(SMogial 3mk^ of \k Statt ai |[eto |orli.

PALAEONTOLOGY:

Vol. V. Part I.

LAMELLIBRANCHIATA

L_

CONTAINING DESCRIPTIONS AND FIGURES

OF THE
OF THE

UPPER HELDERBERG, HAMILTON AND CHEMUNG GROUPS.

By JAMES HALL,

STATE GEOLOGIST.

ALBANY, N. Y.:

CHARLES VAN BENTHUYSEN & SONS.
1884.

(05

5

State op New York, 1

Albany, February 15, 1884. )

Published under the auperviaion of the 'IVuatees of the State Museum of Natural History, pursuant to

chai)ter 355 of the Laws of 1883.

,1

, 1

DEDICATION

To His Excellency

G ROVER CLEVELAND,

Governor of the State of New York :

Sir — I have the honor to present to your Excellency a new volume of the
Natural History of the State of New York, forming a continuation of the work
on tlie Palaeontology of the State.

This volume, together with another to be published early next year, is
devoted to the description and illustration of the fossil bivalve shells known
as Lamellibranchiata. The entire work will embrace all the fossils of this
class from the higher geological formations of the State. The material has been
accumulated from various sources during the period since 1843. Eighty plates
for these volumes had already been lithographed in 1873, but the publication
was delayed for want of legislative authority for the printing. During the
session of 1883 an act was passed by the Legislature, and sanctioned by your
Excellency, providing for the completion of the entire work upon the PaljEon-
tology of the State. The present volume is the first fruit of that act, and I
trust its publication may give you personal satisfaction.

Hoping that this volume may commend itself to the students of science and
prove not unworthy of the great series of works comprised in the Natural
History of the State of New York,

I have the honor to be,

With great respect.

Your obedient servant,

JAMES HALL,

State Geolof^ist.

Albany, February 15, 1884.

"tD"

TABLE OF CONTENTS.

Page.

DEDICATION iii

TABLE OF CONTENTS v

ADDENDA AND CORRIGENDA vi

PREFACE vii-x

SYNOPSIS OF THE GENERA •. . xi-xiv

INDEX . xv-xviii

DESCRIPTIONS OF SPECIES 1-268

aviculopecten ............ 1-40

Lyriopecten ............. 40-57

Pterinopecten 57-81

Ckenipecten 81-90

Pterinea 91-103

S. G. Vertdmnia 104-107

actinopteria ............. 107-128

Pttchopteria 129-152

Glyptodesma ............. 153-157

Leiopteria ............. 158-174

Leptodesma ............. 175-236

Pteronites 237-239

Paljjopinna 240-241

Ectenodesma 242-243

Limoptera ..........■■■ 243-251

Byssopteria ' 252

Mytilarca 253-264

S. G. Plethomytilus 253-256

GOSSELETTIA 265-266

MoDiOLA, S. G. Mytilops 267-268

PLATES AND EXPLANATIONS i-xxxiii and lxxxi-xcii

ADDENDA AND CORRIGENDA.

Pag-e 14, iidd lo reference of A. laitcs, plate 81, tig-. 5.

Page 30, for A. cloiif/atus read A. celsm.

Page 54, add to reference of L. priamcs, plate 82, tig. 6.

Page 74, line 2, for LXXXI read LXXXU.

Page 82, line 3, for P. crenulatits read C. crenulatits.

Page 114, line 23, for rectirulata read reticulatn.

Page l.")7, line 11, for anterior read posterior.

Page 1G7, for A. Bigshiji read L. Big.ibyi.

Page 220, line 8, for N. Y. read Pa.

Pages 18G ami 23S, lines 4 and 7, respectively, for Alleghany read Cattai-augus.

The names Philipsbiirgli and Rockville, are localities referred to in the earlier Geological Reports,
from which many fos.sils were obtained. The former (Philipsburgh) is now known as Belmont. Rockville
was a settlement near the mouth of Rock creek on the Gene.see, in the township of Belfast, during the con-
struction of the Genesee Valley Canal. The name does not now appear in the Gazetteer.

PREFACE

The present volume includes the letter press and plates which constitute a
portion of Volume V, Part 1, of the Palaeontology of New York. It was
originally intended to arrange the whole of this material as a volume of text
and a volume of plates ; but the exigencies of publication have made it necessary
to issue a volume of the work at the present time, and in its present form, leav-
ing the remaining portion to constitute a similar volume which will be published
early in the next year.

The entire woi-k will embrace the descriptions and figures of all the recognized
forms of Lamellibranchiata from the Upper Helderberg, Hamilton, Portage and
Chemung Groups within the limits of the State of New York. This volume
includes descrijitions and figures of the species under the genera included
in the accompanying synopsis, belonging to the families, Pectenida?, Pterinida^,
Aviculidae, Ambonychidse, and Mytilida3.

The fossil Lamellibranchiata of the higher groups of the New York geological
series are often abundant, of great variety of form and of very interesting-
character. Our earlier knowledge of these fossils is almost wholly due to Mr.
Conrad, who described eleven species in the Annual Report of the Geological
Survey in 1838 ; and during the following years this work was continued, both
in the Annual Rei^orts of the Survey and in the Journal and Proceedings of
the Academy of Natural Sciences of Philadelphia. The total number of species
described by Mr. Conrad from all the groups is about one hundred and ten, and
fifty of these have been illustrated in the publications of the Academy. The
number of species at present known from the same formations is about 600, of
which nearly 500 are from the groups above the Oriskany sandstone.

viii PREFACE.

Duriiij^ and since this period the writer has made extensive collections of
these fossils, hoth with his own hands and through the agency of his assistants,
preparatory for their illustration in the Palaeontology of New York. After
having accumulated considerable collections, and feeling the importance of their
proper identification, tlic writer per.sonally engaged Mr. Conrad to examine the
whole and to give his determination of the species which he had described. On
three several occasions, previous to 18G5, Mr. Conrad visited Albany for the
express purpose of making these determinations and identifications, labelling one
or more of each of those which he recognized as typical forms of the species.
Through these means and by later study and comparison it is believed that
nearly all the previously described forms have been satisfactorily determined.

The species described in this volume are illustrated from original drawings
made from typical or authenticated specimens. These specimens are chiefly
selected from the State Museum collections, which were derived from the
State Geological Survey, from subsequent acquisition by purchase, or from field
collections especially made for this object.

The work of lithographing the plates of the Lamellibranchiata was begun in
1870, and owing to the author's constant occupation in duties pertaining to the
State Museum, the supervision of the drawings and lithogra^jhy were chiefly
intrusted to Mr. R. P. Whitfield, who at that time was acting as draughtsman
and museum assistant, and the first thirty plates of this volume were drawn,
and lithographed, and arranged under his direction.

Unfortunately the species had not, at that time, been critically studied, and
in a final revision at a later period (1880) it became necessary to make an
arrangement of the genera and species which is not in accordanci" witli the
arrangement upon these plates. In the course of the work it has been Ibuiid
necessary to reproduce, in a more correct form, with illustration of tlie parts,
some of the figures of the earlier i^lates, as well as to give many additional species.
All these later illustrations are given on Plates Ixxxi-xcii inclusive, which are
arranged in systematic order, with the generic forms in their natural relation
to each othci-. It is to be regretted that these plates cannot be arranged in
consecutive order with those preceding, but in the earlier part of the work the

PREFACE. ix

plates were lithographed, from i to Ixxx, for illustrating the material then on
hand, and the additional plates can only come in after the latter number. This
want of conformity, however, affects only the plates, the text presenting the
genera and species in consecutive and systematic order, with cross-references
to the newly introduced plates.

The subdivision among those forms which have usually been referred to
Aviculopecten was found to be imperatively necessary for any strict classifica-
tion, and the other subdivisions among generic forms which have indiscrimi-
nately been referred to Avicula, Pterinea, Pteronites, etc., have been deemed
equally important. In these subdivisions, while the essential internal characters
have been regarded as of primary importance, the author, without violating
this rule, has endeavored to make such an arrangement of the species that the
student may determine the generic relations from the general form and exterior
markings alone. Since the fossil Lamellibranchiata are commonly found in an
imperfect condition, with the interior surface remaining attached to the matrix,
and only in rare examples, or in very favorable conditions, revealing the interior
structure, it becomes important to have some means of identification other than
that furnished by the hinge characters which are so rarely accessible. However,
notwithstanding the general arrangement according to external features, the
hinge and the interior structure have by no means been undervalued or neglected,
as is shown by numerous illustrations of these parts, which it is believed give
an amount of information not liefore published in any work upon this class of
fossils.

The synopsis of genera here presented is given without comment or com-
parison. In the succeeding volume the author proposes to give a resume of all
the genera described, and in the same connection a comparison with genera
described in other publications with some notice of the bibliography of this
class of fossils, so far as relates to the palaeozoic forms. In that notice the
reasons for the generic subdivisions proposed in the present volume will be
given in full.

In the final revision of the genera and species and in the preparation of the

B

X PREFACE.

tt'.\4 and the later plates ol" this volume the author cheertiilly acknowledges the
very valualjle assistance rendered by Mr. Charles E. Beecher.

Of tile mechanical and artistic execution of this work I may speak with
coiuniendation. Regarding the scientific character of that part of the work
already published and its value to the general public, we have had the testi-
mony of prominent scientific men ; ami I hope the present volume may be
reganled as an acceptable contribution tu oin- knowledge of a class of fossils of
which little systematic information has heretofore been given.

The author has been indebted for the use of specimens for study and illus-
tration to Dr. James Knapp, of Louisville, Ky., to E. B. Knapp, Esq., of
Skancateles, N. Y., and to Mr. Charles E. Beecher. To the collections of the
Cornell University he is indebted for two specimens illustrated in the present
volume, and for several others which are illustrated in the plates already pre-
pared for the next volume.

JAMES HALL.

Albany, Februoni, 1884.

SYNOPSIS

CHARACTERS OF THE GENERA

INCLUDED IN'

THIS VOLUME.

CLASSIFICA TION.

Pectenid^

Pteriniid^

AVICDLID^

Pernopecten.

Creiiipecte!!.
Aviculopecten.
Lyriopecteii.
Pterinopecten.

Pteriiiea.

s. g. Vertumiiia.

Actinopteiia.

Ptychopteria.

' Limoptera.

Glyptodesma.

Leiopteria.

Leptodesma.

Ptei'oiiites.

Palteopiinia.
. Ectenodesma.

- ineqnivalve.

Ambonychiid* I Byssopteria.

Mytilid^

Mytilai'ca s. g. Plethomytilus.

Mytilarca.

Gosselettia.

Modiola s. g. Mytilops.

, equivalve.

xii SYNOPSIS OF THE GENERA.

Pernnperlen* Winchdl. Shell like Pecteii. Hinge with a central cartilage pit
uiiii a crennlated liinge-plate on each side below the hinge-margin. This and
the lollow ing genus appear to be more nearly related to the genus Pecten than
In A \ ieidopecten.

Crenipecten, Hall. Like Aviculopecten in form. Hinge furnished with a series
of small cartilage pits throughout its entire length. Examples, pi. ix, figs. 12, 15.

Aviculopecten, McCoy, is emended to include those forms which have the hinge-
line usually shorter than the tran.sverse diameter, and both ears well-defined.
Test ornamented with rays. Example, pi. i, fig. 10.

Lyriopecten, Hall. Differs from the preceding in the short hinge-line and
very small anterior ear. Test usually' ornamented with strong rays. Example,
pi. viii, fig. 8.

Pten'nopecten, Hall. Hinge-line long. Ears not well-defined, being simple
expansions or extensions of the upper lateral margins to the hinge-line. Test
ornamented with rays. Examples, pi. ii, fig. 18 ; pi. v, fig. 6.

Pterinea, Goldfuss. Shell inequivalve, inequilateral ; posterior side alate ;
anterior end nasute or auriculate. Ligament internal ; ligamental area longi-
tudinally striated. Cardinal teeth two or more. Lateral teeth linear oblique.
Posterior muscular impression large, situated on the post-umbonal slope.
Anterior muscular impression small, situated within the rostral cavity. Test
iirnamented with rays. Examples, pi. xv, figs. 1-21 ; pi. Ixxxiii, fig. 12.

S. g. Veriumnia, Hall. Differs from Pterinea in having the right valve convex,
and the left flat or concave. Hinge area narrow. Example, pi. xxiv, fig. 12.

Actinopteria, Hall. Characterized from Pterinea in the absence of a inroad
striated ligamental area and strong cardinal and lateral teeth. Right valve
sub-convex. Surface with fine rays. Exam])lcs, pi. xvii. fig. 20 ; pi. xviii, fig.
13 ; pi. xix, fig. ■').

Plychopteria, Hall. Diflers from Actinopteria in the nasute anterior extrem-
ity, and large straight wing marked by a strong longitudinal fold. Hinge-
line narrow, linear ; furnished with one or two linear oblique cardinal and lateral
teeth. Surface with fine rays. Example, pi. xxiii, fig. 17.

*.See note, pnge 81.

SYNOPSIS OF THE GENERA. xiii

Limoptera, Hall. Shell large, inequivalve, inequilateral, subquadrate, strongly
alate on the posterior side, auriculate on the anterior end. Ligamental area
large, common to both valves, wider in the left valve, longitudinally striate and
extending to the cardinal extremities. The hinge has an oblique posterior
tooth and several cardinal folds under the beak. Anterior muscular impression
very small and deep, situated at the apex of the rostral cavity; posterior
impression large. Pallial line simple, formed of a series of small deep pits.
Inter-pallial area with numerous small pits for the attachment of umbonal
muscles. Test radiated ; radii becoming obsolete with age. Examples, pi. xcii,
figs. 3, 8, 9.

Glyptodesma, Hall. Shell aviculoid, erect or moderately oblique ; inequivalve.
Ligament external. Ligamental ai*ea striated, continuous. Hinge with two
strong lateral teeth, and numerous irregular transverse plications along the
cardinal margin. In form the shells of this genus resembles Actinodesma ;
but it has not the permanent diverging teeth of that genus. Surface marked
by concentric strige. Examples, pi. xi, figs. 3, 4; pi. xiii, figs. 5, 10; pi.
Ixxxvi, figs. 3, 8.

Leiopteria, Hall. Shell aviculoid, oblique, sub-rhomboidal. Anterior extrem-
ity auriculate ; wing large, extremity produced. Test without proper ra3^s.
Ligament external. Ligamental area marked by fine parallel longitudinal
stritB. Hinge with one or two oblique slender lateral teeth. The cavity of
the Ijeak is partially separated from the anterior end by a short partition or
diaphragm. Examples, pi. xx, fig. 17; pi. Ixxxviii, figs. 5, 27.

Leptodestna, Hall. In its prevailing forms it is similar to Leiopteria, except
that the anterior end is always nasute and acute instead of auriculate and
rounded. Hinge narrow, furnished with a slender lateral tooth just posterior
to the beak and nearly parallel to the hinge-line. Ligament external. Liga-
mental area narrow, extending the entire length of the hinge, marked by fine,
sharp, longitudinal strife. Test with concentric strise. Examples, pi. xxi, fig.
14; pi. xxii, fig. 21 ; pi. xc, fig. 28 ; pi. xci, figs. 9, 16.

Pteronites, McCoy. This genus is restricted to those jDossessing the characters
of the original types. Body very oblique. Hinge-line longer than the body

xiv SYNOPSIS OF THE GENERA.

ol tlir .<li<-ll. WiuLi anil liinge extended posteriorly. Test marked by concen-
tric stria'. Example, pi. xxii, fig. 26.

Poheophina. Hall. Shell .similar in outline to Pinna, gaping in trout. Test
marked li\ fine radiating lines. Body more convex and test with finer rays
tiian in tlie ordinary Pinna. Hinge-line simple. Example, pi. xxv, fig. 18.

KctenoJesma, Hall. Kesendjles Glyptodesma in outline, except that the ante-
i-i<jr wing" is uiore produced and both wings more acute at their exti'eraities.
Test ornamented with rays. p]xample, pi. xxiii. fig. 30.

Bijssoptiria, Hull. Shell erect, equivalve. Alate posteriorly, truncate, and
with a nasute projection in front. Surface radiated. Examples, pi. xxiii, figs.
21, 22: pi. Ixxx fig. 11.

Mijtilarca, s. g. Pleihomijlilus, Hall. Equivalve, mytiloid, gibbous. Shells
with a finely striated ligamental area. Posterior side subalate. Hinge-line
transverse. Lateral teeth small, oblique ; no cardinal teeth have been observed.
Test with concentric stride. Examples, pi. xxx, figs. 5, 7 ; pi. xxxi, figs. 2, 3, 7.

Mijtilarca, Hall. Shell equivalve, inequilateral and mytiliform with terminal
beaks and short hinge-line, which is bordered by a flattened, longitudinally
striated, ligamental area of greater or less extent. Cardinal teeth small,
situated beneath the beak. Posterior teeth small and oblique, situated at the
post-cardinal extremity of the hinge. Test free from radii, with a single
known exception. Example.s, pi. xxxii, figs. 9, 17, 19, 20.

Gosseleltia, Barrois. Shell subtriangular, truncate on the anterior side, sub-
alate on the posterior side. Ligamental area wide, longitudinally striate.
Cardinal teeth strong, situated under the beak. Lateral teeth elongate. Sur-
face marked by concentric striae. Examples, pi. xxxi, figs. 10-16.

Modiola, s. g. Mytilops, Hall. The fossils of this genus resemble Modiola and
Lithodomus in external form, and may also be compared with the fossil genus
Myoconcha. Hinge-line narrow, oblique, extending about one-half the length
of the shell. Pxaks ti'rminal. Examples, pi. xxxiii, figs. 16, 17; pi. Ixxxvii,
fig. 9.

INDEX

TO SPECIES DESCRIBED OR NOTICED IN THIS VOLUME.

[ The heavy-faced figures indicate a description of the species. ]

Actiiiodc&ma cruciforme, (Conr.id) Hall,

A. erectum, [ConvLul] lliiW,

ACTINOPTEKIA, Sail, .

A. auriculata, JTalt, .

A. Boydi, {Conrad) Ball, 'Xi, 113,

A, decussata. Hall, .

A. delta, Sail.

A. Doris, Sail,

A. epsilou, Sail. .

A. eta. Sail, . . . .

A. eximia, Salt, .

A, iota. Sail, . . . .

A. Kappa, Sail,

A. Leander, Hall,

A. niuricata. Sail,

A. perobliqua, (Conrad) Sail,

A. perstrialis. Sail,

A. pusilla. Sail,

A. subdecussata, Sail. .

A. teiiuistriata, Sail. .

A. tlieta. Ball,

A. zeta, Ball,

AUocardium alternatum, Sail. .

Ambonychia, Ball.

ANOIIIA, L, .

Athykis, McCoy,

Avicir.A, Klein, ....

A antjusHrostra, Conrad.

A. bella. Conrad, .

A. Boydii. Conrad,

A. cancellata, Phillips. .

A. Chemungensis, Conrad, .

A. Chemungensis, Vanuxem,

A. cruciformis, Conrad,

A. decussata, Hall,

A. erecta, Conrad,

36, 107,

7, 118, 160,

111,118,

. 181,

. 123,
124,
107,

118, 120,

PAGE.

. 153

133

129

121

16S

160

123

109

128

126

109

127

128

109

108

116

121

117

110, 113, 114

119, 120

. 125, 127

123, 123

expl. PI. 24

252

54

2S

36, 175

113

. 35

116

18

98

172

156

HI

156

3, 114, 11.1

Avicula jiaicUa, Conrail,

A. Icevis, Hall, .

A longispina. Hall,

A. muricata,\ia.\\,

A. orbiculata. Hall,

A. parilis, Conrad,

A. pecieniformis, Conrad,

A. peroMiqua, Conrad,

A. pleuroptera, Conrad, .

A. protexta, Conrad, .

A. qxiadrula, Conrad,

A reticulata, Sisinger,

A. ? signata. Hall, .

A. spinigera, Conrad,

A. tricostaia, Vanuxem, .

A. tuberculata, Conrad,

AVICULOPECIEN, McCoy,

A iEquilateralis, Sail,

A. alius. Hall,

A. altus, White,

A. bellus, (Conrad) Hall,

A caneellatus. Ball, .

A. cancellatulus, McCoy.

A. Caroli, ( Winchell) Ball. .

A. celsus, Ball,

A. Cleon, Sail.

A. convexus. Sail.

A. Coxanus, Meek tj- Worthen.

A. dolabriformis, Sail, .

A. duplicatus, Bali, .

A. ellipticus. Ball,

A. cxacutus. Ball.

A. fascicnlatus. Ball,

A. forniio, Sail,

A. Salleanus, D'Orbigny,

A. Idas, Ball, .

1,3,

1, 4,

113, 114, H6,

113,114,
183,

113. 114,

177,

. expl. PI,
31, 45, 74, 90,

35, 37, 3S,
. 16, 18,

14, 16

26,

17, I'J,

PAGE.
93

168

. 179

108

. 42

4

98

117

lis

184

115

114

29

180

4S

15

248

19

23

23

64

20

18

29

30

6

28

90

27

23,

5, 6, 8, 10,
11, 14, 22,

9, 11, 12, 14,

13, 20,

25

15
55
15

20
22

XVI

INDEX.

PAGE.

PAGE.

A vie

ulopoctcn iKnolo". Hall, .

33,

39

I.C

ioptci'in linsiiifi>rmis. Hdt.

173

A

innifniiH, ffnil.

34,

SH

L.

Milcholli, Hall.

100

A

Ily, //nH.

1*.

20

i

nitida, JIall,

172

A

Iinitii>. yjiiH,

14

Owoni, Hall.

170

A

nmrronalus, IlaU,

38

I.

I{afllies(|iiii. Hnll

161,16.5

100

A

orbirularis, McCoy,

,

4-2

I.

Sayi. Hall.

162,

171

A

orhif-iitatii-*, McCoy, .

a

L

Torreyi, Hall. .

174

A

Ortita. Hall.

. 11,

12

L.

Troosti, Halt.

107

A

onialti-*, Uall. ....

■n, 37.

.38

I.EPTODES.MK, flil//.

i'2;i. 17.1, 2.11

2.i9

A

pattilu!^, Hall,

24,

•26

I,.

acutii-iistruni. Halt.

234

A

peclenifDrmi.-*, IConriifl) Hall,

■i, 4.8,9,

12

L

A(ras<i/,i, Halt.

182

A

I'horru^, IlftU,

10

I,

al,'ituiii. Hall.

218

A

pU-liu*, nail. ...

21

I.

aliforme. Hall.

220

A

phnci'p-i, [Conrad) ffalt, . \,7t,f*.

*. !>. 11, li.

3.i

r,.

arriCoraie, Hall.

229,

231

A.

rrpletui. Hall, ....

11.

12

1,.

;iviforme. Hall,

224

A.

ruga-'slriaUis, Ilnll. 11,

I."!, 17, is.

19

I,

Herki, Hall,

185

A.

Snniluskyen.-i«. [Meek] Hall.

1.

■i

I.

Uillinj,'.si, Ball,

192

A.

scalniiluo, Hall, . 3, 7

, U, l.">, 1",

"22

h

Biton, Hall,

282

A.

8ignatiiH, nail, ....

29

L.

Cadnius, Hall, .

201

A.

equama, nail.

27

L

Clitus, Ball,

210,

212

A

striatu.-i, J7fi//. ....

22, i4.

30

I.

complanatiini. Halt. .

. 226,

227

A

tub-canccUaiux, Hall.

IS

L

Corydon, Ball.

218,

216

A

tonui«. 77n//,

M,

39

L.

f icon. Ball,

202, 204,

■.0.)

A.

undulatus. Hall,

72

L,

cur\'atum. Hall,

196

A

timlulatu:., McCoy,

72

L.

Demus, Halt, .

. 203,

205

A.

Winchdli, Meek, .

89

I,.

(lisparile, Halt.

186

A

(L'renipecten ?) inruUus, ^a/{.

30

L.

e.xtcnuatum, Ball,

. 207,210,211,214,

221

A.

(Pterinopecton ?) invali<lus. Hall.

31

L.

flacciduni. Hall,

225,

227

A

iP. ? ) tcrminalii. Halt,

32

L.

Hector, Halt, .

V.m. 209,

213

BVSSOPTERIA, Jlall.

252

I..

.lason. Ball,

213

B

rafliata. Hall, .

252

L.

lepiUum. Ball. .

195,

197

CREMPE'TEN, Hall,

:!1,8I,

90

L.

Lesleyi, Ball,

223

c.

nniplu.s. Hall, .

8J.

S3

I,.

Lichas, Bait, .

201, 2.30, 232,

2.34

C.

rrcnulatus, Hall. si .

82, s;i, «».

RC

L.

longispimmi. Ball, . 1

79. 181, 1.S2, 1.S4, 191,

19-2

C.

glaber, Hall,

85

I..

Loxijis, Hall, .

204

C.

impolitns. Hall,

83

I„

Lysanrlcr, BaU, .

. 215, 216,

218

C.

I..«on, Hall,

88

L.

.Maclurii, Ball, .

207. 223,

228

C.

liratus, Hall,

. SB,

87

L.

Maicellen.fc, Hall,

175

C.

mirropterus. Hall,

86,

87

L.

-Mathcii, Ball, .

10,1,

194

C.

obsolcliis, Halt,

83,

84

L.

Miclon. Ball.

197

C.

\(me\ic\\\, (Meek) Hall,

89

I,.

Menlor, Ball, .

205,

2;i6

C.

iPeclen) Winchelli, iMeek) Hall.

89

L.

Moitoiii, null.

. 1-2. l.^iO,

190

Errr

.NOI>E8MA, /Ta/i.

242

I,.

niytillri.ime. Hall.

235

E.

biroslralum. Hall.

242

L.

naviroinie, Hall, .

200

Entouujj, Meek,

81

L.

Nercus, Hall, .

217

Ultptodesma, Baa.

l.W,

IB.",

L.

OiTus, Halt,

215,

218

G.

ercrtum, [Conrad) Halt.

. 163,

157

L.

Oiodes, Hall, .

206, 214, 22:i.

235

G

orcctum var. nblir|iium, Hall,

155,

1.56

L.

Oius, Halt, .

219

G.

occidcntale, Hall,

157

L.

patillunl. Hall, .

220

GOSSEEETTIA, Darroit,

■Jfi.-.,

2B(i

L

Pclop^. Ball.

. 214. 220,

•225

O.

rctasa, Hall, ...

206

L

Ph.ion, Halt, .

. 230,

234

<i

triqiietra, 1 Conrad) Hall,

205,

2Bfi

I..

poteiis. Hall,

188, liW. 19:l. 198,

199

luoceramus Chemungmsii, Coniail.

2.VS

L

potens var, juvcns, Hatt,

189

/.

ovi/ormU, Conrarl.

25.-)

1.

propinqum, Ball, .

231

.Innira lon^icaiida, {D'Orbigny^.

48

J..

protcxtum, (Conrorfi Ball.

183

l.y.inpTEiii A, nail,

1-.'!),

158

L

qii;i(lr.alnin, Ball,

233

L

nitrnbyi, /7nH, .

165,

167

1.

lobustiim, Ball, . 1«I,

«■), 189, 191, 193, 198,

199

1.

CbeinunKcn»is, | Vanuxem) Hull.

172,

174

L.

Uogcrsi, Ball,

176. 17:*. 179,

187

I.

Coiimdi. Hall, .

15!>, lliO,

IBS

T,.

luilc. Ball,

221

1.

Di'kayi, Hall,

104, 172,

173

L

Sluiniarili, Halt.

180,

191

1.

Gal.bi, Hall.

160

I-.

."ocialc, BaU,

187

1,

Grecni. Hall.

KiO,

b>i;

L.

spinipcnini, [Conrad) Ball,

, 177, 181.

1S4

L.

tevis, Hall.

158

r.

SIcpbani, BaU,

104

L.

Leal, BaU,

inx

1,

Iruncatnm, HaU.

211

INDEX.

xvu

Leptodesma umbonatum, Sail,

L. umbonatum var. depressum. Rail, 199, 2i

Lima glaber, Hall, ....

L. macroptera, Coui'ad,

L 1 obsoleta, Hall, ....

L. rugmstriata, Hall, .

LiMOPTERA, Hall, ....

L. cancellata, Hall, .

L. cancellatavar. occidens, H. i^ W.,

L, cui'vata, Hall,

L. macroptera, i Conrad; Hall,

L. obsoleta. Hall,

L, pauperata, Hall,

Lyhiopecien, Hall, ...

L- anomia?formis. Hall, .

L. cymbalon, Hall,

L. Dardanus, Hall,

1,. fasclatus, Hall,

L. interradiatus, Hall,

L macrodontu.s. Hall, 43, 4.t, 46, 48

L,. magnilicus. Hall, . . 45, 47,

L. orbiculatus, .ff«;Z. .

L. parallolodontus. /J«Zi,

L. Polydorus, Hall. .

L. Priamus, Hall. ....

L. solo.v. /TaZi, ....

L. tricostatus, ( Vanuxem) Hall,

MERISTIhA, iJn(i, ....

MoDiOLA, Lamarck, ...

JIf. metella. Hall, ...

ilf. prcecedens. Hall,

M. (Mytilops) metella, ffiiZZ,

M. M. ) pra3cedens, Hall.

MODIOMORPIIA, Hall,

Monotis princeps, Conrad,

SIYTILAKCA, Hall, ....

44,

, 60, 53, 55,

4S, no, 51,

41, 43,
40,

45. 50,
43, aO, 54,

45,51,
47, 48,

175, 236,

M.
M.

M.
M.
M.
M.
M.
M.
M.
M.
M.
M.
M.
M
M
M.
jM.
M.
M.

iir

M
M-
M,

arenacea. Hall,
attenuata, 77rt?^
carinata, ffoZZ,
Chemungeusis, (C'onr.) if. .25'
libristriata, ( fTftiie if- Whitfield) Hall.
gibbosa, Hall,

lata. Hall

occidontali.?, ( White tf Whitfield) Hall,
oviformis, (Conra<l) Hall,
ponderosa. Hall, .
t>yramidata. Hall,
radiata, Hall,
regular!.?. Hall.
simplex, Hall,
triqaeter, (Conrad) Hall,
umbonata. Hall, .
{Pli'thomytilus) arenacea, Hall,

i.P.

(P.

(P.

(P

(P

(P.

Myttlops, Hall.
M. [Modiola

M. {M.

M. {M.

M. [M.

) cordiformis. Hall,
) Knappi, Hall,
) mytilimera, Conrad,
) ovata. Hall,
) oviformis. Hall,
) ponderosa, Hall, .

)lata,UiiU, .
) metella, Hall, .
] prtscedens, HaU, .
) simplex. Hall, .

PAGE.
. 198

203

246,

:00, 202,

85

251

Si

15

243

344

244

350, 251

244, 346, 250

243, 349

. 343

3, 40, 74

. 53

50

41

55

60

57

57

81

42

45, 47,

56

66

51

28

267

266

267, 268

368

. 367

234

4

266

253

360

258, 359, 2fil

358,259,261,362, 264

. 864

363

. 363

25!), 363,

175,

1,

263, 262,

364

260, 262

365, 256,
. 364,

262,

264
356

253
263
361

265

85r

254
254
356

254
254
265
255
267
262
268
267
261

MYTILUS, ....

M. Chemungensis, (Conrad) Pliillips &

M. fibristrlatus. White & Whitfield,

M. occidentalis. White & Whitfield,

M. Whitfieldianus. Winchell,

PaLjEOPinna, Hall.

P. flabella, Hall, .

P. recurva. Hall,

Pecten cancellatus. Hall,

P. 1 convexus, H.all,

P. 1 crennlatus. Hall,

/*, ? dolabriformis. Hall.

P. duplicatus, Hall,

P. Halleanus, D'Ortiigny, .

P. striatus, Hall, .

P. Tranquebarieus, Gmelin,

P. uudulatus, McCoy,

Pernopecten, Winchell. .

P. fasciculatus. Hall,

Pletho.hytilus, Hall,

P. ponderosus. Hall.

Pterinea, Goldfuss,

P. avis. Hall,

P Boydi. Conrad,

P. Chemungensis, {Conrad) Hall,

P. consimilis. Hall,

P. costulata, Roemer,

P. dispanda. Hall.

P. fasciculata, Goldfuss,

P. flabella, Hall, .

P. grandis. Hall,

P. interstrialis. Hall,

P longispina, (SaW)^. \ Miller,

P. pinguis. Hall, .

P. prora, Hall, .

P. protexta, (Coarad) S A. Miller

P. reprobus. Hall,

P. reversa. Hall, .

P. reversa var. avis. Hall, .

P. rigida. Hall,

P. ? suborbicularis. Hall,

P. triqueter, Conrail,

P. (Vertumnia) avis, Hall,

P. (V. ) reproba, .HaH, .

P. (V. ) reversa, flaii.

Pteronites, McCoy, .

P. inoptatus. Hall,

P. laivis, (Hall) S. A. Miller, .

P. muricatus. Hall.

P. profundus. Hall,

P. rostratus, Hall,

p. spinigerus, (Conrad) .S. A, Miller,

P. subdecussata. Hall,

Pterinopecten, Hall,

conspectus. Hall. .
crenicostatus. Hall,
cremtlatus. Hall, .
diguatus, Hall,
dispandus. Hall,
erectus, Hall, .
e.xfoliatus, Hall,
fllite.xtus. Hall,
Hermes, Hall,
imljocilis, Hall,

63,

175,

•Salte

103,

95, 98, 101,
90,

91, 92, 93, 97,

91,
103, 104, 105,

151, 208, 237,

67,

65, 66, 68, 69,
.58, 78, 79,

, 63, 64, 65,
73, 76,

59, 60,

67,

63, 64, 66, 67,

236

2.58

264

263

264

240

340

341

18

28

82

26

17

18

22

48

72

81

.55

2,53

254

91

107

113

103

100

93

97

93

98

91

96

179

93

107

183

72

105

105

101

80

365

105

106

104

239

339

158

108

239

338

177

110

248

74

81

78

67

77

77

61

70

69

75

xviii

INDEX.

PACE.

PAGE.

f*t«rinop«ct<.'n Insons, IlcUt,

SO,

61

PtyclioptLTln Kadoni, Hall.

138

P.

intormciliiis, nail,

08

P.

expan.sa. Unll. .

. 152

r.

inralulut. Hall, .

. 31,

(i7

P.

ralcata. flail.

136

!•

I.uttit. Ilnll.

63, B5, BO, 67, 75

, 107

P.

Galcnc. ffall.

. 148

/'

hwlut. Ilnll.

63

P.

f^ibho.-ia. ffalt.

149, I5U

1"

liiultirnilialn!!, Unll. .

67

P.

lata, Ilall.

. 145, 147

1'

Nt'ptunus, /7a//.

78,

79

P.

loliata, Ilall.

150

I-

no<lo;*U!4, Ilall.

60

P.

pciiata, Hall,

. 147, 148

!•

leBcxus. Hall.

S8

P.

Proto, Hall, .

189, 133

I-.

rcgul.iris, ffatl.

G9,

70

P.

Salamanc.'i, Ilall.

131, 134

I'.

spondylus, ffall. .

.

6S

P.

Sao, Hall, .

. 138, 1.34. 13... 137, 145, 148

P

itrictui. Hall.

74

P.

sinuopa. Hall, .

Ijg. 130

!■.

fuborbirularis, ITall,

U, lis, 77, 78,

80

P.

spatulala, ffall.

144

P.

terminnlls. Hall.

33

P.

Spio, ffall,

137, 138

V

iinilosus. llall.

78

P

Thalia, ffall.

148

V.

Vcrltiinniifl, Hall,

71,7(1. 7ft,

106

P.

Thetis ffall, .

. 135, 13B

P.

(.Vviculopccten ?) (*trictus.

Hall.

74

P.

Iri.ionalis. Hall,

140, 144

ITV

^IIOITF.RIA, Mali.

. i:3.

206

P.

Vamixcmi, ffall.

. 151

1'.

alatn. JIall, .

139, 141.

141

Sa.vgu

IXOI.ITES, McCoy. .

173

!•.

Ilccchcri, Ilall.

143

SOI.E.S

L

. 241

!•

clonfrnln. Sail.

141,

143

Spirife

■a Vcrnciiili. ifurchison.

131.189. 221. 2.38

!•

y.ncvato. Rail.

133, 137, 138, 142,

143

Vkuti

MMA, ffall.

104

LAMELLIBRANCHIATA

UPPER HELDERBEHG, HAMILTON, PORTAGE AND CHEMUNG GROUPS.

DESCRIPTIONS OF SPECIES.

AVICULOPECTEN, McCoy.

Section a.

AviCULOPECTEN PKINCEPS.

PLATES I, FIGS. 10, 11 ; V, FIGS 18, 19, 23, '24 ; VI, FIGS. 1-9; XXIV, FIG. 7 ; AND LXXXI, FIGS. 13-17.

Monotis princepH, Conrad. Annual Report N. Y. Geolog'. Sm-vey, p. 117. 1838.
Avimda parilis, " Procee.ling-s Aoacl. Nat. Sci. Phila., vol. 8, p. 239, pi. 112, fig-. 9. 1842.

Compare Avicidopecten A^a^idiiskyensis, Meek. Proceedings Acad. Nat. Sci. Phila., p. 161. 1871.
" Avicula parilis, Conrad? Meek. Palaeontology of Ohio, vol. 1, p. 197. 1873.
" A. pecteniformis, Conrad. Jour. Acad. Nat. Sci. Phila., vol. 8, p. 240, pi. 12, fig. 14. 1842.
Avictdopecten princeps, (Conrad) Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 5, figs.

18, 19, 23, 24 ; pl. 24, fig. 7. Jan., 1883.
Aviculopecten iSanduskyeims, (Meek) Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 1, figs.

10, 11. Jan., 1883.

Shell large, obliquely broad-ovate ; axis inclined more than 60° to the hinge-
line ; length and height nearly equal, varying within moderate limits ;
anterior margin convex ; the convexity increasing to the middle of the
postero-lateral side, thence truncated and extending in a straight line to
the beak, making an angle of from 30° to 40° with the hinge-line. Valves
depressed ; left valve regularly convex ; right valve nearly flat, or very
moderately convex.

Hinge-line straight, having a length of from two-thirds to more than
three-fourths the length of the shell, and extending anteriorly as far as
1

PALJEONTOLOGY OF NEW YORK.

the ;iiitcri>-latcr;il inai-iii with littk' variation. Beaks obtuse, nmiHU'd,
anterior to tlic mi. Idle ol' the liin<;e. rnil>o sul)ten(lin<r an anj,de of
ahout l;5(r.

Kars hiiL'f, triaiiiiiilar: |iosterior onr the hirj^er, and definc(l hy tlie abrupt
slojic of the side of the niiil.o. wliih" tiie anterior ear is separated l>_v a
ilislinct suhais ; lateral niarLiins concave, beconiin<i convex at tlir hinge-
line Hvssal-sinus broad, rounded, well-delincil and iiidirntcil on the ear
1)\ a snlcus extendinir to the cxti'einity of the beak.

The rifiiit valve is flatter and [)roportionuliy broader than the lelt. The
limits of the ears are clearly indicated by the rapid slope of the nmlio, and
the al)sence of strong radiating lines of ornamentation.

Test thin, marked iiy numerous regulai- alternating rays, which increase
in numlier li\ interstitial additions, and become broader and stronger towards
the margins. These radiating ribs are crossed by very fine, sharp stria? of
growth. < In tlie ears the rays are neai'ly obsolete, and the lines of growth
are sharper and stronger than on tlie body of the shell.

The internal mould ])reserves, in a sn])dued degree, the ornaments of
the exterior, and shows a simiile, continuous pallial impression, extending
nearly parallel to the margins, ami terminating in a large sub-ovate muscular
impression, which is posterior tt) the middle of the shell. The eavit}'
beneath the beak extends over the ligameutal area at that jjoint, forming
the cartilage-pit. In young individuals the ligameutal area shows three or
foui' small furrows at the heak, extending towards the extremities of the
hinge-line. Three of these furrows measure - mm. across. In larger and
older individuals, this furrowe(l ligameutal area is nuich more marked,
having frequently a width of ■") mm., and extends the entire length of the
hinge, showing more numerous furrows. At the beaks the furrows are bent
slightly outwards, otherwise, with gentle undulations, they run parallel to
the hinge line. This feature is a constant character in this and several
other .species, and is similar to that in many forms of Pterinea and
Lykiopecten.

The diminsions of the shells of this species are very variable. Large

LAMELLIBRANCHIATA. 3

individuals have a height of 80 inin. with nearly equal length, and a hinge-
line of 50 mm. The gi'adation from this form is very gradual to those in
which the height is equal to, or greater than, the length, and where the
length of the hinge-line is nearly equal that of the shell.

This species differs from A. pecteniformis by the larger anterior ears, with
more numerous and less prominent rays on the body of the shell. In specimens
identified as A. Sanduskyensis the umbo is more inflated and obtuse, while the
length is uniformly greater than the height. A. scahridus, which in some
respects resembles this species, is clearly distinguished by its characteristic
surface-ornamentation and the proportionally greater height of the valves.

This is one of the largest and the most abundant species in the lower and
middle portions of the Hamilton group. It is very easily distinguished by the
large ears with the furrowed ligamental area, full, obliquely ovate outlines, and
characters of ornamentation. It first appears in the Upper Helderberg
limestone in western localities. It is abundant in the lower beds of the
Hamilton group, especially in the coarser shales of the eastern central part of
the State ; while it is rare in the upper soft shales of the group, and scarcely
ever seen in the western counties.

Mr. Conrad suggests the prol)able identity of this species with the subse-
quently described form, A. parilis. A careful comparison of a large number
of specimens establishes this synonymy, and indicates the propriety of uniting
this form with the A. pecteniformis, Conrad. Aviculopeden Sanduskyensis, Meek,
which was afterwards referred by that author to A. parilis, Conrad ? belongs to
this species.

The apparent specific differences noted in the description of these three
forms are neither constant nor well defined; nor even to be regarded as
marking varieties. They are separately considered for the purpose of referring
to the original descriptions, and to correspond with the original specimens,
which are figured for two of the species. Farther investigation will probably
show more satisfactory proof of the validity of the present conclusions. The
original description of Mr. Conrad is as follows — loc. cit. :

4 PALEONTOLOGY OF NEW YORK.

" Monotis princeps. — Sla-U fonvt-x, (k-pressed ; car small, oiuarginate ; radiating
stria) numerous ; rugose, profound. Length about 3 inches.

" Locality, Cazenovia."

Mr. C<j.\KAi)'s de.sorii)tion of Avicula parilis is as follows (Jour. Acad. Nat. Sci.
Phila., Vol. VIII, p. 2.!U. 1842):

•• Avicula parilis, pi. 12, fig. 0. — Upper valve Ihit ; lowei- valve plano-convex;
surface with numerous, equal, filiform, prominent radii ; w ings angulated at
tip. the anterior one most acute, and nearly eipial in length to the j)osterior
wing ; apex not elevated above the hinge line ; anterior, posterior, and basal
margins forming an uninterrupted arched or rounded outline.

" Localilij. Cazenovia, Madison county. New York. Upper Silurian shale.

" A beautiful and common sjiecies, the larger valve much resembling a
Pecten.

"The Mo.NOTis j9rmce/)4-, of the Geological Reports of New York, is probably
the same sliell.

" The Hat valve is represented on the plate."

Formations and localities. \\\ liiiK'stone refericil to tlie age of tln' Upper
Ilelderberg group (Corniferous limestone), at Sandusky, Delaware, and near
Columbus, Ohio; ami also at the Falls of the Ohio.

In the coarser shales of the Hamilton group, at numerous localities in the
eastern and central portions of the State ; in the upper soft calcareous shales
of the group at Moscow. Livingston county, N. Y., and very rarely in the
western extension of the group.

AVICULOPECTEN PECTENIFORMIS.

i'l.ATE I, KIG. n.

AririiJn jMirtenl/nnniii. CoxnAD. Journal Aoiul. Nut. Sci. Phila.. vol. 8, p. 240. 1842.

Ariculoperleii i>ecUni/oriais, (Co.nkau) Hall. Pal. N. V., vol. v, pt. 1. Plates an.l Kxplaiiatiou.>i : PI. 1, ti;,'.

9. Jan., 1883.

Shell siil)-ovate oblifpie to the hinge-line ; length equal to the height ; anterior
aM<l ba.sal margins regularly rounded, the body of the shell extending in a
nearly straight line from the po.stero-lateral margin to the beak.

Left valve convex, retiching its greatest convexity at about one-third the
length of the valve from the beak.

LAMELLIBRANCHIATA. 5

Hinge-line straight, having a length of more than two-thirds the length
of the shell. Umbo prominent, sloping rapidly to the ears ; the sides sub-
tending a little more than a right angle. Beak prominent, situated a little
anterior to the middle of the hinge.

Ears triangular, unequal, the anterior about one-half the size of the
posterior one, lateral margins concave.

Right valve not observed.

Test ornamented by about 35 sharp, strong rays, with intermediate finer
ones, which are crossed by fine imbricating striae of growth. The radii are
not present on the ears. Internal characters not shown in the specimen
described.

The original of this species has a length of 47 mm. with an equal height.
The hinge-line measures 27 mm. The specimen is somewhat imperfect at
the extremities of the ears, and the posterior ear is not sufliciently extended
in the figure.

This form may be distinguished from A. princeps by its smaller anterior
ear, and less expansion at the base of the ears. The umbo appears more
contracted, and in the single known specimen is more prominent. The
principal radii are sharper and stronger, and the alternation of smaller ones
more regular.

In A. exacutus, which resembles this form, the beaks are nearer the middle
of the hinge-line, and the shell has a distinctly reticulate surface ornamenta-
tion, with the radii continued over the ears.

The specimen figured is the left valve, and is the original of Mr. Conrad's
description, no other specimen having been observed.

Formation and locality. Prom the corniferous limestone of the Upper Helder-
berg group, Schoharie, N. Y.

PALJEONTOLOGY OF NEW YORK.

AVK'ULOPECTEN ClKON.

•I.ATK I, Kl(.. 1.

Ariculopeclm Clem, Hall. Piil. N. Y.. vul. v, jit. 1. Plates ami Kxplanatiotis : PI. 1, tig-. 1. Jan., 1883.
Conijiare with the joiinjf of A. primrpx.

Shkll .^iiiiill, ovate; transverse axis slighth' oblique; length somewhat greater
than the lieight ; margins reguhirly romuled.

Left valve convex, the convexity c(|ii;il to alidut one-sixtli tlic Iciiutli of
the hinge-line. Tlio point of greatest convexity is just anterior to the
centre of the shell and towards the beak. Iviglit valve not observed.

Ilinge-line straight, length five-sixths the height of the entire shell.

Beak anterior to the middle of the hinge, not prominent.

Ears defined by the absence of radiating lines, but not Ijy any marked
change in the convexity of the shell ; lateral margins concave. The anterior
ear is limited by a shallow groove. The posterior ear is about twice the
size of the anterior.

Test thin, ornamented by a reticulation of fine radiating lines, and finer
concentric 'stria} of growth. The stronger ra3's have (me or two fmri- lines
between. The lines of growth exti'iid uwi the ears, but less distinctly than
over the l)0(ly of the slicll : ami otlicrwisc the ears are nearly smooth.

Interior not observed in the specimen described.

The length of this specimen is '21 mm., height 24 mm., hinge-line 'JO mm.

This form resemliles tlic young of A. princeps, l>\it it is less oMiipic. and tlie
ears less strongly defined tban in the young of that species as represented in
authentic specimens. Tlie figure does not quite represent the form of the
specimen, and the posterior ear is not so well defined as is shown in the
illustration. The form A. exacutus is very similar to this one; but that species
ha.s fewer and sharper radiating stria;, and the geological horizons of the two
are widely separated.

Formation and localitij. Tpper Ilelderberg limestone, Cohnnbus, Ohio.

LAMELLIBRANCHIATA. 7

AviCULOPECTEN SCABRIDUS.

PLATE III, FIGS. 3-13.

Aviculopecten scabridii.% Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 8, tigs. 3-12.

Jan., 1883.

Shell large, sab-circular, very .slightly oblique to the hinge-line ; length
somewhat greater than the height ; pallia! margin circular, becoming very
full posteriorly.

Valves depressed, moderately convex.

Hinge-line straight ; length equal to two-thirds the length of the shell,
marked by a thickening and inflection of the cardinal margins of the ears.

Beaks obtuse, rising slightly above and arching over the hinge-line,
situated just anterior to the middle ; umljonal angle 110".

Ears narrow, triangular, indented by a sinus which has a depth equal to
the width of the ears. The anterior ear of the left valve is one-half the
width of the posterior, but of nearly equal length ; in the right valve the
ear is larger, and has a well-marked byssal sinus.

The right valve is somewhat less convex than the left, but, with the
exception of the deeper anterior sinus, is very similar in character.

Test ornamented by about sixty strong, rounded rays, with some smaller
intermediate elevated lines, which are crossed by regular, prominent, sub-
imbricating lamellae of growth, about 1.5 mm. apart. On crossing the rays,
the varices of growth are bent suddenly upwards and backwards, forming
short semi-tubular spines. The strong rays are absent upon the ears, but
the lines of growth are numerous, and sharper than over the body of the
shell.

The specimens are mostly partial casts of the interior, preserving no traces
of the muscular impression, pallial line, or hinge characters, but retaining
strong evidences of the external ornamentation of the shell. See fig. 7, pi. 3.
Numerous individuals have a height of 55 mm., with usually a slightly
greater length. The length of the hinge-line in mature examples is about
45 mm.

8 PALAEONTOLOGY OF NEW YORK.

Tlii.s \V(.'ll-(lc'liiR'il spccii's is roiidily distinguished by the slight obliquity of
the l)0(ly of the shell to tlic liinge-line, and the marked characters of the
surfacf. it (lill'cis iVoni A. princeps i\w\ A. pedeniformis in iiaving strong and
regular concentric markings, whih- the rays in these species are niucli more
acute, and tlie axis of the shell is usually <|iiite oi)rK{m' to the hinge-line.
Specimens wliicli preserve tlu' exterior shell show very beautifully the sliort
spinous processes of the concentric lamellaj ; as shown, of the natural size, in
fig. 10, pi. ;i. E.xamples of the species are abundant, and have a considerable
vertical and horizontal range within the grouj] in New York.

Formalim and localities. In the shales of tlie Hamilton grouj), at Pratt's falls,
and Delphi, Onondaga county; Ludlowville, Cayuga county; Bellona, Yates
coimty ; Geneseo, Livingston county, and other places in western New York.

AVICDLOPECTEN EXACUTUS.

PLATE lU, FIGS. 18-22.

Aviculnpecten acaciUus, Hall. Pal. N. V., vol. v, i)t. 1. Plates and Explanations: PI. 3, tig-s. 18-22.

Jan., 18S3.

Shell of medium size, obliquely broad-ovate ; greatest longitudinal diameter
l)elow the middle ; height nearly equal to the length, transverse axis oblique
to the hinge-line ; basal margin full ami regularly rounded ; posterior margin
extended beyond the ear, and more convex than the anterior.

Valves equally convex ; the byssal sinus larger in tlie right valve, and the
umbo less ample.

Hinge-line straight, length four-dfths the longitudinal diameter, extending
nearly as far as the anterior maigin.

Beak o])tuse, oblique, anterior to tlie miilille of tiic hinge and of the valve ;
undx) ample, in some specimens of the left \;dve, the lieak arches over the
hinge-line, while in the right valve the beak rises from the hinge.

Ears triangular; posterior one somewhat the larger, margin concave,
extremity acute; defined from the umbo by a broiwl, shallow sulcus, an
obscure carination, and an abrupt change in tiie surface characters to sub-

LAMELLIBRANCHIATA. 9

dued striae. The anterior ear is well-defined by the sulcus extending from
the angular byssal sinus.

Test ornamented by about forty strong, sharp, continuous rays, alternating
in size with broader and concave interspaces, crossed by fine, sharp, crenu-
lating concentric striae. The ears show finer concentric stride and a few rays.

Pallial line impressed, continuous, extending parallel to the margin of the
shell about half way from the beak, terminating near the centre of the
posterior side, in a sub-circular, muscular impression, marked with regular
concentric striae. The cast preserves traces of the exterior markings, but
presents no definite characters of the hinge.

The largest specimen has a height of 35 mm. A medium-sized specimen
has a height of 26 mm. ; length 27 mm. ; hinge-line 24 mm.

This species differs from the young of A. princeps, in its more acute beak,
smaller anterior ears, and in having rays on both ears ; the rays on the body
of the shell are also stronger. It resembles A. formio in outline, but has more
sharply elevated rays, and less strong concentric striae. A. pedeniformis has
obtuse rounded beaks, and ears not marked by rays, which are distinguishing
features of that species.

Formation and localities. In the shales of the Hamilton group, Monteith's
Point, Ontario county ; and Hamburg, Erie county, N. Y.

AviCULOPECTEN FORMIO.

PLATE V, FIGS. 20, 21.

Aviculopecten formiu, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Exjilanations : PL 5, tigs. 20, 21.

Jan., 1883.

Shell of medium size, obliquely ovate, extended behind ; length equal to or
somewhat less than the height.

Valves depressed, slightly convex. The right and left valves are very
similar; the right being somewhat less convex, and having finer siu-face
markings.

10 PALJEONTOLOGY OF NEW YORK.

Ilin^ro-liiie straifrlit, t'xteiidinj: a.s lar as tliu aiitL-riur inargiu ; k'ligth two-
thinls thf lioijrlit of tlif sliell ; li<:;ainental area narrow.

Boaks well-delined, uot rising aljove the hinge-line, situated anterior to
the middle.

Posterior ear large, triangular, margin concave ; the ornamentation differ-
ing from that on tlie iunl)o ; defined hy a sliirlit depression and a rliange of
convexity. Anterior ear small, defineil hy a wcU-niiirkcd sulcus; hyssal
sinus deep; margin convex near the extremity of the iiinge-line. The area
of the posterior ear is more than twice that of the anterior.

Test ornamented hy ahout 35 rounded, radiating costa% with intermediate
smaller ones, crossed and crenulated hy regular striie of growth, of which
there are ahout 10 in the space of 5 mm. On the ears the radiating lines
are present, especially on the anterior ear, and the concentric striae are more
crowded than on the Ixxly of the shell.

The characters of the interior are not preserved.

The largest specimen has a length of 32 nun., and tlie liinuc-line measures
23 mm. A smaller specimen, preserving Imth valves, has a length of 'JO
mm., and height ahout equal.

This species is distinguished from A. exacutus hy the greater angle subtended
1(\ the sides of the mnho. ])\ its greater obli(piity, and the less sharp radiating
costjB of the surface. In A. Phorcus the length is comparatively greater and
hinge-line .shorter, the ears smaller, and the strong crenulatiug stria) of
growth do not occur.

Formation and localities. In the shales of the Hamilton grouj), at Fultonham,
iSchoharie (■oiuity ; and Hainilton, Madison county, N. Y.

Avit'ULurECTEN Phorcus.

IM.ATK V, KlU. •►;.
Atyicttloperten Phorcwi, Ham,. Piil. N. V., vol. v. jit. 1. Plates and Explanations: PI. 5, ti),'. 22. .Jan., l.'<83.

Shem. of medium size, ohliquely ovate ; height and length equal ; anterior and
ba.sal margins regularly rounded, becoming more convex towards the middle

LAMELLIBRANCHIATA. 11

of the posterior side, and thence concave to the beaks, giving the shell an
appearance of considerable amplitude behind.

Left valve regularly and moderately convex. The right valve is unknown.

Hinge-line straight, about one-half the length of the shell.

Beak rounded, extending to and situated near the centre of the hinge-line ;
umbonal angle smaller than usual, being about 90°.

Ears comparatively small, triangular, with concave margins ; posterior ear
the larger, separated from the body of the shell by a diiference in convexity
and the absence of radiating lines ; anterior ear defined by a sulcus.

Test marked by about 60 fine, rounded, radiating costa?, with a few inter-
mediate smaller ones, and fine stride of growth. The rays are absent on the
ears, but the lines of growth are more distinct than on the body of the shell.

The characters of the interior have not l)een observed.

The specimen described has a height of 37 mm., and a gi'eatest length of
26 mm.

This species differs from A. formio by its smaller ears, their distinct character,
and the general surface-markings. It resembles young individuals of A.
princeps ; but the comparative size and extent of the ears are very different,
while the body of the shell is more constricted at the base of the ears. A.
fasciculatus is very similar in the general form of the body of the shell ; but the
length is greater than the height. The alaj and the ornamentation of the test
are distinguishing characters.

Formation and locality. Hamilton group, Schoharie, N. Y.

AviCULOPECTEN FASCICULATUS.

PLATE V, FIGS. 9-17 ; AND PLATE LXXXI, FIGS. I-I.

Aviculopecttn fativUulatus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations; PI. 5, tigs. !t, 10,

12, 16, 17. Jan.. 1883.
Avieulopecten repletits, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 5, tigs. 13-15. Jan., 1883.
Orestes, " " " " " PI- 5, fig. 11.

Shell obliquely and transversely ovate ; height more than seven-eighths of the
length, produced behind. Pallial margins regularly rounded, becoming more

12 PALJEONTOLOGY OF NEW YORK.

convex towards tin- inidillo tjf the postero-lutcnd .side, and oxtendiiig in a
strai^rlit or slijrlitly concave line to the beaks.

N'alves moderately convex, the right one nicjre depressed when seen in
connection with the otlicr, shorter and comparatively less ol)Ii(iue.

Hinge-line straight, length nearly two-thinls tlic lu'igiit i>t' the shell;
extending, in yonng individuals, as far as the antiiim- iiinrgiiis.

Beaks prominent, well-defined, situated anteiior to the middle of the
hinge-line. Umbo very convex.

Ears of the left valve triangular, the posterior one larger, more attenuate
at the extremity, and defined hy a sulcus ; the margins concave from the
rapidly sloping side of the prominent umbo. Ears of the right valve much
narrower, and attenuate at the extremities, with fewer radiating lines,
marked by a very deep byssal sinus.

Test ornamented with numerous filiform, radiating striae, which are often
fasciculate, and fine concentric lines of growth, 'flic hroad fascicles of striae
often extend across one interval of growth, and on the succeeding interval
appear as regular or ii-rcgular striae without aggregation, or as fascicles of
finer stria?. This change does not always occur, hut is very characteristic
when seen, as in figure 17, plate 5, where the variation is so extreme that it
affects the outline of the shell. In young specimens the raj-s are regular,
with a slight fasciculate arrangement. The concentric lines are sharper and
more crowded on the ears and the rays are more subdued.

Interior not observed.

One specimen has a height of 30 mm., and a l(iii:tli oi' '.VI nun. ; another
specimen has a height of 23 nun., and a length of 2") mm.; the hinge-line
is IG nnn.

The form and surface markings distinguish this species. Tt diflers from ^1.
formio, A. princeps and A. pedeniformis in its surface markings ; and from A.
princeps especially, by the presence of radii on the wings.

Several varieties were designated in the preliminary examination as A.
replelus and A. Orestes ; hut a larger collection of specimens since these species

LAMELLIBRANCHIATA. 13

were indicated has demonstrated the identity of the several forms, notabl}*
figs. 14 and 15 of plate 5, which do not show a fasciculation of the striae.

Formation and localities. In the shales of the Hamilton group, Schoharie,
Onondaga and Madison counties ; also occurring in boulders of the coarse
shales of the Hamilton group at Chemung Narrows, N. Y.

AVICULOPECTEN IdAS.

PLATE III, FIGS. 1, 2 ; PLATE XXIV, FIG. i.

Aviculopecteii Idas, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 3, tig-s. 1, 2 ; 24, fig-. 4.

Jan., 1883.

Shell ovate-orbicular, transverse axis slightly oblique to the hinge-line ; height
nearly equal to or greater than the length ; outline full in front, not extended
posteriorly.

Right valve depressed ; moderately convex. Left valve not observed.

Hinge-line straight, length less than two-thirds the length of the shell,
extending farther towards the anterior than the posterior margin.

Beaks obtuse, well-defined, the umbo separated on each side, from the
ears by a distinct sulcus, which is more marked on the anterior side. The
beaks are nearly in the centre of the hinge-line, but somewhat anterior to
the middle of the shell.

Ears unequal. Anterior one about twice the size of the posterior, convex,
margins convex ; separated from the body of the shell by a deep sinus which
is continued to the beak as a distinct sulcus. Posterior ear triangular, with
margins concave.

Test thin, marked ))y line, concentric lines of growth, and about 80
rounded, radiating striae, which increase by interstitial addition, with the
interspaces less than the striae, of which there are from 7 to 9 in the space
of 5 mm. at the pallial margin. The surface characters continue on the
ears ; but upon the posterior ear the radiating lines are very subdued, while
on the anterior one they are quite prominent.

Interior characters not observed.

The largest specimen has a height and length nearly equal, and hinge-line

14 PALAEONTOLOGY OF NEW YORK.

•Jn mill. Aimtlicr iinli\ idiial liiis a lu-ight iiml length of 27 iimi., and liinge-
liui- 111 nnii.

This species differs from A. fasciculatus m its comparatively larger anterior
and smaller posterior ears, uliile the shell is less full hehiiid, and the fasciculate
surface has not l»een observed. In A. formio the posterior ears are much
larger, and the surface is distinctly reticulate. In A. scahridus the beaks are
more rounded, the wings more extended, and the surface quite diflerent. Some
forms of A. duplicatus and A. rugastriatus resenililc this species ; but the posterior
eais of those species are larger, the anterior \yA\v wider, and the surface
markings characteristic.

The specimen, figure 13, plate 7, from the Chemung group is very nearly
related to this species. A careful examination reveals the following difter-
ences. A. Itys is less oblique in outline, radiating striae less distinctly rounded,
inclining to angular, distance between them greater than the striaj themselves ;
the evidence of the ini])lantation of intermediate striae is obscure ; the
concentric lines are more distant and sharper, leaving the radii in the cast
distinctlycrenulate.

Formation and localities. In the Hamilton group at Fultonham, Schoharie
county ; shore of Cayuga lake ; and Darien, Genesee county, N. Y.

AVICULOPECTEN LAUTUS.
I'LATE ni, ?"u;s. ii;, it.

Avituli)j>etten laittus, Mai.i,. 1'jiI. N. V., vol. v, ]it. 1. I'latf.s ami Exiiliuiiitidii.s : PI. 3, fig^s. IG, 17.

Jjiii., 1S83.

SnEi.i. oliiiqucly o\atc, height e(jual to till' length, valves depressed, convexity
of right and left valves sub-equal.

Hinge-line straight, length about one-fifth less than tlie height of the
sliell, or in some specimens longer, extending as far as the anterior margin
of the valve. Beaks depressed, obtuse, anterior to the centre of the hinge-
line.

Ears sub-equal, triangular, flat, nnicronate at the extremities, margins

LAMELLIBRANCHIA TA. 1 5

concave except in the anterior ear of the right valve, which is convex ;
defined by the umbonal carinte, and by the absence of rays on the posterior
slope. Byssal notch in the right valve angular, deep, continuing to the
beak as a sulcus which separates the ear from the umljo.

The right valve, though very similar to the left, is not so high, and the
anterior ear differs in form from the corresponding one in the left valve.

Test thin, ornamented by about 90 sharp rays, with concave interspaces
having an equal number of intermediate finer rays, and crossed by numerous
regular, sharp concentric stria3. The markings on the ears are similar to
those on the l)ody, but less strong.

Ligamental area very narrow, and marked on the outer margin ])y an
inflection of the test. The other characters of the interior are not preserved.

The left valve of one specimen has a height of 2.3 mm., length 24 mm.,
hinge-line 23 mm. ; the right valve of the same has a height of 22 mm., and
a length of 24 mm. A larger specimen is 29 mm. in height, with an equal
length.

This species resembles A. exacutus in outline, l)ut differs in the lesser con-
vexity and obliquity of the valves ; the beaks are not prominent, and the
surface characters are finer and more delicate. Young individuals of A.
scabridus may be distinguished from this species by the more rounded and
obtuse beaks, and rugose rays, which are usually absent on the ears. A. formio
difiers by its oliliquity and the inequality of the ears, and the much stronger
striae.

Formation and localities. In the shales of the Hamilton group, at West
Bloomfield, Ontario county, and York, Livingston county, N. Y.

AviCULOPECTEN RUG^STRIATUS.

PLATE VII, FIGS. 8-11 ; and PLATE LXXXI, FIGS. 11, 12.

Lima rugwstr'iata, IIali.. Geolog'. Surv. N. Y. : Rep. Fourth Dist., ji. 264. 1843.

Avictilupecteii rugiextiiatiis, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 7, fig's. 8-11.

Jan , 1883.

Shell longitudinally ovate, oblique, more convex in front ; height one-fourth
greater than the length; outline oblique-ovate, with the posterior margin

If, PALMONTOLOGY OF NEW YORK.

depressed convex ; the anterior margin more convex, and the base abruptly
rimnded.

^'alv(•s coin (-'X, very similar, except that the right valve shows an acute
hyssal sinus.

Hiii-ro-line sliort, straight, length more than one-half the length of the
shell.

Beaks acute, prominent, anterior to the middle of the hinge.

Ears small, broad-triangular; posterior unc a little the larger, margin
slightly concave ; anterior ear defined by a distinct sulcus, which is narrow
and deep in the right valve, margin convex ; byssal sinus deep and acute.
The posterior ear is less distinctly limited in the right valve.

Test near the beaks ornamented by fine filiform rays, which are crossed
anil crenulated by sharp, concentric stria). Below the middle of the shell
the rays become large rounded plications, increasing ])y implantation or
bifurcation, and the regular concentric stride are stronger, distinctly crenu-
lating the I'ays, becoming foliate, and giving the surface a rugose appearance.
The rays and concentric lines arc present on the ears.

The interior is not preserved.

Two left valves have a height of 35 nun., and 'I'l mm.; length 29 mm. and
18 mm. ; the hinge-line 16 mm. and 10 mm. respectively. A right valve
of nearly the same proportions has a height of 33 mm., length 25 mm.,
and hinge-line 17 nini.

This species is distinguished from A. duplicatus by its comparativeh' greater
height, the obliquity of the valve, and the acute beaks ; the surface characters
of tiie two are very similar. A. cancellatus is more circular in outline, and the
anterior ears are larger than the posterior pair.

Formation and localities. Shales of the middle Chemung group, Philipsburg,
Itockville and Hobl)ieville, Alleghany county, N. Y.

LAMELLIBRANCHIATA. 17

AviCULOPECTEN DUPLICATUS.
PLATE VII, KIGS. 1-7; ANli PLATE LXXXI, FIGS. 9, 10.

Pecten dupHcatus, Hall. Geolog. Siirv. N. Y. : Rep. Fourth Dist., p. 264. 1843.

Aviculopecteu dupllcatvs. Hall. Pal. N. Y., vol. v, pt. 1. Pliitp.s and Explanations; PI. 7, fig.s. 1-7.

Jan., 18S8.

Shell ovate-orbicular, .sub-eciuilateral, height usually less than the length ;
greatest length below the centre of the shell, giving a somewhat truncated
appearance to the base.

Valves moderately convex ; very similar in dimensions and convexity ;
the central position of the beaks makes the valves nearly equilateral. The
right valve is marked by a deep byssal sinus.

Hinge-line straight, central, length from more than one-half to two-thirds
the length of the shell. Ligamental area narrow.

Beaks rounded, obtuse, sub-central. Umbo prominent, ample.

Ears small. Anterior larger and well-defined by the sulcus extending from
the sinus to the beak. Posterior one small, triangular; margins concave.
Byssal notch deep and abrupt.

Test ornamented with regular duplicating rays, which increase in strength
towards the margins, crossed by fine, regular, foliate, concentric expansions
of the test. In well-preserved specimens this character of surface gives a
decided limate appearance, and somewhat resembles A. rugcRstriatus. In
weathered specimens this surface character is subdued to a reticulation and
crenulation. Near the beaks the shell is nearly smooth ; towards the
margins it is sometimes marked by strong, rounded plications. The rays
and concentric lines are continued over the ears, and the anterior ear usually
has several stronger plications.

A right valve, somewhat larger than usual, has a height of 31 mm., length
.85 mm., and hinge-line 20 mm. A medium example has a height of 27 mm.,
length .SO mm., and hinge-line 18 mm. Younger forms vary slightly from
these proportions ; a small left valve measures 23 mm. in height and length,
with a hinge-line of 15 mm.

18 PALAEONTOLOGY OF NEW YORK.

This spocit-s R'soiiiMcs A. rugastrialus in siirlaoe charactors, Imt it is less
obrujiu' and jjroportionally nuicli longer, with beaks more obtuse. The outline
of A. cancellatus is more nearly cireulju-, and the directiijn of the transverse
axis is <)bli(|ue. From A. scabridus it differs in its shorter hinge-line and
siiiidlfr ears, as well as in the surface markhigs.

Formalion and localities. In tlie calcareous shales of the middle Chemung

group, Ro{-k\ ille. Ilobbieville and Philipsburg, Alleghany county ; f^ast TJaii-

<lolph, Cattaraugus county, N. V.: and Mansridd an<l Sullivan. Tioga county,

Pennsylvania.

AvirULOPECTEN CANCELL.\TUS.

I'L.VTK vn, FIGS. 12, U-19.

Pecten lancrllatiix. IIai.l. (Jeolofr. Siirv. N. V. : Rep. Fourth Dist. 184^.
Ncit Af'u-iiliijKctiii laiudUUidiut, McCoy.

Peclru ffiilltanius,* i)'OnBt(;.vY. Pnxlrome ile Pala;ontolog'io, vol. I, i>. 87, No. 70S. 1847.
Avicidiiitecten mth-caiuxUatiui, H.\i.L. Pal. N. Y., vol. v, jit. 1. Plates ami Kx|ilanation.« : PI. 7, tijrs. 12,

14-HI. .Jan., 1S,SS.

Shell small, broadly ovate, oblique, height a little greater than the length;
anterior lateral margin full and rounded ; posterior lateral margin, lielow the
ears, gentl\ curving.

Right valve regularly convex, slopmg somewhat abruptly to the posterior
ear.

Hinge-line straight, equal to two-thirds the length of the shell.

Beaks, anterior to the middle of the hinge-line, well-defined, obtuse.

Posterior ear small, undefined, the lateral margin concave, not projecting.
Anterior ear marked by a deep sinus, with a sulcus extending to the beak ;
lateral margin rounded.

Test marked by fine, regular, rounded, radiating lines, cros.sed by regular
sharp, concentric strise, producing an evenly cancellate surface. The
posterior ear is marked by the concentric strife with obscure radiating
lines; the anterior ear is rugo.se fn mi the prominence of from four to six
strong rays.

*This name wa.s jii-opo.'OHl by il'Orbijfny as a HiiUntitute for Pecten faiu-ellalii.t, a name pi-eoccupieii l)y
Pliilli|H< foi- an Oolitir fotwil. The latter \h )n'o)>ably a true Pecten, ami there seems to me no sufficient
iTiuHiM why thi- on>,nnal name may not be retained. Avivula cauctllala, Phillips, Palaeozoic Fossils, is
probably not an Avienlolieeten.

LAMELLIBRANCHIATA. 19

Interior characters not known.

The original of this species is 20 mm. in height, 19 mm. in longitudinal
diameter, and the length of hinge-line 12 mm. Another specimen is 14
mm. in height and 12 mm. in length.

This species is distinguished from A. duplicatus and A. rugastriatus by the
less rugose surface, smaller size and different outline. The form of the ears
and byssal sinus is very similar to A. duplicatus, but differs in the regular
reticulate surface ; that species is also a comparatively longer shell. It is in
shape more like A. rugastriatus.

Formation and localities. In the middle members of the Chemung group,
at Philipsburgh and Rockville, Alleghany county; Conewango, Cattaraugus
county ; and near Westfield, Chautauqua county, N. Y.

AviCULOPECTEN ^QUILATERALIS, n. Sp.
PLATE LXXXII, FIG. 1.

Shell of medium size, transversely ovate, erect, equilateral ; height equal to
the length ; lateral and basal margins regularly rounded ; upper anterior
and posterior margins extending in nearly a straight line to the beak.

Left valve slightly convex ; greatest convexity on the umbo.

Hinge-line straight, nearly tw.o-thirds the length of the shell, situated
centrally.

Beak well-defined, situated near the centre of the hinge-line.

Ears sub-equal, triangular, defined from the umbo by a sinus in the margin,
with a sulcus extending to the beak ; margins slightly convex ; extremities
rounded.

Test ornamented with al)out sixty regular, straight, alternating rays,
crossed by fine, irregular strias of growth. The rays are present on the ears,
and are more numerous on the anterior ear.

The specimen described has a length and height of about 38 mm., and
hinge-line of 22 mm.

•j„ PALJEONTOLOGY OF NEW YORK'.

Tliis specit's is distinjruislio.l hy its erect equiliiteral form, sub-equal ears, and
the fitronj;;, refjularly alternatinjr radii.

Formation and locality. Intl..- upper beds of tlie Chemung group at Alleghany
Sulpliur Springs, Warren county, I'a.

AVICULOPECTEN ItYS.
iM.ATi; VII, vm. i:t.

Ariculo,Ktl.:, Itijx, Ham.. I'al. N. V.. vol. v, pt. 1. Pliiti^s .111. 1 KxphiiniticMis : PI. 7, tifr. 13. Jiin., 1SS3.

SiiKi.i. small, broadly ovate, lengtli nearly equal to the height, slightly ol)li<iue ;
margins regularly romultd. nearly equilateral.

Right valve depressed-convex. Left valve not known.

Hinge-line straight, sub-central, having an extent of a little more than
one-half the greatest length of the siu'll.

Beak acute, directed slightly forwai-il. Posterior >nnl)onal slope making a
"•reater an<de with the liin;j,c-line than tlie anterior, riiiho subtending a
right angle.

Ears nearly e(iual. Anterior ear the larger, ol)tuse at the e.xtreiuity,
marked by several strong radii, separated from tlie innbonal region by a
strong sulcus. Posterior ear narrow, triangular, margin concave, separated
bv a distinct sinus IVom the body of the shell, with no rays of ornamenta-
tion ; olituse-angular. Hyssal sinus well-delined.

Surface marked l)y sub-angular, rounded radii, which are regularly increa.sed
in size Avitli the growth of the slu'll, but rarely increased in number by
implantation; concentrically markc(| by line, regular, tlircad-likc stria' of
growth.

Interior characters unknown. Hinge margin apparently simple.

The specimen described has a length of 2o mm., height 27 mm., hinge-
line 1-5 mm.

This .species is less oblicpie than .1. Idas, the hinge-line shorter, radii not
present <m the posterior ear, surlace markings coarser; and rays increasing
more rapiilly in size though fewer in nund)er. In A. cancellatus (==A. Halleanus,

LAMELLIBRANCHIATA. 21

d'Orbigny), the valve i.s more convex, beak more obtuse, and the concentric
marking forms a prominent feature.

Formation and locality. In the Chemung group at Conewango, Cattaraugus
county, N. Y.

AviCULOPECTEN PLENUS.

PLATE XXIV, FIG. 3.

Avk-uhqiecleu pJenua. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 24, tig-. 3. Jan., 1883.

Shell sub-orbicular, sub-equilateral ; transverse axis nearly vertical to the
hinge-line ; height one-sixth less than the length, giving a marked fullness
to the outline of the sides.

Left valve convex, the convexity equal to one-sixth the length of the
shell. The point of greatest convexity distant one-third the length from
the beak. Right valve not <)l)served.

Hinge-line straight, nearly central, the length more than two-thirds the
length of the shell.

Beak obtuse, situated centrally with regard to the hinge-line, and also to
the body of the shell ; umbo rounded.

Ears sub-equal, triangular. Posterior ear mucronate at the extremity ;
margin deeply concave. Anterior ear acute at the extremity, and the margins
convex; separated from the uml)o by an abrui^tly sloping sulcus extending
to the beak.

Surface ornamented with about 130 regular, rounded, close, filiform radii,
crossed by very fine, sharp, concentric striae. The surface markings are
jiresent on the ears, the radii distinct and stronger than on the adjacent
portions of the shell. The rays become more frequent and finer from the
basal margin in both directions towards the ears.

Interior not preserved in the specimen described.

The height of the specimen is 25 mm., length 30 nun., hinge-line 21 mm.
On the lower margin there are 9 rays in the space of 5 mm.

22 I'ALjEONTOLOCY OF NEW YORK.

Ill loriii. tliis species lie;irs considcriililr rcscniljlance to A. duplicatus ; l)iit
the siiil'ace markings are quite diflereiit, and the extremities of the hinge line
are more acute in tliis species. In A. scabridus the beak is not so well defined,
tlic cars usually more extended, and the coarser rugose radii of that species
are characteristic. This form resembles some varieties of A.fasciculatus in the
surface characters, but differs in the obli(|uity of the shell and form ol' the ears.
It differs from A. Idas in the iiiorc rotund form, more numerous and elevated
rays, and larger ears.

The single valve described appears to Ijc well distinguished from all the
other species, and possesses characters too remote to be united with any of
those described from right valves alone.

Formation and locality. In arenaceous shales ol" the middle Chemung group,
near Elmira, X. Y.

AviCULOPECTEN STKIATUS.
PLATE X, FIGS. 3, 4.

Pectim, striatu.1. Hall. Geulop. Siirv. N. Y. : R(>ii. Fcnirtli l)i.«t. 1S4;^.

ABiatlopectnt. xtrlatu.^. Hall. Pal. N. Y., vul. v, \>t. 1. Plat<'s and l';x]ilaii.iticiii.« : PI. 10. tig-s. 3, 4.

.Jan., 1SS8.

Shell trans\ersely ovate, scarcely oblique, nearly equilateral, width some-
what greater than the length.

Ilinge-line straight, two-thinls the leiiuth of the shell, situated centrally
in regard to the body of the shell, not I'xtending as far as the margin.

Beak central to the liiiige-line, well-defined, arching over the hinge;
uiiilio prominent, the sides subtending a right angle.

Ears sub-equal, triangular, ilefniei] l)y the rapid slope of the sides of the
und)o. Anterior ear the larger, limited by a broad sinus; mai'gius slightly
convex; extremity rounded. Posterior ear acute at the extremity : margins
concave.

Test ornamented with line, rounded, clo.sely arrangetl, regular radiating
striai, from 12 to 14 in the space of 5 mm. at the pallial margin. Some
specimens show a slight flattening of the rays and also fine lines of growth.
The ears present the same surface characters.

LAMELLIBRANCHIATA. 23

Ligamental ai'ea narrow, well-marked, its width is .5 mm. in a specimen of
20 mm. in height.

The oi'iginal specimen of this species is 20 mm. in height, 18 mm. in
length, and the hinge-line 13 mm. Another specimen is 13 mm. in height,
11 mm. in length, hinge-line 8 mm. The largest specimen found has a
height of 22 mm.

This species resembles A. celsus more nearly than any other form here
described ; it differs from that one by its much smaller ears with concave
margins, more obtuse umbo, regular, equal striae, and comparatively shorter
form. The two species agree in the non-obliquity of the body of the shell to
the hinge-line. This species has a vertical range from the middle to the upper
members of the Chemung group, but is not abundant.

Formation and localities. In the Chemung group at Painted Post, Steuben
county ; Chemung Narrows, Tioga county, N. Y. ; and in Bradford, Tioga and
Warren counties, Pennsylvania.

AviCULOPECTEN CELSUS.

PLATE Vn, FIUS. -29, 30.

Amciihipectcit altux. Hall. Pal. N. Y., vol. v, pt. I. Plates and ExplanatiuiKS : PI. 7, tigs. 29, 30.

Jan., 1883.
Not Apiculoptcteii altii-s. White. Bull. U. S. Geol. Surv.. vol. v, p. 110. 1879.

Shell small, ovate cuneiform, sub-equilateral, not oblique; height one-fifth
greater than the length ; pallial margin rounded to near the ears, where the
sides of the shell are nearly straight.

Right valve convex ; the greatest convexity being equal to one-fourth the
length of the hinge-line. Left valve not observed.

Hinge-line straight, length tliree-fourths the length of the shell, not extend-
ing as far as either lateral margin.

Beak acute, straight, extremity pointed, arching over the hinge-line ; umbo
prominent, subtending an angle of 80°.

Ears broad-triangular, large, flat, sub-equal, the margins slightly convex ;
extremities rectangular ; separated from the body of the shell by a moderate

•J4 PAL.EOyTOLOGY OF NEW YORK.

sinus, iind Irom the sides of the uiiiho l»y a sulcus ; the byssal sinus is deep and
rounded.

Test iiiarkid liv line alternatinj!; filiform radiatinj? stri*, which are absent
on tlic cars, except as two or three alternating undulations. Fine lines of
growth mark tiie test and extend over the ears.

Liganiental area lincin- and marked ])y an inflection of the hinge-margin.

The specimen has a height of 1". mm. and a length of 13 mm., hinge-
line 10 mm. About 13 rays occupy the space of 5 mm., measured near the
basal margin.

This form may be distinguished Ity its equilateral proportions, acute,
straight apex, the non-ohli([uity of the transverse axis to the liinge-line, the
broad, triangular ears and the alternating surface striae. These characters sepa-
rate it from A. striatus, to which it is most nearly allied.

Formation and locality. In sandstone of the conglomerate, associated with
till' upper Chemung grou]». at Salamanca, Cattaraugus county, N. Y.

AviCULOPECTEN PATULUS.

PLATE VH, KlUS. 3-', Si.

Avicidopeeten patiilm. Ham,. P.il. N. V.. vol. v. i>t. 1. Platc.^* ami Exiilanations ; PI. P. tif.'s. 32, 33.

Jan., 1883.

Shell large, longitudinally broadly elliptical ; height alujut five-sixths as great
as the length. The axis of greatest height is at right angles to the hinge,
and the line of greatest length is parallel to the hinge and across the middle
of the shell. Basal margin convex, somewhat Hatteiied in the niiddle.
Lateral margins very lull, and curving rapidly to tlie ears.

\'alves convex, the convexity e(|nal to one-fourtli tlic length of the hinge-
line. The right and left valves do not difler conspicuously in character, so
far as observetl.

Hinge-line apparently straight, equalling nearly two-thirds the length of
the shell, central, not extending as far as either lateral margin.

LAMELLIBRANCHIATA. 25

Beaks obtuse, rounded ; umbo prominent, straight, central, well-defined
by its gibbous form and the rapid slope of the sides. Umbonal angle 110°.

