L I B R.AFIY

OF THE

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Publications
of

FIELD MUSEUM OF NATURAL
HISTORY

GEOLOGICAL SERIES
Volume IV

CHICAGO, u. s. A.

1909-1931

PRINTED IN THE UNITED STATES OF AMERICA
BY FIELD MUSEUM PRESS

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CONTENTS

Pages

New Echinoids from the Ripley Group of Mississippi. By

Arthur W. Slocom i . . . 1-16

New or Little Known Titanotheres from the Lower Uintah

Formations. By Elmer S. Riggs 17-41

New Trilobites from the Maquoketa Beds of Fayette

County, Iowa. By Arthur W. Slocom 41-84

On the Head of the Macropetalichthyids. By Erik A: son

Stensio 85-198

Contributions to Paleontology. By Sharat K. Roy . . . 199-220

Occurrence of the Alligatoroid Genus Allognathosuchus in

the Lower Oligocene. By Bryan Patterson .... 221-226

A Silurian Worm and Associated Fauna. By Sharat K.

Roy and Carey Croneis 227-248

A Fossil Turtle from Peru. By Karl P. Schmidt .... 249-254

I I 30 1 76

in

Natural History Survey

r.iHrnrv

LIST OF ILLUSTRATIONS

PLATES

I. Figs. 1-6. Cassidulus intermedins sp. nov.
Figs. 7-9. Cassidulus hemisphericus sp. nov.

II. Hemiaster lacunosus sp. nov.

III. Linthia variabilis sp. nov.

IV. Columnar Sandstone of Lower Metarhinus Zone Ex-

posed in the Canyon of White River.

V. Upper figure. Green Clays Capped by Amynodon
Sandstone.
Lower figure. Fossil-bearing Sandstone, Upper Meta-
rhinus Zone.

VI. Mesatirhinus superior sp. nov.

VII. Metarhinus riparius sp. nov.

VIII. Metarhinus earlei Osborn.

IX. Figs. 1, 2. Dolichorhinus longiceps.
Fig. 3. Metarhinus cristatus sp. nov.

X. Dolichorhinus fluminalis sp. nov.

XL Fig. 1. Metarhinus earlei.

Figs. 2, 3. Rhadinorhinus abbotti.

XII. Sthenodectes incisivum Douglass.

XIII. Isotelus iowensis Owen.

XIV. Figs. 1-4. Bumastus beckeri sp. nov.
Fig. 5. Megalaspis beckeri sp. nov.
Figs. 6-8. Thaleops ovata Conrad.

Figs. 9-15. Nileus vigilans Meek and Worthen.

XV. Bigs. 1-4. Sphaerocoryphe maquoketensis sp. nov.
Figs. 5, 6. Amphilichas rhinoceros sp. nov.
Fig. 7. Amphilichas clermontensis sp. nov.

XVI. Figs. 1-4. Cybeloides iowensis sp. nov.

Figs. 5-7. Encrinurus pernodosus sp. nov.
Figs. 8, 9. Calymene fayettensis sp. nov.

XVII.

XVIII.

XIX-
XXVIII.

XXIX.

XXX.

XXXI.

XXXII.

XXXIII.
XXXIV.

XXXV.

Figs. 1-3. Ceraurus milleranus Miller and Gurley.

Figs. 4, 5. Ceraurus elginensis sp. nov.

Figs. 6-9. Eccoptochile? meekanus S. A. Miller.

Figs. 1-5. Pterygometopus fredricki sp. nov.
Figs. 6-8. Pterygometopus larrabeei sp. nov.
Fig. 9. Calymene gracilis sp. nov.

-XXVII. Macropetalichthys rapheidolabis.

Figs. 1, 2. Epipetalichthys wildungensis.
Figs. 3-5. Macropetalichthys rapheidolabis.

Macropetalichthys agassizi?
Epipetalichthys wildungensis.

Epipetalichthys wildungensis.
Macropetalichthys rapheidolabis.

Macropetalichthys rapheidolabis.
Epipetalichthys wildungensis.

Favosites limitaris Rominger.
Eucalyptocrinus bordeni sp. nov.

XXXVI.
XXXVII.

XXXVIII.

XXXIX.

XL.

Figs. 1, 2.
Figs. 3, 4.

Fig. 1.
Fig. 2.

Fig. 1.
Fig. 2.

Figs. 1-4.
Figs. 5, 6.

Figs. 7, 8. Palaeoneilo fieldi sp. nov.

Ancyrocrinus bulbosus Hall.

Figs. 1, 2. Poteriocrinus robbi sp. nov.
Figs. 3, 4. Megalomus canadensis Hall.

Figs. 1, 2. Myalina sappenfieldi sp. nov.
Fig. 3. Hyolithes welleri sp. nov.
Fig. 4. Wanneria walcottanus (Wanner).
Fig. 5. Cryptonymus variolaris (Brong.).
Figs. 6, 7. Niobe? huberi sp. nov.

Nawnites gilboensis gen. et sp. nov.

Figs. 1-5. Cryphaeus australis Clarke.
Figs. 6, 7. Cryphaeus nicholsi sp. nov.

Figs. 1-5. Phacopina devonica (Ulrich).
Figs. 6, 8. Calmonia? sp.
Fig. 7. Platyceras daviesi sp. nov.
Figs. 9, 10. Phacops salteri Kozlowski.

