Basal Eagle Ford Fauna 

(Cenomanian) in Johnson 

and Tarrant Counties 

Texas

GEOLOGICAL SURVEY PROFESSIONAL PAPER 274-C
Basal Eagle Ford Fauna 

(Cenomanian) in Johnson 

and Tarrant Counties 

Texas

By LLOYD WILLIAM STEPHENSON

A SHORTER CONTRIBUTION TO GENERAL GEOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 274-C

Descriptions and illustrations of fossils of 

Late Cretaceous age, including two identified 

bivalve species, two gastropod species, and 

eight cephalopod species

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1955
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

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

Washington 25, D. C. - Price 75 cents (paper cover)
CONTENTS

Abstract.- _ ___________

Introduction __________

Fossiliferous localities __

Systematic descriptions.

Pelecypoda. ______

Scaphopoda_ ______

Page 

53

53

54

55

55

57

Systematic descriptions—Continued 

Gastropoda._________________

Cephalopoda.________________

Literature cited.__________________

Index.__________________________

Page

57

58

65

67

ILLUSTRATIONS

[Plates 4-7 follow page 68]

PLATE 4. Inoceramus, Pseudomelaniat, Lispodesthes, Tarrantoceras, Desmoceras, and Acanthoceras.

5. Tarrantoceras.

6. Boris siakoceras, Euomphaloceras, and Tarrantoceras.

7. Euomphaloceras.

in

A SHORTER CONTRIBUTION TO GENERAL GEOLOGY

BASAL EAGLE FORD FAUNA (GENOMANIAN) IN JOHNSON AND TARRANT COUNTIES, TEXAS

By LLOYD WILLIAM STEPHENSON

ABSTRACT

The basal few feet of the Eagle Ford shale in Johnson and 

Tarrant Counties, Tex., contains interbedded concretionary 

calcareous sandstones and sandy limestones, some of which are 

fossiliferous. The fauna obtained from the concretions includes 

2 identified pelecypod species, 2 gastropod species (both new) 

and 8 cephalopod species (6 new). One new genus, Tarrantoceras, of the family Acanthoceratidae, is described. The two 

new gastropod species are: Pseudomelanial basicostata and 

Lispodesthes lirata; the new cephalopod species are: Acanthoceras 

johnsonanum, Tarrantoceras rotatile, T. stantoni, T. lillianense, 

T. multicostatum, and Borissiakoceras orbiculatum. Several 

additional poorly preserved mollusks are identified generically 

but not specifically.

Both the lithologic character of the beds and the composition 

of the fauna indicate that this zone is the northward extension 

of the flag member (later named Bluebonnet member by Adkins 

and Lozo) of Adkins, in Bell County, Tex. The zone is stratigraphically higher and younger than the Tarrant unit of Moreman in Tarrant County, a unit that Moreman considered correlative with the flag member in Bell County.

In terms of the classification of the Cretaceous strata of 

Europe the fauna here described is of late Cenomanian age.

INTRODUCTION

This report records a few molluscan species, mainly 

acanthoceratid ammonites (Cenomanian), from concretionary calcareous sandstones and sandy limestones 

interbedded with shale in the basal few feet of the 

Eagle Ford shale in southeastern Tarrant and northeastern Johnson Counties, Tex. The fauna is of 

interest partly because it includes species not previously 

described and partly because it confirms evidence of 

the synchroniety of the containing beds with the socalled flaggy member of the Eagle Ford shale in Bell 

and McLennan Counties. Attention was first called 

to the flag member by W. S. Adkins (1923, p. 67-79), 

at which time he interpreted these flaggy beds as 

forming a middle member of the Eagle Ford shale. In 

a later publication Adkins (1933, p. 239, 270, 417-422) 

treated the shale below the flag member as a unit of 

uncertain age, which he called the Pepper formation. 

However, in a recent publication Adkins and Lozo 

(1951, p. 117-157) present evidence that the Pepper

339390—55

shale is a southward extension of the Lewisville member of the Woodbine formation, and this correlation is 

accepted by Stephenson (1953, p. 57-67).

It is therefore established that the flag member, 

which Adkins and Lozo (1951, p. 119, fig. 26), later 

named the Bluebonnet flag member of the Lake Waco 

shale, forms the basal unit of the Eagle Ford shale, as 

that unit is developed in McLennan and Bell Counties. 

These authors treat the Eagle Ford shale in that area 

as a group. The Lake Waco shale is the lower of two 

formations into which they divide the Eagle Ford 

group in McLennan, Bell and other counties farther 

south, and the South Bosque marl is the upper formation. They subdivide, the Lake Waco into three 

subunits: the Bluebonnet flag member, about 6 feet 

thick in McLennan, Bell, and Williamson Counties, at 

the base; the Cloice shale member, 12 to 35 feet thick, 

in the middle, extending from McLennan County to 

Travis County; and the Bouldin flag member, 8 to 13 

feet thick, at the top, also extending from McLennan 

County to Travis County.

Among fossils described by Adkins (1928, p. 240-248) 

from the flag member (=Bluebonnet member) in Bell 

County are: Eucalycoceras leonense, Acanthoceras lonsdalei, A. belknse, and A. stephensoni. From the same 

source Moreman (1942, p. 203, 204) described Acanthoceras validum and A. pepperense. Acanthoceras alvaradoense Moreman is from the same stratigraphic 

position at a locality 4 miles south of Alvarado, Johnson 

County. It appears that the type of Mantelliceras 

sellardsi Adkins (1928, p. 239) came from the Bouldin 

member in Williamson County, but Adkins also recorded it from the Bluebonnet member in Bell County. 

All the others were from the Bluebonnet member.

It is appropriate to mention here a geologic unit in 

Tarrant County, originally described by Moreman (in 

Adkins, 1933, p. 424, 425) as the Tarrant sandy clay 

and limestone, and later (1942, p. 195) referred to by 

him as the Tarrant formation. He classed this 15- 

to 18-foot unit as the basal formation of the Eagle Ford

53
54 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

group, and correlated it with the flag member (=Bluebonnet member) in Bell County. Locally the Tarrant 

is a sharply defined unit with a thin conglomerate at 

the base. Stephenson (1946, p. 1764, 1770; 1952 

[1953], p. 3, 4, 30) has presented evidence that the 

Tarrant unit is stratigraphically lower and older than 

the Eagle Ford shale and forms the upper part of the 

Lewisville member of the Woodbine formation in 

Tarrant County.

The correlation of the Tarrant with the flag member 

has led to the listing of Woodbine species with Eagle 

Ford species (Adkins, 1928, p. 32; 1933, p. 432-435; 

Moreman, 1942, p. 193-196), and consequently to 

confusion as to the stratigraphic relation of the upper 

Woodbine to the lower Eagle Ford. A careful recheck 

ot the Tarrant fauna shows that of 74 named species (4 

questionably identified), 37 (2 questionably identified) 

are common to the fauna of the typical Lewisville 

beds on Timber Creek in Denton County. So far as 

I have been able to determine, only one species, 

Exogyra columbella Meek, is common to the Tarrant 

and the Bluebonnet member. One other species, 

Inoceramus arvanus Stephenson, now known to be 

present in the Bluebonnet and its equivalents, was 

originally described from, the Lewisville member in 

Cooke County, but it has not been recognized in the 

Tarrant unit. One species from the Tarrant, Euomphaloceras eulessanum (Stephenson), is closely related to 

Euomphaloceras lonsdalei (Adkins), but it appears to be 

specifically distinct. Another species in the Tarrant, 

Eucalycoceras barcusi (Jones), (—Acanthoceras barcusi 

Jones), appears to be closely allied to Eucalycoceras 

leonense Adkins from the Bluebonnet member.

FOSSILIFEROUS LOCALITIES

The fossils described on following pages were obtained from beds that represent the northward extension of the flag or Bluebonnet member of the Lake 

Waco formation of Adkins and Lozo, and therefore 

belong stratigraphically above the Tarrant unit. The 

fossils were collected from the basal 10 feet or less of 

the Eagle Ford shale at two nearby localities on 

Walnut Creek in Tarrant County, and at two localities 

in Johnson County.

The two localities in Tarrant County were discovered by the late T. W. Stanton in 1923. They are 

on Walnut Creek, 4.75 miles east-northeast of Mansfield. The following is quoted from his field notes 

dated May 18, 1923:

On Walnut Creek just below bridge (which has been washed 

out) a small exposure of the Eagle Ford contains many large 

flat concretions, one of which was very fossiliferous, containing 

Inoceramus fragilis [?], Acanthoceras, Anchura (orig. no. 1942). 

One hundred yards [about 165 yards] down the creek there is a 

good exposure showing 15 ft. of Eagle Ford with the large concretions in lower 6 ft. and thin indurated sandstone bands for 5 

feet higher. Some of these yielded Ostrea and a few thin pelecypods. These exposures must be within 10 feet of the top of 

the Woodbine. A very good series of specimens of the Acanthoceras was obtained here.

Stanton's collection (USGS 11740) was obtained from 

the large concretions. 1 He states that the concretions 

are within 6 feet of the base of the 15-foot section.

In March 1929, Stanton, accompanied by J. B. 

Reeside, Jr., and me, visited the Walnut Creek localities. 

I measured and described the section at the exposure 

about 500 feet downstream from the bridge site, as 

follows:

Section on left bank of Walnut Creek, ^.75 miles east-northeast of 

Mansfield, 500 feet downstream from an abandoned road crossing

Eagle Ford shale: Feet

7. Clay, gray, shaly, weathering in thin flakes; 

contains a few thin, irregularly platy calcareous 

sandstone seams-.______-_-_-_--_--_-_---_-- 7

6. Sandstone, platy, and sand, 1 to 6 inches thick, 

crossbedded, containing scattered white clay 

balls at base__.____________--__-_---_-_-___ Yis-%

5. Clay, dark, shaly, gypsiferous; a few concretionary calcareous sandstone masses about 4 

feet above base-.--_-_-_--__---------------- 8

4. Sandstone, thin, platy, and interbedded shale; here 

and there a small to large, more or less ovate, 

concretionary (septarian) mass of fine calcareous sandstone reaching 1 foot in thickness, 

and showing effects of crushing by pressure from 

above; fossiliferous--_-__-___---------_------ 1

3. Clay, dark, shaly.._________________-------__- 1

2. Sandstone, thin, coarse, calcareous, containing 

dark phosphatic pebbles and marcasite pebbles; 

contains Exogyra columbella Meek, and fish 

teeth; noted several shark teeth, one tooth of 

Ptychodus and one pavement tooth_______,___ }ii-y\z

Woodbine formation:

Lewisville member:

1. Sand and sandy clay, gray, massive, fine argillaceous, to water leveL-----_-_----__-___ 2

Total. 20

At the lower end of the exposure sandstone of Woodbine aspect could be seen below water level in the creek. 

