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PALAEONTOLOGY:

Vol. V. Paet I.

LAMELLIBRANCHIATA

TE33ZT J^Ji>rT> I»Ili-A.TE3S-

CONTAINING DESCRIPTIONS AND FIGURES

OF THE

MOIsrOMY^RI^

OF THB

UPPER HELDERBERG, HAMILTON AND CHEMUNG GROUPS.

Br JAMES HALL,

8TATB QEOLOQI8T.

ALBANY, N. Y.:

CHABLE8 VAN BENTH0T8EN & SONS.

1884.

Statb ok New York, >

Albaxy, February 15. 1SS4. )

Piiblwhe^l under tho HUpervifuon of the Trwi\«HiH of the State Museum of Natural History, pursuant to

chApt/;r 3{i5 of the LawH of 1883.

208884

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 the PALiEONTOLOGY 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 Palaeon-
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 Geologist.
Albany, February 15, 1884;

TABLE OF CONTENTS.

Page.

DEDICATION iii

TABLE OF CONTENTS v

ADDENDA AND CORRIGENDA vi

PREFACE vu-x

SYNOPSIS OF THE GENERA xi-xiv

INDEX xv-xviii

DESCRIPTIONS OP SPECIES 1-268

aviculopecten 1-40

Lyriopecten 40-57

Pterinopecjten 57-81

Crenipecten 81-90

. Pterinea 91-103

S. G. Vertumnia 104-107

actinopteria 107-128

Ptychopteria 129-152

Glyptodesma 153-157

Leiopteria 158-174

Leptodesma 175-236

Pteronites 237-239

Pal^opinna 240-241

Ectenodesma 242-243

Limoptera 243-251

Byssopteria 252

Mytilarca 253-264

8. G. Plethomytilus 253-256

GOSSBLETTIA . . 265-266

MoDiOLA, S. G. Mytilops 267-268

PLATES AND EXPLANATIONS i-xxxiii and lxxxi-xcii

ADDENDA AND CORRIGENDA.

Page 14, add to reference of A. lactus, plate 81, fig. 5.

Page 30, for A. elongatus read A. cdsua.

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

Page 74, Une 2, for LXXXI read LXXXII.

Page 82, line 3, for P. crenulaius read C crenttlatus.

Page 114, line 23, for recticulata read reticulata.

Page 157, line 11, for anterior read posterior.

Page 167, for A. Bigsbyi read L. Bigsbyx.

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

Pag^s 186 an<l 238, lines 4 and 7, respectively, for Alleghany read Cattaraugus.

The names Philipsburgh and RockN-ille, are localities referred to in the earlier Geological Reports,
from which many fossils were obtained. The former (Philipsbnrgh) is now known as B(»Iniont. Rockville
was a settlement near the mouth of Rock creek on the Genesee, in the township of Belfast, « hiring 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 Pal^ont(Jlogy 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 work 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 descriptions and figures of the species under the genera included
in the accompanying synopsis, belonging to the families, PectenidaB, PterinidaB,
AviculidaB, AmbonychidaB, and MytilidaB.

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 Reports 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
nimiber 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.

During and since this period the writer has made extensive collections of
these fossils, both 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, the writer personally 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 1865, 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 begim in
1870, and owing to the author's constant occupation in duties pertaining to the
State Museum, the supervision of the drawings and lithography 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 accordance with the
arrangement upon these plates. In the course of the work it has l)eeii found
necessary to reproduce, in a more correct form, with illustration of the parts,
some of the figures of the earlier plates, as well as to give many additionjil 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 other. 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, aflFects 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 before 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

X PREFACE.

I text and the later plates of this volume the author cheerfully acknowledges the

very valuable assistance rendered by Mr. Charles E. Beecher.

Of the mechanical and artistic execution of this work I may speak with
commendation. 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 ; and I hope the present volume may be
regarded as an acceptable contribution to our 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
Skaneateles, 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, February, 1884.

xii SYNOPSIS OF THE GENERA,

Pemopecten* Winchell. Shell like Pecten. Hinge with a central cartilage pit
and a crenulated hinge-plate on each side below the hinge-margin. This and
the following genus appear to be more nearly related to the genus Pecten than
to Aviculopecten.

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 transverse 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.

Pterinopecten, 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 incquivalve, 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
ornamented with rays. Examples, pi. xv, figs. 1-21 ; pi. Ixxxiii, fig. 12.

S. g. Vertumnia, 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 broad
striated ligamental area and strong cardinal and lateral teeth. Right valve
sub-convex. Surface with fine rays. Examples, pi. xvii, fig. 26 ; pi. xviii, fig.
13 ; pi. xix, fig. 3.

Ptychopteria, Hall. Differs 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, page 81.

xiv SYNOPSIS OF THE GENERA.

of the shell. Wing and hinge extended posteriorly. Test marked by concen-
tric striae. Example, pi. xxii, fig. 26.

PalcBopinna, Hall. Shell similar in outline to Pinna, gaping in front. Test
marked by fine nidiating lines. Both* more convex and test with finer rays
than in the ordinary Pinna. . Hinge-line simi)le. Example, pi. xxv, fig. 18.

Edenodesma, Hall. Resembles Glyptodesma in outline, except that the ante-
rior wing is more produced and both wings more acute at their extremities.
Test ornamented with rays. Example, pi. xxiii, fig. 30.

Byssopteria, Hall. Shell erect, equivalve. Alate posteriorly, truncate, and
with a nasute projection in front. Surfiice radiated. Examples, pi. xxiii, figs.
21, 22; pi. Ixxx fig. 11.

Mytilarca, s. g. Plethomijtilm^ Hall. Equivalve, mytiloid, gibbous. Shells
with a finely striated ligamental area. Posterior side subalate. Hinge-line
transverse. Lateral teeth snudl, ol)lique ; no cardinal teeth have been observed.
Test with concentric striae. Examples, pi. xxx, figs. 5, 7 ; pi. xxxi, figs. 2, 3, 7.

Mytilarca^ Hall. Shell equivalve, inequilateral and mytiliform w^ith 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 nulii, with a single
known exception. Examples, pi. xxxii, figs. 9, 17, 19, 20.

Gosselettiaj 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. MytilopSy 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. Beaks terminal. Examples, pi. xxxiii, figs. 16, 17 ; pi. Ixxxvii,
fig. 9.

PACK.

Avlculopeclon ipiotti?. Htdl. . . 33, ai
A. In-lKniB, BaU 34. S-l

L. Mllrholll, flaH

A. laiiliis. BaU, 14

A. orUlnilarU. tfeCtv ti

A. orlilculntuN, McCvt, .42
A. Orttet. JIM. . 11. 12

A, ,>rnalin. HWi »5, 81. :»

A. pnlultiH, //oU 84. 2R

A, iw.^lciiiformU,l(7OTl«rrfl iTnU. S, 4,8, ft. 12

A. l-bmrn.. flhtl 10

A. pIvniiK, Sdll, ..... 81
A. i»\nrep>, iCMrad\ B<U1. . l.S, n, «. fl. 11. 12. ti
A. nTiletui, Hull. . 11. 12
A. rugBBtrialus. BaU. ■ . .14. IB, 17. 1-. HI
A. Sn-i.|i,-k-"n^i-,(jlftei|flhU. . . 1. 1
A, -im.n.i,,^. «„;/. . . . 3, 1, 14. ij. IS. -a

A. slgnatu.-. //n«. 80

A. Miuamn, fiolj. 91

A. atrlam-, Bo/I a«,i4, 30

A. leaai^, JIalt, . «. SB
A. unrf.i)ff(u», JIttll 7-2

A. mae).M,-M<.-v\L «S

A, aTtniiicFiPD in<'iilluii. RaU, .30
A. [I'lorinoi«.ohMi?) invaliiliu. ffn/J. . 31

A. iP. ? ) lorminnli^. flnU, . 39

BrSSOPTERIA, flilJI 252

B. rncllBtn. BaU, 8S9

Cbknipectkh. //o'j, :ll. ei, 90

C. tanp\as,BaU 81, E3

C. crcnulotus, ffotl. 81, 88, HCt. K4, KG

C. Kli.hor,//«U. 80

C. . imiialltiu. BaU 83

C. I^nn, //oH, 88

C. llrnluB, BaU B8, 81

C. mlcroiilcran, floU, . . 83, K7

C. olHolclu*. BaU. to. 84

C Win<'lii.-lli.(Ar«ctl/rAU 89

C. (/-(rftnl ir(ntA«)((.lUpnkl llnll. B)

ECTFNOnES)lA,//fliI 242

E. blro«tratum,ffoW 849

1. Omni, ffolt,

1. RaOnei-iuii. ffn«. 161,165,
1., Miyi, //oil. ... 168,
1. Tnn«rl, fliiH. .

I. Troo»tl. ffidi.

l.EiTOOEiiUA. Hall. . vs. 17.-.. ait.

I. AKn*.Bi. floi/

1,. nllfnnne, Hail. . . * . . ' .

I.. J.vin.rm(.,*/;aH.'

L, iti'rti. y^a

I-. Illlllll|t»l. BaU. ...
t. KHan.Batt,

1.. Ciirt,nu^. Batt

L CIU.w.Ha«, ... 810.

I,. U.iryii..ii, fliiH 818,

L. (roon, Ha« «09, 2ul.

I.. r-mn-, ll.ilt. . . 803,

I.. .Ii-|. :..]],., Il.'il

I.. ..v!..„.,:ilni" fl.M. . . 801,2111.211,214,

I- lli^.'.i.liji,, ;;„(/ <«B.

I„ U^t^T.HaU, . . I!«.a00,

1.. Jason. /ftM,

L. loiiiiliim, //aM. . . 1B5,

I,. Lotleyi, /7oK.

1., Llclin-, ffflii, . 204, -iW, 839.

1-. [^jilft*. flh/I, .

L. L.vMQ<lcr. flbU. 21.-., 816.
U Ma,liirii. flWI. , . 2U7.223.
t.. UaVcellonw. ffali. . .

L. UalhPri. T/oH i»3,

L. Mwlun, ffali.

L. Ucnior, ffnn sob,

L. Hoitftul, //oU. . . IH2 1X9

I„ inyliim.rnic. /TaK.

L. nBvirorme. floK

Ultftiidehha, BaU, .... lAU, 11,1
G. frftam, (Conrad) Ball. . . 103, 157

<i. cn-Plum vnr. obliqauni, /ToB. . lOB, 158

G. otciik-iitalr, HaU 101

GOiiiiELKTTi.t. Bamit, .... 26,1. 2riH

<i. retii»i, Ball. 966

U. «rU,«ptra. Conrad > HaU. 966, 26.1
iHocfranHil Clicm<iiigniiii.CoBni-\, . . . .MS

/. ^V^i'.--""""! ■^•^

Jiuil™lr.np™iia».l/J-OrW^lFi. . «

IjlIOrTEIMA, //oil 12». ISK

L IIiffsli.vi,J/<.K, 16fi, IC

I.. C™irn.li, BaU. . . IM, IBP. 1«5

L Dvkavl,//<iM 164,172. 171

L (Jiibbl.HaB, 10»

I.. Qtecni. HaU 130, ItK

I„ 1«Tl«, Hall, 108

L. Leal, ffoH. 168

L. Orru».a,H s,b.

L. Oi-o-le*. /JaU, . 806. 214. aa.
L. Onu, floil. .

I. |.aliilmn.flaU.

I. JV1.>|.-. JJhH. . 814, ejn,

L, Pli.-i..n. //«K 830,

1,. iinlpiis, BaU, 188, I'.Ni, Kin. 198.
I., imt<.mvnr.Iiiven., /fnH. .

1.. protcMuTn,(C(m™rii//nn

!.. qna-lnitum, BaU.

L. i..lMi.,lm.,. lloB. . 181, is:,. I«i. nil. Ifl.1, ins,
1.. lOgcrsI, //oil. 116. IT-. 17(1,
I.. ru.lL.. //all,

1., Slmmnrdt, fliiil 180.

!,, .-...■i«lo. J7«H,

L. S.ci.tjanl, H.iH, " . ' .'

INDEX.

xvu

PAGE.
Leptodesma nmbonatam, HaU^ .... 198
L. nrabonatam var. depreBsura, BdU, 199« 200, 202, 203

XiMapIa6€r, Hall, 85

L, macroptera, Ck)nra(l, 246, 251

X. I obtoUta, Hall, ...... 84

X. rugawtriatay Hall, ..... 15

Umoptk&a, ^ott, .243

L. cancellata, HaU, ..... 244

L. canceUatavar. oecidem.H. A. W., , 244

L. cnrvata, HaU, .... 250, 251

L. macroptcra, (Conrad) Hall, 244, 246, 250

L. obsoleta, ^Tott, .... 243. 249

L. panperata, ffaU, ..... 243

LYRipPBCTEy, Hatt, . 2, 40, 74

L. nnomiaeformis, Ball, . .53

L. cymbalon, ffdU, .45, 47, 60

L. Dardanos, Hall, .41

L. fiisciatns. Hall, 55

L. interradiatus, JSToZ^, .... 44, 50

L. macrodontus, ^ToZ^, 43, 45, 46, 48, 50, 52. 55, 57

L. magniflcoa, HaU, 45, 47, 48, 50, 51, 57

L. orbiculatus, HaU 41, 42, 81

L. parallclodontas, HaU, .40, 42

L. Polydorus. HaU 45, 50, 57

L. Priamas, HaU, . . 48, 50, 54, 56

L. solox, HaU, . . 45, 61. 56

L. trlcofitatns, ( Vdnuxem) HaU, 47, 48, 61

Meribtina, HaU, ...... 28

MODIOLA, Lamarck, .... 175, 236, 267

M. meUUa, Hall, ..... 266

if. praceden8,UaM 267, 268

M. (Bfytilops) metella, HaU, 268

M. M. ) prsocedens, HaU, . 267

MODIOMOBPHA, HaU, .... 175, 234

3fonoii$ princept, Conrad, . 1. 4

MrriLAUCA, HaU 253,262, 266

3r arenacea. Hall, .253

M. attcnnata, HaU, . 260

M. carinata, HaU, ... 258, 259, 261

M. Chomnngensis, ( Conr. ) H. , 257. 258, 269, 261 . 262, 264

M. llbrUtrlata. ( JFhUe if WhM/leld) HaU, . 264

M. gibbosa, HaU, 262

M. lata, HaU, ...... 262

M. occldentalis, ( WhUe if WhUJMd) HaU, 259, 263, 264

Jf. avi/ormii, (Conrad) Hall, . . .255

3f. ponderoaa. Hall, ..... 264

M. pyramidata, HaU, ..... 256

if. radiata. Hall, ..... 252

M. regularlB, HaU, 260, 262. 263

M. simplex, HaU, ..... 261

M. triqueter, (Conrad) Hall, . .265

M. nmbonata, HaU, ..... 257

M. (Plethomytilus) arenacea, HaU, . . 253, 254

if. (P. ) eardifarmis. Hall, 254

M. (P. ) Knappi, HaU, . 256

if. (P. ) mytilimera, Conrad, . 254

M (P. )oy&t&, HaU, .254

M. (P. ) OTiformis, HaU, . 255, 256. 265

H . (P. ) ponderosa, HaU, . . 254, 256

Mttilopb, HaU 262. 267

if {Modiola ) loto. Hall, . .262

if. (if )meteUa,UaU, ... 268

if. (if. )pr<Bceden8,HtL\], . .267

if. (if ) tin^lex, Hall, ... 261

Mttilus, .......

if Chemungetuis, (Conrad) Phillips A Salter.

M. nbrittriatiu. White A Whitfield, .

M. occidentalis, White A Whitfield,

M. jrhitjleldianua, Winchell,
Pal^opinna, HaU.

P. flabella, HaU, .

P. recurva, HaU,
Pecten cancellattu. Hall,

P. 1 convextu, Hall,

P.I crenulaius, UaW,

P. 1 doUibri/ormis, Hall,

P. duplicatus. Hall,

P. Halleanus, D'Orbigny, .

P. 9triatut,UtiVi, .

P. TranqucbaricnB, Om^n,

. P. undalatus, McCoy,
Pernopecten, WincheU, .

P. fasciculatua. Hall,
Pletiiomytilus, HaU,

P. ponderonu,ll[i\\, . .
Pterixea, Oold/U88,

P. avis. Hall,

P. Boydi, Conrad,

P. Chcmangensis, (Conrad) HaU,

P. consimilis, HaU,

P. ccstalata, JRoemer,

P. di8panda, HaU,

P. fascicnlata, Ooldfuaa,

P. flabella, HaU, .

P. grandis, HaU,

P. iutorstrialis, HaU,

P longispina, (HalH S. A Miller,

P. pingnis, Hall, .

P. prora, HaU, ....

P. protexta, (Conrad) S A. Miller,

P. reprotma. Hall,

P. rwer«a, HaU, .

P. reversa var. avU, Hall, .

P. rXgiiXa, Hall, .

P. 7 auborhiciUaris, Hall,

P. triqueter, Conrad,

P. (Verturania) avis, HaU,

P. (V. ) reproba, HaU, .

P. (V. ) revevHh, HaU,

2
103

95, 98, 101

91, 92, 93, 97

91
102, 104, 105

104

Pteroxites, McCoy, .

P. inoptatus, HaU,

P. teri», (Hull) S. A. Miller, .

P. tnuricatiu, Hall, .

P. profundus, HaU,

P. rostratua., HaU,

P. spinigerue, (Conrad) S. A. Miller,

P. subdecussata. Hall,

Pterinopectkx, HaU,

coutipectus, HaU, .
crenicostatus, HaU,
crenulatus, Hall, .
dignatus. Hall,
di$pandus, HaU,
ercctns, HtxU, .
exfoliatns, HaU,
(ilitextus, HaU,
Hermes, HaU,
imbccllis, HaU,

151, 208, 237

63, 65, 66, 68, 69

58, 78, 79

• • ■

32, 62, 64, 65
72. 76

59, 60

59, 62. 63, 64, 66, 67

PAGE.

176. 236

258

261

26S

264

240

241

268

254

107

113

102

100

179

107

183

105

101

266

105

106

104

289

239

168

108

289

238

177

110

248

237

XVUl

INDEX.

PAGE.

PAOB.

Pterinopecten insona, JEToU, 59,

Ptychopturia Endora, HaU,

138

intennedius, HaU, .....

expansa, JEToU, .

. 15«

inooiidtM, Hall 31,

micata, HaU,

186

laetna, ^Tott, 63,85,66,67,75.

107

Galeno, HaU, .

. 14S

lotfttM, Hall

gibbosH, HaU,

149, 150

multiradiatas, Hall, .....

lata, HaU,

. 145, 147

Neptnnas, HaU, .... 78,

lobata, HaU,

150

nodosus, IlaU, ......

perlata, HaU, .

. 147, 148

reflexns, HcM, .....

Proto, HaU, .

129, 133

regnlaris, HaU, .69,

Salamanca, HaU,

131, 134

spondylns, HaU, .....

Sao, HaU, .

. 132, 134. 135. 137, 145, 148

»«ric<tM, Hall,

sinuosa, HaU, .

129. 130

suborbicniaris, ^aZ2, . 44, 58, 77, 78,

spatulata, HaU,

144

terminalis. Hall, .....

Spio, HaU,

. 137, 138

nndosas, HaU, .....

Thalia, HaU,

148

Vertamnnfl, ^TaU. 71,76,79,

106

ThctiA, HaU, .

. 135, 196

(Aviculopcctcn ?) strictu.s, HaU,

tripronalU, HaU,

140, 144

Ptyciiopteria, Hall, 129,

206

Vanuxcmi, HaU,

. 151

alata, HaU 189, Ul,

141

SANGUIXOLITE8, McCoy, .

175

Beecheri, HaU, .....