Figs. 1-3. Oracanthus vetustus Leidy (described

Newberry).
Figs. 4, 5. Oracanthus vetustus Leidy (described

Leidy).
Fig. 6. Gyracanthides murrayi A. S. Woodward.

Figs. 1-4. Oracanthus farringtoni sp. nov.
Fig. 5. Oracanthus vetustus Leidy.

by
by

VI

XLI. Left Mandible of Allognathosuchus riggsi.

XLII. Fig. 1. Sa = Shale Containing Lecthaylus gregarius and
Associated Fauna. Sb = Shale Containing Only Mono-
graptus vomerinus.
Fig. 2. Photograph Showing Interstratification of
Shale and Dolomite.

XLIII. Lecthaylus gregarius Weller.

XLIV. Figs. 1-3. Lecthaylus gregarius Weller.
Fig. 4. Protoscolex ruedemanni sp. nov.
Figs. 5, 6. Incertae sedis.
Fig. 7. Orbiculoidea sp.

XLV. Fig. 1. Dictyonema retiforme (Hall).

Fig. 2. Dictyonema crassibasale Gurley.
Figs. 3, 4, 6, 8. Desmograptus micronematodes

(Spencer).
Fig. 5. Dictyonema teneUum Spencer.
Fig. 7. Palaeodictyota bella (Hall and Whitfield).
Figs. 9-14. Monograptus vomerinus (Nicholson).

XLVI. Plastral Aspect of Podocnemis olssoni sp. nov.

XLVII. Carapacial Aspect of Podocnemis olssoni sp. nov.

No. 1

Fig. 1.
Fig. 2.

No. 2

Fig. 1.
Fig. 2.

No. 3

Fig. 1.

No. 4

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

Fig. 8.

Fig. 9.

TEXT FIGURES

Page

Diagram of Linthia variabilis 2

Diagram of the Floscelle of Cassidulus intermedins . 3

Section of Metarhinus Beds, as Exposed in the North

Wall of White River 20

Panoramic Section of the Amynodon Beds, from

Kennedy's Basin to White River Canyon .... 21

Diagrammatic Figure of a Trilobite 44

Macropetalichthys rapheidolabis 94

Macropetalichthys rapheidolabis 97

Macropetalichthys rapheidolabis 101

Macropetalichthys rapheidolabis 104

Macropetalichthys rapheidolabis 110

Macropetalichthys rapheidolabis Ill

Macropetalichthys rapheidolabis 117

Macropetalichthys rapheidolabis 128

Macropetalichthys rapheidolabis 133

vii

Fig. 10. Macropetalichthys rapheidolabis 136

Fig. 11. Macropetalichthys rapheidolabis 139

Fig. 12. Macropetalichthys rapheidolabis 141

Fig. 13. Macropetalichthys rapheidolabis 142

Fig. 14. Titanichthys agassizi Newb 143

Fig. 15. Macropetalichthys rapheidolabis 144

Fig. 16. Macropetalichthys agassizi? 151

Fig. 17. Epipetalichthys wildungensis Jaekel 154

Fig. 18. Epipetalichthys wildungensis 155

Fig. 19. Epipetalichthys wildungensis 158

Fig. 20. Phlyctenaspis acadica 165

Fig. 21. Phlyctenaspis acadica 166

Fig. 22. Sketch of a Sensory Canal Groove of a Phlyctenaspid

in Transversal Section. Magnified 168

Fig. 23. Restoration of the Outlines of the Primordial Neuro-

cranium. A, of Coccosteus; B, of Dinichthys . . . 171

Fig. 24a. Dermal cranial roof of Coccosteus decipiens .... 174

Fig. 24b. Dermal cranial roof of Dinichthys halmodeus . . . 175

Fig. 25. Coccosteus decipiens 178

Fig. 26. Jagorina pandora Jaekel 183

V1U

Field Museum of Natural History.
Publication 134.
Geological Series. Vol. IV, No. 1

NEW ECHINOIDS FROM THE
RIPLEY GROUP OF MISSISSIPPI

By

Arthur Ware Slocom,

Assistant Curator, Section of Invertebrate Paleontology.

Oliver Cummings Farrington,
Curator, Department of Geology.

Chicago, U. S. A.

May 15, 1909.

NEW ECHINOIDS FROM THE RIPLEY GROUP OF MISSISSIPPI.

BY ARTHUR WARE SLOCOM

The specimens upon which this paper is based were collected by
the writer in the spring of 1908, during a trip made to Mississippi for
the purpose of obtaining a representative series of fossils from the
well-known Cretaceous and Tertiary deposits of that state.

The Ripley formation of Mississippi, from which the specimens
here described were obtained, extends southward from Tennessee, on
the border of which state it has a width of about 10 miles. In the
southern part of Tippah County it widens out to about 1 5 miles and
from thence gradually narrows as it passes south through Union
and Pontotoc Counties until near Houston in Chickasaw County it
disappears altogether. For the most part this formation occupies
the highlands and is locally known as the Pontotoc Ridge. Over a
large part of this region the Ripley is overlain by red sands and clay
of the Lafayette and Wilcox groups, so that the Ripley beds are often
found in the gullies and along the streams and are recognized on
account of their light color. They are locally called "white gullies."