Reeside found the internal mold of a fragment of a large 

ammonite (USGS 14582), here identified as Euomphaloceras alvaradoense (Moreman), loose at the base of the 

preceding section, and probably weathered out of either 

layer 4 or layer 5 (pi. 7, fig. 1).

A small collection (USGS 14580) was made from a 

large concretion in place 6 feet above the base of the 

Eagle Ford formation, about 150 feet downstream from 

the bridge site. In a layer of coarse calcareous sand in 

the Woodbine formation, 5 feet below the base of the

1 A collection made at a given locality at a given time is assigned a United States 

Geological Survey number (as USGS 11740). Other collections made at the same 

locality at later times are given separate and later collection numbers. Thus more 

than one collection number may pertain to the same locality.
BASAL EAGLE FORD FAUNA IN JOHNSON AND TARRANT COUNTIES, TEX. 55

Eagle Ford shale, were collected Ostrea soleniscus Meek, 

Exogyra columbella Meek, Protarca? tramitensis (Cragin), and Gymnentome valida Stephenson (USGS 14579). 

These are common species of the Lewisville member of 

the Woodbine formation.

The fossils from the basal beds of the Eagle Ford 

shale on Walnut Creek are listed below:

Fossils from basal beds of the Eagle Ford shale on Walnut Creek, 

about 4-^5 miles east^northeast of Mansfield, Tarrant County, Tex. 

(USGS 11740, 14580, 14582}

[The one species marked with an asterisk (*) is common to the Lewisville member of 

the Woodbine formation. The three species marked with a dagger (t) are common 

to the Bluebonnet member (=flag member) of Bell and Williamson Counties]

*] Inoceramus arvanus Stephenson

Ostrea sp.

Brevicardium? sp.

Caestocorbula? sp.

Cadulus sp.

Pseudomelania? basicostata Stephenson, n. sp.

Lispodesthes lirata Stephenson, n. sp.

Cyclichna sp.

Acanthoceras johnsonanum Stephenson, n. sp.

Tarrantoceras rotatile Stephenson, n. sp.

stantoni Stephenson, n. sp.

lillianense Stephenson, n. sp. 

^Euomphaloceras lonsdalei (Adkins) 

\E. alvaradoense (Moreman) 

Borissiakoceras orbiculatum Stephenson, n. sp.

One of the two localities in Johnson County, the one 

on the north-facing slope of Mountain Creek Valley, 

2.5 miles north-northeast of Alvarado, was discovered 

by Stanton, Reeside, and Stephenson in March 1929. 

The outcrop consists of large calcareous sandstone concretions containing fossils, weathered out in a field. 

Large masses of sandstone typical of the Lewisville 

member of the Woodbine formation are exposed nearby 

in the bed of Mountain Creek topographically 20 feet 

lower than the fossiliferous concretions in the field. 

The concretions must therefore occupy a stratigraphic 

position low in the Eagle Ford shale, within a few feet 

of the top of the underlying Woodbine formation. The 

following fossils were obtained at this locality:

Fossils from concretions near the base of the Eagle Ford shale, in 

a field 2.5 miles north-northeast of Alvarado, Johnson County, Tex. 

(USGS 14588}

[The two species marked with an asterisk (*) are common to the Lewisville member 

of the Woodbine formation. The three species, marked with a dagger (t) are common 

to the Bluebonnet member (=flag member) of the Lake Waco formation of Bell and 

Williamson Counties]

*\ Inoceramus arvanus Stephenson

*Exogyra columbella Meek

Acanthoceras johnsonanum Stephenson, n. sp.

Tarrantoceras rotatile Stephenson, n. sp.

multicostatum Stephenson, n. sp. 

t Euomphaloceras lonsdalei (Adkins) 

]E. alvaradoense (Moreman)

Tarrantoceras rotatile is closely related to T. sellardsi 

(Adkins), which is recorded from both the Bluebonnet

and Bouldin members of the Lake Waco formation. 

Acanthoceras johnsonanum appears to be more closely 

related to A. bellense Adkins, from the Bluebonnet 

member, than it is to other species in the two flaggy 

members.

The other locality in Johnson County is in an erosion 

gully in a cultivated field about a mile north of Lillian. 

This place was discovered by James P. Conlin, of 

Burleson, Tex. He reports finding the following fossils 

in a concretion from this gully: Acanthoceras alvaradoense Moreman, Acanthoceras sp., Eucalycoceras sp., 

and Borissiakoceras sp. I am referring Moreman's 

species A. alvaradoense to the genus Euomphaloceras 

Spath, and Conlin's Eucalycoceras to the new genus 

Tarrantoceras. Conlin has sent to me from this locality 

one specimen that I refer to Tarrantoceras rotatile and 

another that I am calling T. lillianense (USGS 24510). 

He has also furnished a specimen from the same source, 

that I am making the holotype of T. stantoni.

SYSTEMATIC DESCRIPTIONS

Class PELECYPODA

Genus INOCERAMTTS Sowerby, 1822

Inoceramus arvanus Stephenson

Plate 4, figures 1-3

1952 [1953]. Inoceramus arvanus Stephenson, U. S. Geol. 

Survey Prof. Paper 242, p. 65, pi. 12, figs. 6-9.

The basal beds of the Eagle Ford shale yielded 

specimens of a small Inoceramus that appear to be 

identical in essential shell characters with /. arvanus 

Stephenson from the Lewisville member of the Woodbine formation in Texas. As is generally true of this 

genus the shells of any given species show considerable 

individual variation, but the variations in form outline 

and surface features of the shells here under consideration agree essentially with those exhibited by the 

Lewisville species, and the average size is about the 

same.

Shell rather small for the genus, roughly subcircular 

to subquadrate in outline, moderately inflated. Form 

and outline showing marked individual variations. 

Anterior slope steep, in some specimens at right angles 

to the plane of contact of the two valves, and in some 

overhanging a little toward the front. The posterodorsal, posterior and ventral slopes descend more gently 

and the latter may be modified by a broad, shallow 

radial depression. Beaks prosogyrate, strongly incurved, situated at the anterior extremity of the hinge, 

and at or near the anterior margin of the shell. The 

anterior margin descends steeply and may be at right 

angles to the straight hinge line. Surface marked 

only with fine growth lines and with irregularly developed growth undulations.
56 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

The right valve shown in plate 4, figure 3, measures: 

Length 43 mm, height 43 mm, convexity about 13 mm. 

The larger left valve shown in plate 4, figure 1, measures: 

Length 53 mm, height 57 mm, convexity about 17 mm.

None of the available specimens from the flaggy 

limestones forming the base of the Eagle Ford shale 

show the hinge or ligamental pits. As seen in paratypes from the Woodbine formation (Stephenson, 

1952 [1953], pi. 12, figs. 8, 9), the ligamental area is 

long, 3 or 4 mm wide in adults, and is crossed transversely by a series of shallow ligamental pits that are 

nearly twice as wide as the spaces separating them.

Types.—Holotype, TJSNM 105157; 3 figured paratypes, 

USNM 105158 a-c, and 12 unfigured paratypes, TJSNM 105159; 

3 plesiotypes from basal calcareous concretions of the Eagle 

Ford shale, USNM 108840, 108849, and 108864.

Occurrence.—The species was originally recorded from the 

Lewisville member of the Woodbine formation, in Cooke County, 

Tex., at a locality half a mile north of U. S. Highway 82, half 

a mile west of the Grayson County line (type locality); from 

Grayson County on a branch of Walnut Creek, 0.7 mile north 

of Gordonville; and on a branch of Sandy Creek, 2.5 miles north 

of Sadler.

The species is present in basal calcareous concretions of the 

Eagle Ford shale at the following localities in Texas:

Walnut Creek, about 4.75 miles east-northeast of Mansfield, 

Tarrant County (USGS 11740 (1 figured)).

Walnut Creek, 150 feet downstream from the old piers at a 

bridge site, about 4.75 miles east-northeast of Mansfield, Tarrant 

County (USGS 14580).

North-facing slope of Mountain Creek Valley, 2.5 miles northnortheast of Alvarado, Johnson County (USGS 14583 (1 figured)).

Bird Creek, south of Belton-Temple Highway, about 4 miles 

east-northeast of Belton, Bell County (USGS 11845 (1 figured), 

13577).

Genus OSTREA Linn§, 1758 

Ostrea sp.

Many small and fragmentary shells of a poorly 

preserved, undetermined oyster are present in one of 

the collections from Walnut Creek, about 4.75 miles 

east-northeast of Mansfield, Tarrant County, Tex. 

The containing matrix is a fine calcareous sandstone 

(USGS 11740, USNM 108839).

Genus EXOGYRA Say, 1820 

Exogyra columbella Meek

1876. Exogyra columbella Meek, in Macomb, Rept. Expl. 

Exped. Santa Fe, N. Mex., to junction of Grand 

and Green Rivers, p. 124, pi. 1, figs. 3 a-d. (See 

synonymy in U. S. Geol. Survey Prof. Paper 242, 

1952 [1953], p. 77.)

This species is represented by one small internal 

mold in basal calcareous concretions of the Eagle Ford 

shale at the locality on the north-facing slope of

Mountain Creek Valley, 2.5 miles north-northeast of 

Alvarado, Johnson County, Texas (USGS 14583). It 

occurs at the same stratigraphic position in a branch 

west of the Missouri-Kansas-Texas Eailroad, 1.25 miles 

south of Grand view, Johnson County (USGS 14145), 

and in a road ditch 0.75 mile east of Lloyd, 0.5 mile 

north of Pleasant Home School, Denton County. For 

synonymy, description, types, and occurrence and range 

in Texas (see Stephenson, (1952 [1953], p. 77). The 

basal beds of the Eagle Ford shale is the highest stratigraphic position from which this species has been 

recorded in Texas. USNM 108865.

Genus BREVICARDIUM Stephenson, 1941 

Brevicardium? sp.