Ears broad-triangular, sub-equal, separated from the body of the shell by
a broad, deep sinus ; margins concave below, becoming convex above the
middle ; extremities rounded.

Test ornamented by regular, sharp radii, with broader concave inter-
spaces, and some finer radii, crossed by irregular crenulating lines of growth.
Near the basal margin of a large specimen, there are five of these rays in
the space of 10 mm. A smaller specimen has eleven rays in the same
space.

The interior is not preserved.

The measurements of one individual are: height 55 mm., length 69 mm.,
hinge-line 41 mm. ; of another specimen, height 26 mm., and length 30 mm.

This species nearly resembles in form A. e/lipticus, and difi^ers bv its sharp,
crenulated radii, while that species is marked by strong, rounded, continuous
plications; and the hinge-line is comparatively somewhat longer. These two
forms differ from others in their broad longitudinally elliptical outlines, and
the amplitude of the umbones.

Formation and locality. In conglomerate and sandstone, associated with the
Upper Chemung group, at Rock City, near Salamanca, Cattaraugus county, N. Y.

AviCULOPECTEN ELLIPTICUS.

PLATE Vn, FltJ. 31.
Avieulopectenelliptieits, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 7, Hg. 31. Jan., 1883.

Shell large, longitudinally broadly elliptical, equilaterial, not oblique ; height
equal to about four-fifths of the length ; margins regularly convex and rapidly
curving to the beak.

Left valve capacious, convex. Right valve not observed.
Hinge-line straight, central, length equal to about one-half the length of
the shell.

Beak straight, central, obtuse, rounded ; umbonal angle about 110''.
4

26 PALEONTOLOGY OF NEW YORK.

Ears Pub-equal, Iji-oad-triiiiiixulur, flat ; marffins slij;litly convex; extromitios
R'ctanjiular, (k-liiieil In a gcntlu .sinus, wliic-h is dfi'per helow the anterior ear.

Test niarke<l liy aljout 35 strong, rounded, radiating continuous plications
which are wider than the interspaces. These radii are absent on the ears.
The stria? of growth are irregular and niaik tlie entire surface of the shell.

Internal characters not observed.

A large specimen has a height of 53 mm., length 06 mm., hinge-line 34 mm.

This species differs from A. patulus in its shorter hinge-line, and the strong
rounded radiating plications.

Formation and locality. In sandstone of the upper part of the Chemung
group at Meadville, Crawford county, Pennsylvania.

AviCULOPEC'TEN D0LA15IUF0KM1S.
PLATE VII, KIG.il.

Pecten) dohrhrifurmh, Hall. Geoli>{r. Suiv. N. Y. : Rep. Fourth Dist., p. 2ti.'). 1843.
Avitndoptvteii dulabrifonni.s. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 7, tijf. 21.

Jan., 1883.

Shell small, .-^iil)-nrliicular, slightly olilicpie; lieight nearly equal to the length;
margins regularh iDuiided, becoming more inflated and convex posteriorly.

Right valve moderately convex. Left valve unknown.

Hinge-line straight, central, more than two-thirds the length of the shell.

Beak central, straight, obtuse, rounded, not rising above tlie hinge-line;
iiiulx) well ilefiiied by the rapid slope of the sides and the tiatness of the
ears.

Ears triangular. Hat; margins slightly concave; extremities obtuse-angular.
Posterior ear of the right valve about one-third larger than the anterior.
Byssal sinus not marked.

Test cancellate, marked li\ line radii and eoneeiitric stria', wiiicli cliai-
acters are also preserved on the ears.

Internal characters not known.

A right valve has a height of 11 mm., length 12 mm., and hinge-line 8 mm.

LAMELLIBRANCHIATA. 27

This small species somewhat resembles A. squama in the form of the body
and surface markings, but the beak is less acute and the anterior ear compara-
tively smaller, without distinct sinus.

Formation and locality. In the arenaceous shales of the Chemung group at
Philipsburg, Alleghany county, N. Y.

AviCULOPECTEN SQUAMA.

PLATE VU, FIG. 30.

AvicidopecteiisqtMma,HK\.h. Pal. N. Y.. vol. v. pt. 1. Plates and Explanations : PI. 7, tig-. 20. Jan., 1883.

Shell transversely broad-elliptical, slightly oblique ; height aljout nine-tenths
of the length.

Right valve moderately convex. Left valve not known.

Hinge-line straight, length two-thirds the length of the shell, extending in
front as far as the anterior margin of the valve.

Beak rounded, not rising above the hinge-line, situated posterior to the
centre; umbonal angle 90*^.

Posterior ear small, triangular, narrow, with concave margin ; not strongly
defined ; extremity angular. Anterior ear large, convex, broad-triangular ;
extremity obtuse ; margin convex ; separated from the body by a deep rounded
sinus, and from the sides of the umbo by a distinct sulcus.

Test marked by very fine radiating striae and irregular lines of growth.
These surface characters extend also over the ears.

Internal characters not known.

The specimen described is 11 mm. m height, 12.5 mm. in length, and
hinge-line 8 mm.

This species differs from A. dolabriformis in its more acute beak, absence
of regular concentric striae, and much larger anterior ear.

Formation and locality. In the Chemung group at Philipsburg, Alleghany
county, N. Y.

28 PALEONTOLOGY OF NEW YORK.

AVICULOPECTEN CONVEXUS.

PI.ATK VII, FIGS. •>', 'ii.

Pe-iinl coniv.riis, Hall, neolog-. Siii'v. N. V. : Rej). Fourth Disl., p. 2S5. 1843.

.<4rit-u/<'/>e</oi amvexus. Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 7, tife'K. 22, 23.

Jan., 1883.

Shell small, sub-orbicular, not oblique; heiglit somewhat greater tliiui the
length; margins regularly rouudcil.

Left valve very convex, convexity equal to a1)out oiic-third the length of
the shell. Right valve not known.

Hinge-line straight, central, length three-fifths the length of the shell.

Beak prominent, straight, central, rounded, arching over the hinge-line ;
the sides of the um])o subtend a right angle.

Ears broad-triangular, extremities obtuse-angular. Posterior ear of left
valve smaller than the anterior, defined by the abrupt slope of tlic umbo;
margin slightly concave. Anterior ear convex; margin straight; separated
from the umbo l)y a very deep and narrow sulcus. Byssal sinus small.

Test marked by fine irregular radiating striag and finer regular concentric
lines ; the same surfiice characters are continued over the ears. The speci-
men is exfoliated and the radii represented in the figure are partially restored.

Interior characters unknown.

The original of this species has a height of 12.5 nini., length 12 mm., and
hinge-line 8 mm.

The remarkable convexity of the left valve distinguishes this species from
all the other forms here described. Its orbicular outline, prominent beak and
deep anterior sulcus are also characteristic. In general appearanco tlie body
of the shell resembles some forms of Athyris and Meristiiia ainoiig the
Brachiopods, but its pectinoid character is well marked.

Formation and locality. In the shales of the Chemung group at liockville,
Alleghany county, N. Y.

LAMELLIBRANCHIATA. 29

AviCULOPECTEN SIGNATUS.

PIRATE VII, FKJ, -24.

Avwiilaf signata. Hall. Ueolngr. Surv. N. Y. : Rep. Fourth Dist., p. 2(ir). 184;i.

Av'uiilopfcten sif/natus. Hall. Pal. N. Y., vol. v, pt. 1. Plate.s and Explanations : PI. 7, tiij. 24. Jan., 1883.

Shell small, obli(|uely isub-elliptical, the longest diameter making an angle of
about 45° with the hinge-line ; height and length nearly equal.

Left valve depressed, slightly convex. Right valve unknown.

Hinge-line straight, length more than two-thirds the length of the shell,
extending in front as far as the anterior margin.

Beak very obtuse, rounded, depressed, directed forward, situated near the
centre of the hinge.

'Ears triangular, sul)-equal, flat. Anterior ear separated from the umbo by
a sulcus ; margin convex ; extremity rounded. Byssal sinus moderately deep.
Posterior ear not well-defined ; margin slightly concave ; extremity obtuse-
angular.

Test conspicuously marked by fine, regular, lamellose concentric lines, and
a few irregular, radiating, indented striae.

Interior characters not observed.

The original of this species is 11 mm. in length and height; the hinge-
line 8 mm.

This species is distinguished by the oblique, elliptical outline of the body of
the shell, the depressed, obtuse beak, and the well-defined concentric striae.

Formation and locaUlij. In the Chenumg group at Rockville, Alleghany
county, N. Y.

AviCULOPECTEN CaROLI.

PLATE IX, FIG. .5.

AvwiiUrpecten Cat-oil, Winchell. Proceeding's Acad. Nat. Sci., Phila. 18(i3.

Aviculupecten Carcli, (WtNCHELL) Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 9, iig. :").

Jan., 1883.

Shell small, sub-circular, not oblique, length and height equal ; basal margin
regularly rounded.

30 PALJEONTOLOGY OF NEW YORK.

Left Viilvc coiivox, the convexity r((ual to aliout onr-sixtli of tlie longi-
tudinal (liainetci-. Uidit valve unknown.

Hinge-line straight, length three-fourths of the diameter, extending nearly
to the anterior margin of the shell.

Beak olitu.xc, jiroiiiiiient, central, rising above the hinge.

Ears triangular, nearly equal, separated Irom the umbo by distinct sulci.
Anterior oar with slightly convex margin; extremity rounded. Byssal sinus
(k't'p. Margin uf posterior ear concave; extremity abruptly niucronate.

The test (as preserved on a partial cast of the interior) is marked b}^ about
45 regular alternating, rounded rays with equal interspaces. The lines of
growth are fine and obscure on the specimen. The ears are marked by
tVoiii live to eight rays similar to those on the body of the shell.

The ligamental area is a linear furrow along the hinge-line ; cartilage pit
small, situated mider the beak.

The left valve described has a height of 17 mm., and an equal length;
hinge-line 13 mm.

In the original description of this species mention is made of small, spinose
processes from the concentric stria; ; these do not exist in this specimen,
which is a partial cast of the interior..

This species is distinguished from A. striatus by its more circular form,
obtuse beak, and stronger radii. Compared with A. elongatus, the wings are
smaller, and the height comparatively much less.

Formation and hcality. In the yellow sandstone of the Waverly group at
Newark, Ohio.

AVICULOPECTEN (CrENIPECTEN ?) INCULTUS.

IM.ATK I.\. KIG. 3.

Aviculitj>et:ten (Creiiipecteiif) iiicul liis, Hali,. I*:il. N. Y., vol. v, |it. 1. Plates and Kxplanatioiis : PI ii. tig.

8. Jim., 1883.

Sirp;Li, small, longitudinally very broad-elliptical, nearly circular, not oblique to
the hinge-line, sub-etpiilateral ; height ,soni(nvhat less tlian the louiiitiidinal
tliameter ; basal margin regularlv rounded.

LAMELLIBRANCHIATA. 31

Right valve depressed, convex. Left valve unknown.

Hinge-line straight, central, length one-half the length of the shell.

Beak obtuse, rounded, not rising above the hinge-line ; sides of the umbo
straight.

Ears small, sulj-equal, narrow-triangular, separated from the sides of the
umlx) by sulci. Margin of posterior ear concave ; extremity obtusely angular.
Anterior ear defined by a deep, angular byssal sinus ; margin convex ;
extremity rounded.

The external markings of the test are not preserved. The cast of the
interior is nearly smooth. Pallial line faintly impressed. At each side of
the umbo there is a shallow, undefined impression, nearly parallel to the
margin, extending to al)out the middle of the lengtli of the shell.

A specimen of the right valve has a height of 15 mm., length 17 mm.,
hinge-line 8 mm.

This species approaches very nearly several forms referred to Crenipecten.
More perfect material may show the hinge to be crenulate, which character
would exclude it from Aviculopecten.

Formation and locality. In conglomerate, referred to the Upper Chemung
group, near Olean, Cattaraugus county, N. Y.

Aviculopecten (Pterinopecten ?) invalidus.

PLATE I, FIG. 18; AND PLATE LXXXII, FIG. 21.
Ptt'rhi,<>pec-teiiinvalidu.<<, Hall. Pul. N. Y., vol. v, \>t. 1. Plates mid Exiilanations : PI. 1, fijf. IS. Jan., 1883.

Shell small, rhoml^oidal ; length and height nearly equal, moderately oblique ;
margins regularly rounded, full behind ; the greatest posterior extension is
below the middle.

Left valve depressed-convex. Right valve unknown.

Hinge-line nearly straight, length a little more than the length of the
valve, and extending anteriorly.

Beak obtuse, rounded, situated just anterior to the centre of the hinge-line,

32 PALJEONTOLOGY OF NEW YORK.

tlircctfd sli-ilitly IVnwaid, depressed. Umbonal region moderately prominent,
subtending an angle a little less than 90°.

Ears triangular, flat, extremities jicut«. Anterior ear smaller, ilefined by
a sulcus ; margin nearly straight. Posterior ear with the margin concave,
extremity aciiiniiiatr : having no strong radiating striae.

Test, as indicated in an exfoliated specimen, marked by a few fine radiating
stria\ with wider interspaces whieli are marked by finer radii. Anterior
ear sliuwing the same eliaracters. Posterior ear I'ree from rays. Fine 0(m-
centric stria> cross the rays, ami stronger concentric wrinkles interrupt them
and proihice a slight crenulation of the radii.

The specimen is Id.-') nun. in length, 10 nun. in lieight, with hinge-line a
little more than 1 1 mm.

This .species resenil)les in tbrm the young ol' Pterinopeden dignatus, but differs
in the liner radiating lines on the liody of the sliell, the concave margin, and
absence of rays on the })osterior ear.

Formation and locality. In tbe black Marcellus shale at Cherry Valley, Otsego
county, N. Y.

AVICULOPECTEN (PtERINOPECTE.X ?) TEKMINWLIS.

PLATE I, FIO. 3.

Plerint)ptctenterminalis.U\u,. Pal. N. Y., vol. v, jit. 1. Plates and Kxplaimtidii.-s : PI. l.fiy. 3. Jan., 18S3.

iSliKi.i, small, rliomlioidal : hody of the sliell obli(piely ovate; length a little
greater than the height ; margins regularly rounded, somewhat extemled
lichind.

hfft valve very convex. Kiglit valvi' unknown.

Hinge-line straight, central, eipial to the length of tlu' sludl.

Heak acute, prominent, directed a little forward, arching over the hinge-
line. Uml)o elevated, sul)teudiug a right angle.

Ears triangulai-; margins concave; extremities acute. Posterior ear larger,
iindefnied. Anterior ear limited 1)V a shallow sidcns. TJvssal sinus moderate.

LAMELLIBRANCHIATA. 33

Test thin, marked b^- fine sharp radii, with wider interspaces, which show
one, two or three finer rays, crossed by fine crenulating lines of growth.
The same characters of marking extend over the ears.

Internal characters not known.

The specimen is 14 mm. in length, 12 mm. in height, with hinge-line
15 mm.

This species, in sm-face markings, bears a slight i-esemblance to a young
individual of Avkulopedm princeps ; but the undefined ears and proportionally
longer hinge-line distinguish it.

Formation and locality. In the upper layers of the Corniferous limestone ;
Young's farm, Williamsville, Erie county, N. Y.

Section h.

AviCULOPEOTEN IGNOTUS.

PLATE I, FKi. 2.

Avictil(rpectenignotus,Y{ku.. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 1, tijr. 2. J.an., 1883.

Shell of medium size, transversely and obliquely sub-ovate ; height about five-
sixths of the length ; margins regularly rounded, full on the anterior and
posterior sides.

Left valve slightly convex, nearly flat. Right valve unknown.

Hinge-line straight, central, length nearly equal to the height of the valve.

Beak obtuse, rounded, low, directed toward the anterior.

Posterior ear large, broad-triangular, separated from the side of the uml)o
by a wide shallow sulcus ; margin slightly concave ; extremity obtuse-
angled. Anterior ear less than one-half the width of the posterior, narrow-
triangular, separated from the umbo by a deep byssal sinus and a distinct
sulcus, extending to the apex of the beak ; margin convex ; extremity
rounded.

Test thin, about .5 mm. in thickness; marked with about twenty-five
irregular, rounded radii, which are crossed by very fine concentric strise, and
occasionally interrujjted by varices of growth. The rays are conspicuous

34 PALJEONTOLOGY OF NEW YORK.

oviT till' cfiitri.' di' tlie valve, Ik'ioiiuii;; oliscun.- toward the margins. The
ears show the concentric stria» only.

The characters of the interior are not known.

A specimen of the lel't valvi' measures 'l■^ mm. in heitilit. H'.i mm. in Icniitii,
ami the hinjie-line "J! mm.

This species in general expri'ssion resemhles A. tenuis, hut is distinct in its
smaller anterior ear, more obtuse heals, Drhicular I'orm, and more inx'gular and
stronger rays. Their geological positions ari' widely separated.

Formation and locality. In soft shaly heds of the Corniferous limestone, which
constitute the upper portion of the group, at Lapham's mill, near A'ictor,
Ontario county, N. Y.

AVICULOPECTEN INSIGNIS.

I'I.\TK I, Kli; 8; IT.AIK UI, Klti 13; ami IT.ATK T.XXXI, VU. 7.

AnU-iUiijM-HiH liuilgiivt. Hall. I';il. N. V.. vul. v. pt. 1. Plates jiiul Kxiilauatidii.s : PI. 1, tijf. S ; ]>l. S. lijr. 13.

Jan.. 1SS3.

Shell less than medium size, sub-rhomboidal, moderately ohlicpie, about one-
third longer than high; hasal margins rounde(l ; anterioi- and [xisti-rior mar-
gins obtusely angular or abruptly roundt-d, and I'xtending along the cardinal
slopes in a direct line to the lieak.

IJoth valves are (piite convex; light valve somewhat the less convex.

Hinge-line straight, nearly equal to the length of the shell.

Beak obtuse-angular, prominent, directed forward, nearly central. Unibonal
regiiju ample, the sides subtending an obtuse angle, and sloping more
a})ruptly to the anterior than t<j the posterior margin.

Ears sul)-eiinal, triangular. Anti-rior ear concave or Hat. ddiiicd hy a ilis-
tiiicl sulcus; margin dei'ply concave; extremitx' acuminati'. Hyssal sinus
ileep and well-markcfl. Posterior ear flattened, di'lined by the absence of
the stronger radii; extremity slightly acute; nuu'gin concave.

Test thin, marked by strong radiating costa^, which in the left valve are
abruptly elevate<l and increase by interstitial addition ; crossed by infiecjueiit

LAMELLIBRANCHIATA. 35

elevated thread-like concentric crenulating striae, whicli sometimes give a
nodose character to the radii, and by finer lines of growth. Tlie right valve
is marked by rounded rays arranged in pairs, bifurcating on the umbo,
crossed by fine concentric lines of growth. The radiating stria3 are obscure
on the ears, being more strongly marked on the anterior one.

The interior characters have not been observed.

The largest specimen has a length of 27 mm., height 20 mm., hinge-line
23 mm. A smaller specimen of 18 mm. in length has a hinge-line of precisely
the same length.

The specimen figured on plate 1 is a young individual and does not well
show the characters of the species which are better seen on the other figures
referred to. See plate 81, fig. 7.

This species is less oblique, and the extremity of the posterior ear is less
mucronate . than in A. hellus and A. ornatus. The surface markings are very
similar to the former, but cpiite distinct from the latter.

Formations and localities. In limestone above the Marcellus shales, at Staf-
ford, Genesee county ; in the softer shales of the Hamilton group at Moscow,
Livingston county ; and at Hamburgh, Erie county, N. Y.

AviCULOPECTEN BELLUS.
PLATE II, FIGS 5, (I, 9; AND PLATE LXXXI, FIG. 8.

Avicida heUa, Conrad. Annual Geolog. Rop. N. Y., i>. .")4. 1841.

Avimlopeeteii hdtus (Conrad), Hall. Pal. N. V., \-<il. v, pt. 1. Plates and Explanations: PI. 2, Hgs. 5,

1), St. Jan., 1883.

Shell small, longitudinally sub-elliptical'; height equal to two-thirds or three-
fourths of the length ; margins regularly rounded.

Valves moderately convex ; the right valve somewhat shallower than the
left ; very similar in form and ornamentation.

Hinge-line straight, the length a little greater than the longitudinal
diameter of the shell, nearly central, extending equally beyond the posterior
and anterior margins.

3G PALEONTOLOGY OF NLW YORK.

Hcaks (jl)tiist.'-aii;ik'il, (lirLTtril I'orwunl, placed aiitorior to the luiddlf of
tlu' valve; sides of the uinho carinate, and descending al)riiptly to the ears.

Posterior ear flat or concave, narrow-triangular, wll-dcrnu'd liy the
carinate sides of the umi1)o. am! liy the absence of the strong surface radii ;
niarsrin concave; t-xtriMiiitN acute, iiuicronate. Anterior car alioiit two-thirds
as long as the posterior one, triangular, convex; defined tiy a deep sulcus,
ami the angular cai'dinal slope of the uud)o; margins of the ears in the
left valve straight or concave ; in the right valve, convex ; extremities acute-
angled. In the left valve the byssal sinus is liroad and rounded ; in the
right valve it is a deep, angidar notch.

Test of the left valve marked by from iU to -"jU regular, continuous, thread-
like ray.s, alternating in fours, with three degrees of prominence, crossed and
crenulated by fine, regular, concentric striae. The surface of tiie rigiit valve
is neaily the reverse of this, having broad, flattened rays, arranged in pair.s,
regularly liifui'cating, with iiari-ow concave interspaces which coiii'spond to
the rays of the opposite valve. The posterior ears show several delicate rays
e.vtending from the apex of the beak over their upper portion.

The interior is not known.

A specimen preserving both valves has a height of 14 nnn., length 10 mm.,
and hinge-line 20 nnn. A right valve lias a height of 1 1 nun., length 1*1' mm.
A left valve has a height of 12 nun., length IG mm., hinge-line 17 mm.

This species in appearance resembles A. ornatvs, and differs in its longitu-
dinally narrower outline, more obtuse beak, the mmierons rays, and the
ab.sence of strong, lamellose, concentric fimljriav The two forms are of a
group resembling several species in a parallel group of the genus Actinopter.v,
whi(di are rennirkable as possessing an aviculoid character (when compared with
•some recent species of Avicula) ; in the strong rays, the deep anterior sulcus
and byssal sinus separating the anterior ears from the body of the shell.

Formation and localities. In the .soft shales of the Hamilton group at Tinkler's
Falls, Onondaga county; Hcllona, Vates county; and near Norton's Landing,
Cayuga lake, N. Y.

LAMELLIBRANCHIATA. 37

AviCULOPECTEN ORNATUS.

PLATK II, FKiS 7, S; AND PLATE III, FI(i. U.

AvU-idiipecten oruatu.i. Hall. Pal. N. Y.. vol. v, pt. 1. Plates and Explanations: PI. 2, tigs. 7, 8; pi. 3,

tiff. 14. Jan., 1883.

Shell small, longitudinally oblique-ovate, sub-rhomboidal ; length and width in
the propoi'tion of three to four ; margins regularly rounded.

Valves depressed-convex; left valve somewhat more convex than the
right, and a little larger.

Hinge-line straight, slightly less than the length of the shell, central with
regard to the body of the shell.

Beak obtuse-angular, directed forward, situated a little anterior to the
middle.

Ears sub-equal. Posterior one the larger, triangular, flat or concave,
defined by the abrupt post cardinal slope of the unijjo ; extremity acute ;
margin concave. Anterior ear defined by a deep sulcus ; byssal sinus deep,
more strongly marked in the right valve.

Test of the left valve ornamented by about 25 strong, sharp, elevated rays,
and wide interspaces which are marked Avith a smaller ray ; crossed by
undulating, concentric stria3 which are curved backwards between the
stronger rays, producing arched fimbria?. The right valve shows the
radiating striae originating near the umbo, which is smooth, jiiid increasing
by a double bifurcation, giving them a fasciculate appearance ; they are
crossed ])v tuidulating, concentric striaj. The ears are marked by strong,
radiating lines and fine, concentric stria?.

Internal characters not observed.

The length of the largest specimen is 18 mm., height nearly 15 mm.,
and hinge-line about 17 mm.

This species, in form and general appearance, is very similar to A. bellus ; it
differs conspicuously in the ornamentation, with proportionally shorter posterior

38 PAL.EONTOLOC'Y OF NEW YORK.

ear. Both species sliow the smooth area on tlie uinlid of tlic lidit \;ilve; a
character not observed in any other species liere described.

Formation and locality. In the Hamilton L'roup; shores of Canandaigua lake,
Ontiirio county, N. Y.

AVICULOPECTEN MUCRGNATUS.

I'l.ATK III. Fro. 15.

Am-iiJitpert) 71 mucroniitiix. ITai.i,. Pal. N. V., vol. v, pi. 1. Plait's ami Kxiilanatiim.s : PI. S, ti^;. I.j.

.Ian., 1S.S8.

Shell small, i-otiind-ovate, slightly oblique; length a little greater than the
height. Basal and anterior margins regularly rounded; posterior margin
lull, abruptly sloping to the beak.

Left valve strongly convex. Right valve not observed.

Hinge-line straight, ecpial to the greatest length of the shell, extended
iintcriorly.

Beak obtiise-angidar, directed forward, nearly central. Umbo deep, sides
subtending an ol)tu.se angle, sloping to the ears.

Ears sul)-equal. Anterior car narrow-triangular, elongate, acuminate,
delined liv the deep byssal sinus anil marked sulcus; margin concave.
Posterior ear wider, limited by an undefined sulcus ; margin concave ;
extremity acute.

Test ornamented by rounded i-adii, wliicli bifurcate towards tlii' margin;
crossed by prominent, regular, concentric stria'.

Hinge-area sim|ilc.

The spei'imcn lias a Iciigtli of Id mm., luught 15 mm., hingf-liuc 111 mm.

This .species differs from A. insignis, A. bellus and A. ornatus in the liillowing
characters: the anterior ear is narrower, the outline of the shell is less
oblique, and the form is more rotund.

Formation and locali 1 1/. In cdcarcous slmlcs of the Hamilton group at Dresden,
Yates county, N. Y.

LAMELLIBRANCHIATA. 39

AVICULOPECTEN TENUIS.

PLATE VII, FIGS. .>7, 28; AND PLATE LXXXI, FIG. 0.

Aviculopecten tenuis, Hall. P;tl. N. Y., vol. v, pt. ]. Plates and Explanations: PI. 7, figs. 27, 28.

Jan., 1883.

Shell small to medium size, sub-orbicular, transverse axis oblique ; length and
height equal ; margins regularly rounded, somewhat extended behind.

Left valve slightly convex, nearly flat. Right valve unknown.

Hinge-line straight, nearly central, ; length five-sixths of the longitudinal
diameter.

Beak directed forward, not rising above nor extending beyond the hinge,
anterior to the centre of the hinge-line and of the valve. Umbonal angle 9(P.

Ears large, broad-triangular, unequal, separated from the sides of the umbo
by a broad, shallow sulcus. Anterior ear about one-half the size of the
posterior, flat ; margin convex ; extremity obtuse-angular. By ssal sinus broad
and comparatively shallow. Posterior ear marked by a low, convex undula-
tion, adjacent and parallel to the sulcus ; margin straight or slightly concave;
extremity rectangular, pointed, more obtuse in mature specimens.

Test marked by about twenty-five strong, regular radii, with broader
concave interspaces, and also, in well-preserved specimens, smaller interme-
diate rays. The specimens described are casts of the interior, and show but
faint traces of concentric lines of growth. The ears are mostly free from
surface markings.

Pallial line impressed, continuous, situated about one-half the distance
between the apex of the beak and the pallial margin of the shell. Muscular
imjjression elliptical, within the concavity of the valves adjacent to the
sulcus of the posterior ear. Hinge-ligament without marked characters.

The largest specimen has a height of 29 mm., length 30 mm., and hinge-
line about 23 mm. A smaller individual is 23 mm. in height, 23.5 mm. in
longitudinal diameter, and hinge-line measuring 19 mm.

This species resembles in some respects A. ignotus, and is distinguished by
its transverse form, greater obliquity, larger anterior ear in the left valve.

40 PALAEONTOLOGY OF NEW YORK.

rectiuijiular la-jik, luul more re<rularly alternating rays. Both of these forms
are reniarkalile for tlie very sli<:lit convexity of the left valve.

Formation and localities. In calcareous sandstone of the Upper Cliennuig
group, Randolph and Salamanca, Cattaraugus county, N. Y.

L Y l\ I () P E C T E N , Hall.

LviaOPECTEN PARALLELODONTUS.

PLATK IV, FR;S. 1, 2.

LyrUrpecUn paraUclodmdiui, Hall. MS. for Pal. N. Y., VdL v. 1877.

" " " Catalojj^ue Anier. Piiljt-dziiii' Fossils, S. A. Mili.kr. Cincinnati, 1S77.

" '• " Pal. N. v., vol. V, lit. ]. I'lati-s and Explanations: PI. 4, tip;. 1,2.

Jan., 1883.

Shell of medium .size, sub-orhicular, not oblique; height somewhat less than
the longitudinal diameter; margins regularly rounded.

Right valve moderately convex. lA'ft valve unknown.

Hinge-line straight; anterior poitioii not preserved in tlie spcciiiicii ; fiom
the beak to the extremity of the posterior ear its length is one-half the
loiioitiuliiial diauictcf ol' the sliell.

Reak obtuse, rounded, slightly ol)lique, anterior to tlie centre of the valve ;
uiiil)oiial region ainplc.

Posterior ear large, broad-triangular, flat ; margin straight or slightly
concave; extremity rectangular. Anterior ear not jtreserved.

Test tliiii. iTiarked by about !)0 regular, alternating, rounded radii, with
concave interspaces, and crossed Ity fine, elevated, sharp, cancellating stri:\> ;
these are crowded over the jiosterior ear, and the I'ays are there more
numerous and less regnltirly alternating.

The mould of the interior preserves, afoiiiul the margin, traces of the
stronger rays, and shows a moderately im]iresse(l pallial line, with apparently
an ovate, niiiscnlar impression iicai- tlic iniiboiial region. ('artilag(>-])it suiall,
deeply intlented. Ligameiital area narrow, niarlved 1(\ two or tlircc slender,
parallel grooves, extending to the posterior extremity ; and one i>r two

LAMELLIBRANCHIATA. 41

shorter, accessory grooves extending for a short distance from the cartilage-
pit, and parallel to the longer folds.

The specimen consists of the exterior and interior impression of a right
valve ; it is 38 mm. in height, 43 mm. in length, and the incomplete hinge-
line measm'es 20 mm. from the beak to the end of the posterior ear.

This species differs from L. orbiculatus in its comparatively greater length,
the convexity of the right valve, and the regular alternation of the rays. It is
remarkable as the only pectenoid form yet observed in the Schoharie grit,
while similar forms are numerous in the Upper Helderberg limestone.

Formation and locality. In the Schoharie grit, Albany county, N. Y.

Ltriopecten Dardanus.

PLATE I, FIG. 5.
Lyriapedm Dardanus, Hall. Pal. N. Y., vol. v, jit. 1. Plates and Explanations: PI 1, fig. ,'). Jan., 18S3.

Shell of medium size, orbicular, transverse axis not oblique ; height a little less
than the length ; margin regularly rounded.

Left valve moderately convex. Right valve unknown.

Hinge-line straight, length nearly equal to the transverse diameter of the
valve, extending as far as the posterior margin.

Beak obtuse, rounded, straight, anterior to the middle of the hinge-line
and to the centre of the longitudinal diameter.

Anterior ear small, narrow-triangular, flat, separated from the umbo by a
broad, undefined sulcus ; margin slightly convex above the sinus ; extremity
rectangular rounded. Posterior ear large, broad-triangular, flat; margin
straight or slightly concave, rectangular to the hinge-line ; extremity mucro-
nate.

Test marked by about forty strong rounded continuous rays with wider
concave or fiat interspaces, and sometimes a smaller intermediate ray ; crossed
by sharp, elevated concentric striae. The rays are fine and little elevated on
the ears, while the concentric striae are conspicuous.
6

-\-2 PALAEONTOLOGY OF NEW YORK.

Interior cliaracttTs not observed, except an indication of a wcll-(lelinc(l
lifiainental area.

The specimen is 4.-3 mm. in heij^ht, 48 mm. in lengtii, and the hiuge-liuc
4o mm.

Thi.s species resembles L. parallelodontus, bnt difl'ers in tlie comparatively
larirer and more extended posterior ear and fewer and stronger rays, without
rejruhir alternation of size. L. orbiculatus is more elongate, with more numerous
radii and less defined anterior ear.

The figure is from a gutta percha cast of a moidd of the exterior of the shell.

Formation and locality. In the limestone of the Upper Ileldeilicrg group,
Le Roy, Genesee coimty, N. Y.

Lykiopecten orbiculatus.

PLATE IV, FIGS. S-8; AND I'LATK I.X.XJXII, FIG. i.

Amriila orlriciilala. Hall. (Jeolog-. Siirv. N. V. : Kcp. Kouitli Di.-^t., ji. 202. 1S48.
LyrUipfcten ivrbicalatus, Hali,. MS., vol. v, pt. 1. 1877.

" " " Tatalog-ue Anier. Palaeozoic Fossils, S. A. Millkr. lf<77.

I'jil. N. Y., vol. V, pt. 1; Plates ami Explanations: PI. 4, Hjrs. .3-8.
Jan., 1883.
Not Arittilnpeiteii orbiadari.i, McCoy. Carb. Fos.o. of Irelaml. IS44.
tirh'wulnUis, " " " " "

Shell large, orbiculate, becoming Avider and (ilili([nc witli iiuc : Icnutli nml
height equal in small and nu'diniii individuals; in large specimens the height
is sometimes one-ninth greater than the longitmlinal diameter; basal and
lateral margins full and regularly rounded.

Left valve moderately convex; mnbonal region ample. Kight valve con-
cave, flat or slightly convex over the umbonal region.

Ilinge-line straight, central ; length in young shells ecpial to four-fifths or
five-sixths of the longitudinal diameter ; and in large specinu us the length
is sometimes not more than one-half the length of the valve.

Beak obtuse, slightly oblique to the hinge, not rising above it, situated
anterior to the middli' of the hinge-line, and to the centre of the valve.

Anterior ear of Id't \alve, in small shells, comparatively large, triangular,

LAMELLIBRANCHIATA. 43

limits not strongly defined ; margin straight or slightly concave ; extremity
acute-angular ; in older shells comparatively narrow, with an obtuse-angular
extremity. Anterior ear of the right valve defined by a sulcus, extending
to the extremity of the beak ; margin convex ; extremity rounded. Byssal
sinus scarcely indicated on the left valve, forming a deep, angular notch in
the right valve. Posterior ear large, broad-triangular; length about two-
thirds of the hinge-line ; margin concave ; extremity acute or right-angled
in small specimens, obtuse in larger individuals ; limits not defined.

Test thin, thickness nearly .3 mm., ornamented by about 80 rounded
radii, with broader concave interspaces, crossed by regular, sharp, elevated,
continuous, concentric, foliate expansions of the test, reaching an elevation
of about .6 mm. above the general surface. Usually the test shows only the
strong rays, with occasionally a reticulation (plate 4, fig. 8), where the con-
centric folds are only partially preserved. The figure cited represents also
the internal mould where the test has been wholly removed.

Ligamental area, in young shells, represented by a slight inflection of the
margin of the hinge with a very small longitudinal groove. In more mature
specimens this area is wider, the number and strength of the grooves
increasing, until they occupy a continuous space between the extremities of
the hinge-line, slightly bending outwards at the beak ; the inner ridges and
grooves do not extend the whole length of the area. Cartilage-pit and
muscular impressions not observed.

The original specimen of this species is 38 mm. high, 39 mm. long, hinge-
line about 30 mm. Another more nearly entire specimen is 35 mm. high,
37 mm. long, hinge-line 30 mm. The largest specimen observed shows a
height of 78 mm., with length nearly equal, and hinge-line 42 mm. In this
specimen the longest diameter is 85 mm., measured from a point on the
upper anterior margin to the lower posterior margin.

This species is distinguished by its form and surface markings. The
characters of surface distinguish it from L. Priamus and L. macrodontus, though
in form it bears some resemblance to the former ; and in the ligamental grooves
it is similar to the latter.

44 PALAEONTOLOGY OF NEW YORK.

Pterinopeden mborbicularis, in some of the younger specimens, resembles this
species in general aspect ; l)ut none of that species have shown a broad,
liganiental area, and tlie ears continue to increase witli the growth of the shell.

Formation and localities. In shales of the Hamilton group at Monteith's
Point, Canandaigua lake, Ontario county ; Moscow, Genesee and York, Liv-
ingston county ; and in the shale and Encrinal limestone, along Lake Erie
shore, Eighteen-Mile creek, Erie county, N. Y.

Lyriopecten intekradiatus.

I'LATK II, FIGS. 1-4; and PLATE LXXXII, FIG. 5.

Lyrivpiiien iiiterradiatits, Hall. Pal. N. Y.. vol. v, jit. 1. PlaU's ami Exiilanations : PI. 2, tigs. 1-4.

Jan., 1883.

Shell large, longitudinally very l)roadly elliptical ; transverse axis somewhat
oVjliqiie to the hinge-line; height about one-niuth less tliaii tlie length;
margins lull and regularly roumlcd.

\ idves about equal in dimensions. Left valvi- ilepressed, moderately
convex. Right valve Hat, or .slightly concave below, becoming convex
towards the beak.

Iliiiv;e-line straiiiht, cfutral to the body oi' the shell: leimtli less than two-
thirds the longitudinal diameter of the shell.

Beak of left valve obtuse, not prominent, directed forward, situated about
one-thiid tlie length of the hinge-line from the extremity of the anterior ear.
In the right valve the umbo is often flat, and the angle subtended by its
sides is acute, caused liy tlie deej) liyssal sinus.

Posterior ears narrow-triangular, distinguished from the gra<lually sloping
sides of the uiiilio by their flatness and finer markings ; margins concave;
extremities mucronate. Anterior ear <>{' the left valve .smaller, triangular;
margins c(mcave ; extremity rectangular. Anterior ear of the ri;:lit valve
convex, triangular, truncated at the extremity; separated tioiii the umbo by
a deep angular sulcus, and a broad longitudinal semi-elliptical byssal sinus,
which forms an indentation in the lateral outline of the body of the .shell.

Test of the left valve marked by about 40 strong rounded rays with

LAMELLIBRANCHIATA. 45

smaller intermediate implanted rays, crossed by fine, regular, elevated sharp
lines of growth, which at intervals are raised into lamellas, and appear in the
cast as strong transverse ridges crossing the radii. The turrows between the
radii are narrower than the rays. The regular alternation of the radiating
lines where seen is a very conspicuous feature. The right valve is marked
})>• more numerous and subdued rays, and their alternation is somewhat
obscure. The ears show fine radiating lines and stronger and more crowded
concentric striae.

The differences between the right and left valves, are the convexity, the
surface markings, and the deep byssal sinus of the right valve.

The characters of the interior are not known.

A medium-sized individual has a height of 47 mm., longitudinal diameter
54 mm., hinge-line 32 mm. A smaller specimen measures in height 35 mm.,
length 38 mm., hinge-line 24 mm.

The lai'gest specimen (imperfect) shows a height of 74 mm., and a length
of 88 mm.

In outline and general aspect this species closely resembles L. macrodontus
(plate 8, figs. 9, 10), but differs in the obliquity of the beak, wider anterior
ears, and more elevated and numerous rays. It differs from L. magnijicus in
its outline, larger anterior ears, longer hinge-line, and finer radii of the ears.

The anterior ears of this species, and also of L. solox and L. polydorus, are
smaller than in the species referred to Aviculopecten.

The specimens mostly preserve both valves in connection. A large specimen
(plate 82, fig. 5), occurring in the harder argillaceous sandstone, attains nearly
the dimensions of L. cymbahn (plate 24, fig. 8), but difliers conspicuously in the
more numerous, strong radii, their gentle curvature toward the anterior side,
and the smaller area of surface upon the anterior side of the vertical axis of
the valve.

Formation and locality. In the shales of the Hamilton group, Fultonham,
Schoharie county, N. Y.

4G PALJEONTOLOGY OF NEW YORK.

Lyriopkcten macrouontus.

IT.ATK IV. Fit;. ;p; AXii PI.ATK VIII, FIGS. 9, 10.

Li/rii'jiftteH viaemdiml lui. IIai.i.. Cut. Piila-ozoii: Fossils. S. A. MrLLKR. Cincinnati. 1S77.

Pill. N. Y., vol. V, i)t. 1. Plates anil Exi.Ianatidns : I'l. 4. lifr. !l ; ].l. 8,
tip<. 9, 10. Jan., 1883.

Shell liir<cc, siili-chculiii- ; in isoine large specimens becoming tran.sversely broatl-
ovato, t'nmi tlie posterior extension of the \alvv; height I'nuii one-sixth to
one-eighth less than the Icngtli ; margins regularly idiiiidcd. more convex at
the j)(i>tt riiir jati'ial margin, ami (■xtcnding in nearly a straight line to the
beak.

Left valve depressed, moderately convex. Right valve unknown.

Hinge-line straight, nearly central, varying in length with the age of the shell.

Beak obtuse, ronndetl. directed slightly toward the anterior, not rising
above the hinge.

Anterior ear small, about one-third tlu' length of the posterior, triangular,
not well-defined ; margin straight or slightly concave ; extremity obtuse.
Posterior ear large, triangular, defined liy the absence of the strong radii,
and liv a shallow, nndtdined depression reaching to the beak; margin deeply
sinuate ; extremity acuminate.

Surface marked l)y from 30 to 40 broad, rounded radii, with usually
smaller intermediate rays, crossed by fine striae of growth. Some fragments
of shell, nflhering to the internal mould, have a thickness of one millimeter.

Muscular impression large, sub-circular, concentrically striated, situated
posterior to, and below the umbonal region. Cartilage-pit very small, trian-
gular bene.ath the apex of the beak, not extending to the hinge margin.
Ligamental area usually marked by five strong, elevated ridges, which curve
outward at the beak, diverging from, and ]>artially enclosing, the cartilage-
pit, and continuing toward the extremities of the ears; the innermost ridges
disappear before reaching the extremity of the area.

'file largest specimen is S-"") mm. liigh, !tS mm. long, and tlie liiuge-line
50 mm. Another specimen, somewhat diflerent in |ir(i|i(irtions, is liS mm. in
hei'_dit. 7-') mm. loni:'. with irnu:c-line of 40 mm.

LAMELLIBRANCHIATA. 47

Compared with L. magnificus, this species has greater convexity, less elevated
radii, and, in general, a comparatively greater longitudinal diameter. It differs
from L. cymbalon and L. tricostatus in surface ornamentation.

This species, described from only the left valve, is nevertheless so distinctly
unlike any others here described that it is readily recognized.

Formation and localities. In the coarse beds of the Hamilton group, at Ham-
ilton, Madison county ; and Worcester, Otsego county, N. Y.

Lyriopecten cymbalon.

PLATE 'SXIV, FIG. S.
Lyi-itypecten i-ymbaloit. Hall. Pal. N. Y., vol. v, pt. .5. Plutes an<l Explanations: PI. 24, tig-. 8. Jan., 1883.

Shell large, sub-orbicular, not oljlique ; height a little less than the longitudinal
diameter ; pallial margin regularly rounded, upper anterior margin more
inflated than the posterior, which is truncated toward the beak.

Left valve regularly convex ; the basal margin slightly inflected, giving
the valve an undue convexity. Right valve not known.

Hinge-line straight, length a little greater than one-half the longitudinal
diameter of the shell, and extending about one-third of its length farther to
the posterior than to the anterior margin.

Beak obtuse, rounded, straight, central ; umbonal region defined by its
al^rupt antero- and post-cardinal margins, and hy its convexity.

Anterior ear very small, narrow-triangular ; margin concave ; extremity
obtuse-angular ; l>yssal notch broad and shallow, not conspicuous. Posterior
ear large, triangular, marked ))y a deep sinus ; margin convex ; extremity
angular ; length twice as great as the anterior ear.

Test marked by about twelve very strong, continuous, broad, rounded
rays, with from one to six smaller ones of variable strength in each of the
flat interspaces ; crossed by fine, sharp, regular, concentric striae of growth,
which are elevated into lamellar ridges at irregular intervals. The ears and
a broad adjacent space on the body of the valve are destitute of rays, but
show strong strite and undulations of growth. The direction and character

48 PALAEONTOLOGY OF NEW YORK.

of tlic ravs (ill tin- si)friiiR'ii lij^ured) have been affected, apparently, by some
iiijiiiv rcceivcMl (hiring the life of the animal, which has also pioihiced a
strong varix of growth.

Li«'amental area l.'> iiiin. widi- at tlie ))eak, whence it diminishes towards
the extremities of tlie hinge-line, marked by several Hat, longitudinal striai.
Cartilage-pit broa<l-triangular, situated under the apex.

The .><pecimen described is 7") mm. in lieiglit, SS mm. in longitudinal
diameter, and hinge-line -Iti mm. The distance between tlie centres of two
of tlie larL^' ravs at tlie Ijasal margin is about 17 mm.

The surface markings resemble L. tricostatus, but they are stronger, more
rugose, and the rays less numerous; also the shell is not oblique, and the tjeak
is moi'e obtn.se and roumleil. It differs from L. macrodontus and L. magnificus
in its greater convexity, deepiM' byssal sinus, larger posterior ear, and by its
surface characters. This remarkably large and fine species shows conspicu-
ously the diminished anterior ear, a feature also seen in L. tricosiaim, which is
the reverse of many species of recent Pectenidse, where the anterior ears are
developed beyond the posterior; as in Janira longicauda (d'Orbignv), and Peden
Tranquebaricm (Gmrijn).

This species, although seen in only oiu' valve, is characterized by its peculiar
surface markings and outline.

Formation and locality. Hamilton grouj), from a liowldei' found near Elmiia.
N. Y.

LVRIOPECTEN TRICOSTATUS.

PLATE IV. KIG. n ; l'I..VrE VM, KK; Ji; ; ami I'l. AlK \, KI(;s. (Hi.

Avii-iila Ir'niiMila, V.\.\r.\K.M. (iodhijf. Siirv. N. V. : Rcpoit of Thii-il Uist., p. 179, fi),'. 1. 1843.
Lyriiijmteu trUnnUttuJi (Vanuxb.m), Hall. Pal. N. Y., vol. v, jif. 1. Plates ami Explanations: PI. 4, fifr. H ;

jil. 7. tifT. 2(i ; ])1. 10, Hp). 0-12. Jan., 18S3.

Shem, large, transverselv and more or less ol)liquely broad-ovate; height
usually less than the length, tlie ]iro})ortions varying with the age of the
.'<hell ; y(mng specimens are longitudinally elliptical ; iiuiture specimens are
more obli(jue ; while some abnormal foi'ins show a difl'erence in the direction

LAMELLIBRANCHIATA. 49

of the transverse diameter of nearly 45°; margins full, rounded anteriorly,
extended on the postero-basal side, and thence following a nearly straight
line to the beak.

Valves similar in general outline. Right valve tiat or slightly concave.
Left valve moderately convex.

Hinge-line straight, central, varying from more than one-half the longi-
tudinal diameter in young specimens, to less than one-half in mature
examples.

Beak pointed, depressed, directed forward, situated anterior to the middle
of the hinge-line, and not extending as far as the margin of the hinge.
Umbonal angle 90°.

Anterior ear small, triangular, usually less than half the length of the
posterior one ; margin rounded ; extremity obtuse ; byssal sinus broad,
rounded, indenting the b(jdy of the shell, and shortening the anterior ear.
In the right valve the notch is deeper and more angular. Posterior ear
large, flat, triangular, marked by a distinct sinus which increases with the
age of the shell ; margin above the sinus straight, convex or concave ;
extremity angular. In young specimens the ears are sub-equal, undefined,
and without sinus. In older shells the ;interior ear becomes diminished, or
appears comparatively smaller ; while the posterior ear is increased in size.

Surface ornamented by fi'om 20 to 25 strong, rounded, contiiiuous rays,
with broad, flat interspaces whicli show from three to ten smaller radii ; and
in well-preserved specimens the entire surface of the shell is marked by fine,
regular, sharp, elevated, continuous, concentric lines of growth. In the right
valve the finer radiating lines are conspicuous, while the others are obscure
and more numerous. The ears do not show the stronger rays, but usually
preserve the finer radiating and concentric lines, and are marked by regular,
concentric undulations, which are not seen on the body of the valves. The
thickness of the test is not known.

The hinge-ligament, in mature specimens, has a width of about 2 mm.,
and is marked with from four to seven longitudinal, raised lines, or liga-
7

50 PALjEONTOLOGY of new YORK.

mental fjrooves, diverginjj; from the rartiln^c-pit, and contimuu^ parallel to
tlu' hinge-line ; cartilage-pit small, triangular, placed heneatli the heak.

Tiie largest specimen yet seen, of the left valve, is 80 mm. in height, 88 mm.
in length, and the hinge-line 35 mm. ; the distance between the strong rays
at the l)asal margin is 11 nmi. A specimen of medium size is (12 mm. in
height, 72 mm. in length, hinge-line 3U iiiiii. A yoimg iiulividual is 2o
mm. ill height, 2(1 mm. in length, and hinge-line 18 mm.

This .species somewhat resembles in outline L. macrodontus, but differs in the
surface markings, and the finer parallel teetli of the ligamental area. It differs
fniiu L. magnifictis, L. interradiatus, and L. cymbalon in outline; the surface of
the latter species is similar, but more rugose. From L. Priamus it differs in
fnriii and surface markings.

lu comparing many specimens a great diversity in form and ornamentation
will be observed.

Formation and localities. In the lower and middle Chemung beds at Barker,
Broome county; Big Flats, Chemung Narrows, and Elmira, ('liemnng county;
and Franklin, Delaware county, N. Y.

Lyiuopecten Polydorus.

rr.ATK VII, FIG il.
Lyriipecteit P'ily:li)riu), ll\LL. I'jil. N. V., vol. \ , jit. 1 l'l;it<'s jiml Rxplanatioiis : I'l. 7, ti;;-. 2"). Jan., 1SS3.

Shell of medium size ; transversely very broad-obovate ; height nearly equal-
ling the longitudinal diameter; pallial margins full, regularly rounded on
the posterior side ; and the anterior side of the left valve passing in nearly
a straight line to the beak.

Left valve depressed, nearly Hat. Right valve unknown.

Hinge-line straight, length ei|ual to two-thirds the length of the shell,
extending posteriorly nearly as far as the posterior margin of the shell.

Beak pointed, directed fnrwaiil. central to the boil\ of the shell, and

forward ol" the middle of the liinge-line, rising a little aliove it. I'liil al

anyle more than '.Ml°.

LAMELLIBRANCHIATA. 51

Posterior ear narrow-triangular, one-third longer than the anterior,
the limits not well-defined, and it appears as an expansion or extension of
the posterior side of the umbo ; margin concave ; extremity mucronate.
Anterior ear short-triangular ; margin convex ; extremity rounded, separated
from the umljo by a deep, rounded sulcus, which corresponds to the byssal
sinus.

Test ornamented by about 25 irregular, strong, rounded rays, with wider
interspaces, marked by two or three smaller lines in each one, and crossed
by fine strias of growth. The surface markings extend over the ears.

Interior not observed.

The valve described is 28 mm. high, and of about the same length, and
the hinge-line 18 mm. The length of the posterior ear is 11 mm., and of
the anterior ear 7 mm.

This species bears some resemblance to L. solox, but differs in the flatness of
the valve and less gibbous umbo. In surface character it is similar to L.
tricostatus, but has fewer intermediate striae between the stronger rays, which
in that species are more simple and rounded ; while in other characteristics
they are very unlike.

Formation and locality. In argillo-arenaceous slates of the Chemung group
near Cassadaga, Chautauqua county, N. Y.

Lyriopecten magnificus.

PLATE Vni, FIG. S.
Lyrhipecteii magnifies, Hall. P;il. N. V., vol. v, pt. 1. Plates and Exiilaiiations: PI. 8, tig. S. Jan., 1S83.

Shell very large, nearly circular ; height a little less than the longitudinal
diameter ; basal and lateral margins regularly rounded.

Left valve nearly flat ; the greatest convexity is in the centre of the umbo-
nal region. Right valve unknown.

Hinge-line short, straight, length less than one-half the transverse diameter

52 PAL/EONTOLOGY OF NEW YORK.

oz

(if till' valvo, cxtt'iiiliiiji I'artluT toward iIk- posterior than toward tlu-
anterior inarfiin.

Beak ol)tiisi'. rounded, central to tlie l)ody of the .<licll, (k-pressed, not
rishij; al)ove tlie liiiij:e-hne, nor extending to tin- hinge-margin; undional
region moderately convex, not delined laterally.

Anterior ear small, narrow-triangular, not wi-U-di-dned ; extremity very
ohtuse, roundeil : margin slightly concave without a (k'ri(le<l hyssal sinus.
Posterior ear triangular, more than twice the length of the anterior, and defined
fnjm the nmhonal slope by the absence of the strong radii ; extremity acute-
angular; margin marked by a broad, rounded sinus.

Test marked by about 40 strong, elevated rays, which aie somewhat
tiattened along their summits; usually alternating with one or two sharp or
rounded rays, crosseil by wry line, sharp, concentric stria?. The radii
gradually diminish in strength towards the ears, where they are represented
hy elevated, narrow lines.

Litramental area inarkcil l>v several longitudinal strise. Other interim-
characters not known.

The height of the specimen is ".17 mm., length 104 mm., liinge-liiu' 44 mm.
Three of the stronger rays occupy a space of 12 mm. at the liasal margin.

The specimen described is thi' imprt'ssion of the exterior of a left valve; it is
quite characteristic and very distinct from other known species in its form and
surface markings.

Ill ornamentation and general outlini' there is sonu' resemlilance lietween this
shell and L. macrodontus, but it is h'ss convex, the rays are more (4evate(l, and
more sharply defineil. The geological horizons of the two species are also
widely separated.

Formation and localiti/. In coarse, arenaceous slates of the F])]ier Chemung
group, at Montrose, Suscpiehaiiua county, Peini.

LAMEIJJBRANCHIATA. 53

Lyriopecten anomi^formis.
plate iv, fig. 10 ; plate x, fig. 5 ; and plate lxxxii, fig. 2.

Lyriopecten mwtmwformis. Hail. MSS. foi- vol. v, pt. 1. 1877.

" " " Catalogue Amer. Palaeozoic Fossils, S. A. Miller. 1877.

" " P'l'- N. Y., vol. V, lit. 1. Plates and Explanations ; PI. 4, tig. 10 ; pi. 10,

tifr. ^. Jan., 1883.

Shell larger than medium .size, obliquely elliptical or obovate; height nearly
equal to the length ; the transverse axis makes an angle of about 45° with
the hinge-line; margins regularly rounded anteriorly and along the base,
becoming obscurely truncated on the upper postero-lateral portion of the
shell.

Left valve slightly convex. Right valve nearly flat.

Hinge-line straight, anterior; length equal to one-half the transverse
diameter of the shell.

Beak of left valve obtuse, rounded, oblique, not well-defined, situated
anterior to the middle of the hinge, and extending to the hinge-margin, but
not rising above it. Beak of right valve scarcely defined.

Anterior ear small, obscure, only indicated by the short portion of the
ligamental area anterior to the beak. Posterior ear undefined, triangular ;
margin straight ; extremity obtuse. Byssal sinus in the left valve a small
notch ; in the right valve a very deep, elliptical sinus.

Test thin, marked on the left valve by numerous fine, thread-like radii,
of which every fourth to eighth one is much stronger than the intermediate
lines, crossed by fine striae of growth ; the larger rays are about 20 in
number. On the right valve the radii are represented by obscure, undu-
lating, unequal striaj. The ears show the same surfiice markings.

Cartilage-pit small. Ijigamental area thickened, with about eight flat,
longitudinal lines extending to the extremities of the hinge.

A left valve measures 62 mm. from the anterior ear to the postero-basal
margin ; from the extremity of the beak the height is 55 mm., and the
length, parallel to the hinge, is about 54 mm. ; hinge-line 27 mm.

:,4 J>ALA:oMVLOGY of new YORK.

The right valve is imperfect, but appears to have been iiiDrc einiilai- in
oiitliiH' tli;m tlu' left.

This species is characterized by its form, smrface ornamenta,tion, and marked
resemblance between its right valve and the lower valves of some species of
the recent genus Anomia, in the tlatness of the valve and deep byssal sinus.

Formation and locality. In the slates of the Chemung group, at Chemung
Narrows, Chemung county, N. Y.

LVRIOPECTEN PrIAMUS.

PLATE X, FIGS. 1, l.

Lyriopecten PriatHii.'', U.KJA.. Pal. N. V.. vul. v, i>t. 1. Plates and Explanations : PI. 10, tigs. 1, 2. Jan.. 1883.

Shell large, transversely bromlly elliptical or ovate, wider below ; transverse
axis niiriiial or very slightly oliliiiuc tn tlic liinge-line; height less tliaii one-
tenth greater than the Idiiuitmliiial diameter; margins regularly rounded.

Left valve moderately and symmetrically convex. Right valve unknown.

Hinge-line straight, sub-central ; length about one-half the longitudinal
diameter of the .shell.

Beak obtuse, rounded, oblique, anterior lo the transver.se axis, not rising-
above nor extending as far as the hinge-margin.

Anterior ear small and undefined. Posterior ear bruail-triangular, Hat;
margin concave ; extremity angular. Byssal sinus not defined.

Test marked liy abnut 10 strong, rounde(|. irregular radii witli narrow
interspaces, crossed by fine stritB of growth. Tlie rays are often composed
of ftiscicles of thread-like striaj, and bifurcate at some point of their length.
On the posterior ear the rays are subdued and finer.

Ligamental area 2.5 mm. wide in mature specimens, and marked by
numerous sharp, elevated, parallel, longitudinal stria> extending to the
extremities of the hinge-line. Cartilage-pit triangular, narrow, situated at
the apex of the beak, an<l extending to the margin of the hinge.

One large specimen, which is a cast of the interior, measures 7:^ mm. in
height, 7(J mm. in length; hinge-line 32 mm. A smaller specimen, showing

LAMELLIBRANCHIATA. 55

the exterior, is 63 mm. in height, 57 mm. in longitudinal diameter, aud
hinge-line about 31 mm.

In general appearance of surface this shell is similar to L. macrodontus, but
the details are quite different.

This species, though characterized from the left valve only, is distinctly
different from the others in form and surface ornamentation.

Formation and locality. Associated with numerous segments of crinoidal
columns, and rarely with any other fossils, in the upper part of the Chemung
group, at Franklin, Delaware county, N. Y.

Lyriopecten fasciatus.

PLATE IX, FIGS. 10, 11.

Permipeclen fasciculaUis, Hall. MS., vol. v, pt. 1. 1877.

" " " Catalogue Amer. Palaeozoic Fossils, Miller, p. 200. 1877.

Not Aviculiypecteu fascietilatus. Hall.

Lyriopecten fasr-iatufi. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 9, tigs. 10, 11.

Jan., 1883.

Shell of medium size, very broadly ovate, erect ; length a little less than the
width ; margins regularly rounded.

Right valve convex, the greatest convexity one-third the width of the
valve from the beak. Left valve unknown.

Hinge-line short, straight.

Beak acute, erect, prominent ; umbonal region distinctly defined, sub-
tending a right angle.

Anterior ear small, sctircely defined, about half the length of the posterior
one. Posterior ear triangular, defined by a well-marked sulcus ; margin
nearly straight ; extremity obtuse. Byssal sinus shallow.

Surface ornamented by strong, low, broad, rounded radii, which increase
by interstitial addition ; and numerous sharp, elevated, radiating striae mark
the surfaces of the rays, giving them a distinctly fasciculated aspect. These
also mark the interspaces, which are narrower than the large rays. Sharp,
regular, concentric striae cancellate the radii. The ears are marked only by
the concentric striae, which are less prominent than on the body of the valve.

56 PALAEONTOLOGY OF NEW YORK.

liitrrnal fliaractfi> nut known.

The specimen described, is a rijrlit vahc liaviiij; a length ul' ;i4 mm.,
heif^ht 8(i nnn., and liinge-line about I'l mm.

In outline and siu-f'ace characters this species resembles L. Priamus, but the
valve is more convex than the specimen referred to the right valve of that
species : it is also less oblicpie, and the beak more elevated and erect. The
rays of L. Priamus are distinctly and frequently bifurcating, while in this
species the fasciculate appearance is due to the sharp, elevated stria.' upon the
stronger rays.

Formation and locality. Chemung group, Leon, Cattaraugus county, N. Y.

Lykiopecten solox.

PLATE X.XIV, FIU. 5.
LyrUtptcten solox, H.\i.i.. Pal. N. Y., vol. v, i>l. 1. Plates and Explanations: PI. 24, fig'. 5. Jan., 1883.

SiiKi.i, of medium size, nearly circular; transverse axis not inclined to tlie hinge-
line ; margin regularly rounded, and sloping somewhat abruptly into the
Ijyssal sinus.

Right valve moderately convex. Left valve unknown.

Hinge-line straight, Icimtli about one-lialf the diameter of tlie shell,
extending farther on the anterior side.

Beak obtuse, rounded, central, not rising above the hinge-liuc, directed
slightly forward ; um])0 ample.

Po.sterior ear triangular, defined by its llattened surface, ami the rapid
umbonal slope ; margin concave ; extremity rectangular. Anterior ear
imperfect, l)ut showing a very deep and narrow byssal sinus.

Test marked by numerous fine, angular rays, which are arranged in a])out
4(1 regular, rounded plications, comiiosed of fascicles of liner rays, with
defined inter.spaces. Finer obscure rays mark the umbo, and the posterior
ear shows three or four rounded undulations witli lines of growth.

Literior not known, except the ligainental area, which is narrow, and
nuikes an inflection of the hinge-margin of the ears.

LAMELLIBRANCHIATA. 57

The dimensions of the right valve described are as follows : height 43 mm.,
longitudinal diameter 42 mm., and hinge-line apparently about 25 mm.

This species differs from L. Pobjdorus by its circular outline, convexity, obtuse
beak, ample umbo and surface characters. _ It difters from L. magnificus and
L. macrodontus in the greater convexity of the valve and fullness of the umbo,
as well as in the character of the rays. It is also much smaller than those
species.

Formation and locality. In a fine semi-calcareous, argillaceous sandstone
(lying above the conglomerate ?) of the Upper Chemung group, near Panama,
Chautauqua county, N. Y.

PTERINOPECTEN, Hall.

Pterinopecten multiradiatus.

PLATE I, FIGS, (i, 7.

Pterhidpecteii iimltiradiatu,<i, Hall. Pal. N. Y., vol. v, jit. 1. Plates and Explanalioii.s : PI. 1, hgs. 6, 7.

■Jan., 1888.

Shell large, rhomboidal, body of the valve longitudinally obovate ; length and
height nearly as five to four ; anterior and basal margins regularly curved,
the postero-basal margin produced and the body of the shell extending
thence in a direct line to the beak.

Left valve moderately and regularly convex. Right valve unknown.

Hinge-line straight, anterior, less than the length of the shell.

Beak obtuse, rounded, directed forward, slightly rising above the hinge.
Umbonal region ample, subtending an angle of about 105°.

Ears triangular, flat, moderately well-defined ; margins slightly concave ;
extremities rectangular. Posterior ear about twice the size of the anterior,
limited by a stronger ray and the abrupt post-cardinal slope of the valve.
The anterior ear is limited by a distinct but undefined sulcus. Byssal sinus
scarcely marked.
8

58 PALEONTOLOGY OF NEW YORK.

SiirfiR'L' oniaiiK'nkHl by numerous strong, distant, elevated, rounded ra^s,
with interspaces marked by a strong ray in the centre, and several finer
ones on each side, producing two series of alternations. Concentric striae
obscure. The arrangement of the rays gives the surface a fasciculate aspect,
especially marked in the impression of the exterior. The rays on the pos-
terior ear are sharp and simiilc, wliile on the anterior ear they are similar to
those on the body of the shell.

Interior not observed.

The specimen has a length of 48 iinn.. height 35 mm., hinge-line about
36 mm.

This species is distinguished from P. suborbicularis by its greater length ami
doubly alternating radii. Though somewhat similar in form to P. crenicostatus,
the surface characters are very different.

Formation and locality. In Coruiferous limestone at Stafford, Genesee county,
N. Y.

Pterinopecten reflexus, n. sp.

IT.ATK f-XXXII, FIG. 8.

Shell of medium size, rhomboidal, moderately oblique ; length one-sixth
greater tliau the height; outline regularly curved to the postero-basal mar-
gin, thence extending posteriorly.

Left valve depressed-convex ; mai'gin reflexed. Right valve unknown.

Hinge-line straight, extended posteriorly, exceeding the greatest length of
the shell.

Beak obtuse, low, rounded, diiected forward. Umbonal region convex,
sul)tending an obtuse angle.

Posterior ear large, flat, triaugular, scarcely defined from the umlu); mar-
gin slightly convex ; extremity obtuse. Anterior ear small, triangular, con-
vex, limited by an undefined sulcus and a shallow byssal sinus; margin
nearly straight ; extremity obtuse.

Test marked by fine, rounded striae, alternating with finer lines ; inter-
mediate spaces flat. The same surface marking continues in a subdued

LAMELLIBRANCHIATA. 59

degree upon the posterior ear, and somewhat more strongly on the anterior
slope and anterior ear.

Internal characters unknown.

The specimen figured has a length, across the middle, of 18 nnn., height
15 mm., hinge-line 22.5 mm.

In form, this species resembles P. Hermes, but is distinct in its smaller and
less defined anterior ear, less strong radii, and more depressed beak. It is
much flatter and of difierent proportions from P. exfoliatus.

Formation and locality. In the Corniferous limestone at the Falls of the Ohio,
near Louisville, Ky.

Pterinopecten insons.

PLATE I, FIG. 4.
Pterinopecten insona. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 1, tig. 4. Jan., 1883.

Shell small, rhomboidal, slightly oblique ; length somewhat greater than the
height ; basal margin regularly rounded ; the anterior and posterior sides
become nearly vertical as they approach the ears.

Left valve convex, the greatest convexity near the beak. Right valve
unknown.

Hinge-line straight, length one-fourth greater than the length of the shell,
extended posteriorly.

Beak acute, prominent, anterior to the middle of the hinge, directed for-
ward. Umbonal region prominent, subtending a right angle.

Ears triangular ; margins straight ; extremities acute. Posterior ear large,
undefined. Anterior ear small, convex, with an undefined fold below the
cardinal margin, limited by a distinct rounded sulcus. Byssal sinus slightly
marked.

Test (in a partially exfoliated specimen) marked by regular, sharp, not
numerous rays, with broad, flat interspaces, which, in a perfect condition,
have probably been marked by fine striae. The rays are obsolete over the
posterior slope of the valve and the umbo, and also not preserved on either
of the ears.

60 PALAEONTOLOGY OF NEW YORK.

Interior not observed. Ligamental area narrow, appearing as a simple fold
of the hinge-margin.

The specimen has a length of 18 mm., height 11 mm., hinge-line Ifi.o mm.

in some of the modes of occurrence, this species resembles P. exfoliatus, but
differs in its proportionally longer hinge-line, more extended posterior ear,
(•ompai;iti\ el\- larger anterior ear, and the greatest convexity is nearer the beak.

Formation and locality. Upper TlddertxTg limestone, Western New York.
Tlie particular locality unknown.

Pterinopecten nodosus, n. sj).

PL.VTE LXXXn, FIG. 13.

Shell small, sub-rhomboidal, slightly oblique ; form not fully known.

Left valve very convex.

Beak prominent, nearly erect. Umbonal region very prominent, the limits
distinct on the anti-rior and obscure on the posterior side ; subtending an
acute angle.

Posterior ear large, triangular; margin very slightly concave; extremity
angular. Anterior ear not preserved in the specimen.

Test thin, marked (in a partially exfoliated specimen) by strong, rounded
rays with intermediate finer ones, and fine, concentric', undulating, elevated
striie, witli numerous concentric undulations, which increase in frequency
from the beak to the margin, and on crossing the larger rays, are elevated
into strong nodes. On the posterior ear the rays are fine, equal and con-
tinuous.

Interior characters unknown.

This species is described from an imperfect specimen of tlic left valve: l)ut
it is so remarkable in its nodose umlulations tlmt it is readily distinguished
from every other form.

Formation and locality. In the Corniferous limestone at the Falls of the
Ohio, near Louisville, Ky.

LAMELLIBRANCHIATA. 61

Pterinopecten exfoliatus.

PLATE I, FIGS. 16, 17 ; ANU PLATE LXXXIII, FIGS. 6, 7.

Pterlnnpedeii ejcftillatiiji. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanatidii.^ : PI. 1, tig-.«. 16. 17.

Jan., 1883.

Shell of less than medium size, sub-rhomboidal ; body obliquely ovate ; length
somewhat greater than the height ; pallial margins regularly rounded from
the anterior ear to the base of the posterior slope, from whence the margin
is nearly straight or slightly concave to the extremity of the hinge.

Left valve very convex, inclined to gibbosity. Right valve moderately
convex, much smaller than the left.

Hinge-line straight, a little longer than the greatest length of the shell,
extended posteriorly.

Beak of left valve prominent, sub-acute, anterior to the middle of, and
arching over the hinge-line, directed forward. Umbo prominent, gibbous,
the greatest convexity being about the middle of the width, subtending a
right angle.

Ears triangular. Posterior ear large, undefined ; margin slightly con-
cave ; extremity somewhat acute. Anterior ear small, convex, defined by a
deep, obtuse sulcus ; margin convex ; extremity acutely rounded. Byssal sinus
distinct, somewhat deep.

Test thin ; marked in the left valve l)y fine, regular, radiating striae with
flat interspaces which show one or two finer rays ; crossed by concentric
lines of growth and stronger undulations, which in old shells become very
prominent. The rays are continued over the ears, and are somewhat sub-
dued and less distinctly alternating on the posterior ears, and obsolete over
the upper part of the uml^o. The right valve is marked by obsolescent rays
and concentric undulations.

Ligamental area narrow.

Three specimens measure respectively as follows: Length 17, 20 and 22
mm., height 15, 18 and 18 mm., length of hinge-line 18, 21 and 23 mm.

In the exfoliated condition, this species resembles P. insms ; but has a com-
paratively shorter hinge-line, smaller anterior ear, deeper byssal sinus, and less

62 PALEONTOLOGY OF NEW YORK.

(.■xti-mli'il posti'iior oiir. It is iiiore' ^ibhous and l(j.s.s oblique than P. Hermes,
with less conspicuous stria\

The specimens are usually in tlie condition of partially exfoliated casts, and
retain marks of only the stronger radii ami concentric undulations. The
diflerences Ix'twei ii tlic internal mould and the impression of the exterior
of the shell are represented in figs. 6, 7, ^A' pi. Ixxxiii. This species is not
uncommon in the central and western portions of the State.

Formation and hcalities. Tn a limestone bed of the Marcellus shale at Avon,
Livingston county, Staflord, (Jenesee county, and A^ienna, Ontario county,
N. Y.

Pterixopecten dignatus.

I'l.ATE I, FIGS 12, 14, Ifi.

Pterinopecten diffnatiis. Hall. Pal. N. Y., vol. v, pt. 1. Platos and Explanations: PI. 1, fijrs. 12. 14, 1.5.

Jan., 1883.

SiiEi.i, small, sub-rhomlM)idal, very .slightly oblique; length and height as three
to four ; pallial margins regularly rounded, somewhat more produced on the
postero-lateral portion.

Left valve moderately convex. Right valve depressed, flatter and smaller
than the left : it diiVi'is in surface markings and depth of byssal notch, and
is apparently thinner and more delicate.

Hinge-line straight, length equalling, or greater than, the greatest length
of the shell, extending anteriorly beyond the margin of the valve.

Beaks obtuse, rounded, anterior to the centre of the hinge-line, directed
slightly forward. Umbonal region ample, subtending an acute angle.

Ears triangular, flat. The posterior ear larger and less distinctly defined
than the anterior ; margin straight or .slightly concave; extremity rectangular.
Anterior ear rounded ; margin convex ; extremity acute-angular. Byssal sinus
moderate in the left valve; dee]!, ii.in-ow and angular in the right valve.

Test of the left \alve marked In numerous strong, rounded, increasing
radii, witli l)roader interspaces, containing one or two smaller rays which
originate about the middle of the valve; crossed l)y fine, sharply elevated,
concentric striie. The right valve is marked l)y fnie, sub-eciual, regular.

LAMELLIBRANCHIATA. 63

radiating striae, which increase by interstitial addition, and become obsolete
on the npper part of the umba The radii are also seen on the ears.

Internal characters not observed.

The largest specimen has a length of 19 mm., height 15 nun., hinge-line
19 mm. Another specimen measures 17 mm. in length, 14 mm. in height,
with the hinge-line 18.5 mm.

This species closely resembles P. l&tus, but differs in being less oblique, with
greater height, more acute beak, fewer and stronger radii, and a characteristic
concentric marking. From P. Hermes it difiers in being less oblique, with the
posterior ear less extended, and with finer rays upon the ears. From P. con-
spectus it difters in its greater length, and distinctly different surface markings
of the left valve.

Formation and locality. In the Marcellus shale at Bloomfield, Ontario
county, N. Y.

PtERINOPECTEN LiETUS, n. sp.

PLATE I, FIG. l:!.

Plerinopecten laiitas (in cn-dr), Hali,. P:il. N. Y., vtil. v, )]t. 1. Plates and Exiilanations : PI. I, tiff. 13.

.Ian., 18S3.

Shell small, sul^-rhomboidal, regularly rounded ; length one-sixth less than the
height.

Left valve depressed-convex. Right valve unknown.

Hinge-line straight, longer than the greatest length of the valve, extended
anteriorly beyond the margin of the shell.

Beak obtuse, anterior to the middle, directed forward, not prominent.
Umbonal region scarcely defined, subtending about a right angle.

Ears unequal, triangular. Posterior ear much the larger, undefined ; mar-
gin very slightly concave ; extremity rectangular. Anterior ear smaller,
not distinctly defined from the 1jody of the shell ; margin above the sinus
convex ; extremity acute. Byssal sinus moderate.

Entire surface marked l)y distinct, close, rounded, duplicating radii, crossed
by fine, concentric lines of growth. The surface of the umbonal region is

04 PALEONTOLOGY OF NEW YORK.

wrinkled fntiii the apex to below the middle of the vulve. The surface
iiiiirkings are finer and sub-e(iual over the posterior ear. A small sjiace on
the umbo, as in Aviculopeden bellus, is destitute of radii.
Internal characters not known.

This species dillers from P. Hermes in its less oblique I'orm, shorter liiniie-
line, less ample umbo, and in having no regular alternation in the ra^s, which
are closer and more rounded. It is associated with, and closely allied to, P. dig-
natus, but dillers by its more obtuse beak, longer outline, and comparatively
more frequent and smaller rays, witiiout tlie regular concentric striag.

Formation and locality. In the Marcellus shale at Bloomlidd, Ontario
county. N. Y.

Pterinopecten Hermes.

IT.ATE XVII, FUJS. l:t-15.

Ptfrinnptiltn Htniie.i. Ham,. Pal. N. V.. vol. v, pt. 1. Plates and Explanations: PI. 17. liys. 13-15.

.Ian., 1883.

SiiKLi. less than medium size, sub-rhomboidal, obliquely sub-ovate; length and
height about as three to four ; pallial margins regularly rounded, becoming
straight on the post-cardinal slope at the junction with the ear.

Left valve moderately convex. Right valve not determined.

Beak acute, prominent, iintcrior to the middle ol' tlir slidl (liiectcd tin ward.
Umbonal region ninplf, subtending an angle of al)Out 80°.

Ears very uueijual, triangular. Posterior ear much the larger, scarcely
defined ; margin concave ; extremity acute. Anterior ear small, slightly
C(mvex, defined by a distinct sulcus ; margin convex ; extremity rounded.
Byssal sinus deep.

Test marked by regular, rounded stria\ with wider interspaces which, on
the posterior part of the valve, show finer intermediate rays. The ears
have essentially the same surface characters as the body of the valve. The
entire surface is marked b\ fine ccmcentric stria*. Umbo with concentric
wrinkles. Partial casts of the interior sliow the same characters as the
exterior, liut show no iiuisculiir or pallinl iiiaikings.

LAMELLIBRANCHIATA. 65

The largest specimen has a length of 19 mm., height 29 mm., hinge-line
29 mm.

This species is very similar in form to P. Icztus ; but the hinge-line is pro-
portionally longer and the radii stronger and more distinctly alternating. It
differs from P. dignatus in its more oblique form, proportionally greater diameter
and sharper radii. From P. conspectus it differs in being much more oblique in
outline and comparatively narrower.

Formation and locality. Tn shales of the Hamilton group, Ontario county, N. Y.

Pterinopecten spondylus.

PLATE XVn, FIU. Ki.

Pterinopecten spondyliis. Hall. Pal. N. Y., vol. v, jit. 1. Plates and Explanation.? : PI. 17, fig-. 16.

Jan., 1883.

Shell small, sub-rhomboidal, scarcely oblique ; body of the shell ovate ; length
somewhat greater than the height ; pallial margins regularly rounded, be-
coming straight on the posterior slope, which is continuous with the margin
of the ear.

Left valve convex. Right valve not known.

Hinge-line straight, length greater than the longitudinal diameter of the
shell, extended anteriorly.

Beak obtuse, rounded, directed forward, situated anterior to the middle
of the hinge-line. Umljonal region prominent, but not strongly defined on
the posterior slope ; subtending an acute angle.

Ears broad, triangular, flat. Posterior ear much the larger, scarcely
defined ; margin slightly concave ; extremity rectangular. Anterior ear
defined by a distinct sulcus ; margin convex ; extremity rounded. Byssal
sinus shallow.

Test marked by regular, sharp elevated rays, with broader interspaces
which are marked by -finer rays, and concentric foliate lamellae of growth,
which are bent backward in crossing the rays, forming short semi-tubular

y

G»i PALEONTOLOGY OF NEW YORK.

spines. The radii are less conspiouons on tlie ears, wliidi also show a few
concentric undulations.

Internal characters not preserved. The liganiental area appeart> as a
simple fold in the hinge.

The specimen has a length of 15 mm. ; height 13.5 mm. ; hinge-line
18 mm.

This .species has the general form and aspect of P. Hermes and P. latus. hut
is proportiomilly wider, with different and characteristic surface markings.

Formation and locality. In soft shales of the upper part of the Hamilton
group, shore of Canandaigua lake, Ontario county, N. Y.

Pterinopecten conspectus.

PLATE XVII, FIGS. 17, IS, 20, il.

Ptj-riiu>petten votutptctiui. Hall. Pal. N. V., vdI. v, \A. 1. Plates ami Kxplanations : PI. 17, fifrs. 17-21.

Jan., 1883.

Shell of medium size, siih-rhom))()idal ; moderately <)l>li(|nc in young shells,
scarcc'ly oliliijuf in oMcr oiu's : length ami height ahout cnual, the U-ngth
usually a little greater; j^allial margins regularly rounded, straighter poste-
I'ioi'ly, and merging into the ivir without deliiiitc limitation.

Left valve moderately convex. Right valve nearly Hat, narrower and
ol)li(|ue, with a deeper hyssal sinu.s.

Hinge-line .straight, nearly central, equalling, or a little greater tlian. the
length of the .shell.

Beak suh-acute, anterior to the centre of the hinge-line, directed slightly
forward. Urahonal region somewhat prominent, suhtending an angle of
ahout 75°.

Ears triangulai-. I'osteiior one much the larger, not distinctly defined on
the valve; margin sligiitly concave; exti'cmity rcctauLinlar oi' somewhat
acute, .\ntfi-ioi' ear small, distinctly delint'd ]\\ a roundi'd miIcus ; margin
convex ; extremitv rounded or sul)-anirular. i}\ ssal sinus moderate in the

LAMELLIBRANCHIATA. 67

left valve ; deep and angular in the right valve, as ween in the specimen
figured.

Test of the left valve marked by comparatively few, strong, rounded radii,
with intermediate smaller ones, crossed by fine concentric striae of growth,
and strong undulations which interrupt the continuity of the radii. Right
valve marked by numerous sub-equal radiating stri* which are somewhat
obsolete near the beak, and the umbonal region is marked by some strong
concentric wrinkles. Tlie ears present, in a less degree, the same ornamen-
tation as the body of the shell.

Internal characters not observed. Ligameutal area simple.

A mature specimen is 27 mm. in length and height, and the hinge-line
28 mm.

This species differs from P. dignatm in being less oblique, the anterior ear
less extended, and the radii sharper and more interrupted. It differs from
P. latus and P. Hermes in the less obliquity and the stronger surface markings.
It differs from P. invalidus, which is similar in general aspect, in being wider,
and the margin of the posterior ear less concave.

Formation and localities. In the Hamilton group at Norton's Landing, Cayuga
lake, and shores of Skaneateles lake, N. Y.

Pterinopecten filitextus.

PLATE XVn, FIG. Si ; AND PLATE LXXXII, FIGS. 9, 10.

Pterinopecten filitextus. Hall. Pal. N. V., v<il. v, pt. 1. Plates and Explanatioiis : PI. l". fig-. 22.

Jan., IS83.

Shell larger than medium size, transversely semi-elliptical, scarcely oblique ;
length somewhat greater than the height ; margins regularly rounded, less
convex on the posterior side.

Left valve moderately convex. Right valve flat or concave.

Hinge-line straight, about as long as the length of the shell, not extended
anteriorly beyond the margin.

OS I'ALjEONTOLOGY of NEU YORK.

Beaks obtuse, anterior to tlic miilillc of the valve, directcil foiwiird, not
well defined. Fndjonal region not strongly marked.

Ears une(inal. Posterior ear wide-triangular, extending as far as the mar-
gin of the shell, its limits undefined ; margin nearly straight ; extremity- ree-
tangular. Anterior ear small, limited by a strong sulcus ; margin concave;
extremity obtuse. Byssal sinus in the left valve moderate; in the right
valve well-marked.