At Pontotoc, Mississippi, three localities were visited, viz: (1)
the Patterson farm about three miles southeast of town; (2) the
bluffs on either side of One Mile Run, about a mile south of town on
the Houston road; and (3) the roadside near the southern edge of the
village. These two latter outcrops are similar in position, compara-
tively near together and will be considered in this paper as one locality.
The outcrop on the Patterson farm lies somewhat higher than the
other two and is probably higher geologically. At all these localities
well preserved echinoids were found. About 200 specimens were
collected which proved, on examination, to represent six species,
four of which are new and are here described.

CLASSIFICATION AND TERMINOLOGY.

The classification here used is that prepared by P. M. Duncan,*
and given in the English edition of Zittel's Text Book of Paleontology.

* P. M. Duncan 1889, Revision of the Genera and Great Groups of the
Echinoidea, Jour. Linnean Soc. Vol. XXIII.

Field Mus. Nat. Hist. Geol. Ser. Vol. IV, No. 1.

2 Field Museum of Natural History — Geology, Vol. IV.

The terminology of Desor* with some modifications is adhered to.
It may be briefly stated as follows :

Echinoids or Sea Urchins: Marine animals without arms or stem,
the bodies encased in a solid or slightly flexible test or shell, varying
in shape from spherical to flat ; composed of numerous closely placed
plates, covered with spines. The mouth is on the ventral or actinal
surface; the anus either in the apical system or somewhere in the
posterior interambulacral area. The plates of the ambulacral areas
are more or less extensively perforated for the protrusion of the am-
bulacra or tube feet.

Dorsal Surface: (Af) The upper, usually convex surface, on
which are situated the apical system, petals, etc.

Ventral or Actinal Surface: (C) The lower surface on which the
peristome is situated.

Anterior Sulcus: (as) A more or less distinct groove in the an-
terior margin of the test. In it is situated the anterior ambulacral
area.

iamb

iamb

Fig. i. Diagram of Linthia variabtlis. A, dorsal view. B, posterior view. C, ventral view.

Ambulacral (amb.) and Interambulacral Areas: (iamb.) The test
of practically all echinoids is divided into ten segments or areas,
five ambulacral and five interambulcral areas. In living echinoids
and most Mesozoic or Cenozoic fossil echinoids, including all species
mentioned in this paper, each area consists of two rows of plates.

Poriferous Zones: On each side of the ambulacral areas are bands
or zones containing openings or pores through which issue the tentacles
or tube feet. There are ten poriferous zones, two to each ambulacral
area. In some echinoids there is quite a space between the poriferous
zones and this space is called the inter poriferous zone.

Simple Ambulacra: Those in which the pores of the poriferous
zones have the same disposition from the apex to the peristome.
This is the case in all "regular echinoids."

* E. Desor 1858. Synopsis des Echinides Fossiles Paris,
t The letters in parentheses refer to those of Figs. 1 and 2.

May, 1909.

New Echinoids — Slocom.

Petaloid Ambulacra: In some genera the ambulacral areas are wide
near the apex and the poriferous zones are bounded by a groove. The
part of the area having this form is called the petal (p). In other
genera the poriferous zones are similar in form to the above, but the
petals are not closed at their distal ends and the zones continue. The
disposition of the pores is, however, radically changed. Areas having
this form are called subpetaloid.

Apical System (a) : A disc ordinarily composed of ten plates, (PI. II
fig. 5) five of which called genital plates form the summits of the inter-
ambulacral areas and five called radial plates, by some authors oculars,
form the summits of the ambulacral areas. Two or more of the
genital plates may be fused, thus reducing the number. One of the
genital plates is usually larger than the others and bears a spongy
protuberance filled with minute pores called the madreporite.

b *~ pk

Fig. 2. Diagram of the floscelle of Cassidulus intermedins.

Floscelle: (Fig. 2) In the family Cassidulidae the ambulacral areas
assume a peculiar flowerlike form around the peristome, called the
floscelle. The floscelle is composed of five enlargements of the pori-
ferous zones called the phyllodes (ph). These five phyllodes are
separated from each other by five inflated plates of the interambulacral
areas about the peristomal margin. These inflated plates are called
bourrelets (b).

Fascioles: Narrow bands apparently smooth but in reality formed
of microscopic tubercles, which during life bear vibrating cilia. They
have been divided into: (1) the peripetalous fasciole (pf) which sur-
rounds the petals; (2) the marginal fasciole which follows the sides;
(3) the subanal fasciole which is limited to the posterior face; and (4)

4 Field Museum of Natural History — Geology, Vol. IV.

the lateral fasciole (If) which branches from the peripetalous fasciole
and passes beneath the periproct.

Tubercles: (PL II figs. 8,9.) Wart-like protuberances which occur on
the plates of most echinoids. They vary in size from quite large to
microscopic granulations. Tubercles consist of two parts, the boss
and the mamelon. The base or boss may be either plain or crenulated.
The mamelon is a small rounded protuberance above the boss to which
in life, a spine is attached. A plain or sunken space surrounding the
boss generally marked by a ring of granules is called the areole or
scrobicule.

Periproct (pt) : The upper or posterior opening in the shell, im-
properly called the anus, but which contains the latter. The periproct
is closed by a membrane to which the anal plates are attached. These
plates may be few and symmetrical, or numerous and irregular, and
arranged concentrically about the anal opening. The position of
the periproct is within the apical system in "regular echinoids" but
in "irregular echinoids" it is situated somewhere in the posterior
interambulacral area. It may be either on the dorsal or ventral
surface. The position of the periproct is of great systematic impor-
tance.