One shell, a right valve, from the locality on Walnut 

Creek, 4.75 miles east-northeast of Mansfield, Tarrant 

County, Tex. (USGS 11740), is questionably referred 

to Brevicardium Stephenson. In size and form the 

specimen agrees well with that genus. The shell, 

which is thin and frail, is embedded in fine hard calcareous sandstone in such a manner that only its 

interior surface and margin are observable. Obscure 

radial lining on the internal surface and fine crenulations on the margin suggest the presence on the exterior 

surface of fine radial ribs such as characterize the genus 

Brevicardium. The hinge features are obscure. The 

shell measures: Length 8.4 mm, height 7.5 mm, convexity about 2 mm. USNM 108850.

Genus CAESTOCORBULA Vincent, 1910 

Caestocorbula? sp.

In the collections from two localities on Walnut 

Creek, about 4.75 miles east-northeast of Mansfield, 

Tarrant County (USGS 11740 and 14580), are several 

internal molds of a small bivalve mollusk belonging to 

the family Corbulidae, and questionably referred to the 

genus Caestocorbula Vincent. Remnants of shell substance adhere to the molds over parts of their surfaces. 

The molds are plump centrally and anteriorly, and 

strongly constricted posteriorly, with a short truncation 

at the posterior end. The right valve bears small 

distinct, rather closely spaced concentric ribs on its 

lateral surface; the left valve is nearly smooth, but has 

weak concentric ribs. The reference of the molds to 

Caestocorbula Vincent is based on similarity in form 

and on the concentric ribbing on the right valve which, 

though finer, resembles that on, Caestocorbula crassiplica (Gabb) from the Ripley formation of Mississippi 

and Tennessee. A selected right valve measures: 

Length 4 mm, height 2.8 mm, convexity about 1.5 mm. 

USGS 108851 and 108852.
BASAL EAGLE FORD FAUNA IN JOHNSON AND TARRANT COUNTIES, TEX. 57

Class SCAPHOPODA

Genus CADUIUS Philippi, 1844

Cadulus sp.

One small smooth incomplete tube partly embedded 

in hard matrix, from Walnut Creek, about 4.75 miles 

east-northeast of Mansfield, Tarrant County (USGS 

11740), is referred to Cadulus Philippi. The tube as 

preserved is about 6 mm long, about 0.5 mm in diameter at the small end, increases to a maximum of 1.1 

mm about 4 mm from the small end, and apparently 

becomes slightly constricted as it nears the incomplete 

large end. The tube is gently and evenly curved and 

appears to be slightly compressed, with long axis at 

right angles to the plane of curvature. The specimen 

may be compared with the closely similar species, 

Cadulus praetenuis Stephenson, from the Templeton 

member of the Woodbine formation in Grayson County, 

Tex. (1952 [1953], p. 143). USNM 108860.

Class GASTROPODA

Genus PSEUDOMEIANIA Pictet and Campiche, 1862 

Pseudomelania? basicostata Stephenson, n. sp.

Plate 4, figures 4, 5

The three available specimens of this species are 

from Walnut Creek, 4.75 miles east-northeast of 

Mansfield, Tarrant County (USGS 11740). Shell 

small, spire of medium height with apical angle of 

about 34°, decreasing to about 25° on the larger whorls 

below. Protoconch not preserved. Suture sharply 

but not deeply impressed. Whorls 6 or 7; whorls of 

spire nearly flat on the sides, smooth except for obscure, 

microscopic spiral lining. Body whorl with a weak 

obtuse subangulation at the periphery. Basal slope 

steep, rounded in cross section, bearing on its lower 

two-thirds 3 or 4 flattish to round-crested spiral ribs, 

separated by narrower interspaces. Growth lines 

broadly convex in trend forward on the base, broadly 

concave forward above the periphery, slightly deflected 

backward just before reaching the suture above. 

Aperture not well preserved but apparently rather 

broadly lanceolate, with an acute angle at the rear and 

sharply rounded, though not channeled or notched at 

the front.

Dimensions of the incomplete holotype, the largest 

of the three shells: Height 10+ mm, diameter 4.5 mm.

The species is very much smaller than either P.? 

roanokana Stephenson or P. ? j'errata Stephenson, from 

the Woodbine formation of Texas, and also differs in 

having spiral costae on the base.

Types.—Holotype, USNM 108847; 2 unfigured paratypes, 

USNM 108858.

a39890—55———2

Genus IISPODESTHES White, 1877 

Lispodesthes lirata Stephenson, n. sp.

Plate 4, figures 6-11

The individuals of this species are present in considerable numbers in collections from two nearby 

localities on Walnut Creek, about 4.75 miles eastnortheast of Mansfield, Tarrant County (USGS 11740 

and 14580). The shell substance is very thin and 

fragile and it is impossible to separate any one individual in complete form from the hard matrix. However, nearly all the features needed for description can 

be seen in a selected series of more or less fragmentary 

shells.

Shell small, with plump body whorl and spire of 

medium height. Spiral angle about 46°, though somewhat variable on different individuals. Protoconch 

apparently low turbinate, with about 1% coils. Suture 

closely appressed in a shallow depression. Whorls 

4 or 5, gently convex on the side, expanding rather 

rapidly, bearing spiral lirae that may become covered 

with callus in adults. The body whorl of adults bears 

eight to twelve thin, low, threadlike spiral lirae, ranging 

from distinct to obscure and on different individuals 

from regularly to very irregularly spaced; those low on 

the base are most obscure. The growth lines are 

sinuous, being broadly convex in trend toward the 

front on the base and broadly concave forward on the 

side above the periphery.

The periphery and base are broadly rounded, the 

latter becoming rather steep below. Aperture longlanceolate, acutely angular at the rear, and passing in 

front into a rather long, narrow curved siphonal canal 

(beak). Outer lip broadly arched in the younger 

stages, expanding in adults into two pronglike projections. The upper of the projections is long and 

narrow and curves upward spurlike; on the body whorl 

one of the upper lirae, usually the third one below the 

suture, becomes more prominent as it approaches the 

aperture, and extends as a sharply upraised ridge out 

on the upper projection to its tip. The lower projection 

is broader, shorter, and may end in a blunt, inbent 

point; one of the basal lirae extends as a slightly raised 

ridge out onto this projection. A groove on the inner 

surface of each projection, the upper one the deepest, 

is a reflection of the ridge on the outer surface. In the 

adult the mantle of the living organism spread outward 

away from both the inner and the outer lip and secreted a layer of callus on the outer surface; in fully 

mature individuals callus may cover the entire shell, 

concealing the spiral lirae. In mature shells an anal 

channel incised in callus extends from the posterior 

angle of the aperture up the outer side of the spire to 

the apex.
58 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Dimensions of the incomplete holotype; Height 

14+mm, diameter, exclusive of the expanded lip, about 

8.5 mm. A larger incomplete paratype (pi. 4, fig. 9), 

whose expanded wing is not uncovered, measures: 

Height 17+mm, diameter 7+mm.

The species is similar to, and closely related to 

Lispodesthes panda Stephenson, from the Templeton 

member of the Woodbine formation, but the spire of 

L. lirata is a little higher, the sides of the whorls are 

plumper, the upper spur of the expanded lip is more 

slender and its degree of upward curvature is less, and 

there is less of a tendency for the shell to become completely covered with callus in the mature stage. L. 

patula Stephenson, also from the Templeton member, 

is larger and bears more numerous, finer, and more 

closely spaced spiral lirae.

A closely related species in the western interior is 

Lispodesthes nuptialis White, from beds that are 

correlated by J. B. Keeside, Jr., with the Carlile shale. 

It is there associated with the ammonite Collignoniceras 

woolgari (Meek) (—Prionotropsis woolgari Meek) in a 

paleontologic zone (Turonian) that is stratigraphically 

higher and younger than the basal beds of the Eagle 

Ford shale.

Types.—Holotype, USGS 11740, USNM 108856; 3 figured 

paratypes, USGS 11740, USNM 108862; 2 figured paratypes, 

USGS 14580, USNM 108857; 15 selected unfigured paratypes, 

USGS 14580, USNM 108867; 15 uhfigured paratypes, USGS 

11740, USNM 108837.

Occurrence.—At two adjacent localities on Walnut Creek, 4.75 

miles east-northeast of Mansfield, Tarrant County, Tex.

Genus CYLICHNA loven, 1846 

Cylichna? sp.

At one of the localities on Walnut Creek about 4.75 

miles east-northeast of Mansfield, Tarrant County 

(USGS 11740) several examples of a small gastropod 

having the form of Cylichna Loven occur. These are 

mostly internal molds with a thin film of soft calcareous 

shell material covering parts of them. No indication 

of spiral lirae can be detected. The shell is subcylindrical, broadly bulging in profile, the body whirl enveloping 

all the earlier whorls. One specimen about maximum 

size measures: Height 3 mm, diameter 1.5 mm. USNM 

108859.

Class CEPHALOPODA

Family DESMOCERATIDAE

Genus DESMOCERAS Zittel, 1884

Desmoceras? sp.

Plate 4, figures 12, 13

Two small incomplete ammonites from Walnut Creek, 

Tarrant County (USGS 11740), appear to belong to 

the Desmoceratidae, but are too immature to permit 

of their definite assignment to any one of the many

genera into which that family group has been subdivided. The shell is rather plump and smooth, the 

venter rather narrowly rounded, and the umbilicus 

small, though the coiling is not as close as it is in some 

members of the group. The ventral lobe is narrow and 

deep and the ventral saddle small and bluntly pointed. 

There are four relatively narrow complexly denticulate 

lateral saddles and four corresponding lobes; both lobes 

and saddles decrease rapidly in size from the venter to 

the line of involution. The figured specimen measures: 

Greatest diameter 9.5 mm, maximum radius center to 

venter 5.5 mm, dorsoventral diameter about 3.5 mm, 

corresponding transverse diameter about 4.5 mm. 

USNM 108830.

Family ACANTHOCERATIDAE

Genus ACANTHOCERAS Neumayr, 1875

Acanthoceras johnsonanum Stephenson, n. sp.

Plate 4, figures 14-17

This species is represented by one incomplete mediumsized specimen from Johnson County, which apparently 

includes little, if any, of the living chamber. The 

shell is plump, subsquarish in cross section, flattened a 

little on the flanks; the adult volution embraces onefourth or less of the preceding one. The ribs range 

from weak to moderately strong, becoming more prominent in the adult stage; they tend to alternate in prominence, about half of them reaching the umbilical 

shoulder in strength, where each bears a radially 

elongated, rather prominent node; the intervening ribs 

become weaker inward, some of them fading out before reaching the umbilical shoulder. The venter is 

broadly convex.