Test of right viilve tliin, marked by fine filiform radii, with nnuli \\ ider
interspcaces which are marked hy finer rays; the same character continuing
on the posterior ear, with more e(inal rays. The entire surface is iiiinkcil
by fine, close, concentric lines of growth, with lanicllose elevations at unci|iial
intervals.

Hinge-ligament marked by several parallel grooves.

A right valve measures approximately 35 mm. in length, and li'.i mm. in
height.

In general form this species resembles P. conspectus, T)nt is j)roportionally
longer, and the surface markings are different.

Formation and localities. In the Hamilton group near Cai-diff, Onondaga
county, and from a bowlder of Hamilton shale at Pine Valley, Chennmg
county, N. Y.

Pterinopecten intermedius, n. sp.

I'l.ATK XVII. FKi 19; akI) I'LATK I.XXXIII, Fl(;s. 4, 6.

I'terhiopeclcii cifiispKutits, in pari. Ham,. I'al. N. V., vol. v. jit. 1. I'latos aiKl Kxiiliinjitidiis : PI. 17. ti^r. lil,

.Ian., 1883.

Shell of medium size, sul)-rliomlioi(lal, obli([ue ; ienglii one-fourth greater than
the height; margins regularl\ i-ouiided, nu)re convex on the post-l)asal side.

Left valve convex, greatest convexity below tlie uinlio. Kiglit valve
unknown.

Hinge-line straight, somewhat anteiior : length greater tlian tlic length ol'
the valve.

LAMELLIBRANCHIATA. 69

Beak acute, well defined, arching over the hinge, directed forward, situated
anterior to the middle of the shell and of the hinge-line.

Anterior ear small, triangular, with a longitudinal fold ; limited by a broad
sulcus ; margin slightly convex ; extremity acute. Posterior ear large, broad-
triangular, undefined ; margin slightly concave, extending at right angles to
the hinge, to the post-basal side of the valve; extremity angular. Byssal
sinus broad in the left valve.

Test thin, marked by fine, alternating, filiform, radiating striae, which
increase by implantation until they are very numerous at the basal margins
of some specimens, crossed by fine lines of growth with a few concentric
undulations. The ears preserve the same surface characters in a subdued
degree. Many of the specimens are exfoliated and the surface markings are
very obsciu-e or obsolete.

The characters of the interior have not been observed.

A specimen of the left valve has a length of 14 mm., height 12 mm., hinge-
line IC) nun. A larger example has a length of 19 mm., height 16 mm., and
hinge-line 21 mm.

This species was arranged with P. conspechis. The recent study and compari-
son of a more numerous series of specimens shows several important dift'erences,
and necessitates the removal of this form from that species.

The present species is more oblique, narrower, and the posterior ear is
comparatively longer than in authentic forms of P. conspectus.

In P. Hermes the hinge-line is more extended posteriorly, and the umbonal
angle more obtuse, while in P. regularis the hinge is shorter, the extremity of
the posterior ear rounded, and the margin continuous with the curvature of
the pallial margin of the valve.

Formation and localities. In the shales of the Hamilton group at Ludlowville,
Tompkins county, and on the shores of Cayuga and Canandaigua lakes, N. Y.

70 PALEONTOLOGY OF NEW YORK.

PtERINUPKCTEN KEGULARIS, 11. sp.

I'l.ATE LXXXIII, FIG. 1.

Shell of medium !<ize, semi-circular, body ui" the valve oblique; leuj^th nearly
one-fifth greater than the height, greatest length above the middle ; margins
very full and regularly rounded from the byssal sinus to the posterior extrem-
ity of the hinge.

Left valve moderately convex. Right valve unknown.

Hinge line straight, anterior ; length a little greater than the length of
the valve.

Beak of left valve acute, directed forward, situated anterior to the middle
of the hinge.

Anterior ear small, triangidar, more than half as long as the posterior
ear, limited by a broad sulcus; margin convex; extremity rounded. Posterior
ear large and undefined from the body of the v^alve ; margin convex, in
regular continuation with the pallial margin; extremity obtuse, angular.
Byssal sinus broad.

Test thin, marked with iiumei-ous fine, alternating, filiform, elevated striae
which are crossed by irregular lines of growth. The ornamentation of the
ears is somewhat more subdueil than on tlic body of the valve.

Muscular impression sm.all, ovate, situati^d below the miildlc of the post-
cardinal slope.

A specimen of the left valve has a length of 2-4 mm., height 19 mm.,
hinge-line 2-") mm. A larger example measures 30 mm. in length.

This species is distinguished for the regular continuous convex curvature of
the outline from the byssal sinus to the posterior extremity of the hinge. In
this respect it differs from any other form of tliis genus here described. The
right valve of P. filitextus has a similai- outline, but the left \nl\-e has l)een
shown to have the margin of the jjosterior ear concave and the extremity
acute-angular. The specimen of the right valve of that species, figured in

LAMELLIBRANCHIATA. 71

fig. 22 of pi. 17, is imperfect at the posterior extremity of the hinge, and
thus resembles the present form more than it would if properly restored.

Formation and localities. In the shales of the Hamilton group, between
Genesee and Avon, and at Delphi, N. Y.

Pterinopecten Vertumnus.

PI-ATE V, FIGS. 1-8 ; and PLATE LXXXIII, FIGS. 2, 3.

Ptei-inopecten Vertumnus, Hall. Pal. N. Y., vol. v. pt. 1. Plates and Explanations: PI. 5, figs. 1-8.

Jan., 1883.

Shell large, rhomboidal, oblique ; greatest length below the middle of the valve ;
length about one-fifth greater than the height ; margins regularly rounded,
becoming full behind and sloping rapidly to the hinge-line.

Left valve depressed-convex. Right valve nearly flat.

Hinge-line straight, somewhat shorter than the length of the shell.

Beaks ol)tuse, low, anterior to the middle of the hinge-line, directed
forward. Umljonal region moderately convex in the left valve, depressed
in the right valve, limits defined anteriorly, but not posteriorly.

Ears triangular, flat. Posterior ear much the larger, not defined from
the body of the valve ; margin gently concave ; extremity acute. Anterior
ear small, separated from the umbo by an undefined sulcus, and in the right
valve by the marked, angular byssal sinus ; margin concave ; extremity acute,
sometimes rounded.

Surface of left valve marked by irregularly alternating, strong, flexuous,
flattened radii ; interspaces flat ; crossed hy sharp, elevated, concentric strise
which are more closely arranged towards the margin of the shell. The
same character of surface continues over the ears, and on the posterior ear
the radii are finer, nearly equal in strength, and crenulated by the concen-
tric striaj. On the right valve the rays are more equal and finer than on the
opposite valve; conspicuous on the posterior ears and subcUied on the
anterior.

Three specimens have respectively the following dimensions : length
38, 40, 41 mm., height -SO, .3-3, 29 mm., hinge-line 35, 35, 32 mm.

Tii PALJEONTOLOGY OF NEW YORK.

This spt'fies resonil)k's Pterinea reprobvs, from the shales of the Chemung
f^roiij) at Ithaca, wliich has straighter and more rounded radii in the left valve,
with sharper intermediate radii and more elevated, undulating, concentric strife.
Till' right valve of that species is more convex with stronger and often dupli-
cating radii ; wliiU' the l)yssal sinus is less distinctly marked. The present
species differs from Pterinopeden dispandus in its greater length, projjortionally
longer hinge-line, less strongly marked right valve, and want of duplicaticm
in the radii.

Formation and locality. This species iscomiium in the shales of the Ilainilton
group at Bear gulf, Schoharie county, N. Y.

Ptekinopecten undosus.

PI.ATK II, FIOS. 10-I!I; AM) rLATK LXXXIl, FIG. 7.

Avicatitpeiten undrtlatus. Hall. M.S. 1877.

" " " Cat. Amer. Palieozoic Fo.ssils. S A. Millkk. 1877.

Not Pecteii undiUatits, McCoy. Carb. Foss. of Iielami, p. 101, pi. xvii, fig. 12. 1844.
Not Aril iilitjKtten imdiilatn.^, McCoy. 1853.

Pterimipeiiett undositSy Hall. Pal. N. Y., vol. v, pt. 1. Plate.s aiRi Explanations: PI. 2, tig-s. 10-19.

.Jan., 1883.

Shell larL^cr tlian medium, rhdiiilioidal or siil)-urbicular ; left valve moderately
oblique ; right valve scarcely oblique ; length one-third greater than the
height, proportionally shorter in young shells ami in tlic riglit valve; ante-
rior and l)asal margins regularly rounded, .sonu'what i)r()(lucc(l l)eliinil. and
receding rapidly toward the hinge-line.

Valves nearly equally convex ; the riglil valve a little less convex, more
orbicular in outline, with deep byssal notch, and different surface markings.
When occurring in the softer shales, the valves are often (k'j)ressed-convex.

Hinge-line straight, length a little li'ss than the height of the shell, nearly
central.

Beak obtuse, rounded, scarcely rising above the hinge-line, anterior to the
middle of the shell, inclined forward. Umbonal region ample, well-defiiied,
subtending a very obtuse angle.

LAMELLIBRANCHIATA. 73

Ears sub-equal, triangular, undefined; margins concave. Anterior ear
limited by a sulcus and shallow sinus ; extremity acute. In the right
valve sub-triangular ; margin rounded, defined by an abrupt sulcus and a
deep, angular byssal notch, which encroaches on the body of the valve. In
the posterior ear the extremity is obtuse in the left valve, somewhat more
pointed in the right valve.

Test thin, marked by numerous fasciculate rays, which increase by inter-
stitial addition, with interspaces varying from nearly equal to several times
the width of the rays ; cancellated and sometimes crenulated by elevated,
lamellose striae of growth ; and by from three to ten strong, concentric undu-
lations, which are rounded upon the summits. The markings on the ears
are similar to those on the body of the shell ; the rays on the anterior ear
are sometimes obscured by the striae of growth.

Interior not known. Ligamental area narrow.

A left valve has a length of 51 mm., height 36 mm., hinge-line 36 mm.
A right valve has a length of 44 mm., lieight 37 mm., hinge-line 35 mm.
A young specimen has the following dimensions : length 23 mm., height
19 mm., hinge-line 20 mm. ^

This species is distinctly characterized by the strong, concentric wrinkles,
the deep byssal sinus of the right valve, and by the form of the shell. Speci-
mens vary in the frequency and elevation of the radii, and in the number and
prominence of the concentric undulations.

The specimens are casts of the interior, with scarcely any remaining test.
The surface markings are therefore subdued, and the concentric striae are often
not at all preserved.

This species is widely distributed. It has been found in the Corniferous
limestone at a single locality ; and in the soft shales of the Hamilton group
throughout the western portion of the State.

Formations and localities. In the Corniferous limestone at Clarence Hollow,
Erie county ; in shales of the Hamilton group at numerous localities in Central
and Western New York.
10

74 PALEONTOLOGY OF NEW YORK.

PtERINUPECTEN (AvICULOPECTEN ?) STRICTUS.
ri.ATK XXIV, FIG J; ami J'LATK I.XX.XI, KIG. 18.

PlirhD'jKittii flriilu-i. Uai.i.. Piil. N. V., vol. v. jit. 1. Pliites anil Exiilamitioiis : PI. 24, tifj. 2. Jan., 1883.

SiiKi.i. of nu'diuin size, transversely semi-elliptiral. not olilifnic; body of the
shell ovate, length one-sixth less than tlie lieight ; aiiteiior and lia.sal
margins rounded ; posterior margin straight.

Left valve moderately convex. Right valve tlat.

Hinge-line straight, equal to the length of the shell, ceiilral as; regards
the transverse axis.

Beaks obtuse, low, directed slightly foiward, anterior to the middle of the
hinge-line. Umbonal region moderately prominent in the npper part, sub-
tending an acute angle.

Ears triangular. Posterior ear much the larger, Hat; margin concave;
extremity slightly acute, obscurely defined. Anterior ear small, convex,
defined by a well-marked gi'oove or sulcus; margin rounded; extremity
acute. Bj'Sfial siiuis distinct in the left valve, and a deep rounded notch in
the right valve.

Test of left valve marked by alternating stronger and liner rounded radii,
crossed by sharp, elevated, concentric lines of growth and more distant
undulations, with imbricating lamellose lines. These markings are continued
over the ears, nnich subdued on the right valve, and obsolete upon the
umbo.

Ligamental area marked by two or three furrows, and a central cartilage-
pit.

The specimen figured has a length of 25 mm., height 30 mm., hinge-line
25.5 mm.

This species is donlitlully arranged with the present group of I'onns. In
some aspects it resembles P. conspectus, but is specificalW very distinct. It
might be compared with the young of some large forms of Lyriopecten or with
Aviculopecten, but the extent of the hinge-line, and the undefined limitation

LAMELLIBRANCHIATA. 75

of the posterior ears, do not assimilate it with the ordinary characters ascribed
to those genera.

Formation and locality. In the Clieniung group near Elmira, N. Y.

Pterinopecten imbecilis.

PLATE XXIV, FIG. 1.

Pleriiiopecteti, imherillt. Hall. Pal. N. Y., vol. v, pt. 1. Plate.s anil Exiilanatidiis : PI. 24, tig. 1.

Jan.. 1S83.

Shell small, rhomboidal, oblique, much longer than high ; anterior and basal
margins rounded ; posterior margin produced.

Left valve moderately convex. Right valve not known.

Hinge-line equal to, or greater than, the length of the body of the shell.

Beak obtuse, directed forward, rather prominent. Umbonal region ample,
defined anteriorly ; subtending an angle of about 90°.

Ears very unequal, triangular. Anterior ear small, defined by a distinct
sulcus. Posterior ear large, undefined ; margin concave ; extremity angular.

Surface marked by numerous strong, simple radii, with wider interspaces
which have usually finer intermediate radii ; crossed by fine, equal concentric
lines of growth, and stronger, more distant lamellas, which are elevated and
arched backwards over the larger rays, producing nodes.

Internal characters not preserved.

The specimen has a length of 15 mm., height 11 mm., hinge-line about
15 mm.

This species differs from P. latus, by its distinct and widely separated rays,
and more oblique outline.

Formation and locality. In the Chemung group at Tioga, Tioga county, Penn-
sylvania.

76 PALEONTOLOGY OF NEW YORK.

PtERINOPECTEN DISPANDUS, 11. sp.
PLATK I.XXXII. FIGS. II, li.

.SiiKi.i. large, soiiK'wliat liitiinlMpiil-ovatt', i)lilii[iit', varviiij;' with iIr' at;v of the
slioll ; length a little greater than the height; margins regularly curved,
extending behind.

Left valve convex. Right vahe depressed-convex, somewhat smaller
than the left, and proportionally longer.

Hinge-line straight, less than the greatest length of the slicll, nearly
central.

Beaks oljtnse, little elevated, anterior to the middle, directed forward.
Umbonal region scarcely defined, moderately prominent, subtending a right
angle.

Ears triangidar, nndefined; margins concave. Posterior ear larger than
the anterior. Anteiior cai- liuiited by an undefined sulcus and moderate
sinus; extremity rounded. In the right valve, the anterior ear is narrow,
acute, with a deep, angular byssal sinus.

Surface ornamented by prominent, r()\inded radii, which alternate irregu-
larly with finer intercalated radii, and increase in size and number towards
the margin ; crossed by concentric striae, with more distant varices of growth
which crenulate the radii. The rays are stronger over the anterior slopes,
and are continueil on the ears, somewhat finer on the posterior and stronger
on the anterior. In the right valve the strong rays are regularly duplicat-
ing, and are finer and equal on the posterior ear, with a few stronger ones
on the anterior ear.

Ligamental area narrow.

Two left valves measure respectively 45 and 87 mm. in length, 42 and
44 mm. in height, hinge-line 40 and .'id iniu. A right valve is 82 mm. in
length, 27 mm. in height, liinge-line 28 mm. Other specimens of the left
valve vary considerably, apparently according to age.

This species differs from P. Vertumnus in its greater proportional height,
shorter hinge-line, abruptly rounded radii, and niuidi sharper small intermediate

LAMELLIBRANCHIATA. 11

striaa. The radii upon the right valve are also stronger and distinctly bifurcat-
ing; the concentric striae are stronger, closer, and crenulate the rays more dis-
tinctly. P. suborbkularis is less oblique and the form more rounded, while
the rays are more numerous and closely arranged.

Formation and localities. In the Chemung group at Belmont, Alleghany county,
N. Y., and Mansfield, Tioga county, Pennsylvania.

Pterinopecten erectus.

PLATE LXXXII, FIGS 15-17.

Shell above medium size, transversely semi-elliptical, scarcely oblique ; length
and height nearly equal ; pallial margins regularly rounded, slightly ex-
tended on the posterior side.

Valves moderately convex. Right valve apparently more convex than the
left ; the differences between them have not been satisfactorily determined.

Hinge-line straight, length a little greater than the length of the shell.

Beak small, acute, directed forward, little elevated above the hinge-
margin ; anterior to the middle of the shell. Umbonal region not defined.

Ears triangular, unequal. Posterior ear large, undefined ; margin slightly
concave ; extremity acute. Anterior ear much smaller, not defined ; margin
concave ; extremity acute. Byssal sinus shallow.

Surface marked by numerous rounded unequal radii ; the larger ones
alternating with one, two or three smaller ones ; crossed by fine, sharp,
regular, concentric strite of growth. On the ears the striae are fine and
uniform.

Interior not known. Ligamental area narrow.

The largest specimen has a length of 32 mm., height 30 mm., hinge-line
about 34 mm.

There is some resemblance between this species and P. dispandus, but it
differs in its comparatively smaller size, longer hinge-line, and somewhat less
oblique form.

Formation and locality. In the shales of the Chemung group at a point 600
feet above the base of the formation, at Ithaca, N. Y.

78 PALEONTOLOGY OF NEW YORK.

Pterinopecten crenicostatus.

PLATE VIII, KR;s, 3, 4; ani> PLATE LXXXII, FIG. 14.

Pterino]>e<tiii crenulatiut (by error), Hai.l. Pal. N. Y., vol. v, pt. 1. Plates and Ex]>lanatioiis : PI. 8, figs.

:!. 4. .Jan., 1S8S.

Shell larj!;e, suh-orbicular, sli;:litly ol)li(jVK' ; length somowhat greater than the
height ; pallial margins reguhirl}- curved, l)roadly rounded from the antero-
hiteral to the basal margin ; post-lateral margin less convex.

Left valve very moderately convex. Kight valve not known.

Hinge-line straight, length one-fifth less tliaii the length dl' the shell,
exteiiilrd anteriorly, but not as far as the anterior mai'gin of the valve.

l')eak obtuse, rounded, scarcely directed forward, prominent, anterior to
tlic iniddlc. Uml)onal region wide, indistinctly defined on the jwsterior
sitle, more distinctly limited anteriorly, subtending an angle somewhat
gi-eater than 90°.

Ears triangular. Hat. Posterior ear five times as large a.s the anterior,
undefined ; margin straight or slightly concave ; extremity abruptly acute.
Anterior ear small ; margin deeply concave from the byssal sinus; defined by
a distinct sulcus ; extremity acute.

Test apparently thick, marked by al)()ut fifty strong, roimded rays which
are simple oi- bifurcating, always with liner intermediate rays. Concentric
striae strong, elevated, conspicuously crenulating the radii. The radii mark
the ears, and on tli(> posterior ear are simple and distant.

Internal characters not known.

The two specimens figured give about the following respective dimensions :
length 50, 57 mm., height 47, 53 mm., and length of hinge-line 52 and
40 mm.

This species differs from P. suborbicularis in being more inequilateral, with
longer hinge, and stronger and less frequent radii. It differs from P. Neptunus,
pi. 8, fig. G, by its more erect form, extended hinge-line, distant and elevated
radii, with stronger and more elevated concentric strife.

Formation and localities. In ibe .-bales of tlu' Cheinuug gi-ouj) at Angelit'a and
Conewango, N. Y., and at Mansfield, Tioga county, Pa.

LAMELLIBRANCHIATA. 79

Pterinopecten Neptunus.

PLATE VIII, FIGS. 5-7.

Pleri nnpecten Neptiuiii-', Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 8, tigs. .5-7.

Jan., 1883.

Shell large, sub-orbicular, moderately oblique (more so in young shells) ; length
one-fifth greater than the height ; pallial margins regulai'ly rounded, becom-
ing extended posteriorly.

Valves moderately and nearly equally convex ; very similar in form and
surface markings.

Hinge-line straight, length less than the length of the shell, situated ante-
riorly as regards the body of the valve.

Beaks obtuse, rounded, directed .^lightly forward, nearly erect, not promi-
nent. Umbonal region wide and undefined posteriorly, subtending a very
obtuse angle.

Posterior ear much the larger, slightly concave on the margin ; extremity
angular. Anterior ear small, separated from the body of the shell by a
sulcus ; margin convex, extending obliquely outward from the byssal sinus ;
extremity acute.

Surfiice marked by closely arranged, rounded or sub-angular rays, which
increase by intercalation and bifurcation. The ears are marked by simple and
smaller rays, which in the right valve are distinctly angular. The rays
become obsolete on the umbo. The concentric striae are close, undulating,
and in some conditions may have been sharply elevated and lamellose.

Internal characters not known.

The specimen, fig. 6 of pi. 8 is 55 mm. in length, 46 mm. in height, hinge-
line -88 mm.

The comparison of this species with P. crenicostatus is given under the
description of that species.

In surface ornamentation this species somewhat resembles P. Vertumnus, but
the shell is shorter and less oblique, the hinge-line shorter, and the concentric
striae less elevated.

80 PALAEONTOLOGY OF NEW YORK'.

Formation and }ocalilie.s. In tlie shales of the Chemung group, Angelieu and
PliiHpshurg, Alleghany county, N. Y.

Pterixopecten suborbicularis.

I'LATK Vin, KlliS. 1, 2; PLATE XXIV, FIG. 10; ani> PLATE LXXXII, FIG. 6.

PUrintn! yiiUirlniiilarix, Hall. Geolog'. Surv. N. Y. : Rep. Fourth Dist., p. 264. 1843.
Pttrinuptctfu sulxirhiciUarui, Hall. Pal. N. Y., vol. v, pt. 1. Plates ami Exjilanations : PI. 8, figs. 1, 2 ;

1)1. 24, fig. 10. Jan., 18,S3.

Shell large, rhomboid-orbicular, slightly oblique ; length a little greater than
the height, or sometimes equal ; pallial margins regularly curved, less con-
vex on the pojsterior side; post-ba.'jal margin extended.

Left valve convex. Right valve nearly tlat ; similar in general form and
surface markings.

Hinge-line straight, anterior, nearly equal ix> the length of the shell.

Beak obtuse, broad, rounded, somewhat depressed, directed slightly
forward ; a little anterior to the centre of the hinge. Umbonal region
expanded, subtending an obtuse angle.

Ears triangular, unequal ; extremities angular. Posterior ear tlic larger,
undefined ; margin concave. Anterior ear limited b}' an obscure sulcus.
Byssal sinus shallow in the left valve, deep and angular in the right valve.

Surface marked by numerous regular, rounded or sub-angular radii, which
increase on the left valve by intercalation, and on the right valve by bifur-
cation ; interspaces nearly equalling the rays. On the posterior ear the
rays are finer, and over the body of the shell they are strongly crenulated
by lamellose concentric striae.

Internal characters unknown. The ligamental area is a simple linear
groove.

A large specimen measures 63 mm. in length, 55 mm. in height, the hinge-
line 55 mm. Another one is .SS nun. in length, .35 mm. in height, with
hinge-line .35 mm.

This .species is distinguished by its sulj-orbicular form, slight obliquity, nearly
e<|ual length and height, ami comparativt'ly short hinge-line.

LAMELLIBRANCHIATA. 81

The comparison with P. crenicostatus is given under the description of that
species. It resembles the young of Lyriopeden orbiculatus, but the details of the
characters are quite different.

Formation and localities. In the Chemung group at Hobbieville and Elm
Valley, Alleghany county; New Albion, Cattaraugus county, N. Y., and
Mansfield, Tioga county, Pennsylvania.

C R E N I P E C T E N ,* Hall.
Crenipecten amplus.

PLATE IX, FIGS. 9, 13, 18.

Orenlpecte7i amplux. Hall. P;il. N. V., vcl. v. jit. 1. PLites and Kxiilanations : P!. 9, figs. 9, 13. Jan., 1883.
Crenipecten crenidatuJi ? UALh. Pal. N. Y., vol. v, pt. 1. Plate.s and Explanaticm.s : PI. 9, fig. 18. Jan., 1883.

Shell larger than medium, broadly and o])liquely ovate ; height about one-
sixth greater than the length ; margins regularly rounded, more extended
posteriorly.

Left valve ver^^ convex. Right valve not known.

Hinge-line straight, about equal to one-half the length of the shell, situated
a little anterior to the middle.

Beak obtuse, erect, prominent. Umlional region very convex, well
defined, subtending a right angle.

Ears nearly equal ; margins gently concave. Posterior ear somewhat the
larger, defined by a sulcus. Anterior ear defined by a sulcus which is more
distinct and abrupt. Byssal sinus shallow.

Surface of the cast marked by fine, irregular, concentric striae, with
obsolescent, fine radiating lines. Ligamental area narrow and distinctly
crenulate.

* The forms here described under this generic term have in jiart been leferred to Pebnopecten by Pro-
fessoi- Winchell ; but a critical study of the type species of that geiuis i-hows that it possesses a large central
cartilagp-pit with a crenulated hinge-)ilate on each side below the hinge-margin, which characters alone ai-e
sufticient to distinguish the genus and exclude the foi-ms here described uadei' Crenipecten. See discus-
sion of the relations of Pehnopectbn, Entolicm and Crenipecten, in the introduction to this volume.

11

82 PALEONTOLOGY OF NEW YORK.

Tlie larjjest speoimtMi is 88 mm. in lon,t;:th, 88 mm. in liciirht, liiiiL'^c-line
IG mm.

Thi.s species differs from P. crenulalus in its pn)]i()rti(>n:illy irrentcr licinlit,
rotiuulitv, and less ol)iiquity.

Altliouffh known o\\\y as a cast, it is distinctivL'ly different iVoin otlicr s])ecies.

Formation and locality. In shales oi" tlie Cliemunj; group at luH'.k\ ille, AUe-
jrliany county, N. Y.

Crenipkcten CRENULATUS.

IT. ATE IX, KKJS. fi. 7. s, 15, Hi, 17

I'nltn! crenntai ii.<i, H.M.L. (tCoIo^-. Surv. N. Y. : Rep. Fourth Dist., p. 21)5. 1S43.

Crenipet-tfii in-Kiiidatiut, Hai.l. Pal. N. Y., vol. v, pt. ]. Plate.s and Explanation.* : PI. SI, tip;. tj-S. ).")-17.

Jan., 1883.

Shell of medium size, ovoid-orhicular, moderately oblique ; length and liciulit
nearly equal; margins regularly rounded, somewhat extended posteriorly.

Right valve convex. Left valve depressed-convex ahove. and nearly Hat
below.

Hinge-line straight, length more than one-half the length of the valve,
anterior to the middle of the sliell.

Beaks obtuse, central, inclined .somewhat foi-ward. not I'ising aliove the
hinge-line. Unibonal region of the right valve ]ii()inincnt, siilitending an
angle of about 100°.

Ears small, triangular, subequal, limited on the right valve by the rapid
slope of the sides of the umbo; margins slightly concave; extremities angu-
lar. Ryssal sinus not defined.

Test thin; conspicuously marked with fine, concentric striae of growth.
and obscure or nearly obsolete radii (as seen m figs. 7, 8 and 16, pi. '.)).
The concentric lines are stronger on the ears, and are sometimes cancellated
by fine rays.

Ligamental area narrow, creiudated l)y a row of iiiiiiute cartilage-pits.

A medium-sized speciuien has a length of 'JU mm., height 81 iiiiii.. hinge-
line 17 mm. A smaller specimen has a length of lii'i nnii., height 29 mm.,
and binge-line 16 mm.

LAMELIABRANCHIATA. 83

All the sjjecimens are in the condition of casts or much exfoliaterl, and the
surfiice markings are therefore obscm*e.

The species was originally founded upon specimens of the left valve ; the
right valves shown in figs. 6, 7 and 8, pi. '.), occur in the same association,
and have been identified as of the same species.

This species differs from C. obsoletus in its proportionally greater convexity
and length, and the obliquity of the transverse axis. It is also longer than
C. amplus.

Formation and locality. In shales of the Chemung group at Rockville, Alle-
ghany county, N. Y.

Crenipecten impolitus.

PLATE IX, FIG 14; and PLATE L5XXIII, FIi;. 10.
Cretiipecten hnpalitiis. Halt.. Pal. N. V.. vol. v. |it. 1. Plates and Explanations: PI. il, tig. 14. Jan., 1SS3.

Shell of medium size, obliquely sub-ovate ; length somewhat less than the
height ; anterior and basal margins regularly rounded, produced behind and
extending thence in nearly a direct line to the beak.

Left valve depressed-convex. Right valve not known.

Hinge-line straight, anterior, less than half the length of the shell.

Beak obtuse, rounded, low, inclined a little forward. Umbonal region
scarcely defined, subtending about a right angle.

Ears nearly equal ; margins concave. The posterior ear extends along the
posterior margin as a nai-row expansion. In well-preserved specimens the
ears are defined by sulci. Byssal sinus inconspicuous.

Obscure evidences of concentric striae appear in the casts.

Internal characters unknown.

Two .specimens have respectively the following dimensions: length 24
and 16 nmi., width 26, and 19 mm., hinge-line 9 and 7 mm.

In general form iind convexity this species resembles C. crenulatus, but it is
narrower above, with the hinge-line comparatively much shorter.

84 PAL/IJOSTULOC'Y OF KEW YORK.

The specimens Jire casts of the interior preserved in coarse sandstone; the
surface niarlvings are consequently olditerated.

Formation and locality. In u coarse sandstone of tlie ^'heinunu lh-oii]) near
Olean, Alleuhany countv, N. Y.

Crenipecten obsoletus.
ri.ATK IX, ri<;s. m, -n.

Lima* nhsdhta. Hall. Ocoloff. Siirv. N. V. : Rt'j). Fuiirtli Dist., )>. "iGS. 1843

CnntpeeUii utmolHiin, Hall. Pal. N. Y., vul. v, i>t. 1. Plates iiml Kxplaimlimis : PI. il. lifrs. l!i, lil.

Jan., 1S83.

Shell .small, ohliquely sub-ovate, length nearly equal to the heiuht ; martrins
regularlv curved, becoming produced on the post-basal side, and somewhat
rectilinear on the posterior side.

Valves very similar. Right valve depressed-convex. Left \alve regularly
convex.

Hinge-line straight, a little more than one-half the length of tlu' shell.

Beak obtuse, more proniineiit on the left valve; situated in the centre of
the hinge. Umbonal region well defined in the left valve; depres.sed and
undefined in the right valve.

Ears small, triangular, sub-equal, delined by shallow sulci ; margins gentlv
concave; extremities o])tuse. Posterior ear a littl(> the larger, liyssal sinus
not conspicuous.

Test thin, markeil l»y line, closely arrangeil, concentric striiv, which are
crowded and stronger on the ears. No radiating stria* have been discovered.

Ligamental area narrow, marked liy a row of minute cartilagt'-pits.

A left valve measures 18 mm. in length, 20 mm. in height, hinge-line id
mm. A similar right valve is 16 mm. in length, 17 mm. in height, hinge-
line 8.-") mm.

Tills species bears some resemblance to C. crenulatus, but is more elongate-
ovate; less oblique, with the height somewhat greater than length.

Formation and locality. In shales of the Chemung group at l'hilip,sl)urg,
Alleghany county, N. Y.

LAMELLIBRANCHIATA. 85

Crenipecten glaber.

PLATE IX, FIGS. 20, 22?

Lhiia fflaber, Hall (xeolog. Siirv. N. Y. : Rep. F<mrth Dist., p. 255. 1843.

Crenipecten glaber. Hall. Pa!. N. Y. vol. v, pt. 1. Plate.=! and Explanations: P!. 9, fig-s. 20, 22?

Jan., 1883.

Shell small, ovate, erect, very slightly oblique ; height about one-fifth greater
than the length ; pallial margins regularly rounded, more extended on the
posterior side.

Left valve moderately convex above, and depressed-convex below. Right
valve unknown.

Hinge-line straight, length equal to about one-half the length of the valve.

Beak acute, erect, somewhat prominent, not elevated above the hinge.
Uniljonal region well defined by the sulci, subtending an acute angle.

Ears triangular, nearly equal, separated from the body of the shell by
shallow sulci ; margins straight or slightly concave : posterior ear a little
the larger. Byssal sinus not distinct.

The cast is marked only by fine concentric striae.

Interior unknown.

The crenulations of the ligamental area are obscure in the specimen.

The original of this species is 12 mm. in length, 16 mm. in height, and
hinge-line G mm.

This specimen is embedded vertically to the lines of rock bedding, and the
proportions of length and height may have been changed. The species is
known by its erect form, conspicuous ears and great comparative height.

The specimen of figure 22 is referred with doubt to this species; the erect
form is similar ; the proportional length is slightly greater.

Formation and localities. In shales of the Chemung group at Philipsburg and
Rockville, Alleghany county, N. Y.

8G PALJEONTOLOGY OF NEW YORK.

Crenipecten micropterus.

'I.ATK I.\, FKi. a.

Crenipecten. m'wrupteriix. Hall. Pal. N. V., vol. v, pt. 1. Plata's ami Explanations : PI. 9, ti^. 2, 8.

Jan.. 1883.

SiiKLL small, loniritiiilinally iiml i)i)rK[uely sub-elliptical; length somewhat
great-er than the height; margins regularly roundeil, produced behind and
extending in nearly a direct line to the beak.

Right valve depressed-convex. Left valve unknown.

Hinge-line short, straight, anterior; length about one-third the height (jf
the valve.

Beak low, obtuse. Umhonal region not strongly defined, subtending an
obtuse angle.

Ears very stuall, nearly equal, bounded by shallow sulci. Byssal sinus
not (li.-^tinct.

Surface marked by numerous low, rounded radii, with wider interspaces
and smaller intermediate radii ; crossed by fine concentric lines of growth,
which arc stronger and crowded on the ears, forming their only surface
marking.

Interior unknown. LiganuMital area ob.scurely crenulate.

The specimen described has a length of 18 mm., width Iti inin., liinge-
line 5 mm.

This species resembles in form C. crenulaius, but differs in the radii, and in
the proportionally much shorter hinge-line. The surface markings are similar
to C. liratus, but it is different in its proportions of length and height.

Formation and locality. In the shales of the Chemung group at Philipsburg,
Alleghany county, N. Y.

LAMELLIBRANCHIATA. 87

Crenipecten liratus.

l-LATE IX, FIG. -24 ; and PLATE LXXXIII, FIG. 9.
Crenipecten Hratitu, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. fl, fig. 24. Jan., 1883.

Shell small, obliquely sub-ovate ; length a little less than the height ; anterior
and basal margins rounded ; post-basal margin produced, and thence extend-
ing in a direct line to the beak. '

Left valve moderately convex, the greatest convexity distant one-third the
lieight of the valve from the beak. Right valve unknown.

Hinge-line straight, short, length about one-third the height of the valve.

Beak acute, erect, a little anterior to the centre of the shell, not rising-
above the hinge. Umbonal region moderately elevated, subtending an acute
angle.

Ears small, triangular, defined by moderate sulci ; the posterior ear the
larger. Byssal sinus not distinct.

Surface marked l)y prominent, rounded, alternating radii, with interme-
diate snudler ones. There are about six larger rays, six smaller, and twice
that number of still smaller intermediate strias, all crossed by strong, regular,
concentric laminaj of growth. The ears are apparently destitute of rays.

The crenulations of the ligamental area are small and obscure.

The specimen figured has a length of 20 mm., height 22 mm., hinge-line
7 mm.

This species somewhat resembles C. micropterus in the radii, but differs in all
other characters.

Formation and locality. Chemung group at East Randolph, Cattaraugus
county, N. Y.

88 PALEONTOLOGY OF NEW YORK.

Cbenipecten Leon.

hLATK IX, FIG. 12 ; and I'LATK L.XXXIII, FIG. 8.
Crmiperteit Leim, U.ku.. I'al. N. V.. vol. v, pt. 1. Plato.s and Explanations: PI. !». tip. 12. Jan., 1883.

L511K1.1. of meiliuiii .size, ovate, slightly oblique ; length about one-sixth less than
the height; margins regularly curNcd, produced below, rather straight on
the upper part of the posterior side.

Left valve moderately convex ; the greatest convexity is a little lielow the
middle.

Hinge-line straight, short, nearly central ; length aliout oiio-third the
lieight of the valve.

Beak acute, erect. Uniboiial region not strongly marked, subtending an
acute angle.

Ears sub-equal, small, sulci not conspicuous; posterior ear tlie larger.
A narrow rim, slightly elevated and free from rays, extends from the poste-
rior ear along the margin of the shell.

Surface marked with numerous distinct, rounded or sub-angular rays, and
wilier interspaces with smallei- intiTuiediate rays; with line concentric .strise
and undulations at irregular intervals. The rays are stronger over the pos-
terior half of the valve.

Ligamental area linear, and crenulated with narrow cartilage-pits.

The specimen liguri'(l has a length of l^Ci mm., lieight .30 mm., hiiige-liue
KJ mm.

This species differs iVoiii nil the others in its form and surface chiiracters.
Formation and locality. In sandstone of the Chemung grouj) at Leon, Catta-
raugus county, N. Y.

LAMELLIBRANCHIATA. 89

Crenipecten Winchelli.

PLATE IX, FIGS. 1, 1. 4, 23-30.

Avitidopecten IVinchelli, Mkek. Pal. of Oliiu, vol. ii, p. 2y6, pi. 15, tigs. 50, ati. 1875.

Creniyecten (Peeten) Winchelli (Meek), H.\ll. Pal. N. Y.. vol. v, pt. 1. Plates and Explanations: PI. 9,

ti;,'.". 1, 2. 4, 25-30. Jan.. 1883.

Shell larger than medium, flabelliform, equilateral, not oblique ; length a little
greater than the height ; margins regularly rounded below. On the anterior
■side, from a point two-thirds the height of the valve above the base, the
antero-cardinal margin extends in a direct line to the beak ; the posterior
side, from a point a little above the middle, also slopes in a direct line to the
beak.

Left valve moderately convex ; the greatest convexity about one-third the
height of the shell from the beak. Right valve nearly flat, depressed-convex
above. The right and left valves are unlike.

Hinge-line straight, central, length about two-thirds the length of the
shell. In several specimens referred to the right valve, the length of the
hinge is nearly equal to the length of the valve.

Beak of left valve acute, erect, prominent. Beak of right valve depressed,
obtuse, not rising above the hinge-line. Umbonal region of left valve dis-
tinctly defined, subtending a right angle.

Ears of left valve triangular, defined by shallow but distinct sulci. Margin
of anterior ear convex, with a shalloAv sinus at the l^ase. Posterior ear the
larger ; margin concave, with a comparatively broad sinus. The extremities
of the ears in the right valve are acute. Byssal sinus deeper and more
angular in the right valve.

Surface of left valve marked by numerous rounded or sub-angular, alter-
nating rays, with somewhat wider interspaces, crossed by sharp, elevated,
concentric strise ; the ears show the same markings. Right valve marked
by obscure radii, which are stronger on the ears.

Ligamental area with numerous narrow cartilage-pits.

A large left valve has a length of 47 mm., height 42 mm., hinge-line 29
12

00 PALEONTOLOGY OF NEW YORK.

mm. Another indivickuil measures 27 iiini. in length, 26 imu. in height,
hinge-Hno 18 mm. A right valve referred to this species has a kaigth of
20 mm. anil a height of 18 mm., hinge-lini' 17 mm.

This species differs from any known form of Crenipecten ; it is like
Aviculopecten in external form and surface characters, and resembles the
recent genus Pecten.

Mr. Meek compares this species with Aviculopecten Coxantis, Meek and
Worthen, from the coal measures of Illinois and Nebraska. It is evident that
the crenulations of the hinge have not been previously observed. Except in
the hinge crenulations, this form has no other relations with the genus Creni-
pecten, and it may be found to belong to some genus ^et undescribed, which
will include other species now placed with the Carboniferous forms of Aviculo-
pecten.

In the original descriptidu of the genus, McCoy has not indicated tiie intimate
structure of the hinge, and it is not improbable that there are several generic
types among the species iiuliidcd in the Carboniferous forms of Aviculopecten.

The right ami left valves have not been found in connrctiun. but their
association, and the absence of similar forms in the same beds, render the
identity nearly certain.

Formation and locality. In the Waverly sandstone near Newark, Ohio.

LAMELLIBRANCHIATA. 91

PTERINEA, GoLDFUss.
Pterinea grandis, n. sp.

PLATE LXXXm, FIG. U.

Shell very large, capacious, oblique, sub-rhomboidal, body broadly ovate ;
length about one-fifth greater than the height ; margins regularly rounded,
broad along the base, and a little produced on the posterior side.

Left valve convex. Right valve unknown.

Hinge-line straight, apparently somewhat less than the length of the
valve, [imperfect in the specimen.]

Beak obtuse, prominent, directed forward. Umbonal region gibbous, sub-
tending an angle of about 90°.

Wing large, triangular, not distinctly defined, margin rounded, with a
gentle concavity near the junction of the valve. Ear not observed.

Test thick, marked by distant, strong radii from the umbo to the base ;
the interspaces having alternating larger and smaller rays ; crossed by con-
centric, undulating lamellose striae of growth.

Interior unknown.

The specimen has a length of 120 mm., height 100 mm., and the hinge-
line, from the beak to the extremity of the wing, 95 mm.

This species is distinguished by its large size, very distant strong radii, and
convexity. Compared with P. jiabella, it is proportionally longer, and the wing
less defined. Compared with P. pinguis, it differs in greater length and some-
what less gibbosity.

Formation and locality. In the upper Helderberg limestone, in Scott Co.,
Indiana.

92 PALEONTOLOGY OF NEW YORK.

PtEKINEA I'INGUIS.

PLATE XV, KIGS. ■->, 3; AND I'l.ATE LXXXIII, KIG 13.

Pterinea piiiguii. Hall. Pal. N. Y, vol. v, pt. I. Pliiti's mid Kxiihiiuitiiins : PI. 1."), Kj^s. 2, ',i. Jan., 1S83.

Shell large; gibbous, obliquely ovate, length ami lieigiit nearly equal. Pallial
margins rounded, produced i>n the posterior basal side, and eoneave at the
junction of the wings.

Left valve ventricose, sub-angular along the anterior side. Right \al\e
unknown.

Hinge-line straight, nearly central ; length somewhat greater than the
length of the shell.

Beak acute, angular, arching over the hinge, situated near the anterior
extremity of the hinge-line, directed forwards. Uinl)onal region prominent,
ventricose, defined, subtending an acute angle.

Wing large, triangular, limited by the rapid post-cardinal slope of the
valve ; margin slightl\' concave, roimding to the extremity which is angular.
The extent of the ear is not known, but it is limited by a dec]) sidcus which
gives an angular aspect to tlu^ antero-cardinal sloi)e of the shell. Byssal
sinus not marked in the specimens.

Surface ornamented with about fifteen broad, strong, rounded rays, crossed
by lamellge of growth. The specimens described are weathered casts of the
interior and preserve only slight evidence of the surface characters.

Interior not known.

The largest specimen has a convexity of about 20 mm., its length 7(1 mm.,
height 65 mm., hinge-line more than 65 mm. Another example has a con-
vexity of about 20 mm., length 6.^ mm., height 74 mm., hinge-line 55 mm.

This species bears some genei'al resemblance to P. Jiabella ; it differs in its
large ventricose form, more elevatctl umbo, the characteristics of the ui)per part
of the anterior side of the body, and the abrupt slope into the wing without a
distinct sulcus.

Formation and locality. In the Corniferous limestone, near Columbus, Ohio,

LAMELLIBRANCHIATA. 93

Pterinea flabella.

PLATE XIV, FIGS. 1-21 ; PLATE XV, FIGS. 1, 1-6, 8-10 ; and PLATE LXXXIII, FIGS. 11, 12.

Aim- Ilia flabeUa. Conh.<.d. Jour. Acad. Nat. Sci., Phil., vol. 8, p. 238, pi. 12, fig. 8. 1842.

(••) Vanuxem. Geol. Surv. N. Y.: Report Third Dist. 1S43.
C'onqiai'i' Pterinea faJicicutata, Goldfuss. Petrefacta Gerinaniie, p. 137, pi. 120, fig. ."). 1840.

" " " (") Sandliei-ger, Verstfin, Rhein, Schichtensyst, Nas-'^au. j). 293, pi.

30, Hg. 7. ISfiB.

" " costulata, F. A. Rokmer, Dusker aiul von Meyer. Palaioutographica, T. 1, fig. 2.

PUri II t.a flabella, (Conrad) Hall. Pal. N. Y., vol v, pt. 1. Plates and Explanations: PI. 14, figs. 1-21;

pi. 1."), figs. 1, 4-6, 8-10. Jan., 1883.

Shell large ; broad or narrow ovate, oblique, rarely erect ; length from two-
thirds to nearly equal the height ; and in some extravagant forms the height
is about double the length ; the greatest length below the middle ; anterior
and basal margins regularly curved ; the posterior margin from a little above
the base, follows a nearly straight line to the beak.

Left valve more or less convex, often gibbous and arcuate. Right valve
flat or concave, with m little convexity on the umbo ; arcuate, to correspond
with the curvature of the oj^posite valve.

Hinge-line straight, extended upon the posterior side ; length greater than
the length of the valve.

Beak of left valve acute, rounded, situated near the anterior extremity of
the hinge, curving forwards over the hinge margin. In rare instances the
beak does not extend quite as far as the margin of the hinge. Umbo of the
left valve prominent, gibbous, liiuited by the sulci of the cardinal expansions,
and subtending an angle of from 30° to 00°. Beak of the right valve
depressed, rounded, not rising above the hinge ; umbonal region depressed-
convex, gradually merging into the body of the valve, which is concave below.

Wing large, triangular, nearly flat, varying in proportions, defined (in the
left valve) by the post-cardinal slope; margin concave; extremity acute,
rounded. Ear of left valve a simple rounded convex lobe or auriculation,
defined by a distinct, broad, rounded sulcus ; margin rounded above, sinuate at
its junction with the valve, forming the byssal sinus. The cardinal expan-
sions of the right valve are similar in dimensions to those of the opposite
valve; nearly in the same plane with the body of the shell, and defined
only by the surface strise and the sinus.

!U PALAEONTOLOGY OF NEW YORK.

Test strong, iincrcims, often having a thickness of more than one milli-
iiK'tre. Left valve marked with from six to ten or twelve strong rounded
rays, which originate .at or near the l)eak and continue simple to the margin.
Tlie interspaces are marked bv smaller, alternating costtB, increasing by
interstitial addition as the shell increases in size. The surface is also orna-
mented with strong, elevated, concentric lamellose striae of growth, which are
more or less distinctly bent liaekwards over the stronger radii. The cardinal
expansions an- niarkeil witli rays; ihosv on tlic rai- in well-preserved speci-
iiiciis, are .stronger than on the wing.

Ill the ])artially exfoliated condition, and in the casts, the ears show the
concentric stria? ; and the wings show evidences of the rays. In some con-
ditions the rays are nodose from the concentric laminge, and in older examples
there are undulations of gi-owtli which interrupt the rays and increase their
nodose aspect.

In the right valve tlie surface is marked witli concentric lines which are
more crowded on the cardinal expansions, and with a few strong radii on the
wing, which are sometimes quite obsolete.

The I'asts of the interior sometimes show traces of the stronger radii : luit
usually they are not preserved.

ill the various phases of maceration and exfoliation, the specimens present
gradation from tlic liner railii to the stronger ones, and some specimens are
quite destitute ol surface markings. They vary also in the number of
stronger radii, the development of the wing, the comparative length and
width of the body, the arcuatiou of the valves, the prominence of the beaks,
and the thickness of the test. In rare examples, the stronger ray.s below the
umbo are broken n|i and merged with the finer striae.

Tlie jiallial line originates in a small, deep, anterior muscular impression
just beneath the anterior tooth, and extends nearly })aiallel with the margin
of the valve almost two-thirds the tlistance from the beak to the base of the
shell, where it is aliruptly recurved, terminating in a large, ovate, posterior
muscular impression directly below the posterior extremities of the lateral
teeth.

LAMELLIBRANCHIATA. 95

Ligamental area marked by a variable numlier of sharp narrow grooves,
which extend to the extremities of the hinge-line, and probably correspond
to the successive laminfe of growth.

In the left valve, there are four or five linear, diverging cardinal teeth,
beneath and anterior to the beak ; in the right valve only two or three such
teeth are seen. Two or three linear, slightly diverging, lateral teeth, are
situated below the ligamental area, and posterior to the umbo.

A young symmetrical specimen has a length and height (without the ear)
of 15 mm.; and the greatest extent from the beak to the post-basal margin
is 21 mm. A medium sized specimen is 36 mm. in vertical height; extreme
distance from beak to base 47 mm. ; length parallel to hinge-line 35 mm., and
hinge-line from beak to extremity of wing 38 mm. Another is 46 mm. in
vertical height ; extreme distance from beak to base 52 mm. ; length parallel
to hinge-line 46 mm., and hinge-line from beak to extremity of posterior
wing 56 mm. A specimen of different proportions is 52 mm. in vertical
height; extreme distance from beak to post-basal margin 63 mm.; length
parallel to hinge-line 40 mm.; hinge-line from beak to extremity of posterior
wing 40 mm.

This species in surface ornamentation differs greatly from every other form
below the Carboniferous period, and possesses true pterinoid characters in a
stronger degree than any other species from the New York rocks. The right
valve when detached is not so easily distinguished from some other forms,
as Pterinea Chemungensis and AcUnoptera Boydi.

The species is co-extensive with the Hamilton group throughout the State
of New York. An apparently abnormal form, in its unusually large wing,
(PI. XV., fig. 6,) found in the Chemung group, has been referred to this
species ; and specimens of similar character are common in certain localities.

The specimens occurring in the Chemung group are much larger, and of more
extravagant growth, than any yet observed in the Hamilton group. A large
specimen has a height of 100 mm. ; another measures 90 mm. in length, and is
of equal extent along the hinge-line. The costae on these large forms are often
only four in number and very strong and broad. (See plate Ixxxiii, fig. 11.)

9G PALEONTOLOGY OF NEW YORK.

Formations and localities. This species has been recognized in a single ill-
preserved specimen from the Corniferous limestone, at Staflford, Genesee county,
N. Y. ; casts of the interior, and a single extravagant form preserving the sur-
face characters, have been obtained from limestone of the same age near Col-
umbus, Ohio. It is abuiidaiit in the Hamilton group at numerous localities
from Schoharie to Cayuga lake, more rarely in the western part of the State ;
thougli occuning at Hamburg and elsewhere on Lake Erie shore. It is found
in the upper licds of the Chemung group in Steuben county, N. Y., and Tioga
county, Pennsylvania.

Ptkrtnka intkrstrtaup, n. sp.
rr.ATE i.xxxiv. fh; ■.■■.>.

Shell large: lel't valve (ihliijiiely ovate, narrow above; length and height
nearly equal; anterior and basal margins regularly curved; posterior margin
produced.

Left valve moderately convex, depressed towards base. Right valve
unknown.

Hinge-line straiglit, about equal to tiie length of the shell.

Beak acute, inclined forward. Um})onal region not prominent, narrow,
limited hy the cardinal expansions; subtending an acute angle.

Wing triangular, large ; margin concave ; extremity acute. Ear triangular,
small.

Surface marked by about 20 regular, strong, rounded rays which originate
on the upper part of the umbo and continue undivided to the margin : w itli
broad, flat interspiices marked by from two to four slender, sharp radii, and
crossed by fine concentric stria\ Al)out twelve of the strong rays reach the
margin of the valve below the middle of its height, the remainder come out
on the upper anterior margin. Tiie wing shows tlie radii somewhat less
strong than the body of the valve. The ear is marked by strong radii.

Interior uid<nown.

The specimen described has a greatest length ol' aliout "io mm.; height
nearly 58 mm.; hinge-line from beak to extremity of wing, about 58 mm.

LAMELLIBRANCHIATA. 97

This species somewhat resembles P.flabella; ;ind (lifters in its less convexity,
more numerous strong rays with finer intermediate lines, and less conspicuous
concentric strioe.

Formation and locality. In sandstone of the Chemung group at Chemung
Narrows, Chemung county, N. Y.

Pterinea dispanda.

I'l.ATE XV, FIG. 7.
Ptennea d'l.ipanda. Hall. Pal. N. Y., vol. v, pt. 1. Plates ami E.Nplaiiations : PI. ]"), tii,'-. 7. Jan., 1SS3.

Shell large ; body very In-oadly ovate, nearly erect ; length greater than the
height; anterior margin very convex ; basal margin flattened, not produced
posteriorly.

Left valve regularly convex, and only moderately gibbous on the umbo.
Right valve unknown.

Hinge-line straight, greater than the length of the Ixxly, extended i)os-
teriorly beyond the margin of the valve.

Beak anterior, nearly rectangular, prominent, directed forward. Umbonal
region ample.

Ear small, separated from the body of the shell ))y a broad undefined sul-
cus, which is marked by several oblique folds. Byssal sinus deep and abrupt.
Wing very large, depressed-convex, broad-triangular ; defined by the retral
curving of the concentric strias ; concave on the margin ; extremity
extremely produced and acute.

Test ornamented with strong, unequal, rounded radii, which are some-
times bifurcating on the anterior portion. The wing is marked with similar
smaller rays which are sometimes fasciculate. Entire surface also marked
by concentric lamellose striae, which at irregular intervals are crowded into
fascicles, giving an undulating aspect to the surface, and a low nodose
appearance to the stronger rays.

Interior unknown.

The specimen described has a height of 7(t nun., length about 80 mm., and
the length of the hinge-line about 90 mm.
13

08 PALEONTOLOGY OF NEW YORK.

This slit'll bears some resemblance to the more extravagant forms of Pterinea
flabclla, Imt it is larger than any known specimen of that species, with a ]n(i]tor-
tionallv longer and less defiiicil body, and distinctly dilTcrcnt surface ornamen-
tation.

Formation and localiti/. In tiie upper beds of the Chemung group at Mansfield.
Tioga county, Penna.

Pterinea Chemungensis.

I'l.ATK XVI, FIGS. 3, 7, 10, 12; PLATE LXXXIV, FIU. 21.

Arkula C'litiinunj, ii.-<i.s, Coxrad. Jour. Acad. Nat. Sci., Phila., vol. S, p. 243. 1842.
Anciiln jx'Henifuniiis, Hall. fSeolog-. Siirv. N. Y.: Kept. Fourth Dist., p. 262. 1843.

Pteriiua CheiaimgensU, (Co.nrad) Hall. Pal. N. Y., vol. v, pt. 1. Plates ami Kxplaiuitioiis : PI. 10, fi-rs. 3,

7, 10, 12. Jan., 1883.

Shell very large, rhnuilioidal ; body of shell ovate, narrower jibove, nearly
erect, or sometimes oliii(|uc: IniLitli less than the height; greatest length
below the middle : basal ami post-liasal margins rounded; the anterior
margin above the iniildle is ueai-ly straight. an<l the corresponding portion of
the posterior margin is gently concave.

Left valve moderately convex above, depressed-convex in the lower part.
Right vah c depressed-convex towards the ])eak, flat or slightly concave below.

Ilinge-liue straight, central ; length nearly or quite equal to the length of
the shell.

Beak anterior, acute, directed forward, arching a little over the hinge-line.
Uml)onal regiim not .strongly defined, most jirominent a little below the
hinge ; subtending an acute angle.

Ear short, nearly e(|uilateral. limited by a rounded sulcus ; margin concave,
witli a marked sinuosity and arching of the shell for the byssal sinus. Wing
large, triangular, and extending beyond the posterior margin of the valve, not
distinctly defined by a sulcus or l)y marked change in the surface characters
from the body of the shell ; margin straight or .slighth- concave ; extremity
obtuse. In the right valve, the wing is less distinctly defined than in the
left.

Test .sonicwliiit thin; left valve marked by slendt-r. lililDrni ravs, varionsh

LAMELLIBRANCHIATA. 99

alternating and bifurcating, or sometimes simple from the uml)0 to the liase,
continuing over the wing, and somewhat stronger on the anterior cardinal
extremity than on the posterior ; the interspaces flat, nuich wider than the
rays. The surface is crossed by fine, closely arranged, concentric stria?, which
are occasionally crowded, giving an unequal elevation to the rays. These are
also often interrupted and undulated, either from accident to the shell or
intermittent growth, and are sometimes nearly obsolete at the base. The
right valve is marked by the same interrupted rays on the wing ; on the
body of the shell the radii are obsolete, but the concentric strife are preserved.
The specimens are generally found as casts, or in an extremely macerated
condition.

Ligamental area wide, marked by fine, narrow grooves the whole length of
the hinge. Obscure indications of lateral teeth have been seen.

A left valve is 62 mm. in length, 76 mm. in lieight, hinge-line 55 mm.
Another one has a length of 55 mm., height and hinge-line each 62 mm.
A very large specimen is 85 mm. in height, 102 mm. from beak to post-
basal margin, length 70 mm., hinge-line about 65 mm. A right valve has a
length of 55 mm., height 60 mm., hinge-line about 60 mm.

The form varies from nearly erect to considerably oblique, and is usually
characterized by tlie l)roadly rounded base and interrupted rays, which are
coarse and fine, and irregularly arranged.

•This species reseml)les P. rigida, but the radii lia\e an appearance of less
rigidity, the hinge-area is narrower and the shell is more oblique. It is closely
allied to P. comimilis, differing in the proportionally shorter hinge-line, greater
height of body, and k'ss olilicpiity.

Formation and locality. In the Chemung group at Chemung Narrows, Che-
mung county, N. Y.

1(10 PALJEONTOLOGY OF NEW YORK.

PtERINE.V CONSIMILIS.

I't.ATK XVI, KKiS. 1. 2, S, !l, 11 ; ANI> I'l.ATK I.XXXIV, KKJ. 23.

Plerlnin ciinxliiiUi.1, IIai.i.. Piil. N. V., vol. v, jit. 1. Pliitcs ami Kxphiniitions : PI. l.'i, tip*. 1, 2, S. it, 11.

Jan.. 18S8.

Shki.i, large, sub-vli(iinlii)i(l;il, neai'ly orbicular: k'ligth greater than tlic licidit :
margins regularly curved, moderately produced on the posterior end.

Left valve convex al)0ve, depressed-convex below. Right valve romcx on
the umbo, tlat or slightly concave below.

llinge-line straight, length equal to or a little greater than the length ul'
the valve.

Beak acute, anterior, inc^lined slightly forward, not rising altove the hinge.
Umbonal region prominent hut not strongly liinittMl, sulttending more than a
right angle.

Ear small, liniited by the a1inn)t slope of the umbo, which becomes a dis-
tinct sulcus in till' right valve; margin convex (except in the by.ssal sinus);
extremity rounded. Byssal sinus not distinct. Wing broad, triangular,
undefined, much extended ; margin concave ; extremity acute.

Surface of left valve marked by numerous flattened, slender, filiform rays,
with broad, flat interspaces, which are marked by one or two, more or less dis-
tinct, finer rays. The radii are often undulating, and become obscure towards
the base. The cardinal expansions are correspondingly inaiked. Fine, closely
arranged, inconspicuous concentric striae cross the sm-face. The wings of
both valves are similar in surface characters. Tlic body of the right valve
shows the concentric striaj, with obscure indications of rays.

Ligamental area broad, marked by fine parallel grooves the entire length.
Lateral teeth two, strong, converging. Cardinal teeth preserved as three short
plications under the beak of the left valve. Pallial line simple, originating
anterior to the beak, continuing nearly parallel to the margin of the valve,
recurving and terminating in a large muscular scar on the post-cardinal .slope
juljacent to the wing.

A left valvi' has a length of 02 mm., height 49 mm., hinge-line about 50

LAMELLIBRANCHIATA. 101

mm. A right valve has a length of 46 mm., height 40 mm., hinge-line
48 mm.

This species difiers from P. Chemungensis in being shorter, proportionally more
extended on the hinge-line, with wider ligamental area, more distinct radii,
and greatly difterent proportions of length and breadth, as shown in the right
valves.

Formation and localities. In the Chemnng group at Buck's quarry and
Chemung, Chemung county, and Smithboro, Tioga county, N. Y.

Pterinea rigiua.

PLATE, XVI, FIGS. 5, G.
Pterinea rig'ida. Ham,. Pal. N. Y., vol. v, pt. 1. Plates ami Explanatioiis : PI. Hi, tifjs. 5, tj. Jan., 1S83.

Shell of medium size, su))-rhomboidal, erect; body ovate, narrow al)ove ; length
somewhat less than the height ; margins regularly rounded, slightly extended
on the post-basal portion and straight along the posterior side.

Left valve moderately convex above, depressed-convex below. Right
valve unknown.

Hinge-line straight ; length about equal to tlie length of the valve.

Beak acute, prominent, directed forward, rising to the hinge-margin.
Umbonal region elevated, subtending an acute angle.

Ear small, limited by the moderate byssal sinus and broad sulcus. Wing
large, broad-triangular, undefined ; margin slightly concave ; extremity
angular.

Surface marked with about thirty slender, rigid, rounded rays, which are
sometimes flat or grooved along the summit, continuous from the upper part
of the umbo ; with wider flat interspaces which sometimes show a fine
intermediate ray coming in below the umbo. The cardinal expansions are
marked by rays of the same character. Lines of growth cross the surface.

Interior unknown.

A medium sized specimen has a length of 31 mm., height 34 mm., hinge-

101^ PALEONTOLOGY OF NEW YORK.

lim- altout ;-)5 mm. ' A smnlli'r s])ocimen is 2(i nun. in k'ugtli, 25 mm. in
liciiilit. liiiiuv-liiic 2 1 mill.

Tliis species l)ears a general re.semblance to P. Chemungensis ; it ditiers in
its continuous and comparatively stronger rigid radii. The group oi" four species,
beginning with P. Chemungensis, is well marked and have many characters in
common; Imt nevertheless, present diilerences which warrant their specific
separation.

Formation and localities. In the (Jheuiuiig group, at several localities in
Chenumg county, N. Y.

Ptkrinea prora.

I'l.ATK XVI, KICiS. 4, 13, 14.

PteriHin jimia, IIai.i.. Pal. N. \.. vol. v, i)t. 1. Plat«.< iiiid Kxplaiiatidiis : I'l. U',. tiys. 4, Ki. U.

Jan., 1883.

Siii'.i.i, ol' iiu'iliiiiii size or larger, sul)-rhomboidal, oblique; body o\ati', narrow
above; length one-tburth greater than the height ; inargiiis I'eguiarly rouiuh'd,
extended on the jwst-basal poitioii and sloping i-apidly into tlie .'<iniis ol' the
wing.

fjeft valve moderately convex. Uight \alve depressed-convex aliovi', flat
or concave below, apparently smaller than the lel't.

Hinge-lino straight, longer than the length of the valve, and extending
beyond both margins.

Beak small, acute, directed forward, situated at about the anterior liftii of
tlie hinge. Unibonal region undefined, not prominent.

Ear about one-fil'tli tlie length of the wing, se2)ai'ated from tlie bodvofthe
\al\e iiy a sliallo\A undefined sulcus and marked b\ssal sinus; margin con-
vex; extremity rounded. Wing large, triangular, extended, defined onl\ bv
the change in the curvature of its margin from that of the boilyof the \al\e;
margin deeply concave; extremity acute.

Surface of left valve marke(| with regular, rounded, ''sub-ecpial rays, with

LAMELLIBRANCHIATA. 103

flat interspaces which are sometime.s marked by intermediate rays; crossed
by fine, concentric lines of growth. Tlie cardinal expansions of both valves
show the same character of radii as the body of the left valve. The right
valve has subdued rays in the lower posterior portion ; the upper part shows
only the concentric markings in regular lamellaj of growth.

Interior unknown.

One specimen is 34 mm. in length, 28 mm. in height, hinge-line 44 mm.
Another is 38 mm. in length, 32 mm. in height, hinge-line about 47 mm.

This species has a resemblance to the left valve of P. avis ; but the left valve
of the present species has greater convexity, more extended hinge-line, and a
broad, deep sinuosity in the margin of the wing.

The large right valve repi-esented in fig. 4, of plate xvi, is referred with doubt
to this species on account of its greater size. This specimen shows a large,
broad, elliptical muscular impression near the middle of the post-cardinal slope of
the valve.

Formation and localities. In the Chemung group at Buck's quarry near
Elmira, an<l Chemung Upper Narrows, Chemung county, N. Y.

The three following species have the right valves convex, and the left valve
nearly flat or concave, being the reverse, in this respect, of the preceding
species of the group. The hinge-area is narrow and teeth have not been
observed, while the surface markings are peculiar and characteristic in the
three forms here described. For these reasons I have considered it desirable
to distinguish them, for the present, under a sub-generic head.

1U4 PALEONTOLOGY OF NEW YORK.

VERTUMNIA, n. s. g.
Pterinea (Vertumnia) keversa.

I'l.ATK XXIV, FIGS. G, li ; AND I'l.ATK I.XXXIV, KIU. U.

PUriiiea rrirrxa, Hai.i.. Pal. N. Y., vol. v. jit. 1. Plates and Kxplanatioiis : PI. 24. Hi.'-.-;. H, 12.

Jan., 1883.

SiiKi.L large, rhomboid-orlncular ; l)0(l_v soiiicw liat oMique; Iciigtli ami licight
nearly equal; margins regularly rouiidiMl, a little more extemlcil on the pos-
terior side.

Left valve flat, or .slightly concave, except near the iiniho. Right \al\e
moderately convex, the greatest convexity ahoiit the inidillc of the lici-iit.

Hinge-line .straight, length ('(inal to the length ol' the valve, e.xteiiding
anteriorly beyond the margin.

Beak of left valve depressed, obtuse, undelineil, erect. Beak of right valve
low, obtuse, iiH lined forward. Umbo not distinct in either valve.

Ear of the right valve limited by a distinct broad byssal sinus. Wing
triangular, undefined.

Surface marked by strong, rounded, sinij)le, continuous radii which
originate upon the umbo; with wide. Hat interspaces, which, in tiie right
valve, show occasionally a finer ray; crossed by regularly arranged, sharp,
concentric striae, which are conspicuous both on the rays and interspaces.
The rays are obscure and distant on the upper part of the cardinal expansions.

A large right valve has a length of 5() mm., height 47 mm., hinge-line
0-5 mm.

This species differs IVnni /'. prora by its lesser obliquity, the indefiniteness of
the cardinal expansions, the convexity of tlie right valve, and the liat or con-
cave character of the left valve.

Formation and locality. In the Chemung group near Elmira, at the L'j)2Jer
Narrows of Chemung river, N. Y., and in Tioga count}^ Pa.

LAMELLIBRANCHIATA. 105

Pterinea (Vertumnia) avis.

PLATE XXIV, FIGS. 9, 11, 13.

Pterinea reversa, !'«;•. aris. Hall. Pal. N. Y.. vol. v, lit. 1. Plates anJ Exjilanations : PI. 24, tigs, fl, 11,

18. Jan., 1883.

Shell of medium to large size, rhoinboidal, oblique ; body ovate ; length greater
than the height ; margin moderately rounded in front, becoming full on the
posterior side.

Left valve depressed-convex above. Hat or concave below. Right valve
convex ; the greatest convexity about the middle of the valve.

Hinge-line straight, length greater than the length of the sliell, extended
anteriorly beyond the margin of the valve.

Beak low, obtuse, inclined forwai'd, situated on the anterior third of the
hinge-line.

Cardinal expansions uneciiial, triangular. Hat; margins concave; extremities
mucronate. Ear limited by a broad, shallow sulcus extending from the beak
to the rounded byssal sinus. Wing large, undefined.

Surface of both valves marked by about twenty-five strong, rounded, equal
raya, reaching from the uinl)0 to the base, with broad, fiat interspaces which
occasionally show a single fine intermediate ray. The same surface
characters extend over both cardinal expansions. The entire surface is
marked by fine, regular, sharp, continuous, concentric strise.

Internal characters unknown.

A left valve, illustrated on plate xxiv, fig. 13, has a length of 44 mm.,
height 31 mm., hinge-line 49 mm. A large right valve has a height of
45 mm., length 65 mm., and hinge-line about 65 mm.

This species resembles P. reversa, but differs in its com2:)aratively greater
obliquity, more extended hinge, and proportionally greater length. It differs
from P. prora in the flatness of the left valve, the strong rays, the sharp
elevated striae, and the convexity of the right valve.

Formation and locality. In the Chemung group at Buck's quarry, near Elmira,
Chemung county, N. Y.
14

loG PALEONTOLOGY OF NEW YORK.

Pterinea (Vertumnia) iu:i'K(ii!a; h. s}).

IM.ATK I.XXXII, FIGS. 10,20.

Shell of luediuiii j^izc, I'liomhoidal ; body ol)li(jiie ; Iciigtii soiiu'wliut p't-atcr lliaii
the height ; pallial margin reguhirly rounded, Ijecoming produced behind and
extending tlience in a nearly direct line to the hinge.

Valves depressed-convex, the right valve the more convex; very similar
in form and surface markings.

Hinge-line straight, length greater tliaii tlie greatest length of the sliell,
extended anteriorly considerably beyond the margin of the valve.

Beaks obtuse, not jjrominent, directed forward, anterior to the iiiiildlc.
Umbonal region undefined.

Ear defined by a shallow sulcus : uiariiin concave : extreniitv acute. T5yssnl
sinus moderate, marked in the rii^lit \al\i' hy a |)artial reflexion of the mar-
gin. Wing large, triangular and undefined; margin nearly straight lielow,
slightly concave toward the extremity, which is acute.

Surface marked by numerous strong, rounded lays. which alternate on the
left valve, and (ln|ilicate on the right valve. The interspaces are e(iual to,
or greater tliau, the radii : the rays are liuer on the cnidinal expansions, and
very obscure on the ear and umbonal region ol' the right valve. Concentric
striae regular, sharp.

Interior not known.

Ligamental area narrow, and marked l)y one or two longitudinal furrows.
The sharp stria) in their extension over the hinge-margin give the exterior
a crenulated appearance.

A left valve has a length of 25 mm., height 22 mm., liiuge-line .'id mm.
A right valve has a length of 36 mm., height 28 mm., hinge-line 37 mm.

This species differs from Pterinopeden Vertumnus hy its comparatively
longer hinge-line, more extended ear, less distinctly curving, narrower, anil
more abruptly elevated radii on the left valve; and stronger, not undulating,
duplicating radii of the right valve. The form and proportions are similar to

LAMELLIBRANCHIATA. 107

Pterinopecten latus, l)ut it is a larger and coarser form, with the right valve con-
vex. The geological positions of the two species are quite different. The
character of the surface ornamentation distinguishes it from Pterinea prora and
Pterima avis.

Formation and locality. In shales of the Chemung group, 600 feet above the
base of the formation, at Ithaca, N. Y.

ACTINOPTERIA, Hall.

ACTINOPTERIA EXIMIA.

ri.ATE XXV, KIG. 1.

Actinopteria exiiiiia. Hall. Pal. N. Y., voL v. pt. 1. Plato.'; and Explanations: PL 25, tig-. 1. Jan.. 18S3.

Shell small, rhomboidal ; body falciform, very oblique ; length more than one-
third greater than the height; margin broadly curved along the ventral
side and abruptly recurved over the posterior end.

Left valve convex. Right valve unknown.

Hinge-line straight, less than the length of the valve.

Beak acute, directed forward. Umbonal angle about 00'^.

Ear short, oblique, limited by a distinct sulcus ; margin convex ; extremity
rounded. Wing imperfectly preserved in the specimen described, apparently
joining the body near the middle of the post-cardinal slope, and very .strongly
defined ; margin concave, extending acutely backwards ; extremity acute.

Test marked by al)out twenty strong, elevated slender rays, with regular
. lamellfB of growth which are extended and bent backwards on crossing the
rays, producing strong semi-tubular spines. The cardinal expansions pre-
serve only the lines of growth.

Interior unknown.

The specimen described has a length of 20 mm., and height of 14 una.

The description is made from the figure given on plate xxv, as the specimen
cannot be found at the time of this writing. The characters of form and surface
ornamentation are very characteristic, and the species is important as being the

108 PALEONTOLOGY OF NEW YORK.

only one ut' the genus yet I'uuud in the Schohurie grit. It diflers Iruni
A. mvricata in its narrower and more oblique body and shorter wing, as
measured along the post-cardinal slope.

Formation and locality. In the Schoharie grit, at Schoharie, N. Y.

ACTINOPTERIA MURICATA.

PLATE XVII, FIGS. 1-3.

Av'irida iniir'uata, II.ti.L. Geol. Siu-v. N. Y. : Ri'j). Fourth Di.st., ji. ISl. 1S43.

Ptenmites murivatun, H.ii.l. Cut. Am. Pal. Foss. : S. A. Miller, i>. 202. 1877.

Actijiopteria muricala, }l\i.\.. Pal. N. Y., vol. v, pt 1. Plates and Explanations : PI. 17, lif.'-s. 1-3. Jan., 1S83.

SiiELi- small, sub-rhomboidal : body sub-ovate, very oblique ; length one-third
greater than the height; margin rounded below, turning abruptly backward
on the posterior side, and extending in a direct line to the beak.

Left valve convex, llight valve unknown.

Hinge-line straight I'rom the beak to the po.sterior extremity, .-^loping
downward on the anterior side; entire length greater than that of the body
ol" the shell.

lieak acute, arching over the hinge, inclined I'orward, situated at the
anterior third of the hinge-line. Umbonal region subtending an acute angle.

Ear broad-triangular, separated from the body of the shell by a broad
undefined sulcus which is limited by a strong sub-angular fold extending
from the beak, and by the deep rounded byssal sinus ; margin convex ;
extremity obtuse. AVing flat, triangular, defined by having more subdued
surface rays; margin deeply sinuate; extremity mucronate.

Test thin, marked with from eight to twelve strong, filiform rays, with
finer intermediate ones in the broad, flat interspaces. The rays on the wing
are somewhat subdued. Surface crossed l)y fine concentric lines of growth,
which, at intervals, are crowded and raised into lamellae, and on the rays are
produced into tubular spines. These spines are seen only in the better pre-
served specimens, and appear in the casts as elongate elevations upon the
rays. The concentric strise are conspicuous in the anterior sulcus.

Interior unknown.

LAMELLIBRANCHIATA. 109

Ligamental area grooved.

The largest specimen has an entire length of 16 mm., height 10 mm.,
hinge-line, to the imperfect posterior extremity, 12 mm. A smaller speci-
men has an entire length of 14 mm., height 9 mm., hinge-line 15 mm. The
smallest specimen measures 10 mm. in length of body and hinge-line, and
6 mm. in height.

In form and surface characters this species is quite unlike any other described
from these rocks. In some respects it resembles A. eximia, fig. 1, pi. xxv ; but
has more extended wing and less elongate body.

Formation and locality. In the Marcellus shale at Littleville near West Avon,
Livingston county, N. Y.

ACTINOPTERIA DoRIS, n. Sp.

PLATE XVir, FIG. 4.

Arl'mopteria LeamJer, Hai.l. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 17, fior. 4. J.in., 1883.

Shell small, sub-rhomboidal ; body obliquely sub-ovate ; length a little greater
than the height; margins regularly rounded, sloping abruptly from the
upper part of the posterior side to the Ijeak.

Left valve depressed-convex. Right valve unknown.

Hinge-line straight, about equal to the length of the shell (imperfect in the
specimen described).

Beak depressed, inclined forward, situated at the anterior third of the
hinge. Umbonal region not defined, subtending an acute angle.

Ear not observed. Wing large, flat, not distinctly defined ; margin concave ;
extremity acute.

Test thin, marked by regular, equal, rounded radii, with wider flat inter-
spaces, and sometimes with obscure intermediate rays. The wing shows
finer rays, somewhat crowded at its junction with the body. The fine, con-
centric lines of growth are stronger on the anterior of the valve, giving a
cancellate aspect to the surface.

110 PALAEONTOLOGY OF NEW YORK.

Interior unknown.

Ligamental area with one or two lonjritudinal grooves.

Tlic s]iccimcn lias a hMiQth of IS mm.. liciL'ht IH mm.

Formation and locality. In the Marcelhis shale at East Bloomfield, Ontario
countv, N. Y.

ACTINOPTERIA SUBDECUSSATA.
I't.ATK XVII, KIGS. 23, iV-aT. 29-.'!l ; and PLATE XIX. KIG. IV

Plertmites siMtciuisala, II.vll. MS., vol. v. 1877.

" . •• S. A. Miller in Cat. Am. Pal. Fo.s.«., p. 202. 1877.

AitlnophrUi .Kuhdtcnj<.ini(i. Ilvi.i.. Pal. N. Y., vol. v, pt. 1. Plates and Kxplaiiations : PI. 17, tig-s. 23, 25-

27. 2!l-31 ; 1)1. 111. tij,'. 2.'). .Jan., 1S83.

Shell hirge, siili-ilinmboidal, ver\' oblique; body elongate sub-ovate ; height
al)uut oiic-tliinl less than tlic Icuutli ; margins regularly curved, becoming
more extended on the posterior side.

The left valve, in old specimens, has the umbo convex above, depressed-
convex or flat below, while in young specimens the umbo is altogether con-
vex or gibbous. Might valve moderately convex near the umbo, tiat or
concave below the middle.

Hinge-line straight, length about one-fifth less than the length of the shell,
not extending as far as the posterior margin of the left valve, hut extending
beyond the posterior margin of the right ^ alve.

Beak acute, directed forward, somewhat prominent, anterior nearly
terminal. Umbonal region (in young shells) well marked by the sulci ;
umbonal angle acute.

Ear very small, separated by a vertical sulcus. Wing large, triangular,
defined in young shells by the abrupt convexity of the post-cardinal slope ;
in old specimens not distinctly defined ; margin concave ; extremity acute.
The wing of the right valve is larger, and extends beyond the margin of the
shell.

Test comparatively thin, marked with regular, sub-angular, alternating radii,
the stronger ones extending from the summit of the umbo; a second set interca-

LAMELLIBRANCHIATA. Ill

lated on the lower part of the umbo, and a third set of smaller rays coming
in toward the margin. The first and second series only are shown in young
shells. In the right valve the radii are more subdued. The rays extend
over the cardinal expansions of both valves in neaidy uniform size. Concen-
tric, elevated, regularly rounded striiB of growth cross, the rays, and cancel-
late the surf\ice, and at intervals are crowded together, giving it a lamellose
aspect.

Interior unknown.

Ligamental area marked by one or two parallel grooves.

A large specimen has a length of 65 mm., height 47 mm., hinge-line 55
mm. A specimen of medium size has a length of 51 mm., height 35 mm.,
hinge-line 41 mm. A smaller example has a length of 18 mm., height 11
mm., hinge-line 13 mm.

This species is similar in form to A. decussata, but differs in the convexity of
the valves and the less strongly decussated character of the ornamentation, the
rays being continuous and annulated by the concentric striae, while in that species
the rays are interrupted by strong concentric lamellae, between which are the
finer lines of growth.

This species is also less aljundant and more restricted in geographical range.

Formation and localities. In the shales of the Hamilton group on the shores of
Canandaigua lake, and near Bellona, Yates county, N. Y.

ACTINOPTERIA DECUSSATA.
PLATE XVII, FIGS. 24, 28 ; PLATE XVIII, FIGS. 1-15 ; PLATE XX, FIG. 19 ; AND PL.A.TE LXXXIV, FIG. 4.

Ai'ienla deciixsnta. H.\ll. Geol. Surv. N. Y. : Rep. Fourth Dist., p. 203. 1843.
Phronites decaumta. Hall. S. A. Miller, Cat. Am. Pal. Foss., p 202. 1877.

Actliioptti-ia decussata. Hall. Piil. N. Y., vol. v, pt. 1. Pla!e.s and Explanations: PI. 17, fig-.-^. 24, 28; pi.

18. fig-s. 1-1.'). Jan.. 1883.

Shell large, sub-rhomboidal ; body sub-ovate, very oblique ; length al)out one-
fourth greater than the height; margins regularly curving; the anterior
margin sometimes nearly vertical ; posterior margin more abruptly rounded.

12 PALEONTOLOGY OF NEW YORK.

Valves convex ; the right valve less convex and smaller than the left valve.

Hinge-line straight, less than the length of the valve.

Beak aeiite, prominent, inclined forward, close to the anterior end of the
shell, rmbonal region prominent, and in the left valve gibbous; subtending
an acute angle.

Ear small, separated from the valve by a broad sulcus, beyond which it is
a iHcrc liild ill the shell. Wing large, triangular, flat, extending nearly to
the margin of the valve; limited, in the left \;ilve, liy a inore or less dis-
tinct sulcus, and the abrupt bending of the concentric strias ; margin con-
cave; extremity acute. This character of the wing is somewhat less marked
in the right valve.

Test thick ; the left valve marked with strong, prominent, rounded radii,
regularly alternating with finer ones on the posterior half of the valve;
crossed at regular intervals by strong concentric lamellae ; the inter.spaces
marked l)y fine lines of growth. From maceration or exfoliation these
surface characters are usually only partially preserved, or nearly obsolete.
In certain conditions the rays become nodose where crossed by the lamellae,
and in many examples the concentric striae interrupt the rays, leaving them
alternating above and below the lamella}. (See pi. xviii, figs. 13, 14.)
The surface characters of the body are continued on the wing, while on
the ear the concentric striae are ci'owded and conspicuous, and the rays
obsolete. In the right valve the markings are much subdued, the rays often
obsolete, especially on the lower part of the valve, and the concentric Innielhv
are simple undulations of the surface.

Ligamental area narrow, linear ; marked, apparently, by a single groove.
The cast shows a fold corresponding to the sulcus limiting the wing. Pallial
line extending from just anterior ami below tlie uinlio to the posterior portion
of the body and thence recurving, terminating in a small oval nuiscular impres-
sion. No evidences of teeth are seen in the casts or the interior of valves.

A large spt'cimen lias a length of 7ti mm., height 56 mm., hinge-line 62
mm. A medium sized example has a length of -52 mm., height 43 mm.,
hinge-line 42 mm.