148

SOLEN

f AJm • • • •

. . .241

elongata, ^TaU, .... 141,

143

Splrifcra Vemeulll, Blurchison,

131.189, '224, 238

Eacrate, HaU, . . 188, 137. 138, 142,

143

Vektumkia, HaU,

. 104

LAMELLIBRANCHIATA

OF THB

UPPER HELDERBER6, HAMILTON, PORTAGE AND CHEMUNG GROUPS.

DESCRIPTIONS OF SPECIES.

AVICULOPECTEN, McCoy.

Section a.

AviCULOPECTEN PRINCEPS.
PLATES I. FIGS. 10, 11 ; V, FIGS. 18, 19, 2S, 24 ; VI, FIGS. 1-9; XXIV, FIG. 7 ; AKD LZXXI, FIGS. 18-17.

MtmoHa prineeps, Cokrad. Annual Report N. Y. G^log. Survey, p. 117. 1888.
AvietUa parUia, ** Proceedingps Acad. Nat. Sci. Phila., vol. 8, p. 239, pi. 112, fig. 9. 1842.

Compare Avieulopeeten Sanduakyensia, Mbbk. Proceedings Acad. Nat. Sci. Phila., p. 161. 1871.
Aticula parUUf Con bad ? Mbbk. Palaeontology of Ohio, vol. 1, p. 197. 1878.
A. peetenifarmU, CoKRiJ>. Jour. Acad. Nat. Sci. Phila., vol. 8, p. 240, pi. 12, fig. 14. 1842.
Airieulopeeten prineeps, (Cokrad) Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 5, figs.

18, 19, 23, 24 ; pi. 24, fig. 7. Jan., 1883.
Affieulopecten 8andu9kyensiSf (Mbbk) 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

PALAEONTOLOGY OF NEW YORK.

the antero-lateral margin with little variation. Beaks obtuse, rounded,
anterior to the middle of the hinge.- Umbo subtending an angle of
about 130^.

Ears large, triangular ; posterior one the larger, and defined by the abrupt
slope of the side of the umbo, while the anterior ear is separated by a
distinct sulcus; lateral margins concave, becoming convex at the hinge-
line. Byssal-sinus broad, rounded, well-defined and indicated on the ear
by a sulcus extending to the extremity of the beak.

The right valve is flatter and proportionally broader than the left. The
limits of the ears are clearly indicated by the rapid slope of the umbo, and
the absence of strong radiating lines of ornamentation.

Test thin, marked by numerous regular alternating rays, which increase
in number by interstitial additions, and become broader and stronger towards
the margins. These radiating ribs are crossed by very fine, sharp striae of
growth. On the ears the rays are nearly obsolete, and the lines of growth
are sharper and stronger than on the body of the shell.

The internal mould preserves, in a subdued degree, the ornaments of
the exterior, and shows a simple, continuous pallial impression, extending
nearly parallel to the margins, and terminating in a large sub-ovate muscular
impression, which is posterior to the middle of the shell. The cavity
beneath the beak extends over the ligamental area at that point, forming
the cartilage-pit. In young individuals the ligamental area shows three or
four small furrows at the beak, extending towards the extremities of the
hinge-line. Three of these furrows measure 2 mm. across. In larger and
older individuals, this furrowed ligamental area is nuich more marked,
having frequently a width of 5 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
Lyriopecten.

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

LAMELLIBRANCHIA TA. 3

individuals have a height of 80 mm. with nearly equal length, and a hinge-
line of 50 mm. The gradation 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. Sandnskyensis the umbo is more inflated and obtuse, while the
length is uniformly greater than the height. A. scabridus^ 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. CoNBAD suggests the probable identity of this species with the subse-
quently described form, A. parilis, A careful comparison of a lai^e number
of specimens establishes this synonymy, and indicates the propriety of uniting
this form with the A, pecteniformis , Conrad. Avicuhpecten SanduskyensiSy 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 — foe. ciL :

4 PALJEONTOLOQY OF NEW YORK.

" Monotis princeps. — Shell convex, depressed; ear small, emarginate ; radiating
strise numerous; rugose, profound. Length about 3 inches.
^^ Locality i Cazenovia."

Mr. Conrad's description of Avicula pariUs is as follows {Jour. Acad. Nat. Sci.

Phila., Vol. VIII, p. 239. 1842) :

^^ Avicula parilis J pi. 12, fig. 9. — Upper valve flat; lower valve plano-convex;
surface with numerous, equal, filiform, prominent radii ; wings angulated at
tip, the anterior one most acute, and nearly equal in length to the posterior
wing ; apex not elevated above the hinge line ; anterior, posterior, and basal
margins forming an uninterrupted arched or rounded outline.

" Locality, Cazenovia, Miulison county. New York. Upper Silurian shale.

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

" The MoNOTis princeps, of the Geological Reports of New York, is probably
the same shell.

" The flat valve is represented on the plate."

Formations and localities. In limestone referred to the age of the Upper
Helderberg group (Corniferous limestone), at Sandusky, Delaware, and near
Columbus, Ohio ; and 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.

PLATE I, FIG. 9.

Avicula pecteniformis, Conrad. Journal Acad. Nat. Sci. Phila., vol. 8, p. 240. 1842.
AvictUopecten pectenifonnis, (Conrad) Hall. Pal. N. Y., vol. v, pt. 1. Plates ami Explanations : PI. 1, fig.

9. Jan., 1883.

Shell sub-ovate oblique to the hinge-line ; length equal to the height ; anterior
and basal margins regularly rounded, the body of the shell extc^nding in a
nearly straight line from the postero-lateral margin to the beak.

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

LAMELLIBRANCHIATA. 5

BLinge-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 strisB 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 sufficiently 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. exacuttiSy 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.

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

PALEONTOLOGY OF NEW YORK.

AVICULOPECTEN ClEON.

PLATE I. FIG. 1.

Avicniopecten Cleon, Hall. Pal. N. Y., vol. v, pt. 1. Plat«8 and Explanations : PI. 1, tig. 1. Jan., 1883.
Com|>ai*e with the young of A. princeps.

Shell small, ovate ; transverse axis slightly oblique ; length somewhat greater
than the height ; margins regularly rounded.

Left valve convex, the convexity equal to about one-sixth the length of
the hinge-line. The point of greatest convexity is just anterior to the
centre of the shell and towards the beak. Right valve not observed.

Hinge-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 by 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 strise of growth. The stronger rays have one or two finer lines
between. The lines of growth extend over the ears, but less distinctly than
over the body of the shell ; and otherwise 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 20 mm.

This form resembles the young of A. princeps^ but it is less oblique, and the
ears less strongly defined than in the young of that species as represented in
authentic specimens. The figure does not quite represent the form of the
specimen, and the posterior ear is not so well defineil as is shown in the
illustration. The form A. exacutus is very similar to this one ; but that species
has fewer and sharper radiating stria?, and the geological horizons of the two
are widely separated.

Formation and locality. Upper Helderberg limestone, Columbus, Ohio.

LAMELLIBRANCHIATA.

AVICULOPECTEN SCABRIDUS.
PLATE lU, FIGS. 8-12.

ArAcHlopeeten scabrid^is^ Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 3, figs. B~12.

Jan., 1883.

Shell large, sub-circular, very slightly oblique to the hinge-line; length
somewhat greater than the height ; pallial 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 ; umbonal 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 lamellaB 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 nmnerous, 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 PALEONTOLOGY OF NEW YORK.

This well-defined species is readily distinguished by the slight obliquity of
the body of the shell to the hinge-line, and the marked characters of the
surface. It differs from A. princeps and A. pedeniformis in having strong and
regular concentric markings, while the rays in these species are much more
acute, and the axis of the shell is usually quite oblique to the hinge-line.
Specimens which preserve the exterior shell show very beautifully the short
spinous processes of the concentric lamellae ; as shown, of the natural size, in
fig. 10, pi. 3. Examples of the species are abmidant, and have a considerable
vertical and horizontal range within the group in New York.

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

AVICULOPECTEN EXACUTUS.

PLATE III, FIGS. 18-22.

Aviculopecten exactUus, Hall. Pal. N. Y., vol. v, pt. 1. Plat4^8 and Explanations: PI. 3, figs. 18-22.

Jan., 1883.

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

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

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

Beak obtuse, oblique, anterior to the middle of the hinge and of the valve ;
umbo ample. In some specimens of the left valve, the beak 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 lunbo by a broad, shallow sulcus, an
obscure carination, and an abrupt change in the surface characters to sub-

LAMELLIBRANCHIATA. 9

dued Btrisd. 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 strisB. The ears show finer concentric striaB 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 striaB. 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 diflfers from the young of A. princepSj 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 striaB. A. pecteniformis has
obtuse roimded 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 FOBMIO.

PLATE V, FIGS. 20, 21.

Afieuiopeetei^ formiOf Hall. Pal. N. T., vol. v, pt. 1. Plates and Explanations : PL 5, figs. 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 surface
markings.

10 PALJEONTOLOGY OF NEW YORK.

Hinge-line straight, extending as far as the anterior margin ; length two-
thirds the height of the shell ; ligamental area narrow.

Beaks well-defined, not rising above the hinge-line, situated anterior to
the middle.

Posterior ear large, triangular, margin concave ; the ornamentation differ-
ing from that on the umbo ; defined by a slight depression and a change of
convexity. Anterior ear small, defined by a well-marked sulcus; byssal
sinus deep ; margin convex near the extremity of the hinge-line. The area
of the posterior ear is more than twice that of the anterior.

Test ornamented by about 35 rounded, radiating cost®, with intermediate
smaller ones, crossed and crenulated by regular strise of growth, of which
there are about 10 in the space of 5 mm. On the ears the radiating lines
are present, especially on the anterior ear, and the concentric strisd are more
crowded than on the body of the shell.

The characters of the interior are not preserved.

The largest specimen has a length of 32 mm., and the hinge-line measures
23 mm. A smaller specimen, preserving both valves, has a length of 29
mm., and height about equal.

This species is distinguished from A. exacutus by the greater angle subtended
by the sides of the umbo, by its greater obliquity, and the less sharp radiating
costae of the surface. In A. Phorcus the length is comparatively greater and
hinge-line shorter, the ears smaller, and the strong crenulating strise of
growth do not occur.

Formation and localities. In the shales of the Hamilton group, at Fultonham,
Schoharie county ; and Hamilton, Madison county, N. Y.

AviCULOPECTEN PhORCUS.

PLATE V, FIG. '22,

Aticidcpecten PhorcuSt Hall. Pal. N. Y., vol. v, pt. 1. Plates and Rxplanationn : PI. 6, fig". 22. Jan., 1888*

Shell of medium size, obliquely ovate ; height and length equal ; anterior and
basal margins regularly rounded, becoming more convex towards the middle

12 PALEONTOLOGY OF NEW YORK.

convex towards the middle of the postero-lateral side, and extending in a
straight or slightly concave line to the heaks.

Valves moderately convex, the right one more depressed when seen in
connection with the other, shorter and comparatively less oblique.

Hinge-line straight, length nearly two- thirds the height of the shell;
extending, in young individuals, as far as the anterior margins.

Beaks prominent, well-defined, situated anterior 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 by 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 strio), which are often
fasciculate, and fine concentric lines of growth. The broad fascicles of strise
often extend across one interval of growth, and on the succeeding interval
appear as regular or irregular stria) without aggregation, or as fascicles of
finer striae. This change does not always occur, but is very characteristic
when seen, as in figure 17, plate 5, where the variation is so extreme that it
afiects the outline of the shell. In young specimens the rays 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 length of 32 mm. ; another
specimen has a height of 23 mm., and a length of 25 mm. ; the hinge-line
is 16 mm.

The form and surface markings distinguish this species. It differs from A.
formiOj 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.
repletus and A. Orestes ; but a larger collection of specimens since these species

14 PALEONTOLOGY OF NEW YORK.

20 mm. Another individual ha« a height and length of 27 mm., and hinge-
line 16 mm.

This species differs from A. fascictUatus in its comparatively larger anterior
and smaller ix>8terior ears, while the shell is less full behind, and the fasciculate
surface has not been observed. In A. fortnio the posterior ears are much
larger, and the surface is distinctly reticulate. In A. scabridus the beaks are
more rounded, the wings more extended, and the surfiice quite different. Some
forms of A. duplicatus and A. rugtestriaius resemble this species ; but the posterior
ears of those species are larger, the anterior pair 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 differ-
ences. A. Itys is less oblique in outline, radiating strio) less distinctly rounded,
inclining to angular, distance between them greater than the striaB themselves ;
the evidence of the implantation of intermediate strio) is obscure; the
concentric lines are more distant and sharper, leaving the radii in the cast
distinctly crenulate.

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

AVICULOPECTEN LAUTUS.
PLATE III. PIGS. 1«, 17.

AvieiUopect^n lantM, Hall. Pal. N. Y.. vol. v, i)t. 1. Plat«»H an<l KxplaiiaUonci : PL 3, fig9. 16, 17.

Jan., 1883.

Shell obliquely ovate, height equal to the length, valves depressed, convexity
of right and left valves sub-equal.

Hinge-line straight, length about one-fifth less than the height of the
shell, 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, mucronate at the extremities, margins

16 PALEONTOLOGY OF NEW YORK.

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

Valves convex, very similar, except that the right valve shows an acute
byssal sinus.

Hinge-line short, 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 one a little the lai^r, 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
and crenulated by sharp, concentric strias. Below the middle of the shell
the rays become large rounded plications, increasing by implantation or
bifurcation, and the regular concentric sirm are stronger, distinctly crenu-
lating the rays, )>ecoming foliate, and giving the surface a rugose appearance.
The rays and concentric lines are present on the ears.

The interior is not preserved.

Two left valves have a height of 35 mm., and 22 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 mm.

This species is distinguished from A. dttplicattis by its comparatively greater
height, the obliquity of the valve, and the acute beaks ; the surface characters
of the two are very similar. A. cancellatus is more circular in outline, and the
anterior ears are larger than the post^^rior pair.

Formation and localities. Shales of the middle Chemung group, Philipsburg,
Rockville and Hobbieville, Alleghany county, N. Y.

18 PALEONTOLOGY OF NEW YORK.

This species re8eml)lert A, rugastriaius in surface characters, but it is less
oblique and proportionally much longer, with lujaks more obtuse*. The outline
of -4. cancellatus is more nearly circular, and the direction of the transverse
axis is oblique. From A. scabridics it differs in it« shorter hinge-line and
smaller ears, as well as in the surfiice markings.

Formation and localities. In the calcareous shales of the middle Chemung
group, Rockville, Hobbieville and Philipsburg, Alleghan}' county ; East Ran-
dolph, Cattiiraugus county, N. Y. ; and Mansfield and Sullivan, Tioga county,
Pennsylvania.

AvirULOPECTKN CANCELLATUS.
PLATK VII, FIGS. 12. 14-19.

Pecteii cancifUatnx, Hall. (4et>l<)|c. Surv. N. V. : Ri»p. Foiii-th Dint. 1843.
Not Avicul(>j)ecteH eaneellatHlug, McCoy.

Pecteu Halltanw,* d'Orbkjxy. Pixxinnne ile Pal»ontolo^e, vol. I, p. 87, No. 768. 1847.
Avicidoj}et'U*ii Hub-canceUatHS, Hall. Pal. N. Y., vol. v, pt. 1. Platte ami Kxplanations : PI. 7, figst. 12,

14-19. Jan., 1883.

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

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

Hinge-line straight, ecjual 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, crossed by regular
sharp, concentric strise, producing an evenly cancellate surface. The
posterior ear is marked by the concentric striaa with obscure radiating
lines ; the anterior ear is rugose from the prominence of from four to six
strong rays.

*Tliis name was pi^oposcd by il'Orbig'ny ai< a 8iib.stitiit«» for Ptcten canctUatas^ a name preoccupied by
Philli].)8 for an Oolitir foHMil. The latter is i)n>bably a true Pe<rten, and thei*e seems to me no sufficient
I'eaMon why the oii^nal name may not be nttained. AvictUa camTllata, V\\\\\\\yt^ Palieozoic FoBsibi, is
pi*obably not a:i Aviculoj>ecten.

20 PALEONTOLOGY OF NEW YORK.

This species is distinguished by ite erect equilateral form, sub-equal ears, and
the strong, regularly alternating radii.

Formation and locality. In the upper IhhIh of the Chemung group at Alleghany
Sulphur Springs, Warren county. Pa.

AVICULOPECTEN ItYS.

PLATE VII, Via. 1.1.

AutciifopecUu ItyM. Hall. PhI. N. V., vol. v, pt. 1. ];'laU*s ami Kxpl.inatioiis : PI. 7, ti^. 13. Jan., 18S3.

Shell small, broadly ovate, length nearly equal to the height, slightly oblique ;
margins regularly rounded, 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 shell.

Beak acute, directed slightly forward. Posterior uml)onal slope making a
greater angle with the hinge-line than the anterior. Umbo subtending a
right angle.

Ears nearly equal. Anterior ear the larger, obtuse at the extremity,
marked by several strong nulii, separated from the umbonal region by a
strong sulcus. Posterior ear narrow^ triangular, margin concave, separated
by a distinct sinus from the body of the shell, with no rays of ornamenta-
tion ; obtuse-angular. Byssal sinus well-defined.

Surface marked by sub-angular, rounded radii, which are regularly increased

in size with the growth of the shell, but rarely increased in number by

implantation; concentrically marked by fine, regular, thread-like striae of
growth.

Interior characters unknown. Hinge margin apparently simple.
The specimen described has a length of 25 mnj., height 27 mm., hinge-
line 13 mm.

This species is less oblique than A. Idas^ the hinge-line shorter, radii not
present on the posterior ear, surface markings coarser ; and rays increasing
more rapidly in size though fewer in number. In A. canceUaius (=-4. HaUeanuSf

22 PALEONTOLOGY OF NEW YORK.

In form, this species bears considerable resemblance to A. diq>licattis ; but
the surface markings are quite different, and the extremities of the hinge line
are more acute in tliis species. In A. scabridus the beak is not so well defined,
the ears usually more extended, and the coarser rugose radii of that species
are characteristic. Tliis form resembles some varieties ot A. fasciculattis in the
surface characters, but differs in the ol)li(iuity of tlie shell and form of the ears.
It differs from A. Idas in the more rotund form, more numerous and elevated
rays, and larger ears.

The single valve describtnl appears to ho 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 of the middle Chemung group,
near Elmira, N. Y.

AVICULOPECTEN 8TRIATU8.

TLATE X, FIGS. 3, 4.

Pecten afriaiwff Hall. Geolug". Surv. N. Y. : Rep. Fourth Dint. 1843.

AHculopecten striatuSf Hall. Pal. N. V., vol. \\ \)X. 1. Plato« and Explanations: PI. 10, ligH. 3, 4.

Jan.. 18H3.

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

Hinge-line straight, two-thirds the length of the shell, situated centrally
in regard to the body of the shell, not extending as far as the margin.

Beak central to the hinge-line, well-defined, arching over the hinge;
umbo prominent, the sides subtending a riglit angle.

Ears sub-equal, triangular, defined by the rapid slope of the sides of the
umbo. Anterior ear the larger, limited by a broad sinus; margins slightly
convex; extremity rounded. Posterior ear acute at the extremity; margins
concave.

Test ornamented with fine, rounded, closely arranged, regular radiating
striae, from 12 to 14 in the space of 5 mm. at the pallial margin. Some
specimens show a slight fiatteniug of the rays and also fine lines of growth.
The ears present the same surface charjicters.

LAMELLIBRANCHIATA. 23

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

The original 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 diflfers 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 VII, FIGS. 29, 30.

Aviculopect^n aJtus^ Hall. PaL N. V., vol. v, pi. 1. Plates and Explanations: PI. 7, figs. 29, 30.