Peristome (ps) : The lower opening of the shell ; it is situated on
the ventral surface, either at the center or on the median line between
the center and the anterior margin. In form it may be decagonal,
pentagonal, oval, bilabiate, etc. It contains the buccal membrane
in the center of which the mouth is situated.

Labrum: (1) The posterior lip of the peristome.

Proximal: Nearest to the apex.

Distal: Farthest from the apex.

Lateral: Pertaining to the side.

May, 1909. New Echinoids — Slocom. 5

DESCRIPTION OF GENERA AND SPECIES.

Order SPATANGOIDA.

Family CASSIDULIDiE.

Genus CASSIDULUS Lamarck 1801.

Test small, oblong, depressed, broadest posteriorly, longer than
broad, broader than high, convex dorsally, flat or concave ven-
trally.

Apical system eccentric in front or subcentral; four perforated
genital plates; the madreporite passing back and separating the
postero-lateral genitals but not the radial plates. Ambulacral areas
subsimilar, short, flush, subpetaloid, not closing; pores continued
from the petaloid part to the floscelle, which is well developed. Ten-
tacles both simple and branchial (heteropodous) . Peristome eccentric
in front, the bourrelets narrow and strong, the phyllodes in grooves,
One peristomal plate to each interradium. Usually a median band
behind the peristome where there are no tubercles and where the test
is either cribriform, pitted or plain, or it may be absent. Periproct
supramarginal, in a depression or at the commencement of a groove,
elongated longitudinally. Tubercles small and very close together
on the dorsal surface, large and separated on the ventral, except on
the longitudinal median area.

Range Cretaceous and Eocene.

Cassidulus Subquadratus Conrad.

i860. C. subquadratus Conrad, Jour. Acad. Nat. Sci. Phil., 2nd ser.

Vol. 4, p. 291, pi. 47, fig. 19.
1 89 1 C. subquadratus Clark, Johns Hopkins Univ. Circ. No. 87,

p. 76.
1893 C- subquadratus Clark, Bull. U. S. G. S. No. 97, p. 70, pi.

31, fig. 1 a-h.
Original description: " Suborbicular, flat beneath, flexuous pos-
teriorly; lateral and end slopes truncated; anus very large, obtusely
ovate, with a depression beneath, extending to the margin, which at
that point is salient; ambulacra lanceolate.

Length 3^ inches; Diameter 2% inches; Height 1% inches.
Locality. Tippah county, Mississippi." Clark gives Holly
Springs as the locality of this species.

6 Field Museum of Natural History — Geology, Vol. IV.

No entire specimens of this species were collected by the writer,
but six fragments, Cat. No. P 10345, of sufficient size for identification
were found on the Patterson farm near Pontotoc, Mississippi.

Cassidulus intermedius sp. nov. Plate I, Figs. 1-6.

' Test oval, greatest width posterior to the center; rounded anter-
iorly, slightly rostrated posteriorly; dorsal surface convex, apex
eccentric anteriorly and inflated, sides declining about equally towards
the margins which are slightly inflated; the peristomal concavity
occupying more than half of the ventral surface. Ambulacral areas
narrow and flush, poriferous zones subpetaloid on the upper part of
the dorsal surface to a point varying in the different areas from about
one third to nearly one half the distance from the margin to the apical
system ; the zones are then contracted and continue as narrow bands
over the margin to the vicinity of the peristome, where they abruptly
widen, and again narrow to the peristome forming a floscelle. The
pores are distant and paired on the petaloid portion and in the flos-
celle; on the narrow connecting portions they are single, small and
indistinct. In the petaloid areas the pores of the outer rows are slit-
like, those of the inner rows round and smaller ; each pair is connected
by a groove. Interambulacral areas composed of large plates, the
plates nearest the peristome in each area inflated forming the bour-
relets. Dorsal surface covered with small crowded tubercles with
slightly sunken areoles, the tubercles on the ventral surface rapidly
increasing in size and distance apart as they approach the peristome.
A wide, longitudinal median band extends from near the anterior
margin through the floscelle to the posterior margin. This band is
without tubercles and the surface is smooth except where it passes
through the floscelle. The apical system in the type specimen is too
incomplete for detailed description, but appears similar to other species
of this genus. The peristome is situated slightly in front of the center
of the ventral surface, pentagonal, surrounded by a well-marked
floscelle, the bourrelets large and prominent, the phyllodes very
narrow as they reach the peristome and situated in grooves. The
periproct is elongated longitudinally and situated on the dorsal sur-
face at about one third the distance from the posterior margin to the
apex in a deep groove. The dimensions of the type specimen are:
Length 25.6 mm., width 22.7 mm., height 9.6 mm.

This description is based on a single specimen, Cat. No. P 10346,
collected by the writer. The specimen had been slightly crushed on
the left side, a few of the plates of the left interambulacral area and
part of the apical system are missing, but the general form and all

May, 1909. New Echinoids — Slocom. 7

other parts of the test are complete. In general form this species
resembles C. cequoreus, but it is not so high in proportion to its length,
the periproct is somewhat higher, the pores in the outer rows
of the petaloid portions are slitlike instead of round and the
expansions of the phyllodes are wider. C. intermedins resembles
C. micrococcus in the slitlike pores of the outer rows of the petaloid
areas and in the expansion of the phyllodes, but the position of the
pores in these expansions is more like those of C. cequoreus. The
position of the periproct is midway between that of C. micrococcus
and C. cequoreus, the size and shape of the test is quite unlike C.
micrococcus and the extension of the longitudinal median band in
front of the peristome on the ventral surface does not appear, from
the description and figures, to occur in either of the other species.
The name adopted for this species refers to the characters inter-
mediate between C. cequoreus and C. micrococcus which the species
exhibits.

