSSILS OF THE VJ,NERICARDIA PLANICOSTA GROUP. 
PLATE 42 

FIGURE 1. Venericardia (Venericor) hijuana Gardner and Bowles, n. sp. (p. 184). Sculpture detail of anterior portion of left valve 

from Maverick County, U. S. G. S. sta. 6091, east of Middleton, Hardeman County, Tenn. 

FIGURES 2- 3. Venericardia (Venericor) jewelli Gardner (p. 184). Cotypes (U. S. N. M. 370914) from Midway limestone scarp, 29 

miles southeast of Eagle Pass, Tex. 2, Double valves viewed from the front; 3, another pair of double valves 

viewed from the right. 

FIGURE 4. Venericardia gulielmi Gardner and Bowles, n. name (p. 174). Exterior of holotype, a left valve (U. S.N. M. 154725), from 

Woods Bluff, Tombigbee River, Ala. (after Dall). 

FIGU RE 5. Venericardia (Venericor) labreaensis Olsson (p. 181). Exterior of holotype, a left valve, from La Brea, Negritos formation, Peru; height 34.0 millimeters, width 36.5 millimeters (after Olsson). 

FIGURES 6- 10. Venericardia (Venericor) hijuana Gardner and Bowles, n. sp. (p. 184) . Cotypes and topotypes from sta. 6Q91, 

vicinity of Middleton, Hardeman County, Tenn. 6, Exterior of left valve of cotype (U. S. N. M. 372920); 

7, exterior of umbonal region of left valve of cotype (U. S. N. M. 372919); 8, interior of left valve shown 

in figure 7; 9, interior of left valve shown in figure 6; 10, sculpture detail of anterior portion of right valve, X 3. 

FIGURES 11- 12. Venericardia (Venericor) austroplata Gardner and Bowles, n . sp. (p. 188). Holotype (U. S. N. M. 372924), from 

Point Malaspina, Province of Chubut, Argentina. 11, Dorsal view of holotype; 12, exterior of left valve of 

holotype. 

207 
PLA'I'J£ 43 

FIGURE 1. Yenericardia (Yenericor) aposmithii Gardner and Bowles, n. sp. (p. 186). Exterior of right valve (U. ~. N. M. 1~7224), 

from Nanafalia Bluff, Tombigbee River, Ala. Figured to show greater persistence of ribbing pattern and 

closer cording on posterior area. 

FIGURES 2- 3. Venericardia (Yenericor) smithii Aldrich (p. 185). Cotype from Tun·itella rock near Allenton, Wilcox County, Ala.; 

loaned from the Aldrich collection of the JohnR Hopkins Un iversity, Baltimore. 2, Interior of left valve; 

3, exterior of left valve. 

FIGURES 4- 5. Yenericm·dia (Yenericor) densata malinchae Gardner and Bowles (p. 189). Holotype,, an incomplete right valve 

(U. S. N. M. 373031), from a point 1 mile south,Yest of El Mirador, Nuevo Leon, Mexico. 4, Exterior 

of holotype; 5, interior of holotype. 

FIGURE 6. lfenericardia (Yenericor) aposmithii Gardner and Bowles, n. sp. (p. 186). Exterior of right valve of lfenericm·dia planicosta 

form {3, from Bells Landing, Alabama Ri ver, Ala., slightly reduced in original figure (after Harris). 

FIGURE 7. lfenericardia (lfenericor) aposmithii Gardner and Bowles, n. sp. (p. 186). Interior of right valve of holotype (U.S.N. M. 

1434), from Bells Landing, Alabama River, Ala. 

FIGuRE 8. Yenericardia (lfenericor) apodensala Gardner and Bowles, n. sp. (p. 1 92). Interior of ootype, a right valve (U. S. N. M. 

136644), from Jackson, Miss. 

208 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 180 PLATE 43 

FOSSILS OF TilE VENERICARDIA PLANICOSTA GHOUP. 
GEOLOGICAL S URVEY PROFESSIONAL PAPER 189 PLATE 44 

1 

2 

FOSSILS OF THE VENERICARDIA PLANICOSTA GROUP. 
PLATE 44 

FIGURES 1- 2. Venericardia (Venericor) aposmithii Gardner and Bowles, n. sp. (p. 186) . Holotype (U. S. N. M. 1434), from Bells 

Landing, Alabama River, Ala. I, exterior of left valve of holotype; 2, interior of left valve of holotype. 