LAMELLIBRANCHIATA. 113

This form differs from A. subdecussata in the greater and nearly equal
convexity of the valves, the stronger, rounded rays, and their interruption hv
the concentric lamellae.

Forination and localities. In the Hamilton group, at numerous places in
Central and Western New York.

ACTINOPTERIA BoYDI.

PLATE XIX, FIGS 2-24, ■26-.30 ; AND PLATE LXXXIV, FIGS. 16, 17.

AiHciila Boydil, Conrad. Jour. Aciul. Nat. 8'-i., Pliila., vol. viii, ji. 237, pi. 12, tig-. 4. 1S42.

PUi-inea Boydi, Conkad. S. A. Miller in Cat. Am. Pal. Fo.ss., p. 201. 1877.

Avicula quadrala, Conkad. Jour. Acail. Nat. Sci., Phila., vol. viii, p. 243, pi. 13, tig. 5. 1842.

Aetlnoptena Boydi, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 19, figs. 2-24, 2(i-30 ; pi.

23, fig-s. 5. B. Jan., 1883.
Compare Avinda pKrohliqiia, Conhad. Jour. Acail. Nat. Sci., I'liila., vol. viii, p. 235, pi. 12, tig-. 1. 1842.
" " plfumptrra. Conr.^d. " •• •■ ■■ •• p 242. pi. 13. tig-. 2. 1842.

Shell of metHuni size, I'lioiiilioidid ; body ovtite, varying in proportions, the
longitudinal axis at an angle with the hinge-line of from 45° to 60° ;
length varying from nearly equal to one-fourth greater than the height ;
margins regularly rounded below, straight aixl nearly vertical for a short
distance in front; post-basal side extended.

Valves convex, the right valve a little less convex tliaii the left.

Hinge-line straight from the anterior side of the beak to the posterior
extremity.

Beak anterior, acute, prominent, inclined forward, rising above the hinge
in the left valve. Umbonal region prominent, subtending an acute angle.

Eiir short, oblique, limited by a deep but not sharply defined sulcus. Wing
large, triangular, not distinctly separated from the body of the shell ; margin
concave; extremity acute. In the right valve the ear is somewhat more
extended, the sulcus not strong, but the byssal sinus is marked ; the wing
is proportionally larger and usually more acute at the extremity.

Test thick ; the left valve, in well-preserved specimens, is marked by
numerous strong, simple, sharp rays, which are continuous from the umbo to
15

114 PALAEONTOLOGY OF NEW YORK.

till' iiiartiiii. with rarely intercalated finer rays; crossed by regular, sharp,
elevated, com;entric lamelltc which (in j^ood specimens) are produced into sul)-
tubular, spiniform extensions wynm the rays. Lines of growth are seen
between the lamelhv. On the \\ in^ the rays are more subdued while the
concentric lamelhv are strong. The ear is marked only by the crowded con-
centric striiv. On the right valve the radii are ()l)solete on tiie IhhIv and
well-marked on the wing, and the lamellose expansions are conspicuous. In
some casts they appear as undulating elevated hiniellai.

Pallial line extending parallel to the niari:in of the shell and terminating
in a muscular impression on the posterior slope. A small muscular impres-
sion is also seen just in front of" the beak, and obscure indications of one or
two cardinal teeth.

Ligamental area narrow, striated, marked by two or three sleniler grooves,
which are slightly divergent from the hinge-line.

One of the original specimens of A. quadrula (=^-4. Boydi) has a length of
30 mm., height and hinge-line each 28 mm. A similar specimen has a
length of 25 mm., height and hinge-line each 2o mm.

Two large specimens belonging to the group of A. Boydi have the follow-
ing respective dimensions: length 38, and 40 mm., height 38, and 3-> mm.,
hinge-line 34, and 30 mm.

This species, in older specimens, resembles A. suhdecussata, but differs in the
character ol' the rays, in the less obliquity, and the wider body. The left valve
somewhat resemliles the right yalve of Avicula recticulata, Hisinger, but a com-
parison of the right valves of both species shows them to lie diU'erent.

The forms here classed under one specific designation were descrilied by Mr.
Conrad under difterent species, viz. : Avicula Boydii, A. quadrula, A. pleuroptera,
and probably A. perobliqua.

The species in its various stages of growth and state of preservation presents a
great variation in form and surface characters. The usual condition is that of casts
ol"the interior or specimens more or less exfoliate<l. leaving the surface markings
sul)(lueil or olisolescent, and in a few specimens onl\'. ha\-e the entire characters
of the test in either or Imih \al\es lieen observi'il. The older specimens show

LAMELLIBRANCHIATA. 115

an extension of the shell along the post-basal margin which is marked by
concentric striae and undnlations, while the rays l)ec()me interrupted and obsolete.

After a study and comparison of a very large number of individuals, it has
not been fovmd jJossible to draw any satisfactory line of specific distinction.
The figures on plate xix illustrate all the important varieties of form that have
been observed.

The specimens illustrated in figures 2, -I, 4 of plate xix, represent the typical
form of A. quadrula, Conrad; the figures 9, 10, 11 of the same plate more
nearly correspond to the A. Boydii, Conrad. All the right valves show the same
degree of convexity and the same surface characters, and vary in form no more
than the variations i]i the left \alve. The extreme forms seen in figures 2() and
27 are old shells, showing the irregular growth of the margins, leaving the upper
portions of the shell of normal form and surface characters.
The following are Mr. Conrad's descriptions:

" Avicula Boydii, pi. 12, fig. 4. — Su))-rhond)oidal, compressed, lower valve
" with numerous radii, disposed to be interrupted by concentric lines, which
" are fimbriated, or have numerous angular indentations; anterior wing short,
" sinuous, truncated; |)osterior wing ample; postei'ior exti'cmity of the valves
" acutely rounded."

"Avicula quadrula, pi. 13, fig. 5. — 8u))-(pia(li-atc' ; length and width equal,
" compressed ; lower valve piano-con \ex, with distant radii of equal size,
" crossed by concentric lines ; posterior wing rather shorter than the width of
" the shell ; anterior wing triangular, beneath which the margin is direct before
" rounding to the beak."

The unrecognized form is indicated as follows :

" Avicula pleuroptera, pi. 13, fig. 2. — Lower valve sub-ovate, ventricose, with
" obsolete radii ; summit of umbo above the cardinal line ; anterior wing very
" short ; the posterior wing produced, rostrated, acute, with an oblique rib or
" carina on tlie posterior half, extending to the acutely angulated extremity."
The oblique rib or carina mentioned was pioliably one t)f the lateral teeth as
shown in figure 12, plate xix.

The Avicula angustirostra of Conrad, cited as occuiTJug at Middleville, Schoharie

lie, PALAEONTOLOGY OF NEW YORK.

coiintv, is probalily IVoin the ILiiniltou slialcs at Fultonham ^ and the only
species from tliis locality, answering the description uiven, is A. Boi/dii. in
a condition in w liicli the i-adii and elevated concentric lamellae are more con-
spicnous than in an}' specimens from Cazonovia. Hamilton, or any other locality
in Central New York.

Formation and localities. In the shales of the Hamilton i;rouj) ; aluuulant at
nnmerons ])laces in the eastern and central portions of the State.

ACTINOPTERIA PEROBLIQUA.

PLATK XIX, KKi. :il ; I'L.VTK I.XXXIV, FJG. H.

AiHcida i>eriihru{ua, CoXK.\i). Jour. AcaJ. Nat. Sci., Pliila., vol. viii, p. 'I'ia, p\. 12, tig-. 1. 1S42.
Aclbuiptcria perubliqiia, (Conkad) Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 19, fig-. 31.

Jan., 1883.

SiiKLLof medinm size, suli-rhomhoidal ; body very oblique, narrow-ovate: leiiiith
one-third greater than the height ; anterior margin truncate or slightly con-
cave; basal margin regularly arched and acutely roundcfl over the post-basal
side.

Valves very convex. Left valve gijjbous in the upper part, angular along
the post-cardinal slope. Right valve somewhat less convex.

Hinge-line straight, about two-thirds the length of the shell.

Beak anterior, acute, prominent, inclineil forward. l^mbonal region
gibbous, subtending an acute angle.

p]ar :i small lobe, defined by a distinct sulcus and shallow, elongate, byssal
sinus. Wing large, triangular, limited ly the angular post-cardinal slope
of the valves ; margin moderately concave, sloping forward ; extremity
anguliir.

Test (as seen in the specimen, which is a partial east of the interior),
marked by irregular concentric striiv, which become fasciculate on the wing;
the surface apparently without rays.

Muscular impression large, sub-quadrangular below the middle of the post-
cardinal slo[)e, from which, the pallial line cur\ing downward below the

LAMELLIBRANCHIATA. 117

middle of the valve, extends parallel with the margin to the anterior side of
the umbo.

The specimen described has a length of 37 mm., height 24 mm., hinge-
line 27 mm.

This specimen occurs associated with A. Boydi and other allied forms, and is
known by the convexity of the valves, the sub-angular character of the posterior
slope of the left valve, the great obliquity, the proportions of length and height,
and the absence of radii in the cast.

Mr. Conrad's original description of A. perobliqua is as follows :

" Avicula perobliqua, pi. 12, fig. 1. — Oliliquely sub-ovate, with radiating lines
" distinct only on the posterior side ; dorsal line rectilinear, long and very
" oblique ; anterior wing short, wide, sinuous, the front margin inclining to a
" regular arch ; posterior extremity acutely rounded.

" Locality — Hamilton, Madison county, N. Y. ; Upper Silurian shale.

" A common species, very easily distinguished from others of the genera
" with which it is associated, by its long, very obliquely ovate outline. Casts
" of the interior scarcely exhibit any radiation. It is often found with connected
" valves."

The radii mentioned in this description cannot be recognized in the specimen
which preserves only concentric striae on some parts of the surface. Mr.
Conrad's description may have included casts of A. Boydi, which show slight
traces of radiation, and occur in the same association.

Formation and locality. In the shales of the Hamilton group, Cazenovia,
Madison county, N. Y.

ACTINOPTERIA PUSILLA, n. sp.
PLATE LXXXIV, FIG. 3.

Shell small, sub-rhomboidal ; body ovate, very oblique ; length and height
nearly equal ; margin for a short distance on the anterior side nearly vertical,
broadly rounded along the base and produced on the posterior side.

118 PALEONTOLOGY OF NEW YORK.

Kijrlit valve convex on tlie uiulx), liecoming depressed below the middle of
the leiifitli. I.elt \;dve unknown.

Ilinjie-line straiglit, less than the length of the shell.

Beak anterior, acute, moderately prominent, rndiomil icuion scarcely'
gibbons, subtendini;' an acute au,<;k'.

Wini:- narrow, triangular, elongate, extending nearly to the posterior end
oltlie shell; margin concave; extremity abruptly acute.

Test thin, marked by elevated, sub-imbricating concentric bands, piodiued
bv the lamello.se character of the stria*. Crossing these bands, on the
posterior half of the shell, are interrupted radiating lines, which indicate the
presence of radii upon tiu' original surface. The wing is marked in a
similar manner by strong liands. w hicli ])ass over the hinge-margin, and it
also shows two or three interrupted radiating lines, like tiiose on the poste-
rior part of the body of the shell.

Interior unknown.

The specimen described has a lengtli of 11 mm., height 12 mm., and
hinge-line Id mm.

This .species is allieil to A. decussata and A. Boijdi, having the wing charac-
teristic of the former; but it is a proportionally shorter foi'm. and the
surface nuirkings are ((uite unlike the right \alveof any of the forms at present
known.

Formation and locality. In shales of the ILimilton group, on the shores of
Canandaigua lake, N. Y.

Al'Tl.NOl'TEra.V rEUSTllIALlS.
IM.ATK XXm, KIti.S. i, 7; and I»r,.\TE LXXXIV, KIC \>.

AitiiuipUriii pirxtiialix, II.m.t.. Pal. N. V., vul. \, jit. 1. Plates ami I'",Niil.ni:iliiMis : PI. •.':>. liirs. J, 7.

Jan., ISS:^.

SiiKi.i. small, sub-rhond)oidal ; body sub-ovate, axis slightly curved and ol.li(pie
at an angle of about 45" with the liinge; height al)out three-fourths the
length of the l)ody; basal margin l)roadly rounded; posterior margin aluuptly
curved.

LAMELLIBRANCHIATA. 119

Left valve regularly convex, moderately gibbous at the umbo. Right
valve depressed-convex below, more convex above.

Hinge-line straight, length equal to the length of the body.

Beaks sub-anterior, in the left valve prominent and rising alcove the hinge ;
in the right valve the beak extends to the hinge-line. Umbonal region
moderately gibbous in the left valve, convex in the right, subtending nearly
a right angle.

Ear short, separated from the body by a marked byssal depression ; extrem-
ity rounded. Wing narrow, triangular, joining the body midway between the
beak and the posterior extremity, not distinctly defined ; margin concave ;
extremity produced and acute. The right valve is less distinctly auriculate
in front ; the anterior extremity acute ; the wing is larger and the margin
less abruptly concave.

Test thin, marked l)y fine concentric stritv which are more conspicuous and
equidistant on the right valve. The left valve is marked with fine, closely-
arranged radii, which are strongest on the upper margin of the wing. The
body of the right valve shows only sharp, distant, concentric stria? ; the wing-
is marked by a few rays in the lower part, and by stronger radii along the
hinge-line, which are cancellated by the concentric stria?. The auricle is
radiated, and cancellated in the same manner.

Interior unknown.

A left valve has a length of 13 mm., height 10 mm., and hinge-line 12 mm.
A large right valve has a length of 15 mm., height 1"! mm., and hinge-line
15 mm.

Tliis species differs from A. tenuistriata in its more oblique l)ody, compara-
tively longer hinge-line, and more closely arranged and stronger radii.

Formation and locality. In the lower part of the Chemung group, near
Ithaca, N. Y.

120 PALjEONTOLOGY of new YORK.

A("TlNOI'Ti:i;iA TKNUISTllIATA, II. sp.
ri. \ TK I.\\\I\ . K1(;S. 5, G.

Shkll small, .^uli-quadrate ; boily short-ovatr, ()l)li((U(' at an angle of 60" with
the hinge ; length ahout (»nc-lirtli greater than the height; anterior margin
below the sinus nearly vertical, and then making a liroail curve along the
base; posterior margin broadly cnrvcd.

Left valve regularly convex hclnw the middle, gibbous du the umbo.
Kight valve smaller, nearly equall}- convex.

Hinge-line straight, a little greater than the height of the valve.

Beaks at about the anterior third of the hinge-line, prominent, obtuse,
rising above the hinge. Und)()nnl region gibl)ons and ample, subtending
nearly a right angle.

Ear small, defined by a distinct siinis and byssal tlepression, roundeil at
the extremity. Wing small, triangular, joining the body below the middle of
its length, not strongly limite(l ; margin gently concave; extremity acute.

Test thin, marked l*}' fine concentric stria\ and lililnrm radintions with
wider interspaces, which are marked by extremely slender intermediate
striie. On the anterior side the radiating lines are liner, ami on the cardinal
margin of tlie wing they are stronger. The right valve is nnirkiMJ oidy liy
elevated concentric striiv, and the wing liy line radiations, which become
stronger toward the cardinal margin.

One S2)ecinien has a length of 10 mm., height I'l nnn.. and hinge-line
iJ nnn.

This species is distinguished from A. perstrialis by its erect and more nearl\-
(juadrate form, shorter ear, less extemlec] wing with less concave margin, ami
more distant, finer strife.

Formation and locality. In the lower part of tlu' (Jhenunig gioup at
Ithaca, N. Y.

LAMELLIBRANCHIATA. 121

ACTINOPTERIA AURICULATA, 11. Sp.
PLATE LXXXIV, FIG. 15.

Shell small, rhomboidal ; l^ody ovate, oblique at an angle of more than 45'^
with the hinge ; length about one-fifth greater than the height ; anterior
margin rounded to the sinus ; base gently rui-ved ; posterior margin abruptly
recurved.

Left valve regularly convex below, gibbous above. Right valve unknown.

Hinge-line straight, greater than the height of the valve.

Beak anterior to the middle of the hinge-line, acute, prominent, arching over
the hinge. Umbonal region abruptly gibbous, subtending an acute angle.

Ear large, straight above, limited by an abrupt vertical byssal depression ;
extremity rounded. Wing small, not strongly defined, joining the body
two-thirds of its length below the beak ; margin concave ; extremity
produced.

Test marked by concentric striae, and about twenty somewhat strong,
sharp radii ; this ornamentation is also continued on the wing and the ear.

Interior unknown.

The specimen is 10 min. in length, 6 mm. in height, hinge-line 7 mm.

This species resembles A. perstrialis in form, but difiers in the larger ear,
abrupt vertical byssal depression, shorter wing and coarser radii.

Formation and localitij. In the Chemung group at Lawrenceville, Tioga
county. Pa.

AcTINOPTERIA DELTA.

PLATE XXni, FIG. 3.

Acfhioplei-in delta, H.\Li,. Pal. N. Y , vol. v. pt. 1. Pliite.s and Explanations: PI. 28, tig-. 3. Jan.. 1SS8.

Shell of medium size, rhomboidal ; body broad-ovate, oblique at an angle of about

60° ; height less than three-fifths the length ; anterior margin rounded,

curving into a defined sinus ; base broadly curved ; post-basal side abruptly

rounded.

16

\2-2 PALEONTOLOGY OF NEW YORK.

Lfl't valvL- iiiljhuiis abovt.', gently convex below. Ki^ht valve uuknowu.

Hinge-line straight, abont equal to the height of the valve.

Beak at about the anterior third of the liini:f. directed forward, ]in)iiiinent,
rising above the cardinal line I'lnbonal region giljbous, iicarlv rectangular.

Ear rounded, defined by a distinct Inssal depression wbich extends
forward from the l)eak. Wing small, joining the bod}- near the posterior
extremity, not strongly defined ; margin gently concave ; extremity produced.

Test marked by fine concentric striae, and undulating or interrupted
filiform radiations, with wider interspaces, which have probably been marked
by finer intermediate striae. The concentric lines are obscure in the cast
and appear as a few irregular concentric undulations.

Interior unknown.

The specimen is 23 mm. in length, 1;") mm. in height, hinge-line 16 mm.

Formation and locality. In the lower part of the Chemung group at Ithaca,
N. Y.

ACTINOPTERIA EPSILON.

I'LATE XXni, FIGS. 4, », (5 ami li?).

Arli/ii/plrna iiisiliiii. ILm.i,. P;il. N. Y., vol. v, pt. 1. Plfttes and Explanation.^: PI. 23, tigs. 4, 8. .Jan., 1883.

Shell of medium size, rhondioidal : body ovate, oblique to the axis at an angle
of about Cid'^ ; height about three-fourths the length ; anterior margin rounded
into a very abrupt sinus; l)ase broadly curved; post-basal side abruptlv
rounded.

Left valve moderately convex. Right valve depre.ssetl-convex above. Hat
or concave below.

Hinge-line straight, length somewhat less than the liiigbt of the valve.

Beaks anterior, acute in the left valve; prominent and elevated aliove the
hinge. Umbonal region gibbous, subtending an angle of less than GO'-'.

Ear short, defined by a deep, abrupt byssal depression. Wing trianguhir,
joining the body below the middle, not strongly defined ; margin regularly
concave ; extremity acute and produced.

LAMELLIBRANCHIATA. 123

Test thill, ill the left valve marked by somewhat distant, elevated, lamellose,
concentric strife, with intermediate finer lines, and by aln'uj)tly elevated
rounded rays with wider interspaces ; these are cancellated by the concentric
stria?, which are more conspicuous on the wing. In the right valve the radi-
ating striae are subdued, and the concentric stria> become more conspicuous.

Interior unknown.

A specimen of the left valve is 21 mm. in length, 16 mm. in height, and
hinge-line 14 mm.

This species differs from A. delta b\- its narrower form and greater obliquity
of body.

Formation and locality. In the lower part of the Chemung group at Ithaca,

N. Y.

ACTINOPTERIA ZETA.

PLATE XXIII, FIG. ;i ; and PLATE LXXXIV, FIGS. 1, i.

Acthwptei'ia zeta. Hall. Pal. N. Y., vol. v, pt. 1. Plates ami Explanations : PI. 23. tifr 3. .Tan., 1SS8.

Shell large, rhomboid-orbicular ; body broadly ovate, nearly erect; height greater
tliau tlie length ; auricular margin rounded into the byssal sinus ; l)elow the
sinus the margin is nearly vertical and gradually joining the broad basal
curvature ; posterior end regularly rounded.

Left valve gently convex below, moderately gibljous al)Ove. Right valve
Hat or concave below, depressed-convex above.

Hinge-line straight, much longer than the greatest length of the valve.

Beak in the left valve sub-anterior, elevated, curving over the hinge ; in
the right valve depressed, not rising above the hinge-line. Umbonal region
subtending nearly a right angle.

Ear small, rounded at the extremity, defined by a strongly marked byssal
depression. Wing large, joining the body lielow the middle, not strongly
defined ; margin deeply concave in the middle ; extremity produced into an
acute extension.

Surface marked by strong, elevated, regular, distant, lamelliform, concentric

124 PALEONTOLOGY OF NEW YORK.

striiu, with iiik'niiediatL' liiicr line;;, and In sk-nder, lililoiia, undulatin;^-,
distant ravs, which an- more crowded on the anterior side, becoming finer and
more nnmerons at tlie juncticm of the wing with the liody, and a few nuuli
stronger ones along the cardinal line. Rays not present on the ear, wliicli is
marked only by the crowded concentric striae The concentric stria^ crenu-
late the rays and liend backward in tlie interspaces, prodncing a beautifully
cancellated surface.

The right valve shows two oblique lateral folds or teeth posterior to the
beak.

A right valve has a length of 25 mm. parallel to the hinge, height 28 mm.,
iiingc-line about 34 mm. An imperfect left valve has an approximate length
of 22 mm., iieight 24 mm., and hinge-line 33 mm.

This species is distinguished by its erect, orbicular rorm. great extension of
hinge-line, and marked surface characters.

Formation and locality. In the lower part of the Chemung group at Ithaca,
N. Y.

ACTINOPTERIA ETA, 11. sp.

I'LATK LXXXIV, FIGS. S-11.

Shell of medium size, rhomboidal ; body broad and short-ovate, oblique at an
angle f)f about 45° : length about one-fourth greater than the height ; anterior
margin below the sinus nearly vertical, curving gradually into the broad
base ; posterior side regularly rounded.

Left valve regularly convex below, moderately gibbous above. Ilight
valve smaller, depressed-convex below, gently convex above.

Hinge-line straight, length greater than the height of the shell.

Beak in Ihc left valve sub-anterior, prominent, arching over the hinge: in
the right valve subdued, scarcely rising above the hinge-line. UmlMnial
region gibbous in the left valve, subtending an acute angle.

Ear, in the left valve rounded at the extremity, slightly oblique, defined by
a distinct byssal depression. In the right valve the oar is larger and flat.

LAMELLIBRANCHIATA. 125

strongly limited. Wing comparatively large, extending three-fourths the
length of the valve, not strongly defined ; margin concave ; extremity -pvo-
duced and acute. In the right valve the wing is larger, extending almost
as far as the posterior side of the valve.

Surface of left valve marked by distant, lamellose, concentric stria?, and by
radiations with wider interspaces, which have sometimes slender intercalated
rays. The concentric lamellse crenulate the radii, and are arched backward
in the interspaces, producing a beautifully cancellated surface. The finer
concentric striae between the lamellse are rarely visible, and the spaces
between tlie rays show, under a lens ami in well-preserved examples,
extremely fine, ci'owded radiations. The radii are also seen in the depression
limiting the ear, and on the wing they are equal to those on the l)ody of
the valve. The right valve is marked l>y regular, equidistant, concentric
lamellae. The posterior slope and wing show numerous fine radii which are
crossed by concentric striae continued from the lamellae on the body of the
valve.

Interior unknown.

A small specimen is 20 mm. long, 14 mm. high, and hinge-line 16 mm.
A larger imperfect example has, approximately, a length of 30 mm., height
22 mm., and hinge-line 24 mm.

In surface characters this species resembles A. zeta, but is distinguished by
its greater obliquity and much smaller wing.

Formation and locality. In the lower part of the Chemung group at Ithaca,
N. Y.

ACTINOPTERIA THETA, n. sp.
PLATE LXXXIV, PIGS. 18, 1».

Shell large, sub-rhomboidal ; body broadly ovate, oblique at an angle of about
55° ; length about one-fourth greater than the height ; anterior margin,
below the ear, nearly vertical, curving into the ))i-oad base; posterior cml
regularly rounded.

126 PALAEONTOLOGY OF NEW YORK.

Left valve moderately convex, depressed holow. Riffht valve siiiallcr .iihI
less convex, in'arly flat hclow.

Hinge-line straight, length nearly equal to the height of the shell.

Beaks sub-anterior, prominent, arching over the hinge-line in the left
valve. T'^nibonal region moderately gil)l)()us in the Ii'l't valve, sulitending an
acute angle.

Ear rounikMl, a little ol)Ui|ue, defined liy a nearly vertical depression. In
the right valve the ear is Hat or concave, liinitcil liy the abrupt elevation
of the umbo. Wings large, in the left valve extending about three-fourths the
length dl' the body, and in tlic right valve joining the body at the posterior
end, without distinct limitation in cither valve : margin moderately concave ;
extremity slightly |Mddnced, angular.

Surface of left valve niarkeil ly sharp, elevated, Lunellose, concentric
stria^, with intermediate liner lines; and by slender, elevated rays, with wider
interspaces between the primar\' rays, wliich ai'e often oc('n]iied with one or
two finer lines; the ear and wing aic marked in a .similar manner. The
rays are distinctly crenulated, and tiii- interspaces are cancellated by the
concentric lines, wliich are .slightl}' curved backw'ard. The surface of the
right valve is marked by strong, lamellose, concentric strije, which liecome
less conspicuous on the wing. The posterior slope of tiie body and tlie wing
of this valve are marked by numerous fine rays.

Interior uid<nown.

A .specimen, with the two valves attached, has approximately a length of
4S mm., height .'!() Tum.. and binge-line :]'] mm.

This species resembles A. eta, but differs in the more extemU'(l wing, finer
radii of the left valve, with interstitial additions, narrower interspaces, and
more numerous concentric lamelhe.

Formation and localitij. in tlie shales of tiie lowei- part of tlie ('lienumg
group at Ithaca, N. Y.

LAMELLIBRANCHIATA. 127

• ACTINOPTERIA KITA, 11. Sp.
PLATE LXXXIV, FKi. 7.

Shell of medium size, rhomboidal ; body broadly ovate, oblique at an angle of
about 45° ; length about one-seventh greater than the height ; anterior margin
nearly vertical or slightly inclined for a short distance, thence curving into
the broad base ; posterior end broadly rounded.

Left valve depressed below, regularly convex above, scarcely gibbous.
Right valve unknown.

Hinge-line straight, about equal to the length of the shell.

Beak sub-anterior, prominent. Umbo moderately gib))ous, subtending an
acute angle.

Ear comparatively short, defined by a distinct byssal depression, rounded
at the extremity. Wing not strongly limited, extending quite as far as the
posterior extremity of the shell ; margin somewhat deeply concave in the
middle ; extremity produced and acute.

Surface marked by concentric lamellose striae, and tine thread-like rays,
which are crenulated and cancellated by the lines of growth both on the
body and on the wing.

Interior unknown.

One of the specimens is -SO mm. in length, 22 mm. in height, and hinge-
line about oO mm.

This form resembles A. theta, i)ut the body is proportionally shorter, the
hinge-line longer, the wing margin more concave and the extremity more
produced.

Formation and locality. In the lower part of the Chemung group at Ithaca,

N. Y.

128 PALEONTOLOGY OF NEW YORK.

ACTINOPTERIA KAl'P.V, 11. ^p. '
1>I.\TK I.XXXIV, Kl<;. 13.

Smell id' iiuMliiini si/.c. rliomboidal ; body narrowly ovate, oldiiiuc at an anuU" of
less tl III II \'y^\ lenj;th one-third greater than the height; anterior margin
oltlique, inmiilcil into the hroadly curved l)asal margin; posterior end alirnptly
rounded.

Left valve dejiressed below, convex Irom the middle upward. Right valve
unknown.

Hinge-line straight, equal to the height of the valve.

Beak sul)-anterior, prominent, arching over tlic liiii^^c-linc Umlional
region moderately gibbous.

Ear short, ol>li(|iie, rounded anteriorly, delined by a distinct byssal depres-
sion. Wing triangnlar, joining the body nearly two-thirds of the length from
the beak ; margin oblique, concave ; extremity produced, acute.

Test thin, marked by fine, concentric, irregularly fasciculating striae, giving
an undulated a])pt'arance to the surface, and by filiform, interrupted and
unttulating radii, with wider interspaces, which sometimes show fine
intei'calated rays. The radii upon the wing are prominent and cancellated
by the concentric striae, and are obsolete upon the ear.

Interior unknown.

The specimen has a length of .'!ll nun., height "JO nun., ami hinge-line
l!<l nun.

This species dilfcrs from A. epsilon, in the greater obli(iiiit\ , longer hingv-liiie,
and more distant radii.

Formation and locality. In the lower member ol' tlu- Clieinuug grou[) at
Ithaca, N. Y.

LAMELIJBRANCHIATA. 129

P T Y C II 0 P T E R I A , Hall.
Ptychopteria Proto.

PLATE XXIII. FIGS. 12, 14.

Plychopteria Proto, Hall. Pal N. Y., voL v, pt. 1. Plate.-^ luul Explanations: PI. 2B, tigs. 12, 14.

.Jan., 1S83.

Shell small, rhomboidal ; liody narrow-ovate, oblique at an angle of about 35°
with the hinge-line ; length more thiin one-third greater than the height ;
ante-byssal margin sub-truncate, rounding into the broad sinus ; base broadly
rounded ; posterior end somewhat abruptly curved.

Left valve regularly convex below, gibbous in the middle and above.
Right valve unknown.

Hinge-line straight, length a little greater than the height of the valve,
and nearly equal to two-thirds its length.

Beak at about the anterior third of the hinge, prominent, inclined forward.
Umbo abruptly gibbous, subtending an ticute angle.

Anterior end large,* rounded, limited by a broad byssal depression directed
backward ; extremity angular. Wing small, narrow-triangular, extending
to near the posterior end of the liody ; margin scarcely concave ; extremity
obtuse.

Surfiice marked by fine, regular, elevated radii, which are less conspicuous
on the wing ; also by concentric striaj, which are often crowded and lamel-
lose, producing a sonjewhat undulated character of the sui^face.

Interior unknown.

A large left valve has a length of 2!t mm., height 18 mm., and hinge-line
20 mm. A smaller specimen has a length of 20 mm., height lo mm., and
hinge-line I 4 mm.

This species resembles P. sinuosa, but the anterior end is wider ; the wing
is smaller and not produced at the -extremity , and the radii are coarser. These

*In the descrijitions of the species of Ptychopteria ami Leptodesma, the term aiiricli' or eai- is not so
applicable to the anterior extension as in Actinoptei'ia and Tjeiojiteria and the tiM-ni anterior end has Leen
used for that portion of the shell anterior to the liy.ssal sinns.

17

130 PALjEONrOLOGY OF NEW YORK.

two species are distinguished from tlic tonus wliicli follow by the large anterior
end \\ liirh is separated from the body liy a l)road byssal depression.

Formation and localUij. In a coarse sandstone, from a bowlder containing the
same associated fossils as a sandstone at Portville, Cattaraugus Co., N. Y. ;
prol)ablv of the I'pper Chemung group; Smethport, McKean county, Pa.

Ptv<"H(>i'ti:i!1a sinuos.v.

PLATE XXIII, FIG. 13; PLATE LXXXV, FIG 8.
Plychoplerla xinuosa. Hai.l. Pal. N. Y., vol. \-. pt. 2. PlatHs smd Explanations: PI. 23, fig. l."?. .laii., 1S83.

Shell of medium size, rhomboidal ; body nai-row-ovate, oblique at an angle of
about 40'^ witli tlic hinge; length more than one-third greater than the
height: ant('-l)yssal margin nearly vertical, curving into the broad sinus;
base broadly rounded ; posterior margin recurving into the wing.

Left valve convex Ixdow, gibbous in the middle ami al)ove. l\ight valve
unknown.

Ilinge-line straight, length four-fifths the length of the shell.

Beak at about the anterior third of the hinge, acute, directed forward.
Undjonal region strongly gibbous, limited by the abrupt depression of the
body on tiie posterior side, and by the byssal depression on the anterior side.
Umbonal angle about 30".

Anterior end large, narrow, rounded, defined liy a broad, shallow, nearly
vertical byssal depression; extremity angular, ^^'ing narrow-triangular,
extending nearly to the posterior extremity of the liody : margin nearly
vertical, slightly concave ; extremity somewhat produced, angular.

Surfiice marked by fine imdulating radii, whicli aiv less conspicuous on the
wing, and by fine concentric lines of growth, uliidi are crowded into sub-
imbricating lainella\ On the anterior side of the body the rays are cancel-
lated by tiie elevated concentric striae.

The ligamental area shows a sharp linear groove extending three-fourths
of its length posterior to tiie beak, and a narrow cai'dinal tooth anterior to the
l>i'ak and parallel in tbc binge.

LAMELLIBRANCHIATA. 131

A large specimen of the left valve has a length of 31 mm., height 19 mm.,
and hinge-line 25 mm. A smaller one has a length of 24 mm., heiglit 13
mm., hinge-line 20 mm.

This species has a narrower anterior end than the preceding, a larger and
more extended wing, finer and undulating stria?.

Formation and localities. In sandstones of the Upper Chemung group, Smeth-
port, McKean county, and at Warren, Warren county, Pa., associated with
Spirifera Verneuili.

Ptychopteria Salamanca.

PI.-VTE XXUI, FIGS. 17-in.

Ptychopteria Salamanca, Hall. Pal. N. Y.. vol. v, pi. 1. Plat.'s :niil Kx]>laiiati<)iis : PI. 2S, tiss. 17-'2().

.Ian.. ISSH.

Shell large, rhomboidal ; body sub-ovate, oblique at an angle of about 40*^ with
the hinge-line; length more than once and a half the lieiglit; unte-byssal
margin oblique, rounded below, slightly concave at the sinus, and sloping to
the broadly rounded base, thence abruptly recurved and continued almost
vertically into the margin of the wing.

Valves convex, gibbous above the middle. Tlie left valve is more gibbous
than the right and somewhat larger.

Hinge-line straight, length more than three-fourths the length of the shell.

Beaks in front of tlie anterior third of the cardinal line, directed forward;
the left beak prominent, acute, arching over the hinge ; the right beak obtuse,
depressed, scarcely rising above the hinge-line. Umbonal region gibbous,
subtending an acute angle. The umbo and beak of the left valve are much
more prominent, and the post-cardinal slope is obtusely sub-angular.

Anterior end comparatively small, triangular, produced into an acute
extension. Wing large, triangular ; margin gently concave ; extremity pro-
duced, acute. The fold and sulcus are more conspicuous in the right valve.

(Surface marked by fine, i-egular, uiuhdating and interrupted radii, which
are more conspicuous on the wing: crossing these are regular concentric

in-2 PALjEONTOLOnr OF NEW YORK.

lines, whicli aiv irrciiularh' n'<)\v(l('(| into siil)-iinbricatiug lamella?. On tin-
anterior end of the valve the railii are cancellated by the concentric stritv.

Interior charaeters unknown, except a narrow groove along the ligamental
area.

A left valve has a length ol' 41 mm., height "ii mm., hinge-line 32 mm.
A similar right valve has a length of 40 iiini., height 24 mm., liiiige-line
34 mm.

This species varies in different conditions of preservation. The obtusely
sub-angular appearance of the posterior slope is often exaggerated by lateral
pressure or subdued by vertical pressure. The same is true of the folds of the
wing. Tn some ecmditions the radiations are continuous, in others they are
cancellated. In weathered specimens the stride are sometimes nearly obsolete,
and the concentric lamella? more prominent.

Formation and locality. In the Chemung group, in a sandstone above the
conglomerate at Hock City, near Salamanca, N. Y.

Ptychopteria Sao.

PLATE XXin, KIGS. 10, Si; AM) PLATE I.XXXV, FICS. 14-1?.

riiirhi.plinii .SVr-i. Uw.i.. I'al. N. v., vol. V, pt. I. I'hitus and K.\i>laiiatioiis : PI. 23, tigs. IG, 23.

Jan.. 1883.

SiiELi, of medium size, rhomboidal ; body narrow, elongate-ovate, oblique at an
angle of about 4")' with the hinge-line; length one-third greater than the
height ; ante-byssal margin obrn|uely sub-truncate, gently eur\ing into the
sinus; base broadly rounded; posterior margin extendt'd, abru[>tly recurved
to the wing.

\'alves convex; left valve larger and UKU'e convex than the right.

liinge-line straight, longer than the heiglit of the valve.

IJeak in front of the anterior third of the cardinal line obtuse, jiroiuineut in
the left valve and arching over tlie hinge; less prominent in the right valve,
and rising just ahove the hinge. Tmbo gibbous in the leit valve, less gibbous
in the rijiht, subtendini: an acute anule.

LAMELLIBRANCHIATA. 133

Anterior end sliort, small, acute, limited by a shallow byssal depression.
Wing large, triangular, extending to near the posterior extremity of the body ;
margin slightly oblique, scarcely concave ; extremity apparently not produced.

Surface marked by fine radii which are more or less interrupted by the
varices of the concentric strise, and are frequently undulating. The concentric
striae are often fasciculate, and in their usual condition give an undulated
appearance to the cast, but where well-preserved they are angular and some-
what lamellose.

Interior unknown, except a narrow groove along the ligamental area of
the hinge.

A left valve of usual dimensions has a length of 30 mm., height 19 mm.,
hinge-line 23 mm. A similar right valve has a length of 31 mm., height 18
mm., and hinge-line 22 mm.

This species differs from P. Proio in its less angular posterior slope and
posterior end ; the margin of the wing is less oblique to the hinge and the
extremity is not produced.

The specimens occurring in a conglomerate or coarse sandstone have been
subjected to different degrees of pressure and maceration, and consequently
present a great variety of asjiect in the surface ornamentation. The furrow
and fold limiting the wing are always less conspicuous in the left valve ; and
in some cases when the shell has suffered pressure these characters are very
obscure.

Formation and locality. Abundant in a conglomerate of the Chemung group
at Panama, Chautauqua county, N. Y.

Ptychopteria Eucrate.

PLATE XXUI, KIG. '24; PLATK I.XXXV, FIGS. 27, 28.
Plyclniptcria Eucrate, Hall. Pal. N. Y., vol. v. pt. 1. PIhIps and Exiilanati(m.« ; PI. 'I'i, tig. 24. -Jan., l.S!S3.

iShell above the medium size, rhomboidal ; body very narrow, elongate-ovate,
oblique at an angle of about 30*^ with the hinge-line ; length nearly twice
the height; ante-byssal margin oblique, curving into the sinus; the ventral

134 PALJEONTOLOGY OF NEW YORK.

margin liroadlv curved ; posterior extremity iilniijitly or sul)-aiigularl3^
recurved.

Li'l't valve convex, giljltous on tlie iimlio and obtusely sub-anuidar along
ilir post-cardinal slope. Rigiit valve less convex, somewhat smaller than the
left.

Hinge-line straight; length about two-thirds the length ol" the valve.

Beak near the anterior fourth of tli(> length ol' the hinge, directed forward ;
beak of left valve prominent, acute, incurved over the hinge-line; beak of
right valve obtuse, and not elevated. Tmljonal region of the left valve
gibbous and angular, of the right valve convex, subtending a very acute
angle.

Anterior end small; margin rounded ; extremity at'ute. Byssal depre.s.sion
iililiiiue, directed backward. Wing naiTow, triangular, joining the body at the
posterior end; margin obli([iii'ly tnuieate, scarcely concave; extremity
apparently not produced.

Surface marked by fine radiating striie, which are more conspicuous on the
body of the valve and upon the wing, and are very obscure on the anterior
end; these are crosseil l)y fine concentric stria> of growth which, at irregular
intervals, are raised into fa.scicles, usuall}- more con.spicuous on the umbo
and post-cardinal slope. On the right valve the radii are usually obsolete.

Interior unknown, exce])t the usual linear groove along the hinge-line.

A large left valve ha-< a length of 4(1 mm., height 2(J mm., and hingedine
28 mm. Another is 38 mm. in length, height 20 mm., and hinge-line 27 mm.

In this species the Ijody is more ohlicpie than in P. Salamanca ; \\iv angularity
of the left valve is in a direct line down the middle of the body ; the shell
is comi)aratively narrower; the extremity of the wing is not produced; the
byssal depression is more obli(iue. The want of striaa on the anterior end and
their ob.solesceiu'e on the right valve are marked characters. It is propoitionallv
much longer than P. Sao, with which it is associated.

Formation and locality. In the lower part of a conglomerate of the ("heniung
group at Panama, Chautauqua county, N. Y.

LAMELLIBRANCHIATA. 135

Ptychopteria Thetis, n. sp.

PLATE LXXXV, FIGS. 1-4.

Shell of medium size, rhomboidal ; body narrow-ovate, oblique at an angle of
about 50° to the hinge-line ; length one-third greater than the height ;
ante-byssal margin obliquely sub-truncate, and curving into a very shallow
sinus, from which it makes a broad curve to the sub-angular posterior
margin, whence it is abrujjtly recurved.

Left valve convex below, gil)bous above, very obtusely sub-angular along
the middle.

Hinge-line straight, length a little greater than the height of the valve.

Beak at about the anterior third of the hinge, prominent, arching over the
cardinal li]ie and directed forward. Umbonal region gibbous, subtending an
acute angle.

Anterior end short, limited by a nearly vertical byssal depression ;
extremity acute. Wing of medium size, triangular, joining the l)ody of the
shell nearly at the posterior extremity ; margin truncate, o1)lique ; extremity
ap^iarently not extended.

Surface marked by concentric stria), which are irregularly fasciculate, and
have an angular recurvation along the middle of the body. The body and
wing are marked by comparatively fine radii, which are sometimes distinctly
cancellated by the concentric lines, and are obscure or obsolete on the anterior
portion of the shell, which is marked oni}' by the lamellose concentric stria,'.

Interior unknown.

A specimen of the left valve of the usual size has a length of o2 mm.,
height 21 mm., and hinge-line 22 mm.

This species resembles P. Sao, Inxt the angle of the body to the hinge-line is
greater, and from the uml)o to the posterior end, the valve is sul)-angular ;
the hinge is longer in proportion, and the fold of the wing less conspicuous.

A right valve in the same association has about the same proportions, but
the body is narrower and the radii coarser, making the identity doubtful.

Formation and locality. In a conglomerate of the Chemung group at Panama,
Chautauqua county, N. Y.

13(3 PALMONTOLOGY OF N FAV YORK.

PtVCHOPTERIA FALCATA, 11. sp.

I'L.VTE LXXXV, KIGS. 6, 7.

SuELi, ol' inediuiu size, rhoiiiboidal, suh-ialcate ; hoch" narrow-ovate, ()lili(|iio at
an angle ofal)ont 45° with tlic eanlinal line ; leiiiitli one-tburth greater than
the licigiit : antcriiii- and l)asal margins liroadJN rounded: posterior margin
ahruptiv recurved.

Lett valve convex, gihhous above, aicuatc. liiLdit valve convex on the
uinho, depressed-convex helow.

Hinge-line straight, greater than the height of the shell.

Beak situated at about the anterior fourth of tlie canlinal line, prominent
and arching over the liingc in tlic left valve; lu^t elevated in the right valve.
Umlto jibruptly gibbous in the left valve, snl)tending an acute angle.

Anterior end liniiteil liv a sliallow. ncarlv \ertical byssal de])ression, which
iiudincs l)ackwaid in some specimens; margin convex; extremitv acuminate.
Wing triangular, joining the body near tiic ])osteii()r end ; margin straight,
slightly concave just hrlow the hingi'-linc ; extremity acute.

Surface of both valves marked by fnie radiating stria', which are less
con.spicuous on the wing and obsolete on the anterior end ; and with
concentric striae, which are sometimes strongly lanudlose. jiroducing inidu-
lations of the surface.

Interior unknown.

A left valve has a length of 28 mm., heigiit 'I'l mm., hinge line 1^4 mm.
A similar right valve has a length of 28 mm., height 15 mm., and hinge-line
24 mm.

The shell of this species is comparatively longer, the l)odv more oblique, and
the wing smaller than in P. Thclis.

Formation and localitij. In a sandstoije and conglomerate of the Upper
Chemung group at Alleghany Springs, Warren county, Pa.

LAMELLIBRANCHIATA. 137

Ptychopteria Spio, n. sp.

PLATE LXXXV, FIG. 19.

Shell of medium size, rhomboiclal ; body elongate-ovate, oblique to the hinge-
line at an angle of about 30° ; length considerably more than one-third
greater than the height ; ante-byssal margin curving into a shallow sinus ;
ventral margin broadly rounded ; posterior margin abruptly recurved.

Left valve regularly and moderately convex, gilibous on the umbo. Right
valve unknown.

Hinge-line straight, greater than the height of the valve.

Beak in front of the anterior third, moderately prominent and scarcely
rising above the hinge.

Anterior extremity narrowly acute. Wing very obliquely truncate, joining
the body near the posterior extremity ; the furrow and fold separating it from
the body are only moderately developed ; extremity not produced.

Test thin, marked by tine undulating radii which are obsolete on the
anterior side ; also by concentric striae which are prominent and lamellose on
the anterior.

Interior unknown.

The specimen described has a length of 35 mm., height HO mm., hinge-line
24 mm.

This species differs from P. Eucrate in its comparatively greater height ; it is
less gibbous in the left valve, the posterior end not angularly produced, the
byssal depression less conspicuous, and the radii finer. It differs from P. Sao
in its lesser gibbosity, greater obliquity of the wing margin, and the generally
subdued characters of the surface markings.

Formation and locality. In a conglomerate of the Chemung group, Panama,
Chautauqua county, N. Y.
18

138 PALEONTOLOGY OF NEW YORK.

Ptychuptekia Eudora, n. .•^p.

'l.ATK LXXXV, KIG. H.

Shei.1, <iI' iiioiliuin size. ihoiiil>i)iilal : liody narrow, elongate-ovato, oliliijiK' at an
angle of about •Sd'^' witli the hinge-line; length nearly twice the height;
;intc-li\ ssal margin oljliqne, curving into tlic long, shallow sinus; base
broadly curved ; posterior end acutely recurved.

Left valve gibbous above, convex below. Right valve unknown.

Hinge-line straight, greater than the height of the shell.

Beak a little in front of the anterior third of tlie liinge directed I'orward,
rising above the cardinal line. Undio narrow and gibl)OUs, subtending a
very acute angle.

Anterior end small, limiteil l)y a wcll-markt'd and oblique Inssal depre.ssion ;
extremity acute. The distance from the byssal sinus to tlic cardinal margin
is (me-half the greatest heiglit of tlie valve. Wing joining the body one-
fourth its length above the posterior end; the shallow furrow and fold defin-
ing its limits are not strongly marked ; margin ol)li(juely tiuncate ; extremity
not produced.

Test thin, marked by radii which are very fnie and imdulating on the
body and wing, while they are obsolete on the anterior portion; these are
cancellated by fine concentric stria), which on some portions are fasciculate,
and very conspicuous on the anterior end.

Interior unknown.

The specimen described has a length of ob nun., iieight lid mm., and
hiiiKe-line about 23 mm.

o^

This species bears considerable resenddance to P. Eucrate, but its anterior end
is proportionally narrower, and it may also be distinguished l)y the absence of
a continuous angularity along the body, the Jiiore abru])t recurving of the post-
basal margin, the more obli([ue truncation of the wing, and the less eon.spicu-
ous surface markings. It diflers from P. Spio in its more gibbous umbo and

LAMELLIBRANCHIATA. 139

more elevated beak, narrower anterior end, more abrupt recurving of the poste-
rior margin, and conspicuous byssal sinus.

Formation and locality. In a conglomerate of the Chemung group at Panama,
Chautauqua county, N. Y.

Ptychopteria alata.

PLATE XXni, FIGS. 25, 2i; (21, >2-l ; and PLATE LXXXV, FIG. 26.

Ptychopteria alata. Hall. Pal. N. Y., veil. v. pt. 1. Plates and Explaiiaticnis : PI. 23. tig-.-<. 2."), 2(i (21,

22 ?). Jan.. 1883.

Shell large, broadly rhomboidal ; body sub-cylindrical, oblique at angle of about
45° with the hinge-line ; height less than two-thirds the greatest length ;
anterior margin ol)lique, sloping into the broad curvature of the base ;
posterior margin recurved almost rectangularly, slightly acute.

Left valve gibbous and angular along the axis of the body from the umbo
to the post-basal extremity. Right valve less convex, and less angular in
character than the left.

Hinge-line straight, about one-sixth less than thi' greatest length of the
valve.

Beak very prominent in the left valve, directed forward ; more depressed
in the right valve ; situated at about the anterior fifth of the cardinal line.

Anterior extremity in the right valve small, triangular, acute. Wing
large, triangular, joining the body at the posterior extremity ; the limiting
furrow is obscure in the left valve, but very marked in the right ; margin of
wing gently concave, nearly vertical ; extremity angular, little produced.

Surface marked by tine radii which (in the specimens seen) are obscure in
• the left valve and nearly obsolete in the right ; and by concentric striae
which are crowded into imbricating; ridges.

Some small right valves found in the same association, and referred with
(lou))t to this species, preserve the radii in a much stronger degree.

Interior unknown.

A large right valve has a length of 42 mm., height 26 mm., and hinge-line
35 mm.

140 PALEONTOLOGY OF NEW YORK.

This species is (listinj^uislicd hy the great contrast in the convexity of the
two valves. Tlie left valve is strongly angular ami elevated iVoin the uniho to
the posterior i-xtremity : tlu' right valve is conspicuously alate.

Formation and locality. In a coarse sandstt)ne of the Chenunig group, near
Salamanca. X. Y.

Ptychopterta trigonalis, u. sp.

PLATE I, XXXV, FIGS. 34, 35.

Shell small or of medium size, rliomhoidal ; liods siilj-rylinih-ical, (ililiijue at an
angle of about 4')° with the hinge-line ; length one-third greater than the
height; anterior m;n;j.iii lounded, gently curving into the broad base, with
a faint byssal sinus; postei'ior margin almost rectangularly recurved.

Left valve convex, gibbous on the umbo, and angular fi-om the umbo to
the post-basal extremity. Right valve uidsnown.

Hinge-line straight, length greater than the height of the valve.

Beak in iront of the anterior third of the hinge, obtuse, prominent and
incurved. Umbonal region gibbous, sul)tending an acute angl(\

Anterior end short, rounded, indistinctly separated from the body by an
obscure byssal sinus. Wing large, triangular, joining the body of the valve
near the posterior extremity ; the limiting furrow is very distinct in young-
shells, and obscure in oldei- examjiles; margin somewhat obliquely truncate;
extremity not produced.

Surlace marked by fine radii, wiruh are obscure or obsolete on the anterior
part of the shell ; also by concentric strise, which are somewhat acutely
ri'curved on the angular portion of the body, and in older shells art' fascicu-
late, producing an undulated aspect.

Interior unknown.

A small left valve has a length of It; mm., height I I mm., and hinge-line
13 mm. Another specimen has a length of 30 nun.. Iieight 18 mm., and
hinge-line 25 mm.

LAMELLIBRANCHIATA. 141

This species lias some resemblance to P. alata in the left valve, Init its height
is comparatively greater, the wing more truncate, and not produced at the
extremity.

Formation and locality. In a slialy sandstone above a conglomerate in the
upper part of the Chemung group at Panama, Chautauqua county, N. Y.

Ptychopteria elongata, n. sp.

PLATE I.XXXV, FIGS. 10-13.

Shell of medium size, sub-rhomboidal, elongate ; body sub-cylindrical,
oblique at an angle of 30° with the hinge-line ; length more than one-third
greater than the height ; anterior margin oblique, curving into the basal
margin, with a slight concavity for the byssal sinus ; posterior margin
abruptly rounded.

Left valve regularly convex below, gibbous above. Right valve somewhat
depressed-convex.

Hinge-line straight, about one-fifth less than the length of the valve.

Beaks near the anterior fourth of the hinge, directed forward ; left beak
prominent, sub-acute, arching over the cardinal line ; beak of right valve
depressed, obtuse, scarcely rising above the hinge-line. Umbo gibbous in
the left valve ; the greatest convexity of the valve is about one-third the
length from the beak. Umljonal angle acute.

Anterior end short, produced and acute at the extremity, limited by a
distinct oblique byssal depressit)u. ^Ying narrow-triangular, joining the bod_v
of the shell near the posterior extremity, limited by a furrow which is not
conspicuous in the lower part, but in the right valve is more marked; margin
ol)liquely truncate.

Surface marked by fine radii, Avhich are distinctly cancellated hy the con-
centric strise, when the specimen is tolerably well-preserved ; also by concen-
tric lines of growth which, at somewhat regular intervals, are sharply elevated.
The radii are obsolete on tlie anterior of the valve, and the concentric strise
are lamellose.

142 PALEONTOLOGY OF NEW YORK.

The connected valves show a narrow ligamental area fxtemlini: liall' the
lono^th ol' the hini'c. Otlici' cliaiacters of tlie interior arc unknown.

One specimen lias a length of 35 nun., height 21 mm., and hinge-line 25
mm. .\notlicr has a Icnirth of ^o mm., hcii;ht 1-'! mm., and liinge-line 2(1 mm.

This species resend)les P. Kucrate, l)nt is less gibbous, more elongate, and
without angularity along the body.

Formation and locality. In a conglomerate of the Chemung group at Panama,
Chautau(ina county, N. Y.

Ptychopteri.v g.\lene, n. sp.

I'l.ATK I. XXXV, KIOs 23-31.

Shell small, rhondioidal : liody suli-dliptical. i)Mi(|ue at an angle of aliout 40°
with the hinge; height greatei' than half the length: ante-byssal margin
oblique, curving gently into a shallow siiuis ; base regularly rounded ;
posterior end al)ru])tly recur\ed.

Left valve convex, moderately gibbous on the umbo, and sub-angular along
the upper half. Itight valve less convex above, depressed-convex in the
lower part.

Ilinge-line straight, length greater than the height of the valvi".

Beaks near the anterior third of tlie hinge, inclined forward, prominent,
arching over the hinge-line. Umbo gibbous, subtending somewhat less than
a right angle.

Anterior end small, limited by the shallow, nearl\' Ncrtical byssal depres-
sion ; extremity acute. Wing wide-triangular, joining the bodx near
the posterior em! : limiting furrow distinct ; fold w ide and moderately
prominent; margin oliliiiiicly trinuati', \i'ry slightly concave just below the
hinge-line ; extremity angular.

Surface ol' the body and wing marked by regular, line, interru|)ted or
undidating ladii. wliidi are olisciu'c or obsolete on the anti'rior ])ortion : also
In very line concentric lines, which are crowded into irregular fascicles and
are himellose on the anterior part of the valve.

LAMELLIBRANCHIATA. 143

Interior unknown.

A left valve has a length of 26 mm., height 18 mm., and hinge-lirie 20 mm.
Another sioecimen has a length of 24 mm., height 14 mm., ami liinge-line
17 mm.

Compared with P. Eucrate and P. elongata, the l)ody of the shell is compara-
tively shorter, the furrow of the wing more distinct, the byssal depression
shallower and more nearly vertical. It has the obscure angularity of P. Eucrate,
with coarser and more nearly vertical radii.

Formation and locality. In the lower beds of the Upper Division of the
Chemung group, as seen at Warren, Pa.

Ptychopterta Beeoheri, 11. sp.

I'LATE LXXXV, KIGS. '21, 22.

Shell large, rhomljoidal ; body cylindrical, very arcuate in the left valve, oblique
at an angle of aliout 40° with the hinge ; length nearly twice the height ;
ante-byssal margin slightly oblique, curving gently into the sinus ; ventral
margin broadh' roundeil, straighter toward the posterior end, which is
acutely recurved.

Left valve ventricose, the greatest convexity a little iibove the middle ;
abruptly rounded or sub-angular along the post-cardinal slope, and the eleva-
tion is continued into the angular posterior extremity. Right valve much
less convex.

Hinge-line straight, lengtli moi-i' than two-thirds the length of the shell.

Beaks at about the anterior third of the hinge-line, very prominent and
incurved over the liinge in the left valve. In the right valve the beak is
sulidued, not rising above the hinge-line. Umbo very gibbous in the left
vfilve, sul)tending an acute angle.

Anterior end moderately large, limited by a very Ijroad, shallow, slightly
oblique byssal depression ; extremity flattened, acute, defined by an o1)li([ue
constriction in the margin just l)olow the cardinal line. Wing of medium
size, joining the hody of tlu' shell a little above the posterior extremity ;

144 PALAEONTOLOGY OF NEW YORK.

t\w liinitinj:' fminw distinct; tiif ioM unitU' and the upprr jiart of tlir wiiiff
tint or sli<ilitly cuiivcx ; iiiariiiii <iliiii|iicl\ tiimcatt', concave jnst hclow tlic
hinge; extremity slightly produccii.

Sini'acc marked 1)\- fine nnit'onn radii on the hoily and w inn', whicli arc
nearh ohsolctc on the anterior end, and sometimes interrupted on the hody
hv varices of growth ; also liy line concentric stria; which are acutely
recur\i'd o\'er the ant:nl,ir posterini- slope ol' tlie hody, and crowiled into
fiiscicles at ii'ret:iihir inler\als, ])io(hicing an umhihited apjiearance.

Interior unknown.

A lar^e left valve has a length of ')'! mm., height "JS mm., and hinge-line
3(j mm. .\ rii:ht \al\c in the same association has a length of in nnii.,
height -!<• mm., and himie-liue '.',:] mm.

This s])ecies somew lial reseniiiles P. Irigonalis, hut the postei'ioi' extremity is
more produced, and the wing more ohliijuely tianicate on the nnu'gin. The
right \alve in general aspect resemhles the right valve ol' /-". alala. hut the left
valve is very dissimilar. The distinguishing characters are its large rhomhoidal
form, extreme gihhosity and ai-cuation of the left valve.

Formation and locality. In a compact sandstone of the Upper Chemung group,
in the lower l)eds as seen at Wairen, Pa.

PtYCIIOPTERIA SP.VTILATA, U. Sp.
1M..\TE I.X.WV. KIC. 20.

Shell large, elongate, rhondioidal : l)ody snh-elliptical. ohli(pie at an aniile of
ahout ;')0'^ with the hinge: length more than one-third greater than the
height; ante-hyssal mamin ol)li(pie. gently curving into the simis, thence
extending into the hroadly curvi'd hasal margin ; posterior end rectangularly
or acutely recurved.

Left valve moderately convex, slightly gihhous above. Ilighl valve
depre.ssed-convex, more snh-angular along the post-cardinal slope, and smaller
than the left.

LAMELLIBRANCHIATA. 145

Hinge-line straight, length aliout one-seventh less than the greatest length
of the valve.

Beaks at about the anterior fourth, prominent and incurved over the hinge-
line in the left valve ; depressed in the right valve and not rising above the
cardinal line. Umbonal angle nearly rectangular.

Anterior end large, limited by a broad, slightly oblique, undefined bj'ssal
depression ; extremity acute and nasute. Wing elongate triangular, joining
the body at the posterior end : the dividing furrow distinct in the left valve,
more conspicuous in the right; the fold is not delined in the left valve, and is
strongly marked in the right ; margin nearly vertically truncate ; extremity
not perceptibly produced.

Test thin, marked by fine radii, which are conspicuous upon the body and
wing, and obsolete on the anterior end and byssal depression. The surface
is also marked by fine concentric strias, which are crowded into fascicles,
giving an apparent undulation to the surface from the inubo to the lower
extremity, especially iu the right valve. At the post-basal margin tlie
stria? are recurved at a, little less than a right angle in the left valve, and
more acutely in the right valve, and they are strongly laniellose on the
anterior end.

Interior unknown.

Tlie specimen descril)ed lias a length of 56 mm., height 30 mm., and
hinge-line about 4S mm.

This species resembles P. lata, and also some forms of P. Sao, but it is mucli
more elongate, the valves more depressed, the wing narrower and longer.
Formation and locality. In the Upper Chemung group at Warren, Pa.

Ptychopteria lata, n. sp.

PLATE LXXXV, FIGS. 23-25.

Shell large, rhomboidal ; body sub-elliptical, very oldique, making an angle
with the hinge of nearly 4(1° ; height equal to about two-thirds of the length ;
ante-l)yssal margin o)ili([ue, curving into tlie sliallow simis, from wheiu-e tlie
19

146 PALAEONTOLOGY OF NEW YORK.

basal margin is broadly rounded ; posterior extremity recurved at a little less
than a right angle.

Left valve more convex than the right and gibbous above, obscurely
angular along the post-cardinal slope. This diff('r(Mio(' in the valves is also
shown in the direction of the strioe of growth.

Hinge-line straight, about three-fourths as long as the length of the shell.

Beaks near the anterior fourth of the hinge, prominent in the left valve,
acute, arching over the cardinal line ; in the right valve depressed, rising only
as high as the hinge. Umbonal region of the left valve moderately gibbous,
sul)tending an acute angle.

Anterior end short, small, limited by an oblique byssal depression which
extends along the base about one-third the length of the shell ; extremity
acute. Wing large, extending along the shell to near the posterior extremity ;
margin obliquely trnncate, concave just below the hinge-line, which is
al)ruptly produced.

Test thin, marked by line, interrupted or undulated radii, which are more
strongly marked on the body and wing, and obsolete on the anterior of the
valve ; the surface is also marked by fine concentric striae, which are crowded
into fascicles at unequal distances, undulating the surface; tlu'v turn aliruptly
outwiird. just Itclow the hinge, and are lamellose on the anterior part of the
valve.

Interior unknown.

A specimen preserving both valves has a length of ("i iiiiii.. height 2S nmi.,
hinge-line ?>'~i mm. The right valve is somewhat smaller. Aimtlirr
specimen lias a length of 42 mm., height 28 min., hinge-line of) mm.

This species resembles in form P. Sao, but is larger, the wing furrow nioie
strongly defined on the left valve, the concentric lines more acutely recurved
at the ba.sal angle, and the radii are finei- and more numerous.

Formation and locality. In the rppei- Clieunuig group, the niiddU' lieds of
the series, as seen at Warren, Pa.

LAMELLIBRANCHIATA. 147

Ptvchopteria perlata, n. sp.

PLATE LXXXV, FIGS. :». 39.

Shell large, rhomboidal ; l>0(ly ovate, oblique ; length one-sixth greater than
the height ; anterior and basal margins broadly curved ; posterior end angular.

Left valve very convex, gibbous above. Right valve somewhat gibbous
above, having a convexity of about one-half that of the left valve.

Hinge-line straight, nearly equal to the length of the shell.

Beak at about the anterior third of the cardinal line, prominent and
arching over the hinge in the left valve. Umbo gibbous in the left valve
and convex in the right, subtending an acute angle.

Anterior end large, obscurely defined by a shallow byssal depression, which
is obsolete in the right valve ; margin convex ; extremity acuminate. Wing
broad triangular, joining the body at the posterior end ; the furrow and fold
are stronger in the left valve ; margin slightly convex below, inclining a
little forward ; extremity produced, acute-aiigular.

Surface of the left valve marked by fine, close, rounded radii, which are
often interrupted by the concentric lamellae. The radii are finer upon the
wing, obsolete upon the anterior end, and scarcely present on the right valve.
The concentric lines of growth and Limellie, give an irregularly undidating
appearance to the surfiice.

Interior unknown.

A left valve has a length of 31 mm., height 26 mm., and hinge-line oU nnn.
A right valve measures 33 mm. in length, 27 mm. in height, and hinge-line
32 mm.

This species is a shorter, more erect form than P. lata, and the left valve is
more convex and broader below.

Formation and localifij. In the upper beds of the Chemung group at
Warren, Pa.

148 PALEONTOLOGY OF NEW YORK.

Ptvihopteria Thalia, n. sp.

IM.ATE I, XXXV, FIGS. 32, :«.

Shell of medium «ize, rhomboidal ; body ovate, oblique at an an^le of about 45°
with the cardinal line; Iciiiith one-third greater than the hei^lit : aiitciior
.and basal margins broadly rounded, slightly impressed by the byssal sinus;
post-basal extremity sub-angular, abruptly recurved.

Left valve extremely gibbous, the point of greatest convexity is one-
third of the height from the beak. Right valve convex on the umbo,
depressed-convex below.

Ilinge-line straight, a little less tluui the greatest length ol' the slirll.

Beak situated at the anterior third of the binge, prominent in the left
valve, curving over the hinge-line. Umbonal region abruptly gibbous in the
left valve, distinctly limited, subtending an acute angle.

Anterior end comparatively large, limited by a nearly vertical shallow
byssal depression ; margin convex ; extremity acute. Wing small, distinctly
limited by the post-unilional I'iutow : margin oliliijuely tnnicate, a little
convex ; extremity obtuse-angled.

Surface of both valves marked by fine radii originating on the umbo,
becoming stronger on the lower part of the body, less conspicuous on the
wing, and oljsolete on the anterior end ; and by lines of growth which
are lamellose on the anterior side and produce unequal concentric ridges on
the body of the valve.

Interior luiknown.

A left valve has a length of 25 mm., height 17 mm., ami hinge-line
23 mm. A small right valve has a length of "Jd mm., height 1') mm., and
hinge-line l(i mm.

This species resembles P. perlata Imt the wing is comparatively smaller,
extremity not acuminate, and the umlio more gibbous.

Formation and loralili/. In a sandstone of the I piicr ( 'lirmnm.:' group at .Vlk'-
ghany Springs, Warren comity, l*a.

LAMELLIBRANCHIATA. 149

PtYCHOPTERIA GIBBOSA, 11. sp.

PLATE LXXXV, FIG. 5.

Shell small, rliomboidal ; body broad-ovate, oblique at an angle of about 45°
with the hinge-line ; length not more than one-seventh greater than the
height ; ante-byssal margin oblique, curving into the marked sinus, thence
along the base to the nearly rectangularly recurved posterior extremity.

Left valve very convex, gibbous on the umbo and in the middle. Right
valve unknown.

Hinge-line straight, nearly as long as the length of the shell.

Beaks a little anterior to the middle of the hinge ; very prominent in the
left valve and arching over the hinge. Umbonal region ample, very gibbous,
obscurely angular along the posterior slope, subtending an acute angle.

Anterior end somewhat large, gibbous, and separated from the body of
the shell by a nearly vertical sulcus ; extremity acute and nasute. Wing of
medium size, joining the body at the posterior end ; the furrow and fold are
very conspicuous, the fold somewhat broader and nearly equal to the portion
of the wing above ; margin almost vertically truncate ; extremity apparently
not produced.

Test thin, marked by fine radii and concentric striae. The concentric
lines are crowded into fascicles, producing ao undulated appearance ; and are
strongly lamellose on the anterior end ; the radiating striaB are distinct upon
the body of the shell, obscure on the wing, and obsolete on the anterior end.

Interior unknown.

A specimen of the left valve has a length of 26 mm., height 15 mm.,
hinge-line 22 mm. Another has a length of 20 mm., height 13 mm., hinge-
line 18 mm.

This species is distinguished by the sub-central position of the beak, and the
great prominence of the umbo ; the marked byssal depression, and strong
furrow and fold of the wing.

Formation and locality. In the upper beds of the Chemung group at Warren,
Pa.

150 PAL.EOMX)JJJGY OF NEW YORK.

Ptvchoi'teria louata, ii. !<p.

fI-.\TK LXXXV, Vm. 37.

Shell small. sul)-ilioinboidal ; bod}- broadly ovate, oblique at an angle of about
55° with the cardinal line ; length somewhat greater than the height ; anterior
margin sub-truncate ; base broadly rounded ; posterior margin rectangularly
recurved into the wing.

Left valve very gil)bous; tlic point of greatest convexity is just below the
umbo. Right valve unkiuiw ii.

Hinge-line straight, lengtli ncai-ly njual to the length of the valve.

Beak situated anterior to the middle of' the hinge, prominent, inclined
forwanl. and arching over the nr.irgiu of the valve. Umbonal region ample,
gibbous, subtending an acute angle.

Anterior end large, limited by a broad, undefined Iwssal depression ;
margin convex; extremity apparently obtuse. Wing small, joining the body
at the posterior end, strongly limited l)y a deep furrow and very marked
alar plication ; margin nearly straight ; extremity angular.

Surface marked by fine radiating striae which become finer on the wing
and anterior end : and by striae of growth which are somewliat lamellose on
the anterior of the sbcll.

Interior unknown.

A left valve of this species has a length of lo mm., height 10 mm., binge-
line 1 1 mm.

This species differs from P. gibbosa in its shorter, truncate anterior end, and
stronger fold on tiic wing, wliiili is comparatively stronger than in any species
yet observed.

Formation and locality. In the sandstones of the Upper Chemung group,
Warren county. Pa.

LAMELLIBRANCHIATA. 151

PtYCIIOPTEIUA VaNUXEMI, 11. (Sp.
PLATE I.XXXV, FIG. 36.

Shell large, sub-triaiiguhir ; body narrow-elongate, .sub-cylindrical, oblique at
an angle of nearly 30° with the hinge-line ; ventral margin very long and
gently curving ; posterior margin abruptly and acutely recurved.

Left valve very convex along the axis of the body. Right valve unknown.

Hinge-line straight, length more than one-fourth greater than the height,
or about two-thirds the entire length of the shell. Umbonal angle very acute.

Anterior end unknown. Wing very large, triangular, joining the body
near the posterior end ; the furrow and fold obscure ; margin obliquely
truncate to near the hinge, where it is concave and abruptly recurved into
the produced extremity.

Test thin, marked by strong radii, and by fine, sharp, equidistant, laniel-
lose concentric striai. The concentric strisB are crowded and somewhat
fasciculate on the posterior and the wing, giving an undulated or imbricated
appearance. The rays are very strong over the middle of the body, and
subdued on the wing and basal side, and are distinctly crenulated by the
elevated concentric lines, with the interspaces cancellated.

Interior unknown.

The specimen described has a length of 70 mm., height 34 mm., and
hinge-line about 44 mm.

This species is conspicuously distinct from any other ; in outline it approaches
some of the extreme forms of Pteronites.

Formation and locality. In the highest beds of the Upper Chemung group at
Warren, Pa.

152 PALEONTOLOGY OF NEW YORK.

Ptychoptekia kxpansa.

PLATE XXIII, FIGS. 10, II.

PlyrliiiplerUi tj-iHiusH, Halt.. Pal. N. V.. vol. v. pt. 1. Plates and Kxjilanatioiis : PI. 23, tigs. 10, 11.

Jan., 1883.

Shell of medium size, .sub-rhomlioiil.il : body ovate, oblique at an angle of
aliout (10° with tlii' hintic-linc : Ininth one-fifth greater than the height;
ante-byssal luargin oblique, gently eurving intu the shallow sinus; basal
margin broadly rounded to the l)ase of the wing.

Left valve convex lu'low, gilibous above. Right valve uidsiiowu.

Hiuge-line straight, central, length greater than the length of the valve.

Beak at al»)uT the anterior Hftli of the hinge, inclined acutely forward,
moderately prominent, rmlional angle acute.

Anterior I'lid sinall, surface convex to the nearly vertical byssal depression
whicli exti'iids lialf way to the base of the shell; extremity compressed and
acute. Wing very large, triangular, extended, joining the body at the
posterior extremity ; the furrow obscurely marked ; margin gently concave,
extending backward ; extremity produced.

Surface marked by regular strong radii and by concentric lines of growth.
The concentric stria; are sometimes crowded into irregular fascicles, giving
an umhilated ain)earance to the surface; the radii are strong on thi' umbonal
slope, less conspicuous on the wing, and on the antero-basal portion tlu-y are
interruptetl, and obrupie to those on tlie umbo.

Interior unknown.

The si)ecimen described has a length of 27 iniu., lu'ight 22 mm., ami hinge-
line oO mm.

This species is distinguished by its erect form, large and extended wing, and
peculiar character of surface markings. 'I'lie I'urrow of the wing is indicated
only by a wider depression between the radii, and a strongei- ray marks the
fold.

Formation and localitij. Tn a coarse sandstone of tlie Chemung gionp near
Smethport, Pa.

LAMELLIBRANCHIATA. 15;

GLYPTODESMA, Hall.

Glyptodesma erectum.

PLATE XI, FIGS. 1-10; PLATE XII, FIGS. 1-3, 3-9; PLATE XIII, FIGS. 1-4, 1J-I5 ; PLATE XXV, FIGS. U-17 ;
PLATE LXXXVI, FIGS. I-S ; .IXD PLATE LXXXVII, FIGS. l-»

AvicuJa electa, Conrad. Jour. Acad. Nat. Sci., Phila., p. 238, pi. 12, tig-. 5. 1842.
" cruciformis, Conrad. Geolog-. Surv. N. Y. : Annual Report, p. 54. 1841.
Actinodesma ei'ectuvi (Conrad), Hall. MS., Pal. N. Y. 1877.

" S. A. Miller, in Cat. Amer. Pal. Foss. 1877.
" cruciforme (Conrad), Hall. MS., Pal. N. Y. 1877.

" " S. A. Miller, in Cat. Amer. Pal. Foss. 1877.

Glyptodesma erectum (Conrad), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 11, tigs.

1-10 ; pi. 12, tigs. 1-3, 5-9 ; pi. 13, tigs. 1-4, 12-15 ; pi. 25. figs.
14-17. Jan., 1883.

Shell large ; body ovate, acute, erect or moderately oblique ; wings more or
less expanded, often greatly expanded ; height frequently one-third greater
than the length ; liasal margin more or less regularly rounded; anterior side
broadly convex ; posterior side nearly straight or slightly concave.

Valves very unequal. Left valve varying from moderately convex to
gibbous and arcuate. Right valve depressed-convex in the umbonal region,
flat or concave below ; variable in convexity.

Hinge-line straight, often greatly extended, equalling or usually greater
than the length of the valve.

Beak of left valve prominent, acute, inclined forward, rising above the hinge-
line, and situated anterior to the middle of the body of the shell. Umbonal
region somewhat prominent, often gibbous, limited anteriorly by a distinct
rounded sulcus, and posteriorly by an interruption and change in the direction
of the striae, which sometimes produces a defined line of separation.
Umbonal angle acute.

Anterior wing auriform and small in young specimens, becoming expanded
and variously extended in older specimens, limited by a distinct byssal
depression ; extremity rounded. Posterior wing large, triangular ; margin
concave ; extremity often extended beyond the margin of the shell.

Test thick, marked by fine, irregular, concentric striae of growth which are
sometimes raised into sharp lamellae, or crowded into prominent fascicles.
20

154 PALEONTOLOGY OF NEW YORK.

Tlic'se striae become more conspicuous upon tlic maruiiis iiiul upon the wings,
wlicrr tlu'V ;iri' ol'tcn liiiililv lamcllose. The distant lamellae wliicli mark
the lioilv of the shell are sometimes continued upon tlic liinge, and becoming
stronger, curve over tlic margin, giving it a sharply annulated aspect,
which, when preserved in the impression of the ]iinge-l)order, might be
mistaken for a more important organic marking. Partially exfoliated shells
show some obscure radiating lines which belong to the intimate shell-structure,
and are not external. (These strise are too conspicuously represented in
figure 6 of plate xii.)

Posterior muscular impression situated near the middle of the posterior
slope, and marked by irregular vascular striae ; from the lower anterior side of
this impression the pallial line extends slightly downward, curving forward,
and continuing in a line nearly parallel to the margin it terminates in a
small muscular impression within the rostral cavity. The pallial line is
frequently pitted or interrupted in its course, and from these ])its ladiating
grooves extend toward the margin of the shell.

Ligamental area extending the entire length of the hinge, comparatively
wide, grooved longitudinally with fine, continuous parallel lines. Hinge with
one or two linear, sliglith' oldique, lateral teeth on the jwsterior side, and
with numerous erect or oblique irregular folds along the cardinal line below
the ligamental area, which terminate on the inner margin in distinct crenu-
lations. The cardinal wrinkles are smaller and more regular anteriorly,
becoming large and irregular posterior to the beak.

Three large specimens have the following respective dimensions: length
'JO, 70, and 81 mm., height 100, 99, and 81 mm. ; hinge-line 100, 90, and 90
nun. An example of medium size has a length of 55 mm., height 76 mm.,
and hinge-line 48 mm. A large, erect individual measures 72 mm. in length,
and 90 mm. in height. A small right valve has a length of 23 mm., height
27 mm., and hinge-line 33 mm.

This is an abundant species and attains a very large size in older individuals.
In its different conditions of growth and preservation, it presents a very great
variety of aspect, and it becomes extremely difficult to determine the limits

LAMELLIBRANCHIATA. 155

of the species. In the young shell the posterior wing is proportionally more
extended than in older individuals, while the anterior wing is usuall}' smaller.
During the progress of growth, both wings often become extravagantly
developed, and the form and proportions of these parts cannot be relied upon
for specific distinctions. The characteristic forms have the body nearly erect,
with the umbo and beak directed slightly forward ; but associated with these,
are other forms which present a considerable degree of obliquity in the body
of the shell, and while there seem to be no constant marks of specific
distinction, it is extremely unsatisfactory to group them all under one species.

The interior characters also present considerable differences, the number of
lateral teeth varying from one to three ; the cardinal wrinkles and crenulations
not only vary in number and strength, but in their direction, which is vertical
or oblique. There is also a very great difference in the width of the ligamehtal
area.

Formation and localities. In tlie shales and slialy sandstones of the Hamilton
group, from the eastern limit of the formation as far west as Canandaigua
lake ; it is extremely abundant in Albany and Schoharie counties ; Cazenovia
and Hamilton, in Madison countv, and at Pratt's falls, in Onondaga
county, N. Y. This species is also found in a cherty limestone in Clarke
county, Indiana ; and in similar conditions and associations at several locali-
ties in Ohio.

Glyptodesma erectum, var. obliquum.

■PLATE Xir. FIG. i; and PLATE XIII, FIGS. o-II.

Glyptodesma erectum, va.v. obliquum. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanation.s ; PL 12, tig.

4 ; 1)1. 13, fig-s. ."i-U. Jan., 1883.

This variety possesses the essential characters of the typical forms of the
species. The hinge, test, etc., are similar, but the body of the shell is distinctly
oblique ; the wings are less developed, and the anterior wing, especially, has not
the great extension often observed in the erect forms.

156 PALEONTOLOGY OF NEW YORK.

The specimens of tliis \;ii-it'ty are uniformly smaller. They have been
observed mainly in the soft shales at Pratt's falls, OiKnidaga county, wiiilc the
large erect forms are common in the coarse shales and grits of the gn>u|i in tin-
eastern portion of the State, and in Madison county.

In examining and comparing the extreme forms, the ililferenco is striking
and distinctive. (For exam2)lo, the erect forms on plate xi, and tiie oblique
forms, figures 5 to 11, plate xiii.) But in the study and comparison of a
series of several hundred specimens, the intermediate forms appear to unite
the whole under a single species.

To facilitate the examination, the oblique forms, represented in figures 5-11
of plate xiii, are here designated as G. eredum, var. obliquum.

The description of Avicula ereda, and A. crudformis, given by Mr. Conrad,
are as follows, loc. cit. :

" Avicula ereda, pi. 12, fig. 5. — Direct ; independent of the wings, of ovate
" acute outline ; left valve ventricose, concentrically wrinkled, or marked with
" lines of growth ; apex prominent, narrow, acutely rounded ; posterior wing
" elongated, pointed ; basal margin uniting with the lateral margins in a regular
" curve or arch.

Locality — Hamilton, Madison county. New York.

" Avicula crudformis, Conrad, loc. cit. : " Elevated, with both ears greatly
"elongated. Locality — NearOneonta: This species is remarkable for the great
"proportional height; very little ()lilir[ue. Height oA inches."

The name of A. crudformis has precedence in point of time, but the name
of A. ereda has been adopted because the description and figure entitle it to
recognition, and the former name is only applical)le to the more extravagant
forms of the species illustrated on plates xi and xii.

LAMELLIBRANCHIATA. 157

Glyptodesma occidentale.

PLATE XV, FIG. 12; AND I'LATK LXXXVI, FIG. 9.

Glyptodesiim occidentale. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 15, tig. 12.

Jan., 1883.

Shell large, broadly ovate ; body nearly erect ; height and length about equal ;
margins regularly curved.

Left valve very convex, gibbous on the umbo. Right valve unknown.

Hinge-line straight, equalling or greater than the length of the shell.

Beak anterior to the middle of the shell, directed slightly forward, acute
and prominent. Umbonal region gibbous, defined anteriorly by the broad
sulcus, and on the anterior side sloping abruptly to the wing.

Anterior wing short, defined by a deep sulcus and a marked byssal sinus.
Posterior wing large, depressed-convex, much extended, joining the body of
the shell below the middle, and defined only hy the recurving of the striae ;
margin concave ; extremity acute.

Test thick, marked by numerous fine stria3 of growth, which at intervals
are crowded into fascicles, producing an undulating surface. The striae are
more closely arranged, and become lamellose on the anterior part of the
shell. On the posterior wing the striae are regular, and at distant intervals
a single stria becomes sharply elevated.

Interior unknown.

The specimen of this species described has a length 60 mm., height 66
mm., and hinge-line equal to, or greater than the length of the shell.

This species resembles G. eredum, but appears to be a more robust form ; the
shell is more orbicular, the umbonal region more gibbous, the surface more
rugose from the undulations of the fascicles of strias, and the limitation
between the body and the posterior wing is less strongly defined.

Formation and localities. In the limestone of the Upper Helderberg group at
the Mis of the Ohio, near Louisville, Kentucky, and in Clarke county, Indiana.

158 PALEONTOLOGY OF NEW YORK.

LEIOPTERIA, Hall.
Leiopteria l^vis.

PLATE XVII, FIGS. 5-11 ; AND I'LATE XX, FIO. 5.

^|jic((?a larvis. Hail. Geolog. Surv. N. Y. : Rei). Fourth Dist., p. 181. 1843.
Pleronltes lotvli, (Hall) S. A. Millek. Cat. Amor. Pal. Foss., p. 202. 1877.
Leiopteria Iwpis, Hall. Pal. N. Y., vdl. v, pt. 1. Plates and Explanations : PI. 17, figs. H-II. Jan., 1883.