Locality: Ripley Group near the southern edge of the village of
Pontotoc, Mississippi.

Cassidulus hemisphericus sp. nov. Plate I, Figs. 7-9.

Test subhemispherical with its transverse diameter somewhat
shorter than the longitudinal, sides arcuate, margins angular, ventral
surface flat or nearly so. Ambulacral areas wide, subpetaloid on the
top of the dorsal surface, not closed distally, petals subequal in
length, extending about half way from the apex to the margin,
slightly convex; from the distal end of the petals the ambulacral
areas are continued as a band which gradually increases in width
from the petal to the margin, most of the way being wider than the
petal. On the ventral surface the bands slightly narrow to the
floscelle. The floscelle is not well preserved in the type specimen, but
enough is preserved to determine that the bourrelets are prominent
and that the phyllodes are in grooves. The apical system is central
but the form of the various plates of which it is composed cannot be
determined. The interambulacral areas are about equal in size.
They form an acute angle near the apex and rapidly expand to the
margin, the plates being comparatively large. All the plates of the
dorsal surface, with the exception of those of the petals, are marked
by prominent lines subparallel to the edge of the plates. These lines
are farther apart on the lateral edges than on the proximal and distal
edges. They appear to be lines of growth. The middle portion of
the plates within this series of lines is inflated, so that in the small
plates of the interambulacral areas, near the apex, the centers of

8 Field Museum of Natural History — Geology, Vol. IV.

the plates appear as prominent nodes. These middle portions of the
plates are free from tubercles, but the parts of the plates covered by
the parallel lines and the plates of the petals are covered with minute
tubercles closely crowded together. The lines are much less prom-
inent on the plates of the ventral surface and the tubercles are larger,
with slightly sunken areoles and more evenly distributed over the
surface except on the longitudinal median band, which extends from
the peristome to the posterior margin. The peristome is situated at
the center of the ventral surface, surrounded by a floscelle, the bourre-
lets are prominent and the phyllodes are depressed and contracted
into narrow grooves, where they reach the peristome. The periproct
is supramarginal, but its form and exact position are unknown because
that portion of the posterior interambulacral area near the margin
is missing. The measurements of the type specimen, Cat. No. P
10347, are: Length 34.7 mm. width 26:7 mm., height 19.5 mm.
Allowing for the lateral crushing it is probable that the length and
width were originally about 32 mm. and 29 mm. respectively.

It is to be regretted that other and more perfect specimens
of this species could not have been found and the writer has endeav-
ored to obtain such specimens by correspondence, but so far without
success. The specimen on which the description is based is crushed
laterally, and in three of the interambulacral areas and the region
about the peristome there are some plates missing. Three of the
ambulacral and two of the interambulacral areas are practically
complete. The entire petaloid portion of the dorsal surface is in good
condition, so that the only important character that is in doubt is the
exact form and position of the periproct. The five pairs of plates
above the margin in the posterior interambulacral area are missing
and the periproct was situated somewhere within this space. The
specific name is adopted on account of the hemispherical form of
the test, which distinguishes it to a marked degree from any other
species of the genus.

Locality : The type specimen was collected by the writer in the
"white gullies" of the Ripley Group on the Patterson farm, about
three miles south of Pontotoc, Mississippi.

May, 1909. New Echinoids — Slocom. 9

Family SPATANGID^).
Genus HEMIASTER Desor 1847.

Urchins with a short, elevated, oval or cordiform test. Apical
system in general excentral and posterior. Ambulacral areas peta-
loid, unequal in length, and lodged in depressions of the dorsal surface;
poriferous zones large and equal in the same ambulacral area, pores
elongated and placed close together. Anterior area lodged in a long
shallow sulcus; poriferous zones very narrow and composed of small
round pores sparsely disposed in oblique, widely separate, simple
pairs. Fasciole single, peripetalous, and circumscribing the ambul-
acral areas. Apical disc small and compact, four perforated genital
plates, and five very small radial plates. Peristome bilabiate,
very excentral, opening at the anterior fourth part of the base. Peri-
proct opening high up on the posterior border, which is in general
flat, and obliquely truncated.

Hemiaster differs from Micraster in having a single peripetalous
fasciole and no anal fasciole; the test is likewise in general shorter,
more inflated, and the posterior pair of ambulacral areas are much
shorter than the anterior pair. Hemiaster differs from Linthia in
having only a peripetalous fasciole, the latter having both peripetalous
and lateral fascioles.

Range Cretaceous to Recent.

Hemiaster parastatus (Morton).

1830. Spatangus sp. Mort., Am. Jour. Sci., 1st ser., Vol. 17, p. 286.
1830. S. cor-marinum (?) Mort., Am. Jour. Sci., 1st ser., Vol. 18,

p. 250, pi. 3, fig. 10.
1830. 5. cor-marinum (?) Mort., Jour, Acad. Nat. Sci. Phil., 1st

ser., Vol. 6, p. 199.

1833. S. parastatus Mort., Am. Jour. Sci., 1st ser., Vol. 23, p. 294.

1834. 5. parastatus Mort,. Synop. Org. Rem. Cret. Gr. U. S., p. 77,
pi. 3, fig. 21.