Each of the stronger ribs bears seven nodes, and most 

of the weaker intermediate ribs bear five nodes; the 

weakest rib noted bears only one very low midventral 

node. The nodes in the median row on the venter are 

of medium strength and slightly elongated in the 

younger stages, but become very weak and scarcely 

observable in the late adult stages. On each ventral 

angle there is a pair of nodes connected by a raised 

part of the supporting rib; in the early stages of growth 

the two paired nodes are cone shaped and subequal in 

strength and are a little more prominent than the 

midventral nodes; in the adult stage the outer node of 

each pair is a little the stronger and is slightly elongated 

radially. The suture is partly and not very clearly 

revealed. Enough can be seen to show that it is essentially acanthoceratid in pattern.

Diameter of holotype, as preserved 110 mm (estimated) maximum radius center to venter about 60 

mm; the dorsoventral diameter appears to be a little 

less than the corresponding transverse diameter at both 

the early and adult stages of growth.
BASAL EAGLE FORD FAUNA IN JOHNSON AND TARRANT COUNTIES, TEX. 59

The species is similar in size and form to Acanthoceras bellense Adkins, but in general is more strongly 

ornamented, having more numerous and more prominent ribs and nodes; a striking difference is the relative 

smoothness of A. bellense, especially in the area of the 

umbilical shoulder, on which the radially elongated 

nodes on the larger ribs are not only very weak but are 

set farther out on the flank from the line of involution 

than are the corresponding nodes on A. johnsonanum. 

Another difference is the cone-shaped outer node of 

the ventral pair on the adult of A. bellense in contrast to the radial elongation of the corresponding 

node on A. johnsonanum.

Holotype.—From north-facing slope of Mountain Creek 

Valley, 2.5 miles north-northeast of Alvarado, Johnson County, 

TJSGS 14583, TJSNM 108846.

Occurrence.—Recorded from the type locality only.

Genus TARRANTOCERAS Stephenson, n. gen.

Type species: Tarrantoceras rotatile Stephenson. 

Etymology: Tarrant County; Greek Kepas, a horn.

The features that characterize this new genus are: 

relatively small size; strong lateral compression; 

numerous, closely spaced radiating ribs that cross the 

venter with little or no diminution in size; seven rows 

of nodes on the earlier whorls, including a weak row of 

median nodes that fades out in adult stages; a row of 

nodes on each ventral angle; a row of weak nodes on 

each flank about one-third the width of the flank 

inward from the ventral angle, this row fading out forward on later stages; radially elongated nodes on the 

main ribs at the umbilical shoulder; suture with a moderately deep ventral lobe and short blunt ventral saddle, 

a broad, relatively low, bifid first lateral saddle with 

rounded, nondigitate subelements, a broad, shallow 

digitate lateral lobe, and a second lateral saddle similar 

to the first, but protruding farther forward on the 

flank; umbilicus one-third to two-fifths the total 

diameter of the shell.

The shell of Tarrantoceras, though similar in form 

and ribbing to that of Ammonites mantelli J. Sowerby, 

the genotype of Mantelliceras Hyatt, is more compressed 

than that species and possesses a different and simpler 

suture pattern. According to Wright and Wright 

(1951, p. 24, 37), Mantelliceras mantelli is restricted 

to the specimen figured by Sharp (1853, p. 40) in his 

plate 18, figures 7a-c; the suture shown in his figure 7c 

includes 3+ relatively narrow, high digitate saddles 

and part of a fourth saddle; in contrast the exposed 

suture of Tarrantoceras includes only two relatively 

low broad lateral saddles, the elements of which are 

rounded (nondigitate), separated by a relatively 

broad, shallow digitate lobe. Apparently Mantelliceras 

does not possess a medium row of ventral nodes.

In form and ornamentation Tarrantoceras rotatile, 

the genotype of this new genus, is very similar to 

Eucalycoceras pentagonum (Jukes-Browne), the genotype of Eucalycoceras Spath. The sutures, however, 

are markedly different in the two species, so different 

in fact that, in my opinion, they cannot be considered 

as congeneric. This opinion is based on a comparison 

of T. rotatile with an incomplete topotype of E. pentagonum from the Holaster subglobosus zone (Cenomanian) of England; in this English species the first 

and second lateral saddles are high and narrow and are 

separated by a deep, narrow, digitate lobe; the subelements of the saddles are narrowly rounded, almost 

digitate. In strong contrast the first and second 

lateral saddles of T. rotatile are low and broad, with 

broadly rounded subelements, and the intervening 

lobe is broad and shallow; this type of suture is consistent in the holotype and in five of the paratypes of 

T. rotatile, and also in the three other species of Tarrantoceras here recognized in the basal Eagle Ford 

of Tarrant and Johnson Counties. In other words, 

here is a group of four species possessing closely similar 

suture patterns, which differ markedly from the 

suture of the topotype of Eucalycoceras pentagonum 

cited above.

Tarrantoceras rotatile Stephenson, n. sp. 

Plate 5, figures 1-10

Shell small, coiled in one plane, each whorl embracing about the outer one-third of the flanks of the 

preceding whorl. Flanks compressed, being only 

slightly convex in cross section. Radial ribs closely 

spaced, numbering 44 on the largest whorl of the 

holotype; of these only 14 reach the umbilical shoulder 

in strength and bearing prominent shoulder nodes; 

the others are intercalated between the strong ribs 

and either die out well down on the flank, or reach the 

umbilical shoulder with weak unnoded termini. All 

the ribs are about equal in strength at the ventral angle. 

The number of smaller and weaker ribs between two 

strong ribs ranges from one to three. The ribs are 

gently sinuous, there being a slight curvature in trend 

backward well out on the flank and a slight bend forward as the ribs approach the ventral angle. Each 

rib as a whole is inclined a little forward, and all the 

ribs cross the venter with no diminution in strength.

In the earlier stages each strong rib bears seven 

nodes. There is a median row of ventral nodes that 

becomes weaker toward the front and dies out at a 

shell diameter of about 50 mm. Each rib bears a 

strong, beadlike node at each ventral angle; in the 

holotype these nodes tend to become weaker in the 

forward direction, but are still observable at its largest 

stage. On the ribs of each flank there is a row of
60 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

lateral nodes spaced about one third the width of the 

flank inward from the ventral angle; these nodes are 

much weaker than the nodes on the ventral angle and 

become weaker toward the front, disappearing at shell 

diameters of 30 mm or more on different individuals; 

this row is too far away from the ventral angle to be 

considered as paired with the row on that angle. A 

fairly prominent node elongated slightly in the radial 

direction is present on each strong rib at the umbilical 

shoulder.

In the holotype the living chamber is nearly completely represented and includes more than half the 

last whorl. The sutures nearest the inner end of the 

living chamber are well preserved. The ventral lobe 

is deep and broad, and has three principal and several 

minor digitations on each side, the lower ones forming 

a pair embracing the ventral saddle. The ventral 

saddle is short, rising about one-fourth as high as the 

lobe is deep; it is weakly trifid on its forward blunt end. 

The first lateral saddle is broad and relatively short and 

is divided by a short, narrow sublobe; each subsaddle 

thus formed is weakly trifid and the elements are 

broadly rounded, that is, nondigitate. The lateral 

lobe is smaller than the ventral lobe, and is short, broad 

and digitate. The second lateral saddle is nearly as 

large as the first, is similarly divided, protrudes forward on the flank, and extends to the line of involution.

Dimensions of the holotype: Diameter 61 mm; 

maximum radius center to venter 36 mm; dorsoventral 

diameter 21 mm; transverse diameter about 18 mm; 

maximum diameter of umbilicus 21 mm.

The species is closely related to Tarrantoceras 

sellardsi (Adkins), (=Mantelliceras sellardsi Adkins), 

from the Bouldin member of the Lake Waco formation 

(of Adkins and Lozo). It differs from that species in 

having more prominent ribs, wider umbilicus and 

smaller, beadlike nodes in the median ventral row in 

contrast to the coarser, more elongated nodes in the 

median ventral row of Adkin's species.

Types.—Holotype from Walnut Creek, 4.75 miles eastnortheast of Mansfield, Tarrant County, USGS 11740, USNM 

108835; 2 figured paratypes from the same source, USNM 

108854; 7 unfigured paratypes from the same source, USNM 

108863; 1 unfigured paratype, USGS 14580, USNM 108853; 

1 unfigured paratype, USGS 11740, USNM 108855.

Occurrence.—Walnut Creek, 4.75 miles east-northeast of 

Mansfield, Tarrant County, USGS 11740 (3 figured), 14580.

Tarrantoceras stantoni Stephenson, n. sp. 

Plate 5, figures 11-21

In the collection from Walnut Creek, Tarrant 

County (USGS 11740) are 15 more or less incomplete 

and fragmentary specimens that resemble Tarrantoceras 

rotatile Stephenson except that they differ in the details 

of their ornamentation, and slightly in form. The

largest specimen is nearly as large as T. rotatile but 

the shell is plumper, the radial ribs are fewer and not 

so closely spaced, the nodes are stronger in all the rows, 

presenting a subspinose effect, especially in the younger 

stages. The holotype is a specimen from near Lillian, 

Johnson County, furnished by J. P. Conlin.

The species is similar to T. rotatile in form and general appearance, in the number and spacing of the 

node rows, and in the pattern of the sutures. As in 

that species the nodes in the row on the flank become 

weaker forward and fade out in the later stages, and 

the nodes in the median row on the venter become 

weaker toward the front, and are wanting on the 

largest stage represented in the collection. The nodes 

on the ventral angles continue strong on all but the 

latest stage of adults. Several specimens representing 

young stages of growth indicate initial close coiling 

with an envelopment of more than half the preceding 

coil. In late stages the envelopment is one-fourth or 

less of the preceding coil.

Approximate dimensions of the holotype: Greatest 

diameter 60 mm, maximum radius center to venter 

36 mm, maximum dorsoventral diameter 25 mm, corresponding transverse diameter 18 mm. The diameter 

of the smallest specimen in the collection, which lacks 

the living chamber, is 7.5 mm.

Fragments among the paratypes from Johnson 

County indicate that individuals may attain somewhat 

larger size than the holotype, and may become plumper 

in late stages of growth. On one fragment of the large 

end of an adult (plate 5, fig. 21), senility is indicated 

by the weakening and closer spacing of the ribs and the 

shortening of the dorsoventral diameter.