209 
PLATE 45 

FIGURES 1-3. Venericardia (Venericor) densata Conrad (p. 189). Pathologic individual (U. S. N. M. 369601) cited by Stewart (see 

text) from Choctaw County, Ala. "The hinge is pathologic, the right cardinal not being fully developed, 

and ncar its base is an extraneous shell fragment embedded in the hinge. The groove on the opposite valve 

is modified to fit the irregular cardinal." 1, Interior of left valve; 2, interior of right valve; 3, exterior of left 

valve. 

FIGURES 4-11. Venericardia (Venericor) densata Conrad, figured to show variation within the lower Claiborne of Texas (p. 189). 

4, Hinge of right valve shown in figure 5; 5, exterior of right valve (U. S. N. M. 1818), from the vicinity of 

Wheelock, Robertson County, Tex., possibly the type locality of V. mooreana Conrad; 6, exterior of left valve 

(U. S. N . M. 497001), from point 10 miles southwest of Pleasanton, Atascosa County, Tex.; 7, exterior 

of right valve (U.S.N. M. 497002), from Smithville, Bastrop County, Tex.; 8, interior of right valve (U. ti. 

N. M . 497003), from point a quarter of a mile northwest of Jourdanton, Atascosa County, Tex.; 9, exterior of left valve (U. S. N. M. 1818), from the vicinity of Wheelock, Robertson County, Tex.; 10, exterior 

of left valve (U. S. N. M. 497004), from Mosleys Ferry, Brazos River, Burleson County, Tex.; 11, exterior 

of right valve (U. S. N. M. 497003), from point a quarter of a mile northwest of ,Tourdanton, Atascosa 

County, Tex. 

FIGUREs 12- 13. Venericardia (Venericor) densata pendletonensis Gardner anj Bowles, n. subsp. (p. 188). Holotypc, a right valvC' 

(U. S. N. M. 372694), from Pendleton Bluff, Sabine River, Tex.; 12, Exterior of holotypc; 13, interior of 

holotype. 

FIGURE 14. Venerica?'dia (Venericor) densata Conrad (p. 189). Interior of valve shown in figure 7. 

FIGURES 15-16. Venericardia (Venericor) apodensata Gardner and Bowles, n. sp. (p. 192). Cotype (U.S.N. M. 369599), from Moodys 

Branch near Jackson, Miss. 15, Interior of left valve; 16, exterior of left valve. 

FIGURE 17. Venericardia (Venericor) zapatai Gardner and Bowles, n. sp. (p. 192). Exterior of double valves of holotype, viewed from 

the left (U.S.N. M. 372692), from point 4.8 miles southeast of Zapata, on the Roma road, Tex. 

210 
G EOI,OGICAL S IJRVEY PROFESSIONAL PAPER 189 PLATE 45 

8 

9 

11 12 

FOSSILS OF THE VENERICAHDIA l'LANlCOSTA GHOUl'. 
GEOLOGICAL SURVEY PROFEflS!ONA!, PAPER 189 PLATE 46 

4 

FOSSILS OF THE YENERICARDTA I'LANICOSTA GROUP. 
PLATE 46 

FIGURE 1. Venericardia (Glyptoactis?) moa Gardner (p. 195). Double valves of holotype, view from left (U.S. N. M. 370922), from 

point 18 miles southeast of Eagle Pass, Maverick County, Tex., X 2. 

FIGURES 2- 3. Venericardia ( Venericor?) mingoensis Gardner and Bowles, n. sp. (p. 194). Holotype, a right valve (U. S. N. M. 

372922), from Black River, S. C. 2, Exterior of holotype; 3, interior of holotype. 

FwunEs 4-5. Venericardia (Glyptoactis?) hesperia Gardner (p. 195). Holotype (U. S. N. M. 352268), from Frio River half a mile 

below Myrick's apiary, Uvalde County, Tex. 4, Double valves viewed from right; 5, double valves viewed 

from rear. 

FtGURF;S 6- 7. Venericardia (Venericor) francescae Gardner and Bowles, n. sp. (p. 183). Holotype, a right valve (U.S.N. M. 372923), 

from point 1 mile southeast of New Albany, Union County, Mi~s. 6, Interior of holotype; 7, exterior of 

holotype. 

FIGURE 8. Venericardia (Venericor) regia Conrad (p. 187). Possibly Conrad's type from the Aquia formation, Piscataway, Md., 

collection of Academy of Natural Sciences of Philadelphia. Interior of right valve, X !1/ 10. (After Clark 

and Martin.) 

FIGURE 9. Venericardia (Venericorl') greggiana Dall (p. 194). Exterior of holotype, a right valve, from Greggs Landing, Alabama 

River, Ala. (After Harris.) 