1853. Hemiaster parastatus Marcou, Explan. Text to Geol. Map.

U. S., and Brit. Prov. N. A., p. 47, pi. 7, fig. 8.
1855. H. parastatus d'Orb., Pal. France, Terr. Cret., Vol. 6, p. 265,

pi. 894, fig. 4.
1864. H. (?) parastatus Meek, Check List Inv. Foss. N. A., Cret.

and Jur., p. 3.
1891. H. parastatus Clark, Johns Hopkins Univ. Circ, Vol. 10,

No. 87, p. 77.

io Field Museum of Natural History — Geology, Vol. IV.

1893. H. parastatus Clark, Johns Hopkins Univ. Circ, Vol. 12,

No. 103, p. 52.
1893. H. parastatus Clark, Bull. U. S. G. S., No. 97, p, 83, pi. 45,

figs. 1 a-m.
1905. H. parastatus Johns., Proc. Acad. Nat. Sci. Phil., 1905,

p. 7.
1907. H. parastatus Weller, Paleontology of New Jersey, Vol. 4,

p. 298, pi. 15, figs. 1-13.
This species was described from the Upper Cretaceous limestone
of Timber Creek, New Jersey, and has been reported from the Ripley
Group of Alabama.

Five specimens of this species, Cat. No. P 10341, were collected
by the writer near the southern edge of the village of Pontotoc,
Mississippi, in the so-called "white gullies" of the Ripley Group.

Hemiaster lacunosus sp. nov. Plate II, Figs. 1-7.

Test small, indistinctly cordate, ventral surface moderately con-
vex, dorsal surface convex, strongly elevated in the posterior inter-
ambulacral area and gradually sloping with an indistinct anterior
sulcus; anterior and lateral borders inflated, posterior margin trun-
cated. Ambulacral areas petaloid, with straight petals situated in
depressions of the surface, the antero-lateral pair nearly twice as
long as the postero-lateral pair; poriferous zones of the paired
petals wide, pores transversely elongate and situated far apart.
Anterior petal longer but narrower than the others and situated in a
deep depression which grades into an indistinct anterior sulcus;
poriferous zones of this petal narrow and far apart; pores small,
round and separated by a tubercle. Interambulacral areas broad
and composed of large plates. Surface of the test covered with a
multitude of small tubercles with sunken areoles that increase in
size toward the peristome. The tubercles have perforated mamelons
and crenulated bosses, the inter-spaces being filled with microscopic
granulations. Peripetalous fasciole wide and distinct, moderately
bent inward between the petaloid areas except the two posterior
ones. Apical disc sunken, small and situated somewhat posterior
to the center of the dorsal surface, the four genital plates distinctly
perforated and separated by five small radial plates. Right anter-
ior genital plate large, convex and forming the madreporite.
Peristome transversely arched, bilabiate, with prominent labrum.
Periproct about the size of the peristome, elongated vertically
and situated near the top of the posterior truncation.

May, 1909.

New Echinoids — Slocom.

11

The dimensions of a number of practical^ perfect specimens are
as follows:

Cat. Xo.
P 10342

Length

Width

Height

mm

mm

mm

A

23-4

23.6

15 3

B

23-3

21.7

i7-

C

22.5

21 . 1

16.5

D

20.5

20 .

151

E

17.8

16.3

11. 8

H. lacunosus resembles H. parastatus in general form and pro-
portions, but is distinguished from that species by its smaller size
and by the sunken areoles of the tubercles. Moreover, the posterior
interambulacral area is rounded, while in H. parastatus it is in the
form of a ridge. H. lacunosus is similar to H. Stella in size, but differs
from it in the shape of the fasciole, the sunken areoles and the form
of the anterior margin. It resembles H. dalli in having sunken areoles,
but in general form these two species are quite dissimilar. The
specific name adopted refers to the sunken areoles by which the species
is distinguished.

Locality: This species is abundant at all three of the outcrops
visited at Pontotoc and about 150 specimens were collected. The
test is very thin and and fragile, so that of the 150 specimens less
than a dozen were unbroken. Three specimens which undoubtedly
belong to this species were also collected by the writer at Houston,
Mississippi, associated with fossils of the Selma Chalk, but as the Rip-
ley and Selma formations are both reported from Houston and the
fossils were found at the bottom of gullies of some size, it is quite
probable that the echinoids were of Ripley age. ,

Genus LINTHIA Merian 1853.

Test variable in size, oval or cordiform, grooved anteriorly,
subacuminate or truncated posteriorly, tumid and gibbous dorsally,
almost flat ventrally. Apical system small, eccentric anteriorly,
composed of four perforated genital plates, one of which forms the
madreporite, and five small radial plates. Ambulacral areas diverse;
anterior one in a broad groove, pores round and small. Antero-
lateral pair with petaloid parts in grooves, moderately long, diver-
gent, nearly closing distally; pairs of pores equal or subequal. Pos-
tero-lateral pair also in sunken grooves, less divergent and shorter

12 Field Museum of Natural History — Geology, Vol. IV.

than the others. Ambulacra form the greater part of the peristomal
margins, and are moderately broad on either side of the sternum.
Peristome eccentric in front, semilunar, with a well-developed pos-
terior labrum. Periproct at the upper part of the posterior truncation.
A peripetalous fasciole, and a lateral fasciole starts from the peri-
petalous fasciole close to the antero-lateral petals and passes beneath
the periproct. Tubercles crowded, increasing in size as they approach
the peristome, usually crenulate and perforate, and either on flat or
in sunken areoles.