Jan., 1883.
Not Aviculopeeten altuSf Wuitk. Bull. U. 8. 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 three-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

24 PALEONTOLOGY OF NEW YORK.

sinus, and from the sides of the uuiIh) hy a sulcus ; the byssal sinus is deep and
rounded.

Test marked by fine alternating filiform nuliating striaB, which are absent
on the ears, except as two or three alternating undulations. Fine lines of
growth mark the test and extend over the ears.

Ligamental area linear and marked by an inflection of the hinge-margin.

The specimen has a height of 15 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 by its equilateral proportions, acute,
straight apex, the non-obliquity of the transverse axis to the hinge-line, the
broad, triangular ears and the alternating surface strise. These characters sepa-
rate it from A. striatuSy to which it is most nearly allied.

Formation and locality. In sandstone of the conglomerate, associated with
the upper Chemung group, at Salamanca, Cattaraugus county, N. Y.

AVICULOPECTEN PATULUS.
PLATE Vll, F1U8. 32, 3».

Avu'tUt}})ecten patiiltiSf Hall. Pal. N. V., vol. v, ])t. 1. Plates au<l Explanations: PI. 9, tigs. 32, 33.

Jan., 1883.

Shell large, longitudinally broiidly elliptical ; height alx)ut 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 flattened in the middle.
Lateral margins very full, and curving rapidly to the ears.

Valves convex, the convexity eciual to one-fourth the length of the hinge-
line. The right and left valves do not differ conspicuously in character, so
far as observed.

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

26 PALEONTOLOGY OF NEW YORK.

Ears sub-equal, broad-triangular, flat ; margins slightly convex ; extremities
rectangular, defined by a gentle sinus, which is deeper below the anterior ear.

Test marked by about 35 strong, rounded, riuliating continuous plications
which are wider than the interspaces. These radii are absent on the ears.
The striae of growth are irregular and mark the entire surface of the shell.

Internal characters not observed.

A large specimen has a height of 53 mm., length 66 mm., hinge-line 34 mm.

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

Formation and locality. In sandstone of the upper part of the Chemung

group at Meadville, Craw^ford county, Pennsylvania.

AVICULOPECTEN DOLABRIFORMIS.
PLATE Vll, FIG. 21.

Pecteni (UtMtrifortiiis, Hall. Geolog". Surv. N. Y. : Rt*)). Foui'th Dist., p. 265. 1843.
Aviculopecten dolabrifonnh. Hall. Pal. N. Y., vol. v, pt. 1. Plat«8 and Explaiiationa : PI. 7, fig. 21.

Jan., 1883.

Shell small, sub-orbicular, slightly oblique ; height neiirly equal to the length ;
margins regularly rounded, 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 the hinge-line ;
umbo well defined by the rapid slope of the sides and the flatness of the
ears.

Ears triangular, flat ; 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 by fine radii and concentric striae, which char-
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.

28 PALEONTOLOGY OF NEW YORK.

AVICULOPECTEN C0NVEXU8.

PLATE VII, FKtS. «, ».

Ptcttni amvexus. Hall. Geolo^. Surv. N. Y. : Rt»p. Fourth Dint., p. 2B5. 1843.

Avicuiopecten convexus. Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 7, figs. 22, 23.

Jan., 1883.

Shell small, sub-orbicular, not oblique; height somewhat greater than the
length ; margins regularly rounded.

Left valve very convex, convexity equal to about one-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 iimlx) 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 the umbo ;
margin slightly concave. Anterior ear convex ; margin straight ; separated
from the umbo by a very deep and narrow sulcus. Byssal sinus small.

Test marked by fine irregular radiating stria? and finer regular concentric
lines ; the same surface charact<)rs 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 mm., length 12 mm., and
hinge-line 8 mm.

The remarkable convexity of the left valve distinguishes this species from
all the other forms here descril)ed. It*< orbicular outline, prominent beak wid
deep antcTior sulcus are also characteristic. In general appearance the body
of the shell resembles some forms of Athyris and Meristina among the
Brachiopods, but its pectinoid character is w^ell marked.

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

LAMELLIBRANCHIA TA. 29

AVICULOPECTEN SIGNATUS.
PLATE VU, FIG. 34.

Aviculaf signata. Hall. Geolo^r. 8ui'>'. N. Y. : Rep. Fourth Dist., p. 265. 1843.

AviculopecUn signatuSn Hall. Pal. N. Y., vol. v, pt. 1. Platea and Explanations : PI. 7, fig*. 24. Jan., 1883.

Shell small, obliquely sub-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, sub-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 locality. In the Chemung group at Rockville, Alleghany
county, N. Y.

AviCULOPECTEN CaROLI.
PLATE IX, FIG. 6.

Avieulopeeten Caroli, Winchbll. Proceedings Acad. Nat. Sci., Phila. 1863.

Ai)iculapeeteH Caroli, (Winchbll) Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 9, fig. 5.

Jan., 1883.

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

it--

30 PALEONTOLOGY OF NEW YORK.

Left valve convex, the convexity equal to about one-sixth of the longi-
tudinal diameter. Right valve unknown.

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

Beak obtuse, prominent, central, rising above the hinge.

Ears triangular, nearly equal, separated from the umbo by distinct sulci.
Anterior ear with slightly convex margin ; extremity rounded. Byssal sinus
deep. Margin of posterior ear concave ; extremity abruptly mucronate.

The test (a« preserved on a partial cast of the interior) is marked by 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
from five 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 under 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 locality. In the yellow sandstone of the Waverly group at
Newark, Ohio.

AvirULOPECTEN (CrENIPECTEN ?) INCULTUS.

PLATE IX, FIG. 3.

Aviculopevten {Ciruipecienf) inciiJtiut, Hall. Pal. N. V., vol. v, pt. 1. Plntos and Explanations: PI 9, &g,

3. Jan., 1883.

Shell small, longitudinally very broad-elliptical, nearly circular, not oblique to
the hinge-line^ sub-o(iuilateral ; height somewhat less than the longitudinal
diameter ; basal margin regularly rounded.

32 PALEONTOLOGY OF NEW YORK.

directed slightly forward, depressed. Umbonal region moderately prominent,
subtending an angle a little less than 90°.

Ears triangular, flat, extremities acute. Anterior ear smaller, defined by
a sulcus ; margin nearly straight. Posterior ear with the margin concave,
extremity acuminate ; having no strong radiating str^se.

Test, as indicated in an exfoliated specimen, marked by a few fine radiating
strise, with wider interspaces whicli are marked by finer radii. Anterior
ear showing the same characters. Posterior ear free from rays. Fine con-
centric stria3 cross the rays, and stnmger concentric wrinkles interrupt them
and produce a slight crenulation of the radii.

The specimen is 10.5 mm. in length, 10 mm. in height, with hinge-line a
little more than 11 mm.

This species resembles in form the young of Pterinopedm dignatus^ but differs
in the finer railiating lines on the Inxly of the shell, the concave margin, and
absence of rays on the posterior ear.

Formation and locality. In the l)lac*k Marcellus shale at Cherry Valley, Otsego
county, N. Y.

AviCULOPECTEN (PtERINOPECTEN ?) TERMINALI8.

PLATE I. VUi. 3.

PterifitypecUn tertniruUis, Hall. Pal. N. Y., vol. v, pt. 1. Platon aiul Kxplanations : PI. Iffig". 8. Jan;, 1883.

Shell small, rhoniboidal ; l)ody of the shell obliquely ovate ; length a little
greater than the height; margins regularly rounded, somewhat extended
behind.

Left valve very convex. Right valve unknown.

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

Beak jicute, prominent, directed a little forward, arching over the hinge-
line. Umbo elevated, subtending a right angle.

Ears triangular; margins concave; extremities acute. Posterior ear larger,
undefined. Anterior ear limited by a shallow sulcus. Byssal sinus moderate.

LAMELLIBRANCHIATA. 33

Test thin, marked by 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 surface markings, bears a slight resemblance to a young
individual of Avictdopecten princeps ; but the undefined ears and proportionally
longer hinge-line distinguish it.

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

Section b.

AVICULOPECTEN IGNOTUS.
PLATE 1, ¥1G. 2.

Avieulopeeten ignotus. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 1, fig". 2. Jan., 1888.

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 umbo
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
roimded.

Test thin, about .5 mm. in thickness ; marked with about twenty-five

irregular, rounded radii, which are crossed by very fine concentric striae, and

occasionally interrupted by varices of growth. The rays are conspicuous

34 PALJEONTOLOGY OF NEW YORK.

over the centre of the valve, becoming obscure toward the margins. The
ears show the concentric strise only.

The characters of the interior are not known.

A specimen of the left valve measures 25 mm. in height, 29 mm. in length,
and the hinge-line 21 mm.

This species in general expression reseml)les A. tenuis^ but is distinct in its
smaller anterior ear, more ol)tuse l)eak, orl)icular form, and more irregular and
stronger rays. Th<Mr geological positions are widely separated.

Formation and locality. In soft shaly l)eds of the Corniferous limestone, which
constitute the upper i)ortion of the group, at Lapham's mill, near Victor,
Ontario county, N. Y.

AVICULOPECTEN INSIGNI8.
PLATE I, FKi 8; PLATE HI, PIG. 1.1; ani> PLATE LXXXI. FIG. 7.

AttictUo^wcUn huslgnU^ Hall. Pal. N. V., vdI. v. pt. 1. Plato.sand Kxpltiiiation8 : PI. 1, fijf. 8 ; pi. 3, fig*. 13.

Jan., 1883.

Shell less than medium size, sub-rhoml)oidal, moderately oblique, about one-
third longer than high ; l)asal margins rounded ; anterior and posterior mar-
gins obtusely angular or abruptly rounded, and extending along the cardinal
slopes in a direct line to the beak.

Both valves are quite convex ; right valve somewhat the less convex.

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

Beak ol)tuse-angular, prominent, directed forward, nearly central. UmlK)nal
region ample, the sides subtending an obtuse angle, and sloping more
abruptly to the anterior than to the posterior margin.

Ears sub-equal, triangular. Anterior ear concave or flat, defined by a dis-
tinct sulcus ; margin deeply concave ; extremity ^icuminate. Byssal sinus
deep and well-marked. Posterior ear flattened, defined by the absence of
the stronger radii ; extremity slightly acute ; margin concave.

Test thin, marked ])y strong nuliating costa3, which in the left valve are
abruptly elevated and increa.se ])y interstitial mldition ; crossed by infrequent

36 PALEONTOLOGY OF NEW YORK.

Beaks obtuse-angled, direct^ forward, phiced anterior to the middle of
the valve ; sides of the unilx) carinate, and descending abruptly to the ears.

Posterior ear flat or concave, narrow-triangular, well-defined by the
carinate sides of the umbo, and by the absence of the strong surface radii ;
margin concave ; extremity acute, mucronate. Anterior ear about two-thirds
as long as the posterior one, triangular, convex ; defined by a deep 8ulcu8,
and the angular cardinal slope of the umbo ; 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 broad and rounded ; in the
right valve it is a deep, angular notch.

Test of the left valve marked by from 40 to 50 regular, continuous, thread-
like rays, alternating in fours, with three degrees of prominence, crossed and
crenulated by fine, regular, concentric strioB. The surface of the right valve
is nearly the reverse of this, having broad, flattened rays, arranged in pairs,
reguliirly bifurcating, with narrow concave interspaces which correspond to
the rays of the opposite valve. The posterior ears show several delicate rays
extending from the apex of the Ijeak over their upper portion.

The interior is not known.

A specimen preserving both valves has a height of 14 mm., length 19 mm.,
and hinge-line 20 mm. A right valve hiis a height of 14 mm., length 22 mm.
A left valve has a height of 12 mm., length 16 mm., hinge-line 17 mm.

This species in appearance resembles A. omatuSy and differs in its longitu-
dinally narrower outline, more obtuse beak, the niunerous rays, and the
absence of strong, lamellose, concentric fimbriaB. The two forms are of a
group resembling several species in a parallel group of the genus Actinoptera,
which are remarkable 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 Tinker's
Falls, Onondaga county ; Bellona, Yates county ; and near Norton's Landing,
Cayuga lake, N. Y.

LAMELLIBRANCHIA TA. 37

AVICULOPECTEN ORNATUS.

PLATE II, FIGS 7, 8 ; AND PLATE UI, FIG. 14.

Avieulopecten aniatus, Hall. Pal. N. V., vol. v, i»t. 1. Plates and Explanations : PI. 2, figs. 7, 8 ; pi. 3,

fig. 14. Jan., 1883.

Shell small, longitudinally oblique-ovate, sub-rhomboidal ; length and width in
the proportion 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 umbo ; 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 with a smaller ray ; crossed by
undulating, concentric striae which are curved backwards between the
stronger rays, producing arched fimbriae. The right valve shows the
radiating striae originating near the umbo, which is smooth, and increasing
by a double bifurcation, giving them a fasciculate appearance; they are
crossed by undulating, concentric strias. The ears are marked by strong,
radiating lines and fine, concentric striae.

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 PALEONTOLOGY OF NEW YORK.

ear. Both specieB show the smooth area on the unilx) of the right valve ; a
character not observed in any other species here described.

Formation and locality. In the Hamilton group ; shores of Canandaigua lake,
Ontario county, N. Y.

AVICULOPECTEN MUCR0NATU8.
PLATE HI, FHJ. 15.

Avicultypccttn mucrowUus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Ex|>lanatioiu< : PI. 3, fig*. 15.

Jan., 1883.

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

Left valve strongly convex. Right valve not observed.

Hinge-line straight, equal to the greatest length of the shell, extended
anteriorly.

Beak obtuse-angular, directed forward, nearly central. Umbo deep, sides
subtending an obtuse angle, sloping to the ears.

Ears sub-equal. Anterior ear narrow-triangular, elongate, acuminate,
defined by the deep byssal sinus and marked sulcus; margin concave.
Posterior ear wider, limited by an undefined sulcus; margin concave;
extremity acute.

Test ornamented by rounded radii, which bifurcate towards the margin ;
crossed by prominent, regular, concentric stria).

Hinge-area simple.

The specimen has a length of IG mm., height 15 mm., hinge-line 16 mm.

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

Formation and locality. In calcareous sliales of the Hamilton group at Dresden,
Yates county, N. Y.

40 PALAEONTOLOGY OF NEW YORK.

rectangular beak, and more regularly alternating rays. Both of these forms
are remarkable for the very slight convexity of the left valve.

Formation and localities. In calcareous sandstone of the Upper Chemung
group, Randolph and Salamanca, Catt4iraugus county, N. Y.

LYIUOPKCTEN, Hall.

Lyriopecten parallelodontus.

PLATE IV, Vn\f^. 1. i.

Lyritypetttn panUlelixiontfiJf, Hall. MS. for Pal. N. V., vol. v. 1877.

" ** •* Tatalog-uo Aint»r. Paljpozoic FotwilR, S. A. Millkr. Cincinnati, 1877.

** " •• Pal. N. Y.. vol. V, pt. 1. Plattv and Explanations: PI. 4, figs. 1, 2.

Jan., 1883.

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

Right valve moderately convex. Left valve unknown.

Hinge-line straight ; anterior portion not preserved in the specimen ; from
the beak to the extremity of the posterior ear it« length is one-half the
longitudinal diameter of the shell.

Beak obtuse, rounded, slightly oblique, anterior to the centre of the valve ;
umbonal region ample.

Posterior ear large, broiul-triangular, flat; margiii straight or slightly
concave ; extremity rectangular. Anterior ear not preserved.

Test thin, marked by about 00 regular, alternating, roimded radii, with
concave interspaces, and crossed by fine, elevated, sharp, cancellating striaa ;
these are crowded over the posterior ear, and the rays are there more
numerous and less regularly alternating.

The mould of the interior preserves, around the margin, traces of the
stronger rays, and shows a moderately impressed pallial line, with apparently
an ovate, muscular impression near the um])onal region. Cartilage-pit small,
deeply indented. Ligamental area narrow, marked by two or three slender,
parallel grooves, extending to the posterior extremity ; and one or 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 measures 20 mm. from the beak to the end of the posterior ear.

This species differs from L. orbictdatus 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.

Lymopecten Dardanus.

FLATE I, FIG. 6.
Lyriopecten Dardanwtt Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 1, (ig. 5. Jan., 1883.

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 imknown.

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 roimded continuous rays with wider
concave or flat interspaces, and sometimes a smaller intermediate ray ; crossed
by sharp, elevated concentric strioB. The rays are fine and little elevated on
the ears, while the concentric strioB are conspicuous.

42 PALEONTOLOGY OF NEW YORK.

Interior characters not observed, except an indication of a well-defined
ligamental area.

The specimen is 45 mm. in height, 48 mm. in length, and the hinge-line
43 mm.

This species resembles L. parallelodontuSy but diflFers in the comparatively
larger and more extended posterior ear and fewer and stronger rays, without
regular alternation of size. L. orbictdatus is more elongate, with more numerous
radii and less defined anterior ear.

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

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

LyRIOPECTEN ORBICULATUS.
PLATE IV, FIGS. 3-8; AND PLATE LXXXIl, FIG. 8.

Avicula arhiculfUa, Hall. Geolojf. 8urv. N. Y. : Rep. Fourth Dint., p. 202. 1843.
Lyriopecten arbiculatust Hall. MS., vol. v, pt. 1. 1877.

" " ** Catalog-ue Ainer. Palwozoic FtxHHilH, 8. A. Millbr. 1877.

" •« " Pal. N. Y., vol. V, pt. 1. Platoa and ExplanatioDS : PL 4, tig», 8-8.

Jan., 1883.
Not Aviculopectefi orbicularis, McCoy. Carb. Fo«p. of Ireland. 1844.
" " arbiculatus, " " " " "

Shell large, orbiculate, becoming wider and oblique with age ; length and
height equal in small and medium individuals ; in large specimens the height
is sometimes one-ninth greater than the longitudinal diameter; basal and
lateral margins full and regularly rounded.

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

Hinge-line straight, central ; length in young shells equal to four-fifths or
five-sixths of the longitudinal diajneter ; and in large specimens 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 middle of the hinge-line, and to the centre of the valve.

Anterior ear of left valve, in small shells, comparatively large, triangular,

LAMELLIBRANCHIA TA. 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 roimded. 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. macrodantuSy though
in form it bears some resemblance to the former ; and in the ligamental grooves
it is similar to the latter.

44 PALEONTOLOGY OF NEW YORK.

PterxTuypecten suborbicularis^ in some of the younger specimens, resembles this
species in general aspect; but none of that species have shown a broad,
ligamental area, and the ears continue to increase with the growth of the shell.

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

Lyriopecten intbrradiatus.

PLATK 11, FIGS. 1-4 ; AND PLATE LXXXH, FIG. 5.

LyrUypect^i inttrradiatuM, Hall. Pal. N. Y., vol. v, i>t. 1. Plates and Explanations: PI. 2, figs. 1-4.

Jan., 1883.

Shell large, longitudinally very broadly elliptical ; transverse axis somewhat
oblique to the hinge-line; height about one-ninth less than the length;
margins full and regularly rounded.

Valves about equal in dimensions. Left valve depressed, moderately
convex. Right valve flat, or slightly concave below, becoming convex
towards the beak.

Hinge-line straight, central to the body of the shell ; length less than two-
thirds the longitudinal diameter of the shell.

Beak of left valve obtuse, not prominent, directed forward, situated about
one-third the 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 by the deep byssal sinus.

Posterior ears narrow-triangular, distinguished from the gradually sloping
sides of the umbo by their flatness and finer markings ; margins concave ;
extremities mucronate. Anterior ear of the left valve smaller, triangular;
margins concave ; extremity rectangular. Anterior ear of the right valve
convex, triangular, truncated at the extremity ; separated from 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. 46

smaller intermediate implanted rays, crossed by fine, regular, elevated sharp
lines of growth, which at intervals are raised into lamellae, and appear in the
cast as strong transverse ridges crossing the radii. The ftirrows 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
by 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 difierences 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 largest 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 diflFers in the obliquity of the beak, wider anterior
ears, and more .elevated and numerous rays. It diflFers from L. magnificus 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 Aviculopbcten.