Shell small, .suh-rlioinboidal; body obliquely ovate; length and height nearly
('f|ual ; greate.st length Ijelow the middle ; margins regularly rounded, some-
what extended on the post-basal side.

Left valve more convex than the riglit ; the greatest convexit}" in both
valves is above the middle

Hinge-line straight on the posterior side of the beak, turning aljiujitlN
downward in front ; entire length greater than the length of the shell.

Beaks obtuse, rdimilci!. inclined forward, situated at the anterior third ol"
the shell, that of the lelt valve (|uite ]>rominent. Umbonal region ol' left
valve prominent, subtending an acute angle.

Ear triangular, nearly equilateral, with a strong angular fold along the
middle, separated from the body of the valve ))y a distinct rounded sulcus
and broad byssal sinus; margin rounded; extremity obtuse. Wing trian-
gnlar, tlat, limited by the post-umbonal slope; margin concave ; extremity
acute.

Test tliin, iiiai-ked with distinct concentric stria? of growth, which are
crowded and conspicuous on the \viiigs. There are often oliscure traces of
radii, wliich are more distinct on tlie wing in casts or exfoliated specimens.

Ligamental area narrow, with a single distinct groove. Some specimens
apparently indicate the existence of an oldiiiue lateral tooth on the posterior
side of the umbo.

One specimen has a length of II mm., heiglit 1 "J mm., hingc-linc about
10 mm. Another has a length of iU mm., heiglit I I mm., and liiugt'-line 12

LAMELLIBRANCHIATA. 159

mm. A small specimen is 8 mm. in length, 9 mm. in height, and hinge-line
10 mm.

Formation and localities. In the Marcellus shale at Littleville, Livingston
county ; Alden, Erie county, and East Bloomfield, Ontario county, N. Y.

Leiopteria Conradi.

PLATE XX, FIGS. 1, i, 4; and PLATE LXXXVUI, FIGS. 1-1.

Leiopteria Conradi. H.iLL. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PL 20, fig-s. 1, 2, 4, {5

in erroi-). Jan., 1883.

Shell above the medium size, sub-rhomboidal ; body oblique-ovate ; length a
little greater than the height ; anterior margin straight, nearly vertical ;
iiasal and posterior margins regularly rounded.

Valves sub-equally convex ; the left valve somewhat more convex than
the right.

Hinge-line straight, longer than the length of the valve, greatly extended
posteriorly.

Beaks acute, directed forward, prominent, situated near the anterior end
of the shell. Umbonal region gibbous (in well-preserved shells), moderately
convex l^elovv, subtending an acute angle.

Ear short, separated from the valve by a rounded depression or sulcus,
marked l>v a shallcnv, elongate byssal sinus ; extremity rounded. Wing-
triangular, nuich extended ; margin concave ; extremity acuminate.

Test, as indicated by casts or partially exfoliated specimens, marked by
fine, closely arranged, concentric lines of growth, which at irregular intervals
are crowded and raised into rounded or sub-angular fascicles, giving the
surface a decidedly undulated aspect. The strije become more crowded upon
the cardinal expansions, especially upon the ear.

Ligamental area marked by a single longitudinal groove parallel to the
hinge-line.

Two specimens of the left valve have respectively the following dimensions :
length 39, and 42 mm., height 32, and 30 mm., hinge-line 42, and 47 mm.

iGU PALEONTOLOGY OF NEW YORK.

This species hears some general resenililaiuc in form to Actinopteria decussata
and A. Boi/di, hut is distinguished hy tlie ahsence of rays. It differs from
L. Greeni, fig. '.•, ph xx, in its more ohlique form and greater proportional length.

Formation and localities. In shales of the Hamilton group, on the shore of
Canandaigua lake, and at Bellona, Yates county, N. Y.

Leiopteria Greeni.
ri.ATE x.\, FIGS. 0, \i\ AND ri.ATF, i.xxxvui, Ki(;s. ■:i. *>.

T^npterla Greeni,YiK\.\.. Pal. N. V., vol. v, i.t. 1. Plates a id Explanations : PI. 20, ti^'S. 9. l:i. .Ian.. 1883.

Shell large, suh-rhomhoidal : Ixidy modei'ately ()hli(|ii('. hroadl^y ovate ; length
a little greater tlian the height; margins regularh rounded, somewhat
extended posteriorly.

N'alves moderately and nearly ciinally convex; similar in character.

Hinge-line straight, equalling or greater than the li'iigth of the shell.

Beaks acute, anterior, inclined foi'ward, arching over the hinge in the
left valve ; less prominent in tli(> riglit.

Ear short, limited hy a sulcus and sinus which is deeper in tlie right valve.
Wing large, triangular, defined only hy the abrupt bending of the striaj ;
margin concave ; extremity acute.

Test thin, marked by numerous, closely arranged, concentric lines of
growth, and, at somewhat regular intervals, by sharp, projecting lamello.se
stria? ; and corresponding with these, are regular concentric undulations,
which are shown strongly on the cast, and but jiartially seen on the exterior
surface. The striae mark the wing in the same manner as the l)ody. and are
crowded on the ear.

Ligamental area narrow, marked by a single groove.

A large specimen measures ^u mm. in lengtli, •">] mm. in height, hinge-
line 58 mm.

This species resembles L. Conradi, but is broader, with comparatively greater
heiglit, less obliquity, and le.'ss extended posterior wing.

Formation and localities. In the shales of the Hamilton group at Bi'Uona.
Yates county, and on the shores of Cayuga and Cantmdaigua lakes, N. Y.

LAMELLIBRANCHIATA. 161

Leiopteria Rafinesquii.

PLATE XV, FIG. 11 ; PLATE XX, FIGS II, 7 ; and PLATE LXXXVIII, FIGS. 27, 28.

Leiopteria liafiiies lull. H.\i,L. Pal. N. Y., vol. v, pt. 1. Plates and Exiilanations : PI. 15, tig. 11; pi. 20,

tifjs. G, 7. Jan., 1S83.

Shell of medium size, sul)-rhomboidal ; body rather narrow above, obliquely
ovate ; height equalling or greater than the length ; margins regularly
curved ; the post-basal side extended ; anterior side sometimes nearly
straight for a short distance below the ear.

Left valve convex, gibbous on the umbo. Right valve less gibljous. The
right valve supposed to belong to this species is convex on the umbo, and of
moderate convexity below ; the height is considerably greater than the
length, and the body of the valve less distinctly defined than in the left
valve.

Hinge-line straight; from the anterior side of the l)eak to the posterior
extremity it is about equal to the length of the shell.

Beak of the left valve acute, directed forward, very prominent, situated
at the anterior extremity of the shell. Umbonal region gil^bous, subtending
an acute angle.

Ear short, convex, obtuse, with a brotid undefined vertical sulcus and shal-
low byssal sinus. Wing moderately large, flat ; margin concave ; extremity
acute.

Test thin, marked by regular, concentric lines of growth, which are more
crowded upon the cardinal expansions. The strise aij,e raised at intervals
into strong, elevated lamellae, which are conspicuous on the cast, and more
crowded and prominent on the anterior side. The right valve referred to
this species is marked by concentric wrinkles, which are well-preserved on
the anterior side, with distant, elevated, lamellose strise on the wing and the
margin of the hinge.

Internal characters unknown. The ligamental area appears to be marked
by a groove along the wing parallel to the hinge-line.

Three characteristic specimens have respectively the following dimen-
21

162 PALAEONTOLOGY OF NEW YORK.

sions: length 39, 34, and 25 mm., height 41, 38, and 26 mm., hinge-line 37,
39, and 20 mm. The right valve, mentioned above, is 23 mm. in length, 25
mm. in height, and 23 mm. along the hinge-line.

This species re.sembles the two preceding, but the form of body is more
narrowlv ovate, the oliliquity appears to be intermediate between the two;
the i-ar is less strongly defined : tlic wing is comparatively narrower, and less
extended at the extremity.

Formation and localities. In the shales of the Hamilton group, on the shores
at Skaneateles lake ; at Bellona, Yates county, and Leonardsville, Madison
county, N. Y. ; a single specimen from the Corniferous limestone of Delaware,
Ohio, has been referred to this species.

Leiopteria S.\yi, n. sp.

Pr.ATK I.XX.WUI, FIGS. 1.5-20.

Shkll above the medium size, sub-orbicular ; body very broadly ovate, scarcely
oblique; height greater tlian tlu' length; margin nearly straight in front.
thence regularly rounded.

Left valve very convex, gibboiis in the umbonal region. Right valve
smaller and less convex.

Hinge-line straight, longer tlian the length of the slicll.

Beaks acute, situated near the anterior extremity of the hinge, i)roniiiient,
inclineil lorwnrd, ar<liing over the hinge-line. Umbonal region ample, sub-
tending a right angle.

Kar small. Iicuding downward, flclincd by a broad, shallow sulcus. i?yssal
sinus narrow. Wing large, triangular, greatly extended along the hiiigc-linc,
defined by the retral bending of the stria^; margin concnve; extremity acute.
The wing of the right valve is very broad. Hat. and iiuirh extended : not ilis-
tinctly defined.

Surface marked by fine, clo.sely arrangeil stria^ of growtli, with distant,
elevated lamelhe, which are extensions of strong i'a.scicli's of stria'. These
leave angular concentric folds and undulations in the casts. The stria' are

LAMELLIBRANCHIATA. 163

strongly marked on the cardinal expansions and over tlie hinge-margin.
In well-preserved specimens the undulations are stronger upon the middle
of the valve, and less marked upon the anterior side and the wing. In the
right valve the}* are much more regular and subdued.

Interior characters unknown. Ligamental area marked by a distinct
groove parallel to the margin.

The largest specimen has a length of oO mm., height 40 mm., hinge-line
about 45 mm. A small specimen measures 26 mm. in length, 39 mm. in height,
hinge-line imperfect. Another specimen is 26 mm. in length, 33 mm. in
height, hinge-line 27 mm. A right valve is 33 mm. in length, height about
the same, hinge-line 41 mm.

This form resenrbles, in general surface characters, the three preceding
species, but differs by the more erect body and sul^-orbicular form. In general
aspect it resembles Glyptodesma, and the surtace markings are not very differ-
ent, though none of the specimens show the hinge characters of that genus.

The description has l)een drawn from specimens preserved in line calcareous
shale and in coarser arenaceous material, and the characters remain essen-
tially the same in both.

In a single specimen from the arenaceous shales on the shore of Cayuga
lake, at Norton's Landing, where the shell is partially exfoliated, the surface
is marked by fine, concentric lines of growth, and more distant lamellose stria",
which are about twice as numerous as in the typical specimens. These give a
gently undulating chai'acter to the surface of the cast of the left valve, instead
of the abrupt angular folds of the typical specimens. In the right valve of the
same specimen the striae on the umbo ;ire similar, but more closely arranged,
and on the lower portion, in the cast, they exliibit the gentle undulations of the
typical forms of the right valve.

Formation and localities. In shales of the Hamilton group, in Ontario county ;
Norton's Landing, Cayuga county ; Bellona, Yates county, and in the coarse
grits at Leonardsville, Madison county, N. Y.

ir,4 PALJEONTOLOGY OF NEW YORK.

Lkiopteria Dekayi.

I'l.ATE XIX. KIG 1 ; I'LATK .\.\, FICJS. HV18 ; and PLATE LXXXVIII, KIGS. 5-10.

r^ii>})terii( Dikiuji. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 19, fig-. 1 ; pi. 20, figs.

lU-lS. (lit in error). Jan., 18S3.

Shell oi" medium size, sub-rhomboidal in general form ; body narrowly ovate,
oblique; length about equal to tlH> lioiglit; anterior margin nearh- vertical
lor one-third the length of the .shell, thence broadly rounded over the ba.sal
margin and abruptly recurved at the post-basal extremity.

Left valve convex, gibbous on the umbo. Right valve smaller and less
convex; the limitation of tlic wing not strongly defined.

Hinge-line straight, length a little less than the lengtli of the .-^licll
measured from the anterior side of tlic beak to the cxtrcuiity of the wing.

Beaks anterior, acute, pi'ominent, inclined forward. Umboual region
gibbous above, regularly convex below, subtending an acute angle.

Ear l)ending downward, with a strong fold in the upper part, limited bv
a broad undefined sulcus and shallow byssal sinus. Wing triangular, tiat,
defined Ijy the abrupt retral Ijending of the stria3 and a depressed line along
the post-cardinal slope ; margin concave ; extremity acute.

Test thin, marked by fine regular concentric strijv, which at unequal
intervals arecrowdeil into fascicles, giving an uiKhilatt'd as])e('t to the surface
of the cast ; in old specimens, more crowded on the anterior side and ear,
and on the wing usually regular, sometimes becoming a little fosciculate on
the margin.

This description of the surface is taken from casts or partial casts which
preserve more or less the surface markings. In a few ^-ounger specimens
from the shales, the surface shows tine regular stria' which gradually l)ecome
fasciculate as the shell increases in size.

Ligamental area narrow, marked by fine stri;e ; helow this area is a narrow
oblique fold or lateral tooth.

The three specimens figured on plate xx, have respecti\ely the following
dimensions : length 37, 31, and 20 mm., height 37, 3(1. and 3(1 mm., hinge-

LAMELLIBRANCHIATA. 165

line 31, 21, and 23 mm. A smaller specimen has length of 17 mm., height
16 mm., hinge-line 15 mm.

This species resembles in form L. Conradi and L. Rafinesquii, but there are
some differences in shape and obliquity, and more decidedly in surface
characters. The wing is not so much extended as in L. Conradi, the striae are
more abruptly recurved, and the post-cardinal slope is more strongly defined.
There is a general resemblance with L. Bigsbiji, but tlie bod}- ami hinge-line
are longer, the body narrowing more rapidly from the base, and the strise are
equal and uniform.

Formation and localities. In the soft shales of the Hamilton group ; at Skane-
ateles and Cayuga lakes ; and in the upper coarse beds and lower shales at Pratt's
falls, Onondaga county ; also at Schoharie, N. Y. It is widely distrilmted from
the eastern to the central portion of the State.

Leiopteria Bigsbyi.

PLATE XX, B'IGS. 3, 11, 13-15; AND PLATE LXXXVIII, FIG. 23,

Leuipteiia Bigxhi/i. Hall. 1'mI. N. Y., vol. v, pt. 1. Plates und Exi.laiKitiiiiis : PI. L>0, tiys. 3, II, 13-1.'.

Jan., 1SS3.

Shell larger than medium size, sub-rhomboidal ; body ovate, oblique ; height
greater than the length ; anterior margin nearly vertical for about half the
height of the shell, thence regularly rounded along the base ; posterior side
moderately extended.

Left valve gibljous upon the nmljo, less convex towards the base. Right
valve gibbous on the umbo, depressed-convex below, shorter than the left
valve.

Hinge-line straight, equalling or less than the length of the shell.

Beaks anterior, acute, prominent, rising above the hinge-line, inclined for-
ward. Umbonal region prominent, subtending an angle of about 55°.

Ear short, bending moderately downward, with a strong fold at the upper
side, limited by a broad, undefined sulcus. Byssal sinus shallow. Wing
triangular, wide, nearly flat ; margin concave ; exti-emity acute. The wing

\M PALEONTOLOGY OF NEW YORK.

1)1' the riirlit valvt' is k'ss (k'liiK'd tliaii in the Itft. iiiid the livssal sinus is a
little tU'oper.

Test tliiii : s|n'ciiiii'iis partiallv t'xfoliatcd, or occiirrinu in tlic ciinditioii ol"
casts, show sliarpiv cU'valfd, laiiu'llosc, coiicciitric stri:v, w liidi arc scry dis-
tinct on the wings, and crowded and somewhat ("asciculate on the anterior
side and ear. No intermediate finer stria- have been ohserved. In well-
])reserved specimens the sharj) lauielhe ha\e uiiduhitini;' margins.

Interior nnknown. Ligamental area marked liy a single groove.

A large specimen lias a length of 4.'] mm., height •')() nnn., hinge-line M7 mm.
Another example has a length of oli mm., height '■)'■'> mm., liingc-rnu' -JO mm.
In tlu' yoimgei- shells the height is proportionallv somewhat less than in
the older ones.

This species, compared with the preceding, has a greater height of hody and
shoi'ter liinge-line. and ilill'ei's in the conspicnous, sharp, concentric lamella^.
Ill this species the concentric striie do not produce the folds and uudulatinns
wliich are characteristic of L. Rafinesquii and L. Greeni.

Formation and localities. In shales of tlu' Hamilton group at Pratt's falls,
nudiidaga countv, and in the coarser beds at Schoharie, X. Y.

'o"

TiKllll'TKHIA MlT(lli:r,I,I.

I'LATK X.X, KK;. s ; and I'I.ATE, I, XXXVIII, KIc, -Hi.

Lewptma MitcheUi, Ham.. Pal. N. V., vol. v, pt. 1. Plates and Exi>laiiations : PI. ::0, li;,'. 8. Jan., 1883.

Shell large, sul)-rhond)()idal ; body ovate, moderately oblique; height greater
than tiie length ; anterior nuirgin nearly vertical from the ear for about half
the height, then broadly curving to the post-basal side, thence more abruptly
bending, making the posterior eml slightl}^ extended.

Left valve gibbous on tiie umbo, sloping IVom highly conxcx aboxc to
moderately convex below. Kight valve unknown.

Hinge-line straight, i'(jual to the length of the valve.

Beak anterior, acute, inclined forward, prominent. Lmbonal region prom-
inent, subtending au acute angle.

LAMELLIBRANCHIATA. 167

fe

Ear short, limited bv an undefined sulcus and shallow byssal sinus. Wing
large, triangular, nearly Hat, defined l)y the retral curving of the lamellose
striae; margin moderately concave; extremity aln-uptly acute.

Test thin, marked by regular concentric lines of growth, with distant,
lamellose striae, which are raised into thin, sharp elevations corresponding
with the concentric folds or undulations of the shell. The cast shows only
the undulations. On the anterior margin and wing, the lamellae are closely
crowded, producing a varicose appearance. They are more closely arranged
upon the wing than on the valve, making a gentle retral curve and becoming
very conspicuous on the hinge-margin.

Interior unknown. Ligamental area narrow.

A left valve has a length of 46 mm., height 40 nun., hinge-line about
47 mm.

This species, in general proportions, resembles A. Bigsbyi ; it difl'ers in the
larger and more extended posterior end, with stria) nearly vertical or gently curv
ing, except at the hinge margin ; the body wider above, and the anterior basal
margin less convex. With a single exception, the specimens of L. Bigsbyi
occur in arenaceous beds, while this species is common both to the softer shales
and in the coarser beds.

Formation and localities. In soft shales of the Hamilton group, from loose
masses of rock at the south end of Seneca lake, and in the coarse grits, at
Schoharie, N. Y.

Leiopteria Troosti, n. sp.

PLATE LXXXVni, FIGS. 12, 13.

Shell above the medium size, sul)-rliomboidal ; body broadly ovate, moderately
oblique ; height somewhat greater than the length ; anterior margin, from
the wing to about half the height, nearly vertical, curving broadly around the
base, and more abruptly rounded behind.

Left valve moderately convex, gibbous on the umbo. Right valve unknown.

Hinge-line straight, somewhat less than the length of the shell.

HJS PALEONTOLOGY OF NEW YORK.

Beak anterior, acute, prominent, inclined forward, rising above the hinge.
I'lnhonal region gibbons, abruptly limited on the anterior side bv the sulcus,
and on the posterior side sloping rapidly to the wing.

A\'ing large, tlat, triangular, joining the body of the vahe below the
middle of the height, limited by the gently retral curve of the striae ; margin
moderately concave ; extremity acute or iniu iduatc

Surface marked by regular, ecpiiilistaiit, uiuliilating, lanu'llilnnii. concentric
expansions, which become crowded, finer, and to some extent less undulated
on the wing, stronger and very much crowded on the anterior of the shell.
The undulations extend forward in an abrupt curve, bending gently back-
ward, and being thus opposite and slightly imliricating, they give an
appearance of radiation.

Interior unknown.

The specimen described has a length of oG mm., height '61 mm., and hinge-
line about 29 mm.

In general aspect, this species resembles Actinopteria Boydi, but the body is
much less oblique and wider below ; the surface is without proper rays ; the
wing has only fine, crowded, concentric stria;; while in that sjjecies the wing is
marked with strong radii and a lew lines of gi'owth.

These comparisons are made from similar casts of the interior of both species.

Formation and locality. In the coarse grits of the upjier part of the Hamilton
group, ill the northern part of Schoharie county, N. Y.

LeIOPTERIA LeAI, 11. .-^p.

PLATE LXXXVIII, FKJS. 2t, '.i

Shell small, sub-rhomboidal ; body broadly ovate, very moderately ol)li{pie;
height much greater than the length ; margin regularly rounded from aliove
the middle on the anterior side, to a similar point on the ojjposite side of tlie
valve ; post-basal margin slightly produced.

Left valve very convex; gibbous from below tlie middle ti) tlie umbo.
Right valve unknown.

LAMELLIBRANCHIATA. 169

Hinge-line straight, less than the length of the shell.

Beak anterior, acute, rounded, inclined forward, prominent. Uniljonal
region gibbous, subtending an acute angle.

Ear short, directed downward, limited by an undefined sulcus, with
scarcely any evidence of a byssal sinus. Wing comparatively small, flat,
not strongly defined, joining the body of the shell above the middle of its
height ; margin concave ; extremity abruptly acute.

Test marked by fine concentric strire, which, at intervals, are crowded into
fascicles upon the body of the shell, giving an undulating surface. On the
wings they are closely and evenly arranged.

Interior unknown.

One specimen has a length of 20 mm., height 25 mm., and hinge-line about
17 mm. A small specimen has a length of 13 mm., height 15 mm., and
hinge-line 12 mm.

This species is more prominent on the umljo and more convex below than
any of the forms described in this group ; the wing is shorter and smaller,
with less extension along the postei'ior slope. A young shell referred to this
species and in the same association has a body less abruptly defined on the
posterior side.

Formation and locality. In the coarser grits of the Hamilton group, in tlie
southern part of Schoharie county, N. Y.

Leiopteria Gabbi, n. sp.

PLATE LXXXVm, FIG. 14.

Shell small ; body ovate, very slightly oblique ; height considerably greater
than the length ; anterior margin nearly erect for half the height of the
valve, and regularly curving to the post-basal margin, which is scarcely
produced.

Valves sub-equally convex ; the greatest convexity Ijeing a little above the
middle in the left valve, and on the umbo of the right valve.
Hinge-line not extended, less than the length of the shell.
22

17(1 PAL.EOMVLOGY OF MCW YORK.

Beaks acute, prominent, iliii-oteil t'orwanl, anterior to tlie middle of the
shell. Umbonal region gibbous, subtending an acute angle.

Ear small, straight on the upper margin ; marked by an oblique fold, and
separated Worn, the body by an abrupt sulcus and a well-defined byssal sinus.
Wing small, triangular, joining the body of the shell below the middle of
its height, defined by a change in the direction of the surface strije; margin
gently concave ; extremity acute.

Test thin, marked by line concentric striai, ami at reiiulai' intervals In-
stronger elevated stria?, which give to the macerated shell, and the cast of the
interior, a regular banded surface. These stronger strise are closely arranged
on the anterior side and ear. while on the posterior side they ])reserve their
equidistant character. The right valve is very distinctly marked by the
elevated concentric stria\ In both valves there are radiating lines which
apparently belong to the structure of the shell.

Interior unknown. Ligamental area narrow.

One specimen has a length of 13 mm., height 111 nini., hiiiLie-line aiiout
in iiiui. Another example has a length of 12 iiiui., height \o mm., and
hinge-line about 1 I mm.

Tiie small size, erect ovate form, short hinge-line, the proportions of height
and length, and the surface characters, distinguish this species from every other
form here described.

Formation and localities. In the soft shales t)l' the Hamilton group ; shores of
Canandaigua lake, and at Norton's Landing, Cayuga lake, N. Y.

Leiopteria Oweni.

PLATE XX, FIG. 10.
Leiopter'm Oweni, Halt,. Pal. N. V., vol. v, |it. 1 Pliitos ami Explauatioii.s : PI. 20. tifr. 10. .Ian.. 1883.

Shell quite large, sub-rhomboidal ; body broadly ovate, oblique to the hinge-
line; length greater than the height; margins rounded, produced posteriorly.
Left valve convex, umbo gibbous, beak elevated. Right valve concave

LAMELLIBRANCHIATA. 171

below, Hat above, becoming convex towards the beak, which i^; low and
scarcely reaches the hinge.

Hinge-line straight, about equal to the length of the valve.

Beaks anterior, acute, directed forward.

Ear large, extended, defined by a broad sulcus and marked byssal sinus.
Wing large, expanded ; margin concave ; extremity abruptly acute.

Test thin, marked by fine concentric striae of growth, which on some
parts of the surface are crowded into fascicles, producing ridges or undula-
tions. These are somewhat regular over the whole of the left valve,
and stronger on the anterior part ; on the right valve they are without
regularity. The right valve also shows radiating lines which appear to
belong to the shell structure, and are quite conspicuous in partially exfoliated
specimens. The strige are crowded and lamellose on the anterior margin
and adjacent to the byssal sinus ; on the wing they are closely and evenly
arranged.

Interior unknoAvn.

One of the imperfect specimens described has an approximate length of
(U mm., height 55 mm., and hinge-line a))Out 55 mm. ; the measurement
along the axis of the body, from the beak to the post-basal margin, is
75 mm.

The two specimens observed are crushed, and the characters of the left valve
are very much obscured, while the right valve preserves more nearly its true
proportions. It dift'ers from the other species of this group in the concave
form of the right valve. In surface markings it is very similar to L. Sayi,
but the concave right valve is a very distinguishing feature. The shell is
large and thin, and has suffered compression and distortion in the process of
imbedding in the soft shales.

Formation and localiUj. In the soft shales of the Hamilton group, Canandai-
gua lake, Ontario county, N. Y.

172 PALjEONTOLOGY OF NEW YORK.

Leiopteria Chemungensis.

PLATE XXII, FIOS. 17, 18.

Apicula Vhemiingeiisis. Vani xkm. (xcdldfr. Surv. N. V. : Rei>. 'I'liinl Dist., p. 182, tig. 40, Nn. 'i. 1842.
fyeiiipteria uitida. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 22, lig«. 17, 18.

Jan., 1883.

SiiKLL ut iiic'diiuii !<i/A' ur larger, rhomboid-ovate : bod}- elongate-ovate, oblique at
an angle of about 00° with the hinge-line; length equal to more than fi)ur-
fit'th.s of the height; anterior margin nearly vertical for about one-hull'
the height of the shell and broadly rounded on the base ; post-basal margin
abruptly rounded.

Left valve convex, gibbous in tlie umlM)nal region. Kiglit valve smaller,
less gibbous.

Hinge-line straight, a little longer tlian tlie height of the shell.

Beaks sub-anterior, inclined forward, acute, prominent, arching over the
hinge. Umbonal region narrow, prominent, subtending an acute angle.

Ear of left valve small, Ijending slightly downward, defined by a broad
distinct sulcus ; extremity rounded. Ear of right valve flat. B3^ssal sinus
shallow and broad, deeper in the right valve. Wing broad-triangular,
joining the body below the middle of the length, limited by the abrupt
bending of the striae ; margin deeply concave in the middk' ; extremity
produced and acute.

Surface, in a partial cast, marked by fine concentric striae, which are
crowded and lamellose on the ear, distinctly marked on the wings, and
appearing on the I)ody as distinct undulations: these in tlie perfect shell
may have been sharp lamelliform striae.

Interior unknown.

A specimen of the left valve has a length of 30 mm., lieight •"!;") mm..
hinge-line 47 mm.; the body from beak to post-basal extremity iiiea,siu-es
43 mm.

The specimen figured is the original of Avicula Chemungensis, Vanuxkm. It
resembles L. Dekayi of the Hamilton group, but differs in its longer hinge-line,
larger wing, and more acute beak, while the body of the shell is narrower.

LAMELLIBRANCHIATA. 173

In the volume of Plates and Explanations this species was referred to
L. Dckayi in the absence of the original specimen, which has since lieen
compared and found to belong to the Chemung group.

Formation and locality. In a slaty sandstone of the Chemung group, eight
miles north of Binghamton, N. Y.

Leiopteria linguiformis. n. sp.

PLATE LXXXVUI, FKj. 23.

Shell a1:)0ve medium size, erect, sub-rhomboidal ; body elongate-ovate, making
an angle of about 60° with the hinge-line ; length equal to three-fourths of
the height ; anterior margin nearly vertical from the byssal sinus to below
the middle of the valve ; basal margin broadly rounded ; post-basal margin
rapidly curving into the Aving.

Left valve convex above, depressed-convex below. Right valve unknown.

Hinge-line straight, nearly equal to the length of the shell.

Beak acute, erect, prominent, rising above the hinge-line. Umbonal
region convex, subtending an acute angle.

Ear small, triangular, bending slightly downward, limited by a well-
defined byssal depression ; margin nearly straight ; extremity rounded.
Byssal sinus shallow. Wing broad-triangular, joining the body below the
middle of the post-cardinal slope, not strongly limited ; margin concave ;
extremity acute.

Surface marked by concentric stride which are strongly lamellose on the
ear, the pallial margins and on the wing.

Ligamental area narrow, marked by two or three longitudinal grooves.
Muscular impression oval, situated near the middle of the post-cardinal
slope.

The specimen described has a length of 33 mm., height 42 mm., and
hinge-line 32 mm.

174 PALEONTOLOGY OF NEW YORK.

Tliis species differs from L. Chemungensis in its more erect form, and tlic car
is without the strong fold and marked sulcus of tli.it species: tin- wiuLr is alsn
less extended and the margin less concave.

Formation and locality. In the (Jhemung group in the valley ol' Cayutu creek,
Broome county. N. Y.

LeIOI'TEEIA TullKEVI, n. sp.
n.ATK XXII. riGS. G, 7; and pl.vte lxxxvui, fk;. n

SiiKi.L ol' nu'diuni size, rhomboidal, sub-falcate; body narrow-ovate, arcuate,
ol)lique at an angle of less than 45° wdth the iiinge ; height equal to al>out
two-thirds of the length ; anterior and basal margins broadly curving liom
the byssal sinus; post-basal margin ])roduced and abruptlv recurved.

Left valve very convex, gibbous in the middle and above. Right valve
unknown.

Hinge-line straight, al)Out equal to the height of tin- valve.

Beak sul)-anterioi", directed forward, acute, prominent and aicliing over
the hinge. Umbonal region narrow, vcntricose, well-defineil, subtending an
acute angle.

Ear large, bending downward, marked by a strong oblique fold, limited ly
a broad, vertical byssal depression and shallow sinus; niai-gin convex;
extremity ap})arently obtuse. Wing joining the body above the posterior
extremity, limited liv the nearly vertical post-nnd)onal slope, which makes a
more or less nuirked sulcus; margin concavi' : extremity proiluccd. acute.

Surface marked by fine striae of growth which are somewhat reguiarh'
lamellose on the body of the valve.

A left valve has a lc)i;:tli of "J'.l inni., lieiglit 'I'l nini., bingc-liiu> ill mm.

This species dilfers from L. Chemungensis in its proportionally greater lengtii.
narrower umbo, more convex and oblique left val\ e, and shorter wing.

Formation and locality. In a sandstone and conglomerate of the ("biiiiuug
group near Panama, N. Y.

LAMELLIBRANCHIATA. 175

LEPTODESMA, Hall.

The species arranged under the generic designation of Leptodesma present a
very remarkable assemblage of forms, beginning (as here arranged) with those
resembling Avicula and passing through various phases in form, proportions,
etc., until the wing becomes nearly obsolete, the byssal sinus obscure, and the
antei-ior end rounded, and the entire shell assuming the form of Mytilus or
MoDiOLA, Sanguinolites, Modiomorpha and allied genera. For convenience the
species have been arranged into natural groups in the following order : a, spini-
fera ; b, umbonata ; c, rostrata ; d, patulata ; e, arcoidea ; f, mytiloidea. These
relations will l)e more fully explained under the generic description and discus-
sions in tlie Inti'oduction to this volume.

Section a, spinifera.

Leptodesma Marcellense.
PLATE XVII, fk;. :-2.

Li-ptodesnia Mai-celleuse, Rxhh. Pal. N. Y., vdl. v, pt. 1. Pl.-ites and Exiilanations : Pl. 17, tii,>-. 12. Jan., 1883.

Shell small, sub-rhomboidal ; )»ody obliquely ovate ; height about two-thirds
the greatest length ; margin regularly rounded, extended posteriorly and
continuing in a direct line to the beak.

Left valve moderately convex. Right valve unknown.

Hinge-line straight, greatly extended posteriorly, reaching beyond the
margin of the valve.

Beak obtuse, prominent, nearly erect, situated on the anterior third of the
hinge. Umbonal region jjrominent, sloping abruptly on the posterior, not
well defined on the anterior side.

Anterior end limited by a shallow, obscure sulcus ; margin regularly
rounded. Wing narrow-triangular, much extended along the hinge, termin-
ating in a mucronate process ; margin deeply and acutely sinuate.

17G PALEONTOLOGY OF NEW YORK.

Test thin, marked Iiy fine, closely arranged, concentric strise, which are
more crowded anteiidily : these are crossed by extremely fine radii, wliich
are cliielly confined to the shallow sulcus, anterior to the beak, and are also
(jbscurely marked on the wing.

Ligamental area marked b}- two strong grooves. Two oliliiiiu' linear
depressions along the posterior slope indicate the probable existence oi' lat-
vy;\\ teetli. Other characters of the interior, unknown.

The speciiui'ii has a Icuu'tli of I 1 imii.. hci;:iit 7 iinii.. hin^c-linc \'l inui.

This species bears some resemblance to several species in the Cliemung
group, l)ut it is comparatively narrower and more oblique.

Formation and localiUj. In the Marcellus shale, Bloomfield, Ontario count\-,
N. V.

Lkptodesma Kogersf.

I'l.ATK XXI, FIGS. l-!l.
Leptitilestma Hof/emi. Il.u.i.. Pal. N. V.. vol. v. ].t. 1. Plati-.sMinI t^xiilaii.ntions : PI. ^1, tio-s. l-it. .Ian., 1883.

Shell ol' small ur medium size, sul)-rhouihoi(hd ; body ovate, very oblique;
length greater than the height ; anterior and basal margins broadly rounded ;
posterior margin extended and abruptly recurved.

Valves equally convex above. Right valve somewhat depressed Ijelow,
comparatively higher than the left.

Hinge-line straight, longer than the leiiutli ol' the shell.

Beaks sub-anterior, obtuse, nearly erect, prominent. Umbonal region
gibbous, oblique.

The anterior extremity is scarcely alate or anrionlnte. consisting of a
rdunded extension, straight above and slightly sinuate at the base. Wing
comparatively large, triangular, joining the body of the valve near the poste-
rior extremity, defined by the crowding and curving of the concentric striae ;
margin nearly straight for five-sixths of its extent, then acutely recurving;
extremity prolonged into a mucronate spine which extends beyond the poste-
rior limit of the valve, in the right valve the wing is less deeply sinuate.

LAMELLIBRANCHIATA. 177

Test thin, marked by closely arranged concentric strige, which at irregular
intervals are crowded into fascicles, producing a gently undulated surface.
On the wing the stri;>? are closely arranged, and just below the hinge-line
afe turned backward along the spiniforni extension of the wing.

Interior unknown. Ligamental area narrow, having several fine, grooves
parallel to the hinge.

One specimen has a length from beak to base of 24 mm., height 15 mm.,
hinge-line about 20 mm. The corresponding right valve has a length of
20 mm., height 15 mm., hinge-line 26 mm. The largest specimen observed
has a length of 32 mm., height 21 mm., hinge-line, to the origin of tlie
spine, 20 mm. Small specimens are often less than 10 nnii. in length and
height.

This species, occurring abundantly in the Hamilton gioup, closel}' resembles
Avicula spinigera of Conrad, from the Chemung group. In the comparison of
large numbers of specimens, the diflferences are so slight that specific distinc-
tion is not always apparent. The Chemung forms are usually more oblique,
but this is not a constant character ; the wing is smaller and less extended
along the posterior slope ; the right valve is narrower and more oblicjue, and
the sinus in the margin of the wing is narrower and deeper than in the right
valve of the Hamilton form.

Formation and localities. In the shales of the Hamilton group at Norwich,
Chenango county ; Middleville, Schoharie county, and Leonardsville, Madison
county, N. Y.

Leptodesma spimgerum.

PLATE XXI, FIGS. 10-13; AXD I'LATE LXX,XIX, FIG. 1.

Avicula spinigera, Conrad. .Jour. Acad. Nat. Si-i., Phila., vol. S, ]i. 2:-!7, jil. 12, tig. 8. 1S42.
Ptenmite-s spinigerus (Conrad), S. A. Miller. Cat. Amer. Pal Foss., p. 202. 1877.

Leptodesma spinigerum (Conrad), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 21, tig-s.

10-13. Jan., 1883.

Shell of medium size, sub-rhomboidal ; liody ovate, oblique to the hinge at an
angle of about 45° ; length one-third greater than the height ; ante-byssal

ITS PALEONTOLOGY OF NEW YORK.

mar<::in truncate at the extremitv, curving below into tlie sinus: ))asal
margin rounded, somewhat abruptly recurved posteriorly.

Left valve regularly convex below, gibbous al)Ove the middle. Right
valve depressed-convex below and abruptly gibbous above.

Hinge-line straight, (and including the spine) equal to or greater than the
length of the shell.

Beaks sub-anterior, prominent. Umbonal region abruptly gibbous, sub-
tending an acute angle.

Anterior end short, dcdncd by tlie oblique byssal depression wliicli extends
to more than oiic-tliinl thi' length of the valve below the Ijeak ; extremity
obtusely angular. Wing not large, joining the body nearly at the posterior
third ; margin oblique below, acutely recurved above, the greatest concavity
being just l)elow the cardinal extension : extremity pro(hiced into a long
spiniform process.

Test tliin, marked at irregular intervals by strong concentric lanieike, with
intermediate fine striae. The lamellne are stronger on the anterior side and
obscure on the wing. The casts are often nearly smooth.

Interior unknown.

A specimen of medium size has a length of 29 nun., height 'Jn mm., liinge-
Hne to base of spine, \'l mm. A smaller specimen has a length of 'JO mm.,
height 14 mm., hinge-line, to base of sjjine, VI mm.

Tliis specii's (;losely resembles L. Rogers/, but is distinguished l)v the obli(pie
and more extended byssal depression, sliorter wing, and more rounded basal
margin.

Formation and localities. In sliales of tlie Chemung group, on the Chemung
river above Elmira, and along the Blossburg railroad near Painted Post, N. Y.

LAMELUBRANCHIATA. 179

Leptodesma longispinum.

I'l.ATE XXI, FIUS. U, 17-1!) ; AND PLATK LXXXIX, KIGS. i-i.

Aviriila loiii/ixpiiia. Hall. Geolofr- Surv. N. Y. : Rcji. Fnurth Dist., p. 202, fiy. S. 1848.
Pteriiiea lovgi^y'nia (Hall), S. A. Miller. Cat. Amor. Pal. Foss. 1877.

Leptodesma longiKpinum, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 21, tigs. 14, 17-19.

.lau.. 1S88.

Shell above the medium size, sub-rhomboidal ; body elongate-ovate, very
oblique ; length greater than the height, often nearly double ; margin from
the byssal .sinus to beyond the ba.se In^oadl)- rounded ; posterior margin
extended and al)ruptly recurved.

Valves, in young specimens, sub-equally convex ; in older specimens the
right valves are somewhat less convex.

Hinge-line straight ; length equalling or greater than the length ol' the vtilve.

Beaks anterior, prominent, obtuse, nearly erect, arching over the hinge-line.
Umbonal region gibbous, subtending an acute angle.

Anterior extension scarcely auriculate, rounded in front, straight above.
Wing small, very narrow-triangular ; mtirgin deeply sinuate, the bottom of
the sinus being close l)eneath the hinge-line; extremity protluced into tin
elongate spine.

Test thin, marked by fine, irregular, concentric strijB of growth, which
are abruptly recurved on the post-cardinal slope, and extend along the margin
for nearlv half the length of the l)odv before recurving into the wino;. The
stria) are more elevated and crowded on the anterior side.

The original specimen of this species has a greatest length from beak to
base of 42 mm., height 24 mm., hinge-line al)out 38 mm. A small right
valve has a length of 22 mm., height 12 mm., hinge-line 24 mm.

This species resembles L. Rogersi, but the shell attains a larger size ; the
body is more oblique to the hinge-line, ;ind the posterior extremity more
abruptly recurved ; the wing is smaller and not extending so far down the body
of the valve, the sinus is narrower with the deepest portion just beneath the
hinge ; the spine is stronger and more distinctly defined ; the right and left

180 PALAEONTOLOGY OF NEW YORK.

valves are the same in form; the sinus in the wing of the right valve is not
so deep as in the left valve, liut nuu'ii dreper tlian in the right valve of that
s]>eoies.

The original specimen is iUnstrateil in lignre 14 oC plate xxi, and ligures 17,
IS, T.I are right valves occurring in the same jjeds.

This form is associated with Avicula spinigera of Conrad, wliich is a smaller
siiell, less oblique, narrower, and witli a more angidar anterior extremity.

Formation and localities. In the Clicnumg grou]), at Painted Post, Steuben
county, between Corning and Kluiini. and at Chemung Narrows, N. Y.

LePTODESM.V SUUMARUI, U. Sp,
PLATK LXXXIX, FIGS. 5, G.

SiiF.LL of medium size, suh-rliouiboidal : body narrow, very ()))liquely-ovate ;
length soraewh;it K'ss tlian twice the height; margin very broadly curving
from the anterior extremity to the base ; basal margin rounded and :dirupt!y
recurved at the post-basal extremity.

Left valve ([uite convex; the greatest convexity about one-third the length
of the valve below the a])ex. Right valve unknown.

Hinge-line straight; length about equal to the height of the shell.

Beak sub-anterior, obtuse, prominent and arching over the hinge-line.
Umbonal region gibbous, subtending an at-ute angle.

Anterior extremity short, acute, straight above, obli(iue l)elow. Wing
small, narrow-triangular, extending to a [Joint below the middle of the length
of the shell ; margin concave ; extremity acute, probably spiniibrm.

Test thin, marked by lamellose, often fasciculate strite, which are more
crowded on the anterior side and byssal depression, and more regular and
distinct on the wing.

Interior unknown.

Tliree .specimens of left valves have res])ectively the following dimensions :
length 42, 40 and .'Ki nun., height 24, 27 and 24 mm., and hinge-line about
20, 24 and 24 nnu.

LAMELLIBRANCHIATA. 181

This species (lifters from L. longispinum in the wider ami somewhat less oljlique
1jo(I\ , with more reguhirh" romided posterior extremity ; the sinus in the wing
is less acute and farther below the cardinal line, also in the absence of the strong
posterior spine of that species.

Formation and locality . In the Chemung group, near Elmira, N. Y.

Leptodesma robustcm.

I'LATE XXI, FIGS. 15, IK, -20; AM) FTw\TK LXXXIX. FIG. 8.

Leptodesma mhitstuiii. Hall. Piil. N. V., vol. v, pt. 1. Plates and ICxplaiiatidiis : PI. 21. fiffs. l.'i, 16.20.

Jan.. 1SS3.

Shell large, sub-rhomboidal ; body obliquely ovate ; length much greater
than the height ; ante-byssal margin rounded ; straight below, or scarcely
impressed by the sinus, making a broad curve around the base to the post-
basal extremity and thence abruptly recurving toward the beak.

Left valve gibbous above, regularly convex below the middle ; the greatest
convexity about one-third the length of the valve from the beak. Right
valve moderately convex in the middle. Hat below and scarcely gibbous on
the umbo.

Hinge-line straight, about ecpial to the length of the shell.

Beaks nearly anterior, obtuse, sub-erect, very prominent, rising above the
hinge-line. Umbonal region gibbous, prominent, ahruptly elevated along the
post-umbonal side for more than half the length of the shell, then merged in
the general convexity ; on the anterior side obscurely limited by a broad
undefined depression. Umbonal angle acute.

Anterior extremity scarceh* auric ulate. Wing small, narrow-triangular,
extending about hall' the length of the valve, defined by the curving of the
striae; margin strongly concave, the deepest concavity just ])elow the hinge;
cardinal margin thickened and extended into a strong spine. In the right
valve the wing is larger and broader, and the sinus less deep ; the anterior
extremity corresponds with that of the left valve.

Test moderately thick, marked by fine concentric striae which Ijecome

isii PALJEOXTOLOGY OF NEW YORK.

more nuiiRTous anil fosciculato at irregular intervals, proflucing a sligiitlv
luiilulated snrlace, crowded iiiid laniellose on the anterior.

Interior iinkiKiwn.

A specimen of a left valve lias a length, from hcak to hase, of 4o mm.,
height 29 mm., and hinge-line to the base of the spine 'I'i mm. A right
valve, referred to this species, has a length of 32 mm., liciiilit 27 mm., and
hinge-line, exclusive of the .spine, 31 mm.

This species is larger and more rohust tiiaii L. longispinum ; the body is wider,
less ol)liqne, and less abruptly recurving at the post-basal extremity ; the wing
is larger and the greatest depth of tlio sinus not quite so near the cardinal
line; the stride do not recurve so alirii|itly forward on the posterior slope; the
right valve is proportionally higher; the wing i.s less deeply sinuate, and the
spiniform extension is shorter.

Compared with L. Morto«/, the body of the shell is less obliijuc ami moic
expanded, while the Aving is much smaller and the simis nearer the hinge-line.

Furmalion and localitij. In the middle portion of the Chemung grouj) at
Painted Post, Steuben county, N. Y.

LkI'TODESMA AgASSIZI. n. S|).

n.ATK I,.\.\.\I.\, FIGS. 17-l!l

Shell of medium size, sub-rhomboidal ; l)ody broadly ovate, obli»[ue to the
hinge-line at an angle of from 50'' to o5° ; length nearly one-third greater than
the height ; anterior margin broadly rounded below the In'ssal sinus; ventral
margin regularly curved ; more abruptly curved at the post-basal extremity.

Left valve moderately convex below, more convex al)ove and gibbous on
the umbo, llight valve less convex.

Hinge-line straight, about equal to the heiglit of tiie valve.

Beaks snl)-anterior, scarcely directed forward, prominent, rising a little
aJKJve the hinge-line. Umboual region moderately gibbous, subtending an
acute angle.

Anterior end large, obtuse, truncate above and curving below into the

LAMELLIBRANCHIATA. 183

byssal siiiu.s, limited by an oblique depression which reaches to near the
middle of the length of the valve. Wing small, joining the body ))elow the
middle ; margin oblique below and abruptly concave just beneath the cardinal
line, recurving and produced into ii short spiniform extension. The right
valve is less convex, the wing larger and more extended along the posteiior
slope.

Test thin, mai'ked by fine, distant, lamellose striae with intermediate finer
lines. The stronger strite are more conspicuous on the anterior. The
partial casts are nearly smooth.

Interior unknown.

One specimen has a length of 29 mm., height 23 mm., hinge, to base of .spine,
li") mm. Another example has a length of 26 mm., height 10 mm., hinge, to
base of spine, 15 mm.

This species Ijears a general resemblance to L. spinigeruni, witli which it is
sometimes associated, l^ut the l)od\- is more erect and much wider below ; the
wing is somewhat wider, the spine shorter, and the striae less strongly marked.

Formation and locality. In the middle portion of the Chemung group, on the
Chemung river, between Elmira and Waverly, N. Y.

Leptodesma protextum.

PLATE XXI, FIGS 2-2, 23

Avieula protextUy Cokrad. Jour. Aoad. Nat. .Sci., Pliila.. vi>l. viii. p. 238, pi. 12, fig'. 6. 1842.
Pterinea prolexta (Conrad), S. A. Miller. Cat. Amer. Pal. Foss., p. 202. 1877.

Leptodesma protextum (Conrad), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PL 21, figs. 22,

28. Jan., 1883.

Shell small, sub-rhomboidal ; body elongate-ovate, very oblique ; length nearly
twice as great as the height ; anterior margin below the byssal sinus, oblique ;
base broadly rounded and abrui)tly recurved on the post-basal extremity.

Valves sub-equally convex ; the greatest convexity is above the middle of
the length, becoming less toward the posterior side, which is somewhat
depressed. The right valve is apparently a little smaller than the left.

Hinge-line straight, about equal to the length of the shell.

1S4 PAL2E0NT0L0GY OF NEW YORK.

Beaks near the anterior ciid nl' the xalvc ()l)tnse, rmimlcil. iiiiiinini'iit,
ini'lined lorwainh Uiiihonal reiiioii imiinw, gihhoiis lor a short spaee helow
the hiuge, suhtendiug an acute angle.

Anterior end scarcely anriculate, ahniptly rounded hi the left valve, pointed
in the right valve, limited hy a broad, nndelined depression, wliiiji is le.ss
marked in the right valve. Byssal sinus shallow. Wing narrow-tiiangular,
joining the IkxIv near the posterior extremity ol' the valve, defined hy the
direction of the striae; margin deeply conca\e, the greatest concavity just
beneath the hinge-line; extremity produceil into a sharp spine which extends
nearly as for as the posterior margin of the shell.

Test thin, marked by concentric stria? of growth, which ;ire crowded into
fa.scicles at irreirular intervals, giving a somewhat wrinkled oi- undulatinsr
surface. On the anterior side the stria' are crowded and laraellose, while
they are quite regular and closely arranged over the wing. On the external
shell the stria? ai-e elevated into regular, equidistant lamellfe. In the exfoliated
shell, or partial casts, the surface presents obscure or obsolescent radii which
appear to belong to the intimate shell-structure, and which are not shown on
well-preserved specimens.

Interior uni^nowii.

The largest specimen observed Ikis a length of 2li iniii.. height \'-\ uini.,
hinge-line li<l nnn. A similar right valve has a lengtli of I'^i mm., height
111 mm., hinge-line hi mm. The specimens are usually smallei- than those
figured.

This species, in form of body and in the cimcentric stria?, resembles
L. Inngispinum ; but the anterioi- extremity (especially in tlii' right valve) is
narrower, the wing is extended farther down the body of the vahe. ami the
spine is less produced.

This shell in its usual condition of prest'rvation (that is. having the spinilbrm
process of the wing broken oil", or the wing partially covered) presents the
characters described by Mr. Conhah. although not illustrated in his figure. A
specimen of this species is labelleil in the liami writing of Mr. Conr.vd, Avicula
protexta, and therefore the name is retained.

LAMELLIBRANCHIATA. 185

Formativn and localities. In the Chemung group at Chemung Narrows, N. Y.,
and Tioga county, Pa.

Leptodesma Becki.

PLATE XXII, FIGS. .-J-o.

Leptodesma Becki, Hall. Pal. N. V.. vol. v. pt. 1. Plates and Explanations: PI. 22, Hgfi. 3-5 (and

tiif.s. (i anil 7 in rn'or). .Ian., 1883.

Shell of medium size, sub-rhomboidal ; body oblique, narrowly ovate in the
left valve ; length more than one-third greater than the height ; anterior
margin oblique, extending in nearly a direct line into the broadly rounded
basal margin ; post-basal margin produced, not abruptly recurved into the
wing.

Left valve gibljous except in the lower part. Right valve less convex.

Hinge-line straight, less than the length of the shell, and greater than
tlie height.

Beaks at about the anterior third of the hinge-line, obtuse, directed
forward and arching over the hinge. Umbonal region giblaous, scarcely
defined anteriorly, Init well-marked posteriorly by the aljrupt slope of the
side. Umbonal angle acute.

Anterior end truncate, acute at the extremity. Wing of medium size,
not distinctly limited, joining the body nearly at the posterior extremity ;
margin concave ; extremity produced into a short spine. The right valve
is proportionally higher, the body less distinctly defined, and the wing larger.

Test thin, marked b}' concentric stria?, whicli are crowded and somewhat
lamellose in front, and closely and evenly arranged on the wing. The liinge-
line has a sintjle narrow sfroove.

A left valve has a length of 28 mm., height 17 nun., hinge-line about
22 mm. A detached right valve has a length of 2'.> mm., height 20 mm.,
hinge-line 30 mm.

This species resembles L. rohustum in general expression and in .the sinus of
the wing, but the body is narrower, more regularly convex, the base less expanded,
24

JbO PALEONTOLOGY OF NKIV YORK.

and the basal margin and tin- stria' along the posterioi' slope are not so aljrujitly
recurved.

Formation and localities. In the Chemung group, near Corning, Chemung
county, and Portville, Alleghan}- county, N. Y.

Leptodesma disparile.

I'l.ATE XXV, FIGS. 2-4 ; AXIi PLATE LXXXIX, FIGS. -23, 24.

LejtlodesvM dliparile, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Exjilanations : PI. 25, figs. 2-4.

Jan., 1883.

Shell of small or medium size, sub-rhomhoidal : Kody ovate, oblique to the hinge
at about 45°; length more than onc-tliird greater than the height in the
left valve; ante-byssal margin ohrKjue, gently curving into tlu' sinus; basal
and ])osterior margins regularly rounded.

Left valve convex below, gibbous above. Right valve flat or concave
below, depressed-convex in the middle, and gibbous on the umbo.

Hinge-line straight, greater than the length of the shell.

Beak sub-antorior, prominent, rising above the hinge-line, directed slightly
forward. Umbonal region gibbous, subtending an acute angle.

Anterior end large, somewhat produced, limited by a nearly \ertical liyssal
depression ; extremity obtusely angular. Wing somewhat large. Joining the
body near the posterior extremity ; margin oblicjue below, concave above the
middle, ami produced into an elongate spinit'orin judcess. The right valve is
smaller, the wing more extended and less dciiiu'd, while the anterior end is
large and well defined by the byssal sinus and sulcus.

Test marked by concentric, lanicllose ridges with intei'mediate finer lines
of growth; the lamellae are sometimes more distinct on the right valve.

Interior unknown.

A left valve has a length of 28 mm., height 2U nun., hinge-line more tlian
30 mm. A right valve has a length of 30 mm., height 18 mm., hinge-line
33 mm.

LAMELLIBRANCHIATA. 187

This species is distinguished from L. Rogersi and L. spinigerum by the large
anterior end, narrower undio, more extended wing, with less deeply sinuate
margin, less convex right valve, and the regular concentric lamellose ridges
of the surface.

Formation and localities. In sandstones of the Upper Chemung group, McKean
county. Pa. ; and Farmer's Valley, Cattaraugus county, N. Y.

Leptodesma sociale.

PLATE XXI, FIGS. Sl-M (33, 34 ?).

Lfptodesma sociale, Hai.l. Pal. N. Y.. vol. v. pt. 1. Plates an<l Explanation.s : PI. 21. tig-s. 24-2S (33, 34 ?).

Jan.. 1883.

Shell small, sub-rhomboidal ; body broad-ovate, oblique ; length greater than
the height ; anterior margin nearly straight and quite oblique ; base regu-
larly rounded ; post-basal side somewhat extended and abruptly recurved.

Left valve convex, gibbous in the upper part, more convex than the right
valve, which is moderately convex above and depressed-convex or flat lielow.

Hinge-line straight, sometimes greater than the length of the shell.

Beaks at about the anterior third of the hinge-line ; the left beak promi-
nent, obtuse ; the right beak less conspicuous. Umbonal angle acute.

Anterior extremity suli-auriculate, straight above, slightly extended.
Wing triangular, joining the body of the valve below the middle of its
length (measured from hinge to base) ; margin regularly concave ; extremity
produced into a spine, which, in jjerfect specimens, reaches beyond the
margin of tlie valve. In the right valve the wing is less distinctly defined,
and the sinus not so deeply concave.

Surface marked by fine concentric stria?, which at somewhat regular
intervals are elevated into sharp, conspicuous lamellaj, or sometimes into
fascicles of strige producing elevations. These become crowded and irregular
on the anterior of the valve, and are very regular and uniform on the wing
and on the right valve.

Interior unknown.

188 PAL/EONTOLOGY OF NEW YORK.

A specimen of a left valve has a lenjrth of 10 iiiiii., iieiiiht T.o nun., iiiniic-
line alioiit 111 mm. A similar specimen lia.< a Icnirth of 11 mm., liei<i;ht G.5
mm., and hinge-line about 11 mm. A rii;ht valve has a length of '.I nun.,
height (') mm., hinge-line about S mm. iVnother one has a length of lii mm.,
height 11 mm., hinge-line about Ki mm.

This is a small and aliuiidaiit species, often occurring in great inimbers on
the surfaces of A\:\\\- lavers. It is distinguished hv its form and the rescular
lamellose appearance ol' the surface.

Formation and localities. In tiie shales of the Chemung group at Connewango,
Cattaraugus county; Nanticoke Springs, Broome county, and south of Ithaca,
N. Y.

LkPTODES.M.V I'OTENS.

I'I,.\TE X.\I, KKiS. 21, »); PI..\TK XXU, KU;> M, IJ. 1(1, (in?) ■>! ; axd PLATE LXXXI.X. KILJ. 7

LeptiidfrSinu jMitens. H.ai.l. Pal. N. V., vol. v, jit. 1. Plates and Exiilanaticns : PI. 21. lifrs. -Jl. 8(1; |il. 2l'.

tig-s. 11. 1.'. H). 21. .Jan.. ISSS.

iSiiELi, large, sub-rhomboidal ; body ovate, oblicpie, l)road IjcIow: length more
than one-third greater than the height ; ante-byssal margin sub-truncate,
erect, ()l)li([ue below, basal margin broadly curving ; posterior margin broad,
extended and abruptly recurving at the upper extremity.

Left valve convex, gibbous al)()ve ; the greatest convexity at one-third the
height of the shell from the beak. Kigiit valve almost e(|ually convex, more
alii'ujitly gibbous on the uml)o. and coinparatively shorter and wider.

Hinge-line straight, about e(|ii;d to the length of tlie shell.

Beak sub-anterior, obtuse, erect, prominent, arching over the hinge.
Umbonal region gibbous, very prominent, limitt-d anteriorly by a shallow
depression extending from a point anterior to the beak to the margin at one-
third the height of the shell below the hinge-line; posterioily limited by the
abrupt post-cardinal .slope. Uinlion.d angle acute.

Anterior extremity extended and angular. \\ ing large, trianguhir, joining
the body near the posterior extremity, distinctly limited ; margin l)roadly

LAMELLIBRANCHIATA. 189

sinuate ; extremity produced into a strong spine (the extent of whicli is
unlinown).

Surface marked by strong concentric lines of growth, which are crowded
into small fascicles at irregular intervals on the body of the shell, and become
lamellose expansions on the anterior. On the wing they appear as sharp
equidistant lamella'. Casts of the interior show the concentric striae in a
sut)dned condition.

Interior unknown.

The largest left valve observed has a length, measured from beak to base,
of 02 nun., height 46 mm., hinge-line, exclusive of the spine, 58 mm. A
smaller specimen has a length of 57 mm., height 39 mm., hinge-line, to base
of spine, 58 mm. A right valve referred to this species has a length of M6
nun., height 28 mm., and hinge-line, to base of spine, 35 mm.

This species more nearly resembles L. rohustum than anv of the forms here
described ; but it is larger, the wing proportionally larger and distinctly limited,
and the siiuis ol" the wing more central. The right valve is also more convex
and the wing more deeply sinuate. It occurs in the upper members of the
Chemung group, associated with Spirifera Venceuili, while L. robustum is found
only in the middle of the series.

It is a larger and more robust shell than L. Mortoni, and the right valves
are very unlike.

Formation and localities. In tlie Upper Chemung group at Olean, Portville,
Cassadaga lake, and in loose specimens collected near Panama, N. Y.

Leptodesma potens, var. juvens.

PLATE XXU, FIG. 16.

Leptodesma potens. mr. jmvn.'i. Hall. Pal. N. Y., vol. v, jit. 1. Plate.'^ and Rxiilanatioiis : PI. 22, tig-. 10.

Jan., 18S3.

Shell small, rhomboidal ; body ovate, oblique ; the greatest length more than
once and a half the height; anterior margin oblique, very broadly curving
below ; post-basal extremity rounded and abruptly recurved.

Left valve convex below, vexy gibbous and ventricose in the middle and
above. Right valve unknown.

190 PALEONTOLOGY OF NEW YORK.

HiiiiiC-line straight, less than the length of the shell.

Beak obtuse, situated at the anterior third of the hinge-line, prominent,
arching over the hinge-lint' and iii( liiifd slii:litly forward. Umbonal region
ventricose, ob.scurely limited anteriorly by au undefined depression, and on
the posterior side by the abrupt and almost vertical post-umbonal slope.
Umbonal angle acute.

Anterior end sliort, triangular; cxticiiiity acute. Wing broad-triangular,
joining tbe Ixxly of the shell near the posterior end : margin regularly
concave ; extremity acute.

Test thin, marked by extrenudy fine, regular concentric striae, which are
crowded into fascicles on the anterior end.

Interior unknown.

The specimen described has a greatest leiigtli of "J") mm.. heiLLht I "i mm.,
hinge-line 22 mm.

This shell resembles L. potens, but it is apparently more extended and aiiite
in front, sub-trnncati' on the posterior end; the wing joins the body near
the posterior extremity, and its margin is less deeply sinuate than L. potens.
These variations appear in comparison with the older individuals of that species
and cannot be taken as positive evidence of specifie diiTerence, while at the
same time their common characters may 1)6 insnflicient to unite them.

Formation and locality. In the Chemung group at East Randolph, Cattaraugus
county, N. Y.

Leptouesma Moktom.

I'LATE XXI, KIUS. 2!l, :il, M; AND ri.ATK LXXXIX, FIGS. !)-Il.

I^ptodesma Muftinii. Hall. PjiI. N. Y., vol. v, ))t. 1. Plates and Explanjitioii." : PI. •l^. fiir^. 2il. HI, :W

(pi. 22, tiir. 20 in en-or). Jan., ]88:^.

Shell above the medium size, sub-rhomboidal ; body elongate sulj-ovate, very
oblique; length more than one-half greater than the height ; ventral margin
broadly curving to tlie Ijase; the posterior margin extendeil ami abruptly
recurved.

LAMELLIBRANCHIATA. 191

Left valve convex, gibbous above. Right valve depressed-convex below,
and abruptly gibbous at the umbo.

Hinge-line straight ; length less than the length of the shell.

Beaks sub-anterior, obtuse, erect, prominent, arching over the cardinal
line. Umbonal region gibbous and gradually sloping down to the general
convexity, abruptly limited on the posterior side, subtending an acute angle.

Anterior end extended, acute and nasute. Wing large, triangular, slightly
convex, joining the body of the shell more than two-thirds of the length
below the beak; margin symmetrically concave; extremity produced and
very acute. In the right valve the anterior end is broad and flat ; the wing
is large, with no defined limit Ijetween it and the body of the valve.

Surface marked by elevated concentric striae which, at irregular intervals
are fasciculate, producing undulations on the surface. This character is often
marked on the front of the shell where the fascicles are composed of three
or four distinct striae.

Interior unknown.

A specimen of the left valve has a length, measured from beak to base, of
44 mm., height 30 mm., hinge-line about 38 mm. Another example has a
length of 45 mm., height 25 mm., hinge-line 32 mm. A right valve measures
43 mm. in extreme length, height 30 mm., hinge-line al)out 34 mm.

This species bears some resemblance to L. robuslum, but the body is more
oblique and not so broad below ; the anterior extremity is acute ; the wing-
larger, more extended along the valve and very symmetrically concave on the
margin. The form of the shell is very similar to L. longispinum, but difters
by its larger wing, the broader sinus and more regularly rounded posterior
extremity, and in the latter respect it resembles L. Shumardi, while it is
otherwise very different.

Formation and localities. In the Chemung group at Portville and Little
Genesee, Alleghany county, N. Y.

192 PALEONTOLOGY OF NEW YORK.

LePTODESMA BlM,IN(iS[, 11. ^p.

n.A IE i.xxxix. Ki(;s ij-i.-,

SiiKi.i. larji't'. siili-rlioinhoidal ; lioily cloiigaty-ovatc, or sul)-r\ rniili-i<'al, \vv\
oliliqiie; leiijitli alioiit twice the height; ante-by.ssal margin rounded,
heconiing (straight or slightly concave at the sinus; ventral margin hroadh-
(Hiving; posterior margin extended, acutely recurved at the i)Ost-l)asal
extremity.

Let"t valve gihhous on tin' iiiuIk). convex lidow. Kiuiit salve ind\no\vn.

Hinge-line straight ; length, including the spine, nearly (M|n,il to the length
of the valve.

Beak sub-anterior, obtuse, slightly ol)li(iue, prominent, llmlxnial region
somewhat gibbous, subtending an acute angle.

Anterior end limited by a slndlow byssal depression, acute and iiasute at
the extremity. Wing long, narrow-triangular, extending below the middle
of the valve; margin sinuate; extremity produced into a spine.

Test thin, marked by line concentric stria' which aic alinipth arclu'd on
the posterior slope, regular upon the wing, and crowiled into line iiiegular
fascicles which are conspicuous on the anterior. Some speciineiis show sharp.
elevated, lamellose stria? at e([ual distances on the surface of the body. The
surface characters vary with the different states of cxfoliMtion iiiid maceration.

The lArgest specimen observed has a greatest length, from beak to ba.^e,
of -u mm., height -iC) mm., hinge-line, to base of spine, >]•") mm. A small
example of the lel't valve has a length of o4 mm., height 1<S inni.. ami hinge-
line about :-»r> mm.

This species is more elongate and oblique than L. longispinum, the wing extends
farther down along the posterior slope, and the anterior extremity is I'nlh r and
more acute.

Formation and localities. In the (hemnng group at Panama, N. V. Other
specimens from near Elmira, >.'. Y., and Manslield, Tioga countx, Pa., are
referred to this species with reservation.

LAMELLIBRANCHIATA. 193

Leptodesma Matheri.

PLATE -\Xn, FIGS. S, !), 10; AND J'LATli LXXXIX. flG. iS.

Lfptndt.fiiin Mathiri, Hall. V-A. N. Y.. vol. v. jit. 1. Plates ami Exiilanations : PI. 22, fiffs. S-10.

Jan.. 1S83.

Shell of medium size, rhoiiiboidal ; body ovate, oblique at au angle of 45° with
the hiuge-liiie ; length about one-half greatei" than the height ; ante-byssal
margin vertical in front, joining the broad curvature of the basal margin ;
posterior margin produced and abruptly recurved.

Left valve moderately convex below, scarcely gibbous aljove. Right valve
shorter and less convex.

Hinge-line straight ; length much less than tlie length of the valve, Init
nearly equal to the height.

Beaks at about the anterior third of the hinge, obtuse, directed slightly
forward, not very prominent. Uml)onal region moderately gibbous, sub-
tending an acute angle.

Anterior end protluced, tiattened, acute at the extremit}-. \\n\g of
moderate dimensions, extending nearly to the posterior extremity ; margin
gently concave ; extremity produced and acute.

Test thin, marked by fine concentric striae which are tasciculate on the
body of the shell, producing an undulated appearance. The stria? are
sub-lamellose on the anterioi- and regular over the wing.

Interior unknown.

A left valve has a length of o5 mm., height 23 mm., and hinge-line about
28 mm. A similar right valve has a length of 21) mm., and height 20 mm.

This species differs from L. robustum in its comparatively larger wing, without
distinct sinus in the margin, and the more produced anterior end. It resem-
bles L. potens, but differs in its more produced anterior end, less gibbous body,
and more abruptly recurved posterior margin.

Formation and locality. In the upper beds of the Chemung group, near
Bradford, McKean county. Pa.
25

194 PALEONTOLOGY OF NEW YORK.

Leptodesma Stephanf, n. sp.

PLATE LXXXIX, FIGS. iO-.'-J.

SiiKLi, abuvf the medium size, sub-rhomboidal ; body ovate, straight on the post-
umbonal slope, oblique at an angle of from 30° to 40° with the hinge-line ;
height about five-eighths of the length ; ante-byssal margin vertically truncate
al)ove, curving below into the sinus ; basal margin broadly rounded, abruptly
recurved at the post-basal extremity.

Left valve convex, somewhat gibbous above. Right valve depressed-
convex below and abruptly gibl)Ous at the umbo.

Hinge-line straight, equal to al)()ut five-sixths the length of the valve.

Beaks sub-anterior, directed slightly forward, obtuse, prominent, rising
a little above the cardinal line. Umbonal region regularly gibbous, subtending
an acute angle.

Anterior end large, short, defined by a nearly vertical byssal depression,
which reaches the margin about one-third the length of the valve from the
anterior extremity, which is abruptly rounded or truncate. Wing joining the
body at less tlian one-fourth the length of the valve from the posterior
extremity; margin very oblique below, deeply concave above; the greatest
depth of the concavity is above the middle, whence the margin is abru])tly
recurved and produced into a spiniform extension.

Test of moderate thickness, marked by nearly equidistant lamcllose
concentric stria\ witli intermediate finer strite of growth. The lauicllose
strife are sul)du(>(l upon the wing, and very strong and irregular on the
anterior side.

Interior unknown.

A large specimen of this species has a length of 4;! mm., height 2-3 iiiiu.,
and hinge-line about 33 mm. A somewhat smaller example lias a length
of 37 nnn., height 2-5 mm., and hinge-line -Kl mm. A right valvi' measures
33 mm. in Icngtli. 24 iiiiii. in lieight, and hinge-line 2S mm.

Tliis .sjjccies resembles L. Matheri, with which it is associated, l)iit ilifVers in
its greater obliquity, more elongate outline, more extended and llatler wing,

LAMELLIBRANCHIATA. 195

which is more deeply concave on the margin and with tlie extremity more
produced ; the anterior extremity is also larger and apparently not produced.
The right valves of the two sjjecies are very unlike.

Formation and localities. In the Upper Chemung group at Bradford, Pa., and
douhtfully occurring near Elmira, N. Y.

Leptodesma lepidum.

PLATE XXI, FIG. 411; AKI) I'LATE LXXXIX, FIG. W.

LeptodesiiM lepidum. H.\Lr.. Piil. N. Y.. \(.l. \'. ]it. 1. Plates and Explanations: PI. 21. fif?-. 40. Jan., 1883.

Shell of medium size, narrow, sub-rhomboidal ; body narrowly ovate, somewhat
straight on the posterior slope, oldique at an angle of about 35° with the
hinge-line ; length less than twice the height; margin very oblique anteriorly,
curving into a marked byssal sinus; base l^roadly rounded to the posterior
extremity, which is abruptly recurved.

Left valve regularly convex below, gibbous above. Right valve very
depressed-convex, nearly flat lielow, moderately convex on the umbo,
considerably smaller than the left.

Hinge-line straight ; length more than two-thirds the greatest length of
the shell.

Beaks sub-anterior, directed forward, prominent in the left valve, depressed
in the right valve. Umbonal region narrow and abruptly gibbous in the
left valve ; depressed and scarcely defined in the right. Umbonal angle
about 30°.

Anterior end small, acute at the extremity, limited by a distinct vertical
byssal depression. Wing narrow-triangular, joining the body at about one-
fourth the length from the posterior extremity ; margin deeply concave,
abruptly recurved along the cardinal line, and extended into a spiniform
pi'ocess. In the right valve the wing is scarcely defined.

Test marked by very fine concentric striae, which are regular upon the
body and wing, and crowded and fasciculate on the anterior. In the right
valve the strias are more distant and more even in their character.

lOG PALjEONTOLOGY OF NEW YORK.

Interior unknown.

A left valve of medium size has ji length of 41 mm., hcii:lit '22 mm., leiiiitli
of cardinal line about o") mm.

'riii.-i .species diflfers from />. Ihctor \\\ its greater <>lili(|nity, broader body
below, more produced and abruptly recurved post-basal extremity, deeper and
broader byssal depression, more produced anterior end, and narrower and
more deeply sinuate wing, with a more extended extremity.

Formation and localities. In th(> central portion of the Chemung group at
Philipsburg, Alleghany county, N. Y., and below the conglomerate (.-<anie
position) in Snllivan township, Tioga county, Pa.

LeI'TODESMA CUUV.\TU.M.

I'L.VTE XXV, FIG. 5.

Ltjil'>dfxiii.:i i-amttMin. M\\.\.. l';il. N. Y., vol. v. jit. 1. Plates and Exiilauatioiis ; PI 2S, tij'-. .'). Jan., 1883.

Shell above the nn-diuin size, rhomboidal; bodv ovate, sub-arcuate above,
oblique at an angle of nearly ^^0° with the hinge-line ; length and height as 7
to 4; ante-l)yssal margin oldique above, curving into a long, .shallow sinus;
l)asal and posterior margins forming a broad, continuous curve, and abrujjtly
recurving at the post-basal extremity.

Left valve regularly convex Ijelow, gibbous above tlu' middle. Right
valve luikiiown.

Hinge-line straight; length about equal to the lengtii of the valvt-. but not
fidly .seen, as the spiniform termination is imperfect.

Beak sul)-antt'rior. proiniinMit, ilii-cctcil linwai'il. riiilioual region gibbous,
subtending an acute angle.

Anterior end large, abruptly acute at the extremity, limited liy a distinc't,
nearly vertical l)yssal depression. Wing narrow-triangular, joining the bod\
at the posterior extremity; margin very oblique l)elow, concave above,
abruptly recurved just l)elow the cardinal line and extended into a .spiniform
process. In a cast of the left valve tlic wing is distinctly separated Ironi
the body by a marked liu row.

LAMELLIBRANCHIATA. 197

Test moderately thick, marked liy elevated lainellose striae, with finer
intermediate lines.

Interior unknown.

The specimen described has a length of 42 mm., height 24 mm., hinge-
line, to base of spine, 30 mm. The sj^ine is proljalily extended from o to
10 mm. beyond.

This species resembles L. lepidum, Init differs in its more gibbous form, larger
and more obtuse anterior extremity.

Formation and locality. In sandstones of the Upper Chemung group, McKean
county, Pa., on the road from Bradford to Farmers' Valley, Cattaraugns
county, N. Y.

Section b, umbonafa.
Leptodesma Medon, n. sp.

PIRATE XC, FIGS. 1-1.

Shell of medium size, snb-rliomboidal ; body broad-ovate, oblique at an angle
of about 60° with the hinge-line ; length nearly one-third greater than the
height ; ante-byssal margin curving slightly outward, concave at the sinus ;
basal and posterior margins broadly rounded, passing directly into the wing.

Left valve gibbous above, depressed-convex below. Right valve some-
what less convex than the left. The right valve appears to have been
somewhat smaller and the base more extended than in the letl valve.

Hinge-line straight ; length a little greater than the height of the shell.

Beaks at about the anterior third of the hinge, acute, prominent, arching
over the hinge-line. Umbonal region gibbous, descending almost vertically
on the posterior, and sloping abruptly on the anterior side. Umbonal angle
acute.

Anterior end short, separated from the body by a marked sinus; extremity
angular, gently rounded below. Wing not defined, broad-triangular, reaching
nearly to the posterior end of the body ; margin slightly concave ; extremity
acute.

198 PALEONTOLOGY OF NEW YORK.

Test thill, marked by concentric striiTJ, which, on the bod}' of the shell,
.are crowded into fascicles and assume a distinct regularity in passing over
the wing. The hinge shows one or two slender parallel grooves.

Three similar specimens of the left have respectively the following
dimensions: length 32, 32 and 33 mm., hciglit 22. 2^") and 23 nun., and
hinge-line 25, 27 and 25 mm.

In this species the l)ody of tlie shell resembles L. robustum and L. potens, but
is less oblique to the hinge-line, tln' wing less (U-lined. and its postci'ior
extremity not produced into a spine.

Formation and locality. In the upper part of the Cheuuuig group, Lawrence-
ville, Tioga county. Pa.

LkPTODKS.MA UMIiDNATUM.
I'L.VTK X.\n, FIG. 13; .VM> PL.iTE XC, KIG. 9.

h^ptodesiiM uiiibonutiim, Hai.l. Pal. N. V., vol. v, \>\.\. Pliites ami Rxplanations : PI. 22, tig. 13.

.Ian., 1883.

Shell of medium size, rhomboidal ; body oblique, uainjuly ovate ; greatest length
one-half more than the height ; ante-byssal margin straight or slightly
convex, curving into the wide sinus, oblique below; ventral margin broadly
rounded ; posterior extremity moderately produced, abruptly recurved.

Left valve convex, ventricose above the lower third. Right valve
unknown.

Hinge-line straight ; length less than the length of the shell.

Beak at al)out the anterioi' third of the cardinal line, directed slightly
forward, prominent and arching over the hinge. I'mltonal I'egion narrow
and ventricose, defineil anteriorly by a broad, shallow depression, which is
nearly vertical to the hinge-line, and posteriorly Ijy the abrupt depression of
the body.

Anterior end acute, triangular. ^Ving rather large, triangular, convex,
joining the body of the .shell near the posterior extremity; margin bi'otidly
concave; extremity produced, acute.

LAMELLIBRANCHIATA. 199

Test thin, marked by fine concentric lines of growtli whicli are irregularly
crowded into small fascicles, producing a slightly undulated appearance.
The stria? are strong and regular over the wing.

Interior unknown.

The left valve described has a length of 41 mm., height 27 mm., hinge-line
about 38 mm.

This species bears some general resemblance to L. potens and L. robustum, but
the l)ody is narrower, less oblique and much more gibbous, the beak more
elevated, and the posterior extremity of the body less expanded. The wing
is also much larger than in L. robustum. It is very closely allied to L. umbonatum
var. depressu?n, PL xxii, fig. 14., but differs in its smaller mucronate anterior
end ; the body is more convex and narrower below, and the extremity of the
wing more produced.

Formation and locality. In a calcareous band of the ujjper part of the
Chemung group. Twenty-mile creek, Chautauqua county, N. Y.

Leptodesma umbonatum, var. depressum.

PLATE XXn, FIG. 14 ; AND PLATE XC, FIG. 10.

Leptodesma wnhonatum, var. depressum, Hall. Pal. N. Y., vol. v. [it. 1. Plates and Exjilanaticus: PI. 22.

fig. 14. Jan., 1883.

Shell of medium size, rhomboidal ; body very oblique-ovate ; length once and
a half greater than the height ; ante-byssal margin, Ijelow the acute extrem-
ity, regularly curving into the ventral margin ; posterior extremity produced,
with the margin gently recurving into the wing.

Left vafve convex l)elow, gibbous above. Right valve smaller, a little less
convex, abruptly gibbous on the umbo.

Hinge-line straight, somewhat less than the greatest length of the shell.

Beaks sub-anterior, obtuse, directed slightly forward, very prominent,
arching over the hinge-line.

Anterior end short, large, limited liy a broad, undefined depression ;
extremity produced, acute. Wing large, triangular, not distinctly defined.

200 PALAEONTOLOGY OF NEW YORK.

joiniii";' the hofly near the po.sterior cml : extremity produced, aoutc, and
])rol»iil)ly extended into a short spine.

Te.st marked l>y fine stria^ of trrowth whioli are irreguhirly tasciculate.
prodncing a sliglit uinkilation of tlie surface, Tlie striiv are hmiellose on
the anterior side and regular on the winu'.

Interior unlvuown.

The specimen descrilied has a greatest length of aljout 40 mm., heiglit li")
mm., and hinge-line •!•"> mm.

This form difters from L. unibonaium in tlie lesser convexity and greater width
of the lower part of the hody ; less ahrujjt depression on the anterior side from
the umho; the posterior slope less elevated and defint'd lielow the middle, and
a much larger ante-lnssal jtortion of the shell.

Formation and locality, in the upper part oi' the (.'henumg group, Najioli
Centre, Cattaraugus county, N. Y.

LeI'TODES.M.V X.VVIKORME.
IM.ATK .WII, FIG. 15; ANii I'LATK -WUI, Flli. ].

Leptodemna nav'ifonm. Hall. Pal. N. V.. vol. v. |it. 1. Phites and Kxplanalidiis : PI. 22. titr I.");

pi. 28. tif.'. 1. .Ian.. ISSS.

Shell helow the medium size, rhomboidal ; body very oblique, short-ovate;
length nu)re than one-third greater than the height ; anteiior extremity
subtruncate ; margin curving to the broadly roinided lia.se; posterior margin
slightly proiluced, gently curving forward, nearly vertical.

Left valve convex below, very gibbous above the middle. Kight valve
depressed-convex below, gibbous aliove.

Hinge-line straight, more than one-third greater than the height of the
shell.

Beaks obtu.se, situated at the anterior fourth of the liinge-liiie. prominent.
directed slightly forward. Umbonal region gibbous, sloping abruptly into
the wing.

LAMELLIBRANCHIATA. 201

Anterior end short, acute. Wing large, not distinctly limited, extending
almost ti) the posterior extremity; margin scarcely concave below;
extremity produced, acute.

Test marked by fine concentric striae, Avhich are crowded into fascicles at
nearly equal intervals, rounded upon the upper part of the ))ody,and sub-angular
on the lower part. The stride are crowded and lamellose on the anterior ;
on the posterior slope they make a short abrupt curve, passing over the wing
with a gently forward direction and curving backward just below the hinge-
line. In the weathered surface of the right valve the concentric undulations
are stronger, the post-cardinal slope is marked b}' strong interrupted radii
which appear to belong to the intimate structm-e of the shell. The hinge is
marked by a single narrow groove.

A specimen of the left valve has a length of 22 mm., height 14 mm., and
hinge-line about 21 mm. A right valve occurring in the same association
has a length, from l)eak to base, of 2(i mm., height 18 mm., and liinge-line
about 2f5 mm.

This species is quite unlike any here described.

Formation and locality. In the lower beds of the Chemung group at the
Inclined Plane, near Ithaca, N. Y.

Leptodesma Cadmus, n. sp.

PLATE XC, KIGS. 11, 7.

Shell of niediiun size, rhomboidal ; l)ody oljliquo, narrowly ovate or sul)-
cylindrical ; length nearly one-third greater than the height ; ante-byssal
margin somewhat vertically truncate, sloping below into the broadly curving
base ; posterior margin abruptly curved.

Valves convex, gibbous above ; the right valve smaller than the left.

Hinge-line straight, nearly equal to the height of the shell.