The species is named in honor of the late Dr. Timothy 

W. Stanton.

Types.—The holotype, the most complete available specimen 

of this species, was generously supplied by J. P. Conlin, by 

exchange of the best, though less complete, specimen of the 

same species in the collection from Walnut Creek. Conlin 

found his specimen in a gully in a cultivated field about 1 mile 

north of Lillian, Johnson County, Tex. (USGS 24510, USNM 

108866). Three figured paratypes, USGS 11740, USNM 108861 ; 

11 unfigured paratypes, USGS 11740, USNM 108836. One 

figured paratype, USGS 14583, USNM 108845; 3 unfigured 

paratypes, USNM 108843.

Occurrence.—Walnut Creek, 4.75 miles east-northeast of 

Mansfield, Tarrant County, USGS 11740; north-facing slope of 

Mountain Creek Valley, 2.5 miles north-northeast of Alvarado, 

Johnson County, USGS 14583; an erosion gully in a cultivated 

field about 1 mile north of Lillian, Johnson County (J. P. Conin's loc. no. 4551).

Tarrantoceras lillianense Stephenson, n. sp. 

Plate 5, figures 22-27

This species is represented by nine specimens that 

possess features of form and sculpture intermediate 

between those of Tarrantoceras rotatile and those of
BASAL EAGLE FORD FAUNA IN JOHNSON AND TARRANT COUNTIES, TEX. 61

T. stantoni. Compared with the former the flanks are 

plumper, and in the adult stage the ribs are fewer, a 

little coarser and more widely spaced, and the nodes 

on the ventral angles and on the umbilical shoulders 

are a little coarser; the sutures are essentially identical, 

presenting shallow lateral lobes and broad, low saddles 

with rounded forward elements. Compared with T. 

stantoni the flanks are of about the same plumpness 

but the ribs are more numerous and weaker, and the 

nodes are much less conspicuous, lacking a spinose 

effect; on this species the ventrolateral rows of nodes 

are more closely spaced than they are on T. stantoni. 

The holotype is an incomplete internal mold (about 

half a volution) having some shell adhering, representing mainly the living chamber and bearing 22 radiating 

ribs. The imprint of part of the venter of the preceding volution is present on the inner curve of the 

specimen and a rubber cast of this imprint is shown in 

plate 5, figure 25. Dimensions of the holotype are: 

Greatest diameter 56 mm, dorsoventral diameter 20 

mm, corresponding transverse diameter 19 mm, diameter of umbilicus 20 mm. The figured paratype, 

representing a younger stage, measures: Greatest 

diameter 33 mm, radius center to venter 21 mm, 

dorsoventral diameter about 14 mm, corresponding 

transverse diameter about 14 mm, diameter of umbilicus 

10 mm.

Types.—Holotype from a gully in a field 1 mile north of 

Lillian, Johnson County (J. P. Conlin, collector), USGS 24510, 

USNM 108841; 1 figured paratype, USGS 11740, USNM 

108848; 7 unfigured paratypes, USGS 11740, USNM 108838.

Occurrence.—Walnut Creek, 4.75 miles east-northeast of 

Mansfield, Tarrant County; a concretion in an erosion gully 

about 1 mile north of Lillian, Johnson County.

Tarrantoceras multicostatum Stephenson, n. sp. 

Plate 6, figures 21-23

Two incomplete internal molds that possess the 

essential characters of Tarrantoceras Stephenson, differ 

specifically from T. rotatile Stephenson. The adults 

are somewhat larger than T. rotatile, are plumper 

on the flanks, more rounded on the venter and have 

smaller and weaker ventral nodes. The most striking 

difference, however, is the greater number of costae; 

30 costae can be counted on the large incomplete 

volution of the holotype (pi. 6, fig. 21), which includes 

less than half a turn; it is estimated that the complete 

volution must have possessed 60 or more costae, in 

contrast to the 44 counted on T. rotatile. The umbilical nodes on the larger costae are prominent and 

radially elongated. In the mold of the holotype of 

T. multicostatum a little more than half the living 

chamber is represented, back of which are parts of 

2 or 3 badly corroded sutures. In the paratype, which 

probably includes about half the living chamber, part

a39390—55———3

of the last suture is more clearly preserved than are 

the sutures in the holotype; as thus revealed the sutures 

appear to be essentially like those of T. rotatile. Except 

for their greater number and the smaller size of their 

nodes the costae of the present species are similar to 

those of T. rotatile; the number of smaller costae 

between the larger costae ranges from 2 to 4.

The approximate dimensions of the holotype as 

preserved are: Diameter, 67 mm, dorsoventral diameter 25 mm, corresponding transverse diameter, 

23 mm, maximum radius center to venter 41 mm, and 

maximum diameter of the umbilicus 28 mm.

Types.—Holotype, USNM 108844; paratype, USNM 108842.

Occurrence.—The holotype and paratype, the only available 

specimens, are from the north-facing slope of Mountain Creek 

Valley, 2.5 miles north-northeast of Alvarado, Johnson County, 

Tex. (USGS 14583).

Genus EUOMPHALOCERAS Spath, 1923

Type species: Ammonites euomphalus Sharpe

1923. Euomphaloceras Spath, Great Britain Geol. Survey ( 

Summary of Progress (1922), App. 2, p. 144.

1951. Euomphaloceras Spath. Wright and Wright, Paleont. 

Soc., Mon., London (revision of Sharpe's Mollusca of 

Chalk of England), p. 29, 36. (Includes synonymy of 

the genus.)

Acanthoceras lonsdalei Adkins (1928, p. 244) from 

the base of the Eagle Ford shale in Bell County, A. 

alvaradoense Moreman (1942, p. 205) from the same 

stratigraphic position in Johnson and Tarrant Counties, 

and A. eulessanum Stephenson (1952 [1953], p. 201) 

form the Lewisville member of the Woodbine formation 

in Tarrant County, appear to be American representatives of the genus Euomphaloceras Spath. The features 

that distinguish this genus from Acanthoceras Neumayr 

are: a median row of small ventral nodes that fade out 

in later stages; typically these nodes number two or 

more times as many as the nodes in either of the two 

adjacent rows of ventrolateral nodes; however, the 

comparative number of the small nodes in the median 

row is extremely variable in different species; the 

nodes in the outer ventrolateral row (farthest from the 

midline of the venter) are much more prominent than 

those of the corresponding row in Acanthoceras, and 

these outer nodes increase in prominence in the later 

stages of growth becoming strikingly prominent in 

large adults; in general the system of ribs and nodes in 

Acanthoceras is more regular than in Euomphaloceras.

J. P. Conlin, of Burleson, Tex., has shown me a 

fragment of a large ammonite (specimen 4621 in his 

private collection), which possesses an unusual ventral 

feature. The large prominent nodes of this specimen 

seem to ally it with the genus Euomphaloceras, but its 

specific identity was not determined. The fragment
62 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

pertains to the living chamber probably just back of 

the aperture. The specimen is subquadrate in cross 

section, with dorsoventral diameter of about 105 mm 

and corresponding transverse diameter between the 

ribs of about 95 mm. The ribs on the flank are nonprominent and widely separated and bear moderately 

prominent, somewhat elongated nodes on the umbilical 

shoulder. The fragment includes two ribs on the flank, 

each bearing a large prominent node on the ventral 

angle, with a third rib, the one farthest forward partly 

broken away on the flank, but with the ventral portion 

intact. The two pairs of nodes farthest from the aperture are connected by broad, gentle swells of the otherwise smooth ventral surface. In striking contrast the 

two nodes farthest forward are connected by a prominent transverse ridge that rises wall-like across the 

venter.

Another large specimen in Conlin's private collection 

(5560), probably also a species of Euomphaloceras, from 

the classic Bird Creek locality in Bell County, possesses 

a closely similar wall-like feature on the venter between 

1 the two nodes farthest forward. Conlin also reports 

a poorly preserved specimen, probably Euomphaloceras 

alvaradoense (Moreman), from 4 miles south of Alvarado, which shows the same wall-like feature between 

the two anterior nodes. This feature, having been 

observed in three specimens from three widely separated 

basal Eagle Ford localities, is obviously not rare in 

large ammonites at that stratigraphic position. The 

location of the feature near the aperture of the shell 

suggests that it may be some sort of a gerontic manifestation; since, however, gerontic features usually take 

the form of constrictions, rather than expansions, the 

real biologic meaning of the wall-like ventral ridge 

connecting the two anterior ventral nodes remains to 

be determined.

Euomphaloceras lonsdalei (Adkins)

Plate 6, figures 6-20

1928. Acanthoceras lonsdalei Adkins, Tex. Univ. Bull. 2838, 

p. 244, pi. 26, fig. 5; pi. 27, fig. 3.

1942. Acanthoceras lonsdalei Adkins. Moreman, Jour. Paleontology, v. 16, no. 2, p. 204.

The holotype of Euomphaloceras lonsdalei (Adkins) is 

a medium-sized specimen having a diameter of 110+ 

mm; the specimens from Tarrant and Johnson Counties 

are smaller than the holotype; one fragment from Bell 

County, a topotype, pertains to a specimen larger 

than the holotype. The largest available measurable 

topotype is 44+ mm in diameter and the diameter of 

the smallest specimen, from Tarrant County is 8.5 mm; 

the available specimens present a nearly complete 

range in size between these extremes. Assuming that 

all these specimens are correctly referred to Adkin's

species, a considerable individual variation in the size 

and distribution of the nodes and costae, and in minor 

details of the suture patterns, is indicated.

The holotype as now available to me is incomplete; 

the anterior part of the holotype as shown in Adkins 

original figure presumably is lost; it probably included 

part of the living chamber; at any rate the broken large 

end of the holotype in its present condition shows 

traces of a septum that may have been the last one 

immediately back of the living chamber.

Using the available part of the holotype, two topotypes, and 20 or more smaller specimens from sandy 

limestone at the base of the Eagle Ford shale in Tarrant 

and Johnson Counties, a more detailed description of 

the species may be given than was possible with the 

original material. The shell is medium sized, exceeding 

a measured diameter of 110 mm. It is plump, broad 

and broadly rounded on the venter, and flattish on the 

flanks. In the early stages of growth the advancing 

shell envelopes more than half of the preceding volution, 

but in the later stages the degree of envelopment may 

be one-third or less the width of the flank. The ribs 

are weak to medium strong except as they are made 

prominent by nodes on the ventral angles and flanks. 

The ribs present on the flanks number 14 or 15 to the 

volution; in adults they trend nearly directly across 

the flanks, but in the younger stages they bend forward 

at the ventral angles; 7 or 8 larger ribs extend inward 

in strength to the umbilical shoulder, but in larger 

specimens the number reaching the shoulder may increase to 12 or 13; intermediate smaller ribs, which may 

be weak or of ordinary strength at the ventral angles, 

die out on the flanks before reaching the umbilical 

shoulder, or about at the shoulder. On the venter in 

each space between the larger ribs of adults are one or 

two additional weak transverse ribs; these are few or 

wanting in the small, early stages of the shell.