FIGURE 10. Vencricardia (Venericor) regia Conrad (p. 187). Exterior of right valve shown in figure 8, X 9/10. (After Clark and 

Martin.) 211 

INDEX 

A 

Abstract_ _____ _______ ____ _____ ________ _ Page 

143 

Ackerman formation, relations oL _____ ____ ___ _ --------------- ------- ---- 140,149 

Acknowledgments for aid ______ ----------------------- ____________ -----------_ 143 

acuticostata, Venericardia __ ------------------ ___ __________ ____ __________ __ _.__ 194 

alabamiensis, Ostrea___ _ _ __ _ _ _ _ _ ___ _ _ _ _ _ __ __ _ _ _ _ __ _ _ _ _ ___ _ _ _ _ _ __ __ _ _ _ ___ __ _ __ _ 156 

aJticostata, Veuericardia _____________________ _______________ 167,185,186,194,195,196 

An1n1onites____ _ _ ___ _ _ _ __ __ _ _ _ __ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ __ _ _ _ __ __ _ _ _ _ _ _ 158 

angustoscrobis, Veuericardia (Venericor) --------------------- 152, 159, 17&-176, pl. 38 antiq nata, Venericardia______ _ __ __ _ _ _ _ __ _ _ _ _ _ _ _ ___ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 145 

apodcnsata, Vencricardia (Venericor) ____________________ __ 159,192-193, pis. 37, 43,45 

uposrnithii, Vcnericardia (Vencricor) __ __ __ ___ ____ 149,150,186-187,188,190, pls. 43,44 

aragonia, Venericardia ___ ----------- ---------- ----- --- ____ -------- ------ 175, 177, 183 

asci a, Venericardia __ ____ ------------------ __ ---------------------------- 171, 172, 190 Venericardia (Venericor) ____________ ___________ ______ __ ____ ______ 171- 172, pl. 35 

Astarte concentrica_ _ _ _ _ _ __ __ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ __ __ _ __ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ 164 

corrugata_ _ _ _ __ __ _ _ _ ___ _ _ _ __ ___ _ _ _ __ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ __ _ _ _ _ __ _ _ _ _ 164 

Inutabilis _____ -------------------- __ ----- ___ ---------------------------- 164, 165 sima______________________________________________________________________ 164 

Astarticls _ _ _ __ _ _ _ _ _ _ __ _ __ _ _ _ __ __ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ 164 

austroplata, Vencricarclia (Venericor) ____ _____ __ ____ ___ ______ ___ __ ___ 148,188, pl. 42 

l:l 

Barnwell formation, relations oL __________ ____ __ ______ ____ _______ _______ ___ 157,158 

baronetti, Cardita_ ------------ __ __ ___ _ ------------- ___ __ ___ __ ______ ___ ___ ____ 162 

Bashi formation, fauna oL_____ __ ____ _____ _____ ___________ ______________ _____ 150 

bashiplata, Venericardia (Venericor) _____ 150, 163, 164, 169-170, 171, 172, 173, pis. 33, 34 

beaumonti, Cardita __________ ____ ___ -------------------- ______ -------------- __ 162 

bellastriatum, Solarium_______________________________________________________ 158 

Bells Landing marl, fauna oL---------------------------------------------- 149,150 

Bibliography----------------- ___ ------------- __ -------------------- _______ _ 16&-167 

Bigford member, relations oL____________________ __ __________________________ 154 

llullinella jacksorwnsis______ __ ______ _ _ _ ___ __ ___ ____ _ __ ___ __ _ __ _ __ __ _______ _ __ 158 

c caeamai, Venericardia (Venericor)_ ---------------- ------------------ 155, 174, pl. 37 

Caddell clay, relations oL __ ---------- ---------------------------------------- 159 

calafia, Venericardia _____ ________ __ _ ------------------ __ ---------- ________ ____ 155 

Venericardia hornii_ _______ _____ __ ___________________________ _ ------------ 179 

Calyptraphorus cf. C. velatus __ _____ ___ _______ _____ ___ ____ ____ __________ _____ 161 

Cane River formation, relations of. ______ __________ ________ ________ ____ _____ 153,154 