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. cymbalon (plate 24, fig. 8), but diflFers conspicuously in the
more niunerous, 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.

46 PALEONTOLOGY OF NEW YORK.

LyRIOPECTEN MACR0D0NTU8.

PLATE IV, FIG. 9; and PLATE VIII. FIGS. ». 10.

Lyrhvptn-ten macnuiifHtwt^ Hall. Cat. Pnlspoxoir FokhiIh. K. A. Millsr. Cincinn*ti. 1877.

Pal. N. Y., vol. V, ])t. 1. Platen and Explanatunw : PI. 4, fi^. 9; pi. 8,
ti^. 9, 10. Jan., 1888.

Shell large, sub-circular ; in some large si)ecimens becoming transversely broad-
ovate, from the iK)sterior extension of the valve ; height from one-sixth to
one-eighth less than the length ; margins regularly rounded, more convex at
the posterior lateral margin, and extending 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, rounded, directed slightly toward the anterior, not rising
above the hinge.

Anterior ear small, al>out one-thinl the length of the posterior, triangular,
not well-defined; margin straight or slightly concave; extremity obtuse.
Posterior ear large, triangular, defined by the absence of the strong radii,
and by a shallow, undefined depressicm reaching to the beak ; margin deeply
sinuate ; extremity acuminate.

Surface marked by from 30 to 40 broad, rounded radii, with usually
smaller intermediate rays, crossed by fine strioe of growth. Some fragments
of shell, adhering 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 beneath the apex of the beak, not extending to the hinge margin.
Ligamental area usually marked l)y five strong, elevated ridges, which curve
outward at the beak, diverging from, and partially enclosing, the cartilage-
pit, and continuing toward the extremities of the ears ; the innermost ridges
disappear before reaching the extremity of the area.

The largest specimen is 85 mm. high, 98 mm. long, and the hinge-line
50 mm. Another specimen, somewhat different in pro|)ortions, is 68 mm. in
height, 75 mm. long, with hinge-line of 40 mm.

LAMELLIBRANCHIA TA. 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. cymbaUm 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 hcalUies. In the coarse beds of the Hamilton group, at Ham-
ilton, Madison county ; and Worcester, Otsego county, N. Y.

Lyriopecten cymbalon.

PIJLTE XXIV. FIG. 8.
LyriopeeUn qpnbalon. Hall. Pal. N. Y., vol. v, ])t. 5. Plates and Explanations: PI. 24, fig. 8. Jan., 1883.

Shell large, sub-orbicular, not oblique ; 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
abrupt antero- and post-cardinal margins, and by its convexity.

Anterior ear very small, narrow-triangular ; margin concave ; extremity
obtuse-angular ; byssal notch broad and shallow, not conspicuous. Posterior
ear large, triangular, marked by a deep sinus ; margin convex ; extremity
angular ; length twice Jis 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 striaa 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 striae and undulations of growth. The direction and character

48 PALEONTOLOGY OF NEW YORK.

of the rays (in the specimen figured) have been affected, apparently, by some
injury received during the life of the animal, which has also produced a
strong varix of growth.

Ligamental area 1.5 mm. wide at the beak, whence it diminishes towards
the extremities of the hinge-line, marked by several flat, longitudinal strisB.
Cartilage-pit broad-triangular, situated under the apex.

The specimen described is 75 mm. in height, 88 mm. in longitudinal
diameter, and hinge-line 46 mm. The distance between the centres of two
of the large rays at the basal 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 beak
is mofe obtuse and rounded. It differs from L. macrodantus and L. magnificus
in its greater convexity, deeper 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. iricostatuif which is
the reverse of many species of recent PectenidsB, where the anterior ears are
developed beyond the posterior ; as in Janira hngicanda (d'Orbigny), and Pedm
Tranquebaricus (Gmelin).

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

Formation and locality. Hamilton group, from a bowlder found near Elmira,
N. Y.

Lyriopecten tricostatus.

PLATE IV. FIG. 11 ; PLATE VII, FKi. «6; ani> PLATE X, FIGS. 6-12.

Avicula trictMtnta, Vanuxkm. Gh»ol(»g. Surv. N. V. : Report of Thin! Dint., p. 179, fig. 1. 1848.
Lyrittpet'ten tricostatus (Vakuxbm), Hall. Pal. N. Y., v( I. v, pt. 1. Plate8 and ExplanationB : PI. 4» fig. 11 ;

pi. 7, tig. 26 ; pi. 10, tigH. 6-12. Jan., 1888.

Shell large, transversely and more or less obliquely broad-ovate; height
usually less than the length, the proportions varying with the age of the
shell ; young specimens are longitudinally elliptical ; mature specimens are
more oblique ; while some abnormal forms show a difference in the direction

50 PALEONTOLOGY OF NEW YORK.

mental grooves, diverging from the cartilage-pit, and continuing parallel to
the hinge-line ; cartilage-pit small, triangular, placed beneath the beak.

The 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 basal margin is 1 1 mm. A specimen of medium size is 62 mm. in
height, 72 mm. in length, hinge-line 39 mm. A young individual is 23
mm. in height, 29 mm. in length, and hinge-line 18 mm.

This species somewhat resembles in outline L, macrodoniuSy but differs in the
surface markings, and the finer parallel teeth of the ligamental area. It differs
from L. magmfictiSy L. interradiatuSy and L. cymbahn in outline ; the surface of
the latter species is similar, but more rugose. From L. Priamus it differs in
form and surface markings.

In 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, Chemung county ;
and Franklin, Delaware county, N. Y.

Lyriopecten Polydorus.

PLATE VII, FIG. «ft.
Lyriopecten Pulydonm, Hall. Pal. N. Y., vol. v, pt. 1 Plates an<l Explanations* : PI. 7, fig-. 25. Jan., 18S3.

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 flat. Right valve unknown.

Hinge-line straight, length eijual to two-thirds the length of the shell,
extending posteriorly nearly jus far as tlie posterior margin of the shell.

Beak pointed, directed forward, central to the body of the shell, and
forward of the middle of the hinge-line, rising a little above it. Umbonal
angle more tliaii 90°.

LAMELLIBRANCHIA TA. 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 umbo 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 striae 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. soloXy but diflfers in the flatness of
the valve and less gibbous umbo. In surface character it is similar to L.
iricostatus, 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 localUy. In argillo-arenaceous slates of the Chemung group
near Cassadaga, Chautauqua county, N. Y.

Lyriopecten maonificus.

PLATE VIII, FIG. 8.
Lyritfpecten magnificua. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 8, fig*. 8. Jan., 1883.

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 PALEONTOLOGY OF NEW YORK.

of the valve, extending farther toward tlie posterior than toward the
anterior margin.

Beak obtuse, rounded, central to the body of the shell, depressed, not
rising above the hinge-line, nor extending to tlie hinge-margin; umbonal
region moderately convex, not defined laterally.

Anterior ear small, narrow-triangular, not well-defined ; extremity very
obtuse, rounded ; margin slightly concave without a decided byssal sinus.
Posterior ear triangular, more than twice the length of the anterior, and defined
from the umbonal slope l)y the absence of the strong radii ; extremity acute-
angular ; margm marked by a broad, rounded sinus.

Test marked by about 40 strong, elevated rays, which are somewhat
flattened along their summits ; usually alternating with one or two sharp or
rounded rays, crossed by very fine, sharp, concentric striae. Tlie radii
gradually dimmish in strength towards the ears, where they are represented
by elevated, narrow lines.

Ligamental area marked by several longitudinal striaB. Other interior
characters not known.

The height of the specimen is 97 mm., length 104 mm., hinge-line 44 mm.
Three of the stronger rays occupy a space of 12 mm. at the basal margin.

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

In ornamentation and general outline there is some resemblance between this
shell and L. macrodontus^ but it is less convex, the rays are more elevated, and
more sharply defined. The geological horizons of the two species are also
widely separated.

Formation and locality. In coarse, arenaceous slates of the Upper Chemung
group, at Montrose, Susquehanna county, Penn.

LAMELLIBRANCHIA TA. 53

Lyriopecten anomi^formis.

PLATE IV, FIG. 10; PLATE X, FIG. 6; AND PLATE LXXXU, FIG. 2.

Lyriopecten anatniaformis, Hall. MSS. for vol. v, pt. 1. 1877.

Catalogue Amer. Palteozoic FoeeilB, 8. A. Millbb. 1877.
Pal. N. Y., vol. V, pt. 1. Plates and Explanations : PI. 4, fig. 10 ; pi. 10,
fig. 5. 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 posterolateral 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 strisa of growth; the larger rays are about 20 in
number. On the right valve the radii are represented by obscure, undu-
lating, unequal striae. The ears show the same surface markings.

Cartilage-pit small. Ligamental 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.

54 PALEONTOLOGY OF NEW YORK.

The right valve is imperfect, l>ut appears to have been more circular in
outline than the left.

This species is characterized by its fonn, surface ornamentation, and marked
resemblance between its right valve and the lower valves of some species of
the recent genus Anomia, in the flatness of the valve and deep byssal sinus.

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

Lyriopecten Priamus.

PLATE X. FlliS. 1, 2.
Jjyriopecteti Priamust Hall. Pal. N. V., vol. v, pt. I. Platen and Kxplanatioiw : PI. 10, lig8. 1, 2. Jan., 1883.

Shell large, transversely broadly elliptical or ovate, wider below ; transverse
axis normal or very slightly ol)li(iue to the hinge-line ; height less than one-
tenth greater than the longitudinal diameter ; margins regularly rounded.

Left valve moderately and symmetrically convex. Right valve unknown.

Hinge-line straight, sul)-central ; length alK)ut one-half the longitudinal
diameter of the shell.

Beak obtuse, rounded, oblique, anterior to the transverse axis, not rising
above nor extending as far as the hinge-margin.

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

Test marked by afjout 40 strong, rounded, irregular radii with narrow
interspaces, crossed by fine striae of growth. The rays are often composed
of fascicles of thread-like stria\ 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 striae extending to the
extremities of the hinge-line. Cartilage-pit triangular, narrow, situated at
the apex of the beak, and extending to tlie margin of the hinge.

One large specimen, wliich is a cast of the interior, measures 72 mm.*in
height, 70 mm. in length ; hinge-line 32 mm. A smaller specimen, showing

LAMELLIBRANCHIA TA. 56

the exterior, is 63 mm. in height, 67 mm. in longitudinal diameter, and
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.

FormaKon 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, U.

•

Ptmopecteu fa^cieulatwi. Hall. MS., vol. v, pt. 1. 1877.

" " " Catalogue Amer. Palteozoic Fossils, Millbr, p. 200. 1877.

Ifoi Avieulopefften faseinUatus, Hall.

Lyriopecten fasricUus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 9, figs. 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, scarcely 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.

Internal characters not known.

The specimen described, is a right valve, having a length of 34 mm.,
height 36 mm., and hinge-line about 10 mm.

In outline and surface characters this species resembles L. PriamuSy but the
valve is more convex than the specimen referred to the right valve of that
species ; it is also less oblique, and the beak more elevated and erect. The
rays of L. Priamus are distinctly and frequently bifurcating, while in this
species the fasciculate api)earance is due to the sharp, elevated striaB upon the
stronger rays.

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

Lyriopecten solox.

PLATE XXIV, FIG. 5.
Lyriiypfvten snUox. Hall. Pal. N. Y., vol. v, pt. 1. Platos and Explanations: PI. 24, fig. 5. Jan., 1883.

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

Right valve moderately convex. Left valve miknown.

Hinge-line straight, length alx)ut one-half the diameter of the shell,
extending farther on the anterior side.

Beak obtuse, rounded, central, not rising above the hinge-lme, directed
slightly forward ; umbo ample.

Posterior ear triangular, defined by its tlattened surface, and the rapid
umbonal slopes ; margin concave ; extremity rectangular. Anterior ear
imperfect, l)ut showing a very deep and narrow byssal sinus.

Test marked by numerous tine, angular rays, which are arranged in about
40 regular, rounded plications, composed of fa^^cicles of finer rays, with
defined interspaces. Finer ol)s(»ure rays mark the umbo, and the posterior
ear shows three or four rounded undulations with lines of growth.

Interior not known, except the ligameiital area, which is narrow, and
makes an intlection of the hinge-margin of the ears.

LAMELLIBRANCHIA TA. 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. Polydorus by its circular outline, convexity, obtuse
beak, ample umbo and surface characters. It differs 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. 6, 7.

Pterivopecten mfUtiradiatus, Hall. Pal. N. Y., vol. v, pi. 1. Plates and Explanations : PI. 1, figs. 6, 7.

Jan., 1883.

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.

58 PALEONTOLOGY OF NEW YORK.

Surface ornamented by numerous strong, distant, elevated, rounded rays,
with interspaces marked by a strong ray in the centre, and several finer
ones on each side, producing two series of alternations. Concentric striaB
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 simple, while 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 nmi., height 35 mm., hinge-line about
36 mm.

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

Formation and locality. In Corniferous limestone at Stafford, Genesee county,

N. Y.

Pterinopecten reflexus, n. sp.

PLATE LXXXII. FIG. H.

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

Left valve depressed-convex ; margin reflexed. Right valve unknown.

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

Beak obtuse, low, rounded, directed forward. Umbonal region convex,
subtending an obtuse angle.

Posterior ear large, flat, triangular, scarcely defined from the umbo ; 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

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 13 mm., height 11 mm., hinge-line 16.5 mm.

In some of the modes of occurrence, this species resembles P. exfoUattUj but
differs in its proportionally longer hinge-line, more extended posterior ear,
comparatively larger anterior ear, and the greatest convexity is nearer the beak.

Formation and locality. Upper Helderberg limestone, Western New York.
The particular locality unknown.

Pterinopectbn nodosus, n. sp.

PLATE LXXXU, FIG. 18.

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 anterior 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
strisa, with 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 the left valve ; but
it is so remarkable in its nodose undulations that 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 ; AMD PLATE LXXKIII, FIGS. 6, 7.

PUrinopeeUn ex/tdiattut. Hall. Pal. N. Y., vol. v, pt. 1. Plates and EzplanatioTis : PL 1, figs. 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 by 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 umbo. 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. insons ; but has a com-
paratively shorter hinge-line, smaller anterior ear, deeper byssal sinus, and less

62 PALEONTOLOGY OF NEW YORK.

extended posterior ear. It in more gibbous and less oblique than P. Hermes^
with less conspicuous striae.

The specimens are usually in the condition of partially exfoliated casts, and
retain marks of only the stronger radii and concentric undulations. The
differences between the internal mould and the impression of the exterior
of the shell are represented in figs. 6, 7, of pi. Ixxxiii. This species is not
uncommon in the central and western portions of the State.

Formation and localities. In a limestone bed of the Marcellus shale at Avon,
Livingston county, Stafford, Genesee county, and Vienna, Ontario county,
N. Y.

Pterinopecten dignatus.

PLATE I, FIGS 18, 14, lA.

Pterinopecten dignatus. Hall. Pal. N. Y., vol. v, pt. 1. PlateH and ExpUnations : PI. 1, figs. 12, 14, 15.

Jan., 1883.

Shell small, sub-rhomboidal, very slightly oblique ; length and height as three
to four ; pallial margins regularly rounded, somewhat more produced on the
posterolateral portion.

Left valve moderately convex. Right valve depressed, flatter and smaller
than the left ; it differs 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 ; deep, narrow and angular in the right valve.

Test of the left valve marked l)y numerous strong, rounded, increasing
radii, with broader interspaces, containing one or two smaller rays which
originate about the middle of the valve ; crossed by fine, sharply elevated,
concentric striae. The right valve is marked by fine, sub-equal, regular,

LAMELLIBRANCHIATA. 63

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

Internal characters not observed.

The largest specimen has a length of 19 mm., height 15 mm., 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. IcUuSy 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 differs in being less oblique, with the
posterior ear less extended, and with finer rays upon the ears. From P. crni-
sptdus it differs 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 l^tus, n. sp.

PLATE I, FIG. IS.

Pterinopetten lautua (in error). Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 1, fig. 13.

Jan., 1883.

Shell small, sub-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 body of the shell ; margin above the sinus
convex ; extremity acute. Byssal sinus moderate.

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

64 PALEONTOLOGY OF NEW YORK.

wrinkled from tlie apex to below the middle of the valve. The surface
markings are finer and sub-equal over the posterior ear. A small space on
the umbo, as in AvictUopeden btllus^ is destitute of radii.
Internal characters not known.

This species differs from P. Hermes in its less oblique form, shorter hinge-
line, less ample umln), and in having no regular alternation in the rays, which
are closer and more rounded. It is associated with, and closely allied to, P. dig-
natuSf but differs by its more obtuse beak, longer outline, and comparatively
more frequent and smaller rays, without the regular concentric striaB.

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

Pterinopectkn Hermes.

PLATE XVn, ri«8. lS-15.

PUrinapevttn Htnnex^ Hall. Pal. N. Y., vol. v, pt. 1. Platen and EzplaiiationB : F\, 17, f^, 13-15.

Jan., 1883.

Shell less than medium size, 8ul)-rhom])oidal, 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, anterior to the middle of the shell directed forward.
Umbonal region ample, subtending an angle of about 80°.

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

Test marked by regular, rounded striae, 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 surfiice is marked by fine concentric striae. Umbo with concentric
wrinkles. Partial casts of the interior show the same characters as the
exterior, but show no muscular or pallial markings.

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. UkIus ; 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.

Farmatim and locality. In shales of the Hamilton group, Ontario county, N. Y.

PtERINOPBCTEN SPONDYLtfS.
PLATE XVU, FIG. 16.

PUnntypeeten apondylun^ Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: 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. Umbonal 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

66 PALEONTOLOGY OF NEW YORK.

spines. The radii are less conspicuous on the ears, which also show a few
concentric undulations.

Internal characters not preserved. The ligamental area appears 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. lotus, but
is proportionally 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. 18, 80. 41.

Ptfrbwpevten coiMj}ect^i8, Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 17, fig«». 17-21.

Jan., 1883.

Shell of medium size, sub-rhomboidal ; moderately oblique in young shells,
scarcely oblique in older ones ; length and height about equal, the length
usually a little greater ; pallial margins regularly rounded, straighter poste-
riorly, and merging into the ear without definite limitation.

Left valve moderately convex. Right valve nearly flat, narrower and
oblique, with a deeper byssal sinus.

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

Beak sub-acute, anterior to the centre of the hinge-line, directed slightly
forward. Uiiibonal region somewhat prominent, subtending an angle of
about 75^.

Ears triangular. Posterior one much the larger, not distinctly defined on
the valve ; margin slightly concave ; extremity rectangular or somewhat
acute. Anterior ear small, distinctly defined by a rounded sulcus ; margin
convex ; extremity rounded or sub-angular. Byssal sinus moderate in the

LAMELLIBRANCHIA TA. 67

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

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

Internal characters not observed. Ligamental area simple.

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

This species difiers from P. dignattus in being less oblique, the anterior ear
less extended, and the radii sharper and more interrupted. It differs from
P. liBlus 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 fiutextus.

PLATE XVII, FIG. 22 ; and PLATE LXXXII, FIGS. 9, 10.

Pterifwpeeten JUitextiut, Hall. Pal. N. Y., vol. v, pt. 1. Plates and BxplanationB : PI. 17. fi|r. 22.

Jan., 1883.

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.

68 PALEONTOLOGY OF NEW YORK.

Beaks obtuse, anterior to the middle of the valve, directed forward, not
well defined. Umbonal region not strongly marked.