The larger ribs that reach the umbilical shoulder 

bear prominent, radially elongated nodes at their 

inner ends. Each of the larger ribs bears a pair of 

rather widely separated nodes at each ventral angle; 

the inner node of each pair (nearest the midline of the 

venter) is the smaller and is slightly elongated parallel 

to the venter; the outer node is prominent, cone shaped, 

and the successive nodes of this row increase in prominence in the forward direction; the nodes in the median 

row on the venter are smaller and more numerous than 

those in either of the lateral ventral rows; in this median 

row there is one small node on each rib, whether large 

or small, that crosses the venter; on the smaller ribs 

on the venter there may or may not be a small ventrolateral node in line with the inner lateral row of nodes.

The sutures are not observable on the holotype nor 

on the smaller of the two topotypes. Traces only of
BASAL EAGLE FORD FAUNA IN JOHNSON AND TARRANT COUNTIES, TEX. 63

the sutures appear on the larger topotype. Sutures 

are well preserved on the small plesiotypes and on 

several of the selected examples. Ventral lobe deep 

and rather wide, with parallel digitate sides, ending 

below in two longitudinal prongs that enclose a squarish 

ventral saddle; the latter rises about one-third as high 

as the lobe is deep, its blunt forward end indented 

with one or more small notches; first lateral saddle 

broad, about as high as the ventral lobe is deep, and 

rendered bifid by a small, narrow sublobe; each subsaddle thus formed is subdivided into three parts by 

small lobules; each of the small elements of the saddle 

formed by the sublobe and lobules is simple and 

rounded on its front; the first lateral lobe is rather 

broad, digitate, and shallower than the ventral lobe; 

the second lateral saddle is much smaller than the first 

and in the early stages of the shell is broken into three 

small, simple elements by lobules; the second lateral 

lobe is small with three digitations; two small, simple 

saddles separated by a small, pointed lobe intervene 

between the second lateral lobe and the line of involution; in the stage reached by the largest of the four 

plesiotypes from Tarrant County the saddles are 

rendered somewhat less simple by the appearance of 

additional small lobules or notches. «

Dimensions of the part of the holotype that is available for measurement: Diameter 85 mm; maximum 

radius from center to venter about 53 mm; dorsoventral diameter of volution at broken end 35 mm; 

corresponding transverse diameter about 45 mm; 

diameter of umbilicus about 28 mm. The maximum 

diameter of the holotype, including the part at the 

large end that appears on the original illustration and 

now presumed to be lost, is 110+ mm.

Types.—Holotype, Bureau of Economic Geology, Austin, 

Tex., 2410; 2 plesiotypes ( = topotypes), USGS 11845, USNM 

108831; 4 plesiotypes, USGS 11740, USNM 108824; 9 selected 

examples, USGS 11740, USNM 108823.

Occurrence.—Holotype and two topotypes, Bird Creek near 

Belton-Temple Highway, about 4 miles east-northeast of Belton, 

Bell County; north-facing slope of Mountain Creek Valley, 2.5 

miles north-northeast of Alvarado, Johnson County, USGS 14583; 

Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant 

County, USGS 11740.

Euomphaloceras alvaradoense (Moreman) 

Plate 7, figures 1-9

1942. Acanthoceras alvaradoense Moreman, Jour. Paleontology, 

v. 16, no. 2, p. 205, pi. 32, fig. 6; text fig. 2, O, T.

This species occurs in considerable numbers at two 

localities (USGS 11740, 14580) hi Tarrant County 

and at a locality (USGS 14583) in Johnson County 

about 6.5 miles north of the type locality of the species. 

The specimens range from fragmentary to nearly 

complete in form, and from a minimum diameter of

about 16 mm to about 100 mm. However, one large 

internal mold of about the posterior half of a living 

chamber, found loose in the bed of Walnut Creek at 

one of the outcrops of the basal beds of the Eagle 

Ford shale in Tarrant County (USGS 14582), is interpreted to represent an adult stage of the species; 

the dorsoventral diameter of the volution at the large 

end of this fragment is 78 mm and the corresponding 

transverse diameter is about 80 mm.

The features that indicate the closer relationship of 

the species to Euomphaloceras Spath than to Acanthoceras Neumayr are the large nodes composing the 

outer of the two ventrolateral rows of nodes, which 

increase regularly to large size as growth proceeds, 

and occasional small intermediate ribs and nodes between the regular ribs on the venter. Of the two species 

of Euomphaloceras in the basal beds of the Eagle Ford 

shale this species is least like the genotype, E. euomphalum, in that there is only a meager development 

of small medial ventral nodes.

Form plump, cross section subquadrate, flanks and 

venter gently convex; ribs nearly direct, 16 or more to 

the volution in early stages, 12 or 13 in later stages, 

ranging from weakly developed to medium strong on 

different individuals. In the early stages a pair of 

ventrolateral nodes is present on each ventral angle 

of each main rib, the inner one (nearest the midline 

of the venter) slightly elongated and equal to or larger 

than the outer one, which is cone shaped or slightly 

elongated; the nodes of each pair are joined by a slightly 

higher swelling of the rib on which it stands, and the 

outer node leans away from the venter at an angle of 

about 45 degrees; as growth proceeds the inner nodes 

on the inner row gradually become weaker and eventually coalesce with those in the outer row to form large 

cone-shaped nodes that continue to increase hi strength 

to the largest observed stage of growth. The complete coalescence is accomplished on different individuals at shell diameters ranging from 65 to 90 

mm. A median row of ventral nodes is present in early 

stages; these nodes are cone shaped or slightly elongated, 

weak, and die out on different individuals at different 

stages of growth, usually at a shell diameter of 65 

mm or less, but may be represented by weak swellings 

at diameters as great as 125 mm; most of the nodes in 

the median row lie in alinement with nodes in the 

ventrolateral rows on the main ribs, but additional 

weaker nodes may be present on weak intermediate 

ventral ribs. Nearly all the main ribs bear radially 

elongated nodes on the umbilical shoulders.

The suture pattern is not observable on some of the 

specimens but may be clearly seen on others, especially 

on some of the smaller ones. The suture is of the acanthoceratid pattern. There is a deep, quadrangular,
64 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

digitate ventral lobe; a short quadrangular ventral 

saddle enclosed between two straight terminal prongs 

of the ventral lobe, the forward end divided by one, 

two, or three shallow notches; first lateral saddle broad, 

divided into two subsaddles by a small digitate sublobe, 

the subsaddles further divided by lobules into three 

small denticulate elements rounded on the front; first 

lateral lobe relatively small, digitate; second lateral 

saddle relatively small with three or four rounded small 

denticulate elements; another very small lobe or lobule 

is followed by two or three small saddles separated by 

small lobes, to the line of involution.

Dimensions of holotype: Diameter 125 mm; maximum radius center to venter about 76 mm; dorsoventral diameter 45 mm; transverse diameter measured 

on ribs 52 mm; between ribs 45 mm; diameter of 

umbilicus 37 mm. A medium-sized incomplete individual, with about half the living chamber represented, measures: Diameter 89 mm; maximum radius 

center to venter about 52 mm; dorsoventral diameter 

at large broken end 34 mm; corresponding transverse 

diameter of volution measured on ribs about 40 mm; 

maximum diameter of umbilicus about 28 mm. The 

large fragment of an internal mold representing about 

half of the living chamber, previously mentioned, 

probably indicates that adults of the species attained a 

diameter of 270 mm or more.

Types.—The holotype, from Johnson County, 4 miles south of 

Alvarado, the only specimen available at the time of the original 

description, is in the Moreman collection at the Bureau of 

Economic Geology, University of Texas, Austin, Tex. (BEG 

19801). Two plesiotypes, USGS 11740, USNM 108822; 1 

plesiotype, USGS 14582, USNM 108828; 1 plesiotype, USGS 

14583, USMN 108825; 12 selected examples, unfigured, USGS 

14583, USNM 108826; 4 selected examples, unfigured, USGS 

14580, USNM 108827; 6 selected examples unfigured, USGS 

11740, USNM 108829.

Occurrence.—Walnut Creek, about 4.75 miles east-northeast 

of Mansfield, Tarrant County, USGS 11740, 14580, and 14582; 

north-facing slope of Mountain Creek Valley, 2.5 miles northnortheast of Alvarado, Johnson County, USGS 14583; 4 miles 

south of Alvarado (holotype).

Genus BORISSIAKOCERAS Arkhanguelsky, 1916

1916. Borissiakoceras Arkhanguelsky, Com. geol. Petrograd 

Mem., (N. S.), v. 152, p. 55, pi. 8, figs. 2, 3.

1935. Borissiakoceras Arkhanguelsky. Morrow, Jour. Paleontology, v. 9, No. 6, p. 463-465. (Genus discussed in 

connection with the description of the species, B. 

reesidei Morrow.)

In its general form, its rounded venter, the presence 

of a row of short, oblique nodes on the ventral angle, 

the essential similarity of its sutures, and the presence 

of lateral and ventral crests, the species Borissiakoceras 

orbiculatum Stephenson agrees closely enough with the 

genotype, B. mirabile Arkhanguelsky, to indicate a congeneric relationship. In Grayson County, Tex., the

genus has been recognized stratigraphically as high as 

the Metoicoceras whitei zone of the Eagle Ford shale 

(USGS 14555). One fragment of an ammonite from 

the Lewisville member of the Woodbine formation, 

identified as Euhoplitesl sp. (Stephenson 1952 [1953], 

p. 198, pi. 45, figs. 5, 6) should have been referred to 

Borissiakoceras.