Range Cretaceous to Recent.

Linthia variabilis sp. nov. Plate III, Figs. i-ii.

Test distinctly cordate, truncated posteriorly, ventral surface
depressed convex, dorsal surface elevated, forming a sharp ridge in
the posterior interambulacral area. Sides inflated and sloping to the
lateral and anterior margins; posterior truncation slightly concave
and the angle between the truncation and the base line varying from
77° to 900. Ambulacral areas straight, petaloid, situated in compara-
tively deep depressions of the dorsal surface. Antero-lateral pair
about one and one-half times the length of the postero-lateral pair,
poriferous zones of these four petals wide, pores elongated and slit-
like. Each pair of pores connected by a shallow groove and the pore
near the border of the petal the larger. Unpaired anterior ambulacral
area situated in a deep depression the continuance of which forms a
sulcus in the anterior margin. Poriferous zones of this area narrow
and situated far apart. Pores round and each pair separated by a
tubercle. Interambulacral areas broad and composed of large plates.
Surface of the test covered with minute perforated tubercles having
crenulated bosses. These tubercles increase in size as they approach
the peristome. Interspaces filled with small tubercles and microscopic
granulations. Both peripetalous and lateral fascioles are clearly
defined, peripetalous fasciole decidedly bent inward between the
antero-lateral and postero-lateral petals and somewhat less so between
the other petals. Apical system situated in the center or somewhat
anterior to the center of the dorsal surface; small, depressed, having
the four genital plates perforated and separated by five small radials.
Peristome transversely elliptical, situated near the anterior margin.
Labrum prominent. Periproct somewhat elongated vertically and
situated near the top of the posterior truncation.

May, 1909.

New Echinoids — Slocom.

13

The dimensions of a number of practically perfect specimens are
as follows:

Cat. No.

Length

Width

Height

Height of
Periproct

Posterior
Angle

Position
of Apex

P 10457

mm

mm

mm

mm

A

24 . 2

23.1

IS-

6 5 .

75°

Anterior

B

23-5

22.8

13 -5

5

1

75°

Anterior

D*

29.7

29 . 1

*5 ?

6

6

75°

Central

E

25-

24.7

15-3

6

9

74°

Anterior

F

25-

23-5

15 ■ 7

6

7

82°

Anterior

G

23-9

24 .6

18.2

7

5

85°

Subcentral

H

21 .

19.7

15-

8

5

79°

Subcentral

J

20.

20 .

13.6

6

3

85°

Central

Kt

31.6

26.4?

23 -7?

9

5

87°

Anterior

P 10458

L

26.6

26 .4

19 .6

9

8

85°

Central

M

24.9

25-7

17.7

8

2

84°

Central

N

23.8

23-7

*7-5

8

850

Subcentral

O

21.7

21.8

15.6

8

5

85°

Subcentral

P

26 . 1

24 -5

16.3

7

8

90°

Central

S

24.8

25-3

14 -5

6

6

84°

Anterior

T

251

23.6

16 .4

7

5

77°

Anterior

U

24 . 2

24.1

16 . 2

7

4

77°

Anterior

V

27-3

26.3

15-4

6

7

73°

Subcentral

w

18.7

l7 ■

. 10.8

5

1

83°

Central

X

17. 1

16.6

10 . 1

4

8

77°

Central

This table shows that this species exhibits great individual vari-
ation in a number of characters. Thus the proportion of length to
width varies from wider than long to longer than wide ; the proportion
of height to length is variable; the height of the periproct varies in
proportion to the height of the test; the basal line and the posterior
truncation form an angle varying from 730 to 900 and the position of
the apical disc varies from central through subcentral to decidedly
anterior. The manner in which these variations are combined is
so diverse, however, that no well-marked divisions can be made.
Taking two extremes of form such as B and L we find B longer than
wide, test low, periproct low, posterior angle 750, apex anterior; in
L the length and width are about equal, test high, periproct high,
posterior angle 850, apex central. This combination of characters
would seem to be of specific importance, but S is wider than long,
test high, periproct low, posterior angle 840, apex anterior; F longer
than wide, test high, periproct low, posterior angle 820, apex anterior;
X longer than wide, test low, periproct low, angle 770, apex central.
Hence it is evident that these variations are not constant but in-

* Crushed vertically,
t Crushed laterally.

14 Field Museum of Natural History — Geology, Vol. IV.

dividual variations. Owing to this tendency to variation, the spe-
-cific name variabilis has been adopted.

Only one other species of this genus, L. tumidulus, has hitherto
been described from the American Cretaceous and that species is so
unlike L. variabilis that a detailed comparison is unnecessary.

Locality: This species is from the Ripley Group and is quite
abundant both on the bluffs at One Mile Run and near the southern
•edge of the village at Pontotoc, Mississippi. Two casts which evi-
dently belong to this species were also collected by the writer in the
Owl Creek marls in Tippah County, Mississippi.

A careful examination of the literature reveals the fact that com-
paratively little attention has hitherto been paid to the echinoids
of the Ripley Group of Mississippi. The following are all the references
that have been found by the writer:

Journal of the Academy of Natural Sciences Philadelphia, 2d
series, Vol. 4, p. 291. i860. T. A. Conrad describes Cassidulus
■abruptus and C. subquadratus both from Tippah County, Mississippi.