Ears miequal. Posterior ear wide-triangiilar, extending as far as the mar-
gin of the shell, its limits undefined ; margin nearly straight ; extremity rec-
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 valve thin, marked by fine filiform radii, with much wider
interspaces which are marked by finer rays ; the same character continuing
on the posterior ear, with more equal rays. The entire surface is marked
by fine, close, concentric lines of gix)wth, with lamellose elevations at unequal
intervals.

Hinge-ligament marked by several parallel grooves.

A right valve measures approximately 35 mm. in length, and 29 mm. in
height.

In general form this species resembles P. conspectus^ but is proportionally
longer, and the surface markings are different.

Formation and localities. In the Hamilton group near Cardiff, Onondaga
county, and from a bowlder of Hamilton shale at Pine Valley, Chemung
county, N. Y.

Pterinopecten intermedius, n. sp.

PLATE XVII, FKi. 19; and PLATE LXXXm, FKiS. 4, 5.

PteriHopect4:n canaptctus, in part. Hall. Pal. N. V., vol. v, pt. 1. Plates aiid Explanations: PI. 17, fi^f. 19,

Jan., 1883.

Shell of medium size, sub-rhomboidal, oblique ; length one-fourth greater than
the lieight ; margins regularly rounded, more convex on the post-basal aide.

Left valve convex, greatest convexity below the umbo. Right valve
unknown.

Hingfi-line straight, somewhat anterior ; length greater than the length of
the valve.

LAMELLIBRANCHIA TA. 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 striaB, 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 obscure 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 16 mm. A larger example has a length of 19 mm., height 16 mm., and
hinge-line 21 mm.

This species was arranged with P. conspectus. The recent study and compari-
son of a more numerous series of specimens shows several important differences,
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 hcaltties. 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.

Pt£R1N0P£CT£N REGULARIS, U. 8p.

PLATE LXXXIII. FIG. 1.

Shell of medium size, semi-circular, body of the valve oblique ; length 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, triangular, 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 valve; margin convex, in
regular continuation with the pallial margin ; extremity obtuse, angular.
Byssal sinus broad.

Test thin, marked witli numerous fine, alternating, filiform, elevated striaB
which are crossed by irregular lines of growth. The ornamentation of the
ears is somewhat more subdued than on the body of the valve.

Muscular impression small, ovate, situated below the middle of the post-
cardinal slope.

A specimen of the left valve luis a length of 24 mm., height 19 mm.,
hinge-line 25 mm. A larger example mejisures 31) 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 this genus here described. The
right valve of P. jUitextus has a similar outline, but the left vaJve has been
shown to have the margin of the posterior 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.

Formaiian and localities. In the shales of the Hamilton group, between
(jeneseo and Avon, and at Delphi, N. Y.

Pterinopecten Vertumnus.

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

Pterinopecten VertwanuSt 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 obtuse, low, anterior to the middle of the hinge-line, directed
forward. Umbonal 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 by sharp, elevated, concentric stria)
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 strisB. On the right valve the rays are more equal and finer than on the
opposite valve; conspicuous on the posterior ears and subdued on the
anterior.

Three specimens have respectively the following dimensions : length
38, 40, 41 mm., height 30, 33, 29 mm., hinge-line 35, 35, 32 mm.

72 PALEONTOLOGY OF NEW YORK.

This species resembles Pterinea reprobuSy from the shales of the Chemung
group at Ithaca, which has straighter and more rounded radii in the left valve,
with sharper intermediate radii and more elevated, undulating, concentric striae.
The right valve of that species is more convex with stronger and often dupli-
cating radii ; while the byssal sinus is less distinctly marked. The present
species differs from Pterinopecten dispandus in its greater length, proportionally
longer hinge-line, less strongly marked right valve, and want of duplication
in the radii.

Formation and locality. This species is common in the shales of the Hamilton
group at Bear gulf, Schoharie county, N. Y.

Pterinopecten undosus.

PLATE II. FIGS. 10-19; AND PLATE LXXXII. FIG. 7.

AvicuIope(ten wutulatuSt Hall. MS. 1877.

" " " Cat. Amor. PaliPoi5<»ic F(»«Bil». H. A. Millkr. 1877.

Not Pecten unduiatus, McCoy. Carb. Pow. of Ii*4*land, p. 101, pi. xvii, fig*. 12. 1844.
Not Avkiditpecten undidatus^ MK'oy. 18.')3.

Pterinopecten 7indt*tfu, Hall. Pal. N. Y., vol. v, pt. 1. Platen and Rxplanationa : PI. 2, figp. 10-19.

Jan., 1883.

Shell larger than medium, rhomboidal or sub-orbicular ; left vaJve moderately-
oblique; right valve scarcely oblique; length one-third greater than the
height, proportionally shorter in young shells and in the right valve ; ante-
rior and basal margins regularly rounded, somewhat produced behind, and
receding rapidly toward the hinge-line.

Valves nearly equally convex ; the right 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 depressed-convex.

Hinge-line straight, length a little less 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-defined,
subtending a very obtuse angle.

LAMELLIBRANCHIA TA. 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 striaB 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 striaB 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., height 37 mm., hinge-line 35 mm.
A yoimg 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.

74 PALAEONTOLOGY OF NEW YORK.

PtERINOPECTEN (AvICULOPECTEN ?) 8TRICTU8.
PLATE XXIV, FIO. 2 ; AND PLATE LXXXI, FIG. 18.

Pterinopecten Hrictus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 34, ^. 2. Jan., 1883.

Shell of medium size, transversely semi-elliptical, not oblique ; body of the
shell ovate, length one-sixth less than the height; anterior and basal
margins rounded ; posterior margin straight.

Left valve moderately convex. Right valve flat.

Hinge-line straight, equal to the length of the shell, central as regards
the transverse axis.

Beaks obtuse, low, directed slightly forward, anterior to the middle of the
hinge-line. Umbonal region moderately prominent in the upper part, sub-
tending an acute angle.

Ears triangular. Posterior ear much the larger, flat ; margin concave ;
extremity slightly acute, obscurely defined. Anterior ear small, convex,
defined by a well-marked groove or sulcus; margin rounded; extremity
acute. Byssal sinus distinct in the left valve, and a deep rounded notch in
the right valve.

Test of left valve marked by alternating stronger and finer rounded radii,
crossed by sharp, elevated, concentric lines of growth and more distant
imdulations, with imbricating lamellose lines. These markings are continued
over the ears, much 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 doubtfully arranged with the present group of forms. In
some aspects it resembles P, conspectus, but is specifically very distinct. It
might be compared with the young of some large forms of Ltriopegten or with
Aviculopecten, but the extent of the hinge-line, and the undefined limitation

w-.r.-.-.r.MAhL».

LAMELLIBRANCHIATA. 75

of the posterior ears, do not assimilate it with the ordinary characters ascribed
to those genera.

Formation and locality. In the Chemung group near Ebnira, N. Y.

Pterinopecten imbecilis.

PLATE XXIV. FIG. 1.

Pterinopecten hnbecilU, Hall. Pal. N. Y., vol. v» pt. 1. Pl&tea and Explanations: PL 24, fig. 1.

Jan., 18S8.

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 lamellad, 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, Uetus^ 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 D18PANDU8, 11. 8p.
PLATE LXXXII. FIU9. 11. li.

Shell large, somewhat rhoiiil)oicl-<)vate, oblique, varying with the age of the
shell ; length a little greater than the height ; margins regularly curved,
extending behind.

Left valve convex. Right valve depressed-convex, somewhat smaller
than the left, and proportionally longer.

Hinge-line straight, less than the greatest length of the shell, nearly
central.

Beaks obtuse, little elevated, anterior to the middle, directed forward.
Umbonal region scarcely define<l, moderately prominent, subtending a right
angle.

Ears triangular, undefined; margins concave. Posterior ear larger than
the anterior. Anterior ear limited by an imdefined 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, rounded radii, which alternate irregu-
larly with finer intercalated radii, and increase in sia^ and number towards
the margin ; cn>ssed by concentric stria?, with more distant varices of growth
which crenulate the radii. The rays are stronger over the anterior slopes,
and are continued 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 37 mm. in length, 42 and
44 mm. in height, hinge-line 41) and 30 mm. A right valve is 32 mm. in
length, 27 mm. in height, hinge-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 much sharper small intermediate

LAMELLIBRANCHIATA. 77

striae. The radii upon the right valve are also stronger and distinctly bifurcat-
ing ; the concentric strisB are stronger, closer, and crenulate the rays more dis-
tinctly. P. suborbicularis 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 coimty, Pennsylvania.

Pterinopecten erectus.

PLATE LXXXU, PIGS 1&-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, unecjual. 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 strisB 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. dispanduSy 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 CRENIC0STATU8.
PLATE VIII, FI(J8. S, 4 ; and PLATE LXXXII, FIG. 14.

Pterinopettm crenulatw (by eiTi>r), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Ex|)Unations : PI. 8, figs.

8. 4. Jan., 1883.

Shell large, sub-orbicular, slightly oblique ; length somewhat greater than the
height ; pallial margins regularly curved, broadly rounded from the antero-
lateral to the basal margin ; post-lateral margin less convex.

Left valve very moderately convex. Right valve not known.

Hinge-line straight, length one-fifth less than the length of the shell,
extended anteriorly, but not as far as the anterior margin of the valve.

Beak obtuse, rounded, scarcely directed forward, prominent, anterior to
the middle. Umbonal region wide, indistinctly defined on the posterior
side, more distinctly limited anteriorly, subtending an angle somewhat
greater than 90°.

Ears triangular, flat. Posterior ear five times as lai^ as 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, marke<l by about fifty strong, rounded rays which
are simple or bifurcating, always with finer intermediate rays. Concentric
striae strong, elevated, conspicuously crenulating the radii. The radii mark
the ears, and on the posterior ear are simple and distant.

Internal characters not known.

The two specimens figured give about the following respective dimensions :
length 56, 57 mm., height 47, 53 mm., and length of hinge-line 52 and
46 mm.

This species differs from P. suborbicularis in being more inequilateral, with
longer hinge, and stronger and less frequent nulii. It diflfers frt)m P. Nephmus,
pi. 8, fig. 6, by its more erect form, extended hinge-line, distant and elevated
radii, with stronger and more elevated concentric stride.

Formation and localities. In the shales of the Chemung group at Angelica and
Conewango, N. Y., and at Mansfield, Tioga county. Pa.

LAMELLIBRANCHIATA. 79

Pterinopecten Nbptunus.

PLATE Vin, FIGS. 6-7.

Pterinopecten Neptann^t Hall. Pal. N. T., vol. v, pt. 1. Platea and Explanations : PI. 8, figs. 5-7.

Jan., 1883.

Shell large, sub-orbicular, moderately oblique (more so in young shells) ; length
one-fifth greater than the height ; pallial margins regularly 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 slightly 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.

Surface 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 striaB 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 38 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 PALEONTOLOGY OF NEW YORK.

Formation and localities. In the Hhales of the Chemung group, Angelica and
Philipsburg, Alleghany county, N. Y.

PtERINOPECTEN 8UB0RBICULARI8.
PLATE Vni. FIGS. 1. 1 : PLATE XXIV. FIG. 10; AMD PLATE LXXXU. FIG. ft.

Pleritteaf subartncularix. Hall. G<h)1o^. Siirv. N. Y. : Rt^p. Fourth DikI., p. 364. 1843.
Pteriuupecten subt^rbifnlaruit Hall. PmI. N. Y., vol. v, pt. 1. Platen and Kxplanations : PI. 8, figs. 1, 2;

pi. 24. ti^. 10. Jan.. 1883.

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 posterior side ; post-basal margin extended.

Left valve convex. Right valve nearly flat ; similar in general form and
surface markings.

Hinge-line straight, anterior, nearly equal to 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 iin obtuse angle.

Ears triangular, unequal ; extremities angular. Posterior ear the larger,
undefined; margin concave. Anterior ear limited by 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 Ixxly of the shell they are strongly crenulated
by lamellose concentric strias.

Internal characters unknown. The ligamental area is a simple linear
groove.

A large specimen mea^sures 03 mm. in length, 55 mm. in height, the hinge-
line 55 mm. Another one is 38 mm. in length, 35 mm. in height, with
hinge-line 35 mm.

This species is distinguished by its sub-orbicular form, slight obliquity, nearly
equal length and height, and comparatively short hinge-line.

LAMELLIBRANCHIA TA. 81

The comparison with P. crenicostatus is given under the description of that
species. It resembles the young of Lyriopeden orbiadatuSy but the details of the
characters are quite diflferent.

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.

CRENIPECTEN,* Hall.

Crenipecten amplus.

PLATE IX, FIGS. 9, IS, 18.

Cfrenipeeten amplus. Hall. Pal.*N. Y., vol. v, pt. 1. Plates and ExplanationB : PI. 9, figs. 9, 13. Jan., 1883.
Cfrenipecten crtnulatuMf Hall. Pal. N. Y., vol.'v, pt. 1. Plates and Explanations : PI. 9, fig. 18. Jan., 1888.

Shell larger than medium, broadly and obliquely ovate ; height about one-
sixth greater than the length ; margins regularly rounded, more extended
posteriorly.

Left valve very 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. Umbonal 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.

* Tlie forms here described under this generic term have in part been i-eferred to Pbbhopbgtbn by Pro-
fessor Winchell ; but a eintical study of the type species of that genus shows that it possesses a large centi'al
cartilage-pit with a crenulated hinge-plate on each side below the hinge-margin, which characters alone are
sufficient to distinguish the genus and exclude the foiins hei-e descnbed uader Cbk^'IPKctbn. See discus-
sion of the i-elations of Pkrnopbctbn, Entolium and Crbnipkctbn, in the introduction to this volume.

82 PALAEONTOLOGY OF NEW YORK.

The largest specimen is 33 mm. in length, 38 mm. in height, hinge-line
16 mm.

This species differs from P. crenvlatus in its proportionally greater height,
rotundity, and less obliquity.

Although known only as a cjist, it is distinctively different from other species.

Formation and locality. In shales of the Chemung group at Rockville, Alle-
ghany county, N. Y.

Crenipecten crenulatus.

PLATE IX, FIGS. «, 7, H. lA. Ifl. 17.

Pectenf creuuIatNJt. Hall, doolog*. Surv. N. Y. : Rep. Fourth Di^t., p. 265. 1843.

Crenipecten aifntUatiui, Hall. Pal. N. Y., vol. v, pt. 1. Platen and RxplanationH : PI. 9, Ag^. 6-^, 15-17.

Jan., 1883.

Shell of medium size, ovoid-orbicular, moderately oblique ; length and height
nearly equal ; margins regularly rounded, somewhat extended posteriorly.

Right valve convex. Left valve depressed-convex above, and nearly flat
below.

Hinge-line straight, length more than one-half the length of the valve,
anterior to the middle of the shell.

Beaks obtuse, central, inclined somewhat forward, not rising above the
hinge-line. Uinbonal region of the right valve prominent, subtending an
angle of al>out 100^.

Ears small, triangular, sul>equal, limited on the right valve by the rapid
slope of the sides of the umbo ; margins slightly concave ; extremities angu-
lar. Byssal sinus not defined.

Test thin ; conspicuously marked with fine, concentric strisB of growth,
and obscure or nearly obsolete radii (as seen in figs. 7, 8 and 16, pi. 9).
The concentric lines are stronger on the ears, and are sometimes cancellated
by fine rays.

Ligamental area narrow, crenulated by a row of minute cartilage-pits.

A medium-sized specimen has a length of 29 mm., height 31 mm., hinge-
line 17 mm. A smaller specimen has a length of 26 mm., height 29 mm.,
and hinge-line 16 mm.

LAMELLIBRANCHIA TA. 83

All the specimens are in the condition of casts or much exfoliated, and the
surface markings are therefore obscure.

The species was originally founded upon specimens of the left valve ; the
right valves shown in figs. 6, 7 and 8, pi. 9, occur in the same association,
and have l>een identified as of the same species.

This species differs from C. obsoldus in its proportionally greater convexity
and length, and the obliquity of the transverse axis. It is also longer than
C. ampins.

Formation and locality. In shales of the Chemung group at Rockville, Alle-
ghany county, N. Y.

CrENIPECTEN IMPOLITUS.

PLATE IX, FIG. 14 ; AND PLATE LXXXIIJ, FIG. 10.

CreiiipetUn impolitus^ Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 9, fig. 14. Jan., 1883.

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 narrow expansion. In well-preserved specimens the
^ars 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 mm., width 26, and 19 mm., hinge-line 9 and 7 mm.

In general form and convexity this species resembles C. crenulattiSy but it is
narrower above, with the hinge-line comparatively much shorter.

84 PALEONTOLOGY OF NEW YORK.

The specimens are easts of the interior preserved in coarse sandstone ; the
surface markings are consequently obliterated.

Formation and locality. In a coarse sandstone of the Chemung group near
Olean, Alleghany county, N. Y.

Crenipecten obsoletus.

PLATE IX, FIGS. 19, 21.

LUmaf obsoleta. Hall, (leoloj?. Surv. N. Y. : Rep. Fourth Dist., p. 265. 1843

CrtnipecttH oNtoltiun. Hall. Pal. N. Y., vol. v, pt. 1. Plat4>8 and Kxplanatioiis : PI. 9. fiffn. 19, 21.

Jan., 1883.

Shell small, obliquely sub-ovate, length nearly equal to the height ; margins
regularly curved, becoming produced on the post-basal side, and somewhat
rectilinear on the posterior side.

Valves very similar. Right valve depressed-convex. Left valve regularly
convex.

Hinge-line straight, a little more than one-half the length of the shell.

Beak obtuse, more prominent on the left valve ; situated in the centre of
the hinge. Umbonal region well defined in the left valve ; depressed and
undefined in the right valve.

Ears small, triangular, sub-equal, defined by shallow sulci; margins gently
concave ; extremities obtuse. Posterior ear a little the larger. Byssal sinus
not conspicuous.

Test thin, marked by fine, closely arranged, concentric striae, which are
crowded and stronger on the ears. No radiating striae have been discovered.

Ligamental area narrow, marked l)y a row of minute cartilage-pits.

A left valve measures 18 mm. in length, 20 mm. in height, hinge-line 10
mm. A similar right valve is 16 mm. in length, 17 mm. in height, hinge-
line 8.5 mm.

This 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 Philipsburg,
Alleghany county, N. Y.

LAMELLIBRANCHIA TA. 85

Crenipecten olaber.

PLATE IX, FIGS. 20, 2S?

Lifna glaber. Hall. Geolog. Surv. N. Y. : Rep. Fourth Dist., p. 255. 1843.

Crenipecten glaber. Hall. Pal. N. Y , vol. v, pt. 1. Plates and Explanations : PI. 9, figs. 20, 22 1

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.
Umbonal region w^ll 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 striaB.

Interior unknown.

The crenulations of the ligameutal area are obscure in the specimen.

The original of this species is 12 mm. in length, 16 mm. in height, and
hinge-line 6 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.

86 PALEONTOLOGY OF NEW YORK.

CrENIPECTEN MICR0PTKRU8.
PLATE L\. FlU. 23.

Crenipectea micrttpteriis. Hall. Pal. N. V., vol. v, pt. 1. Platen ami Explanations: PL 9, Ags. 2, 8.

Jim.. 1883.

Shell small, longitudinally and obliquely 8ub-elliptical ; length somewhat
greater than the height ; margins regularly rounded, 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 of
the valve.

Beak low, obtuse. Umbonal region not strongly defined, subtending an
obtuse angle.

Ears very small, nearly ecjual, lK)unded by shallow* sulci. Byssal sinus
not distinct.

Surface marked by numerous low, rounded radii, with wider interspaces
and smaller intermediate radii ; crossed by fine concentric lines of growth,
which are stronger and crowded on the ears, forming their only siurface
marking.