Morrow (1935, p. 463-465) referred two species from 

the Upper Cretaceous of the western interior to 

Borissiakoceras, one, B. reesidei, from the upper part 

of the Graneros shale, south of Wilson, Elsworth 

County, Kans., and the other, B. aplatum, from the 

upper part of the Blue Hill shale member of the Carlile 

shale, south of Tipton, Mitchell County, Kans. As 

figured, both of these species are less compressed and 

more rounded on the venter than B. orbiculatum, and 

they both lack ventrolateral nodes. Specimens from 

the western rim of the Black Hills in Wyoming (USGS 

12649), obtained from a dark limestone concretion in 

beds correlated by Cobban and Keeside (1952 cor. 

chart) with the lower part of the Greenhorn limestone, 

(pi. 6, fig. 5), are very similar in form and suture pattern 

to B. orbiculatum, but most of the individuals have a 

less conspicuous development of the ventral nodes; 

however, weak nodes are present and on some the nodes 

are stronger than on others. This difference, though 

slight, appears to be fairly consistent in a dozen or more 

individuals and with the limited available material it 

seems advisable to regard the Black Hills specimens as 

belonging to a separate undescribed species. There is 

also an undescribed species of Borissiakoceras from a 

Cretaceous locality 1 mile northeast of Wilcox, Wyo.; 

it has a thin disklike form, an excavated venter, a 

narrower umbilicus, and a more elaborate suture pattern, than has B. orbiculatum.

Borissiakoceras orbiculatum Stephenson, n. sp.

Plate 6, figures 1-4

This species is represented in the basal beds of the 

Eagle Ford shale by three specimens from Walnut 

Creek, Tarrant County, Tex. (USGS 11740). Shell 

small, strongly compressed, rounded on the venter, 

each volution enveloping about three-fifths of the preceding one. Flanks flat, diverging slightly outward; 

ribs represented by obscure, widely spaced, gently 

sigmoidal undulations, each with a short node, oblique 

forward, at each ventral angle. No other nodes present. 

Venter nearly semicircular in cross section at early 

stages, obtusely subangular at each edge in later stages. 

On a juvenile stage of one of the three specimens evidence of a small, threadlike ventral keel was noted on 

the exterior of the shell, but this keel was accidentally 

destroyed in preparation; it was not reflected on the 

underlying internal mold. Two specimens of the closely
BASAL EAGLE FORD FAUNA IN JOHNSON AND TARRANT COUNTIES, TEX. 65

related, undescribed species from the western rim of 

Black Hills, Wyo., previously mentioned, each bears an 

imprint of a small, threadlike, evenly beaded ventral 

keel at an.early stage of growth; among the 16 specimens from this locality these 2 are the only ones that 

reveal the presence of a keel. Growth lines gently 

sigmoidal on each flank indicate a weak lateral crest; 

the growth lines also indicate a rather pronounced 

ventral crest. Umbilicus small, about one-fourth the 

diameter, with steep, rounded sides.

The sutures are not clearly revealed on the holotype, 

which is chosen for its size and perfection of form, 

but are uncovered on one small paratype. The ventral 

lobe is broad, simple, and of moderate depth; the ventral 

saddle is simple, broadly rounded, and about one-third 

as high as the lobe is deep. The lateral suture pattern 

is simple; the first lateral saddle is rendered bifid by 

a shallow notch; the first lateral lobe is much smaller 

than the ventral lobe and may be simple or weakly 

bifid; the second lateral saddle is about as broad as the 

first and is similarly bifid; the second lateral lobe is 

about as deep as the first, but is narrower and is simple; 

between this lobe and the line of involution are two 

smaller simple saddles separated by a shallow simple 

lobe. One specimen of the closely related species 

from the locality on the western rim of the Black Hills, 

shows the sutures at a later stage of growth perfectly 

preserved (pi. 6, fig. 5); they are like the suture in B. 

orbiculatum except that two or three additional small 

notches appear in the lateral saddles.

Dimensions of the holotype, an individual that 

probably includes most of the living chamber: Diameter 

22.5 mm, maximum radius center to venter 14 mm, 

dorsoventral diameter of volution near the aperture 

about 9 mm, corresponding transverse diameter about 

4.5 mm, width of volution from line of involution to 

venter near aperture 11 mm, maximum diameter of 

umbilicus about 5 mm.

Types.—Holotype, USNM 108832; 2 figured paratypes, 

USNM 108833. Borissiakoceras sp., from western rim of Black 

Hills, Wyoming, figured for comparison of sutures, USGS 12649, 

USNM 108834.

Occurrence.—Found only at the type locality on Walnut 

Creek, 4.75 miles east-northeast of Mansfield, Tarrant County 

(USGS 11740). Adkins (1933, p. 433) lists the genus Borissiakoceras, n. sp., from Walnut Creek, but does not state the 

exact locality.

LITERATURE CITED

Adkins, W. S., 1923, Geology and mineral resources of McLennan 

County: Tex. Univ. Bull. 2340, 202 p., 4 pis., geol. map.

———— 1928, Handbook of Texas Cretaceous fossils: Tex. Univ. 

Bull. 2838, 303 p., 37 pis.

1933, The geology of Texas; pt. 2, The Mesozoic systems

in Texas: Tex. Univ. Bull. 3232, p. 239-518 (esp. p. 

423-432).

Adkins, W. S., and Arick, M. B., 1930, Geology of Bell County, 

Texas: Tex. Univ. Bull. 3016, 92 p., 2 figs., geol. map.

Adkins, W. S., and Lozo, F. E., 1951, Stratigraphy of the Woodbine and Eagle Ford, Waco area, Texas, in Adkins, W. S., 

and others, 1951, The Woodbine and adjacent strata of the 

Waco area of Central Texas: Fondren Sci., Ser. 4, [Dallas], 

p. 101-164, 6 pis., 26 figs.

Cobban, W. A., and Reeside, J. B., Jr., 1952, Correlation of the 

Cretaceous formations of the western interior Of the United 

States: Geol. Soc. America Bull., v. 63, p. 1011-1044, folding chart.

Jukes-Browne, A. J., and Hill, W. M., 1896, A delimitation of 

the Cenomanian—being a comparison of the corresponding 

beds in southwestern England and western France: Geol. 

Soc. London Quart. Jour. v. 52, no. 206, p. 99-178 (esp. 

p. 156, pi. 5, fig. 1).

Moreman, W. L., 1927, Fossil zones of the Eagle Ford of north 

Texas: Jour. Paleontology, v. 1, no. 1, p. 89-101, pis. 13-16.

———— 1933, quoted in Adkins, W, S., The Geology of Texas; pt. 2, 

The Mesozoic systems in Texas: Tex. Univ. Bull. 3232, p. 

425-426.

1942, Paleontology of the Eagle Ford group of north and

central Texas: Jour. Paleontology, v. 16, no. 2, p. 192-220, 

pis. 31-34, 2 figs.

Morrow, A. L., 1935, Cephalopods from the Upper Cretaceous 

of Kansas: Jour. Paleontology, v. 9, no. 6, p. 463-473, pis. 

49-53, figs. 1-8.

Sharpe, Daniel, 1853, Description of the fossil remains of Mollusca found in the Chalk of England, pt. 1, Cephalopoda: 

Palaeont. Soc. Mon., London, 70 p., 27 pis.

Spath, L. F., 1923, On the ammonite horizons of the Gault and 

contiguous deposits: Great Britain Geol. Survey Summary 

of Progress (1922), app. 2, p. 139-149.

Stephenson, L. W., 1946, Alunite at Woodbine-Eagle Ford contact in northeastern Texas: Am. Assoc. Petroleum Geologists Bull., v. 30, no. 10, p. 1764-1770.

———— 1952 [1953], Larger invertebrate fossils of the Woodbine 

formation (Cenomanian) of Texas: U. S. Geol. Survey 

Prof. Paper 242, 226 p., 59 pis.

1953, Mollusks from the Pepper shale member of the

Woodbine formation: U. S. Geol. Survey Prof. Paper 243-E, 

p. 57-68, pi. 13.

Wright, C. W., and Wright, E. V., 1951, A survey of the fossil 

Cephalopoda of the Chalk of Great Britain: a revision of 

Sharpe (1853) Description of the fossil remains of Mollusca 

found in the Chalk of England, pt. 1, Cephalopoda: Palaeont. 

Soc. Mon., London, p. 1-40.

INDEX

A Page 

Abstract-_-____--_____-_-_____ 53

Acanthoceras..........-......................... 54,58

alvaradoense.......................... 53,55,61,63

barcusi...................................... 54

bettense..................................... 53,59

eulessanum................................. 61

johnsonanum....................... 55,58,59; pi. 4

lonsdalei................................. 53,61,62

pepperense.................................. 53

stephensoni................................. 53

validum..................................... 53

sp___--._-.__-.___________.___ 55 

Acanthoceratidae__.__--------______ 58

alvaradoense, Acanthoceras................. 53,55,61,65

Euomphaloceras................. 54,55,62,65; pi. 7

Ammonites euomphalus......................... 61

mantelli-. ___________.__,___ 59 

aplatum, Borissiakoceras........................ 64

arvanus, Inoceramus....................... 54,55; pi. 4

B 

barcusi, Acanthoceras............................ 54

Euomphaloceras............................ 54

basicostata, Pseudomelania................... 67; pi. 4

bettense, Acanthoceras........................... 53,59

Bluebonnet flag member of Lake Waco shale. 53,54,55 

Borissiaokceras.................................. 64

aplatum.. __..__..-_-___-__.-_.. 64 

mirabUe.—..-.............................. 64

orbiculatum........................ 55,64,65; pi. 6

reesidei..................................... 64

sp................................. 55,64,66; pi. 6

Bouldin flag member_______. ___. __ 53,56 

Brevicardium................................... 56

sp._-------_____.--_------___----- 66

G

Cadulus.......

praetenuis.

sp.

Caestocorbula.. 

crassiplica.

........................... 67

......----------_........ 57

___.--_--.._.__-_._.-. 67

........................... 66

........................... 56

. — — — — — — __——_ 66

Carlile shale....-_____. —...................... 58,64

Cottignoniceras woolgari........-................. 58

cdlumbella, Exogyra.......................... 54,55,56

crassiplica, Caestocorbula........................ 56

Cylichna........................................ 55,68

sp.......................................... 55,58

sp.

D

Desmoiceras.....

sp..........

Desmoceratidae -

58

8; pi. 4 

58

E

Eagle Ford shale...-.______________ 53 

flag member._-____.-_---___-.. 53

Eucalycocerasleonense.-........................ 53,54

pentagonum................................ 59

sp___.._____-„--——________.. 55

[Italic numbers indicate descriptions]

Euhoplites sp.________________------ 64

eulessanum, Acanthoceras....................... 61

Euomphaloceras............................ 54

Euomphaloceras.-.............................. 61

alvaradoense..................... 54,55,62,65; pi. 7

barcusi------... ..._--..__----------__ 54

eulessanum-.-.............................. 54

euomphalum................................ 63

lonsdalei............................ 54,55,62; pi. 6

euomphalum, Euomphaloceras................... 63

euomphalus, Ammonites........................ 61

Exogyra........................................ 66

columbetta............................... 54, 55,56

P

{errata, Pseudomelania. 

fragilis, Inoceramus.-..