Beaks at about the anterior third of the hinge-line acute, directed forward,
prominent, arching over the cardinal line. Umbonal region abruptly gibbous,
subtending an acute angle.
26

202 PALAEONTOLOGY OF NEW YORK.

Anterior end small, terminating in a narrow nasute extension. Wing
comparatively large, triangular, joining the Ijody near the posterior end ;
surfiice concave ; margin gently sinuate ; extremity produced into a short
spiniform extension.

Test thin, marked by line concentric .stria;, which are somewhat regularly
fasciculate on the body of the shell, crowded and sub-lamellose on the
anterior, and regular over the wing, curving backward just below the hinge,
indicating a spiniform extension of the wing. On the bod}- of the right
valve tlie striae form sharp, laiucllose elevations at somewhat equal intervals.

Tlie hinge is marked In' one or two narrow, longitudinal grooves.

A left valve has a length of 34 mm., height 24 mm., and hinge-line 22 mm.
A similar specimen, somewhat vertically compressed, has a length of 36 mm.,
height 24 mm., hinge-line 25 mm.

This species resembles L. vmbonatum var. depressum, but differs in its smaller
and narrower anterior end and more cyliniliicid body, ami wing without abroad
sinus in the margin.

Formation and localities. In the upper beds of tlic Clienumg group, Steuben
county, N. Y., and Tioga and Bradford counties. Pa.

Leptodesma Creon, n. sp.

PLATE Xr, FIGS. U-i:!.

Shell below medium size, sub-rlioniboidal ; liody ovate, oblique to the hinge-
line at an angle of about 5-3°; length nearly one-third gi'eater tlian the
height; ante-byssal margin slightly ol)li(|uc or rounded, distinctly sinuate
below, then gently curving to the broad l)ase; posterior margin broad, join-
ing the wing without interruption.

Left valve convex below, giljbous above. Kight valve less gibbous than
the left and more expanded.

Hinge-Une straight; length a little greater tlian the height of the shell.

Beaks at about the anterior third of the hinge-line, sub-acute, directed
forward, prominent, arching over the hinge. Umbonal region very gibbous,

LAMELLIBRANCHIATA. 203

narrow, limited by the abrupt slope of the posterior side. Umbonal angle
acute.

Anterior end large, short, rouuded, curving into the bjssal sinus, defined
by a marked byssal depression ; extremity acute. Byssal sinus marked by a
broad, shallow curvature of the margin. Wing small, narrow-triangular, not
distinctly limited ; margin concave ; extremity acute. The wing of the
right valve is comparatively larger.

Test thin, marked by fine concentric lines of growth, which are some-
times regular or often crowded into fascicles on the body of the shell.

Cardinal line marked by a narrow longitudinal groove. Interior unknown.

A left valve has a length of 32 mm., height 21 mm., hinge-line 23 mm.
A smaller specimen has a length of 29 mm., height 20 mm., hinge-line

'>'?

mm.

This species resembles in general expression L. umbonatum var. depressum,
but it is uniformly smaller, the anterior end shorter, byssal depression nar-
rower, wing smaller, the recurving of the posterior margin of the body less
abrupt, the limits of the wing less distinctly marked, the extremity less
produced, and the umbonal region n<it so abruptly gibbous.

Formation and locality. In the upper part of the Chemung group, Lawrence-
ville, Tioga county. Pa.

Leptodesma Demus, n. sp.

PLATE XC, riGS, I.-,, n;.

Shell of medium size, rhomboidal ; body very oblique, narrowly ovate ;
extreme length more than one-third greater than the height ; ante-byssal
margin ol)li([ue, rounded below, concave at the sinus ; basal margin broadly
rounded ; posterior margin abruptly curved.

Left valve convex, gibbous above. Right valve of similar form, less
convex, and in the posterior part wider and more depressed.

Hinge-line straight, about two-thirds as long as the length of the valve.

Beaks situated at about the anterior third of the hinge, prominent,

204 PALjEONTOLUGY OF NEW YORK.

directed forward and rising; a little above the cardinal line. I'lnbonal
region gihbous, defined on the anterior liy the hyssal depression, ami on
the posterior ))y the slope of the side.

Anterior end large, limited hx an oljlinue In ssal depression, angnlar at the
extremity and ronnded below. Byssal sinus extending to a point more than
one-third the height of the valve l)elow the beak. Wing narrow-triangular,
not distinctly limited: niaruin ol)li(iue, slightly convex, recurving ju.st below
the hinge-line ; extremity angailar.

Test marked b\- fine, irregular stria?, somewhat fasciculate on the body,
and crowded and lamellose in front.

Interior unknown.

A well-preserved left valve has a length of 35 mm., height 20 mm., hinge-
line nearly 24 mm.

The body of the valve in this species is narrower and more elongate than in
L. Creon, and the wing smaller ami less distinctly defined. It resemldes
L. Lichas, but diflers in its more gibbous undjo, stronger byssal depression, less
obli(|ue margin of wing, with less acute termination and ])roportionally shorter
body.

Formation mid localitij. In sandstones of the Chemung group at Lawrence-
ville, Tioga county, Pa.

Leptoiiesma Loxias, n. sp.

I'l.ATK .\C. KU; U.

Sheij. of medium size, rhomboidal : Ijody ovate, narrow above, olili(iuc to the
hinge-line at an angle of about 40°; Iteight one-third less than the length;
ante-byssal margin oblique, rounding into the sinus; ventral margin broadly
rounded ; posterior margin abruptly recurved.

Left valve convex, gibbous in the middle and above. Right valve
unknown.

Hinge-line straight, greater than the height of the shell.

Beak obtuse, prominent, arching over the cardinal line, situated at the

LAMELLIBRANCHIATA. 205

anterior third of the hinge. Umbonal region narrow and gib))ous, subtend-
ing an acute angle.

Anterior end limited by a broad, nearly vertical byssal depression which
extends one-half the height of the valve ; margin convex ; extremity
acuminate. Wing triangular, not distinctly limited, joining the body near
the posterior extremity; margin oblique, nearly straight, concave just
beneath the hinge-line ; extremity mucronate.

Test thin, marked by fine concentric strife, which are regular over the
body and wing and strongly lamellose and fasciculate on the anterior end.

Interior unknown.

A small left valve has a greatest length of 28 mm., heiglit 17 mm., hinge-
line 21 mm.

This species is distinguished from L. Creoii and L. Demus by its narrower
anterior end and more rounded ventral marain.

Formation and locality. In the Chemung group, Lawrenceville, Tioga county,
Pa.

Leptodesma Mentor, n. sp.

I'l.AI'K XL. FKV .■); AMi PLATE XXIIl, FKi. Ifi ?

Shell of medium size, sub-rhomboidal ; body elongate-ovate, narrow at the
anterior end, obliipie, making an angle of about 40° with the hinge-line ;
length one-third greater than the height ; ante-byssal margin oblique, curving
into the gently depressed sinus ; basal margin hroadly curving into the
rounded posterior extremity.

Left valve moderately convex in the lower part, becoming convex in the
middle and gibbous above. Right valve unknown.

Hinge-line straight ; length about equal to the height of the valve.

Beak sub-anterior, directed forward, acute, but little elevated al)ove the
hinge-linCr Umbonal region abruptly, or sub-angularly gibbous, narrow,
subtending an acute angle.

Anterior end small, narrow, limited l)y an oblique byssal depression which
reaches about half way down the body of the shell ; extremity pointed.

206 PALEONTOLOGY OF NEW YORK.

Wing joining the })orly near the post-extremity of the shell, defined by a
shiillow groove; margin o()lifjnc. straiglit. apparently sliglitly concave just
below the cardinal line.

Test thin, leaving upon tlie cast the marl<s of the striae of growth whicli
have been somewhat fascicled upon the body, giving it an obscurely undulated
appearance.

Interior unknown.

A specimen of tliis species Ims a leugtli oi' •")■") nini.. liciglit 24 nnn.. and
hinge-line nearly 24 nun.

This species i-esembles L. Orodes, but dilTers in its greater obliquity ; the
bodv is more attenuate toward the anterior, and the wing is distinctly limited.

This one, and several other species, have shown tlu' presence of an alar
furrow and obscure fold, similar to Ptychopteria.

Formation and locality. In a coarse sandstone of the Upper Chemung group,
south of Smethport, McKean county, Pa.

Leptodesma Orodes.

l>r..\TE .K.\V, KIGS. B, 9, (10-); AND PLATE .XC, FIG. 8.

Leptodesma Orodes, Hall. Pal. N. Y., vol. v. pt. 1. Plate.s iind Explanations: PI. 25, tip?. G, 9 (lOt).

.Ian.. 1SS3.

Shell of medium size, su])-rhomboidal ; body ovate, oblique to the hinge-line
at an angle of about 55°; length one-fifth greater than the lieight; antc-
byssal margin a little oblique, nearly vertical above, curving into a long,
undefined sinus ; ventral margin rounded into the broad posterior curve.

Left valve moderately convex in the lower part, increasing in convexity
to the middle of the length, where it l)ecomes gibljous. Right valve
unknown.

Hinge-line straight, a little less tlian tlie height of tlie valve.

Beak sub-anterior, directed forward, moderately prominent, scarcely rising
above the cardinal line. Umbonal region abruptly gibljous, subtending an
angle of about 30°.

LAMELLIBRANCHIATA. 207

Anterior end short in the direction of the hinge-line, separated from the
body by a well-marked byssal depression extending for half the height of the
valve ; extremity abruptly angular. Wing large, joining the body below the
middle of its length, obscurely defined from the body of the valve ; margin
moderately oblique, nearly straight, or slightly convex below, with a very
gentle concavity just beneath the cardinal line.

Test thin ; casts of the interior obscurely marked by fine strise of growth
which are sometimes fasciculate upon the body of the shell.

Interior unknown.

An individual of medium size has a length of 32 mm., height 27 mm., and
hinge-line 23 mm. A smaller example has a length of 25 mm., height 20
mm., and hinge-line 18 mm.

This species is distinguished from L. Madurii by its shorter form, less
parallel sides of the body, larger wing, which is not extended on the cardinal
margin, and the body is not angular along its entire length.

The specimen, PI. xxv, fig. 10, has been flattened by pressure and is referred
with doubt to this species. It has the same general aspect, but is proportionally
wider below the middle, and more broadly rounded on the post-basal margin,
which peculiarities may have been produced by compression.

Formation and locality. In a coarse sandstone of the Upper Chemung group,
on the road from Olean, N. Y., to Smethport, Pa.

Section c, rostrata.
Leptodesma extenuatum.

PLATE XXII, FIG. 23 ; ANlJ PLATE XC, FIGS. 17, 18.

Leptodesma extenuatum, Halt,. Pal. N. Y., x-ol. v, pt. 1. Plates and Exiilanatioiis : PI. 22, fig-. 23.

Jan., 1883.

Shell of medium size, elongate, semi-ovate ; body narrowly ovate and oblique
to the hinge-line at an angle of about 30° ; length nearly twice the height ;
ante-byssal margin very oblique, scarcely depressed at the sinus, thence nearly
straight to the broadly curved jjase ; posterior margin abruptly recurved.

208 PALAEONTOLOGY OF NEW YORK.

Left valve moderately convex below, gibbous ou the umbo. Right valve
Hat below. (lcpres.sed-coii\ox in the middle, and more convex above, propor-
tionally wider than the left, and distinguished by its depressed-convex ibrm.

Hinge-line straiglit ; length greater than the length of the valve.

Beak of left valve sub-ant€rior, acute, directed forward, rising sliglitlv
above the hinge-line. Beak of riglit valve depressed, not rising above the
cardinal line. I'liiboiial region of left valve moderately gibbous, snlitending
ii very acute angle.

Antcriiir end greatly extended, a(!ute, rostrate, limited by a shallow b\ ssal
depression. Wing narrow-triangular, joining the body at tlic posterior
extremity, defined by the recurving of the stria>; margin abrupth- and
symmetrically concave; extremity produced beyond the posterioi- limit of
the shell.

Test thill, iiiarkcil by fine, sharp, closely arraiigi'c I, concentric stria-, which
are sometimes fasciculate upon the body and anterior side, and very distinct
npon the wing. Partial casts of tlic interior of the left valve give indications
of fine radii wliich appear to Ijelong to the intimate structure of the shell.

Characters of tlic interior unknown.

A left valve has a length of >5'2 mm., height K! mm., and hiii<:c-line
il mm. A right valve has a length of .■J4 nun., hciglit I'.i nun., and liinge-
line 4(1 mm.

This species is distinguished by tlie great lengtli of the liingr-line, its naiiow
outline, and anterior extension. It approaches Pteronites in character, but
differs in having a distinct wing, more depressed form, and a recurvation of
the strise along the po.st-uiiibnnal slope.

Formation and localities. In the Chenumg gron|). I'liilipsburg, Alleghany
county, N. Y., and Kelly's creek, Tioga county, Pa.

LAMELLIBRANCHIATA. 209

Leptodesma Hector, n. sp.

PLATE XC, FIGS. IH. 20,

Shell of medium size, sub-rhomboidal ; body narrowl}' elongate-ovate, oblique
at an angle of about 30° with the cardinal line ; length a little more than
once and a half the height ; ante-byssal margin oblique, carving into a broad,
shallow sinus ; ventral margin broadly curved ; posterior margin abruptly
recurved.

Left valve moderately convex below, narrowly gibbous above. Right
valve depressed below, gently convex above.

Hinge-line straight ; length equal to about four-fifths of the length of tlie
valve.

Beaks sub-anterior, directed forward, acute, slightly elevated al)ove the
hinge. Umbonal angle very acute.

Anterior end narrow, small, produced into an acute extension, defined by
a shallow byssal depression. Wing large, joining the body at three-fourths
or more of its length from the ))eak ; margin very oblique below, deeply
sinuate just- beneath the cardinal line, turning abruptly backward and
terminating in a spiniform extension. The wing of the right valve is
scarcely defined, and the shell has a somewhat broadly spatulate aspect.

Test thin, marked by line, close, concentric stria^, and, as usually seen,
the surface shows nearly equally distant lamellose stria? on the body and
wing, which are crowded on the anterior side and extension. In the right
valve these characters are more subdued on the body than on the wing. In
ordinary conditions, the specimens mostly exhibit only oljscure indications
of the striation of the shell.

Muscular impression in the right valve large, sub-circular, placed below
the middle of the length of the posterior slope.

A left valve, of the usual size, has a length of 35 mm., height 20 mm.,
hinge-line 27 mm. A small specimen has a length of 20 mm., height 12
mm., and hinge-line 1(1 mm. Young shells of this species are more gibbous
than the older examples.
27

210 PALEONTOLOGY OF NEW YORK.

This species resembles, in its general form, L. extenuatum, but the body is
narrower at the beak, the wing less extendeil, and the greatest concavity of the
margin is just below the cardinal line ; while in that species it is near the
middle : the anterior extremity is also less prolonged.

Formation and locality. In the upper shales of the Chemung group near
Canton. Bradford county, Pa.

Leptoi)esm.\ Clitus, n. sp.

I'LATF. X( . Via Jl.

Shell of medium size, narrowl}' sub-rhomboidal ; body elongate-ovate, ohli([UL'
to the hinge-line at an angle of about 30° ; length less than twice the height ;
ante-byssal margin very oblique ; ventral margin broadly rounded, somewhat
abruptly recurved at the post-basal extremity.

Left valve depressed-convex below, convex above, moderately gibbous on
the umbo. Right valve unknown.

Hinge-line straight, less than the greatest length of the shell.

Beak sub-anterior, directed forward, moderately prominent, rinbonal
region gibbous, subtending an acute angle.

Anterior end narrow, prolonged into a rostrate extension, ileliued by a
strong byssal depression. Wing narrow-triangular, joining the body near
the posterior end, defined only by the abrupt recurving of the stride ; margin
deeply and abruptly concave, the deepest concavity about the middle ; the
extremity is an acute extension of the cardinal line.

Test tliiii, marked by fine concentric stria;, \vhich are fasciculate iipdii tiic
l)ody, leaving the cast marked by gentle undulations, which are lamellose and
elevateil on the anterior side and rostral extension, and elevated on the wing.

Interior unknown.

A left valve has a length of M7 mm., hciglit ■_'<) nun., hinge-line '■'>'! mm.

This species diflers from L. extenuatum in its lnoader l)ody, shorter hinge-line,
and narrower wing; the strioB bend more altruptly forward along the pnst-
cardinal slope, and the wing margin is more deeply concave.

Formation and localities. In shales of the Chenunig grouji at Kelly's creek
and Mansfield, Tiosa countv. Pa.

LAMELLIBRANCHIATA. 211

Leptodesma truncatum, n. sp.

PLATE XC, FIGS. 24. 2.").

Shell above the medium size, sul)-rhomboidal ; body ovate-elongate, oblique to
the hinge-line at an angle of alxnit 35° ; length two-thirds greater than the
height ; ante-byssal margin oblique and often abruptly truncate, curving into
the sinus ; broadly rounded along the ventral margin, and more rapidly curv-
ing on the post-basal margin.

Left valve gently convex below, becoming more convex above, and some-
what gib1)0us on the umbo. Right valve less convex, Hat in the lower part.

Hinge-line straight, nearly as long as the length of the shell.

Beaks sub-anterior, directed forward ; in the left valve somewdiat promi-
nent ; in the right valve not elevated above the hinge-line. Umljonal angle
acute.

Anterior end obtuse, truncate, abruptly angular at the cardinal margin,
limited by a slightly oblique byssal depression. Wing large, triangular,
joining the body at the posterior extremity; margin sloping gently forward
for two-thirds of the width, then abruptly recurved and extended in an acute
or spiniform process. In the right valve the wing is less defined, and the
anterior end is more strongly truncate.

Test thin, marked by sharp, elevated, distant, concentric strias, with
intermediate finer lines of growth. The sti'onger striae are regular upon the
wing and posterior part of the shell, fasciculate on the anterior side, ami
stronger and lamellose on the anterior extremity.

Interior unknown.

A left valve has a length of 88 mm., height 22 mm., and hinge-line 37 mm.

This species may Ije known by its truncate anterior end. The forni of the
body is very similar to L. exienuatum , liut it is somewhat more convex and a
little wider ; the wing margin is less concave and the extremity less extended.
The right valves of these two species are conspicuously different.

Formation and locality. In the central portion of the Chemung group, Mans-
field, Tioga county, Pa.

2V2 PALEONTOLOGY OF NEW YORK.

Leptodesma Corydon, n. sp.

PLATE XC, FIG. 2i.

Shell above the medium size, sub-rhom]>oi(I;il ; body narrowing very rapidly
toward the beak, oblique to the liiii^e-liae at an angle of about 30°; length
less than twice the height; ante-byssal margin oblique, nearly straight,
slightly impressed at the sinus, broadly curved at the base and rounded on
the posterior extremity.

Left valve depressed-convex below and slightly gibbous on the umbo
(as preserved in thinh' laminated shale). Right valve unknown.

Hinge-line straight, about equal to the greatest length of the shell.

Beak sub-anterior, directed forward, little elevated above the cardinal line.
Umbonal region moderately gibbous, subtending an acute angle.

Anterior end narrow, rostrate, acute, extended, defined by a distinct,
shallow, byssal depression wliicli produces a long, gentle curvature in the
margin of tlie valve. Wing narrow, joining the body at nearly the posterior
e.vtremity ; margin abruptly recurved l)elow and somewhat deeply concave a
little below the cardinal line ; extremity forming a spiniform extension.

Test thin, marked by fine concentric stria>, which are fasciculate on the
])ody at unequal distances, and shai-ply elevated and more distinct on the
wing.

Interior unknown.

A left valve of medium size has a length of 42 mm., height 25 mm.,
hinge-line about 4(1 nun.

Compared with L. Clitus, the body of the shell is more elongate-ovate or
sub-spatulate, narrowing more rapidly toward the post-extremity ; the wing is
wider and the sinuosity less deep, its greatest depth being near the cardinal
line.

Formation and locality. In the Chemung group, Kelly's creek, Tioga county,
Pa.

LAMELLIBRANCHIATA. 213

Leptodesma Jason, n. sp.

PLATE XCI, FIGS. 4-6.

Shell above the medium size, sub-triangular; body elongate-ovate or sub-
spatulate, attenuate toward the anterior end, oblique at an angle of about
40° with the hinge-line ; length once and a half the height ; margin of the
anterior end gently curving into the undefined l)yssal sinus ; thence nearly
straight to within one-fourth the length of the valve from the posterior
extremity, which is regulaidy and broadly rounded.

Left valve regularly convex below, narrow and gibbous above. Right
valve depressed-convex below, more convex above, and modei'ately gibbous
in the umbonal region.

Hinge-line straight, somewhat less than the greatest length of the body.

Beaks sub-anterior, acute, directed forward, slightly elevated above the
hinge-line. Umbonal region abruptly giblwus, subtending a very acute angle.

Anterior end short. Wing joining the body near the posterior extremity ;
margin regularly concave, the greatest concavity near the middle of the
width, tei^minating in a short spiniform extension. In the right valve the
wing is proportionally larger and less defined.

Test thick, mai'ked upon the body and wing with sharp, elevated,
lamelliform strige and intermediate finer strige ; on the anterior the striae are
fasciculate.

Interior unknown.

A large left valve has a length of 40 nun., height 20 mm., hinge-line 32
mm. A right valve has a lengtli of 36 mm., height 20 mm., and hinge-line
34 mm.

This species resembles L. Hector in general form, but is broader at the
posterior end, more abruptly gibbous along the axis above the middle, the wing
joins the body nearer the posterior extremity, and the margin of the wing has
the deepest concavity in the centre of its width. The right valve is more
convex than the right valve of L. Hector, and the concentric elevated striag are

1^14 PALEONTOLOGY OF NEW YORK.

imicli stronj^xT. In all those clmriicters it also difTei-s more extremely from
L. extenualum.

Formation and locality. In conipaet sandstone oi' the Ujiper Chemung group,
alternating with some red beds, on Seely creek, Tioga county, Pa.

Liii'TuuES.M.v i'laui's, n. sp.

PLATE XC, FIli> SS, "1.

Shell larger than the medium size, sub-rhoniboidal : body ovate, oblique at an
angle of about 40° with the hinge-line ; height two-thirds the greatest length ;
ante-byssal and ventral margins very oblique and continuing in nearly a
straight line for two-thirds the length, with a slight concavity for the bvssal
sinus ; posterior margin very broadly curving.

Left valve depressed-convex below, gradually l)ecumiiig mure convex above
the middle, and somewhat gibbous on the umbo. Right valve unknown.

Hinge-line straight, nearl}" ec^ual to the greatest length of the shell.

Beak sub-anterior, inclined forward, obtuse, scarcely elevated above the
hinge-line. Umbonal angle acute.

Anterior end triangular, prolonged, acute. Wing joining the body of the
shell at the posterior extremity ; margin symmetrically concave ; extremity
j)roduced and acutely angular.

Test marked by distant, sub-etiual, laniellose elevateil stri*, with liner
intermediate striiB. The stronger striiie are regular on the wing and posterior
slope of the body, and become irregular and fasciculate on the anterior side
and lower half.

Interior unknown.

The hinge shows a narrow striated ligamental area, and, apparently, a
.slender lateral tooth.

A large left valve has a length of 44 mm., bciglit ■2S nun., .lud hinge-line
42 mm.

This form is more oblique, and the wing is longer ami u.nrower than in
L. Orodes.

LAMELLIBRANCHIATA. 215

Formation and locality. In the Upper Chemung group, Mansfield, Tioga
county. Pa.

Leptodesma Orcus, n. sp.

1>LATE XC. FIG^ -23

Shell of medium size, sub-riiomboidal ; body ovate, straight on the posterior
slope, oblique to the hinge-line at an angle of about 40° ; length about one-
third greater than the height ; ante-byssal margin oblique, slightl}- impressed
at the sinus, nearly straight along the base and regularly rounded posteriorly.

Left valve symmetrically and gently convex })elow, slightly gibbous
above. Right valve unknown.

Hinge-line straight ; length equal to three-fourths the length of the shell.

Beak anterior, acute, little elevated above the hinge-line. Umbonal region
narrowly gibbous, subtending a very acute angle.

Anterior end short, limited by an oblique bys.sal depression ; extremity
acute. Wing of medium size, joining the body about three-fourths its length
from the beak ; margin alnniptly curving forward from the base to near the
hinge-line, where it is sharply recurved into a short, angular extension of
the cardinal line.

Test thin, marked by fine concentric stria3, which are somewhat fascicu-
late on the body and anterior jiart of the shell, and a little more sharply
elevated on the wing.

Interior unknown.

The specimen illustrated has a length of 30 mm., height 22 mm., and
hinge-line 24 mm.

The form and pi'oportions of body are quite similar to L. Lysander, but it
is wider on the posterior, narrower on the anterior end, and more oblique to
the hinge ; the stria? less sharply elevated, curving more forward along the
posterior slope, and more abruptly recui'ved under the cardinal line.

Formation and locality. In the Chemung group at Kelly's creek, Tioga county.
Pa.

216 PALEONTOLOGY OF NEW YORK.

Lei'Todesma Lysander.

PLATE XXII, VIG.-2-2; and PLATE XC, FIG. .14.
L'pUxhuma Lysamhr, H.\i,i.. Pal. N. V.. vdl. \, jit. 1. Platc.^ a;iil Kxiil.-ination.s : PL 22. i\g. 22. Jan.. 1883.

Shell of medium size, sul>rhomboidal ; body ovate, abruptly narrowing
toward the front, ol)li(|Uc to tlie hinne-line at an angle of al)out 45°; length
one-third greater tliiin the height ; ante-bys.'^al margin oblique above, curv-
ing into the marked ;<inu.><, regularly rounded along the base and po.sterior
extremity.

Left valve depressed-convex below, more convex above, and moderately
gibbous on the uml)o. Right valve unknown.

Hinge-line straight, about equal to tlie greatest length of the valve.

Beak sub-anterior, moderately prominent. Umbonal region but slightly-
gibbous, subtending an acute angle.

Anterior end broad, obliquely truncate ; extremity slightly extended and
acute. "Wing narrow-triangular, joining the body at the posterior extremity ;
margin concave, greatest concavity just above the middle, thence turning
outward it is produced into a spiniform extension of the cardinal line.

Test marked by fine concentric strise, with sharp lamella? at nearly regular
intervals over the bod^ an<l wing, becoming crowded and fasciculate on the
anterior of the shell.

Interior unkiiow n.

A specimen has a length of ;>•") nnu., height '24 mm.. Miid hinge-line
33 mm.

This species differs from L. Corydon in its shorter ami liroa(KT form ; tlie
body is less oblique and more abruptly narrowed toward the anterior: the
striae are less abruptly recurved along the posterior slope.

Formation and localities. In shales of the Chennmg grou]i at Kelly's creek
and Mansfield, Tioga county, Pa.

LAMELLIBRANCHIATA. 217

Leptodesma nereus, n. sp.

PLATE XC, FIGS. 31-:53.

Shell of medium size, sub-rhomboidal ; body broadly ovate, narrowing rapidly
to the anterior end, and oblique to the hinge-line at an angle of 45° ; length
less than one-third greater than the height ; ante-byssal margin gently curved,
extending into a wide sinus, broadly rounded along the base, curving regularly
on the post-basal side and abruptly recurved in the upper part.

Left valve gently convex below, more convex above, and moderately
gibbous on the umbo. Right valve smaller, more depressed below, nearly
equally convex toward the umljo.

Hinge-line straight, less than the length of the valve.

Beaks sub-anterior, acute, directed forward, rising slightly above the
hinge-line. Umbonal region gibbous in the left valve, narrower but equallv
gibbous in the right valve. Umbonal angle acute.

Anterior end small, abruptly curving into the byssal depression ; extremity
acute, not prolonged. Wing broad, extending along the body about four-
fifths of its length from the beak ; margin very oblique in the lower part
and moderately concave above the centre, then turning abruptly backward
just below the cardinal line, and produced into a short spiniform extension.
In the right valve the wing is less defined and less concave on the margin.

Test thin, marked by concentric stride, which are fasciculate on the body
and anterior part, and more elevated, distant and sharp upon the wing.

Muscular impression large, sub-circular, situated on the posterior slope
below the middle of the length. The pallial line extends from the lower
part of the muscular impression nearly parallel to the anterior and basal
margin. The hinge of the left valve has a strong groove extending its entire
length ; the right valve has an oblique posterior fold.

One specimen has a length of 35 mm., height 26 mm., hinge-line .31 mm.
A similar example has a lengtli of 34 mm., height 24 mm., and hinge-line
28 mm. A right valve has a greatest length of 31 nnn., height 20 mm., and
hinge-line 25 mm.
28

218 PALEONTOLOGY OF NEW YORK.

This species resembles L. Orcus, but the wing is wider, less deeply aud
iil)niptly sinuous, and the striae turn more aljruptly forward at the junction
ol' the bod}' ami winy. The body is narrower and more oblique than in
L. Lysander, and the anterior end less prolonged.

Formation and locality. In the shales of the Upper Chemung- group near
Canton. Bradford county, Pa.

Leptodesma alatum, n. sp.

Shell of medium size, sul)-rlionil)()iilal : hdily ovate, rapidly narrowing toward
the beak, oblique, making an angle of about 50° with the hinge-line ; length
one-third gi-eater than the height ; ante-byssal margin oblique and <ur\ing into
the distinct sinus ; ventral margin gently cm'ved, joining the broad, rounded,
posterior extremity.

Left valve gently convex below, becoming more couA-ex and slightly
gibbous above tlic middle. Right valve depressed in the lower portion,
in the middle and abcne about equally convex with the left.

Hinge-line straight, a little less than the length of the valve, and greater
than the height.

Beaks sub-anterior, directed forward, acute, l>ut little elevated al)0\e the
hinge-line in the left valve. Umbonal region narrow, and abruptly gibbous.
In the right \ alve the beak is depressed, aud the umbonal region a little
less gibbous than in the other valve.

Anterior end small, acute at the extremity, rounded below to the distinct
byssal sinus. Wing large, wide-triangular, joining the body at the posterior
extremity ; margin moderateh' concave, the greatest concavity being above
the middle, from which point it turns abruptly outward and the extremity
is produced into a spiniform extension. In the right valve the wing is less
distinctly limited from the body than in the left.

Test thin, marked b}^ sharp, elevated, concentric striae with finer inter-
mediate lines of growth. The stronger striae are somewhat regular upon the
body and wing, while on the anterior side they are crowded and fasciculate.

LAMELLIBRANCHIATA. 219

Muscular impression large, sub-circular, situated below the middle of the
posterior slope. The pallial line extends from the lower part of the muscu-
lar impression, parallel to the basal and anterior margins, into the cavity of
the beak. Ligamental area wide.

A left valve of this species has a length of 35 mm., height 26 mm., and
hinge-line 33 mm. A somewhat larger right valve has a length of 38 mm.,
height 28 mm., and hinge-line 33 mm.

Formation and locality. In the shales of the Chemung group at Canton, Brad-
ford county, Pa.

Leptodesma Oeus, n. sp.

PLATE XC, FIG :iO.

Shell above the medium size, sub-rhomboidal ; body broadly ovate, abruptly
contracted towards the anterior end, oblique at an angle of about 50° with
the hinge-line ; ante-byssal margin oblique, curving into the marked sinus,
thence gently curving to the posterior extremity, which is broadly rounded.

Left valve depressed-convex below, moderately convex above. Rio-ht
valve unknown.

Hinge-line straight; length about five-sixths the greatest length of the
valve.

Beak sub-anterior, directed forward, slightly rising above the cardinal line.
Umbonal region moderately gibbous, subtending an acute angle.

Anterior end triangular, abruptly acute at the extremity, defined bv a
marked byssal depression. Wing large, triangular, without distinct limita-
tion, joining the body near the posterior extremity ; margin oblique below,
concave above the middle, turning abruptly outward and terminating in a
sharply angular extension of the cardinal line.

Test thin, marked by sharp, elevated, concentric striag with finer inter-
mediate ones. The stronger striaj are regular on the wing and posterior
side ; irregular and fasciculate on the anterior.

Interior unknown.

220 PALEONTOLOGY OF NEW YORK.

Two left valves have respectively these dimensions: length 48, and 42 mm.,
heiffht 32, and 30 mm., hintie-line 40, and 35 mm.

This species resembles L. Pelops, but the body is broader and less oblique,
iIr' anterior portion not so attenuate, the wing somewhat wider, the greatest
sinuosity in the margin of the win<: being nearer to the cardinal line, and the
extremity of tlic wing more acuminate.

Formation and locality. In shales of the Chemung group, Mansfield, Tioga
county. N. Y.

Leptodes.ma aliforme,

I'l.ATK .\XII, KIU is; AMI I'LATK XCI, FIG. 2.
Liplnr!,.\mn aliforme, IlAr.i.. Pal. N. Y., vol. v. pt. 1. Plate.'; and Explanations: PI. 22. tig. 28. Jan., 1SS3.

SiiEM, large (right valve), elongate, triangular : body narrow, spatulate, oblique
at an angle of about 30° witli tlie cardinal line; length twice the height;
margin of shell oblique anteriorly, continued along the base in nearly a
straight line for two-thirds its length, thence curving to the po.'^terior
extremity, whicli is abruptly rounded.

Right valve nearly flat below, depressed-convex in tbe middle, .-^lightly
gitjbous in the unilionul region. Left val\e luiknown.

Hinge-line straight ; length equal to the greatest length of tlie >liell.

Beak sub-anterior, depressed, directed forward.

Anterior cml narrow-triangular; extremity attenuate, very acute. Wing
narrow, elongate, triangular, extending to tlie posterior extremity of the
valve, not defined; margin concave, the greatest concavity below the middle;
extremity slightly produced, angular.

Test not preserved. The specimen is a cast of the interior, showing some
faint indications of concentric strias.

Muscular impression large, situated at about the middle of the k-ngtli of
the posterior slope. Pallial line continued parallel to the anterior side, with
slight interruptions, nearly to the lieak. The hinge is furnished with a slen-
der, oblique lateral tooth.

LAMELLIBRANCHIATA. 221

The specimen described is 60 min. in length, with a height of 29 mm.,
and hinge-line 61 mm.

This snecies bears considerable resemblance to L. extmuatum in the characters

J.

of the right valve ; bnt it i-s proportionally narrower, the posterior exti'emity
more abruptly recurved and the hinge-line less extended behind. A single
right valve is the only specimen at present known. It differs sufficiently from
the other forms here described to be easily recognized.

Formation and locality. In a white sandstone of the middle portion of the
Chemung group near Angelica, Alleghany county, N. Y.

Leptodesma rude.

PLATE XXV, FIG. \i ; and PLATE XCI, FIG. 3.
Leptodesma rude, Hxhh. Pal. N. Y., vol. v, jit. 1. Plates and Explanations: PI. 25, fig. 12. Jan., 1883.

Shell large, sub-rhomboidal ; body broadly ovate below, rapidly attenuating
above, oblique to the hinge-line at an angle of about 50° ; length less than
one-third greater than the height ; ante-byssal margin curving into the broad
sinus ; ventral and posterior margins broadly rounded.

Left valve convex below, becoming narrow and gibbous above the middle.
Right valve less convex.

Hinge-line straight, less than the length of the valve.

Beak sub-anterior, directed forward, acute, little elevated above the
cardinal line. Umbonal region narrow and gibbous, subtending an acute
angle.

Anterior end large, limited by a vertical byssal depression ; extremity
acute. Wing of moderate size, joining the body at the posterior extremity ;
margin concave ; termination acute.

Test thick, marked by concentric strise, which have been fasciculate,
leaving strong undulations upon the cast of the interior. These surface
characters are subdued in the right valve.

Interior unknown.

222 PALAEONTOLOGY OF NEW YORK.

A left valve has a length nl" "il iiiiii., heiglit 37 iiiiii., Iiinw-line about
42 mill.

Specimens of this species usually present a vei'j rough and irreuulai- aspect
Ironi the character of the shell, with its strongly lamellose structure and tlic
coarse matrix in which it is usually Ibmid. The specimen figured is a cast of
the interior, and is distinguished by the broad posterior end and aluupt narrowing
toward the front, the obtusely sub-angular lunbo, and the large anterior end.
In a crushed .specimen retaining both valves, the right valve is almost equally
convex with the left; the surface is less lamellose and presents only gentle
undulations.

Formation and locality. In a coarse sandstone of the uj)per part of the
Chemung group, on tlic road from Olean, X. Y., to Sniethport, Pa.

Leptodesma Biton, n. sp.

I'l.AlE X(J1. vm i.

Shell large, sub-rhomboidal ; body elongate-ovate, making an angle of about
45° with the hinge-line ; height nearly two-thirds of the length ; ante-byssal
margin oblique, slightly curving into a long, shallow sinus, which impresses
the margin for more than half the length of the valve; basal and posterior
margins broadly rounded.

Left valve regularly and gently convex in the lower part, becoming more
convex and gibbous above the middle. Kight valve uidxnowii.

Hinge-line straight, greater than the heiglit of \\\v \al\c.

Beak sub-anterior, directed forward, but little elevated above the liinge-
line. Umbonal region al)ruptly gibljous, subtending an acute angle.

Anterior end produced, narrow, acute at the extremity, limite<l by an
oblique, shallow byssal depression. Wing large, joining the bod}- at the
posterior end, not distinctly separated : margin slightl}- ol)lique below, gently
concave above the middle, and curving slightly outward just below the car-
dinal line.

Test thill ; cast marked by fine concentric striae of growth, which, at

LAMELLIBRANCHIATA. 223

intervals, have been elevated into fascicles, and on the external shell, were
probably sharp lamellose striae.

Interior nnknown.

The specimen described has a length of -30 nun., height -W mm., and
hinge-line 35 mm.

This species resembles L. Orodes, and may be distinguished by the more
extended and acute anterior extremity, and the larger wing which is distinctly
concave on the margin and recurved just below the cardinal line. It differs
from L. Macluril in its more produced anterior extremity, and broader wing
which is less abruptly recurved at the extremity.

Formation and locality. In a coarse sandstone of the Upper Chemung group,
south of Sniethport, McKean county, Pa.

Leptodesma Lesleyi, n. sp.

PLATE XCI. FIG. 7.

Shell large, sub-rhomboidal ; body narrow, elongate-ovate, making an angle of
30° with the cardinal line ; length more than one-third greater than the
height ; ante-byssal margin oblique, nearly straight above, curving into the
broad sinus ; ventral margin broadly curved ; posterior extremity abruptly
rounded.

Left valve convex below, narrowly gibbous in the middle and on the
umbo. Right valve less convex, depressed below.

Hinge-line straight, nearly equal to the greatest length of the shell.

Beaks sub-anterior, directed forward,, acute and arching over the hinge in
the left valve, depressed in the right valve. Umbonal region of the left
valve narrowly gibbous, and subtending a veiy acute angle.

Anterior end large, limited by a broad, distinct, oljlique byssal depression ;
extremity flattened and acuminate. Wing large, triangular, joining the
l)ody near the post-basal extremity, limited by the abrupt forward bending of
the stride ; margin deeply concave ; extremity produced and acute. The

224 PALEONTOLOGY OF NEW YORK.

wing of the right valve is scarcely defined from the body and less deeply
concave on the margin.

Test marked by fine, irregular, concentric striae which are strongly fixscicu-
late and lamellose on the ventral side and anterior end, and are shown on
tlie wing as sharp, elevated, regular striae. Some specimens preserve line
resrular striae on the lioilv of tlie valve, ])ut tlic\' are usuallv somcwliiit irreg-
ular and lamellose. In ;iii cxIoIiattMl and macerated conditi(Jii tlicy sliow
fine radiating lines which probably l)elong to the intimate structure of the
sliell.

Ligamental area (as preserved in an imperfect right valve) l.o mm. wide,
and marked by very fine, minutely undulating longitudinal striie. The
hinge also shows an obscure oblique lateral tooth.

A left valve, of medium size, has a greatest length of 56 mm., height
31 mm., and hinge-line about 51 mm.

This species somewhat resembles L. avifnrme, but is distinguislied by its more
oblique form, and wider anterior end. Specimens are quite abundant in an
argillo-calcareous sandstone of the Upper Chemung group, associateij witli
Spirifera Verneuili.

Formation and locality. In the Upper Chemung group, Auljurn township,
Susquehanna county. Pa.

Leptodesma avifokme, n. sp.

I'l.ATI-; XCI, KIG. 8.

Shell large, sub-rhomboidal ; body elongate-ovate, broad Ijehiud, and rapidly
narrowing towanl the beak, oblique at an angle of a little less than 45° to
the hinge-line ; height more than one-half the length ; ante-byssal margin
very oblique, continued in a straight line into the shallow sinus, thence
curving to the posterior extremity, which is broadly rounded.

Left valve gentlj- convex below, very convex above, and moderately
gibbous on the umbo. Right valve unknown.

LAMELLIBRANCHIATA. 225

Hinge-line straight ; length a little more than the greatest length of the
valve.

Beak sub-anterior, directed forward, acute, not rising much above the
hinge. Umboual angle acute.

Anterior end narrow, elongate, very acute, limited by a shallow" byssal
depression. Wing large, joining the body near the base ; margin broadly and
symmetrically concave ; extremity produced into a spiniform extension reach-
ing beyond the posterior extent of the shell.

Test marked by fine concentric striae which are regular on the posterior
part of the body and the wing, and very crowded and fasciculate on the
anterior.

Interior unknown.

A large left valve has a length of 60 mm., height 37 mm., hinge-line
62 mm. A slightly larger, imperfect specimen has been found, the body of
which, near the posterior extremity, has a greatest width of from 25 to 28
mm., and measures from 12 to 14 mm. in the narx'ow part between the beak
and the byssal sinus.

This species differs from L. Pelops in the longer and more ei'ect body, more
attenuate anterior extremity, more extended wing and deeper sinus in the
margin.

Formation and localities. In the middle beds of the Chemung group at
Charleston, and near Mansfield, Tioga county. Pa.

Section d, patulata.
Leptodesma flaccidum, n. sp.

PLATE XCI, FIG. 9.

Shell of medium size, rhomboid-ovate, spatulate below ; body oblique at an
angle of about 45° to the hinge-line ; length about one-third greater than
the height ; ante-byssal margin subtruncate, oblique, a little concave below,
curving into the broad ventral margin ; posterior margin abruptly rounded

and recurved.

29

226 PALEONTOLOGY OF NEW YORK.

Loft valve moderately convex in the middle, ffibbous on the umbo,
depres.sed-convex in the lower part. Right valve unknown.

Hinge-line straight; length about equal to the height of the shell.

Beak obtuse, directed forward, moderately prominent, situated anterior to
tlie middle of the cardinal line. Umbonal region gibbous, subtending an
acute angle.

Anterior end comparatively large, produced into a nasute extension.
Wing small, niirrow-triangular, joining the body of the shell more than one-
third the height above the base ; margin gently concave; extremity acute.

Test thin, marked by fine regular striae of growth, which are fasciculate
on the mnbo and lamellose at nearly equal intervals on the lower part of
the shell.

Interior unknown. The hinge is marked by a single slender groove.

A left valve has a length of 40 mm., height 27 mm., hinge-line about
27 mm.

This species resembles L. complanatum, but differs in its greater proportional
length and the body is more depressed and extended below. It is characterized
by the spatulate posterior extension, which is more extreme than in any other
species here described.

Formation and locality, hi the Chemiuig group, Lawrenccville, Tioga county,
Pa.

Leptodesma patulum, n. sp.

Pr.ATK XCI, Kl(;<. 10, 11

Shell above the medium size, sub-rlioiiiboidal : liodj' oblique, elongate, sub-
ovate ; length slightly more than one-third greater than the height;
ante-byssal margin oblique, gradually curving to the ventral margin which
is nearly straight ; posterior margin broadly curved.

Valves moderately convex below, scarcelj^ gibbous above, similar in form ;
the right valve being a little smaller and less convex than the left.

Hinge-line straight, somewh.at longer than the height of the shell.

Be.aks at about the anterior third of the hinge-line, directed forward,

LAMELLIBRANCHIATA. 227

somewhat prominent. Umbonal region moderately gibbous, not strongly
defined. Umbonal angle acute.

Anterior end large, produced into a nasute extension. Wing large,
joining the shell at the posterior extremity ; margin scarcely concave,
abruptly produced along the hinge-line.

Test marked by fine lines of growth which are irregularly fasciculate,
sometimes appearing as equidistant, sharply elevated lamellae ; crowded on
the anterior ; more regular over the wing and abruptly recurving just
beneath the hinge.

The hinge is marked by one or two narrow, parallel, longitudinal grooves.

A specimen of medium size has a length of 40 mm., height 26 mm., and
hinge-line 28 mm. A similar right valve has a length of 36 mm., height
24 mm., and hinge-line 27 mm.

This species differs from L. flaccidum in its much larger wing, which is more
extended along the body of the shell. It is less convex and the umljo less
gibbous than in any of the preceding species.

Formation and locality. In the upper part of the Chemung group at Mans-
field, Tioga county. Pa.

Leptodesma complanatum.

PLATE XXII, FIG. 2.

Leptodtsiiia complanatuni. Hall. Pal. N. V., vol. v, pt. 1. PLates ami Exiilan.ations : PI. 22, tig-. 2.

Jan., 1SS3.

Shell of medium size, obliquely semi-elliptical ; body sub-ovate, moderately
oblique ; length one-third greater than the height ; ante-byssal margin sub-
truncate, gradually curving into the broad ventral margin ; posterior margin
abruptly rounded.

Left valve depressed-convex, a little gibbous on the umbo. Right valve
unknown.

Hinge-line straight ; length less than the lieight of the shell.

Beak acute, incurved, directed forward, moderately prominent. Umbonal

228 PALEONTOLOGY OF NEW YORK.

region indistinctly defined anteriorly ; the posterior side limited by the post-
umbonal depression.

Anterior end short ; extremity angular. Wing undefined, joining the
body one-third of the length from the posterior extremity ; margin gently
concave ; extremity scarcely produced.

Test marked by fine, sharply elevated, concentric striaj, which are more
crowded anteriorly, and very regular on the wing.

Interior unknown.

The specimen described, which is a separate left valve, has a length of
28 nun., height 20 mm., and hinge-line IS mm.

Formation and locality. In the shales of iUl' Chemung group at Philips-
burg, N. Y.

Section e, arcoidea.
Leptodesma Maclvhii.

PLATE XXV, KIGS. 8, M ; am> PLATE XCI, FIGS. 13, 14.

Leptoiciiiia Madurii, Ham,. P;il. N. Y., voL v, pt. 1. Plate.s Jind Kxplanation-s : PI. 25, fig^. 8, 13.

Jan., 1883.

Shell large, i-huiiil)i)iil;il ; liody elongate, suh-elliptical, ol)li4ue, making an angle
of about 45° with the hinge-line ; length more tliaii one-thii'd greater than
the height ; aute-byssal margin oblique, genth' curving into a long, shallow,
undefined sinus ; ventral margin nearly straight, curving abruptly into tlic
posterior margin, wliidi is ronnilcil and ain uptly recurved.

Left valve moderately convex in the lower part, becoming gibbous and
sub-angular along the line of the axis to the l)eak. Right valve distinctly
arcuate, less convex, narrowly gibbous in the umbonal region.

Hinge-line straight; length about (Hjnal to the height of the valve.

Beaks sub-anterior, directed forward, Imt little elevated above the hinge-
line in the left valve, depressed in the right. Umbonal angle acute.

Anterior end narrow-triangular, limited by an oblique depression which
extends nearly one-third of the length of the valve to the byssal sinus.

LAMELLIBRANCHIATA. 229

Wing large, undefined ; margin very oblique in the lower part, .slightly
concave above, the greatest concavity being a little below the hinge-margin ;
extremity produced into an angular extension. The right valve shows less
distinction between the body of the valve and the wing.

Test thin, marked by distant lamellose lines of growth witli intermediate
finer strise. These lines are more regular upon the wing and very much
crowded and fasciculate upon the anterior side of the body.

Interior unknown.

Hinge, posterior to the beak, furnished with a slender lateral tooth

A left valve of this species has a length of 55 mm., height 35 mm., hinge-
line 37 mm., and the body, at the posterior end, having a width of 25 mm.
A right valve has a length of 45 mm., height 30 mm., and hinge-line about
28 mm.

The specimens of this species observed are casts of the interior in coarse
sandstone, or impressions of the exterior in the same rock. The species is
distinguished by its straight ventral side and the nearly parallel direction of
the sides of the body in the left valve.

Formation ajid localities. In a coarse sandstone of the Upper Chemung group,
on the road from Olean, N. Y., to Smethport, Pa., and at Bradford, Pa.

Leptodesjia arciforme, n. sp.

PLATE XCI, FIG. 12.

Shell large, narrow, sub-rhomboidal ; body sub-cylindrical, oblique at an angle
of about 30° to the hinge-line ; length nearly one-half greater than the
height ; anterior margin oblique, merging into the broad, low curvature of
the ventral margin ; posterior margin abruptly rounded and curving into the
undefined wing.

Valves very convex, strongly gibbous, obtusely sub-angular along the
middle ; the greatest convexity distant from the beak one-third the height
of the valve. The right valve is less gibbous, but otherwise similar to the
left.

230 PALAEONTOLOGY OF NEW YORK.

Hinge-line straijrht ; length about equal to the height of the shell.

Beaks prominent, directed forward and arching over the hinge, situated
at about the anterior third of the cardinal line. Uinl)onal region angularly
gibbous al)Ove, alnniptly defined along the posterior slojje. Umbonal angle
acute.

Anterior end short, angular. Wing an uudeliued, narrow-triangular
expansion; margin straight or a little concave; extremity very slightly
produced.

Test moderately thick, marked l)y fine concentric striae, which are
fasciculate on the body of the shell, and crowded ami laraellose over the
anterior side.

Interior unknown.

A large left valve has a length of 00 mm., height 36 mm., and hinge-
line 37 nun.

This species is distinguished from L. Lichas by its larger and stronger form,
being very gibbous along the entire length of the shell, and with a propor-
tionally smaller wing.

Formation and locality. In the upper part of the Chemung group at Mansfield,
Tioga county. Pa.

Leptodesma Phaon, n. sp.

PLATE XCI, FIG. 18.

Shell above the medium size, narrow-rhomboidal ; body sub-cylindrical, very
oblique, making an angle with the hinge-line of less than 30° ; length nearly
twice the height ; ante-byssal margin short, oblique, curving into the broad,
almost straight ventral side ; posterior margin abruptly but regularly rounded
and continuous with the base of the wing.

Left valve very convex, gibbous above. Right valve unknown.

Hinge-line straight, somewhat longer than the height of the .shell.

Beak at the anterior third of the hinge-line, obtu.^e, moderately elevated,
directed forward. Umbonal region gibbous, not well-defined anteriorly,
abruptly depressed on the posterior. Umbonal angle acute.

LAMELLIBRANCHIATA. 231

Anterior end short, acute at tlie extremity, defined hy a slight bend in the
striae indicating tlie byssal sinus. Wing small, narrow-triangular, joining
the body near the posterior end ; margin straight, very oblique ; extremity
angular.

Test marked by strong concentric striai, which at equal intervals are raised
into sharp lamellse, and are more crowded in front.

Interior unknown.

A left valve has a length of 47 mm., height 25 mm., and hinge-line 27 mm.

This species is remarkable for its extreme obliquity of body. In its general
features it somewhat resembles L. arcifonne, but differs in the less angular
gibbosity of the body, larger wing, more extended anterior end, and in the
surface markings.

Formation and localiUj. In the upper part of the Chemung group at Mansfield,
Tioga county, Pa.

Leptodesma propinquum, n. sp.

PLATE XCI, FIGS. 16, 17.

Shell of medium size, rhomboidal ; body narrow, sub-cylindrical, very oblique,
making an angle of about 30° with the hinge-line ; length more than twice
the height ; anterior margin oblique ; ventral margin nearly straight on the
anterior half, and broadly curving over the lower half; posterior margin
abruptly curved.

Valves gibbous, nearly equal in size and convexity.

Hinge-line straight, longer than the height of the valve.

Beaks at about the anterior third of the hinge-line, directed forward, very
prominent, arching over the cardinal line. Umbonal region gibbous, limited
posteriorly by the vertical descent of that side, scarcely defined on the
anterior. The umbo and post-cardinal slope are obtusely sub-angular for
about two-thirds of the length of the body. Umbonal angle acute.

Anterior end not defined (the byssal depression being obsolete) ; extremity
acute. Wing small, narrow-triangular, joining the body near the posterior

2:^2 PALEONTOLOGY OF NEW YORK.

extremity, undefined: niar<:in straight or slightly concave, very oblique;
extremity slightly produced, angular.

Test marked by regular, even, concentric striie, which, when well preserved,
are elevated and lamellose, and are crowded and fasciculate on the anterior
end of the shell.

Interior unknown.

A nearly entire left \:\\\(' has a greatest length of 45 mm., height 20 mm.,
ami hinge-line 26 iniii. A similar I'ight valve has a length of 37 mm.,
height 18 mm., and hinge-line 22 mm.

This species is very similar to L. Lichas, but dill'ers in the greater convexity
of body, undefined Ijyssal depression, and narrower wing.

Formation and locality. In the middle portion of the Chemung group at Mans-
field, Tioga comity, Pa.

Leptodesma Lichas.

PLATli XXI, FIGS. 35-39; AXn PLATE XCI, FItiS I'J, 20.

LrptodesiiM Lichas, Hai.l. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 21, fig-.*. 3.5-39.

.Jan., 1883.

Shell of medium size, sub-rhomboidal ; body sub-cylindrical, very oblique ;
length nearly twice the height ; ante-byssal margin subtruncate, extending
below to the broad, gently curving base ; posterior margin abruptl}- recurved.

Valves very convex above, gently convex toward the posterior extremity-,
making the body somewhat cylindrical. Right \al\c probably a little
shorter tlian the left, as inferred from the separated valves.

Hinge-line straight, less than the length of the shell.

Beaks acute, situated at the anterior third of the hinge-line, directed for-
ward, prominent, arching over the cardinal line. Umbo abruptly gibbous,
subtending an acute angle.

Anterior end large, acute and nasute at the extremity. The bys.sal sinus
makes only a slight depression in the margin. Wing narrow-triangular, join-
ing the body near the posterior extremity, not distinctly limited ; margin

LAMELLIBRANCHIATA. 233

straight and oblique below, recurving just beneath the hinge-line, and form-
ing a short mucronate extension.

Test thin, marked by fine concentric strias which are irregularly crowded
into fascicles, producing an undulated aspect to the surface. The strise are
sub-lamellose on the anterior side, and sometimes fasciculate on the wing.
The fascicles on the body are often marked on their summits by sharp,
regular lamellae. The structure as seen in exfoliated specimens is radiated ;
but this does not appear to be an exterior character.

The hinge is marked by a single aiarrow groove ; beyond this the charac-
ters of the interior are unknown.

A large left valve has a length of 45 mm., height 25 mm., hinge-line
27 mm. A smaller specimen has a length of 28 mm., height 16 mm.,
hinge-line 17 mm. A right valve has a length of 20 mm., height 15 mm.,
and hinge-line 15 mm.

Formation and localities. In the Chemung group at Philipsburg, Alleghany
county, N. Y., and in Sullivan township, Tioga county, Pa.

Leptodesma quadratum, n. sp.

PLATE XCI, FIG. 15.

Shell of medium size, rhomboidal or sub-quadrate ; body ovate, making an
angle of nearly 40" with the cardinal line ; length one-third greater than the
height ; ante-byssal margin nearly vertical in front, rounding below into the
shallow sinus, and extending nearly the whole height of the valve ; ventral
margin nearly straight ; post-basal margin abruptly rounded and joining the
wing without limitation.

Left valve convex, gibbous on the umbo, and obscurely angular along the
posterior slope. Right valve equally conve:^.

Hinge-line straight, equal to three-fourths the length of the valve, and
equal to the height.

Beaks situated at the anterior third of the hinge, prominent and arching
over the cardinal line. Umbonal region gibbous, subtending an acute angle.
30

234 PALEONTOLOGY OF NEW YORK.

Anterior end convex, limited by a shallow, oblique, byssal depression which
is nearly as long as the height of the valve ; length one-half the height ;
extremity slightly produced. Wing triangular, scarcely defined, joining the
body at the posterior extremity ; margin oblique, straight or slightly convex ;
extremity obtuse-angular. An imperfect right valve presents about the same
characters of wing.

Test marked In flue striae of growth which are strongly fasciculate on the
anterior end.

Interior unknown.

A left valve has a greatest length of 31 mm., height 20 mm., and hinge-
line 21 mm.

This species is distinguished by its short, broad, sub-quadrate form. It has
very much the aspect of Modiomorpha, but clearly belongs with L. Phaon and
L. Lichas, which are among the extreme variations of the species of Lepto-

DESMA.

Formation and locality. In the Upper Chemung group, Lindley township,
Steuben county, N. Y.

Section /, mytiloidea.
Leptodesma acutirostrum, n. sp.

PLATE XCI, FIG. 21.

Shell of mfdium size, rhomboid-ovate; body narrowly ovate and rapidly
attenuate toward the beak, oblique, making an angle of a little less than
45° with the hinge-line ; length nearly one-third greater than the height ;
ante-byssal margin oblique, sloping into the shallow sinus ; broadly rounded
below, the curvature continued into the posterior extremity.

Left valve depressed-convex in the lower part, moderately convex in the
middle, and slightly gibbous above. Right valve unknown.

Hinge-line straight, less than the height of the valve.

Beak anterior, acute, directed ibrward, scarcely rising above the hinge-

LAMELLIBRANCHIATA. 235

line. Umbonal region narrow and moderately gibbous, subtending a very
acute angle.

The byssal depression reaches the mai'gin just below the beak, leaving a
very small, acute, anterior extremity. Wing large, undefined, joining the body
at the posterior end ; margin oblique, essentially straight, not recurved at the
cardinal extremity.

Test thin, leaving upon the cast the marks of the stride of growth which
are more or less fasciculate upon the body, and crowded and lamellose in
front.

Hinge furnished with a distinct posterior tooth. Interior unknown.

The specimen described has a length of 32 mm., height 24 mm., and
hinge-line 22 mm.

This species somewhat resembles L. Orodes, especially as shown in PI. xxv,
fig. 10, but the beak is more nearly anterior, the anterior end much smaller
and more acute, the byssal sinus not extending so low on the body of the
valve, and the body of the shell more distinctly attenuate toward the beak.
It is especially distinguished by its narrow slender beak and small anterior
end.

Formation and locality. In a sandstone of the Upper Chemung group at
Warren, Pa.

Leptodesma mytiliforme.

PLATE xxv, FIGS. 7, 11 ; AND PLATE X(JI, FIGS. -22-35.

Leptodesma mytUiformf, Hall. Pal. N. Y., vol. \', pt. 1. Plates and E.\planations : PI. 25, fig-s. 7, 11.

Jan., 1883.

Shell of medium size, elongate-ovate ; body narrowly elliptical, becoming
attenuate in front, oblique, making an angle of nearly 45° with the hinge-
line ; length more than one-third greater than the height ; ante-byssal margin
oblique, gently curving into a scarcely perceptible sinus, giving a straight or
slightly concave margin extending for two-thirds the length of the valve ;
posterior margin abruptly rounded.

236 PALJEONTOLOGY OF NEW YORK.

Left valve regularly convex in the lower half, becoming contracted, gib-
bous and sub-angular al)ove the middle. The right valve is smaller, the
liinge-line proportionally longer, the base of the valve and the wing much
more depressed, and the umbonal region narrow and more angular.

Hinge-line straight, about equal to the height of the valve.

Beaks sub-anterior, directed luiwanl, acute, scarcely raised above the
hinge-liiu'. Umbonal region iianow and gibbous, subtending a very acute

angle.

Anterior end short, aljniptly attenuate, acute, limited by a shallow byssal
depression which extends for hidf the length of the valve. Wing large, not
strongly limited, extending nearly to the posterior extremity of the body ;
margin very oblique, not concave, nor recurved below the cardinal line ;
extremity obtuse-angular.

Test thin, marked by concentric stria3 which have left, their impression
upon the cast of the interior, showing them to have been regular upon the
body and wing, and crowded into fascicles upon the anterior side.

Ligamental ai-ea narrow and finely striated. Interior unknown.

The largest specimen of the left valve observed has a length of 48 mm.,
height 25 mm., and hinge-line 22 mm. A smaller example has a length of
33 mm., height 22 mm., and hinge-line 20 mm. A large right valve has a
length of 40 mm., height 25 mm., and hinge-line 27 nun.

This species differs from L. Mentor in its proportionally longer, narrower and
sul)-angular l)ody, the smalliT, less defined wing, the less distinct byssal sinus, and
the smaller anterior i'w\. The wing is often imperfect, giving the shell nuicti
the aspect of Mytilus or Mnmoi.A. Tlie axis of the shell in the left valve is
apparently slightly curved, giving it a characteristic expression.

Formation and locality. In a coarse sandstone of the Upper Chemung group,
nil tlie road from Olean, N. Y., to Smethport, Pa.

LAMELLIBRANCHIATA. 237

PTERONITES, McCoy.
Pteronites profundus.

PLATE XXII, FIGS. 25, 26, 27.

Pteronites ■prafimdm. Hai.l. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 22, figs. 25-27.

Jan., 1883.

Shell large, lougitudinally semi-ovate ; body semi-elliptical, arcuate, oblique
to the hinge-line at an angle of about 30° ; length about twice the height ;
anterior margin very oblique, slightly concave beneath the beak and gradu-
ally curving into the broadly rounded basal margin; posterior margin
obliquely truncate, slightly curving below.

Left valve convex in the lower part, gibbous from the middle upwards.
Right valve unknown.

Hinge-line straight ; length more than the greatest length of the shell.

Beak sub-anterior, obtuse, rising but little above the hinge-line, and
apparently not incurved. Umbonal region very gibbous, subtending an acute
angle.

Anterior end produced into an acute extension which is limited by a very
shallow byssal depression. Wing not defined, extending from the beak the
entire length of the shell, and produced beyond the posterior extremity of
the body ; margin very slightly concave, extending at nearly right angles to
the axis of the body.

Test of moderate thickness, marked by concentric striae. The casts show
distant, irregular, concentric undulations.

Hinge with a single continuous groove. The pallial line extends parallel
to the ventral margin, from a point anterior to the beak to below the middle
of the length of the body.

A large left valve has a length of 78 mm., with a height of 38 mm., and
hinge-line 90 mm. A smaller example has a length of 37 mm., height
23 mm., and hinge-line 40 mm.

238 PALEONTOLOGY OF NEW YORK.

All the specimens of this species are casts of the interior, with the single
exception of an individual which preserves the test very imperfectly. The
concentric undulations of the cast are often a conspicuous feature, and the
umbonal slope is occasionally obtusely subangular. The wing follows the
general contour and convexity of the valve.

Formation and localities. In the Upper Chemung group, associated witli
Spirifera Verneuili near Olean, Alleghany county ; in the vicinity of East Ran-
dolpli, and other places in Cattaraugus county, N. Y.

Pteronites rostratus.

PLATE XXII, FIG. 21.
Pteronites rostratus, Ham,. Pal. N. V., \ol. v, jit. 1. Plates and Explanations : PI. 22, fig. 24. Jan., 1883.

Shell of medium size, broadly semi-ovate ; body oblique at an angle of about
45" to the hinge-line ; length nearly twice the height ; ante-byssal margin
oblique, gently curving into the broadly rounded basal margin; posterior
margin somewhat obliquely truncate.

Left valve depressed-convex below, convex in the middle, and somewhat
gibbous above. Right valve unknown.

Hinge-line straight ; length greater than the greatest length of the shell.

Beak sub-anterior, sub-acute, prominent. Umbonal region moderately
gibbous, subtending an acute angle.

Anterior end nasute. Wing not defined, in direct continuation of the
convexity of the body, extending to the posterior extremity ; margin very
slightly concave, oblique to the cardinal line, slightly produced at the
extremity.

Test ornamented by fine, elevated, concentric strise, which are continued
over the body and wing without interruption, becoming crowded and some-
what fasciculate on the anterior side and on the nasute extension in front.

The umbonal region shows a few concentric imihilations, which are not
continued to the middle of the length of the valve.

LAMELLIBRANCHIATA. 239

Interior unknown.

The specimen described has a length of 29 mm., height 16 mm., and hinge-
line 31 mm.

This species is much smaller than P. -profundus, less elongate and less gibbous
in its proportions. The beak is apparently more elevated and angular, but
the angularity of the umbonal region is not continued along the body as in the
preceding form.

Formation and locality. In the shales of the Chemung group at Rockville,
Alleghany county, N. Y.

Pteronites inoptatus, n. sp.

PLATE LXXXVII, FIG. 5

Shell of medium size, broadly semi-ovate ; body ovate, oblique, making an
angle of about 25° with the cardinal line ; ventral and basal margins broadly
rounded ; post-basal extremity abruptly recurved.

Left valve regularly convex, slightly gibbous above. Right valve unknown.

Hinge-line straight, less than the greatest length of the shell.

Beak sub-anterior, directed forward, prominent and incurved over the
cardinal line. Umbonal angle acute.

Anterior end short, nasute ; extremity acute. Wing very narrow-trian-
gular, scarcely defined, joining the body at the posterior extremity ; margin
oblique, in direct continuation with the posterior extremity and curving
backward just beneath the cardinal line ; extremity acute.

Test marked by concentric strige of growth which are strongly fasciculate
on the anterior end and ventral margin.

Interior unknown.

The left valve described has a length of 38 mm., height 21 mm., and
hinge-line 33 mm.

This species is distinguished from the other forms of this genus by its narrow
wing and shorter hinge-line. It has the characteristic aspect of Pteronites
although approaching, in several particulars, to some species of Leptodesma.

Formation and locality. In the Chemung group, Mansfield, Tioga county, Pa.

240 PALEONTOLOGY OF NEW YORK.

PALyEOPINNA, Hall.
Pal^opinna flabella.

PLATE XXV, FIG. 18; AND PLATK LXXXVII, KICJ. 4.

Palcuyp'mna flabella, Hall. PjiI. N. Y., vol. v, pt. 1. Plates and Exi>lanations : PI. 25, fig. 18.

Jan., 1883.

Shell large, broadly semi-ovate, gaping at the anterior extremity ; axis oblique
to the hinge at an angle of about 30°; length nearly twice the height;
byssal margin abruptly truncate ; ventral margin very broadly curving ;
posterior margin oI)lique, sub-truncate.

Left valve depressed-convex in the posterior and ventral portions,
becomiuE: more convex above and moderatelv gibl)ous in the umbonal re<ri()n.
Right valve unknown.

Hinge-line straight, e({ualliiig the greatest length of the shell.

Beak antei'ior, terminal, prominent, directed forward, scarcely rising above
the cardinal line. Umbonal region subtending an acute angle.

Anterior end abruptly truncate ; margin excavate. Wing continuous with
the body of the shell without limitation or interruption ; margin directed
backward, nearly straight, continuous with the post-basal margin of the
body ; extremity abruptly rounded.

Test thin, marked by regular concentric striae of growth which are cancel-
lated by fine sub-equal radii ; in the cast the concentric and radiating striae
are of nearly equal strength, ^n the anterior end the radii are obscure or
obsolete as preserved in the cast.

Ligamental area narrow, marked by a single longitudinal groove and a
slight oblique furrow extending backward from the beak a little more than
one-third the length of the hinge.

The left valve described has a length along tlu' hinge-line of 80 nnii.,
height 40 mm. ; measured along the axis of the body the length is about 70
mm., and the anterior truncation is 25 mm. long.

LAMELLIBRANCHIATA. 241

The specimen described is a cast of the interior, preserving the surface
markings in a subdued condition. The anterior margin a2:)pears to have been
slightly incurved and the truncation resembles that in some forms of Solen.

Formation and locality. In the Oriskany sandstone, Schoharie, N. Y.

Pal^eopinna recurva.

IT.ATE XXV, FIG. li).
Palceophi/ia reciirva, Hali,. Pal. N. Y., vol. v, pt. 1. Plates ami Explanations: PI. 2o, %. 19. Jan., 1883.

Shell large, elongate semi-elliptical ; axis making an angle with the hinge-line
of from 20°-25° ; length greater than twice the height ; basal margin very
broadly curving ; posterior margin rapidly rounding and recurving tow^ard
the beak.

Left valve depressed-convex below, convex above and becoming gibbous
toward the beak. Right valve unknown.

Hinge-line straight, not extending as far as the posterior extremity.

Anterior end unknown. Wing not defined ; margin continuous with the
post-basal margin and abruptly incurving at the extremity.

Test thin, marked by fine sub-equal striae of growth, which become
lamellose on the pallial margin ; and by radii of unequal strength, which are
are sometimes strongly crenulated by the concentric striae. Anterior to the
middle of the shell the radii are obscure.

Interior unknown.

The specimen described is imperfect on the anterior end but preserves a
length of 120 mm., and a height 02 mm.

This species differs from the preceding in its larger size, broadly rounded
posterior extremity, and the hinge not extending as far as the posterior
margin ; the body is also more oblique and less convex.

Formation and locality. In limestone of the Upper Helderberg group,
Stafford, Genesee county, N. Y.
31

242 PALAEONTOLOGY OF NEW YORK.

ECTENODESMA, Hall.

ECTENODES.MA BIROSTRATUM.
I'LATIi XXUi, Flo.-.. -.'T-iu; ami PLATK LXXXIV, KIG. M

Ecleiiodesma birnslratuiii, H.vi.i,. Pal. N. V., vol. v, pt. 1. Plates and Explanations; PI. 23, figa. 27-30.

Jan., 1883.

Shell large ; body ovatu, ()bli(|U(j ; lieiglit greater than the length ; margin
regularly curving from the base of the anterior wing to the post-basal
margin, where it is somewhat abruptly recurved.

Left valve regularly convex below, gibbous in the umbonal region, some-
what arcuate, the point of greatest convexity being about the middle of its
length. Right valve concave below, depressed-convex in the middle, convex
on the umbo.

Hinge-line straight, iinicli longer than the length of the shell, and, in
extreme specimens, more than once ami a half greater than the length of
the shell.

Beaks acute, anterior to the middle of the shell, inclined forward, and
arching over the hinge-line. Umbonal region gibbous, limited on the
anterior side by a shallow undefined sulcus, and on the posterior side by the
abrupt depression ol' the body, subtending an acute angle.

Anterior wing large, triangular ; margin concave ; extremity produced to
an acuminate extension. Byssal sinus shallow and undefined. Posterior wing
large, triangular, joining the body below the middle of its height; margin
concave ; extremity produced into an acute termination.

Test of left valve marked with regular and even radii which are rounded
above, fattened and sometimes bifurcate below ; similar but more acute radii
continue over the posterior wing. In the right valve the ra\ s are more
numerous, hner and sharp, and are continued upon the posterior wing with a
little less force than on the body of the shell ; and very much subdued upon
the anterior wing; entire surface marked In' fine, even, concentric striae of
growth.

LAMELLIBRANCHIATA. 243

The specimens show an oblique Uiteral tooth, with obscure indications of
anterior teeth or folils. Ligamental area narrow, marked with fine parallel
striae.

A left valve has a length of 45 mm., height 50 mm., hinge-line, when
entire, about 75 mm. A small right valve has a length 34 mm., height
27 mm., hinge-line about 45 mm.

This species is distinguished by the great and nearly equal extent of the
hinge-line on both sides of the beak ; by the peculiar form of the body of the
shell ; and by its surface characters, which are unlike any yet observed.

Formation and localities. In the Chemung group at Franklin, Delaware
county ; and a right valve referred to this species is from a point four miles
above Chenango Forks, Chenango county, N. Y.

LIMOPTERA, Hall.

LiMOPTERA PAUPERATA.

I'LATli XXVI, FIG. 5.

LhiinpUra pattpfmta. Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. US. Dec , lS(i9.

Pal. N. Y., vol. V, pt. 1. Plates Hill 1 Explanations: PI. •->(), fig-. 5. J.an.. 1883.

Shell large ; body ovate, sub-erect ; wing greatly expanded ; height much
greater than the length; basal margin broadly rounded; posterior side
gently curving from the post-basal extremity to. the beak.

Left valve somewhat regularly convex from the umbo to the base. Ivight
valve unknown.

Hinge-line straight, longer than the greatest length of the valve.

Beak of the left valve prominent, inclined forward, rising above the
hinge-line, situated anterior to the middle of the liody of tlie shell.
Umbonal region moderately gibl)0us, abrupt ou the anterior, and more gently
sloping on the posterior side.

Auricle and byssal sinus unknown. Wing large, triangular, not distinctly
limited from the body, and extending nearly to the post-basal extremity of
the shell ; margin slightly concave ; extremity abrupt (rectangular ?).

244 PALEONTOLOGY OF NEW YORK.

Test marked by stronj^ rounded radii, with alternate smaller ones ; or finer
bifurcating rays between, which are somewhat curved as they approach the
beak. The entire surface of the shell is mai-ked by fine concentric striae,
which become crowded and lamellose, obscuring and partiallj' obliterating
the rays ; the striae on the lower part of the body are conspicuous, and also
on the wing and especially toward the hinge-margin. In the cast the rays
show a somewhat nodose character which is probably due to the unequal
weathering of the concentric lamellaj.

Interior characters and ligamental area unknown.

The .specimen described has an approximate height of 75 mm., and a
length of 65 mm. (The figure is incorrect in its proportions.)

This species differs from L. macroptera, and from L. cancellata, in its lesser
gibbosity and its much stronger radii. A single, ill-preserved, specimen from
the Hamilton group, possesses characters similar to this species, but the iden-
tity of the two cannot be positively determined without more material.

Formation and locality. In the higher beds of the Upper Helderberg lime-
stone at Stafford, Genesee county, N. Y.

LiMOPTERA CANCELLATA.
PI,.VTE XXVI, FIGS. 1-4 ; AND PLATE XCII, FIGS. 1-3.

Limoptera cancellata, Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. 16. Dec, 1869.

Miller, Cat. Araei-. Pal. Foss., p. 193. 1S77.

Pal. N. Y., vol. V, pt. ]. Plates and Explanations: PI. 26, figs. 1-1.
.Jan., 1883.
TAmoplera cancellata, var. occideas, H. axd W. Twenty-Foui-tli An. Rep., N. Y. State Museimi Nat. Hist.,

p. 199, pi. 11, fij,'-.'*. 12-].^. 1872.

Shell large ; body sub-erect, broadly ovate ; axis nearly vertical to the hinge-
line ; wing expanded ; height and length nearly equal ; ventral margin
very broadly rounded ; anterior margin expanded below and contracted
above ; post-basal side expanded, recurving somewhat abruptly and extending
in a sub-arcuate line to the beak.

Valves very unequal. Left valve moderately convex below, gradually

LAMELLIBRANCHIATA. 245

becoming gibbous and arcuate above. Right valve concave below, flat in the
middle and dejiressed-convex in the umbonal region.

Hinge-line straight, less than the length of the valve.

Beak of left valve prominent, anterior to the middle of the valve, acute,
inclined forward and arching over the hinge-line. Umbonal region promi-
nent, gibbous, abruptly limited on either side. In the right valve the beak
does not rise above the cardinal line. Umbonal region defined on the ante-
rior side by a distinct oblique fold or ridge, and on the posterior side by a
well-marked depression limiting the wing, subtending an acute angle.

Ear small, limited by a shallow sinus below. Wing large, triangular,
extending more than half the height of the shell toward the base ; margin
gently concave and slightly recurving toward the hinge-line ; extremity
angular.

Test of moderate thickness, marked by somewhat distant, rounded,
abruptly elevated radii, with wider intermediate flat spaces which are some-
times marked by one or more smaller rays. In the pa,rtial cast, these rays
are crossed, and the intermediate spaces cancellated, by fine concentric striae.
Towards the ventral and baso-lateral margins the shell is lamellose and the
radii become obsolete. The concentric strife are crowded upon the wing,
and the radii are less conspicuous than on the body of the shell.

Ligamental area in left valve large ; smaller in the right valve. The pallial
line in the left valve forms a distinct nodose ridge, which extends from the
rostral cavity in a slightly arcuate line to below the middle of the valve.
In the right valve, the pallial line in the cast extends along the ridge,
limiting the body of the shell from the anterior alation. In the cast of the
left valve, the umbonal cavity is marked by numerous nodes indicating pits
in the shell for muscular attachment. The posterior muscular impression is
large, occupying the post-umbonal slope at a point about half-way from
the beak to the base of the shell.

A cast of the interior has a length of about 78 mm., height 77 mm., and
hinge-line less than the length of the shell.

246 PALMONTOLOGY OF NEW YORK.

This spc'i'ies is (listiiigiiislicd by its erect I'urm, the Ijruiul tlat interspaces
between the radii, and the regular sharp concentric striaB.

Formation and locality. The specimen is I'roni the higlier t)eds of limestone
at the Falls of the Ohio, which arc of the age oftlic llainiltun Lumni.

LlMlll'TKKA MACKDl'TERA.

PLATE XXIV. FIU U, I'l.ATK XXVI, FIGS 0-9 ; I'LATE XXVU, FKiS 1-10; I'l-ATi; \X\1I1. FKiS 4, S ; I'LATE

XXIX, FIGS. I-l ; AND I'LATE XCII, FIGS. 4-9

Lima mne-riiptrrn, Co:<r.IlD. Annual Report N. Y tteolog'. Snrv., p. 117. 1S3S.
Limaplern inaj-rnptcin (Co.nkad), Hall. Prelim. Notice Lara. Shells, etc., pt. "J. p. 17. Dec, 1S69.

S. A. Mii.i.ER, Cat. Amer. Pal. Fo.s.s. 1877.

IIai.i.. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 24, fig. 14 ;
pi. 2I>, figs. 0-9 ; pi. 27, figs. 1-10 ; pi 28, fig.<. 4, .5 ; and pi. 29.
figs. 1-4. .Ian., 1883.

Shell large ; including the cardinal expansions, the form is subquadrate ; body
broadly ovate, erect or moderately oblique ; wing more or less expanded ;
height one-fourth to one-third greater than the length ; basal margin broadly
rounded, with the anterior and posterior sides sub-parallel.

Valves very uiu'<|ual. Left valve ranging from moderately convex to
very gibbous, often .somewhat regularly arcuate from Ijeak to base. Right
valve smaller than the opposite, in young specimens nearly tlat l)elow,
depressed-convex in the middle, and more convex in tlie umboual region;
iu specimens of medium size there is often a greater convexity in the upper
part, and in very old specimens the surface is depressed-convex ami nearly
flat in the lower part.

Hinge-line straight, sometimes equalling but usually less than the length
of the .shell.

Beak of the left valve proiuiueiit, acute, iiicliiHMl lorwanl, rising above and
arching over the cardinal line, situated anterior to the middle of the l)ody of
the shell. Umbonal region proiuiiient, convex in yuiuig shells and gibbous
in older ones, limited anteriorly l)y a distinct sulcus, and posteriorly Ijy the
abrupt umbonal slope. Beak of right valve acute, scarcely rising above the
hinge-line, defined anteriorly by the byssal sulcus, and posteriorly by the
abrupt depression and distinct limitation of the wing. Umbonal angle acute.

LAMELLIBRANCHIATA. 247

Ear small, well-ck'tine:l in young specimens, and scarcely increasing in
size in proportion to the growth of the shells, limited by a distinct byssal
depression; extremity rounded. Wing large, triangular ; margin more or less
concave in young shells, aud often nearly straight in older shells ; extremity
produced or rectangular, often extending beyond the posterior margin of the
valve.

Test thick, especially in the umbonal region ; marked by distinct sub-
equidistant, rounded railii, with slightly concave interspaces, in which are
often finer, or obscurely developed rays ; the right valve is usually more
closely and less strongly marked by them than the left. The radii are
crossed and crenulated by elevated, lamellose, concentric strife, which are
more distant and conspicuous on the right valve. In the 3^oung shells, the
radii are conspicuous on the wing; they are a little more distant than on
the body of the shell, and often ol^solete along the line of the junction of the
wing with the body, especially in the right valve. In both valves, the radii
become obscure or obsolete below the centre, and the surface is marked by
strong, irregular, concentric, lamellose undulations. The radii often become
more or less obsolete upon the wing, while remaining conspicuous on the
body of the shell.

Ligamental area extending the entire length of the hinge-line, much wider
in the left valve ; marked by coarse parallel, undulating, longitudinal grooves
or strise. There is a conspicuous oblique posterior lateral tooth, and two
strong cardinal folds beneath or just anterior to the beak. Anterior
muscular impression situated in the rostral cavity ; the pallial line continues
thence in a curve somewhat parallel to the margins of the shell, turning
inward below the middle of the height and joining the large muscular
impression.

The right valve of a young individual (plate xxiv, fig. 14) has a length
of 30 mm., height 35 nmi., and hinge-line 32 mm. The margin of the left
valve, which remains in the matrix, shows it to have had a length of 42 mm.,
and a height of 53 mm. Another specimen, with the two valves attached,
has the left valve 75 mm. and the right valve 55 mm. in height, while the

248 PALEONTOLOGY OF NEW YORK.

leiij^th of tlio two valves respectively is 63 and 43 mm. In anotlier
.specimen (plate xxvii, figs. 6 and 7), where the two valves are in juxtapo-
.^ition, there appears to be little difference in the relative dimensions, but
this appearance is in a great measure due to the fact that the margins of the
left valve have been l)roken away to tlio line nl' imiction of iIil' two valves.
Tlie proportional (liiiicnsions of the left valves are subject to iimch variation,
as is shown in ])late xxvii, figs. 2 and 3.

The measurement of two large specimens gives respectively, length 78
and 74 mm., height '.•() mm. each, and hinge-line 58 and 65 mm. A large
specimen with the margin imperfect has a length of 88 mm., and height 112
mm. A separated right valve has a length of 97 mm., heiglit 103 mm., and
hin2:e-line 84 mm.

The young shells ol' this form, especially the right valves, might readily be
mistaken for Aviculopecten or Pterinopeden ; but a critical examination will show
the radii to be peculiar and chiiracteristic of the genus.

The form and proportions of the fossil are subject to great \ariations in
their natural conditions, but the variation and distortions of form, consequent
upon the degree and direction of pressure from the inclosing matrix, produces
much greater extrcMiics. Some of the distorted forms are illustrated on plates
xxviii and xxix. In llie older specimens, the obliteration or obsolescence of
the radii beloAv the middle of the valve, gives a great variety of aspect to the
fossil. These variations are illustrated on plates xxvi, xxvii and xxviii.