Interior unknown. LigamentAl area obscurely crenulate.

The specimen descril)ed hiis a length of 18 mm., width 16 mm., hinge-
line 5 mm.

This species resembles in form C, cremdaius^ but differs in the radii, and in
the proportionally much shorter hinge-line. The surface markings are similar
to C. liratuSy 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.

-^Jw«

LAMELLIBRANCHIA TA. 87

Crenipecten liratus.

PLATE IX, FIU. 24 ; AND PLATE LXXXIU, FIG. 9.
Crenipecten liratuSf Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 9, 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
height of the valve from the beak. Right valve unknown.

Hinge-liae 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 by prominent, rounded, alternating radii, with interme-
diate smaller ones. There are about six larger rays, six smaller, and twice
that number of still smaller intermediate striae, all crossed by strong, regular,
concentric laminae 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.

Crenipegten Leon.

PLATE IX, FIG. li ; AND PLATK LXXXUI, FIG. 8.
Crenipecten Letm, Hall. Pal. N. Y., vol. v, pt. 1. Platen and Ezplanatiom: PI. 9, fi^. 12. Jan., 1888.

Shell of medium size, ovate, slightly oblique ; length about one-sixth less than
the height; margins regularly curved, produced below, rather straight on
the upper part of the posterior side.

Left valve moderately convex ; the greatest convexity is a little below the
middle.

Hinge-line straight, short, nearly central ; length about /)ne-third the
height of the valve.

Beak acute, erect. Umbonal region not strongly marked, subtending an
acute angle.

Ears sub-equal, small, sulci not conspicuous; posterior ear the 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-angidar rays, and
wider interspaces with smaller intermediate rays ; with fine concentric stria)
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 figured has a length of 26 mm., height 30 mm., hinge-liue
10 mm.

This species differs from all the others in its form and surface characters.
Formation and locality. In sandstene of the Chemung group at Leon, Catta-
raugus county, N. Y.

90 PALEONTOLOGY OF NEW YORK.

mm. Another individual measures 27 mm. in length, 26 mm. in height,
hinge-line 18 mm. A right valve referred to this species has a length of
20 mm. and a height of 18 mm., hinge-line 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 Aviculoptcten CoxanuSj 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 yet undescribed, which
will include other species now placed with the Carboniferous forms of Aviculo-
pecten.

In the original description of the genus, McCoy has not indicated the intimate
structure of the hinge, and it is not improbable that there are several generic
types among the species included in the Carboniferous forms of Aviculopecten.

The right and left valves have not been found in connection, 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.

92 PALEONTOLOGY OF NEW YORK.

Pterinea pinguis.

PLATE XV, FIGS. 2, 3 ; AND PLATE LXXXIII, FIG. 18.
Pterinea pinguis. Hall. Pal. N. Y, vol. v, pt. 1. Platt*^ and Explanations: PI. 15, figs. 2, 3. Jan., 1883.

Shell large ; gibbous, obliquely ovate, length and height nearly equal. Pallial
margins rounded, produced on the posterior basal side, and concave at the
junction of the wings.

Left valve ventricose, sub-angular along the anterior side. Right valve
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. Umbonal region prominent,
ventricose, defined, subtending an acute angle.

Wing large, triangular, limited by the rapid post-cardinal slope of the
valve ; margin slightly concave, rounding to the extremity which is angular.
The extent of the ear is not known, but it is limited by a deep sulcus which
gives an angular aspect to the antero-cturdinal slope of the shell. Byssal
sinus not marked in the specimens.

Surface ornamented with about fifteen broad, strong, rounded rays, crossed
by lamellae 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 70 mm.,
height 65 mm., hinge-line more than 65 mm. Another example has a con-
vexity of about 20 mm., length 63 mm., height 74 mm., hinge-line 55 mm.

This species bears some general resemblance to P. jlabdla ; it differs in its
large ventricose form, more elevated umbo, the characteristics of the upper part
of the anterior side of the body, and the abrupt slope into the wing without a
distinct sulcus.

Formation and locality. In the Comiferous limestone, near Columbus, Ohio.

LAMELLIBRANCHIATA. 93

Pterinea flabella.

PLATE XIV. PIGS. 1-21 ; PLATE XV, FIGS. 1, 4-6, 8-10 ; AND PLAT£ LXXXUI, FIGS. 11, 18.

AviciUa flabella, Conrad. Jour. Acad. Nat. Sci., Phil., vol. 8, p. 238, pi. 12, fig. 8. 1842.

" (") Vanuxbm. Geol. Surv. N. Y.: Report Thini Dist. 1S43.

Compare Pterinea foJtciculata, Goldfuss. Petrefacta G^ermanis, p. 187, pi. 120, fig. 5. 1840.

♦♦ *♦ •• (**) Sandberger, Veratein, Rhein, SchichtensyBt, Naawiu, p. 293, pi.

30, fig. 7. 1856.

** ** costulaiOf F. A. Robmbr, Dunkbr and voir Mbtbr. Rabeontographica, T. 1, fig. 2.

Pteriuta flabdla, (Conrad) Hall. Pal. N. Y., vol v, pt. 1. PlateB and Explanations: PI. 14, fig3. 1-21;

pi. 15, 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 a little convexity on the umbo ; arcuate, to correspond
with the curvature of the opposite 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, limited by the sulci of the cardinal expansions,
and subtending an angle of from 30^ to 60^. 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 striaB and the sinus.

96 PALEONTOLOGY OF NEW YORK.

Formations and localities. This species has been recognized in a single ill-
preserved specimen from the Corniferous limestone, at Stafford, Genesee couniy,
N. Y. ; casts of the interior, and a single extravagant form preserving the smr-
face characters, have been obtained from limestone of the same age near Col-
umbus, Ohio. It is abundant in the Hamilton group at numerous localities
from Schoharie to Cayuga lake, more rarely in the western part of the State ;
though occurring at Hamburg and elsewhere on Lake Erie shore. It is found
in the upper l)eds T)f the Chemung group in Steuben county, N. T., and Tioga
county, Pennsylvania.

Pterinea interstrialis, n. sp.

TLATK LXXXIV. FUw «.

Shell large; left valve obliquely 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 straight, about equal to the length of the shelL

Beak acute, inclined forward. Umbonal region not prominent, narrow,
limited by the cardinal expansions ; subtending an acute angle.

Wing triangular, large ; margin concave ; extremity acute. Ear triangular,
small.

Surface nuirketl by about 20 regular, strong, rounded rays which originate
on the upper part of the umbo and continue undivided to the margin ; with
broad, flat interspaces marked by from two to four slender, sharp radii, and
crossed by fine concentric striw. About twelve of the strong rays reach the
margin of the valve below the middle of its height, the remainder come out
on the up[)er anterior margin. The wing shows the radii somewhat less
strong than the body of the valve. The ear is marked by strong radii.

Interior unknown.

The specimen described has a greatest length of about 55 mm. ; height
nearly 58 mm. ; hinge-line from beak to extremity of wing, about 58 mm.

LAMELLIBRANCHIA TA. 97

This species somewhat resembles P. fiabella ; and differs in its less convexity,
more numerous strong rays with finer intermediate lines, and less conspicuous
concentric striae.

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

Pterinea dispanda.

PLATE XV, FIG. 7.
Pterifiea dUpatidOt Hall. Pal. N. Y., vol. v, pt. 1. PlatcH and Explanations: PI. 15, fig. 7. Jan., 18S3.

Shell large ; body very broadly 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 body, extended pos-
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 by 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 striaB; 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 70 mm., length about 80 mm., and
the length of the hinge-line about 90 mm.

98 PALEONTOLOGY OF NEW YORK.

This shell bears some resemblance to the more extravagant forms of Pterinea
flabellaj but it is larger than any known specimen of that species, with a propor-
tionally longer and less defined body, and distinctly different surface ornamen-
tation.

Formation and locality. In the upper beds of the Chemung group at Mansfield,
Tioga county, Penna.

Pterinea Chemungensis.

PLATE XVI, FIGS. 3, 7, 10, 12 ; PLATE LXXXIV, FIG. «.

Avicida CheiHU7igen8ut, Conrad. Jour. Ac&cl. Nat. Sci., Phila., vol. 8, p. 243. 1842.
Apicula pectmifonnis. Hall. Geolog. Surv. N. Y.: Rept. Fourth Dist., p. 262. 1843.
Pterinea Chetnungensis, (Coxkad) Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 16, figs. 3,

7, 10. 12. Jan., 1883.

Shell very large, rhoml)oidal ; body of shell ovate, narrower above, nearly
erect, or sometimes oblique ; length less tlian the height ; greatest length
below the middle ; basal and iK)st-])jisal margins rounded ; the anterior
margin above the middle is nearly straight, and the corresponding portion of
the posterior margin is gently concave.

Left valve moderately convex alcove, depressed-convex in the lower part.
Right valve depressed-convex towards the beak, flat or slightly concave below.

Hinge-line 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.
Umbonal region not strongly defined, most prominent a little below the
hinge ; subtending an acute angle.

Ear short, nearly equilateral, limited by a rounded sulcus ; margin concave,
with 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 by marked change in the surface characters
from the body of the shell ; margin straight or slightly concave ; extremity
obtuse. In the right valve, the wing is less distinctly defined than in the
left.

Test somewhat thin ; left valve marked ])y slender, filiform rays, variously

LAMELLIBRANCHIA TA. 99

alternating and bifurcating, or sometimes simple from the umbo to the base,
continuing over the wing, and somewhat stronger on the anterior cardinal
extremity than on the posterior ; the interspaces flat, much wider than the
rays. The surface is crossed by fine, closely arranged, concentric striaB, 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 striae 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. Obsciu'e indications of lateral teeth liave been seen.

A left valve is 62 mm. in length, 76 mm. in lieight, hinge-line 55 mm.
Anotlier 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 the ])roadly rounded biise and interrupted rays, which are
coarse and fine, and irregularly arranged.

This species resembles P. rigiday but the radii have an appearance of less
rigidity, the hinge-area is narrower and the shell is more oblique. It is closely
allied to P. cowsimilis^ differing in the proportionally shorter hinge-line, greater
height of body, and less obliquity.

Formation and locality. In the Chemung group at Chemung Narrows, Che-
mung county, N. Y.

100 PALEONTOLOGY OF NEW YORK.

PtERINEA CONSIMILIS.
PLATE XVI, FIGS. 1, 2, 8. 9, 11 ; AMD PLATE LXXXIV, FIG. 23.

Pterinen amsimilis. Hall. Pal. N. Y., vol. v, pt. 1. Plates and ExplanatioiiB : PI. 15, figs. 1, 2, 8, 9, 11.

Jan., 1883.

Shell large, sub-rhomboidal, nearly orbicular ; length greater than the height ;
margins regularly curved, moderately produced on the posterior end.

Left valve convex above, depressed-convex below. Right valve convex on
the umbo, flat or slightly concave below.

Hinge-line straight, length equal to or a little greater than the length of
the valve.

Beak acute, anterior, inclined slightly forward, not rising above the hinge.
Umbonal region prominent but not strongly limited, subtending more than a
right angle.

Ear small, limited hy the abrupt slope of the umbo, which becomes a dis-
tinct sulcus in the right valve ; margin convex (except in the byssal 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 marked. Fine, closely
arranged, inconspicuous concentric striaB cross the surface. The wings of
both valves are similar in surface characters. The body of the right valve
shows the concentric striae, 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
adjacent to the wing.

A left valve has a length of 52 mm., height 49 mm., hinge-line about 50

t •
• • •

. •• •

• • •

• -• •.

..'•lOS PALEONTOLOGY OF NEW YORK.

.*. ••

line about 35 mm. A smaller si)ecimen is 26 mm. in length, 25 mm. in
height, hinge-line 24 mm.

This species l>ears n general reseml)lance to P. Chemungensis; it differs in
its continuous and comparatively stronger rigid nulii. The group of four species,
beginning with P. Chemungensis^ is well marked and have many characters in
common ; ])ut nevertheless, present differences which warrant their specific
separation.

Formation and localities. In tlie Chemung group, at several localities in
Chemung county, N. Y.

Pterinea prora.

PLATK XVI, FUiS. 4, 13, H.

Pierin-ea p^rr>m. Hall. Pal. N. V., vol. v, pt. 1. PlatifH and Explanations: PI. 16, tigs. 4, 13, 14.

Jan., 1883.

Shell of medium size or larger, sub-rliomboidal, oblique ; body ovate, narrow
above ; length one-fourth greater than the height ; margins regularly rounded,
extended on the post-basal portion and sloping rapidly into the sinus of the
wing.

Left valve moderately convex. Right valve depressed-convex above, flat
or concave below, apparently smaller than the left.

Hinge-line straight, longer than the length of tlie valve, and extending
beyond both margins.

Beak small, iicute, directed forward, situated at about the anterior fifth of
the hinge. Umbonal region undefined, not prominent.

Ear about one-fifth the length of the wing, separated from the body of the
valve by a shallow undefined sulcus and marked byssal sinus ; margin con-
vex ; extremity rounded. Wing large, triangular, extended, defined only by
the change in the curvature of its margin from that of the body of the valve ;
margin deeply concave ; extremity acute.

Surface of left valve marked with regular, rounded, sub-equal rays, with

104 PALJEONTOLOGY OF NEW YORK.

VERTUMNIA, n. s. g.
Pterinea (Vertumnia) reversa.

PLATE XXIV, riGii. 6. 1«; and PLATE LXXXIV, PIG. 84.

Pti-rinea rererm. Hall. Pal. N. Y., vol. v, pt. 1. PlateH and Explanations: PI. 24, tigs. 6, 12.

Jan.» 1883.

Shell large, rhomboid-orbicular ; body somewhat oblique ; length and height
nearly equal ; margins regularly rounded, a little more extended on the pos-
terior side.

Left valve flat, or slightly concave, except near the umbo. Right valve
moderately convex, the greatest convexity about the middle of the height.

Hinge-line straight, length equal to the length of the valve, extending
anteriorly beyond the margin.

Beak of left valve depressed, ol)tuse, undefined, erect. Beak of right valve
low, obtuse, inclined forward. Umbo not distinct in either valve.

Ear of tlie right valve limited hy a distinct broad byssal sinus. Wing
triangular, undefined.

SurfU(H» marked by strong, rounded, simple, continuous radii which
originaU* upon the umbo ; with wide, flat interspaces, which, in the right
valve, show occasionally a finer ray; crossed by regularly arranged, sharp,
concentric stria), wliich are conspicuous both on the rays and interspaces.
The rays are o])Scure and distant on the upper part of the cardinal expansions.

A large right valve has a length of 50 mm., height 47 mm., hinge-line
Tif) nnu.

This species difters Irom P. prora by its lesser obliquity, the indefiniteness of
tlie cardinal (expansions, the convexity of the right valve, and the flat or con-
cave* clnn'a(*U»r of tlie h^ft valve.

Formatim and locality, in tlie Chemung group near Elmira, at the Upper
Narrows of Olunnimg river, N. Y., and in Tioga county. Pa.

106 PALEONTOLOGY OF NEW YORK.

Pterinea (Vertumnia) reproba, 11. np.

PLATE LXXXII, VUiS. 1», 20.

Shell of medium size, rliomboidal ; body oblique ; length somewhat greater than
the height ; pallial margin regularly rounded, ])ecoming produced behind and
extending thence in a neariy 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 than the greatest length of the shell,
extended anteriorly considerably beyond the margin of the valve.

Beaks obtuse, not prominent, directtnl forward, anterior to the middle.
Umbonal region undefined.

Ear defined by a shallow sulcus ; margin concave ; extremity acute. Byssal
sinus moderate, marked in the right valve by a partial reflexion of the mar-
gin. Wing large, triangular and undefined ; margin nearly straight below,
slightly concave toward the extremity, which is acute.

Surface marked ])y numerous strong, rounded rays, which alternate on the
left valve, and duplicate on the right valve. The interspaces are equal to,
or greater than, the nulii ; the rays are finer on the carduial expansions, and
very obscure on the ear and umlx)nal region of the right valve. Concentric
striflB regular, sharp.

Interior not known.

Ligamental area narrow, and marked by one or two longitudinal furrows.
The sharp striae 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., hinge-line 30 mm.
A right valve has a length of 36 mm., height 28 mm., hinge-line 37 mm.

This species differs from Pterinopecten Vertumnus by its comparatively
longer hinge-line, more extended enr, less distinctly curving, narrower, and
more abruptly elevated radii cm the left valve ; and stronger, not undulating,
duplicating radii of the right valve. The form and proportions are similar to

LAMELLIBRANCHIATA. 107

Pterinopecten Icdus^ but it is a larger and coarser form, with the right valve con-
vex. The geological positions of the two species are quite diflferent. The
character of the surface ornamentation distinguishes it from Pterinea prora and
Pterinea 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.

PLATE XXV, FIG. 1.

ActinnpUria exiviia. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 25, fig*. 1. Jan., 1883.

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 60^.

Ear short, oblique, limited by a distinct sulcus ; margin convex ; extremity
roimded. 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 about twenty strong, elevated slender rays, with regular
lamellae 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 min.

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 of the genus yet found in the Schoharie grit. It differs from
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 MUMCATA.

PLATE XVII, FIGS. 1-3.

AvictUa muricat€Lf Hall. Gih)!. Surv. N. Y. : Rop. Fourth Dist., p. 181. 1843.

Ptenmitea muricatus. Hall. Cat. Am. Pal. Foss. : 8. A. Miller, p. 202. 1877.

Adinapteria muriccUOf Hall. Pal. N. Y., vol. v, pt. 1. Plat«8 aii<l Explanations : Pi. 17, figs, 1-3. Jan., 1883.

Shell 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. Right valve unknown.

Hinge-line straight from the beak to the posterior extremity, sloping
downward on the anterior side ; entire length greater than that of the body
of the shell.

Beak acute, arching over the hinge, inclined forward, 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. Wing 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 striae are conspicuous in the anterior sulcus.

Interior unknown.

110 PALEONTOLOGY OF NEW YORK.

Interior unknown.

Ligamcntal area with one or two longitudinal grooves.

The specimen has a length of 18 mm., height 16 mm.

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

ACTINOPTERIA SUBDECUSSATA.

PLATE XVII, FKiS. 23. 2S-27. »-31 ; AND PLATE XIX, FIrt. 2ft.

Plenmitts subdeciutscUa, Hall. MS., vol. v. 1877.

K. A. Millor in Cat. Am. Pal. Fotw., p. 20a. 1877.
Aciinopterui utihdtt-wwdia. Hall. Pnl. N. V.. vol. v, pt. 1. Platen and Explanationfi : PL 17, fig«. 23, 2Sh-

27, 29-31 ; pi. IJ). tijr. 25. Jan., 1883.

Shell large, sub-rhomboidal, very oblique ; body elongate sub-ovate ; height
about one-third less than the length ; margins regularly curved, becoming
more extended on the j)08terior 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. Right valve moderately convex near the umbo, flat or
concave below the middle.

Hinge-line straight, length about one-fifth less than the length of the shell,
not extending Jis far as the posterior margin of the left valve, but extending
beyond the posterior margin of the right valve.

Beak acute, directed forward, somewhat prominent, anterior nearly
terminal. Umbonal region (in young shells) well marked by the sulci;
umbonal angle iicute.

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 aeoond aefe interca-

112 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 acute, prominent, inclined forward, close to the anterior end of the
shell. Umbonal 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 mere fold in the shell. Wing large, triangular, flait, extending nearly to
the margin of the valve ; limited, in the left valve, by a more or less dis-
tinct sulcus, and the abrupt bending of the concentric strisa ; margin con-
cave ; extremity acute. This character of the wing is somewhat less marked
in the right valve.