Oraneros shale—----- 

Greenhorn limestone. 

Gymnentome valida....

H

Inoceramus--................................... 66

arvanus............................_ 54,55; pi. 4

fragilis...................................... 54

johnsonanum, Acanthoceras............. 55,58,59; pi. 4

L

Lake Waco shale.._-______._____ 53 

subunits of-___-______..--._.._ 53,55

Lewisville member of Woodbine formation _. _ 53,

54,55, 56,61,64 

littianense, Tarrantoceras.................. 55, 60; pi. 5

lirata, Lispodesthes..................... 55, 67, 58; pi. 4

Lispodesthes.................................... 67

lirata.............................. 55, 67, 58; pl.4

nuptialis—................................. 58

panda.............. ......._____.___ 58

patula...................................... 58

List of fossils from basal beds of Eagle Ford shale. 55

Localities, Johnson County____.---__.. 55

Tarrant County..--.__._.-..___ 54

Walnut Creek-.------.-------------------- 54

lonsdalei, Acanthoceras. ____________ 53,61,62 

Euomphaloceras.................... 54, 55, 62; pi. 6

M 

mantelli, Ammonites............................ 59

Mantelttceras.-............................. 59

Mantetticeras mantelli........................... 59

sellardsi..................................... 53,60

Metoicoceras whitei.............................. 64

mirabile, Borissiakoceras..............-------__ 64

multicostatum, Tarrantoceras.............. 55, 61; pi. 6

N 

nuptialis, Lispodesthes........................... 58

orbiculatum, Borissiakoceras............ 55, 64, 65; pi. 6

Ostrea. --...----.—-——-.-- — .— 54,56

soleniscus.

SP-.-- ——-

55

55,56

panda, Lispodesthes............................. 58

patula, LUpodesthes......................___ 58

pentagonum, Eucalycoceras...................... 59

Pepper formation____..._____.--.. 53

pepperense, Acanthoceras.........._____.... 53

praetenuis, Cadulus............................. 57

Prionotropsis woolgari........................... 58

Protarca tramitensis............................. 55

Pseudomelania.................................. 67

basicostata....................______ 67; pi. 4

ferrata...................................... 57

roanokana.................................. 57

Ptychodus...................................... 54

R 

Reeside, J. B., Jr...__-...-.-_.-------..--.- 54

reesidei, Borissiakoceras...-..................... 64

Ripley formation_______..„_______ 56 

roanokana, Pseudomelania........______. 57

rotatile, Tarrantoceras............... 55, 69, 60,61; pi. 5

sellardsi, Mantitticeras............... _____. 53,60

Tarrantoceras.................... ...—.—— 55,60

soleniscus, Ostrea............................... 55

South Bosquemarl-__...————.—.——— 53 

Stanton, T. W., quoted-—-------------------- 54

stantoni, Tarrantoceras-................ 55, 60, 61; pi. 5

stephensoni, Acanthoceras....................... 53

Stratigraphic sections..._..-—__———.. 54 

subglobosus, Holaster............................ 59

Tarrant formation..........__.._.._._. 53,54

Tarrantoceras................................... 69

liHianense............................. 55, 60; pi. 5

mutticostatum......................... 55, 61; pi. 6

rotatile......................... 55, 69, 60, 61; pi. 5

sellardsi..................................... 55,60

stantoni............................ 55,60, 61; pi. 5

tramitensis, Protarca-.--- ........— ————— --. 55

valida, Gymnentome..... 

validum, Acanthoceras- 53

W

whitei, Metoicoceras...————————— 64

Woodbine formation...-.----.-..... 53,54,55,56,57, 58

woolgari, CoUignwiiceras......................... 58

Prionotropsis..-............................ 58

67

PLATES 4-7
PLATE 4

[Figures natural size except as indicated]

FIGURES 1-3. Inoceramus arvanus Stephenson (p. 55).

1. Internal mold from concretion in field 2.5 miles north-northeast of Alvarado, Johnson County. USGS 14583. 

USNM 108840.

2. Internal mold from Walnut Creek, about 4.75 miles east-northeast of Mansfield, Tarrant County. USGS 11740, 

USNM 108849.

3. Internal mold from Bird Creek, 4 miles east-northeast of Belton, Bell County. USGS 11845, USNM 108864. 

4-5. Pseudomelania? basicostata Stephenson, n. sp. (p. 57).

Views of the holotype, X3, from Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant County. USGS

11740, USNM 108847. 

6-11. Lispodesthes lirata Stephenson, n. sp. (p. 57).

6. Holotype, X2, from Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant County. USGS 11740,

USNM 108856. 

7-9. Views of 3 paratypes (each X2) from the same source. USNM 108862.

10. A paratype, X2, from a locality on Walnut Creek near the preceding locality. USGS 14580, USNM 108857.

11. Inner view of a paratype, X2, from the same source, showing groove under upper prong of expanded lip.

USNM 108857. 

12-13. Desmoceras? sp. (p. 58).

12. Internal mold, X3, coated for photographing, from Walnut Creek, 4.75 miles east-northeast of Mansfield, 

Tarrant County. USGS 11740, USNM 108830.

13. The same specimen, uncoated, to show sutures. 

14-17. Acanthoceras johnsonanum Stephenson, n. sp. (p. 58).

14. 15. Views of holotype, from concretions in a field, 2.5 miles north-northeast of Alvarado, Johnson County. 

USGS 14583, USNM 108846.

16. View of partly uncovered inner volution of holotype.

17. Back view of inner volution of holotype.
GEOLOGICAL SURVEY PKOFESSIONAL PAPEK 274 PLATE 4 

"" ->

14

INOCERAMUS, PSEUDOMEIANIA?, LISPODESTHES, TARRANTOCERAS, DESMOCERAS, AND ACANTHOCERAS
PLATE 5

[Figures natural size except as indicated]

FIGURES 1-10. Tarrantoceras rotatile Stephenson, n. sp. (p. 59).

I-3. Views of the holotype, coated, from Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant County. 

USGS 11740, USNM 108835.

4. Side view of holotype, uncoated,to show sutures.

5. View of part of venter of holotype, uncoated, to show sutures.

6. 7. Views of an incomplete paratype, from the same source, USNM 108854. 

8-10. Views of a small paratype, from the same source, USNM 108854. 

11-21. Tarrantoceras stantoni Stephenson, n. sp. (p. 60).

II-13. Three views of the holotype, from gully in field 1 mile north of Lillian, Johnson County. USGS 24510,

UNSM 108866. 

14, 15. Views of a small paratype, X3, from Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant

County. USGS 11740, USNM 108861. 

16, 17. Views of a small paratype from the same source. USNM 108861.

18. A small paratype, X3, coated, from the same source, USNM 108861.

19. 20. Views of the same paratype, X 3, uncoated to show sutures.

21. An incomplete specimen, from concretions in a field, 2.5 miles north-northeast of Alvarado, Johnson County,

to show gerontic features near aperture. USGS 14583, USNM 108845. 

22—27. Tarrantoceras lillianense Stephenson, n. sp. (p. 60).

22. 23. Views of the holotype, from gully in field 1 mile north of Lillian, Johnson County. USGS 24510, USNM 

108841.

24. Back ventral view of the holotype.

25. View of rubber cast made from imprint on inner curve of holotype.

26. 27. Views of a paratype, from Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant County. USGS 

11740, USNM 108848.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 274 PLATE 5

23

TARRANTOCERAS
PLATE 6

[Figures natural size except as indicated]

FIGUKES 1—4. Borissiakoceras orbiculatum Stephenson, n. sp. (p. 64).

1. Holotype, X2, from Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant County, USGS 11740, 

USNM 108832.

2. 3. Side and back ventral views of a paratype, X2, from the same source, USNM 108833. 

4. Side view of a paratype, X4J-2, showing sutures, from the same source, USNM 108833. 

5. Borissiakoceras sp. (p. 64).

View, X2, of specimen from western rim of Black Hills, Wyo., USGS 12649, USNM 108834. Inserted for comparison with B. orbiculatum. 

6-20. Euomphaloceras lonsdalei (Adkins), (p. 62).

Six specimens shown in the order of size from largest to smallest.

6. Ventral view of fragment from septate portion of a large topotype, from Bird Creek, 4 miles east-northeast of 

Belton, Bell County. USGS 11845, USNM 108831.

7. 8. Views of another smaller topotype, USNM 108831.

9-11. Views of a plesiotype from Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant County, USGS

11740, USNM 108824.

12, 13. Views, X2, of a small plesiotype, from the same source, USNM 108824. 

14-17. Views of a small plesiotype, from the same source; 14, 15 side and back ventral views, X2, coated; 16, 17

back ventral and side views, X3, uncoated, to show sutures. USNM 108824. 

18-20. Views, X3, of the smallest plesiotype from the same source; figures 18, 19 coated; figure 20 uncoated, to

show sutures. USNM 108824. 

21-23. Tarrantoceras multicostatum Stephenson, n. sp. (p. 61).

21. Holotype from concretion in field, 2.5 miles north-northeast of Mansfield, Tarrant County. USGS 14583, 

USNM 108844.

22. 23. Views of a paratype, from the same source, USNM 108842.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 274 PLATE 6

BORISSIAKOCERAS, EUOMPHALOCERAS, AND TARRANTOCERAS
PLATE 7

[Figures natural size)

FIGURES 1-9. Euomphaloceras alvaradoense (Moreman) (p. 63).

1. Ventral view representing part of living chamber of a large piesiotype, from Walnut Creek, 4.75 miles eastnortheast of Mansfield, Tarrant County. USGS 14582, USNM 108828.

2. 9. Views of a piesiotype, from concretion in a field, 2.5 miles north-northeast of Alvarado, Johnson County. 

USGS 14583, USNM 108825.

3-5. Side and ventral views (figs. 3, 4), coated, piesiotype, from Walnut Creek, 4.75 miles east-northeast of Mansfield, Tarrant County. USGS 11740, USNM 108822; partial view of opposite flank of same specimen 

(fig. 5), uncoated, to show sutures.

6-8. Side and ventral views (figs. 6, 7), coated, of a piesiotype from the same source, USNM 108822; back ventral 

view of same specimen (fig. 8), uncoated, to show sutures.

U. s. GOVERNMENT PRINTING OFFICE: 1955
GEOLOGICAL SURVEY PROFESSIONAL, PAPER 274 PLATE 7

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