Report of the Geology and Agriculture of the State of Mississippi,
i860, p. 92. E. W. Hilgard, State Geologist, gives a list of fossils
'collected from the strata of the Ripley Group in Tippah, Pontotoc
and Chickasaw Counties, in which the following echinoids are
listed :

Hemiaster, 2 species.

Cassidulus subquadratus Conrad.

Cassidulus? (Echinanthus?) sp.

Cassidulus shape of Faujasia apicalis.

The Echinodermata of the United States, W. B. Clark, Bull.
U. S. G. S. Vol. 97, 1893. The following echinoids are noted from
the Ripley Group:

Botriopygus alabamensis Clark Alabama.

Cassidulus cequoreus Morton Alabama.

Cassidulus micrococcus Gabb Eufaula, Alabama.

Cassidulus porrectus Clark Eufaula, Alabama.

Cassidulus subconicus Clark Mississippi.

Cassidulus subquadratus Conrad Holly Springs, Mississippi.

Hemiaster parastatus Morton Alabama.

Cassidulus abruptus Conrad is mentioned as a doubtful species.

Geology and Mineral Resources of Mississippi, A. F. Crider. Bull.
U. S. G. S. Vol. 283, 1906, p. 20. A list of the Ripley fauna at Owl
Creek, Tippah County, Mississippi, as collected by Dr. T. W. Stanton
is given in which Cassidulus subconicus and C. subquadratus are
mentioned.

May, 1909. New Echinoids — Slocom. 15

The following list shows the echinoids and associated fossils
collected by the writer on the Patterson Farm, Pontotoc, Mississippi.

ECHINOIDS

Cassidulus subquadratus Conrad.
Cassidulus hemisphericus Slocom.
Hemiaster lacunosus Slocom.

BRYOZOANS

A few unidentified specimens.

PELECYPODS

Anomia argentaria Morton.
Cucullcea sp.
Exogyra costata Say.
Exogyra interrupta Conrad.
Gryphceostrcea vomer Morton
Ostrcea denticulifera Conrad.
Ostrcea tecticosta Gabb.
Ostrcea, two unidentified species.
Pecten sp.

GASTROPODS

Turritella tippana Conrad.
Several unidentified natural casts.

CEPAHLOPODS

Baculites.

CRUSTACEA

Thorax of a crab, unidentified.

VERTEBRATES

Shark teeth and vertebrae.

The following were collected near One Mile Run and in the south-
ern part of the town of Pontotoc:

ECHINOIDS

Cassidulus intermedins Slocom.
Hemiaster parastatus Morton.
Hemiaster lacutwsus Slocom.
Linthia variabilis Slocom.

16 Field Museum of Natural History — Geology, Vol. IV.

PELECYPODS

Exogyra costata Say.
Gryphceostrcea vomer Morton.
Ostraa denticulifera Conrad.

ACKNOWLEDGMENTS

The publications of P. M. Duncan and E. Desor have been freely
drawn upon for the generic descriptions here used, but as they have
been rearranged and adapted more or less they have not been treated
as quotations.

President John GofE of the Chickasaw Female College, Pontotoc,
Mississippi, gave the writer valuable information as to localities in
the field and also later furnished specimens which materially aided
in the preparation of this paper.

Explanation of Plate I

Cassidulus intermedius sp. nov., page 6.

Figs. 1-4. Dorsal, ventral, posterior and lateral views of the type specimen.
Xi.

Fig. 5. Portion of the left posterior ambulacral area at base of the petaloid
region, greatly enlarged.

Fig. 6. Right posterior phyllode with the adjoining bourrelets, greatly
enlarged.

Cassidulus hemisphericus sp. nov., page 7.

Figs. 7, 8. Dorsal and lateral views of the type specimen. Xi.

Fig. 9. Portion of the anterior ambulacral area at the base of the petaloid
region, greatly enlarged.

FIELD MUSEUM OF NATURAL HISTORY.

GEOLOGY, VOL. IV, PL. I.

Explanation of Plate II

Hemiaster lacunosus sp. nov., page 10.

Figs. 1-4. Dorsal, ventral, posterior and lateral views of B, one of the
type specimens. Xi.

Fig. 5. Apical system greatly enlarged, g. genital plates, m. madreporite.
r. radial plates.

Fig. 6. Portion of the anterior petal where it joins the apical system,
greatly enlarged.

Fig. 7. Several plates of the right anterior petal, greatly enlarged.

Figs. 8, 9. Top and side views of a tubercle, greatly enlarged.

FIELD MUSEUM OF NATURAL HISTORY.

GEOLOGY, VOL. IV, PL. II.

LIBKmKY

UmVERSIIY Oh iLLiiMUib

URBANA

Explanation of Plate III

Linthia variabilis sp. nov., page 12.

Figs. 1-4 Dorsal, ventral, posterior and lateral views of Cat. No. P 10457 B.
Xi.

Figs. 5-8. Dorsal, ventral, posterior and lateral views of Cat. No. P 10458 L.
Xi.

Fig. 9. Apical system, greatly enlarged.

Fig. 10. Several plates of the left posterior petal, greatly enlarged.

Fig. 11. Several plates of the anterior petal, greatly enlarged.

FIELD MUSEUM OF NATURAL HISTORY.

GEOLOGY. VOL. IV, PL. III.

10

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