Cardita __________ __________ ___ _________ ________ __________________ ____ ___ 164, 167- 168 

baronetti. _ ___ _ __ ____ _ _____ _ _ _ __ _____ _ __ ____ ____ ________ __ __ ________ ___ ___ 102 

beaumontL. _ _ _ _ _ _ _ _ _ _ ___ _ _ __ _ _ _ ___ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ ___ __ _ _ _ _ _ __ __ _ _ _ _ _ _ 162 

densata ___ ___ ----------- _____ ___ ------------ _:__ ______ ______ __ _______ _____ 189 

dorsata__ __ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ __ _ _ ____ 189 

rtnponii. .. _ __ ___ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ __ __ _ _ _ _ __ __ _ _ _ _ __ __ _ _ _ __ _ _ _ _ _ ___ _ __ __ ___ _ 162 

lib yea ____ ___ ___ ________________ ____ __________ ---------------------------- 162 

longa ___ ____ ____ __ ____ ____ ________ ___ __________ _ , - ___ ___ ___ _______ _______ - 161 

planicosta. ___ ____ ____ ------ ---------------- ___ ------------------- ___ ___ 185, 187 

regia_______ ______ ____ ___ _______ _______ ________ _____ _______ ___ ___ __ ___ _____ 187 

sandiegoensis ________ ______ _____ __ __ _____ ________ ____ ___ ___ __________ ____ .. 194 

subquadrata_ __ _ _ _ _ _ _ _ _ _ _ _ __ __ _ _ _ ___ _ _ __ _ __ _ _ _ _ _ __ _ _ __ _ __ _ _ _ _ _ ____ _ _ _ _ _ _ _ _ 184 

variegata. ___________________________________________________________ ___ 167-168 

(Venericardia) densata_____ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ __ 189 

Carolia _ _ _ _ _ _ _ ___ _ _ _ _ _ _ _ _ _ _ _ ___ _ _ _ __ _____ _ _ _ _ _ _ _ _ ____ _ _ _ _ _ __ _ _ _ _ _ _ __ __ _ _ _ _ ___ _ 161 

Castle Hayne marl, relations oL---------------------------------------------- 158 

Catahoula sandstone, relations oL____________________________________________ 159 

Chamids. _ ---------------- ___________ ________ __ ______________________ -------- 164 

Cbank shells. ______________________________ __ __ ------------------------------ 164 

claiboplata, Vcncricarclia (Venericor) __ _____ __ 152,153, 154-155,173-174, 177,191, pl. 36 

Claiborne gro up, fanna oL--------- -- -------------------------- ------------ 151-156 

relations oL ______ ____ -------- _____ ___ ______ __ ________ ____ -------------- 158, 159 

clavidcns, Vcnericardia --- -- -------------- _____ ___________ ---------- __ -·----- 174 

Vencricardia (Vencricor) ____ ______ _______ ____ ---- ---------------- 182-183, pl. 41 

clav iger1 Vcncricardia _____ ____ ------- _____ ___ ___ ___ _______ __ ________ ------ ____ 176 

Vcncricardia (Vencricor) __ ---------- ___ ___ _______ ---------- __ 175, 176-177, pl. 38 

Clav ilithes __ --------------------- __ ____ ______ _ ___ ______ __ ____ ____ __ _____ _____ 183 

Clayton formation, character and distribution oL_ _____ ________ ____ __ __ ______ 144 

fauna oL ------- __ _______ _____ ___ ------- __ _________ _ ----------____ __ __ __ 144-146 

Coal Bluff bed, relations oL ------------------------------------------------ 146,149 

Cocoa sand member, relations oL____________________________________________ 157 

concentrica, Astarte. _--------------___ _______________________________________ 164 

Page 

Congaree clay member, relations of.___________ _____ __ ___ ___ _____ _____ __ 157 

Congaree shales, relations oL ------------------------------- __ ___ _____ __ ______ 158 

Conrad, '1'. A., quoted·----------------------------------------------------- 158, 190 Cook Mountain formation, character and relations oL _______________ _______ 154,155 

fauna oL __ ------------------------------------------------------------- 153,155 

Cooke, C. W., quoted . ------------------------------------------------- 144,146,179 

cookei, Venericardia (Venericor) ___ ____ ____ ____ ____ ______ _________ 159,175,176, pl. 38 

Cooper marl, relations oL---------------------------------------------------- 158 

corrugata, Astarte. _______________ ___ __ ____ -- __ -__ ------------------ ---------- 164 

Crowleys Ridge, structure oL------------- ----------------------------------- 146 Cucullaea _______ ------- ________ ____ ___________ __ ____ _ -_____ -----__ --------- _-- 161 

cuvieri, Venericardia. ______ ---------------- ____ -------- ________ __ --------- ___ 194 

D 

Dall, W. H., quoted-------------------- ------------------------------------ 160,164 

densata, Cardita ____ _____ ___ -------------------------- ________ ---------------- 189 

Cardita (Venericardia) ____ _____ ______ ____ ______ ____ _________ _ ------------ 189 