In all the younger specimens, the wing is produced, ami the margin sinuate,
while the surface is distinctly marked by the radii. These features are
gradually lost as tlie slu-ll advanct-s in age, until the margin of the wing
becomes nearly oi- (|nit(' direct, the extremity of the wing obtuse, and tlie
surface marked only by the concentric strise of growth. In old specimens the
ear is often obscure, and scarcely retains the pro])ortionate size of that
appendage in the younger shells.

Formation and localities. In the Hamilton group, at Cazeuovia and other
localities in Madison county, and in Otsego and Onondaga counties, N. Y.

LAMELLIBRANCHIATA. 249

LiMOPTERA OBSOLETA.

PLATE AXIX, IIGS. 5, 6; PLATE XXVI, FIG. 10? ; AND PLATE XCII, FIG. 10.

Lini'jptei-a ol suleta. Hall. Prelim. Notice of Lam. Shells, etc., pt. 2. Dec, 18ti9.

Pal. N. Y., vdl. V, pt. 1. Plates and Explanations: PI. 2fl, tig-.s. 0,(1. Jan., 1883.

Shell large ; body ovate, erect or slightly oblique ; height greater than the
length ; basal mai'gin regularly rounded ; anterior side broadly convex and
contracting to the byssal sinus ; posterior side abruptly recurved from the
base, and extending in a nearly direct or slightly concave line to the extremity
of the wing.

Valves very unequal. The right valve much depressed or nearly flat ; the
left valve depressed-convex Ijelow, regularly convex in the middle, and
gibbous in the umbonal region.

Hinge-line straight, nearly rectangular to the axis of the body of the
shell, less than the length of the valve.

Beak of left valve prominent, acute, inclined forward, situated anterior to
the middle of the body, rising much al)ove the beak of the right valve, and
arching over the cardinal line. Umbonal region prominent, and sometimes
gibbous, limited anteriorly by a distinct broad depression, and posteriorly by
the abrupt umbonal slope ; subtending an acute angle.

Ear small, limited by the byssal sinus. Wing moderately large, triangular,
extending below the middle of the length of the body ; extremity abruptly
rounded.

Test thick, marked by irregular concentric striie of growth, which are
crowded and strongly lamellose on the lower half of the body and on the
anterior and posterior sides. On the wing, just below the cardinal line, the
strige turn gently outward. In some specimens there remain obscure indica-
tions of radii.

Ligamental area wide, extending the entire length of the hinge-line ;
marked by coarse undulating stria? and wider intermediate grooves. Other
characters of the hinge and interior not observed.

One of the specimens figured has a height of 88 mm., and another of 100
32

2:>0 PALEONTOLOGY OF NEW YORK.

imn. ; the approximate length is 70 mm. and 88 mm., respectively. Another
specimen has a length of 77 mm., and a height of 90 mm. A larger speci-
men has a length of 90 mm., and a height of 100 mm.

The specimens of this species occur in the softer shales of the Hamilton
group, and it is possible that long maceration has had some influence in olilitc-
rating the radii ; but L. macroptera, with its more convex form, and marked bv
its characteristic radii, occurs in the same localities. Although not entirely
satisfied in regard to its specific distinction, it may be convenient to separate
this at least as a varietal form.

Formation and localities. In the Hamilton group, at Hamilton, Madison county,
at Delphi, Onondaga county ; and on the shore of Cayuga lake, N. Y.

LiMOPTERA CURVATA.
PLATE XXVIII, FIGS. 1-3.

TAmoptera ciurata. Hall. Prdiiii. Nnticc L.im. Shcll.-^, etc.. part 2, p. IS.- Doc, 1860.

" " Pal. N. Y., vol. V. )it. 1. Plates and Exphinjitinn.s: PI. 28, figs. 1-3. .Ian.. 1S&3.

Shell large, sub-rhomboid-ovate in outline ; body broadly ovate, arcuate,
expanded on the antero-basal margin.

Valves very unequal. Left valve very gibbous in the middle and umbonal
region. Right valve depressed-convex below, becoming somewhat gibbous
on the umbo. Left valve, with the beak, very prominent and incurved ;
beak of right valve rising but little above the hinge-line.

Test thick, marked by strong rounded radii with intermediate finer lines
which become obsolete on the lower part of the valve. The radii are crossed
by fine, closely arranged striae of growth, which at intervals are crowded and
lamellose, especially toward the margin of the valve.

The internal cast shows the anterior muscular impression situated at the
extremity of the rostral cavity, from which the pallial line, marked In- a
row of strong pustules, extends nearly parallel to tlic anterior margin for
more than one-third the length of the valve ; thence broadly curving, it
extends below the middle of the valve, and recurves into a large sub-circular

LAMELLIBRANCHIATA. 251

muscular impression on the post-umbonal slope. The interpallial area is
finely pustulose.

This variety was originally separated from L. macroptera by reason of its
proportionally broader, shorter, and more gibbous form ; the arcuation of the
body of the left valve, and its expansion on the <antero-basal margin. In a
single example of the left valve, the radii are much stronger than usual in
typical specimens of the other form, and the interstitial radii more strongly
developed. These characters, and others upon which the species was originally
founded, when compared with a large number of individuals of the genus, are
represented with many modifications, and the specific distinction is here
continued with much reservation.

On comparing the typical specimen of Mr. Conrad's L. macroptera, we find
it proportionally shorter and wider than many specimens since referred to the
same species ; measuring 63 mm. in length and about 78 mm. in height, the
left valve very gibbous and the body sub-arcuate ; the proportions being very
nearly the same as in L. curvata, represented in fig. 2, of plate xxviii.

Formation and localities. This species occurs in the Hamilton group at
Cazenovia and other places in Madison county, N. Y.

2513 PALEONTOLOGY OF NEW YORK.

B Y S S 0 P T E R 1 A , Hall.
Byssopteria radiata.

PLATE XXXII, FIGS. 21, 22; a.mj I'L.VTE I.XXX, KIG. 11.

Mijtllarca radiata, II.vli.. MS. 1877.

S. A. Miller. Cat. Amor. Pal. Fos.sils. 1877.
Byssirpltria radiata. H.vll. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 32, tif,'?. 21,22;

pl. 80, fig. 11. Jan., 1883.

Shell large, wide-triangular, alate posteriorly ; body undefined : length about
five-sevenths of the height ; anterior margin vertically truncate the entire
height of the shell ; basal and posterior margins broadly rounded.

Valves sub-equal, depressed-convex on the basal and post-basal sides, sub-
angularly gibbous on the umbo and along the anterior side.

Hinge-line straight, less than the length of the shell. Beaks anterior,
acute, elevated, and directed forward. Anterior end sub-nasute.

Test marked by strong, sub-equal, rounded radii which are wider than the
interspaces, often bifurcating below the middle of their length, and on the
outer portion of the undefined wing they are fasciculate and finer. Enth-e
surface marked by striae of growth which become elevated into fascicles
tow^ard the margins.

Interior unknown.

A right valve has a length of 55 mm. and height 72 mm. A left valve
measures 54 mm., in length, and 79 mm., in height.

This species is unlike any Pectinoid or Aviculoid form described in this
volume, and has somewhat the aspect of several species of Ambonychia from
the lower rocks, although probably very distinct in its generic relations.

Formation and localitij. In the Upper Chemung gi'oup at Mansfield, Tioga
county. Pa.

LAMELLIBRANCHIATA. 253

MYTILARCA, Hall.

Sub-Gentjs PLETHOMYTILUS, Hall.

Mytilarca (Plethomytilds) arenacea.

PLATE XXX, FIG. 1 ; and PLATE LXXXvII FIG. 10.

Mytilarca arenacea, Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. 20. Dec, 1869.

" " " S. A. Miller in Cat. Amer. Pal. Foss. 1877.

Pletlurmytiltis " " Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 30, fig. 1. Jan., 18S3.

Shell of medium size ; body ovate, acute at the apex, slightly oblique ; height
equal to about three-fourths of the length. Byssal area concave ; margin
straight below to a point three-fourths of the length from the apex ; abruptly
curving to the posterior and basal margins ; post-basal and dorsal margins
gently curving to the extremity of the hinge-line.

Valves moderately convex below, becoming gibbous in the umbonal region,
and upon the anterior umbonal slope.

Hinge-line straight and short. Beaks anterior, prominent, rising above
the cardinal line, moderately incurved. Umbonal angle acute. Posterior
alation narrow and short, merging into the general contour of the margin
above the middle of the length of the shell.

Test thick, marked by fine concenti'ic striae of growth, which at some-
what regular intervals are crowded, and raised into imbricating lamellte, as
shown in casts of the interior.

A valve of the ordinary size measures about 60 mm. in length, and 45
mm. in its greatest height.

The fossils of this species are known only as casts of the interior, in an
arenaceous matrix, and are usually more or less imperfect, the narrow
posterior alation being rarely pi'eserved in connection with the body of the
shell.

Formation and localities. In the Schoharie grit at Schoharie, and in the
Helderberg mountains, Albany county, N. Y.

■2'A PALEONTOLOGY OF NEW YORK.

Mytilarca (Plethomytilus) poxderosa.

rl.ATK X.W, KIGS. -.'-7

Mi/lilaira piDidf-roxd. 1I.U.I,. Prelim. Notice Lam. Shells, etc., p:, 2, ],. -21. I)>m'., 1800.

IIali.. S. a. MiLiKH, Cat. Amor. Pal. F().s.s. 1S77.
Phthnmiililnx poinlfioxux, Hall. Pal. N. Y'., vol. v, jit. 1. Plates ami Kxiilanatioiis : PI. 30, lig«. 2-7.

.Ian.. lS,S.i.

Shell very large; body acutely ovate, erect ; height tliree-fiftlis the length;*
ventral margin nearly straight or .^lightly concave for about one-halt the
. length of the shell; posterior anil lia.<al margins abruptly roiuiilcil : dorsal-
margin gently curved to the exlreiuity of the hinge-line.

\'alves equal, regularly convex posteriorly, gibbous above and in the
umbonal region.

Hinge-line straight and short. Beaks anterior, proniincnt, rising much
above the cardinal line, moderately incurved. \ Ciitral side concave with a
slight intlation ot'tlic margin at the In'ssal opciiiiii:-. Dorsal side sub-alate.

Test thick, marked by concentric striaB of growth uhicli liccomc lamcllo.se
toward the margin.

Ligamental area finely and evenly striated longitudinally, in old shells
becoming very wide, indicating great thickness of the test.

Interior unknown.

A large specimen, which is a cast of the interior, has a leiigtli of lo") mm.,
height 80 mm., breadth 80 nun. A small example has a length of 36 mm.
and height 23 mm.

This species differs from Mijtilurca (P.) arenucca in its greater size and gil)-
bosity ; from M. {Pkthoynytilus) cordiformis, 11\ll=M. (P.) mijilimera, Coxrad,
and M (P.) ovata. Hall, from the Lower Helderberg group, in its moi'e elongate
form and more attenuate apex.

Formation and localities. In the limestone of the L'pper Helderberg group,
Helderberg mountains, Albany county, X. Y. ; Clarence Hollow, Erie county,
N. v.: and in limestone (jf the same age at (Jolundius, Ohio, and Walpole,
Ontario.

*Iii the mytiloid fdi'iiis the lenffth is measured from the beak to the posterior extremity and the heit'lit is
at rig-ht angles lo this. The breadth represents the convexity of the valves.

LAMELLIBRANCHIATA. 255

Mytilarca (Plethomytilus) oviformis.

PLATE XXXI, FIGS. 1-8; and PLATE LXXXVII, FIG S.

Inoceramus oviformis, Conrad. Jour. Acad. Nat. Sci., Phila., vol. viii, p. 246, pi. 13, fig-. 7. 1842.
Mytilarca oviformis (Conhad), Hall. Prelim. Notice Lam. Shells, etc., jit. 2, p. 21. 1869.
Plethomytilus oviformis (Co.vrad), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations ; PI. 31,

fig-s. 1-S. Jan., 1883.

Shell large ; body ovate, erect, wide posteriorly and acute above ; length about
one-fifth greater than the height ; ventral margin for nearly half the length
of the shell nearly direct, thence gently curving into the posterior extremity
which is broadly rounded ; dorsal margin very gently curved.

Valves equal, regularly convex in the posterior part, becoming gibbous
in the umbonal region.

Hinge-line straight, less than the height of the shell. Beaks prominent,
anterior acute, and incurved, rising above the cardinal line.

Ventral side truncate with a small fold for the passage of the ))yssus.
Dorsal side sub-alate.

Test thick, marked by fine, close strise of growth which at intervals are
fasciculate and raised into lamellose elevations and very much crowded and
elevated on the ventral side of the shell.

Ligamental area wide, finely striated longitudinally and occasionally
preserving one or two oblique folds which may have been lateral teeth.
Other characters of the interior unknown.

A large specimen has a length of 74 mm. and height 55 mm. A small
example measures 25 mm. in length and IT mm. in height.

This form diflters from M. (P.) ponderosa in its greater proportional height,
smaller size, and lesser gibbosity.

Fonnation and localities. In the shales of the Hamilton group at numerous
localities in Schoharie, Otsego, Onondaga, Ontario, Livingston and Erie
counties, N. Y.

2r,0 PALAEONTOLOGY OF NEW YORK.

MyTILARCA (PlETHOMYTILUS) KnAPPI. n. Sj).
I'l.ATI-; I.XXXVII, KIC. 13

Shell ul' medium .size; body ovate, obtuse, liru;nl lielow ; hei,<,4it nearly equal
to the length ; ventral margin rounded with a slight sinuosity at the byssal
opening; dorsal margin broadlx roiiiidcil.

Ri'dit \:il\c iiioilcniti'h cdiiveN below, somewhat iiKire convex in the
umbonal region. Left valve unknown.

Hinge-line less tlian tlie lieiiiht of the shell. Beak obtuse.

Test thin below, thicker on the upper part and cardinal line. Surface
marked by fine, regular, elevated striae of growth.

Ligamental area narrow, coarsely striated longitudinally.

Interior unknown.

The right valve described has a length of i8 mm. and height 44 mm.

This species differs from M. (P.) oviformis in its proportionally greater height,
less attenuate beak, lesser convexity and the coarsely striated ligamental area.
The relations of this species are somewhat obscure, owing to the obscure limi-
tation of the beak and the effects of maceration and compression. It is
however clearly distinct from any of the forms here descriljed.

Formation and locality. In the shales of the Hamilton group on the shores
of Skaneateles lake, N. Y.

Mytilarca pyramidata.

ri.Aii-; l.wx, I'HiS 1 :!.
MytVarcn.p)jram\datn.U.\\.\.. I'.il. N. Y.. vol. v, j.l 1. I'hi'.i's iin.l i;x|ilaii:itinns : PI. SO, Hirs. 1-3. .liiii., 1SS.S.

SiiKLi- of medium size; Ijody sub-angularly ovate, pyramidal; length one-third
greater than the height ; ventral margin truncate and concave, curving
abruptly into the basal margin; dorsal margin very gently < urx ing to the
beaks.

Valves equal, convex, gibbous above, and sub-angular along tbc anterior
umbonal .slope. The ventral side is rectangularly incurved.

. LAMELLIBRANCHIATA. 251

Hinge-line short. Beaks acute, extremely elevated, directed slightly
forward and curving over the cardinal line.

The test has not been preserved. The casts are nearly siriooth, but show-
ing lamellose stri« on the pallial mai-gin.

Interior unknown.

A specimen of this species has a length of 36 mm., height 23 mm., breadth

22 mm.

«

This form is shorter, more gibbous, more attenuate towards the beak, and
less rounded on the posterior side than M. Chemungensis.

Formation and locality. In the Schoharie grit, Schoharie count}', N. Y.

Mytilarca umbonata.

PLATE XXXII, FIGS. 1-7.
Mj/tllarca umbo7iata,'ii>i.LL. Pul. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 32, tig-s. 1-7. Jan., 1883.

Shell small to medium size ; body ovate, acute above ; length more than one-
third greater than the height ; ventral margin truncate, inflated at the byssal
opening ; basal margin abruptly rounded.

Valves equal, strongly convex in the lower part and narrowly gibbous in
the umbonal region. Ventral umbonal sloj)e obtusely angular, concave
between this and the ventral margin. Dorsal side not alate.

Hinge-line short. Beaks acute, elevated, nearly vertical, arching over the

cardinal line.

Test thin, marked by fine concentric lines of growth which become

crowded and lamellose toward the pallial margin.
Interior unknown.
A specimen has a length of 33 mm., height 18 mm., l)readtli 19 mm.

This species differs from M. Chemungensis in its shorter and more gibbous
form ; the beaks more elevated and erect.

Formation and localities. In the Middle Chemung group, Ithaca, N. Y., and
near Mansfield, Pa.

33

258 PALEONTOLOGY OF NEW YORK.

Mytilarca Chemungensis.

PLATE XXXTT. FIGS. 8-11, 13, 14

Inoceramiis Chemangensis, Coxrad. Jour. Acail. Nat. Sci., Phila., vol. 8, p. 24G, pi. 13, fig. 9. 1842.
Mytilus Chemungen.H.1 (Conrad), Phillips and Salter. Memoirs Geolog. Surv. of Great Britain, vol. 2, pt.

1, p. 365, pi. 20. figs. 10, 11. 1848.
Mytilarca Chemungensv! (Conrad), Hall. Prelim. Notice Lara. Shells, etc., p. 23. 1869.

<■ " " '• Pal. N. Y., vol. V, pt. 1. Plates and Explanations : PI. 32, figs.

8-14 (pi. 33, fig. 8, in eiTOr). Jan., 1883.

Shell of medium size, much elongated from beak to posterior extremity ; body
narrow, elongate-ovate, sub-arcuate ; length averaging twice the height but
with considerable variation ; ventral margin nearly straight, slightly concave
for nearly three-fourths of the length ; basal margin abruptly rounded ;
dorsal margin gently curving.

Valves equal, convex in the posterior part, gibbous above ; the greatest
convexity a little above the middle. The ventral unibonal slope is obtuse,
sloping nearly vertically to the ventfal margin.

Hinge-line short, oblique. Beaks elevated, acute, anterior, slightly
incurved.

Test thin, marked by very fine concentric striae, which toward the mar-
gins are often fasciculate and sub-imbricating.

Ligamental area finely striated longitudinally. Cardinal teeth small,
diverging, situated immediately under the beak. Other characters of the
interior unknown.

The proportions of length and height are subject to great variation. A
short example has a length of 26 mm. and height 17 mm. A specimen of
ordinary proportions has a length of 5.3 mm. and height 26 mm. An
elongate form has a length of 56 mm. and height 22 mm.

This species differs from M. carinata in its comparatively longer form ; the
ventral umbonal slope less angular ; and the body less arcuate.

Formation and localities. In tlic middle portion of the Chemung group,
Rockville, Hobbieville and Phillipsburgh, Alleghany county, and East
Randolph, Cattaraugus county, N. Y.

LAMELLIBRANCHIATA. 259

Mytilarca carinata.

PLATE XXXII, FIGS. 15-19 ; AND PLATE XXjaH, FIG. 8.

Mytilarca carinata. Hall. MSS. 1877.

" " " S. A. MiLLEK, in Cat. Amer. Pal. Foss., p. 197. 1877.

" " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 33, fig-s. 15-19.

Jan., 1883.

Shell of small or medium size ; body obliquely sub-ovate ; length nearly twice
the height, except in young specimens ; ventral margin nearly straight or
slightly concave for more than three-quarters of the length of the shell,
thence rounding abruptly into the basal margin, then more gently rounded
into the gently curving dorsal margin.

Valves equal, depressed-convex in the posterior part, becoming moderately
convex in the middle and scarcely gibbous above. The ventral umbonal
slope is angular, and the shell between it and the margin is concave.

Hinge-line short, less than the height of the shell. Beaks anterior, prom-
inent, acute, slightly curving forward.

Test thin, marked by very fine concentric strias of growth, which are
crowded on the anterior side and toward the base.

Ligamental area of moderate width, finely striated longitudinally.
Cardinal teeth small, diverging, situated under the extremity of the beak.
Lateral teeth two, small, oblique, situated just below the posterior extremity
of the hinge-line. Other characters of the interior unknown.

A specimen has a length of 30 mm. and height 18 mm. A more elongate
form has a length of 43 mm. and height 20 mm. A small individual has a
length of 23 mm. and height 15 mm.

This form diflers from M. Ckemungensis in its proportionally shorter form,
the young shells have a sub-triangular aspect, the ventral umbonal slope is
always angular, and the body is more distinctly arcuate.

Formation and localities. In the middle portion of the Chemung group, Tioga
and Chemung counties, N. Y.

260 PALEONTOLOGY OF NEW YORK.

MyTILARCA REGTJLARIS, 11. sp.

PI-ATK XXXII, YUi. I--'.

Shell al)Ove the medium size ; body narrowly ovate ; length less than twice
the height ; byssal area scarcely depressed ; ventral margin for two-thirds
the length nearly straight, thence curving into the posterior margin which
is regularly rounded ; dorsal margin gently curving to the extremity of the
cardinal line.

Left valve gently and regularly convex in the posterior half, convex above
and scarcely gibbous on the umbo. Right valve unknown.

Hinge-line straight, short, olilique. Beak nearly erect, acute and abruptly
attenuate.

Test thin, marked by fine elevated concentric strife wliicli arc crowded on
the ventral and dorsal sides of the valve.

Ligamental area narrow, longitudinally striated.

Interior unknown.

The specimen described has a length of 48 mm. and height 28 mm.

As compared with M. Chemungensis this species has a proportionally wider
form ; it is more nearly equilateral, the umbonal elevation is less abrupt and
more nearly central. It is proportionally higher than M. ocddentalis and less
elevated along the umbonal slope.

Formation and locality. In a sandstone of the Chemung group, near Leon
Centre, Cattaraugus county, N. Y.

Mttilarca attenuata.

PLATE XXXn, FIG. •!«.

Mytilarca altcnmita. Hall. Pi-elim. Notice Lam. Shells, etc., pt. 2, ii. 23. 18G9.

" " " Pill. N. v., vol. V, pt. 1. Plates and Explanations : PI. 32, fig. 20. Jan., 1SS3.

Shell above medium size ; body extremely elongate, sub-cuneiform : length
nearly three times the height ; ventral margin nearly straiglit for almost the
entire length, with a slight depression at the byssal opening; posterior

LAMELLIBRANCHIATA. 261

margin abruptly rounded, gently curving into the dorsal margin which is
straight above the middle.

Right valve gently convex in the posterior part, becoming gibbous and
angular in the umbonal region. Left valve unknown.

Beak erect, acute, pointed.

Test of moderate thickness, marked by fine concentric strise of growth,
which at intervals have been raised into lamellae which have left strong
varices upon the cast.

Interior unknown.

A right valve has a length of 65 mm. and height 24.5 mm.

This species differs from M. Chemungensis in its more elongate, straighter form,
and in the angularity of the umbonal slope. From M. carinata it is distin-
guished by its elongate form, straight ventral side, and more prominent anterior
umbonal slope.

Formation and locality. In the arenaceous beds associated with fossils of the
middle Chemung group, from a loose mass collected at Elmira, N. Y.

Mytilarca simplex.

PLATE XXXIII, FIGS. 19, 21.

Mytilops (Modiola) simplex. Hall. Pal. N. Y.. vol. v, pt. 1. Plates and Explanations: PI. 33, figs. 19,

21 (20 in error) Jan., 1883.

Shell of medium size ; body elongate-ovate, with an acute apex ; length nearly
twice the height ; byssal area depressed ; margin below nearly straight for
two-thirds the length ; posterior margin abruptly rounded ; dorsal margin
gently curving to the hinge-line.

Valves equal, moderately convex in the posterior part, and gibbous on the
umbo. The line of greatest convexity is on the ventral side of the axis.

Hinge-line short. Beaks sub-erect, acute, abruptly attenuate.

Test marked by fine, closely arranged, concentric striae.

Ligamental area and interior unknown.

A specimen has a length of 41 mm. and height 25 mm.

262 PALEONTOLOGY OF NEW YORK.

This species is somewhat intermediate to M. Chemungensis and M. regularis,
but is distinguished from the former by its shorter form, and from the latter
by its greater convexity and more attenuate beak. This form and the suc-
ceeding, were referred to Mytilops, but a careful comparison shows them to lie
related to the species here arranged under Mytilarca.

Formation and locality. In the sandstones of the Chemung group, west of
Smethport, Pa.

Mytilarca gibbosa, n. sp.

PLATE XXXIII, FIG. 20 ; AND PLATE LXXXVII, FIG. 7.

Shell of medium size ; body ovate-arcuate, obliquely truncate along the hinge-
line ; length less than twice the height ; ventral margin nearly straight for
more than three-fourths the length, abruptly curving into the posterior
margin, thence gently rounded to the extremity of the hinge-line.

Left valve very convex; the greatest convexity above the middle.
Umbonal region gibbous. Right valve unknown.

Hinge-line oblique, nearly equal to the height of the shell. Beak small,
appressed, arching toward the ventral side.

Test marked by fine concentric striae, which, at irregular intervals, are
crowded into fascicles, leaving varices iipon the surface of the cast.

Interior unknown.

The specimen described has a length of 45 mm., and height 26 mm.

This species is proportionally longer, beak more acute, and much more
gibbous than M. lata.

Formation and locality. In the Upper Chemung group, Napoli, Cattaraugus
county, N. Y.

Mytilarca lata.

PLATE XXXIII, FIG. 22.
Mytilops (Modiola) lata. Hall. Pal. N. Y.. vol. v. i)t. 1. Plates and Explanations: PI. 33, fig. 22 Jan., 1883.

Shell large ; body broadly sub-elliptical, abruptly narrowing toward the beak
on the dorsal side ; length one-third greater than the height ; byssal area

LAMELLIBRANCHIATA. 263

slightly inflated, thence nearly straight for almost three-fourths the length
of the shell ; posterior margin broadly rounded ; dorsal margin gently curved
for two-thirds of the length and then truncated in nearly a direct line to the
beak.

Right valve moderately convex in the posterior part, becoming broadly
convex in the middle, and somewhat gibbous in the umbonal region. Left
valve unknown.

Hinge-line oblique ; extent unknown. Beak elevated, erect, acute.

Test marked by rather coarse, elevated lines of growth.

Interior unknown.

The specimen described has a length of 60 mm. and height 40 mm.

This species somewhat resembles M. regularis but the beak is more anterior,
the body wider and more convex, and the truncation of the cardinal margin is
much longer.

Formation and locality. In the Chemung group, Randolph, Cattaraugus
county, N. Y.

Mytilarca occidentalis.

PLATE XXXIII, FIGS. 3-o ; and PLATE LXXXVII, FIG. U.

Mytilus occidentalis. White and Whitfield. Proc. Boston Soc. Nat. Hist., vol. viii, p. 297. 1862.
Mytilarca occidentaJ is (W. and W.). Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. 24. 1869.

" " " Pal. N. Y., vol. V, pt. 1. Plates .and Explanations: PI. 33,

figs. 3-5. Jan., 1888.

Shell above the medium size ; body extremely elongate, narrow-ovate ;
length more than twice the height ; ventral margin a little inflated at the
byssal opening, then gently curving to the posterior margin which is abruptly
rounded, and broadly curving along the dorsal side.

Valves equal, convex in the posterior part, becoming gibbous below the
middle and anteriorly ; the greatest convexity is anterior to the middle.

Hinge-line short. Beaks acute, nearly erect. The umbonal region is
narrow and the convexity is continued along the median line to the posterior
end of the shell.

264 PALEONTOLOGY OF NEW YORK.

Test thin, marked by numerous fine concentric striae, which at irreguhir
intervals have been raised into iinbrifatintr ]aniolla\ loavinff stronir varices
on the cast.

Interior unknown.

A specimen has a length ol' -yl mm. and bright '!■> nmi.

Tliis species is distinguished from M. Chemungensis by its straighter foi-in,
erect beaks, and convexity along the medial line.

Formation and locality. In the Yellow sandstones, at Burlington. Iowa.

Mytil.'\rc.\ fibristriata.

PLATE XXXHI, KIGS. 6, 7 ; AND PLATE LXXJCVU, FI«. H.

Mytilus jihrUtriatiix, White and Whitfield. Prnc. Boston Soc. Nat. Hist., vol. viii, p. 296. Kd,., 1SC2.
" WhnfiehUann.t. Wi.vcuell. Proc. Acad. Nat. Sci., Phila., p. 413. Sept., 1862.

p. 11. 1S63.
Mytilarca fibristriata, (W. .-iiid W.). Hali,. Prolim. Notice, L.im. Shells, etc., pt. 2. p. 24. 1869.

" JihH.itriafa (W. and W.) {fimhristriata. in error), Hai.i,. Pal. N. T.. vol. v, jit. 1. Plates and

Kxplanatinn.'s : PI. 33. fi^'S. 6, 7. .Inn., 1883.

Shell of medium size; body very elongate, luirrow elliptical; length more
than twice the height ; byssal area convex and inflated : ventral margin
nearly straight for two-thirds the length, thence curving into the abruptly
rounded posterior extremity ; dorsal margin very gently curved to the
extremity of the hinge-line.

Valves equal, moderately convex in the posterior part, becoming gibbous
in the middle and anterior.

Hinge-line short, oblique. Beaks narrow, sub-erect, rmbonnl region
narrowly gibbous.

Test thin, marked liy fine, tiiread-like, uudidatiug radii, whii-h are
more or less interrupted ly the fine concentric stria?.

Interior unknown.

A specimen has a length of 48 mm., and height 'I'l nun.

This species is distinguished from M. occidmtalis by its lesser gibbosity ; the
convexity of the body is along the ventral side instead of the median line ;
and by the presence of undulating, filamentous radii.

Formation and locality. In the Yellow sandstones at Burlington. lo\va.

LAMELLIBRANCHIATA. 265

GOSSELETTIA, Barrois.

GOSSELETTIA TRIQTJETRA.

PLATE XXXI, FIGS. 9-17; AND PL \TE LXXXVII, FIG. 1-2.

Pterlnea trlqueter, Coxrad. Geolog. Surv. N. Y. : Ann. Rept., p. 116. 1S3S.
Mytilarca ti'iquder (Conrad), .Hall. Prelim. Notice Lam. Shells, etc., p. 22. ISfiO.

Gfo.f.^elettia triqiicti-a ((.'oxrad). Hall. Pal. N. Y., vol. v. i)t. 1. Plates ami Explanatiims : PL 31,

Hfi's. 1)-17. .Jan., 1SS3.

Shell of medium to largL' size ; both' triangular, oblique ; in young shells the
height and length are nearly equal, in older shells becoming more elongate ;
anterior margin truncate, flattened on the ventral side; posterior margin
broadly rounded.

Valves equal, very convex, sub-angularly gibbous along the ventral side.
The convexity or breadth of the closed valves is about equal to the height
of the shell. Ventral side vertical. Dorsal side sloping very abruptly in
young individuals, and less abruptly in older shells.

Hinge-line straight, nearly or quite equalling the height of the shell.
Beaks anterior, strong, elevated and incurved.

Test thick, marked by fine concentric lines of growth which are crowded
and much elevated on the anterior side. In older specimens the stritB
become irregula-r and lauiellose toward the basal margin.

Ligamental area comparatively wide and very finely striated longitudinally.
Cardinal teeth three, strong and somewhat diverging. Lateral teeth elongate
and extending nearly to the posterior extremity of the hinge-line. The
anterior muscular scar is sub-circular, deep, situated near the inner border of
the cardinal plate and truncating the anterior cardinal tooth.

A medium-sized specimen has a length of 58 mm., height 4o mm., breadth
41 mm. A larger individual has a length of 80 mm. and height 55 mm.

The older shells present some similarity to M. {Plethomytilus) oviformis, but the
ventral angular slope is characteristic. In young specimens the triangular and
extremely gibbous form distinguish it from all other species here described.
34

266 PALEONTOLOGY OF NEW YORK.

It is referred to the genus Gosselettia of Barrois, from the Devonian of
Spain, on account of its similarity of external form and the strong cardinal
teeth ; otherwise it has all the characters of Mytilarca.

Formation and localities. In the shales of the Hamilton group, Fultonham,
Schoharie county, and Onondaga county, N. Y.

Gosselettia retdsa.

PLATE XJiXIII, KIGs, 1, '
Oosselettia retitxa. Hai.i,. Pal. N. Y.. vol. v, i>t. 1. Plates ami Explanations: PI. 30. tif^s. 1. 2. Jan., 1883.

Shell of medium size ; body very oblique, rhomboid-ovate, sub-arcuate ; length
one-third greater than tlu- lunglit ; ventral margin nearly straight for two-
thirds of the length, inflated at the b3^ssal opening and concave below,
thence abruptly curving into the broad basal and dorsal mai-gin.

Valves equal, regularly convex in the posterior part and gibbous in the
umbonal region ; the point of greatest convexity is above the middle.
The ventral umbonal slope is sub-angular. Ventral side flat.

Hinge-line short. Beaks acute, prominent, directed a little forward and
incurved.

Test of moderate thickness, marked b^- lamellose concentric lines of
growth which at irregular distances are crowded into fascicles.

Ligamental area and interior unknown.

The specimen de.scril)e(l has a lengtli of 49 mm., beiglit 32 mm., breadth
30 mm.

This species differs from G. triquetra in its proportionally longer form, which
is less expanded posteriorly ; hinge-line shorter and less oblique to the body of
the .shell ; and the ventral umbonal slope is less angular along the length.

Formation and locality. In the Hamilton group. Eighteen mile creek, Erie
county, N. Y.

LAMELLIBRANCHIATA. 267

M 0 D I 0 L A , Lamarck,
Sub-Genus MYTILOPS, Hall.

MODIOLA (MyTILOPS) PRjECEDENS.

PLATE XXXIII, FIGS. 9-18

Modiola prmcedens. Hall. Pi-elim. Notice of the Lam. Shells, etc., pt. 2, p. 1. 1869.

Mytilops (Miidi(ila) prwcede.nn. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Exjilanations ; PI. 33. fig-s. 9-18.

Jan., 1883.

Shell of medium size ; body elongate, semi-elleptical, broadly and obtusely
sub-triangular ; length a little more than twice the height ; byssal margin
slightly sinuate ; anterior end compressed, abruptly rounded, nearly straight
or gently curving along the ventral side, acutely recurved at the posterior
extremity, thence broadly rounded to the extremity of the hinge.

Valves equal, convex below, becoming gibbous and angular anteriorly.
The line of greatest convexity extends from the beak to the post- ventral
extremity, slightly arcuate.

Hinge-line slightly arcuate, sub-alate ; length nearly half the length of
the valve. Beaks small, sub-terminal, slightly incurved.

Test marked by fine, equal, concentric striaB, and by tine, wrinkled radii,
which diverge along the median line and curve toward the opposite margins.

Ligamental area with one or two longitudinal grooves.

Interior unknown.

A small specimen has a length of 28 mm., and height 12 mm. A medium-
sized specimen has a length of 36 mm., and height 17 mm.

Formation and localities. In a conglomerate of the Chemung group, Port-
ville, Alleghany county, N. Y., and south-east of Smethport, Pa.

268 PALjEONTOLOGY OF NEW YORK.

MmilOLA (MVTILOPS) MKTKLLA.

I'l.ATE XXXIII, I'lGS. ■-'3,24; AXI. IM. ATK I.XXXMl, Klti li

Modiola iiutclla, IIai.l. Prelim. Nolii'o Lain. Hhp\U. etc., jit. 2, i>. 1. IWiO.

ilytiUqts (Mo(liolu) iip:tcll,i. Hall. P:il. N. Y.. vol. v, pt. I. Pl.itrs :un\ Kxi>lanatioiis: PI. :!:!. i\-s~. -':!. -.'I

Jan.. 1SS:J.

SuELi. large ; body naiTow elliptical, sub-arcuate, ol)li<iuely truncate on the
anterior dorsal side; length more than twice tiie height; ventral margin
gentl\- curving, nearly straight for three-luurths of the length, thence
abruptly rounded at the posterior extremity ; dorsal margin very gently
curving to the extremity of the hinge-line.

Valves equal, depressed-convex at the posterior end, becoming gradually
more convex to a point anterior to tlie middle of the length, and gibbous in
the umbonal region.

Hinge-line obli(iae, about ecpial to the iieiglit of the valve. Beaks small,
appressed.

Test thin, marked b}- concentric striae.

Liscamental area marked bv two slender grooves. Other interior characters
unknown.

A specimen has a length ol' -"tT mm., height 2o mm., and hinge-line 24 mm.

This species dift'ers from M. prcecedens in its larger form, which is less
expanded posteriorly, less angular and gibbous along the umbonal slope, and
without radii on tiie surface so far as can be determined in the specimens.

Formation and localities. In a conglomerate of the ('luMuung grouj). at
Panama, and in a liouliler of similar rock on tiie road from Ellington to Cherry
cieek, Chautauqua county, N. Y., and at Warren, Pa.

Plates 11 and 13 Missing.

PLATES AND EXPLANATIONS.

PLATE I.

AviCULOPJiCTEX ClEON.

PajTC e.
Fig-. 1. 'I'l).- left valve of tlie specimen descviheii. The specimen is not so nearly entire as represented
in the H^jiirt*.

Uppt-r llil.lerberggTOup. Columbus, Ohio.

AviCDLOPECTEN IGNOTUS.
I'age 33.
Fig. a. A left vah e, fi-iiin. which the shell ha-s been almo-it entirely exfoliate.!.
Upper Helderberg- group. Near Victor, Ontarw Co.. iV. Y.

AVICULOPECTEN (PtEUINOPECTEN?) TEKMI.NALIS.
Page 32.
Fig-. 3. A left valve enlai-ifccl to two iliametei-s.

Upper Jlr-lilerberg group. lVUiiam.iviUe, Erie Co., N. Y.

Ptekixopecten insons.

I'age 59.
Pig. 4. The exfoliated left \aUe described, enlarged to two diametei-s.
Upper Helderberg groii]!. Western N. Y.

Lyriopecten Daku.^nus.

Page 41.
Fig. 5 A view of an in.perfect left valve, taken from a gutta-percha impression of the natural mould.
The si)ecimen is more e.\ten<leil on the anterior side than is i-epresented in the figure, and
there is an intermediate set of finer ray.s, also, not shown.
Upper Hehlerborg group. Le Itoij, N. Y.

I'XERIXOl'ECTEN MULTII! ADIATU.S.

l*afire 57
Fig. 0. The left valve de.sciii.ed.

Fig. 7. A view of the impression left in th(' matrix.

ri>|ier Helderberg group. Stafford, Geiiesee Co.. N. Y.

AVICULOPECTEN INSIGNIS.
Pago U.
See Plates 3 and 81 .
Fig. S. An iinpeifect left valve. enlarg('d to two diamntei-s.

Hamilton group. Stiiford, Genesee Co., N. Y.

AVICULOPECTEN PECTENIIOKMIS.

Fig. y. Tlie original .s|>ei!ifuen descrilu'd.

Ujiper Helilerberg gi-oup. Schoharie. N. Y.

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PLATE I— Continued.

AVICULOPECTEN PEINCEPS.

Page 1.
See Plates 5, e, 24 and 81.
Fig:. 10. A left valve.

Upper Helderberg group. Falls of the Ohio.
Fig. 11. A larger left valve of this species. The hinge-line should be represented as straight.
Upper Helderberg group. Bearffrass creek, Ky.

Pterinopecten dignatus.

Page 6-.'.
Fig. 12. A left valve, enlarged to two diameters, showing the form and surface characters.
Fig. 14. A specimen retaining both valves, enlarged to two diameters, showing their compai'ati\e form and
surface oniamentation. The anterior ear of the right val\e hiis much strongei- rays than
represented.
Fig. 15. An imperfect left valve, natiu'al size.

Marcellus shale. Blonmfield, Onlariu Co., N. Y.

Ptekinopecten l^tus.

Page 63.
Fig. 13. The left valve of the specimen described, X 2. The umbo shoidd be represented as free from
radii, and concentrically wrinkled.

Marcellus shale. BloomfieUl, Ontario Co., N. Y.

Pterinopecten exfoliatus.

Page 61.
See Plate 83.
Fig. 1(5. A medium sized left valve of this species.

Limestone of the Marcellus shale. Avon, N. Y.
Fig. 17. A large left valve, with the test more exfoliated than the pi'eceding. ^

Limestone of the Marcellus shale. Vimma, Ontario Co., N. Y.

Aviculopeoten (Pterinopecten ?) invalidus.

Page 31.
See Plate 82.
Fig. 18. A left valve, X 2. Hg. 21, plate 82, gives a more entire outline of this species and of the natural
size.

Marcellus shale. Cherry Valley, iV. Y.

PLATE II.
Lyriopecten interkadiatus.

Page U.
See Plate 82.
Fiir. 1. A small loft valvp.
Fifr. 2. A .'ipocimoii nf mpdiiim size.

Fiy. S. Th<,' i-ifrht valvp ticlonfriiif; to thi- l«ft valvp. tig-. 1.
KifT. 4. The right valve nf tiff. 2.

Hamilton gTuup. Piiltonham, fichoharieCo.. N. Y.

AviCL'LOPECTEN BELLCS.
Page 36.
See Plate 81.
Fi}.'. .1. A .-(mail left valve. X 2.
Fijj. K. A similar left valve, X 2.

Fig-. ;». A .ipHi-iiiiHii ))reserviiifr I'oth valves, showing their i-om|iavalive form and relations, X i-
Hamilton jrrouii. Xear Belloiia, N. Y.

AviCULOPECTEN ORNATUS.

Page .37.

See Plate 3.

Fifr. 7. A small .speiiinen piv.serviiifr liolh valves sligrhtly (lisplactcil, and the right one imperfect :

showinfT the form and ornamentation, X ''■
Fijr. 8. .\ larger specimen, similai- to the iirecediiig, bnt with the sui-faee charactei'S partially obliterateil
from maceration, X -■

Hamilton gronp. Caviiiid-aifftta hike. X. Y.

l^TERINOPECTEN UXDOSUS.
I'age 72.
.See Plate S2.
Fig. 10. A small Ifft valvi-, showing tlic! great proportional length of hinge-line in the young .shell.

Hamilton group. Cuitaiidaigua lake. N. Y.
Fig. U. A large left valve, U;iviiig very distant eipial radii.

Hiimilton gi'ouj). Bethany, N. Y.
I"'ig. 12. A i-ight valvi', showing numerous concentric undulations.

Hamilton group. CaiuiiKlaigua lake. N. Y.
Fig. i:-!. .\ right valve preserving two strong undulations in the nndioinil regimi, nior.' snliducd concentric
lines l>elow, and numerous tine radii.

Corniferous limestone. Claniice HuUmc, xV. Y.
Fig. H. A right valve preserving a jiortion of the test on the upper anterior side and jinterior ear.

Hamilton gronp. 1'aiiandaiyim lake, N. Y.
Fig. l.T. .\ characteristii' right valve.
Fig. Hi. .K large nght valve, showing numerous concentric undulations.

Hamilton group. CaHandaigiM lake, N. Y.
Fig. 17. A small specimen preserving both valves and showing strong undulations.

Hamilton group. Caitaiidatyna lake. jY. Y.
Figs. IS. 19. Two nearly entire large left valves.

Hamilton gj-oup. Oeneseo. TAvingston Co.. N. Y.

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PLATE III.

AVICULOPECTEN IdAS.
Page 13.

See Plate 24.
Fig. 1. A small right valve.

Hamilton group. Fultoiiham. Schoharie Cu., N. F.
Fig. 2. A larger example of more nearly normal proportions.

Hamilton gi-oup. Darlen, N. T.

AviCULOPECTEN SCABRIDUS.

Page 7.
Fig. 3. A young indi\'idual, apparently, of this species, slightly narrowed by compression.

Hamilton group. Bellona, N. Y.
Fig. 4. A left valve with the surface nuich distorted. Ijut preserving a very perfect outline.

Hamilton gronji. Canaudaigua lake. N. T.
Fig. 5. The cai-dinal portion of a right valve.

Hamilton group. Schoharie Co., N. Y.
Fig. 6. A left valve of medium size ; imperfect at the cardinal extremities.

Hamilton group. Delphi Falls, N. Y.
Fig. 7. An imperfect right valve preserving the surface characters of the ears, as obtained from the

matrix after the removal of the specimen.
Fig. 8. An enlargement from the surface of a specimen preserving the test.

Hamilton group. Cfeneseo, Livingston Co., N. Y.
Fig. 9. An enlarg-ement of the surface of specimen, fig. 7, taken from the middle of the valve.
Fig. 10. A large left valve presei'ving a very perfect outline, with a portion of the test adhering to the lowei-
anterior poi'tion.

Hamilton grouii. Bellona, N. Y.
Pig. 11. An enlargement of a portion of the test of the preceding si^ecimen.
Fig. 12. An enlai'gement fi-om the surface of a specimen denuded of the test.

Hamilton group. Crooked lake outlet, N. Y.

PLATE m— Continued.

AVICULOPECTEN INSIGNIS.

Page 34.

See Plates 1 and 81.

Fi{r. 13. The interior of a right valve imbedded in shale, showing the ornamentation a.< it ajipears on the

interior of the shell.

Hamilton group. Hamburg, Srie Co., N. Y.

AviCULOPECTEN ORNATUS.
Page 37.
See Plate 2.
Fifr. 14. 'I"he interior of a left valve imbedded in shale, X 2.

Hamilton group. CaiiawUiif/ua lake, N. Y.

AviCULOPECTEN MUCRONATUS.
Page 38.
Fig. 15. The interior of a left valve imbedded in shale.

Hamilton group. Dresden, Yates Co., N. Y.

AviCULOPECTEN LAUTUS.
Page U.
See Plate 81.
Fig. 16. 'ITie interior of two attached valves imbedded in shale, showing their comparative form and pro-
portions.

Hamilton group. West BloomJUld, N. Y.
Fig. 17. ITie interior of a left valve preserved a.s the preceding. Another figin-e of this specimen is given
on plate 81, fig. 5, taken from an impression of this mould.

H.TKiiltiin n-roii].. York Centre, Livingston Co., N. Y.

AviCULOPECTEN EXACUTUS.

Page S.
Fig. 18. 'ITie interior of ii left valve imbedded in shale.

Hamilton group. Hamburg, Erie Co., N. Y.
Fig. 10. A small left valve with the anterior ear imperfect.

Hamilton group. Canandaigua lake, N. Y.
Fig. 20. A large impei'fect left valve. The beak is represented as too acute, and the concentric lamella'
are not shown an on the specimen.

Hamilton group. Hamburg, Erie Co., N. Y.
Fig. 21. A left valve deiuided of the test. The .specimen shows the pallial line and muscular impression.

as described in the text.
Fig. 22. 'I'he upper portion of a right valve preserving the test.
Hamilton gi-oup. Hamburg, Erie Co., N. Y.

Paleontology NY.Vol V,

( PKCTIXID,£ )

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PLATE IV.
Lyriopecten parallelodontus.

Page 40.
Fiij. 1. The extenor f>f an imperfect i-iK-ht valve, as ohtaineil fmm an impression of the exterior of the

shell in the mati-ix. The sinus in the margin of the posterior ear is represented as too deep.
Fig-. 2. 'ITie interior mould of the preceding valve, .showing the ligamental grooves. The specimen also
preserves traces of the jiallial lim: and muscular impression.
Schoharie grit. Alhany Co., N. T.

Lyriopecten orbiculatus.

Page i-2.
See Plate 82.
Fig. 3. The interior of a small left valve imbedded in shale, showing a very perfect outline.

Hamilton gi-oup. ffeiwseo, Livingston Co., N. Y.
Fig. 4. The exterior of an exfoliated left valve. This specimen is the original of fig. 1, p. 202, Geolog.
Rept. Fourth Dist. N. Y.

Encrinal limestone of the Hamilton group. Shore of Lake Erie. N. 7.
Fig. 5. A left valve preserving a portion of the cardinal area. The ligamental area in the specimen shows
several longitudinal grooves much stronger than represented ; the figure is aLso too narrow
and the anterior ear too obtuse.

Hamilton gi-oup. Baileytoum, iV. T.
Fig. C. A large left valve, showing the obliquity of the body consequent to age, ami the comjiaratively
short hinge-line, although the latter is represented as too short in the figure.
Hamilton gi'ou]). Moscow, N. Y.
Fig. 7. A portion of the ligamental area of the right valve of specimen X 3. showing the longitudinal
gi'Ooves, with a slight bending ovitward under the beak.

Hamilton group. York Centre, Livingatoii Co., N. Y.
Fig. S. A large left valve j)reserving sonie portions of the test, and otherwise quite imperfect from mace-
ration and exfoliation.

Hamilton group. CanandaigtM lake, N. T.

Lyriopecten macrodontus.

Page 46.
See Plate 8.
Fig. 9. A large imperfect mould of the interior, showing the coai-se grooves of the ligamental ai'ea.
The muscular impression is preserv<!<l in the s|iecimen, but is not i-epi-esented in the figin-e.
Hamilton group. IVorcester, Otiego Co., N Y.

Lyriopecten anomijEformis.

Page 63.
See Plates 10 and 82.
Fig. 10. An impei-fect right valve, showing a portion of the hinge area and the deep byssal sinus. The
I'ays, as represented, are too strong ; they should be fine, undulating and vmequal in size.
Chemung group. Chemung river. Upper Narrows, N. Y.

Lyriopecten tricostatds.

Page 48.
See Plates 7 and 10.

Fig. 11. .\n imperfect left valve. By a fault in the lithography, the secondary and tertiary rays are
represented too nearly alike, instead of alternating in size and strength.
Hamilton group. Near Summit, Scholtarie Co., N. Y.

( PF.CTIN'ID.K, )

Palaeontology NYVol V.

Plate W.

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PLATE V.

Ptkrinopecten Vertumnus.

Page 71.

See Plate 83.

Fiffs. 1-6. Lpft valves of various sizes, showing slight variations in outline, anil considerable variation in

thp numbpr and strength of the rays.
Fig. 7. A small right valve. The l)ys.«al .sinus is not represented sufficiently deep

Fig. 8. A .snei-imen pre.serviiig both valves, showing their comparative form ami surfai-e ornamentation.
Hamilton grouji. f^chohark Co., iV. Y.

AviCDT,OPECTEX FASCICULATUS.
Page 11. '
See Plate 81.
Figs. 9, 10. Two small left valves.

Hamilton group. Pultonham. Svhoharie Co , N. Y.
Fig. 1 1. A left valve. Another figure of this specimen is given on plate 81, fig. 3, showing the concentric
striiP.

Hamilton grouji. CoxtMon. Ontario Co., X Y.
Fig. 12. A left valve which is much produceil ]>o.steriorly. The spi-eimeM is imi>ei-feit at the bi^ak. and is
restored in the figure.

Hamilton group. Fulto^ihaiii, Schoharie Co.. N. Y.
Fig. 13 An imperfect left valve, showing sti-ong faseicles of I'adiating .stria'.
Figs. 14, 15. Two large left valve.s, with simple thread-like stria- ornamenting the sui-face.
Fig. IK. A small light valve of this species

Hamilton group. Schoharie Co.. N. Y.
Fig. 17. A left valve presenting gi-eat irregularities in the radii, due to accident and intei'mittent growth.
Hamilton group. Cazemmla, N. Y.

AVICULOPECTEN PRINCEPS.

Page 1.
See Plates 1, 6. 24 anil 81.
F"ig. 18. A small left vahe preserving a portion of the test.

Hamilton gronp. Canundaigtia lake. N. Y.
Fig. 19. A portion of the test enlarged, showing the surface ornamentation.
Fig. 23. An irapei-fect left valve.

Hamilton group. Western iV. Y.
Fig. 24. .\n entire and characteristic right valve.

Hamilton grouii. Cazenavia, N. 1'.

AVICCLOPECTEN FORMIO.

Page 9.
Fig. 20. An iin]ierfeit left valve of the .species. The margins of both ears are represented as too concave
in the figure.

Hamilton group. Fultonhain, Schoharie Co., N. Y.
Fig. 21. .\ .smaller s|lecinl(^n retaining both valves.

Hamilton gTou]i. Madison Co., N. Y.

AviCULOPECTEN PhORCUS.

I'ngc 10.
Fig. 22. A left valve preserving a nearly entire outline.

Hamilton grou)i. Sctwharie Co., iV. Y.

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PLATE VI.

AVICULOPKCTEN PKINCEPS.
rage 1.
See Plates 1, 5, 24 anJ 81.
Fig-. 1. A large loft valve, much extended posteriorly.

Hamilton group. Seneca lake, N. T.
Fig. 2. The impression of the exterior of a large right valve, showing the ligaraental area. The spot near
the middle of the valve has been caused by the attachment of a Crania to the exterior of the
shell. Hamilton group. Hamilton, N. ¥.
Fig. 3. An impression of the interior of a right valve. The striated ligamental area is shown in the
specimen, but not represented in the tigui'e.

Hamilton group. Hamilton, Madison Co., N. Y.
Fig. 4. An imperfect left valve.

Fig. 5. The right valve attached to the preceding, showing the comparative size and ornamentation.
Fig. 6. A small oblique left valve. The hinge-line should be represented as straight, and with a strong

ligamental area.
Fig. 7. A sjiecimen presei'ving both valves.

Hamilton group. Borodino, N. Y.
Fig. 8. A left valve, showing the ordinary characters of the species. The ligamental area is preserved
in the specimen, but not here i-epresentcd, and the hinge-line is too short in the figure. This
valve is associated with, and probably belonged to the right valve shown in figure 3.
Hamilton group. Hamilton, N. Y.
Fig. 9. An imperfect left valve.

Hamilton group. SkaneateUs lake, iV. Y.

a^MniLir : m sf © m m^ip .

Palaeontology NYVol V.

( PECTIXID.£.

Plate VI,

J H EmCTlon del

Kierr.anrJitlx

PLATE VII.

AVICULOPECTEN DUPLICATUS.

Page 17.
See Plate 81.
Fig. 1. An imperfect right valve.

Chemung group. Hobbieville. N. T.
Fig. 2. A left valve, which shows the prevailing charaoter of the species in ha\-ing the anterior side longer •
and more extended than the posterior. The original of the species.
Chemung gi-oup. PHUpsTjurg, Alleghany Co., iV. Y.
Fig. 3. A somewhat larger left valve.

Chemung gi-oup. Mockuille, Alleghany Co., N. T.
Fig. 4. The surface of a specimen enlarged to three diameters.

Chemung gi-oup. Rockmlle, iV. T.
Fig. 5. Aleftvalve. The outline of the figure is somewhat too high and too short, and liears an niniatural
resemblance to the succeeding species.

Chemung group. Rockville. N. T.
Fi"-. 6. A right valve. The figure represents the body too .short, the sti-i;e too sh.arp .and the beak too

obtuse.

Chemung group. East Randolph, N. T.

Fig. 7. A small left valve.

Chemung grouji. Jinckville. iV. Y.

AviCULOPECTEN RUG^STRIATUS.
Page 15.
See Plate 81.
Fi". 8. A small left valve nearly entii-e, showing the usual form of tlie s]>i>cies. ,

Chemung group. PhiUpslmrg, N. Y.
Fiu-. 9. A larger left valve of similar character to the preceding.
Fig. 10. An enlargement of the surface, showing the character of the ornanicnlatioii.
Fig. 11. A nearly entire right valve.

Chemung group. Rockmlle, jX. Y.

AviCULOPECTEN C.4NCELLATUS.

Page IS.
Fig. 12. A right valve, showing the usual form and proportions.

Chemung group. Phllipshnrg, N. Y.
Kg. 14. A right valve preserving the ears and surface markings in a very perfect condition.

Chemung group. Cotiewarigo, Cattaraugus Co., N. Y.
Fig. 15. An enlargement of the preceding specimen to two diameters.
Fig. 16. The interior impression of a right valve, with radii partially pnisevved.

Chemung group. Westfield, N. Y.
Fi"-. 17. An enlargement of a small right valve to two diameters.

Chemung grou]3. Conmmngo, N. Y.
Figs. 18, 19. A right valve, natural size and enlarged. The specimen is somewhat distorted from pressui'e,
and does not represent the normal form of the shell.

Chemung group. Rockville. N. Y.

AviCULOPECTEN ItYS.
Page 20.
Fig. 13. The right \alve described.

Chennmg group. Conewango, N. Y.

AviCULOPECTEN SQUAMA.
Page 27.
Fig. 20. A ritrht valve enlarged to two diameters, showing the form, ears and surface markings.
Chenuing group. Philipshurg, N. Y.

I'LAXK VII— €oiilinue<I

A VICULOPECTEX DOLABRIFOK.M is.
Pajje 26.
Kif.'. 21. A rifflit vnlve enlarged to two iliain«ters. The <*ai-s shoulil sbow, in the figure, rays similar t<i
those on the hoily of the valve. This figure is from the original sjiecinien of the specie.i.
Chemung grou)>. P/nUpxbiiry, N. Y.

AviCULOPEgXEN CONVEXUS.

I'agc 18.

l"i". 2'J. A left valve enhirgoil ti^ two ilianietei'S. Tlie anterioi- ear .shnnlil show a .slight sinus in the

margin for the byssns.
l'"ig. "JS. A iirolile of the i)i'ec(>(lingi showing the e.onvexity of the valve. (Original of tig. C, i>. 264, Geolog.
Rei>t. Fourth Dist. N. V.)

rheninng gron]i. lioehi'ilh, N. Y.

AVICULOPECTEN SIGNATUS.

Page 28.
Kiif. 24. A left valve I'olarged to two diameters, showing the form ami surface markings. (Origimtl of
fig. .i, p. 264, Geolog. Re|)t. Fourth Dist. N. Y.)
Chemung grou)). liorkville, N. Y.

Lyriopecten Polydorus.

Page 50.
Kig. 25. The left valve de.seribed. The byssal sinus shouhl Vje deepei- than reju-esented.
Chemung group. Ccumadaga, N. Y.

Lyriopecten tricostatis.

Page 4S.
See Plates 4 and 10.
Fig. 26. All enlargement to two diametei-s of a i)ortion of thi> siirfni-c> nf a spec-inien of this .species.
Clieinuiig gi-onji. ^ear Elmira, N. Y.

Aviculopecten tenuis.

Page 39.
See Plate SI.
Kijr. 27. .\ h'ft valve, showing tlu' form and siirfaee marking.*. The si)eeimen also .shows the muscular
inipressiiin and pallial line.

Chemung group. llinvUilph, jS'. Y.
Kig. 28. A larger s)ieeimeii of the sann\ AnotlnM- tigm-e is given on jilate 81, showing more clearly
the eharac.tei-s of the spei^es.

Cliemiiiig group. NeaiNalamaiun.JV. Y.

Aviculopecten celsus.

Page 23.
Figs. 2H. 30. \ light valve, natural size and enlarged.

Chemung grfiii]). Siilanmiiin, X. Y.

Aviculopecten ellipticus.

Page 2.').
Kig. 'i\. A nearly entire left valve of this species.

Chemung group. Meadmlle, Pa.

Aviculopecten patulus.

Page 24.
Fig. 32. A .small right valve as obtained from the inipivssion in thi' matrix. Tin' cats ai>' |iaitiall\
restored in the figure.

Chemung group. iSalamanca, jY. i'.
Fig. 33. A large left valve, .showing the characters of the shell as obtaineil from an im]iression in a tine
cong-lomerate. Thi^ hinge-line should be reju-eseuted as straight.
Chemung group. Near fialatnniica, jY. Y.

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Paleeontology NY.Vol V

( PECTiNin.f; )

Plate VTI.

J.H Emerton del

PLATE VIII.
Pterixopectex suborbicularis.

Page 80.
S.!e Plates 24 aiul 82.
Fig. 1. A nearly entire left valve. The rays are strong-Iy cronulateil in the sperimen ami ilo not bifurcate
n.s represented, but increase in number by intei-stitial a'Witidii.
Chemung' group. New Albion, Cattaraugux Co., N. Y.
¥\g. 'i. A view of another individual. (The original of fig. 1, p. 264, Geol. Rept. Fourth Dist. N. Y.)
Chemung 'group. Holhieville, N. Y.

Ptekinopectex crenicostatus.

Page 78.
See Plate 82. .
Fiji^. H. An im|>i>rfect left valve showing the crenulate rays.

rhemung- gi-onp. Coruneanrio, N. Y.
Fip. 4. A large left valve This specimen is re-ilr.'iwn on plate 82, tig. 14, and represents more fully the
form and surface ornamentation.

Chemung gronj). Angdica, N. Y.

Pterinopecten Neptunus.

Page 79.
Fig. .5. \ small left valve, imperfect on the post-cardinal margin.

Chemung group. Phitipsi/urg, N. Y.
Fig. fi. A large imperfect left valve.

Chemung group. Philipsbiirg, N. Y.
Fig. 7. An iinpei-fect right valve. The specimen is obscure and is erroneously repi-esented as a left
valve.

Chemimggrou|>. Angeliia, N. Y.

Lyriopecten magnificos.

Page.M.
Fig. 8. A large left valve obtained from an impression of the matrix. The ligamental area should be
represented as longitudinally striate near the beak.
Chemung gTOU|). 3Ii»itro,ie. Pii.

Lyriopecten macrodontus.

Page 46.
See Plate 4.
Fig. 0. A left \ahe, incorrectly represented as nearly circular, although in the specimen it corresponds
in form with tig. 10. 'Hie ligamentid area is also shown in the specimen.
Hamilton group. Hamilton, iV. Y.
Fig. 10. A large left valve. The anterior margin is restored in the figure.
Hamilton group. Hnmilton, N. Y.

EnnEiMnnrKa"© ©mmwiF.

Paleontology NYVolV

(PECTIXID^E. )

Plate 'M

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Ph:L4st.lith

PLATE IX.

Crenipecten Winchelli.

Page 89.
Figs. 1, 2, 4. Small rig-ht valves showing the form of this valve and the obsolescent surface markings.
Figs. 25, 26, 27. Three left valves. Fig. 25 incorrectly represents the specimen as having the form of a
light valve. The beak should turn slightly toward the left and the posterior margin
should be more extended.
Fig. 28. The upper portion of a left valve, enlarged to two dianieter.s, showing the form and surface

characters of the ears, and the tran.sverse ligamental grooves or cartilage pits.
Fig. 29. An enlargement of the surface as obtained from au impression taken in the natural mould of the

exteiior.
Fig. 30. An enlargement as shown in an impression of the exterior left in the matrix.
Waverly sandstoiie. Ntnoark. Ohio.

AVICULOPECTEN (CliENIPECTEN ?) INCULTUS.

Page oO.
Fig. 3. An impression of the interior of a right valve.
Chemung group. Glean, N. Y.

AviCULOPECTEN CaROLI.
Page 29.
Fig. 5. A partially exfoliated left valve.

Waverly sandstone. NewarTt, Ohio.

Crenipecten crenulatds.

V3.ee S'2.
Figs. 6-8. Three left valves varying somewhat in form and obUquity. i
Chemung group. Rockville, Alleghany Co., iV. Y.
Fig. m. A right \-alve showing the form of this N.ilve and the row of minute cartilage-pits along the hinge.
The posterior ear is not sufficiently extended in the figure.
Chemung group. Philipshii,rg, Alleghany Co., N. Y.
Fig. 16. A light valve. The posterior ear in the specimen is somewhat larger than represented.
Pig. 17. An enlargement, to two diameters, sho^ving the row of cartilage-pits along the hinge.
Chemung grouj:). Rockville, N. Y.

PLATE IX— Contiiined.

Crenipecten amplus.

Page 81.
Kif."-. !•. A li't't valvi- slmwiiiy tin- cjirtilag-e jiits aUniff the hiiifff. Tin- iKisteridi- eai- as rcpreseiiteil is too

loiifT. frivirifr till" fig'iire the aspec^t of the right valve.
Fij,'. ly. A lai'tre left valve. The tig-iire should be exteiuli'ii fully 3 mm. on the postenor side to correspond

with the sjiecimeii.
Fife', l."*. An imperfect specimen, somewhat dislcn-ted tVum pressuie, and referi-ed tn this species with some
doiil)t.

• 'hfiniiiiy frronp. MockvUle, jy. Y.

LVRIOPECTEN FASCIATUS.

Page 65.
Fi{r. 10. An imperfect left \ alve.

Fig. 11. An enlargement of a portion of the sui-face showing the fasciculate radii and concentric striae.
Chemung group. Leon, Cattwaiigjis Co., N. Y.

Crenipecten Leon.

Page 88.
Si'e Plate S3.
Fig. \2. \ left valve of this .s])ecies. .Vnother figure of this specimen is given on plate .n3 shnwirig mere
correctly the chara<:ters of the hinge and the form of the valve.
Cheuumg group. Leon, Cattaraugus Co.. N. Y.

Crenipecten impolitus.

Pace Si.
See Plate 83.
Fig. 14. A large left valve showing the form and pi'oportions of this species. The .spccinicji preseivcs
traces of distant ra<liating lines which are not represented in the tigui'e.
t'hemung group. Olean, N. Y.

Crenipecten obsoletus.

Page 84.
Figs. Kt, 21. Tjcft and right vahes. Fig. 21 is from the original specimen of the s])ecies.
Chemung group. PhiTtpshiirg. N. Y.

Crenipecten glabek.

P.ige 85.
Fig. 20. A view of the original .specimen of fig. 10, p. 264, Geolog. Rept. Fourth Dist. N. y. 1S43.
FMg. 22. A larger specimen referred with some doubt to this specimen.
Chemung group. Alleghany Co., N. Y.

Crenipecten micropterus.

Pago 88.
Fig. 23. .\ right valve .showing the foriu and surface characters.
Chemung group. P/iilipshurr/, iV. Y.

Crenipecten liratcs.

Page 87.
See Plate 83.
Fig. 24. A left valve. Another figure of this specimen is given on plate S3, to show the size of the eai"s as
preserved in the specimen.

Chemung group. East Randolph, N. Y.

PLATE XII.
Glyptodesma ekectum.

Page 153.

See Plates 11, 13, 25. 86 anil 87.
Fig. 1. \ left valve.

Hamilton group. Cazeitovia, N. Y.
Fii,'. 2. .\ view (if rig-ht valve showing pallial anil muscular imi>i-e.>«ions.

Hamilton group. C'azenoina, N. Y.
Kip. :i. A left valve jireserving strong, concentric, lamellose sui-face markings.

Hamilton group. Madison Co., N. Y.
Fig. 5. A small light valve jireserving the lateral teeth.

Hamilton group. Schoharie Co., N. Y.
Kig. fi. A very convex left valve. The radiating lines are represented too strongly in the tigui'e.

Hamilton group. Hamilton, Madison Co., N. Y.
Fig. 7. The right side of a cast showing a very distinct muscular scar and pallial line. The appai-ent
double impres.sion of the muscular scar is probably due to an irregular growth of this part
during its advancement.
Fig. 8. A \ cry large and erect left valve, with the cardinal angles much extended. It is of the form of

Avicula crufiformU, Conrad.
Fig. 9. A very large left valve with the test partially exfoliated.

Hamilton group. Jefferson, Schoharie Co., N. Y.

Glyptodesma erectum, v:ir. obliquum. .

I'age 155.
See Plate 13.
\'\\i. A. A small loft valve nearly complete in form and outline.
Hamilton giouji. Cnnandaigua lake, N. Y.

Paleontology NY Vol V

I PECTIXID^E. )

Pla^te IX,

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V'\g. 1. A li'ft \)il\(N showiiif; tin? tbi-iii uiiil siirfacp chiu-ai-tKi-s. The fijrnre should also show nunicrous Ktie

rays on the posterior ear.

Fiif. 2. A similar left valve, showing considerable variation in tlie siirf:i hai-arters, and strong- lijra

mental area with a central cartilage-pit.

Chi'inutii,' (."-ronp. FrTiiMhi, Delmmre Co., N. Y.

AVICULOPECTEN STRIATUS.
Page -22.
Fig. 3. A left valve ; the original of fig. 7, p. 264, Geolog. Rept. Fourth Dist. N. Y. 1843.
Fig. 4. An enlara-ement of the same, showing niorir distinctly tiie characters a.s dest^ribed.
Chemung group. Painted Post, ffteiihen. Co., N. Y.

LvKIOI'ECrEN ANO.\tI.EFOKMI8.

I'a^'e .IS
S..e Plates 4 ami 82.
Fig. .">. A left valve. This specimen is inoi-e correctly rei)resented on plate 82, tig. 2.
Chemung group. CliiniiiiKj mch. X. Y.

LyRIOI-ECTEN TKtCOSTATUS.

See Plates* 4 and 7.
Fig. li. An imjierfect left valve preserving a portion of the striated ligamental area and the cartilage pit.

Chemung grouj). Chemwiig Co., N. Y.
Fig. 7. A small left valve with the posterior side undeveloped from accident or natural deformity.

Chemung group. Near Hlmlra, N. Y.
Fig. 8. .\ lai-ge left valve, showing the byssal notch on the anterior side and the comparative size of the
anterior and posterior ears. The posterior ear in the sj)ecimen, shows several ol>.scnre rays
and the ligamental area is strongly striated.

Chemung group. Near Elmira, N. Y.
Fig. 9. A fragment of a large left valve ]5reser\nng a more extended posterior ear than usual. The

anterior ear is too much extended in the figure and should be represented as in tig. S.
Fig. 10. .\ l<-f't vaUe with a ])ortion broken away, showing what appeai-s to be thi' right \alve beneath.
The stronger radii should Ite continuous over the interval occupied by the other valve, and
the finer lines on that valve shoidd be of the .same chara('ter jus on the left valve.
Chemung group. Broome Co., N. Y.
Figs. 11, 12. Two small left valves representing the form and ornamentation of the shell at this period of
growth.

Chemung group. Chemung Co., N. Y.

(EIIIIgsfflI^rI^J© ©m^wiF.

I PECTIXID^K. )

PalseontologyNYVoiy.

Plate X.

J.H EmerLon del

IM.ATK XI.

(il.YrroDESMA F.KRCTUM.

Page IM.
See Plutes 12, 13, 25, 8t> and 87.
Fips. 1. 2. Two oppiisite valve.'i of the same iniliviiliuil. Vig. 2 sIkiws the nmsnilar scai- and alsn give.'!
the comparative elevation of the beak.s of the two valves. The left valve of the specimen
also shows the pallial line and niiiseidar impression, which ai'e not represented in the
ligure.
I'iir. ;>. A more entire left valve, haviiijf the eai-s but lilth'. extended.
I'iir. 4. A rig-ht valve having- the cardinal anjrles much produced.

Hamilton {rrouj). Fidtoiiham, Schoharie Co.. N. Y.
Fiff. "i. A smaller right valve, showing one of the obliijue lateral teeth.

Hamilton group. Cazeiiovia, JS. Y.
Kig. ti. A light valve, showing a iiroportionally gi-eater lireadtli. ami moderately extended cardinal

ex|pansions.
Fig. 7. A portion of a large left valve with very large canliu.al alations.

Hamilton gi'o\ij). MadiKnn Co., N. Y.
Fig. S. A left valve. Another figure of this .specimen is given on jilate 86. fig. IJ.

Hamilton grouji. Cazmwria, N. Y.
Fig. 9. A large left valve with short broad i-ardinal angles and unusual height. The im)iression of the

ligamental area is longitudinally striated.
Kig. 10. A left valve with the cardinal angles narrow and unusually extended. This form is the Avh-nla
cruciformis, Co.NRAn. Ann. Rep. ]?. .")4. 1S41. The specimen preserves the pallial line and
nuisrular inipressiim, which are not shown in tlii' figure.

S^MIIIILiriElM (Bmrn^BW

Palaeontology NY.VolV.

( AVICTLID.K .

Plate SI,

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PLATK XIV.
Pterinea flabella.

rage ii:i.
See Plates 15 and 83.
Fitr. 1. -V li't't valvi- (if a small siiofiiraeu of iiim-e than ii.«iial ohliqiiity.

Hamilton {ri-oup. Eastin-n N. 1'.
Fig. 2. The left valve of anothei- speeimen, ^ven to sIkjw the ai>pearance produceil by having- a portion
of the mavfrin and wing removed.

Hamilton group. Euateru N. Y.
Fi". 'i. A h'ft \alve of a well prewerveil specimen of medium size, showing the general form ami rhar-

aiitere. Hamilton group. BaMern N. Y.
Fig. 4. .\ left valve somewhat narrower than the preceding.

Hamilton group. PratVn Falls, Ommdaqa Co., N. Y.
Fig. f). A left valve having a broail body and extended ving.

Hamilton group. Tiilli/, JS'. Y.
Fig. G. A large imperfect s))eiMmen with an unusually Jarge wing.

Hamilton group, MililiKOil Co., S. Y.
Fig. 7. An impi-rfect left valve of nai-row, erect form, showing the striated ligamental area.

Hamilton group. fSkniK'nlelfx lake, J\'. Y.
Fig. 8. The left side of a sjiecimen from whii'h the shell has been removed leaving only the marks of the
stronger radii in the cast, a (-onnuou cooilition of the .sp.-cimens from the hard calcareous layers.
Hamilton group. Delphi, JX^. Y.
Figs. 9-13. A series of right valves ; figs. 10, 11 and 12 beingthe reverse of tigs. 2, 8 and 5, respectively.
Fig. 14. A profile view of the specimen figs. 8 and 11, showing the comparative depth of the valves.
Fig. 15. The internal moidd of a right valve, showing the anterior and po.steriiir ninsiular impressions,
the jiallial line with the cardinal and lateial teeth.

Hamilton group. Pratt'-i /allx, Onondaga Co.. N. Y.
Fig. 10. The interior tVom .'i gntta-percha mould, showing the form of the teeth and the uniscniar scars.
Figs. 17. IS. The vertical and cardinal views of a natural internal mould of a fragment of a left valve
showing the characters of the interioi-.

Hamilton gi-onp. Otiego Co., N. Y.
Fig. 1".<. The interior, as obtained from a gutta-percha impres,sion.
Fig. 20. The internal mould of a snniU left valve preserving the hinge chariicters ami mu.scniar scara.

Hamilton grouji. Ot.ttyu Co., iV. 1'.
Fig. 21. The inner surface of the carilinal portion of a left valve showing the ligamental ai-ea.
Hamilton group. Pratt'.i Falla, Onondaga Co., N. Y.

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'Palssoutolcny NYVolV

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PLATE X\'.
Ptekixea flabella.

Pnprc 93.

Sec Plntos 14 mid SS.
Fiif. 1. An iiii|)ci-f'oit Icl't valve.

Upper Heldei-liei-fi: lime-stone. Stafford, Gimtsee Ok, N. Y.
KifT. ■•. The internal moiilil of a siiiall left vahe, showing- the hing-e eharaetei-s and the museular
impressions.

Hamilton g-ronp. Ol.icgo Co., N. Y.
Fiff. 5. The interior a.s obtained from an impression in g-utta-peroha.
Kiir. t). A left \alve, haviiijir tlie wing unusually large and extremely extended.

Chemung group. Miuisfitld, Pa.
Fig, S. An enlargement of surface where the intermediate ra<lii ai'e nearly equal.

Fig. 9. An enlargement of surface showing the alternating small radii, and strong, concentric 1am-
ellose striffi.

Hamilton group. Skaneateles lake, N. T.
Fig. 10. An enlargement of a specimen preserved in calcareous shales, showing strong lamellae and very
unequal radii.

Hamilton group. Hainhurg, Erie Co., N. Y.
The weathering of .«pecimcns like the one rejiresented in Fig. 10 often obliterate.s the finer
surface ornamentation, and leaves the lai-ger rays with transverse ridges marking the place
of the stronger lamellae, giving them a nodose character. A specimen in this condition was
described by Mr. Conrad as Avicula tulevculata, with distant tuberculated ribs and interme-
diate strise. . . Ann. Rept. Geolog. Surv. N. Y., p. 117, 1838. This name should have
been cited in the sjTionomy of Avicula flabella, page 93 of this volume.

Pterinea pinguis.

Page 92.
See Plate 83.
Figs. 2, 3. Casts of two impei-fect left valves. The specimen fig. 2 is ro-drawn on plate 83, fig. 13, to show
the foi-m of the beak anil proportions of the valve.

Upper Helderberg gronj). Near Columbus, Ohio.

Pterinea dispanda.

Page 97.
Fig. 7. The left valve described, showing the foi-m and surfaire charactei-s.
Chemung group. Mansfl^ld, Pa.

Leiopteria Rafinesquii.

PagelGl.
See Plates 20 and 88.
Kig. 11. A'left valve, slightly imperfect at the extremity of the wing. The auricle is siiniewhal tiKi much
Hxtended in the figure.

I I iper Helderberg limestone. Dehncan: dliin.

(tI.VPTODE.^MA occidentale.

Page 157.
See Plate"86.
Kif;. 12. An inijierfect left valve. This specimen is better repi'esented on plate 8li, tig. H.
I'lijier Helderberg limestone. Fiitl.i of the Ohio.

IflJiM^lL-LCillltf ©Ji.DJiCriF.

PaleeontologyNYVolV.

( AVICI'LID-C . )

Plate TV

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PLATE XVI.

PtEKIN'EA CONSIMILIS.
Page 100.
See Plate 84.
Fig-. 1. A small right valve, showing the strong- radii on the wing and their absence over the body.
Pig-. 2. A larger right valve, imperfect at the posterior margin.
Fig. 8. An imperfect left valve, showing a very broad striated Ugamental area.

Chemung group. Ntar Elmira. iV. T.
Pig. 9. A similai- left valve of somewhat shorter form.

Chemung group. JVear Elmira, N. Y.
Fig.' 11. k left valve, .showing some irregularity in the concentric markings of the shell along the ven-
tral margin ; probably due to a natural irregularity in the growth of the shell.
Chemung gi-oup. iVertr Elmira, K. Y.

Pterinea Chemungensis.

Page 98.
See Plate 84.
Pig. 3. .A right valve, showing the form an<i surface ornamentation.

Chemung group. Chemung river. Upper Narrows, N. Y.
Pigs. 7, 10. Two left valves of very erect form.

Chemung group. Chemung JVarrows, N. Y.
Fig. 12. A left valve, more oV)lique than the preceiling.

Chemung group. Cliemung river. Upper Narrows, N. Y.

PlERINEA PROEA.
Page 103.
Fig. 4. An imperfect right valve. The specimen shows the pallial line and muscular scar.

Chemung group. ■ Near Elmira, N. Y.
Fig. 13. The right side of a specimen preserving a part of the right valve Ijing in the impression of
the left one.

Chemung group. Near Elmira, N. Y.
Fig. 14. An inipre.s.sion of a right valve, retaining a portion of the left valve around the pallial margin.s.

Pterinea rigida.

Page 101.
Figs.JS, 6. Two left valves, showing the characteristic form and ornamentation of the si>ei"ies.
Chemung group. Chemung Co., N. Y.'

smiESv^^Drsf© ©iP.iffiwiF.

Palaeontology NYVoiy^

( AVICXTLID.-E . )

Plate XVI.

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PLATE XVII.

ACTINOPTERIA MURICATA.

Page 1C8.

Fig. 1. A small left valve sliowinsf the extent of the wing-, X 2. The .surface of the wing .should show

several fine radii.
Fig. 2. A larger left valve, X 2. The extremity of the wing is not sufficiently extended in the figure, and

the surface has fine radii which ai'e not represented.
Fig. 3. A left valve preserving- the mucronate extensions of the radii along the ventral margin, X 2.
Marcelhis shale. Littleville, Livingston Co., N. Y.

ACTINOPTERIA DOEIS.

Va.ee 109.
Fig. 4. A left valve of this species, enlarged to two diameters.
Marcelhis shale. East Bloomfield, N. Y.

LeIOPTERIA LvEVIS.

Page 158.
See Plate 20.

Figs. 5, (i. Two right valves, X 2. Fig. G is incoi-rectly restored on the ventral margin and the wing.
Figs. 7-11. Left valves showing the prevailing characters of the species, X 2.
Marcelhis shale. Livingston and .EHe counties, iV". Y.

Leptodesma Marcellense.

Page 175.
Fig 12. The left \-alve described, X 2.

Marcellus shsde. Hast Bloomfield, N. Y.

Pterinopecte.v Hermes.

Page (14.
Fig. 13. A small left viilve. The extremity of the ear i.-* represented too acute and the pallial margin is
reflexed in the specimen.

Hamilton group. Canandaigua lake, JV. Y.
Fig. 14. A larger left valve.

Hamilton g-roui). Ontario Co , JV. Y.
Fig. 15. The interior of a left valve.

Hamilton group. Caiimulaiyua lake, N. Y.

I'l.ATE XVII— Contitiueil

Pterinopecten spondylus.

Page Go.
Fif.'. 111. The interior of a left valve showing the spinous processes of tlie rays projecting' from tho pallial
niarg-in. enlarged to two diametei-s.

, Hamilton group. CanandaigJM lake, N. T.

Pterinopecten conspectus.

Page 06.
Fig. 17. The exterior of an imperfect right valve as obtained from a gutta-percha cast of the natural mould.

Hamilton group. Skancateles lake, N. T.
Fig. 1§. An exfoliated left valve.

Hamilton group. Skaneateles lake, N. T.
Fig. 20. A specimen i)reserving the fine intermediate rays of the test.

Hamilton group. Darien, Genenee Co., N. Y.
Fig. 21. A left valve with the test removed. The ear is represented as too oblique in the figure.

Hamilton group. Skanratele.^ lake. N. Y.

Pterinopecten inteumedius.

Page 63.
See Plate 83. •
Fig. 19. A left valve enlarged to two diameters.

Hamilton group. Cayuga lake, N. Y,

Pterinopecten fiijtextus.

Page G7.
See Plate 82.
Fig. 22. A right \alve pi-esei-ving the test and showing the form of this valve.

Hamilton group. From a bottlder. Pine Valley, Chemung Co.. A'. Y.

Actinopteria subdecussata.

Page no.

See Plate 10.
Fig. 23. A small left valve.
Fig. 25. A somewhat larger example.

Fig. 26. An individual of medium size showing the foi-m and surface markings.

Pig. 27. A left valve, a large portion of which is broken away, showing the interior of the right valve.
Fig. 29. A large left valve.

Fig. iiO. A i-ight valve .showing a greater extent of the wing than in the opposite valve.
Fig. HI. A s]iecimcn of medium .size, showing the interior of the left valve occupied by a portion of the
right, and rejn-e.senting the difference in the strength of the surface markings on the two
v;dves.