Test thick ; the left valve marked >vith strong, prominent, rounded radii,
regularly alternating with finer ones on the posterior half of the valve;
crossed at regular intervals by strong concentric lamellaa ; the interspaces
marked by 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 lamellse,
and in many examples the concentric striae interrupt the rays, leaving them
alternating alK)ve and below^ the lamellaB. (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 crowded 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 lamellse
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 and below the umbo to the posterior portion
of the body and thence recurving, terminating in a small oval muscular impres-
sion. No evidences of teeth are seen in the casts or the interior of valves.

A large specimen has a length of 7G 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.

L ..: 1

114 PALEONTOLOGY OF NEW YORK.

the mai^in, with rarely intercalated finer rays; crossed by regular, sharp,
elevated, concentric lamelhe which (in gowi specimenB) are produced into sub-
tubular, spiniform extensions uix)n the rays. Lines of growth are seen
between the lamella>. On the wing the rays are more subdued while the
concentric lamella? are strong. The ear is marked only by the crowded con-
centric stria*. On the right valve the railii are obsolete on the body and
well-marked on the wing, and the lamellose expansions are conspicuous. In
some ciusts they appear as undulating elevat^Ml lamellaB.

Pallial line extending parallel to the margin 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 slender grooves,
which are slightly divergent from the hinge-line.

One of the original specimens of A. quadrula {=A. 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 23 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 35 nmi.,
hinge-line 34, and 30 mm.

This species, in older specimens, resembles A. subdecussatay but differs in the
character of the rays, in the less obliquity, and the wider body. The left valve
somewhat resembles the right valve of Avicula recUculata^ Hisinger, but a com-
parison of the right valves of both species shows them to be different.

The forms here classed under one specific designation were described by Mr.
Connul under different 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 surfiice characters. The usual condition is that of cast^
of the interior or specimens more or less exfoliated, leaving the surface markings
sub(hie<l or obsolescent, and in a few specimens only, have the entire characters
of th(* test in either or both valves l)een observe<l. The older specimens show

LAMELLIBRANCHIATA. 115

an extension of the shell along the post-basal margin which is marked by
concentric strisB and undulations, while the rays become interrupted and obsolete.

After a study and comparison of a very large number of individuals, it has
not been found possible 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, 3, 4 of plate xix, represent the typical
form of A. quadruhj Conrad; the figures 9, 10, 11 of the same plate more
nearly correspond to the A. Boydii^ Conrad. All the righjb valves show the same
degree of convexity and the same surface characters, and vary in form no more
than the variations in the left valve. The extreme forms seen in figures 2G 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 Boydiiy pi. 12, fig. 4. — Sub-rhomboidal, 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 ; posterior wing ample ; posterior extremity of the valves
" acutely rounded."

" Avicula quadrulaj pi. 13, fig. 5. — Sub-quadrate ; length and width equal,
"compressed; lower valve plano-convex, with distant radii of equal size,
" crossed by concentric lines ; posterior wing rather shorter than the width of
" the shell ; anterior wing triangidar, 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 wiii<^ very
" short ; the posterior wing produced, rostrated, acute, with an oblique rib or
" carina on the posterior half, extending to the acutely angulated extremity."
The oblique rib or carina mentioned was probably one of the lateral teeth as
shown in figm^e 12, plate xix.

The Avicula angustirostra of Conrad, cited as occurring at Middleville, Schoharie

116 PALEONTOLOGY OF NEW YORK.

county, is probably from the Hamilton shales at Fultonham; and the only
species from this locality, answering the description given, is A. Boydii^ in
a condition in which the radii and elevated concentric lamellsB are more con-
spicuous than in any specimens from Cazenovia, Hamilton, or any other locality
in Central New York.

Formation and localities. In the shales of the Hamilton group ; abundant at
numerous places in the eastern and central portions of the State.

ACTINOPTERIA PEROBLIQUA.

PLATE XIX, FIG. 31 ; PLATE LXXXIV, FIG. 14.

Aviciiia pernbliqua, Conrad. Jour. Acad. Nat. Sci.. Phiia., vol. viii, p. 235, pi. 12, fig. 1. 1S42.
Acthuipteria peroUiqtui, (Conrad) Hall. Pal. N. V., vol. v, pt. 1. Plates aiid Rxplanations : PI. 19. fig*. 31.

Jan., 1883.

Shell of medium size, 8ub-rhoml)oidal ; body very oblique, narrow-ovate; length
one-third greater than the height ; anterior margin truncate or slightly con-
cave ; basal margin regularly arched and acutely rounded over the post-basal
side.

Valves very convex. Left valve gibbous 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^ inclined forward. Umbonal region
giblK)us, subtending an acute angle.

Ear a small lobe, defined hy a distinct sulcus and shallow, elongate, byssal
sinus. Wing large, triangular, limited by the angular post-cardinal slope
of the valves; margin moderately concave, sloping forward; extremity
angular.

Test (as seen in the specimen, which is a partial cast of the interior),
marked by irregular concentric stria>, which become fasciculate on the wing ;
the surface apparently without rays.

Muscular impression large, sul)-quadrangular below the middle of the post-
cardinal slope, from which, the pallial line curving downward below the

118 PALEONTOLOGY OF NEW YORK.

Right valve convex on the iinil)o, l)econiin{2: depressed below the middle of
the length. Left valve unknown.

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

Beak anterior, Jioute, moderately prominent. UmlK)nal region scarcely
gibbous, subtending an acute angle.

Wing narrow, triangular, elongate, extending nearly to the posterior end
of the shell ; nuirgin concave ; extremity abruptly acute.

Test thin, marked by elevat<?d, sul)-imbricating concentric bands, produced
by the lamellose chanu*ter of the stria\ Crossing these bands, on the
posterior half of the shell, are int^irrupted radiating lines, which indicate the
presence of radii upon the original surfjice. The wing is marked in a
similar manner by strong l>ands, w^hich pass over the hinge-margin, and it
also shows two or three interrupted radiating lines, like those on the poste-
rior part of the body of the shell.

Interior unknow^n.

The specimen described hius a length of 11 mm., height 12 mm., and
hinge-line 10 mm.

This species is allied to A. decussata and A, Boydi^ having the wing charac-
teristic of the Ibrmer; but it is a proportionally shorter form, and the
surftice nuirkings are quite unlike the right valve of any of the forms at present
known.

Formation and locality. In shales of. the Hamilton group, on the shores of
Canandaigua lake, N. Y.

A(^T1N0PTKR1A PERSTRIALIS.
PLATE XXUI, FKiS. '2, 7; AM» FLATK LXXXIV, FKi. 13.

AvViiHtpteria perHtriall% Hall. Pal. N. V., vol. v, pt. 1. Plat«»8 an<l KxplanatioiiH : PI. 23, fijfs*. 2,7.

Jan., 1SS8.

Shell small, sub-rhomboidal ; body sub-ovate, axis slightly curved and oblique
at an angle of about 45° with the hinge ; height about three-fourths the
length of the body ; basal margin broadly rounded ; posterior margin abruptly
curved.

120 PALAEONTOLOGY OF NEW YORK.

ACTINOPTERIA TKNUISTRIATA, n. Sp.
TLATK LXXXIV, FIGS, ft, 6.

Shell small, sub-quadrate ; body short-ovate, oblique at an angle of 60*^ with
the hinge ; length about one-fifth greater than the height ; anterior margin
below the sinus nearly vertical, and then making a broad curve along the
base; posterior margin broadly curved.

Left valve regularly convex below the middle, gibbous on the umlx).
Right valve smaller, nearly equally 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. ITmbonal region gibbous and ample, subtending
nearly a right angle.

Ear small, defined by a distinct sinus and byssal depression, rounded at
the extremity. Wing small, triangular, joining the body below the middle of
its length, not strongly limitiMl ; nuirgin gently concave ; extremity acute.

Test thin, marke<l by fine (*on(*entric stria% and filiform radiations with
wider interspaces, which are niarke<l hy extremely slender intermediate
stria\ On the anterior side the radiating lines are finer, and on the cardinal
margin of the wing they are stronger. The right valve is marked only by
elevated concentric stria\ and the wing by fine radiations, which become
stronger toward the cardinal margin.

One specimen luis a length of 10 nun., height 13 mm., and hinge-line
14 mm.

This species is distinguished from A. perstrialis l)y its erect and more nearly
quadrate form, shorter ear, less extended wing with less concave margin, and
more distant, finer striie.

Formation and locality. In the lower part of the Chemung group at
ItluK'a, N. Y.

122 PALEONTOLOGY OF NEW YORK.

Left valve gibbous ti})ove, gently convex below. Right valve unknown.

Hinge-line straight, about equal to the height of the valve.

Beak at al>()ut the anterior third of the hinge, diFected forward, prominent,
rising above the cardinal line. UmlK)nal region gibbous, nearly rectangular.

E<ar rounded, defined by a distinct byssal depression which extends
forward from the beak. Wing small, joining the body near the posterior
extremity, not strongly defined ; margin gently concave ; extremity produced.

Test marked by fine concentric striao, and undulating or interrupted
filiform radiations, with wider interspaces, which have probably been marked
by finer intermediate strice. The concentric lines are obscure in the cast
and appear as a few irregular concentric undulations.

Interior unknown.

The specimen is 28 mm. in length, 15 mm. in height, hinge-line 16 mm.

Formation and locality. In the lower part of the Chemmig group at Ithaca,

N. Y.

ACTINOPTEUIA EPSILON.
PLATE XXHI, FlCiS. 4, H, (5 ami ((?).

Acti/ufpteria ejwihm. Hall. PhI. N. V., vol. v, pt. I. PIati*M and KxplanationH: PI. 23, figH. 4, 8. Jan., 1883.

Shell of medium size, rhoml)oidal ; Ixnly ovate, oblique to the axis at an angle
of aliout (50^ ; height al)out three-fourths the length ; anterior margin rounded
into a very al)rupt sinus ; l)ase bromlly curved ; post-basal side abruptly
rounded.

Left valve mo<lerately convex. Right valve depressed-convex above, fiat
or concave below.

Hinge-line straight, length somewhat less than the height of the valve.

Beaks anterior, ainite in the left valve ; prominent and elevated above the
hinge. UmlK)nal region giblK)us, sul)tending an angle of less than 60^.

Ear short, define<l by a deep, abrupt byssal depression. Wing triangular,
joining the Ixxly below the middle, not strongly defined ; margin regularly
concave ; extremity acute and produced.

r<A:M.Ji .

124 PALEONTOLOGY OF NEW YORK.

8tria>, with interine<liate finer lines, and hy slender, filiform, nndulating,
<listant ravH, which are more crow<led on the anterior side, becoming finer and
more numerous at the junction of the wing with the Inxly, and a few much
stronger ones along the cardinal line. Rays not present on the ear, which is
markcHl only by the crowded concentric strite. The concentric strise crenu-
late the rays and l)end biickwanl in the interspaces, producing a beautifully
cancellated surface.

The right valve shows two oblique lateral folds or teeth posterior to the
l>eak.

A right valve has a length of 2^) mm. parallel to the hinge, height 28 mm.,
hinge-line al)out o4 nnn. An imperfect left valve luis an approximate length
of 22 mm., height 24 mm., and hinge-line o3 mm.

This species is distinguished by its erect, orbicular form, greait extension of
hinge-line, and marked surface chanu'ters.

Formation and locality. In the h)wer part of the Chemung group at Ithaeii,
N.Y.

ACTINOPTERIA ETA, 1\. sp.
PLATE LXXXIV, KIUS. S-U.

Shell of meilium size, rhomboidal ; Ijody broad and short-ovate, oblique at an
angle of about 45^ ; length about one-fourth greate^r than the height ; anterior
margin below the sinus nearly vertical, curving gradually into the broad
base ; posterior side regularly rounded.

Left valve regidarly convex below, moilerately gibbous above. Right
valve smaller, depresse<i-convex below, gently convex above.

Hinge-line straight, length greater than the height of the shell.

Beak in the left valve sub-anterior, prominent, arching over the hinge; in
the right valve subdued, scarcc^ly rising alK)ve the hinge-line. Umbonal
region giblnms in the left valve, subtending an acute angle.

Kar, in the left valve rounded at the extremity, slightly oblique, defined by
a distinct byssal depression. In the right valve the ear is larger and flat,

LAMELLIBRANCHIA TA. 1 25

strongly limited. Wing comparatively large, extending three-fourths the
length of the valve, not strongly defined ; margin concave ; extreniity pro-
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 lamellsB crenulate the radii, and are arched backward
in the interspaces, producing a beautifiilly cancellated surface. The finer
concentric striaB between the lamellsB are rarely visible, and the spaces
between the rays show, under a lens and in well-preserved examples,
extremely fine, crowded radiations. The radii are also seen in the depression
limiting the ear, and on the wing they are equal to those on the body of
the valve. The right valve is marked by 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 })ody 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 reseml)les A. zeta, but is distinguished l)v
its greater obliquity and much smaller wing.

Formation and locality. In the lower part of the Chemung group at Ithaca,
N. Y.

ACTINOPTERIA THETA, U. Sp.
PLATE LXXXIV, FIGS. 18, 19.

Shell large, sub-rhomboidal ; body broadly ovate, oblique at an angle of about
55^; length aliout one-fourth greater than the height; anterior margin,
below the ear, nearly vertical, curving into the broad ])ase ; posterior (Mid
regularly rounded.

126 PALEONTOLOGY OF NEW YORK.

Left valve moderately convex, depressed below. Right valve smaller and
less convex, nearly flat below.

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

Beaks 8ul)-anterior, prominent, arching over the hinge-line in the left
valve. Umbonal region moderately gibbous in the left valve, subtending an
acute angle.

Ear rounded, a little oblique, defined by a nearly vertical depression. In
the right valve the ear is flat or concave, limited by the abrupt elevation
of the umbo. Wings large, in the left valve extending about three-fourths the
length of the body, and in the right valve joining the body at the posterior
end, without distinct limitation in either valve; margin moderately concave;
extremity slightly produced, angular.

Surface of left valve marked by sharp, elevated, lamellose, concentric
striae, with intermediate finer lines ; and by slender, elevated rays, with wider
interspaces between the primary rays, which are often occupied with one or
two finer lines ; the ear and wing are marked in a similar manner. The
rays are distinctly crenulated, and the int^^rspaces are cancellated by the
concentric lines, which are slightly curved backward. The surface of the
right valve is marked by strong, lamellose, concentric striaB, which become
less conspicuous on the wing. The posterior slope of the body and the wing
of this valve are marked by numerous fine rays.

Interior unknown.

A specimen, with the two valves attached, has approximately a length of
48 mm., height 30 mm., and hinge-line 33 mm.

This species resembles A. eta, but difters in the more extended wing, finer
radii of the left valve, with interstitial additions, narrower interspaces, and
more numerous concentric lamellae.

Formation and locality. In the shales of the lower part of the Chemung
group at Ithac^a, N. Y.

128 PALAEONTOLOGY OF NEW YORK.

ACTINOPTERIA KAPPA, 11. Sp.
PLATE I.XXXIV, FKi. IS.

Shell of iiiediiini size, rhoiii])oi(hil ; l>ody narrowly ovate, oblique at an angle of
less than 4oO ; leiiji^th one-third greater than the height ; anterior margin
oblique, rounded into the broadly curved basal margin ; posterior end abruptly
rounded.

Left valve depressed below, convex from the middle upward. Right valve
unknown.

Hinge-line straight, equiil to the height of the valve.

Beak sub-anterior, prominent, arching over the hinge-line. Umbonal
region moderately gibbous.

Ear short, oblique, rounded anteriorly, defined by a distinct byssal depres-
sion. Wing triangular, joining the lK)dy nearly two-thinls of the length from
the beak ; margin oblique, concave ; extremity produced, acute.

Test thin, marked by fine, concentric, irregularly fasciculating strise, giving
an undulated appearance to the surface, and by filiform, interrupted and
undulating radii, with wider interspaces, which sometimes show fine
intercalated rays. The radii upon the wing are prominent and cancellate<l
])y the concentric striae, and are obsolete upon the ear.

Interior unknown.

The specimen has a length of 30 nun., height 20 mm., and hinge-line
20 mm.

This species differs from A. epsilon, in the greater obliquity, longer hinge-line,
and more distant radii.

Formation and locality. In the lower member of the Chemung group at
Ithaca, N. Y.

LAMELIJBRANCHIATA. 129

PTYCnOPTERIA, Hall.
Ptychopteria Proto.

PLATE XXIII, FIG8. 12, U.

Ptychopteria Proto, Hall. Pal N. Y., voL v, pt. 1. Plates and Explanations: PL 23, fi^fs. 12, 14.

Jan., 1883.

Shell small, rhomboidal ; body narrow-ovate, oblique at an angle of about 35°
with the hinge-line; length more than 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 acute 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 body ; margin scarcely concave ; extremity
obtuse.

Surface marked by fine, regular, elevated radii, which are less conspicuous
on the wing ; also by concentric striie, which are often crowded and lamel-
lose, producing a somewhat undulated character of the surface.

Interior unknown.

A large left valve has a length of 29 mm., height 18 mm., and hinge-line
20 mm. A smaller specimen has a length of 20 mm., height 13 mm., and
hinge-line 14 mm.

This species resembles P. sinitosa, but the anterior end is wider ; the wing
is smaller and not produced at the extremity, and the radii are coarser. These

* In th(» de8<!npti()ii8 of th« sjwi-ies of Ptyclioptoriii and Leptodesina, the term auricle or ear i« not so
applicaLle to the antenor extension as in Aetin(>j)teria and Leioj>teria and the term anterior end has heen
used for that ]>ortion of the shell anterior to the Lyssal sinus.

130 PALAEONTOLOGY OF NEW YORK,

two species are distinguished from the forms which follow by the large anterior
end which is separated from the body by a broad byssal depression.

Formation and locality. In a coarse sandstone, from a bowlder containing the
same associated fossils as a sandstone at Portville, Cattaraugus Co., N. Y. ;
probably of the Upper Chemung group ; Smethport, McKean county, Pa.

Ptychoptkria sinuosa.

PLATE XXm, FIG. 13; PLATK LXXXV. FIG 8.
Ptychiipteria sinutma. Hall. Pal. N. Y., vol. v, pt. 2. Plahvs and Explanations : PI. 23, fig*. 13. Jan.. 1883.

Shell of medium size, rhomboidal ; body narrow-ovate, oblique at an angle of
about 40^ with the hinge ; length more than one-third greater than the
height; ante-byssal margin nearly vertical, curving into the broad sinus;
base broadly rounded ; posterior margin recurving into the wing.

Left valve ccmvex below, gibbous in the middle and above. Right valve
unknown.

Hinge-line straight, length four-fifths the length of the shell.

Beak at about the anterior third of the hinge, acute, directed forward.
Umbcmal region strongly gibbous, limited by the abrupt depression of the
l)0(ly on the posterior side, and by the byssal depression on the anterior side.
Umbonal angle about 30^.

Anterior end large, narrow, rounded, defined by a broad, shallow, nearly
vertical byssal depression ; extremity angular. Wing narrow-triangular,
extending nearly to the posterior extremity of the body ; margin nearly
vertical, slightly concave ; extremity somewhat produced, angular.

Surface marked by fine undulating radii, which are less conspicuous on the
wing, and hy fine concentric lines of growth, which are crowded into sub-
imbricating lamella\ On the anterior side of the body the rays are cancel-
lated by the elevated concentric strige.

The ligamenbil area shows a sharp linear groove extending three-fourths
of its length posterior to the beak, and a narrow cardinal tooth anterior to the
])ejik and parallel to the hinge.

132 PALEONTOLOGY OF NEW YORK.

lines, which are irregularly crowded into sub-imbricating lamellse. On the
anterior end of the valve the radii are cancellated by the concentric striae.