Venericardia _______ ______ ___ ____________ ____ \.52,154-155,169,173,174, 176,189-192 

Venericardia (Venericor)_ -- ------------------------------ 188, 189-192, pis. 37,45 

diga, Venericardia (Venericor) -------------- ___ _____ __ 161, 173, 181, 182, 183, pls. 37,41 

Distribution of species comparable to V. planicosta ___ ____ __ ______ 160--163, pls. 29-31 

dorsata, Cardita _______________________________________________ - ________ ---- __ 189 

Dumblc, E.'!'., quoted------------------------------------------------------- 182 

duponti, Cantita __ ------------------------------------- ________ -------------- 162 V cncricardia_____ _ _ _ __ __ _ _ _ __ __ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ ___ _ _ _ _ _ __ _ _ _ _ _ _ __ 101, 168-109 

E 

Enclimatoceras __________ ___ __ --" __________ _ ---- _----- _- ---------------------- 161 

Eocene epoch, formations oL -------------------- --------------------------- 143-160 

formations of, correlation oL.--------------------------------- 143-144 (chart l) 

marine beds of, distribution of outcrops oL _ ----------------- ------------ pl. 31 

]<' 

Fayette sandstone, relations oL---------------------------------------------- 159 Findlay, W. A., quoted _________________ __ __ ___________________ _________ ___ 164-165 

Flint River formation, relations of. ______ ____ ___ _____ ___ _______________ ____ __ _ 157 

oraminifera __ ________________ ___________________ ____ ___ _______ ____________ 146-147 

:Forest Hill sand, relations oL __ __ _____________ ____ ___ _______ _ --------------- 15G 

francescae, Venericardia (Venericor) ____ _____ ____ __ ____ ____ ___ ____ 145,183-184, pl. 46 

Frio clay, relations oL-------------------------------------------------------- 159 

Fulgur _________ ------------------------ __ _ ------------------------------- __ 163-164 perversum ____________________________ _______________ __ __ ______ ___ __ _ -_ _ 163-I 64 

G 

Gabb, W . M., quoted-- ------------------------------------ ------------------ 185 

georgiana, Ostrea. ---------------------------------------------------------- 157, 158 

Gisortia ___ _____ __ _______ --------------- ____ -------------------------------- 161, 162 Glans __________ ____ ___ _______ ____ ______ __ ____ _____ __ _________________ - _______ - 195 

G lyptoactis ____________________ ___ _______ __ _ ----- _____ ___ __ ___ ___ _______ 186, 194-195 

Goodallia ___________________________________ ____ ____ ___ ____ - __ _____ - _- __ ----__ 164 

Gosport sand, character and relations oL ----------------------- -------- 152, 15&-156 granulata, Venericardia _______________________________ ---- _ _ _ _ _ __ _ _ _ _ _ __ _ _ _ __ _ 164 

greggiana, Venericardia _________________ -------------------- ________________ 150, 194 

Venericardia (V~nericor) ________ --------------------------------- 150, 194, pl. 46 

Greggs Landing marl, fauna oL ... ------------------- ---------------------- 149-150 gulielmi, Venericardia ___ _____________________________________________ 174-175, pl. 42 

H 

hadra, Venericardia ______________________ _ --------- _ -------------- _______ : __ 186, 194 

Hanna, M.A., quoted---------------------------------------------------- ---- 164 llarris, G. D., quoted ______________________________________________________ 158,185 

hatcheplata, Venericardia (Venericor) ________________________ 151,172-173, pis. 33,34 

Hatchetigbee formation, fauna oL-------------------------------------------- 151 

Hercoglossa _______________ ----------------------- ----------- __ ---------------- 161 

hesperia, Venericardia. ------------------------- ________________________ 147, 148, 161 

Venericardia alticostata _________________ ------- _ ----- __ __ ____ ___ ____ ______ 195 

Venericardia (Giyptoactis) _________ ___ __ ______ ___________ 147- 148,195,196, pl. 46 

hijuana, Venoricardia (Venericor) ____________________________ 145,148,184-185, pl. 42 

horatiana, Vencricardia __________ _____________ __ ____ 15(;...151, 175,177,178,179,180,183 

Vencricardia (Vencricor) _______ __________________ ___ _______ ___ 177-178, pis. 39, 4U 

Hornerstown marl, fauna oL------------------------------------------------- 145 

hornii, Venericardia __ _ ----------------------------------------------- __ 164, 177, 179 

Venericardia planicosta ___ _____ ___ ------------------------------------ __ 178, 179 

humerosa, 'l'urritella__________________________ ___ ____________________ _________ 161 

213 

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