Hamilton group. All from CauamUiigua hiki, r.vcrpl fir/. 2'? whir/i is from lielloiia.
Yates Co.. N. Y.

ACTIX( MTI'.KI.V DECUSSATA.

Pago 111.

See Plate.'* 18, 20 and 84.
Fig. '24. A .'imall left valve.

Hamilton group. Dresdtn, Yates Co., N. Y.
Fig. 28. .\ large left vuUr with the test removed, showing the usual form of the shell.

Hamilton group, ('iiiirwddlf/nn lake. iV". Y.

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PLATE XVIII.

ACTINOPTEUIA DECUSSATA.
Page lU.
See Plates 17, 20 and 84.
I'ig-. 1. .\ liiiiri' right valve, preserving' the lamella; of the test.

Encrinal limestone of the Hamilton g-roup. Eighteen Mile creek, N. Y.
Fig. 2. The right valve of a specimen preserving both valves. The left valve is repi-esented in tig. 9.

Hamilton group. York, Limnystoji Co., N. Y.
Fig. 3. A right \alve. The specimen ijreserves several rays on the wing which are not i-epresented in
the tigurc.

Hiunilton group. Geneseo, Livingston Co., N. Y.
Fig 4. A .small right valve showing the radii on the wing.

Hamilton group. Ontario Co., N. Y.
Fig. 5. A small left valve.

Hamilton groui>. Caiiandaigua lake, N. Y.
Fig. 6. The left valve of the specimen, fig. 4.
Fig. 7. A left valve preserving a portion of the test on the anterior eml.

Hamilton group. Livingston Co., iV. Y.
Fig. 8. A ca.st of a left valve.

Eucriiial limestone of the Hamilton group. Eighteen Mile creek, N. Y.
Fig. 9. The left valve of the specimen tig. 2.
Fig. 10. A left valve showing vei-y fine surface radii.

Hamilton group. York, Livingston Co., N. Y.
Fig. 11. A similar specimen of more elongate form.

Hamilton group. Bellona, Yates Co., N. Y.
Fig. 12. A large left valve preserving the greater portion of the test.

Encrinal limestone of the Hamilton group. Eighteen Mile rreek, Erie Co., iV. Y.
Fig. 13. .\ left vahe enlarged to two diameters showing the characters fif surface in a well-preserved

specimen.
Fig. 14. A farther enlargement of the surface, to show the elevated lamellat and the mode of increase of the

i-adii.
Fig. 15. Cardinal view of a specimen jjreserving both valves partly opened.

Hamilton group. York, Livingston Co., N. Y.

( AVlri'LlD.« 1

Palaeontology NY.VolV,

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Plate XVni

iti-itiiiff <--/ t S-\F r'y^£T J rj^i

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PLATE XIX.
LEiorrERiA Dekayi.

Pago 164.
See Plate-s 20 and 88.
Vig. 1. .\ .small left valve. The specimen shows no imlieations of rays such a.s are represented in tin-
fignre. Hamilton gi-oup. C'ooperstown, N. T.

ACTINOPTEKIA BOYDI.

Page 11.1.
See Plate 84.
Fi(js. 2, 3. Two left valves preserving the surface onianientation.

Hamilton group. Schoharie Co., N. Y.
Fig. 4. A left valve.
Fig. "). A small left valve.

Hamilton group. Jefferaon, Schoharie Co., N. Y.
Fig. <>. A right valve with an unusually extended wing.

Hamilton group. Fnltonham, Schoharie Co., N. Y.
Fig. 7. The exterior of a right valve, as obtained from a gutta-perrha inlln■L■^•^i(>rl of the natural monhl,
showing the spinous processes of the lamell.T.

Hamilton gi-oup. PuUonham, Schoharie Co., N. Y.
The preceding figures represent the forms desciibed as Amada qiMclrtila, Conrad.
Fig. S. A .small left valve. The ear should be represented as somewhat oblique.

Hamilton group. Jefferson, Schoharie Co., iV. Y.
Figs. 9-11. Thi-ee left valves showing gradation in size and slight differences in form and surface char-
acter.
Fig. 12. A small right valve enlarged to two diameters. Another figure of this specimen is gi\en of the
natural size in fig. 17, pi. 84.

Hamilton group. Hamilton, Madison. Co., N. Y.
Figs. 18-1."). Three left valves diftering slightly in form ami surface ornaments.

Hamilton group. Schoharie Co., N. Y.
Figs. 10-20. A series of left valves reiire.senting the type A. Boydi of Conrad.
Figs. 21-23. Right valves asst)ciated with and corresponding to the preceding.
Fig. 24. Two individuals, each retaining both valves in contact.

Hamilton group. Figs. 16 and 17 are from Schoharie county ; the othere are from
Onondaga and Madi.^on counties, N. Y.
Figs. :iii. :i7. Two large left valves.

Hamilton group. Caze:noma, Madison Co., N. Y.
Fig. 28. The i-ight valve of the specimen, fig. 26, showing the comparative .size of the two valves.
Fig. 29. Cardinal view of the preceding. Another view of the left valve is given on plate 84, fig. 16.
Fig. 30. A right valve showing unusually fine concentric stria.
Hamilton group. Cazenovia, N. Y.

ACTINOPTERIA SUBDECUSSATA.

Page 110.
See Phite 17.
Fig. 25. A left valve showing the characters a.s preserved in a coarse shale.
Hamilton group. Cazenovia, N. Y.

ACTINOrXERIA PEROBLIQUA.

Page 116.

See Plate 84.

Fig. 31. The right valve of the .specimen described. Tin' left valve of this specimen is figured on plate 84,

fig. 14. Hamilton grouji. Cazenovia, JV. Y.

Paleontology NYVolV

I AVi(i'[.ii).+; )

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i'LATE XX.
Leioptekia Conradi.

Page 159.
Sefl Plate 8S.
Fijr. I- A liii's'*" l»'fl valve

Ilamillim {jriiiip. Cniianda'it/ua laki; N. T.
Kifr. 2. A siiecimeu of iiieilium sizo showiiijf strong concenlric undulations.

Hamilton gi'oup. liellona, Tatex Co., N. Y.
Kig. 4. A left valve. Another fig-iirc of this specimen is given on plate 88, fiy. a.

Leiopteria Bigsbyi.

Page lii,j.
8ee Plate 88.
Figs. 3, 11. Two left valves showing the form of the shell anil the line concentric stria;.
Figs. 13, 14. Two right \alves.
V\'S. 1"> A liirL'e left valve.

Hamilton group. f>flio?iarie Co., i\". i'.

Leiopteria l.evis.

Page l.W.
See Plate 17.
Fig. 5. A left val\e enlarged to two diameters.

Hamilton group. Ontario Co., N. Y.

Leiopteria RAFiNEsyuii.

I'age 161.
See Plates 15 and 88.
Fig. 6. A small left valve.

Hamilton gi-oup. ISkaiieatdc.'i lake, N. Y.
Fig. 7. A largei- examjile showing regulai- concentric undulations of the surface.
ITaniilton grou)i. Biilona, Yotts Co.. .A''. Y.

Leioitekia jMitciielij.
Page lee.
See Plate 88.
Fig. S. A left valve of this sjiecies.

Hamilton groop. From a houldji- rra (hi: toicit, of Cathenne, Schuyler Co., j\'. Y.

Leiopteria Greeni.

Page IGO.
See Plat« 88.
Fig. t). A large imlividual retaining both valves partly opened, showing the left valve and the oardinal
\iew' of the I'ight valve.

Hamilton group. BeUoua, Yate.1 Co., JV. Y.
Fig. 12. An imperfect left valve preserving a portion of the test and ^llowing the regular concentric

lamella'.

Hamilton grouj). -From ti boulder hi the town of Catherine, fiihnyhr Co., N. Y.

IjEioitekia Oweni.

Page 170.
Fig. 10. The specimen described, showing the right valve and the umbo of tlu' left.
Hamilton group. Cananrlnigiia lake, N. Y.

Leiopteria Dekayi.

Page 1(4.
See Plates 19 and 88.
Figs. 16-18. Tliree left \alves diflei-ing somewhat in form and obliquity.
Hamilton group. OUryo Co., JV. Y.

Actinopteria decussata.

Page 111.
See Plates 17, 18 and 84.
Fig. 19. A right valve. The speiMmen .shows the pallial line and nuiscular iniprc.«sion which features are
not i-ejircsenteil in the figure.

Hamilton group. Mailison Co., iV. 1'.

IS^IVJilllL^'DSir S-Jd^'CriF.

Paleeontolog/NY.VolV

I avio'lid.-f; . 1

Plate XX.

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J.H Eraerton del .

PLATE XXII.

Leptodesma ? sp. iudet.

Fig-. 1. An obscure rijjht valve of an indeterminate character.
Chemung' group. Ithaca, N. T.

Leptodesma complanatum.

Page 327.
Fig-. •!. The left valve described. The strijE should turn backward along- the hinge posterioi- to the beak.
Chemung group. Philipsburg, Allegliany, Co., N. Y.

Leptodesma Becki.

Page 185.
Fig. 3. A large right valve.

Chemung group. Co')iiing, Chemunc) Co., N. Y.
Fig. 4. A smaller imperfect example.

Chemung group. Near PartrrUle, Cattaraugus Co., iV". 1'.
Fig-, "i. A small left valve showing the form and pi-oportions of the shell.

Chemung group. Corning, iV. Y.

Leiopteeia Torrevi.

Page 174.
See Plate 88.
Figs. (i. 7. Two left valves, fig. 7, showing the characters of the species.

Chemung group. Fig. 6, from Panama; fig. 7, from SakDnanm. N. Y.

Leptodesma Matheri.

Page 193.
See Plate 89.
Fig. 8. An imperfect left \alve of medium size.
Fig. 9. A I'ight valve.

Fig. 10. A small left valve. The body of the valve is represented as too broad.
Chemung group. Bradford. McKean Co., Pa.

Leptodesma potens.

Page 188.

See Plates 31 and 89.
Fig. 11. A right valve.

Chemung group. Napoli, Cattaraugus Co., N. Y.
Fig. 12. A similar left valve. The extremity of the wing should be represented as acute as in fig. 19.

Chemung gi-oup. Near Clean, N. Y.
Fig. 19. A large left valve.

Chemung group. PortvUle. Cattaraugits Co., N. Y.
Fig. 20. A more elongate form referred to this species with some doubt.

Chemung group. Randolph, Cattaraugus Co., N. Y.
Fig. 21. A large elongate left valve.

Chemung group. Near Cassadaga. Chmitauqua Co.. N. Y.

Leptodesma umbonatum.

Page 198.
See Plate 90.
Fig. IB. The left valve described. Another figure of this specimen is given on plate 90, fig. 9.
Chemung group. Twenty Mile creek, Chautauqua Co., N. Y.

PLATE XXII— Conlinueil.

LErrODESMA USIBOXATUM, VftT. DEPKESSUM.

]'a;.'0 19'J.
Sof Plate 90.
Fi?. 14. The spnoiimMi il.'.scril.eil. Another tifjure of tlxii? speq^IU«^l jsigiveu on plate 90, fife'. Id.
Chemung' ^rouji. ^TopDli, Caltaraayus Co., N. T-

Lepto: - aviforme.

See Phite 23.

Fig. 15. The left Viilve cUwci-ibed. The antevior end shonM 1"- '■•' -.•.;<.■. 1 :.-i m,.,-.- ovi.Mi.le,! .•m„1 .n-ni,-.

and the exireniity <■<( tlie wing a.s nuicronate.
Chemung group. Near Ithaca, N. T.

LePTOOESMA POTENS, V;U. .ILVKNr..
Page MO. r

Kl^'. li;. A l.-li i.-ih.-.

Chemung group. Bust llaiulolph. ' F.

Licioi'TKuiA Ciie.muxgexsi.s.

I'ajfC 17-2: > ■ I i.i
Figs. 17, IS. Opposite views of the original .speeimcn showing Ihe left and right valves. The right valve i.s
imlieildeil vertically in the roek and has beeanmeh shortened by the shrinkage or compi'ession
of the layers, while the surface of the shell has been slightly, wn-inkled from the ^arae cau.se.
Cliemung group. Eiyht inihs north of Bhmiiamti';:. .T. 1'.

Lei'touesma Ly.saxuer.

tase 21fi.
See Plate 90.
Fi". 22. A left valve. The figure is partially lestored and should rejiresent the.body as considerably wider.
Chennuig group. Maiinfidd. Tiorja. Co., I'u.

Leptojjesma extexuatu.m.

Page -207.
See Plate 90.
Fig. 23. An imperfect left valve. Another figure of this specimen is given on plate 90, fig. 17.
Chemung group. PJni'qislMrr/, AUeffJiaiiy Co., iV. I'.

Pteuoxites kostuatus.

Page 2»S.
Fig. 24. The left valve described.

Chemung gi-ouji. JiockvUle, N. Y.

PtEHOXITES PaOFl'XDUS.

l'age-237.
Fig 2.1. A small left valve.

Chemung group. A'cic Albion, C'attaruiiyii.i (.'<>., ^V. X'.
Fig. 2(5. A larger example. The anterior side should show reguLir concentric uudnhitions.

Chennuig group. Jiandntpli. Catlaraiif/us Co., N. )'.
Fig. 27. A large indiviilual, imperfect on the anterior end.

Chemung group. Niar Oleaii, N. T.

Leptoijessia aliforme.

Pago 2-20.
See Plate 91.
Fig. 28. A right valve. This speiimen is redrawn o.i plate 91, tig. 2, ami represents more rlearly the
specific ehnracters. I ■

Chemung group. Niiir Aiif/fJli-ii. Allic/haiiy Co., N. Y.

Paleontology NYVolV.

( AVlCrl,ID,-E . I

Plate XXn.

SW^ ^^BE3Tsa»'

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15

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r-'irrriaT'.r.lK'

PLATE XXIII.

Leptodesma jjav ifokme.

Page 200.
: I : See Plate 22.
Fig-. 1. A right valve showing- the characters of the shell.
Chemung g-roup. Near Ithaca, N. Y.

ACTIXOPTERIA PEKSTRIALIS.

Page lis.

See Plate 84.
Fig-. 2. A loft valve.
Fig-. 7. A rig-ht \ al\"e of a l:irg-cr example.

Chemung- gfoup. Ithaca, N- i'.

ACTINOPTEKIA DELTA.

Page l-'l.
Fig-. ?: The left v.-ilv(! described.

(^houiuiig- gronp. Ithaca, JV. Y.

ACTtXOPTEUIA EPSILOX.
Page 12-2.

Fig. 4. A small left valvft. ■ : . _ .,

Figs. .^, 6. Two left valves refei-i-ed to this species with some dmibt on .nccoaiit of theii- liner surface radii.
Fig-. 8. An imj^ressiou of a left valve, retaining that of the rig-ht vah-e beueatli it in the centre, thus show-
ing partly the features of both.

(Chemung g-roup. Ithaca, JY. Y.

xVCTINOPTERIA ZETA.
Page Hi.
See Plate 84.
Fig. 51. A i-ig-ht \-alve showing the form and surface ornamentation, with two oblique lateral teeth.
Chemnng gronp. Ithaca, iV. Y.

Ptychoiteeia expansa.

Page 1.5-2.
Fig. 10. The left \-alve describe<l showing the form and surface .OTOamentation. The body is represented

as too narrow and there shoXUd be a slight fm-row limiting- the wing.
Fig. 11. An enlargement of the snrface from the anterior nmbonal slope, showing the direction of the radii.
Chemung grcuvp.; Slmethport, Pn.

PxYCIiOPXEKIA PeOTO.

Page 129.
Figs. 12, 14. Two left valves. The wings in each one .shonld be limited liy a slight fnrruw.
Chemung g-rouij. Near Smethport, Pa.

PLATE XXIII— Continaotl.

PtYCHOPTERIA SINIOSA.

Page 130.

See Plate 85.

Fig. 13. A left valve showing the form and surface characters. The wing should be limited by a shallow

furrnw.

Chemung group. Near Smethport, Pa.

Leptodesma Mentor.

Page 20b.
See Plate 90.
Fig. 15. An imperfect right valve supposed to belong to this species from its association.
Chemung group. Near Sinethport, Pa.

Ptyciioi'teria Sao.

Page U-2.
See Plate 8.5.
Fig. 16. A left valve of medium size. The fold and furrow of the wing should !)<> n'liresented a.s stronger.
Fig. 23. An associated right valve.

Cliemung gi-oup. Panama, Chautauqua Co., N. Y.

Ptyctiopteria Salamanca.

Page 131.
Figs. 17, 18. Two left valves showing the foi-m of the shell and surface character. Fig. 18 should show an

alar fold similar to fig. 17.
Fig. 19. A cardinal view of the specimen, fig. 18, showing the relative convexity of the valves and the com-
parative elevation of the lieaks.
Fig. 20. The right side of a specimen preserving both valves partly opi'oed.
Chemung group. Near Salamanca, iV. Y.

PtYCHOPTERIA ALATA.

Page 13H.

See Plate 85.
Figs. 21, 22. Two small right valves.
Figs. 25, 26. Two larger characteristic right valves.

Chemung gi-oup. Salamanca, N. Y.

PtYCHOPTERIA EuCRATE.

Page 133.

See Plate 85.

Fig. 24. The right side of a specimen preserWng both valves. *
Chemung group. Panama, N. Y.

ECTENODESMA BIROSTRATf.M.

Page -242.

See Plate 84.

Fig. 27. A right vahe leferrod to this .species, showing the form, surfai-e oi-namentation and strong, oblique

lateral tooth.

Chemung grouji. Four miles north of Chenango Fork.i, N. Y.
Figs. 28-30. Three left valves in ditfi-rent degrees of preservation, showing some variation in ftirm and
surface marliings.

Chemung group. Franklin, Ddaxeare Co.. N. Y.

(Eiiii]ESiainr3?!r© ©mmwip.

Paleontology NYVoiy.

( Avirri.iD.« )

Plate ^'-in.

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PLATE XXIV.

Pterinopecten imbecihs.

Paf^e 75.
Fig-. 1 . An imperfect left vahe, X 2.

Chemung group. T'lorja, T'loya Co.. Pa.

Ptekinopectex (Aviculopecten) strictus.

Page 74.

See Plate 82. .
Fig. 2. A right ^•alve showing the form of the shell and the characters of the hinge.
Chemung group. Near EVmlra, N. I.

AVICULOPECTEN PLENUS.

Page 21.
Fig. 3. A left valve, showing the genei-al features of the shell.
Chemung group. Near Elmira, N. Y.

AviCULOPECTEN IdAS.
Page 13.

See Plate 3.
Fig. 4. A right valve.

Hamilton group. Cayuga lake, N. Y.

Lyriopecten SOLUX.

Page 56.
Fig. r.. A right valve, imperfect anterior to the beak. The recent discovery of the impression of this valve
substantiates the correctness of the restoration of the anterior ear in the figure.
Chemung group. Panama, N. Y.

'.■,i:! !■!

ri.ATK \.\rv— Contiimcil.

Pterinea (Veutumxia) reveksa.

Page 104.
See Plate 84.
Fig. t>. A large right valve. Another figure of this specimen is given on plate 84, fig. 24, to show the
ob.solescence of the rays on the wing.

Chemung group. Elmira, N. Y.
Fig. 12. A specimen with the valves united along the hinge, showing the convex right valvo and flat or
concave left valve.

Chemung group. Chemung river. Upper Narroios, N. Y.

AVICCLOPECTEN PRINCEPS.

I'agc 1.
See Plates!, f>, 6 an.l SI.
Fig. 7. An enlargement, to two diameters, of the impres.sion of the hinge, showing the striations of the
, liganient.al area.

Hamilton grouj). Cazetinrin, iV. Y.

I.,VI!IOPECTEN CYJIIl.VLON.
Page 47.
Fig. 8. A large, perfect left valve. The specimen shows a striated ligamental area.
Hamilton group. Prom a boulder near Elmira, N. Y.

Ptekinea (Vertumnia) avis.

P.nge lie.
Fig. 9. An imperfect right valve.

Chemung group. Near Elmira, JV. Y.
Fig. II. A large, convex right valve. The figure should be restored at the cardinal angles to correspond
with fig. 13.

Chemung group. Mansfield, Pa. ' ; n ' .'
Fig. 13. A nearly entire left valve. The liyssal sinus should be a little deeper than is represented.
Chemung group. Near Elmira, N. Y.

Pterinopecten suborbiculauis.

Page SO.
See Plates 8 and 82.
Fig. 10. A view of a large and very perfect left valve. The radii increase by intwstitial addition and not
by bifurcation as is represented in the figure.

Chemung group. Elm Vnlliij, Alleghany Co.. N. Y.

LiMOPTERA MACROPTERA.

Page 246.
.See Plates 26, 27, 28, 29 and 92.
Fig. 14. A small right valve showing the form and surface ornamentation.
Hamilton group. Pratt's Fall.i, Onondaga Co., N. Y.

Allocardium alternatum, gen. et sp. nov.

Fig. 1.5. A view of the spec-men enlarged to two diametei-s. The relations of this shell are not apparent.
It has the a-spect of a bivalve shell in the charactei-s of the rays and the cardinal aurionlation,
and somewhat resemliles Hii'i'Aui's and Trigoniluna. With the present materi.al it cannot
be satisfactorily arranged with any known genus of molluscs.
Hamilton group. Cayuga lake, N. Y.

Pateontology NYVol V

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PLATE XXV.

ACTINOPTEKIA EXIMIA.

Viiga 107.
Fig-. 1. A left valve somewhat imperfect on the wiiiff but showing' the form of the l)ody and .surface
ornamentation.

Schohai-ie grit, fichohark: N. T.

Leptodesma disparile.

rase 186.
See Plate 89.
Fig-s. 2, 3. Two right \-alves. The wing- margin of fig. 2 should be sinuate to correspond with fig. ;!.
Fig. 4. A left valve.

Chemung group. McKean Co.. Pa.

Leptodesma curvatum.

Page 19K.
Fig. 5. The left valve desci-ibed.

Chemvuig group. McKean Co., Pa.

^I'l.VTK XXV— Coiitiiiueil. '

Leitouesma Okodes.

See Plato 90.
Figs. 0. 0. Two left val\o.«. The .s])i-ciiiien fig. 9, is reiliawn on pi. 00, fig. 8.

Fig. 10. A largo l>'fl valve soincwliat ilistorted by pic^ssure ami ref«;n>e.l to the specie.'! with .loulit.
Chemung group. JVrar tSinet?iport, Pa.

Leptodesma mytiliforme.

Paso 2:J3.
See Plate 91.
Figs. 7, 11. A right and left valve. Other illustrations of these specimens are given on plate 91. figs. 22
and 24, .'ihow-ing more clearly the specific charac^tei-s.
Chemung gi-oui). Near Smethport, Pa.

Leptodesma Maclurii.

Page 'JiS.
Soo Plate 91.
Fig. 8. A right valve. See fig. 14, pi. 91, for another figure of thi.s specimen.
Fig. 13. A left valve. Another figiu-e of the .specimen is given on plate 91. fig. 13.
Chemung group. Near Smttliport, Pa.

Leptodesma rude.

Page 2-21
See Plate 91.

Fig. 12. The left valve described. See fig. 3, pi. 91.

Chemung group. Near SmeUiporf, Pa.

Gr-YPTODESMA ERECTUM.

Page loi.
See Plates 11, 12, 13, 8(5 and 87.
Fig. 14. An interiud mouhl of the upper portion of a left valve shownng the lateral teeth and striated
ligameiital area. The large scar on the post-umbonal slope was probably made by the
attachment of a Crania to the shell and covei-s a portion of the large muscular impression.
Hamilton group. From a boulder near Ni(hol.i, N. Y.
Fig. la. An internal cast of a right valve, showing the pallial line and im)irinl of a strong posterior tooth.

Hamilton grouj). Otsego Co., N. Y.
Figs. !i;, 17. A riL'-hl and a left valve a.s preserved in a cherty limestone.
Hamilton gi-oup. Indiana.

Pal;eopinna flabella.

Page 240.
See Plate 87.
Fig. IS. Till' li'ft valve desci-ibed. See plate 87, fig. 4.

Oriskany sandstone. iScJioharie. N. Y.

Pai..eopixna kecurva.

Page 241.
Fig. 19. A view of a lai"ge imperfect li'ft valv<r.

I'pper Helderberir irrcmp. S'laffurd. Ciene.tee Co., N. T.

Palaeontology NY Vol V

( AVirvuD.*: . I

Plate XXE

L^

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H M MartiTt del .

Ph-.l>,3U!th

PLATE XXVI.

LlJIOl'TEKA CANCELLATA.

Page 244.

See Plate 92.

Fig-. 1. TiM" li'it valvi' oi .1 spi-ciim-ri. Another fi<^iire of this valve is given on plate 92, fig. 3.

Fifr. 2. The riirht side of the same. The jiallial line and mu.sc-iilai' imin-ession are visible in each val\c

lint are not repre.setited in the figure.
Fig. 3. A carilinal view, showing at a, a', the filling of the nmbonal adductor muscular attachment where

the pallial line terminates.
Fig. -1. An enlargement of the snrfjice from the left valve.
Hamilton group. Falls of the Ohio.

LlMOlTERA PAUPERATA.

Page .;43.
Fig. 5. View of an impei-fect left valve. The radii on the wing and posterior side of the body are not
made sufficiently distinct.

Upper Helderberg gi-onp. ^Stafford, Genexee Co., N. Y.

LiMOPTERA MACROPTERA.

Page 246.
8ee Plates 24, 27, 28, 29 and 92.
Figs. (>, 7. Two left valves .showing the striatious of the hinge area.

Hamilton group. Madison Co., N. Y.
Fig. S. The profile of a small specimen which has been laterally iiiiiii)ri-.<.si-d, giving more than the natural
rotundity.

Hamilton group. Cazerutvia, N. Y.
Fig. 9. A view of the left valve showing fewer an<l stronger radii than u.sual.

Ll-UOFIERA OBSOLETA?

Page 249.

See Plates 29 and 92.

Fig. 10. A view of the upper portion of the light side of a specimen, .showing the broad striat«d ligamental

area of the left \alve.

Hamilton group. Cazenovia, N. Y.

( AMnOXVCIIIID--E . I

Palee ontology NY.VolV.

Plate XX?L

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vrillJiJiBSS'lijCli** --^---'"' V?" "

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PLATE XXYII.

LiMOPTEKA JIACKOPTERA."

Page 246.-
See Plates 24, 26, 28, 29 and 92.
Fig. 1. The rig-ht valve of a Fmall imliviilnal which is very perfect in fomi.
Fig. 2. A small right vahe.

Hamilton group. Summit, 8clioharie Co., N. Y.
Fig. 3. A .somewhat larger example.

Hamilton group. Lebanon, Madlion Co., N. Y.
Fig. 4. A left valve oliliquely compressed and showing no surface radii.
Fig. 5. The right valve of the preceding.

Fig. 10. A profile view showing the comparative convexity of the valves. This specimen is the original
of Conrad's description.

Hamilton group. Madiiim Co., N. Y.
Figs, (i, 7. Two views of a sjiecinien which shows very distinctly the character of the surface.
Fig. 8. A cardinal view of a large specimen. The figure was intended to .show the striated area of both
\ alves an<l a vertical depression undoi' the beafc as if from a receding cartilage pit ; but
these features have imfortunately >>een lost in the lithography.
V'li:. '.>. A i-ardinal view of an individual distorted by lateral compression. The internal mould shows one
distinct point of muscular attachment on the apex of each valve. See plate 28, fig. 4, for an
illystration of the right \alve of this specimen showing the umbonal muscular impression and
pallial line.

Hamilton group. Madison, Co., N. Y.

mjiiMiiiL^Jimsjr ©mmwip.

PalceontologyNYVolV

( AMnoxvcHiin.« )

PlatelXVtI.

U-.js.^impsotL cLicj

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PLATE XXVIII.

LiMOPTERA CUKVATA.

Page 250.
Fig. 1. A large loft valve showing- the anteiior ciirvatui-e of the beak and the alternation of the radii.
Fip. 2. An internal cast of a left valve showing- the inler-pallial area covered with small imstules which
were ajiparently the points of attachment for umbonal muscles. The spei-inien shows the pal-
lial line and muscular impression.
Fig. 3. The left valve of a large specimen, showing the wing and some ti-aces of the i-adii. ITio post-basal
margin is not snftii-i«'ntly extended in the figure.
Il.-uiiiltim group. Madhon Co., N. ¥.

LiMOPTERA MACROPTEIiA.

Page HI':

See Plates 24, 26, 27, 29 and 02.

Fig. 4. Till- I'ight side of a, laterally compressed specimen, representeil on pi. 27, tig. 9, and pi. 29, fig. 2.

The umbonal scar is here shown in its true po.sition.
Fig. a. The left side of aii unusually elongate spe<-imen, due in ]>art to tlio l)reaking away of the margin
of the left valve to the margin of the right valve.
Hamilton group. Madison Co., N. Y.

Palaeontology NY Vol V,

( AMBONYCHIID.*: . )

piateixym.

■S-wiiLtijn, ii; i

Fig.

1.

Fig.

2.

Fiirs.

3.

PLATE XXIX.

LiMOPTERA MACROPTEEA.

Page 24G.
See Plates 24, 2G, 27, 28 and 02.
The i-ifcht siile of the specimen fig-. S, plate 20.

A \ iow of Ihf left .«ide of the specimen fig:. 9, pi. 27, and lig. 4, pi. 28.

4. The profile and left views of a much distorted specimen, showing the effects of compression.
Hamilton group. Madinoii Co., N. Y.

LiMOPTERA OBSOLETA.
rage 249.
See Plates 26 and 92.
Fig. 5. The left side of a specimen slightly impei-fect on the anterior side, but showing the usual surface
charactei-s.

Hamilton group. Hamilton, MadUicm Co., N. Y.
Fig. ij. A left valvt" showing the sui-face characters and the sti-iated ligamental area.
Hamilton group. Cayuga lake, N. Y.

Palaeontology NYVol V.

Plate IXII

G3.SiiTi:pson. del .

Svrmtcm, \itli

PLATK XXX.

Mviir.AUCA (Pl,KTIl()MVTILUs) AltKXO.SA.

I'age -i-i;).

Sop Plate 87.
Kit.'. 1. .\ lif^ht viilvH of niydium si/o.

Schoharie g-i-it, f^alioliarie, N. Y.

MVTILAUCA (Pl.ETHOMYTILUS) PONDEKOSA.
Viigc *2.>4.
KifT. 2. A lifrht valve of a small specimen.

Ki);. '.i. A. left valve of a lavijer specimen, showing' con-siderable extension of hinge-line.
Fiir. 4. A left valve of meilium .size.

Upper HelrlcM-lierg group. Clarence. Hollow. Erie Co., N. Y.
Fig. 5. The under .side of the rosti-al portion of a specimen showing the gi-eat breadth of the striated liga-
mental area. The margin of the shell is comjiressed and bent inwards on the anterior side
showing the surface striiE.

Upper Helderberg group. Columbus, Ohio.

Figs, li, 7. The profile and left \iews of a large specimen entirely denuded of the te.8t.

Upper Helderberg group. Columbus, Ohio.

( amboxychiiDvk: )

Paleontology NY.Vol V.

Plate XXX.

J.H Emerion deJ

'^.vriTJ:QTi, lilJti .

Kijr.

1.

Fife'.

2.

Fig.
Fiir.

3.
4.

PLATE XXXI.

MvTiL.iitCA (Pletiiomvtilis) oviformis.

Page "2.55.
See Plate 87.

.\ lift valve of a young' shell of elongate form.

Hamilton group. Cayuga lake, N. Y. ,

2. A left valve of the ordiiiai-y size, .showing the sti-iateil hinge-area and three posterior teeth on the
wing whii-h are not sufficiently marked in the lithography.
Hamilton group. Cayuga lake, X. If.
A i-ight valve showing the strong ligamental area.
A more elongate form with attenuate beak.

Hamilton group. York Centre, Hvingslon Co., N. T.
Fig. ."). Till' anterior .side of a compressed .speeimon presei-ving the valves in contact at the hinge, but
widely parted below.

Hamilton group. GeTieseo, Livingston Co., N. Y.
Fig. G. A large i-ight valve widened below by compression.

Hamilton group. Seneca lake, N. Y.
Fig. 7. A ca.st of a .small elongate right valve. The beak has been removed to show the ligamental ai-ea :
the three oblique lateral teeth are seen on the post-£ardinal .angle.
Hamilton group. Canandaigua lake, N. Y.
Fig. 8. A large, broad right valve showing an unusually short hinge-area.
Hamilton group. Belloiia, Yates Co., N'. Y.

GOSSELETTIA TRIQUETRA.

rage 2ti5.
See Plate 87.
Fig. 9. A view of the left valve of a young individual of this species.
Fig. 10. The right side of a vej'y ventricose si^ecimen preserving the natural form. Supposed to be the

original specimen.
Figs. 11, 18. 14. The Left, cardinal and posterior ^•iews of a specimen preserWng the natural convexity
and showing the posterior teeth of the left valve.
Hamilton group. Onondaga Co., N. Y.
Fig. 12. The anterior side of a similar specimen showing the anterior muscular impressions.

Hamilton grouj). Oiwndaga Co., N. Y.
Fig. 15. A partial cast of a left valve. The beak has been removed to show the strong anterior teeth and
anterior muscular impression.

Hamilton group. Fultonham, Schoharie Co., N. Y.
Fig. ] li. A large left valvi? preser\ing the surface markings and the ligamental area.

Hamilton group. Fultonham, Schoharie Co., N. Y.
Fig. 17. A large right valve.

Hamilton group. Madison Co., N. Y.

MJiMiHiLTriDjKr ©m[ffiwip =

Palaeontology NYVolV

( AMBO>r\'CHIID,'E . )

Plate. XXH.

JW.Hall del.

S-^vintoiv, lith-.-

PLATE XXXTT.
Mytilakca u.mp.onata.

I'age 257.
Figs. 1—1. The right, left, .•inti'i-inr iiml posterior views of an iinliviilual preserving both valves. The
si)ecimen has been slightly compressed laterally, giving an unnatural sharpness to the rostral
portions.

Chemung group. Ithaca. iV. Y.
Figs. 5, 6. 7. The posterior, anterior and right sides of a specimen. Fig. G shows what appears to be the
pallial line tenninating near the beak.

Chemung group. Mansfield, Pa.

Mttilakca Ciiemungensis.

P.lftC -258.

Fig. 8. A small right valve showing the striated ligamental area.

Chemung gi'Oup. Philipsburg, Alleghany Co., N. T.
Fig. 9. A left valve with the beak partially broken away showing the small cardinal teeth.

Chemung group. Itockville, Alleghany Co., iV. Y.
Fig. 10. Tlie interior of a left valve from an impression in the shale, showing the striated hinge-area.

Chemung group. Jiockvillc, i\r. Y.
Fig. 11. A small, broad right valve.

Fig. 13. An impression of the margin of a large left valve, showing the form of the hinge and its breadth as
extending within the margin of the shell.

Chemung gi-oup. Rockeille, N. Y.
Fig. 14. A very narrow and erect left valve showing also the striatioiis of the hinge.

Chemung gi-oup. Ea.'^t Randolph, JV. I'.

MviILARCA REOULARIS.
Page 260.
Fig. 12. A left valve showing the broad rounded form and straight erect beak.
Chemung group. Leim Ctnlre, Cattara^igus Co., N. Y.

Mytilarca carinata.

I'agc 2.")9.
See Plate 33.
Fig. 15. A small left valve.

Chemung group. Near Elmira, N. Y.
Fig. 10. A small right valve showing the form of the shell.

Chemung group. FactoryviUe, Tioga Co., N. Y.
Figs. 17, 18. Two opposite valves showing some variation in the form of the shell.

Chemung group. Near Elmira, N. 1'.
Fig. 19. An internal cast preserving impressions of the cardinal and lateral teeth and showing the striated
ligamental area.

Chemung group. Near Elmira, N. Y

Mytilarca attexuata. »

I'age 2('i0.
Fig. 20. A left valve showing the erect subcannate form and attenuate beak.
Chemung group. Elmira, N. Y.

Byssopterta RADIATA.

Page ~o'l.

See Plate 80.

Fig. 21. A right valve imperfect at the beak, but showing the surface characters and angular anterior .sitle.

Fig. 22. An imperfect left valve which shows the general outline. The radii are not so distinctly dujilicate

as on the other specimen.

Chemung group. Mansfield, Tioga Co., Pa.

(BiniESiawEa'LE. ©aiffiwiF.

Palaeontology NY Vol V,

( AMBONYCHIin^E . )

Plate XXXIl

8

4-

22

IK.E.i'OS.S.Jjsi

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PLATE XXXIII.

GOSSELETTIA RETUSA.

Page 260.
Fig-. 1. The left side of a well-preserved sjiecimen, showing the general form of the shell.

Hamilton group. Eighteen Mile creek, Erie Co., N. Y.
Fig. 2. The antero-cardinal view of the same.

Mytilarca occidentalis.

Page 203.
See Plate 87.
Fig. 3. A view of the right sUe of the original of this species.
Fig. 4. The anterior view of the same

Fig. 5. A left valve. The ante-byssal portion is represented as too large. See fig. 11, plate S7.
Yellow sandstone. Burlington. Iowa.

Mytilarca fibristriata.

Page 264.

See Plate 87.

Fig. G. A left valve. Anothei- figure of this specimen is given on plate 87. fig. 6. to show tlie foi-ni of the

anterioi- end and the presence of radii.
Fig. 7. The right side of the original specimen as seen in a sulphur cast.
Yellow sandstones. Burlington, Iowa.

IM.AI'IO XXXIII— CoiUinue.l.

IMvTIIAIiCA CAHINATA.

I'aKc iV.!.-.

See Plate 32.

Fig-. 8. Airenlargeinent of the cardinal portion of fig. 19, plate 32. lus ohtaiiieil from an iiiipros.sion, showing

more clearly the hinge characters.

Cliemnnf,'- ^'roni>. Near Elmira, N. Y.

MoDiOLA (Mytilops) pr^cedens.

Pat'O 2U7.
Fig. '.'. A sntall left valve denuded of the strife.

Figs. 10, 11. Cardinal views of two sperimen.s with the valves partly opened.
Fig. 12. A .small right valve.

Fig. 13. A left valve of medium .size, preserving the surface stria-.
Fig. 14. An elongate i-ight vahe, showing the surface characters.

Chemung group. Oltan, JV. Y.
Fig. 15. A right \alve, prob.'ibly of this species but showing no surface stria".

Chemung group, ^methport, Pa.
Fig. 16. The car<Uiuil view of a specimen, with both valves strongly striate.
Fig. 17. A large broail specimen jireserving the surface markings.
Fig. IS. The anterior view of an example showing nearly equal convexity of both valves.

Chemung group. Olean, iV. Y.

Mytii.auca simplex.

Page 261.
Fig. 19. A large right valve, showing varices of growth.

Fig. 21. A smaller left valve. The beak should be directe<l slightly to the li'ft to give the proper expres-
sion to the figure.

Chemung group. Smethpni't, Pa.

.MVTILAUCA GIBBOSA.
Page 26J.
See Plate 87.
Fig. 20. The left vahe descritted. Another figure is given on jilate 87, fig. 7.
Chemung grouj). Napnl), Cattaraugiis Co., N. Y.

MvTILARCA LATA.

Pace 263.
Fig. 22. A right valve showing the lii'oad form of the shell.
Chemung groui). Randolph, N. Y.

MoDiOLA (Mytilops) metella.

Page 208.
See Plate 87.
Figs. 23, 24. Two right \alves showing the general form of the shell. A figure of .another specimen is given
on plate 87 in the same position ils the figures of M. prascedtn.s on the present plate for a better
comparison.

Chemung group. Cliautauqua Co., N. Y.

iii^aaniLirajM '^ (^mmmmm^ mmwrnp^ . (■\c

Palaeontology NY.VolV

( AMUONVCmiD.lC i MYTILID-E.)

PlateXXXm

J.W.H.a. H, MM. del.

PLATE LXXXI.

AviCUT,OPECTEN FASCICULATUS.

Page 11.
See Plate 5.
Fig. 1. A left v.alve showing the characteristic fasciculate radii.

Hamilton group. Near Clarksville, Albany Co., N. T.
Fig. 2. A left valve with tiner and more regulai- radii.

Hamilton group. Near Clarksville, N. Y.
Fig. 3. The specimen pi. 5, tig. 11, redrawn to show the concentric striae.

Hamilton group. Castleton, Ontario Co., N. T.
Fig. 4. A right valve preserving the radii on the ears and showing the subdued characters of the surface
as compared with the left valve.

Hamilton group. Near Clarksnille, N. Y.

AVICDLOPECTEN LAUTUS.

Page 14.
See Plate 3.
Fig. 5. A figure made from an impression in gutta-percha, from the interior of the specimen illustrated
on pi. 3, fig. 17, showing more clearly the surface ornamentation.
Hamilton group. York Centre, Livingston Co., N. Y.

1

I

PLATE LXXXI— Contlnneil.

AviCULOPECTEN TENUIS,

Page 39.

See Plate 7.

Fig. 6. The left valve represented on pi. 7, fig. 23, redrawn to show the true form ami ornamentation,

with the pallial line and muscular impression.

Chemung group. Near Salamanca, N. Y.

AviCULOPECTEN INSIGNIS,

Page 34.

See Plates 1 and 3.

Fig. 7. A left valve preserving the form and proportions in greater perfection than shown on the previous

plates. Hamilton group. Stafford, Genesee Co., N. T.

AviCULOPECTEN BELLUS.
Page 33.

See Plate 2.
Fig. 8. A light valve, X 2.

AviCULOPECTEN DUPLICATU8.

Page 17.
See Plate 7.
Fig. 9. A left valve showing th<! coarse radii on the pallial margin.

Chemung group. Mansfield, Pa.
Fig. 10. An entire right valve.

Chemung group. Mansfield, Pa.

AviCULOPECTEN KUGiESTRIATUS.
Page 15.
See Plate 7.
Fig. 11. A right valve preserving the surface characters with considerable perfection.

Chemung group. Uockiulle, N. Y.
Fig. 12. Several of the railii, of the jireceding specimen, enlarged two diameters to show the changes in
surface ornamentation from llio beak to the base.

AviCULOPECTEN PBINCEPS.
Pago I.
See Plates 1, 5, 6 and 24.
A right valve showing the pallial line and muscular impression.

Hamilton gi-oup. Ludlowville, iV. Y.
A specimen \vith a portion of the left valve removed showing the interior of the right valve ami
the diffei-ence in .size between the right and left valves.

Hamilton group. MuttanviUe, Ontario Co., N. Y.
A left valve as preserved in limestone.

Hamilton group. Delaioare, Ohio.
A specimen preserved in a soft shale .showing strong regular concentric strijp.

Hamilton group. Livinff.iton Co., N. Y.
An indivi<lual vertically imbedded in the shales showing the effects of compres.sion and ciistortion.
Hamilton group. N. Y.

Fig.

13.

Fig.

14.

Fig.

l.'>.

Fig.

16.

Fig.

17.

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PLATE LXXXII.

AVICULOPEGTEN ^QUILATERALIS.

Page 19.
Fig 1. A left valve showing tiie fo:-m and surface ornamentation.

Chemung gi-oup. Alleghany Springs, Watren Co., Pa.

Lyriopecten anomi^formis.

Page 53.
See Plates 4 and 10.
Fig. 2. The specimen illustrated on plate 10, fig. 5, redrawn to show the proper form and surface orna-
mentation. , ', ,
Chemimg group. Chemung creek, N. Y.

Lyriopecten orbicularis.

Page 42.
See Plate 4.
Fig. 3. A specimen with the upper portion of the left valve removed, showing the exterior impression of
the right valve and the comparative size of the two valves.
Hamilton group. Canandaigua lake, N. Y.

Pterinopeoten suborbicularis.

Page SO.
See Plates 8 and 24.
Fig. 4. A right val\-e of this species showing the deep byssal sinus.
Chemung gi-oup. Mansfield, Pa.

Lyriopecten interradiatus.

P.-ige 44.
See Plate 2.
Fig. 5. A large left valve showing the surface ornamentation and the ligamental area.
Hamilton group. Schoharie Co., N. Y.

Lyriopecten Priamus.

Page 54.

See Plate 10.
Fig. 6. A right \'alve of this species.

Chemung group. Franklin, Delavmre Co., N. Y.

Pterinopeoten undosus.

Page 72.
See Plate 2.
Fig. 7. A left valve with comparatively few radii, and the strong characteristic concenti-ic undulations.
Hamilton gi-oup. Bethany, N. Y.

Pterinopeoten keelexus.

Page 58.
Fig. 8. A view of the interior of a left valve.

Corniferous limestone. Ohio falls.

PLATE LXXXII— Continued.

Pterinopecten filitextus.

Page 67.

See Plate 17.

Fig-. 9. A specimen showing the interior of the right valve and preserving the pallial margin of the left

valve. Hamilton group. Onondaga creek, iV. T.
Fig. 10. An enlargement, to three diametei-s, of a portion of the surface of the specimen illustrated on plate
17, fig. 22.

Hamilton group. F'rom a boiddei; Pine Valley, N. Y.

Pterinopecten dispandus.

Page 76.
Fig. 11. A right valve of this species.

Fig. 12. A left valve.

Chemung group. Mansfield, Pa.

Pterinopecten nodosus.

Page 60.
Fig. 13. The imperfect left valve described, showing the characteristic nodose radii.
Comiferous limestone. Ohio falls.

Pterinopecten crenicostatus.

Page 78.
See Plate 8.
Fig. 14. The specimen plate 8, fig. 4, I'edrawu and restored in outline to show the entire form and details
of surface charactei-s.

Chemung group. Near Angelica, N. Y.

Pterinopecten erectus.

Page 77.
Fig. 15. A specimen with the upper portion of the left valve br(iken away, showing the interior of the

right valve.
Fig. 16. A left valve of medium size.
Fig. 17. A large left valve.

Chemung group. Itliaca, N. Y.

Pterinopecten (Aviculopecten ?) strictus.

Page 74.
See Plate 24.
Fig. 18. A left valve, associated with the right valve illustrated on plate 24.
Chemung group. Near Elmira, N. Y.

Pterinea (Vertumnia) keproba.

Page 106.
Fig. 19. A left valve. .

Fig. 20. The convex right valve of a largei- individual than the jireceding.

Chemung group. Ithaca, N. Y.

Aviculopecten (Pterinopecten) invalidus.

Pago 31.
See Plate 1.
Fig. 21. The left valve, fig. 18, plate 1, ilrawn of natural size, showing the true form and proportions.
Marcellus shale. Cherry Valley, N. Y.

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PLATE LXXXIII.

Pterinopecten regularis.

Page 7(i.
Fig. 1. A left valve showing- the characteristic form and sni-fare markiufifs.
Hamilton g-roup. TAiiing.itim Co., N. Y.

Pterinopecten Vehtumnus.

i'age 71.
8ee Plate 5.
Fig. 2. A small specimen preserving- the left valve entire and a portion of the right -s'alve.

Hamilton group. Onondaga Co., N. Y.
Fig. 3. A left \-alve to show the characters of the surface ornamentation.
Hamilton group. Sknneatdes lake, N. Y.

Pteuinopecten intermedius.

Page 68.
See Plate 17.
Fig. -4. A left valve wholly denuded of the test.

Hamilton gi-oup. Cayiiga lake, N. Y.
Fig. 5. A left valve as obtained from an imjn'ession of the extei-ior in the matrix, showing- the foi-m anil
surface markings.

Hamilton group. Cayuga lake, N. Y.

I'I.ATK I..\X.\III— (Juiitimic-il.

Pteuinopecten exfoi.iatus.

tage 01.

See Plate 1.

Fig'. G. A left viilve as obtained from an impression of the matrix, showing- the foi-ui and surface charactei-s.

Fi{r. 7. A laige imperfect left valve with the test almost wholly exfoliated ami ]>resenling a strongf contrast

with the preceding.

Limestone of Miircellus .«hale. Qeiiesee Co., N. Y.

Cren'ipecten Leon.

Page tM.
See Plate y.
Fig-. 8. The left valve described sliowinj^ the hinge characters and I'oi-m of the valve.
Cliemung- g-roup. Lemi, Ckiftaraugns Co., N. Y.

Crenipectex likatus.

IMge >*7.
.See Plate i».
Fig-. '.I. A left valve showing the form and size of the ears given in correction of tig. 24, plate H.
Chemung gi'ouj). Cnmtewavgo, Cnttavangus Cn., N. Y.

Ckenipecten kmpomtus.

Page S3.

See Plate H.
Fig. 10. A snnill left valve.

C'hianung gronj). (Ihnii, J\'. Y.

I'iKlMNEA FLAHELLA.
Page 93.
Se.- Plates 14 and 1. "5.
Fig. 11. .\ large left valve showing but three .strong radii.

Chemung gronp. Lawremmnlle, Tioyii Co., Pa.
Fig. I'J. The internal mould of a left valve, showing tin- liL.'-nini'ntal area, lateral and cardinal tei'th. pallial
line and both muscular impi-e.ssions.

Hamilton grouj). Si-hoharie Co., A. 1.

PtEKINEA PINGUIS.

Page 92.
See Plate Ih.

Fig. 13. A left valve showing the form ami proi)ortions ; redrawn from the specimen of tig. '1, plate 15.
Upper Helderberg grovij). Near Colnmbii.'s, Ohio.

PtEKINEA GKANDl.'*.
Page 91.
Fig. 14. A large left valve imperfect on the anterior end.

Upi>er Helderberg group. Lexington, Siott Co., Iml.

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PLATE LXXXIV.

ACTINOPTERrA ZETA.
Page 123.
See Plate 23.
Fig. 1. A large left valve of this species.

Fig. 2. A smaller example preserving the surface ornamentation.
Chemung group. Ithaca, N. Y.

ACTINOPTEBIA PUSILLA.
Page 117.
Fig. 3. A right valve of this species.

Hamilton group. Caimndaigua lake, N. Y.

ACTINOPTERIA DECUSSATA.

Page 111.
See Plates 17, 18 and 20.
Fig. 4. An enlargement of the surface of the specimen fig. 13, plate 18, showing the characters on another
portion of the shell than i-epresented in fig. 14 of the same plate.
Hamilton group. Western N. Y.

ACTIXOPTERIA TENUISTRIATA.

Page 120.
Fig. .'). A left valve showing the usual characters.

Fig. 6. An enlargement of the surface from another specimen showing the regular coarse rays with finer
rays between.

Chemung group. Ithaca, N. Y.

ACTINOPTEKIA IOTA.

Page 127.
Fig. 7. An imperfect left valve.

Chemung group. Ithaca, N. Y.

ACTINOPTERIA ETA.
Page 121.
Fig. 8. A left valve as obtained from an impression of the matrix, showing the characters of the surface.
Fig. 9. A small left valve.

Fig. 10. A right valve of this species, showing the form and character of the surface.

Fig. 11. A left valve of medium size, somewhat narrowed by pressure, showng the cai-dinal expansions
and surface markings.

Chemung group. Ithaca, N. Y.

ACTINOPTERIA PEUSTKIALIS.

Page 118.
See Plate 23.
Fig. 12. A right valve referred to this species.

Chemung group. Ithaca, N. Y.

ACTINOPTERIA KAPPA.

Page 128.
Fig. 13. A left valve.

Chemung group. Ithaca, N. Y.

ACTINOPTERIA PEROBLIQUA.

Page 116.

See Plate 19.

Fig. 14. The left valve of the specimen fig. 31, plate 19, showing the pallia! line and muscular impi-ession

with several umbonal scars.

Hamilton group. Cazenovla, N. Y.

ri.ATK I.XXXIV— Continueil.

ACTINOPTERIA AUUICULATA.
rage 121.
KifT. 1"). Tho left valve descrilied showing' the larg-c anterior ear.

Chemung group. TjawreneeinUe, Tioga Co.. Pn.

ACTIXOX'TERIA BOYDI.
I'agc 113.
See Plate 19.
Fig. 111. The left valve of the siiecinion fig?. 20, 2S, 29. plate 19. redva\vii to show the jiallial line ami
muscular impressions. ' ' ' ■" "

Hamilton group. Cazeiutvia, iV. Y.
Fi". 17. A small right valve showing the hinge characteiTi, pallial line and muscular impression. Thus
figure is the natural size of the specimen represented in figure 12, plate 19.
Hamilton group. Hamilton, Madison Co., iV. T.

AciIx\"Oi"XKi:iA XIIKXA.
Page 12.'j.
Figs. 18. 19. The right and left valves of the specimen described.
Chemung group. Ithaca, iV. ¥.

ECTENODESMA BIKOSTRATUM.

Page Hi.
See Plate 23.
Fig. 20. The left valve represented on plate 23, fig. 30, recb-awn to show the extent of the wings.
Chemung group. FranMin, Delaware Co., N. Y.

Ptekinea Cuemungensls.

Page 98.
See Plate 16.
Fig. 21. A large left valve of this species showing the form of the shell and the iriterruptejl rays with the
fine conceutinc strire of the surface.

Chemung group. Near Bath, N. Y.

Pterinea interstkialis.

Page 96
Fig. 22. An imperfect left valve.

Chemung group. Chemung iVoiroms, iV. Y.

Ptekinea coksimilis.

Page 100.
See Plate It!.
Fig. 23. A left valve showing the ligamental area, cardinal and lateral teeth, pallial line and muscular
impression. Some portions of the test are i-emaining on the lower half of the valve.
Chemung group. Tioga Co., JS". Y.

PtERINEA (VeUTUMMAJ lIEVElitA.

I'iige 101.

See Plate 24.

Fig. 24. The specimen represented on plate 24, fig. •>, redi-awn to show the absence of strong rays on the

wing.

Chemung group. Elmira, N. Y.

3SAMIIIILT[D3ff AlflQ- eiHIlgMIUlf (B (E-IEKBTCJIFl

Palaeontology of NYVolVPt]

?\r,if'[ySW

Chas Van. Benthuysen.& Sons, hih

PLATE LXXXV.

Ptychoptebia Thetis.

Pase 135.
Figs. 1-3. Three left valves showing' some variation in form and obliquity.
Fig. 4. A I'ight valve referred to this species.

Chemung group. Panama. N. Y.

Ptyciiopteria gibbosa.

Page UO.
Fig. 5. A left valve .showing the large anterior end and short wing, with the broadly gibbous body of the
valve. Chemung group. Warren, Pa.

Ptychop teria falcata.

Paj?e 13G.
Fig. 6. An entii-e left valve, showing the form and surface markings.
Pig. 7. A smaller example of the same valve.

Chemung gi'oup. Alleghany Spring.s, Warren Co., Pa.

Pttchopteria sinuoja.

Page l:iO.
See Plate 23.
Fig. 8. A left valve showing the oblique cardinal and latei-al teeth.
Chemung group. Warren. Pa.

PfiCIlOPTERIA El 'DOR A.

Page i:t8.
Fig. 9. A left valve of this species showing its elongate form.
Chemung gi-oup. Panama, N. F.

Ptychopteria et,oxoat.\.

Page 141.
Fig. 10. A carilinal view of a specimen preserving both valves.
Fig. 11. The ventral view of a smaller .specimen with the v.ilves closed.
Fig. 12. A large right valve of this species.
Fig. 13. The left valve of the specimen tig. 10.

Chemung gnuip. Panama, N. Y.

Ptychopteria Sao.

Page r.'.-i.
See Plate 23.
Plf;, 14. A small left vahe.
Fig. 15. The left valve of a larger example.
Fig. 16. A specimen of medium size.
Fig. 17. The cardinal view of a small individual, showing the prominent beak and umbo of the left valve

as compai-ed with the right.
Fig. 18. The \-entral view of a specimen preserving both valves.
Chemung group. Panama, N. Y.

Ptychopteria Spio.

Page 137.
Fig. 19. A left valve of this species.

Chemung group. Panama, W. Y.

Ptychopteria .spatulata.

Page lU.
Fig. 20. A left valve showing its large size and broad elongate form.
Chemung group. Warren, Pa.

I'LATK LXXXV— Cniilinucd.

Ptychoptekia Beecheiu.

P&ae Hi.
Kii;. 21. All entire li'ft valvo sliowiiij;' its "-ibboiis anil arcnate form,
l-'iff. 22. .V rij.'-ht valvo of this sjiocies.

Chemung- group. Jrarnti. Pa.

Ptyctioptekia I-AIA.

I'aye lir,.
Fig. 23. An entire left valvi'.

F\g. 24. A larger left valve.

Fig. 2"). A right valve showing its comparatively strong alar I'ol.l.
Chemung group. If'aireit. Pa.

Ptycjiopteria alata.

Pajro 139.
See Plate 23.

I'ig. 20. The posterior half of a left valve, showing the subangnl.u- posterior slope.
Chemung group. >ia1amania, N. T.

Ptychoptkria Eucrate.

Page 133.
See Plate 23.
Fig. 27. A left valve of this species.
Fig. 28. A small left valve.

Chemung group. Pannina, N. Y.

PtYCHOPTERIA (lAI.f.NE.
Page 1«.
Fig. 29. A left valve flattened by pntssure.

Fig. 30. A smaller left valve preserving the normal proportions of the species.
Fig. 31. The right valve of a specimen preserving both valves.
Chemung group. JVarrea, Pa.

Ptychopteria Thalia.

p.i.tfc us.
Fig. 32. A small right valve.

Fig. 33. A meilium sized left valve showing the short gibbous form of the shell.

Chemung group. Alleghany Sjirings, Warren Co. . Pa .

PlY-CnOPTERIA TRIGONALIS.

I'a^'C- 140.
Fig. 34. A small left valve showing the form and chai-aeters of the species.
Fig. 35. A large imperfect left valve.

Chemung group. Panama, N. Y.

Ptychopteria Vanuxemi.

Page 151.
Fig. 3C. A portion of a large left valve, showing the peculiar form of the bocly and the surface charactera.
Chemung gi'tuip. IVarren, Pa.

Ptychopteria lobata.

Page ISO.
Fig. 37. A left valve showing the short form of the valve .and the strong alar plication.
Chemung group. IVarrni, Pa.

Ptychopteria peui.ai \.

Pajt8,147.
Fig. 3.S. A right valve of this species.

Fig. 39. A left valve showing the form and surface markings.

Chemung grouj). Warren, Pa.

ssEss^jxTpji- 3uiin!:p.

Paiae ontology of N.T.yolVPt.I.

Plate LXXXV

^

15

21

"V

S2

r

J

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" iriLtnuns del

?h.-^T .1':-

PLATE LXXXVI.

Glyptodesma erectum.

, Page 153.
See Plates 11, 12. 13, 25 and 87.

Fig-. 1. A left \alve of a small individual.

Hamilton group. FahinJ!, Onondaga Co., N. Y.
V\g. 2. The light valve, as seen lying- within the left, showing its form and comparative size.

Hamilton group. Cayuga lake, N. Y.
Fig. 3. The hinge of a specimen, showing the striated ligamental area and strong cardinal folds. ■

Hamilton group. Delphi, Onondaga Co., N. Y.
Fig. 4. A small left valve with small anterior wing and very large posterior wing, also showing one of the
olilique lateral teeth.

Hamilton group. Cayuga lake, N. Y.
Fig. 5. The anterior profile view of a very perfect specimen retaining the test, showing the comparative
convexity of the valves.

Hamilton group. Pratt's falln, Onondaga Co., N. Y.
Fig. 6. The left valve tig. 8, phitt; 11, redrawn to show the ligamental area, lateral teeth and muscular
impression. The tubular markings around the mai-gin are the remains of the excavations
made by boi-ing sponges.

Hamilton group. Cazeiurvia, N. Y.
Fig. 7. A large right valve, showing the ligamental area, pallial line, muscular impression and umbonal pits.

Hamilton group. Gilberts-inlle, Otsego Co., N. Y.
Fig. 8. A left valve presenting the same internal charactei-s as the precetling, together with two strong
lateral teeth.

Hamilton group. Albany Co., iV. Y.

Gl.VrTODESMA OCCIDENTALE.

Page 157.
See Plate 15.
Fig. 9. The Mi)ecimen of iig. 12, plate 15, redrawn to show the erect form of the body and extent of the
posterior cardinal expansion.

Upper Helderberg gi-oup. Falls of the Ohio.

mAMSILTEirf [E-IEHETIJIP.

-itologyofNYVolYp-

Flaie ISS?.T

C E Beecher, del

Chas YaaBenthuyseatScSons.lith

PLATE LXXXYII.

Glyptodesma erectum.

See Plates 11, 12, 13, 25 and 86.
Fig-. 1. The interior of a specimen -nath the valves thrown open, showing the comparative size and foi-m
of the valves, the hinge characters and muscular markings.
Hamilton group. BelpM, Onondaga Co., iV. ¥.
Fig. 2. The internal mould of a left valve, showing the pallial line, muscular impression and small tuliei--
cles in the inter-pallial area, I'epresenting the points of attachment of small umbonal muscles.
Hamilton group. Pratt'x falls, Onondaga Co.. jK. Y.
Fig. 3. An internal mould of a right valve showing the anterior and posterior adductor muscular impres-
sions, and a small Crania atfaclied to the wing.

Hamilton group. Pi-om a boulder,. J-Yaverly, Tioga Co., N. Y.

..<M. ,^^^^^vll .'jc,
PaL,EOPINNA rLABELT,A.
Page 2)0.
See Plate 25.
Fig. 4. The left valve described, showing the form of the shell and a single groove along the hinge.
Oriskany sandstone. Schoharie, N. Y. . , ^ ■sviif/ ii'.i A

PtERONITES IXOl'TATUS.
Page 239.
Fig. 5. A left valve showing the form of the shell. The scar on the post-umV)onal slope was produced by
the attachment of a Crania.

Chemung group. Mamifidd, Pa.

PLATE LXXXVII— Continued

Myiilarca fibristkiata.

Page '26*.
See Plate 33.
Fig. H. The left valve tig. 6, plate 33, redrawn to show the true form of the anteiior side. This species is
the only radiate form of the genus yet described and more perfect material may show
charactei-s which would exclude it from Mytilarca.
Yellow sandstone. Burlington, Iowa.

Mvrii,.\i{f"A oinBOSA.

Pago 'i63.
See Plate 33.
Fig. 7. The left valve fig. 20, plate 33, redrawn to show more clearly the entire form of the valve.
Chemung group. Napoli, Caltaraugus\Co., N. T.

Mytilarca (PLExuojiyriLus) omformis.

Page 255.
See Plate 31.
Fig. 8. The upper portion of a right valve showing tho. oblique po.stenor teeth of the hinge.
Hamilton group. York, Limngslon Co., N. T.

MoDioLA (Mytilop.s) METELLA.

P-ige 2G8.
See Plate 33.
Fi". 9. A right valvi' showing the form and proportions of the shell.
Chemung group. Warren, Pa.

Myhlarca (Pi,ethomytilus) arenacea.

Pago 253.
See Plate 30.
Fig. 10. A left valve.

Schoharie grit. Schoharie, N. Y.

Mytilarca Occident a lis.

Page 263.
See Plate 33.

Fig. 11. The left valve fig. f>, plate 33, redrawn to show the form of the beak and anterior side. The
outlines of this one and of fig. 6 are partially restored from other specimens and represent all
that can be determined from the imperfect material.
Yellow sandstone. Burlington, Lrwa.

GOSSELETTIA TRIQUETRA.
Page 26.1.
See Plate 31.
Fig. 12. A large right valve of elongate form.

Hamilton group. Fidtonham, Schoharie Co., N. Y.

Mytilarca (Pletiiomytilus) Knappi.

Page 256.
Fig. 13. The right valve described, .showing the form of the shell and the striated ligamental area.
Hamilton group. SkaneaUles lake, N. Y.

[DMIISM^2>IT SAHIDgTElIflE T© SHIEM^ll© ©ia©TIJF»

Plate IJOOC'/l

Chas ^■.'■'x.i fJrJttauysentxScr.s. lifli

PLATE LXXXVIII.

LeIOPTERIA COiN'KADr.

Page 159
See Plate 20.
Vig. 1. A left valve rshdwing' strong coneenti'ic undulations.

Hamilton group. LronardsvlUe, Madison Co., iV. Y.
Fig. 2. A small left valve.

Hamilton groujj. Caiuindaigua lake, iV. Y.
Fig. 3. A large left vah-e imperfect on the anterior side. This tigiire is given in i-on-eftion of tig. 4. phite 20.
Fig. 4. An imperfect right \'alve.

Hamilton group. SkanedtelfK lake, N. Y.

Leiopteria Dekayi.

Page 164.
See Plates 19 and 20.
Fig. 5. The internal njould of a specimen preserving both valves, and showing the vertical plate just
anterior to the beaks.

Hamilton group. F'uUunhaiii, iScho/iarit Co., N. Y.
Fig. 6. A large left vahe with the wing partially I'estored.
Hamilton group. iSclioharie Co., N. Y.
Fig. 7. An enlargement of the surface on the umbonal slope of the specimen tig 10.
Fig. 8. A left valve jiresei-ving the sti-iated ligamental area.
Fig. 9. A cardinal view of a portion (.f both valves showing the deep sulci anterior to the beaks.

Hamilton group. Ftdtonham, Sc-lioliarie Co., N. Y.
Fig. 10. A small left valve showing the fine concenti'ic striae of the test.
Hamilton group. Delphi. Onondaga Co., N. Y.

Leiopteria Torreyi.

Page 174.

See Plate 22.
Fig. 11. A left valve of this species.

Chemung group. Paimina, CJ/autauqaa Co., N. Y.

Leiopteria Troosti.

Page 1()7.
Fig. 12. A left \alve showing the form and surface characters.
Fig. 13. A portion of the surface enlarged to thi-ee diameters.
Hamilton grouj). ScJioJiarie Co., N. Y.

Leiopteria Gabbi.

Page 16U
Fig. 14. A left \alve showing the form and sui'face characters.
Hamilton group. Cayuga lake, N. Y.

ri.ATlO I.XXXVIII— Coiitiiiuoil.

Lkiopticria Sayi.

I'ase Ki.
Viff. 1") All iiiiiii'ifcrt left valvi! preserving very line c-oncentric lines.

llainilton gTOiip. NaHmi's Laitiling, (Jayuga lake, A. 1'.
I'if;. K;. The left val\e uf a specimen preserving' lii tli valves, showing' the extent of llie win- and general
form of the shi'll. i i i

Hamilton gron]). LhiiwjstoH Co., iV. Y.
lijr. 17. 'I'lie rij,'ht valve of a larfje specimen with the valves partially opened.

Hamilton {,'ronp. Bdloiia, iV. Y.
V'li:. 18 A lei t valve \ ireservinf,' the auricle ami wing nearly entire. The Vioily of the .shell has l)een subjected
to pre.ssure and distorlion in the soft shale and does not represent the true torm and obliquity.

Hamilton group. Belloiia, N. Y.
Fig. l'.». An imperfect left valve as preserved in a coarse gi-it.

Hamilton group. Leonardsville, MndUon Co., iV. Y.
Fig. '20. A small left valve of consideralile t;ibbosity.

Hamilton group. iScltoharie Co., IV. Y.

Leiovteria Gkeeni.

Page 160.
See Plate 20.
Fig. 21. A large left valve. The figure is restored on the l)eak and anterior side.

Hamilton group. Bellona, Yates Co., N. Y.
Fig. 22. An imperfect right valve.

Hamilton group. Canandaiffua lake, N. Y.

LeIOPTERIA BlGSBYI.

Page 1U5.
See Plate 20.
Fig. 23. A small right valve referred to this species.
Hamilton group. N. Y.

Leioptekia Leai.

Page im.
Fig. 24. A small left valve.

Fig 2.5. A larger irapei'fect left \alve associated with the jireceding.
Hamilton group. SchoTiarie Co., JV. Y.

Leiopteria jMixchelli.

Page IfiG.

See Plate 20.

Fig. 26. A lar.e imperfect left valvi^ ius obtained from the impression of the exterior of the valve in the

matrix.

Hamilton giiiiip. HcJioharle Co., N. Y.

Leiopteria Rafinesquii.

Page 101.
See Plates 15 and 20.
Fig. 27. A nearly entire left valve showing the form and the strong concentric undulations.

Hamilton group. Belloiia, N. Y.
Fig. 28. Aright valve referred to this specieS. The specimen is impei-fect at the beak and extremity of
the wing.

Hamilton group. Lnonardsville, N. Y.

Leiopteria linquiformis.

Page 173.
Fig. 20. A left valve, denuded of the test, showing the general form with the jiallial line and muscular
imjM'essioii.

Chemung group. Aorth of Bing/ia niton, N. Y.

lEAMiaEaTElM AMIS OmiEMiIJMCS ©MrflUJIFi

Pal csontol ogy of 1) YVolV'Pt J

xtelXXXM.

E. Emmons, del.

Chas Van.Benthu--7senicSoTis, liih

PLATE LXXXIX.

a — Spinifera.

Leptodesma spinigerum.

Page 177.
See Plate 21 .
Fig. 1. A li'ft valve preserving' the siiiiiifiuMii extension of the cardinal ani^U^.
Chemung- g-roup. Clionnnrj river, ahoxv Ehidra, N. Y.

Leptodesma longispinum.

Page 179.
See Plate 21.
Figs. 2, 3. Two left valves varying slightly in form and surface markings.

Fig. 4. A large imperfect right valve preserving a p<n'tion of the finely striated ligamental area.
Chemung group. Near Elmlra. N. Y.

Leptodesma Shumardi.

Page isn.
Pigs. 5, 6. Two left valves varying somewhat in foi-m and proportions.
Chemung group. Niar EJmirn, lY. Y.

Leitodesma potens.

Page 188. •

See Plates 21 and 22.

Fig. 7. A nearly entire right valve of this species.

Chemung gi'ouji. Near Oknn, N. Y.

Leptodesma kobu.stum.

Page 181.

See Plate 21.
Fig. 8. A large left \-alve.

Chemung group, t>teiihen Co., N Y.

I'l.ATE I.KXXIX— CoiiUiiued.'

Ijl.rrOUESMA MOKTONI.
Page ISO.
Sec Phiti; 21.
Fig-. 9. The specimen tig-. 81. plate 21, reiirawn to .show the form of the body and size of the wing-.

Chemimg f^roui). Porlnllle, Cattaraugus Co., N. Y.
Pig. 10. 'I'ho right valve tig. 32, plate 21, redrawn to show the pi-opiir form and charactei-s of this valve.

Chemung gronp. Portville, N. 7.
V\g. II. A cai-dinal view of a specimen, pi'eserving the valves partially njien and .showing their comparative
size. Chemung- ^•ouii. TAttle Genesee, N. T.

I^KITODESMA BiLLINGSI.
Page 1!>2.
Fig. 12. A large loft valve.

Chemung group. Panama, iV. Y.
Fi"-. 13. A right valve agreeing in form and proportions with this species, l>ut referred with some doubt
on account of the geolog-ical po.sition.

Chemung group. Near Elinira, N. F.
Fig. 14. An imperfect left valve of somewhat different form.

Chemung group. Panama, N. Y.
Fig. 1.'). A small left \-alve from the same horizon as the specimen tig. 13.

liEPTODES-MA LEPIDUM.

P.lgc 19.i.

See Plate 21.
Fig. 1(5. A li'ft valve showing the form and surface markings.
Chemung group. Tinr/n Co. , Pa.

Leptodesma Aga.ssizi.

• Page If^-J.

Figs, n, 18. Two left valves showing the chara<;teristic foi-ni of this species.
Fig. 19. A small right valve.

Clicmung grouji. Ifear Elmira, N. Y.

Leptodesma Stephani.

Page 194
Fig. 20. A right valve.

Figs. 21. 22. Two left valves showing the usual characters of the species.
Chemnng group. Bradford, Pa.

LkI'TODESMA DI.SPARILE.
Page 180.
See Plate 2.5.
Fig. 23. A right valve showing the form and ornamentation.
Fig. 21 A small left valve preserving the spiniform process.
Chemung group. McKean Co., Pa.

(QMISMITEJIf © ©mOUJIF,

Pal ae c ntol 0 gy of N Y^^1V: Pt 1

Plate liSXK

-•v, ■ ^^nrr^^

^V

X

■SW'"'"-^'

^^

if

,,f*'^*>»«E

^'SiT

■%

■i

'^^s^„

ft

Z jLiumGns, dej.

a5 \ari-Beath.uyseaccSoii;i, liii.

PLATE XC.

b — Umbonata.
Leptodesma Medon.

Page l'J7.
Figs. l-;i. Three left valves varying- somewhat in form and size.
Fiy. 4. A right valve of this species.

Chemung group. Lawreiiceville. Tioga Co.. Pa.

Leptodesma Mentor.

Paste '20.5.
See Plate 23.
Fig. 5. A left vah'e of the usual form.

Chemung group. Smethport, Pa.

Leptodesma Cadmus.

Page 'JOl.
Fig. 6. A left valve of a specimen preserving both valves partly opini.
Chemung group. Smithfield, Bradford Co., Pa.

Fig. 7. A large left valve.

Chemung group. jStcnheii Ca., N. Y.

Leptodesma Orodes.

Page 206.
See Plate 25.
Fig. 8. The specimen fig. 9, plate 25, redrawn to slinw the true form of the liudy ami wing.
Chemung group. Smethport. Pa.

Leptodesma umbonatum.

Page 19S.
See Plate 22.
Fig. 9. The specimen tig. 13, plate 22, redrawn to show its proper form nnd projiortions..
Chemung grouii. Tiiv.nly Mile creek. Clmutauqua Co.. N'. Y.

Leptodesma umbonatdm, var. deprkssum.

Page 199.
See Pl.ate 22.
Fig. 10. The specimen fig. 14, plate 22, redrawn and restored in outline.

Chemung group. Napoli Centre, Cattaraugus Co., N. Y.

Leptodesma Creon.

Page 'la-i.
Figs. 11. 12. Two left valves showing .slight differences in form and surface markings.

Fig. 13. A right valve.

Chemung group. Lawreiu-eriUe, Tioga Co., Pa.

Leptodesma Loxias.

P.age '204.
Fig. 14. A left valve of this species.

Chemung gronp. LawreneevUle, Tioga Co.. Pa.

Leptodesma Demus.

Page 203.
Figs. 15, 1(5. A right and left vah'e showing the usual form of the shell.
Chemung group. Lawrencevillr. Tioga Co., Pa.

c — Rostrata.
Leptodesma extenuatum.

Page 207.
See Plate 22.
Fig. 17. The specimen fig-. 23, plate 22, redrawn to show the entire form and proportions.
Fig. 18. A right valve with the test removed sho\ving the pallial line and muscidar impression.
Chemung group. MansfieUl, Tioga Co., Pa.

I'l.ATK XC— Coiitiiiuc<l

Lei'touesma IIkctoh.

I'lvgC 209.
Kijfs. lit. lid. Tlif U'lt anil lifrht valves iif this sppciMs The lig-ht valvi' pi-eserves the imllial line ami mus-
cnhir iiiiiiifssion.

Chi'iniiiifr ffi""!'- Ciinhm, ISriidforil I'n., Pa.

Leptodesma ("mtus.

I'agc 210.
Kig. 21. A left viilve. .showiiijr the f(irm and .sui-facn markinjr>-
Cheniuiiff grroup. Mansfiuld, Pa.

Lkitooesma Corydon.

Page -1^.
Fij,'. 22. The left valve descnbe<i.

Chemung grouji. Maiusfielrl , Pa.

Leptodesma Orcu^.

Pajre 21.').
Fig. 23. A left valve.

Chemung gi-diij). Mansfield. Pa.

Leptodesma truncatlm.

Page 211.
Figs. 24, 2.1. A rig-ht and left valve of this species.

Chonuing group. Manxfield, Pa.

Leptodesma ai.aiim.

Page 21S.
Fig. 26. A loft valve.

P'ig. 27. A light valve pi'eserving the pallial line and nius(-idai- impression. The apparent anterior mus-
rulnr scar is due to a defect in the shell, as the pallial line can lie traced to a point jn.st anterior

to the beak.

Chemung group. Coiitoii, Bradford Co., Pa.

TjEptodesma Pelops.

Page2U.
Figs. 28, 21t. Two left valves varying slightly in form and ]>roi>ortious.
Chenmng group. MansfirUl, Pa.

Leptodesma Orus.

Page 219.
Fig. :^0. A left valve showing the foi-m and surfa<:e markings.
Chemung group. Mnv.ifi^'UI, Pn.

Li'.ptodesma Nereus.

P.ige 217.
Fig. 31. A moidd of an imiierfeei right valve lying in the left valve, showing the oblique lateral teeth, the

pallial line and museidar impression.
Figs. 32, 33. Two left valves: tig. 33 shows an oblifpie Lateral tooth corresponding to the two in the right
valve rciu-esented in figure 31.

Chemung grouji. Man.-ifield, Pa.

Leffodesma Lysander.

Page 216.
See Plate 22.
Fig. 34. A left valve, showing the form and regular concentrii' stria- of the surface.
Chemung group. MaiiafitM. Pa.

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PLATE XCI.

c- — Rostrata.
Leptodksma Biton.

I'age C22.
Fig. 1. An imperfect left valve of this species.

Cliemmig- group. i>^imth nfjSmettqjo-H, Pa.

LePTODESMA ALIFORME.

P:ige -'-il).
See Plate 22.
Fiff. -. A la rye right valve ^showing; the pallial line awl muscular impression. This figure is given in
correction of fig. 28 of plate 22.

Chemung grouj). Avyelha, N. Y.

Leptodesma kujje.

P;ise-221.
See Plate 2.").
Fiij. 'A. The left \alve described. This figure is given in correction of tig'ure 12, plate 2;").
Chemung group. Ntar Sinethport, Pa.

Leptoijesma Jason.

Page 213.
Fio-. 4. \ left valve of the medium size.

Chemung group. Canton. Bradford Co., Pa.
Fig'. ."). A I'ight valve somewhat imperfect, but pi'eserving the form of the body and cardinal expansions.

Chemung group. Near Mansfield, Pa.
Fig. 8. A smaller rig-lit valve associated with the preceding- '

Leptodesma Lesleyi.

Page 223.
Fig. 7. A large left valve showing the foi-m and sui-face markings.
, ' Chemung group. Susquehanna Co., Pa.

Leptodesma aviforme.

Page 2-24.
Fig. 8. An imperfect left valve.

Chemung group. Tioga Co., Pa.

d — Patulata.
Leptode.sjia flaccidum.

Page 2-25.
Fig. 0. A left valve showing the charactei-istic form of the species.
Chemung- group. Laiorenceville, Tioga Co., Pa.

Leptodesma patulum.

Page 226.
Fig. 10. An imperfect left valve.

Chemung group. Mansfield, Pa.
Fig. II. A right valve.

Chemung group. Ma'mfield, Pa.",

e — Arcoidea.
Leptodesma aecifoeme.

Page -229.
Fig. 12. A large left valve.

Chemung group. Mansfield, Pa.

PLATE X(;i— Coiitiimod.

Lkitodesma Maclurii.

Pago 228.
See Plate 25.
Fip. i:i. A \iirij;ii left .valve nf tlii.s species. This ti^rnre is f^iveii in correction of ti^. 18, plate 25.

Chemung- group. Near Smetliport, Pa.

V\g. 14. The i-ig-ht valve tig-iired on plate 25, tig. 8, i-edrawn to coi-rect the outline.

Chemung group. Near fiinethport. Pa.

LePTOUESMA gUADKATUM.
Page -233.
Fig. ir>. Till' left valve described.

Chemung group, fiteuben Co., N. Y.

Leptodesma PROPINQOUM.

IPagu Ail.
Fig. l(i. A nearly entire left valve, showing the fonu .uid cliararters of the .species.

Chemnng group. Mansfield, Pu.
Kig. 17. A similar right valve.

Chemung group. Manxfmld. Pu.

Leptodesma I'haon.

Page 230
Fig. IS. .\ li'ft valve- (if this species.

Chemung grouji. Man-tfield, Pa.

Leptodesma Liciias.

Page 232.

.See Plate 21.
Fig. li". A small left valve.

(Chemung group, fiteuhen Co., N. ¥.
Fig. 20. The li-ft \alve figured on plate 21, tig. 37, redi-awn to correct the outline.

Chemung group. P/nlip.iburg, N. Y.

f — Mytiloidea.
Leptodesma acutirostrum.

Page 234.
Pig. 21. The left valve described, showing the form of the body and the acute; anterior end.
Chemung group. Warreti, Pa.

Leptodesma mytiliporme.

Page 23.').
See Plate 25.
Pig. 22. The right valve figured on plate 25, fig. 7, redrawn to correct the outline and the form of the body.
Fig. 23. A small left valve.

Fig. 24. A view of left valve given in correction of lig. 11, plate 25.
Fig. 25. Two left valves as preserved on the surface of a piece of sandstone.
Chemung group. Road from Olean to Smethport, Pa.

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PLATE XCII.

LiMOPTEKA CANCKLLAl A.
Page 244.
See Plate 26.
Fi^'s. 1, 2. Two small left valves differing- in the frequency of the radii.

Hamilton group. Falls of the Ohio.
Fiff. 3. The left siile of the orifri""! specimen, redrawn to show the restored outliin', the pallia! liiu- and
niuscidar impression.

Hamilton g-roup. Falls of the Ohio.

LiMOPTEKA MACROPTERA.

Page 246.
See Plates 24, 2G. 27, 28 and 29.
V\g. 4. A small g-ibbous left valve showing' numerous tine radii.

Hamilton ^i-oup. Delphi, Onondaga Co., N. Y.
Fig.*. .1. fi. The right and profile vicw.s of a small specimen showing the form and convexity of the shell.

Hamilton group. Pratt's falls, Ommdaga Co.. N. Y.
Fig. 7. An outline of a large right valve.

Hamilton group. Schn/iarie Co., N. Y.
Fig. 8. A left \'alve preserving very marked surface charactei-s.

Hamilton group. Delphi, N. Y.
Fig. 9. .\ light valve showing the marked radii on the unibonal region and their gradual obsolescence
toward the margin of the valve. The hinge preserves the striated Ugamental area, the
ohlifpie lateral teeth and three obscure canlinal folds anterior to the beak.
Hamilton group. Pratt's falls, Onondaga Co., N. T.

LiMOPTERA OBSOLETA.

Page 249.
See Plates 2(3 and 2!».
Fig. 10. A large left valve, showing the form and surface charactei-s and a iiortion of the ligamental area.
Hamilton gron)!. Pratt's falls, Onondaga Co., N. T.

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