Interior characters unknown, except a narrow groove along the ligamental
area.

A left valve has a length of 41 mm., height 2'4 mm., hinge-line 32 mm.
A similar right valve hjis a length of 40 mm., height 24 mm., hinge-line
34 mm.

This species varies in different conditions of preservation. The obtusely
sub-angular appearance of the i)osterior slope is often exaggerated by lateral
pressure or subdued by vertical pressure. The same is true of the folds of the
wing. In some conditions the radiations are continuous, in others they are
cancellated. In weathered specimens the stria? are sometimes nearly obsolete,
and the concentric lamelhv more prominent.

Formation and locality. In the Chemung group, in a sandstone above the
conglomerate at Uock City, near Salamanca, N. Y.

Ptychopteria Sao.

PLATE XXIII, FUiS. Ifi, 21; AND PLATE LXXXV, FIGS. 14-18,

Ptychftiitfria S<w. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Kxplanations : PL 23, figs. 16, 23.

Jan., 1H83.

Shell of medium size, rhomjjoidal ; body narrow, elongate-ovate, oblique at an
angle of about 45° with the hinge-line ; length one-third greater than the
height ; ante-byssal margin obliquely su])-truncate, gently curving into the
sinus ; base broadly rounded ; posterior margin extended, abruptly recurved
to the wing.

Valves convex ; left valve larger and more convex than the right.

Hinge-line straight, longer than the height of the valve.

Beak in front of the anterior third of the cardinal line obtuse, prominent in
the left valve and arching over the hinge ; less prominent in the right valve,
and rising just above the hinge. Um})o gibl>ous in the left valve, less gibbous
in the right, subtending an acute angle.

134 PALEONTOLOGY OF NEW YORK.

margin liromlly curved ; posterior extromity abruptly or sub-angularly
recurved.

Left valve convex, ji;ihbous on the umix) and obtusely sub-angular alon^
the post-cardinal slope. Right valve less convex, somewhat smaller than the
left.

Hinge-line straight; length al)out two-thirds the length of the valve.

Beak near the anterior fourth of the length of the hinge, directed forward ;
beak of left valve prominent, Jicute, incurved over the hinge-line; beak of
right valve obtuse, and not elevated. Umbonal region of the left valve
gibbous and angular, of the right valve convex, subt'Cnding a very acute
angle.

Anterior end small ; margin rounded ; extremity ivcute. Byssal depression
oblique, directed backward. Wing narrow, triangular, joining the body at the
posterior end; margin obliquely truncates scarcely concave; extremity
jipparently not produced.

Surface marked by fine radiating strise, which are more conspicuous on the
body of the valve and upon the wing, and are very obscure on the anterior
end : these are crossed l)y fine concentric stria) of growth which, at irregular
intervals, are raised into fascicles, usually more conspicuous on the umljo
and post-cardinal slope. On the right valve the nulii are usually obsolete.

Intt>rior unknown, except the usual linear groove along the hinge-line.

A large left valve has a lengtli of 40 mm., height 20 mm., and hinge-line
28 mm. Another is 38 mm. in length, height 20 mm., and hinge-line 27 mm.

In tills species tlie body is more oblique than in P. Salamanca ; the angularity
of the left valve is in a direct line down the middle of the body; the shell
is comparatively narrower ; the extremity of the wing is not produced ; the
byssal depression is more oblique. The want of striae on the anterior end and
their obsolescence on the right valve are marked characters. It is proportionally
much longer than P. Sao, with which it is associated.

Formation and locality. In the lower part of a conglomerate of the Chemung
group at Panama, Chautauqua county, N. Y.

136 PALEONTOLOGY OF NEW YORK.

Ptvciiopteria falcata, n. sp.

I»LATK LXXXV, KKiS. 6, 7.

Shell of inediuiu size, rhomboidal, sub-falcate ; body iiarrow-ovat<?, oblique at
an angle of about 45^ with the cardinal line ; length one-fourth greater than
the height ; anterior and basal margins broadly rounded ; posterior margin
abruptly recurved.

Left valve convex, gibbous al)ove, arcuate. Right valve convex on the
umbo, depressed-convex below.

Hinge-line straight, greatt»r than the height of the shell.

Beak situated at a])out the anterior fourth of the canlinal line, prominent
and arching over the hinge in the left valve; not elevated in the right valve.
Umbo abruptly gibbous in the k»ft valve, subtending an acute angle.

Anterior end limited l)v a shallow, nearly vertical bj-^ssal depression, which
inclines biickward in some specimens; margin convex; extremity acuminate.
Wing triangular, joining the body near the posterior end ; margin straight,
slightly concave just below the hinge-line ; extremity acuto.

Surfiu*,e of both valves marked by fine nidiating strisa, which are less
conspicuous on the wing and obsolete on the anterior end ; and with
concentric striae, which are sometimes strongly lamellose, producing undu-
lations of the surface.

Interior unknown.

A left valve hius a length of 28 mm., height 22 mm., hinge line 24 mm.
A similar right valve hjis a length of 28 mm., height 16 mm., and hinge-line
24 mm.

The shell of this species is comparatively longer, the body more oblique, and.
the wing smaller than in P. Thetis.

Formation and locality. In a sandstone and conglomerate of the Upper
Chemung group at Alleghany Sprhigs, Warren county. Pa.

138 PALEONTOLOGY OF NEW YORK.

PtVCHOPTERIA EuDORA, 11. «p.

I»LATK LXXXV, FIO. 9.

Shell of medium si/A*, rhomboidal ; body 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 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 thinl of the hinge directed forwanl,
rising al)Ove the cardinal line. Umbo narrow and gibbous, subtending a
very acute angle.

Anterior end small, limited l)y a well-marked and oblique byssal depression ;
extremity acute. The distance from the byssal sinus to the cardinal margin
is one-half the greatest height of the 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)liquely truncate ; extremity
not produced.

Test thin, marked l)y nwlii which are very fine and undulating on the
])ody and wing, while they are obsoleti^ on the anterior portion ; these are
cancellated by fine concentric stride, which on some portions are fasciculate,
and very conspicuous on the anterior end.

Interior unknown.

The specimen described hiis a length of 31) mm., height 20 mm., and
hinge-line about 23 mm.

This species bears considerable reseml)lance to P. EucraUy but its anterior end
is proportionally narrower, and it may also be distinguished by the absence of
a continuous angularity along the body, the more abrupt recurving of the post-
basal margin, the more oblique truncation of the wing, and the less conspicu-
ous surface markings. It differs from P. Spio in its more gibbous umbo and

. j

140 PALEONTOLOGY OF NEW YORK.

This specioH is distinf^iiished by the j^reat oontnwt in the eoiivexitj of the
two valves. The left valve is stronjjjly aujj^ular and elevated from the umbo to
the posterior extremity ; the right vadve is conspicuously alate.

Formation and locality. In a coarse sandstone of the Cheuunig group, near
Salamanca, N. Y.

PtYC^HOPTEKIA TRir.ONALIS, u. sp.

PLATE LXXXV, FUi.S. 34. 85.

Shell snndl or of medium size, rhomlK)idal ; Inxly sulHcylindrioal, oblique at an
angle of about 4r)0 with the hinge-line ; length one-third greater than the
height; anterior margin rounded, gently curving into the broad ba^e, with
a faint ])yssal sinus ; ix)sterior margin almost rectangularly recurveil.

Left valve convex, gibl)ous on the um))o, and angidar from the umbo to
the i)ost-biisal extremity. Right valve unknown.

Hinge-line straight, length greaU^r than the height of the valve.

Beak in front of the anterior thinl of the hinge, obtuse, prominent and
incurved. Uml)()nal region gibbous, subtending an luuite angle.

Anterior end short, rounded, indistinctly separated from the Ixxly by an
obscure byssid sinus. Wing large, triangular, joining the l)ody of the valve
near the posterior extremity ; the limiting furrow is very distinct in young
shells, and obscure in older examples; margin somewhat obliquely trunc^ite;
extremity not produced.

Surface marked by fine nulii, which are obscure or obsolete on the anterior
part of the shell ; also l)y concentric strias which are somewhat acutely
recurved on the angular portion of the body, and in older shells are fiiscicu-
late, producing an undulated jispect.

Interior unknown.

A small left valve has a length of 1(5 nnn., height 11 mm., and hinge-line
13 mm. Another specimen has a length of 80 mm., height 18 mm., and
hinge-line 25 mm.

LAMELLIBRANCHIATA. 1 41

This species has some resemblance to P. alata in the left valve, but its height
is comparatively greater, the wing more truncate, and not produced at the
extremity.

Formation and locality. In a shaly sandstone above a conglomerate in tlie
upper part of the Chemung group at Panama, Chautauqua county, N. Y.

Ptychopteria elongata, n. sp.

PLATE LXXXV, FIGS. 10-13.

Shell of medium size, sub-rhomboidal, elongate; body sub-cylindrical,
oblique at an angle of 30° with tlie 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 margui
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. Umbonal angle acute.

Anterior end short, produced and acute at the extremity, limited l)y a
distinct oblique byssal depression. Wing narrow-triangular, joining the body
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
obliquely truncate.

Surface marked by fine radii, which are distinctly cancellated by the con-
centric striae, when the specimen is tolerably well-preserved ; also by concen-
tric lines of growth which, at somewhat regular intervals, are sharply elevattMl.
The radii are obsolete on thi^ anterior of the valve, and the concentric stria*
are lamellose.

142 PALEONTOLOGY OF NEW YORK.

The connect-ed valves show a narrow ligamental area extending half the
length of the hinge. Other characters of the interior are unknown.

One specimen has a length of 35 mm., height 21 mm., and hinge-line 25
mm. Another has a length of 25 mm., height 13 mm., and hinge-line 20 mm.

This species resembles P. Eucrate, but is less gibbous, more elongate, and
without angularity along the body.

Formation and locality. In a conglomerate of the Chemung group at Panama,
Chautauqua county, N. Y.

Ptychopterta galene, n. sp.

• I»LATK LXXXV, FKis. t»-31.

Shell small, rhomboidal ; body sub-elliptical, oblique at an angle of about 40°
with the hinge ; height greater than half the length ; ante-byssal margin
oblique, curving gently into a shalh)w sinus ; base regularly rounded ;
posterior end abruptly recurved.

Left valve convex, moderately giblmus on the umbo, and sub-angular along
the upper half. Right valve less convex al30ve, depressed-convex in the
lower part.

Hinge-line straight, length greater than the height of the valye.

Beaks near the anterior third of the 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, nearly vertical byssal depres-
sion ; extremity acmte. Wing wide-triangidar, joining the body near
the posterior end ; limiting furrow distinct ; fold wide and moderately
prominent ; margin obliciuely truncate, very slightly concave just below^ the
hinge-line ; extremity angular.

Surface of the body and wing marked by regular, fine, interrupted or
undulating nulii, which are obscure or obsolete on the anterior portion ; also
by very fine concentric lines, which are crowded into irregular fascicles and
are lamellose on the anterior part of the valve.

144 PALEONTOLOGY OF NEW YORK.

the limiting furrow distinot; the told gentle and the upper part of the wing
flat or slightly convex ; margin obli(iuely truncat-e, concave just below the
hinge ; extremity slightly produced.

Surface marked by fine unifc^rm radii on the Inxiy and wing, which are
nearly obsolete on the anterif)r end, and wnnetimes mt<?rrupt4Kl (m the IkkIv
bv varices of growth ; also by fine ccmcentric striae which are acutely
recurved over the angular ptKsterior slope of the Ixnly, and crowde<i into
fascicles at irregular intcTvals, producing an undulat^nl api)earance.

Interior unknown.

A large left valve has a length of •')2 mm., height 28 mm., and hinge-line
30 mm. A right valve in the same ass(K*iati(m has a length of 40 mm.,
height 20 mm., and hinge-line 'io mm.

This species somewhat resembles P. trigonalis^ but the posterior extremity is
more produced, and the wing more obliquely truncate on the margin. The
right valve in general aspect resembles the right valve of P. a/oto, but the left
valve is very dissimilar. The distinguishing characters are its large rhomboidal
form, extreme gibbosity and arcuation of the left valve.

Formation and locality. In a compact sandstone of the Upper Chemung group,
in the lower betls as seen at Warren, Pa.

Ptychopteria spatulata, n. sp.

PI.ATK LXXXV, FUi. a).

Shell large, elongate, rhomboidal ; body sub-elliptical, oblique at an angle of
about 30^ with the hinge ; length more than (me-third greater than the
height; ante-byssal margin oblicpie, gently curving into the sinus, thence
extending into the broa<lly curves! basal margin ; posterior end rectangularly
or acutely recurved.

Left valve moderately convex, slightly gibbous above. Right valve
depressed-convex, more sub-angular along the post-cardinal slope, and smaller
than the lefY.

146 PALEONTOLOGY OF NEW YORK.

ba^al margin is broadly roimdwl ; 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 difference in the valves is also
shown in the direction of the strioB of growth.

Hinge-line straight, alx)ut 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. Uml)onal region of the left valve moderately gibbous,
subtending 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 truncate, concave just below the hinge-line, which is
abruptly produced.

Test thin, marked hy fine, interrupted or undulated radii, which are more
strongly marked on the Ixxly and wing, and obsolete on the anterior of the
valve ; the surface is also marked by fine concentric strioB, which are crowded
into fascictles at uneciual distances, undulating the surface ;'they turn abruptly
r>utward, just below the hinge, and are lamellose on the anterior part of the
valve.

Interior unknown.

A HjHMnmen preserving both valves has a length of 45 mm., height 28 mm.,
binge-line ^55 mm. The right valve is somewhat smaller. Another
-|K?irimen has a length of 42 mm., height 28 mm., hinge-line 36 mm.

This H|>e<!ies resembles in form P. SaOy but is larger, the wing furrow more
'tronjriy defined on the left valve, the concentric lines more acutely recurved
;if tli^r \nit^ii\ angle, and the radii are finer and more numerous.

Formatimi and lorality. In the Upper Chenmng gi'oup, the middle beds of
•/,<• -i'ri^v-, iin H4»cn at Warren, Pa.

148 PALEONTOLOGY OF NEW YORK.

Ptychopteria Thalia, n. sp.

PLATE LXXXV, FIGS. :», 3S.

Shell of medium size, rhomboidal ; body ovate, oblique at an angle of about 45°
with the cardinal line ; length one-third greater than the height ; anterior
and basal margins broadly rounded, slightly impressed by the byssal sinus ;
post-biisal extremity sub-angular, abruptly recurved.

Left valve extremely giblx^us, the point of greatest convexity is one-
third of the height from the beak. Right valve convex on the umbo,
depressed-convex below.

Hinge-line straight, a little less than the greatest length of the shell.

Beak situated at the anterior third of the hinge, 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-umbonal furrow ; margin obliquely truncate, 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 obsolete 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 unknown.

A left valve has a length of 25 mm., height 17 mm., and hinge-line
23 mm. A small right valve has a length of 20 mm., height 13 mm., and
hinge-line 16 mm.

This species resembles P. perlala but the wing is comparatively smaller,
extremity not acuminate, and the umbo more gibbous.

Formation and locality. In a sandstone of the Upper Chemung group at Alle-
ghany Sprinj^s, Warren bounty, Pa.

r-^*

LAMELLIBRANCHIATA. 149

PtYCHOPTERIA GIBB08A, n. Sp.
PLATE LXXXV, FIG. 6.

Shell small, rhomboidal ; 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 an undulated appearance ; and are
strongly lamellose on the anterior end ; the radiating striae 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.

.'._ _■ •

1-30 PALEONTOLOGY OF NEW YORK.

Ptychofteria lobata, 11. sp.

I»LATK I.XXXV, FUi. :17.

Shell siiiall, !jub-rhoinlx)i(laI ; body hroadly ovate, oblique at an angle of about
55° with the canlinal line; length somewhat {greater than the height; anterior
niartrtn sub-truncate ; lisiso broadly rounded ; posterior margin rectangularly
recurved into the wing.

Left valve very gibbous; the point of greatest convexity iajust below the
uuiIkj. Right valve unknown.

Hinge-line straight, length nearly eijual to the length of the valve.

IJeak situated anterior to the middle of the hinge, prominent, inclined
forward, and arching over the margin of the valve. Umbonal region ample,
gibbous, subtending an iicute angle.

Anterior end large, limited by a browl, undefined byssal depression ;
margin convex ; extremity apparently obtuse. Wing small, joining the body
at the; pf)sterior end, strongly limited by 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 ant<;ri(jr end ; and by stria) of growth which are somewhat lamellose on
the anterior of the shell.

Interior unknown.

A left valve of this species has a length of 13 mm., height 10 mm., hinge-
line 1 1 mm.

7'lji- *«fMrci(?s differs from P. gibbosa in its shorter, truncate anterior end, and
'tfo/c'rr fold on the wing, which is comparatively stronger than in any species
•, <•? ob^'-rved.

I'orrn^Uum nrul locality. In the sandstones of the Upper Chemung group,
'Mixrft'ti 'roiiiity, Pa.

LAMELLIBRANCHIATA. 151

Ptychopteria Vanuxemi, n. sp.

PLATE LXXXV, FIG. 36.

Shell large, sub-triangular ; 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 vci*y 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, lamel-
lose concentric strise. The concentric striae 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 Ptermites.

Formation and locality. In the highest beds of the Upper Chemung group at
Warren, Pa.

152

PALEONTOLOGY OF NEW YORK.

Ptvchopteria expansa.

PLATE XXIII, FIGS. 10. 11.

PhjvhopttrUi vxiHvuta, Hall. Pal. N. V., vol. \\ pt. 1. Plates and Explanations: PI. 28, tlg». 10, 11.

Jan., 188.S.

Shell of inediuiu si/.o, sub-rhonihoidal ; body ovjite, oblique at an angle of
about (50° witb tho hinj!;e-linc» : length one-fifth greater than the height ;
ante-byssal margin oblique, gently curving into the shallow sinu8; basal
margin })roiully rounded to the base of the wing.

Left valve convex below, gibbous above. Right valve unknown.

Hinge-line straight, central, length greater than the length of the valve.

Beak at about the anterior fifth of the hinge, inclined acutely forward,
moderat-ely prominent. Uinbonal angle iwnite.

Anterior end small, surface convex to the nearly vertical byssal depression
which extends half way to the base of the shell ; extremity compressed and
iicute. Wing very large, triangular, extended, joining the body at the
posterior extremity ; the furrow obscurely marked ; margin gently concave,
extending backward ; extreinity produced.

Surfiu'e marked by regular strong radii and by concentric lines of growth.
The concentric striae are somi^times crowded into irregular fascicles, giving
an undulated appearance to the surfju'e ; the nulii are strong on the umbonal
slope, less conspicuous on the wing, and on the antero-basal portion they are
interrupted, and oblique to those on the umbo.

Interior unknown.

The specimen described has a length of 27 mm., height 22 mm., and hinge*
line 30 mm.

This species is distinguished b^* its erect form, large and extended wing, and
peculiar (character of surlUce markings. The furrow of the wing is indicated
only by a wider depression between the nwlii, and a stronger ray marks the
Ibid.

Formation and locality. In a coarse sandstone of the Chemung group near
Smethport, Pa.

LAMELLIBRANCHIA TA. 1 53

GLYPTODESMA, Hall.

Glyptodesma erectum.

PLATE XI. FIGS. 1-10; PLATE XII, FIGS. 1-3, 5-9; PLATE XIII, FIGS. 1-4, 13-15; PLATE XXV. FIGS. 14-17;

PLATE LXXXVI, FIGS. 1-8; AND PLATE LXXXVII, FIGS. 1-3.

Avicula ei-ecta, Coitrad. Jour. Acad. Nat. Sci., Phila., p. 238, pL 12, fig*. 5. 1842.
** crudformiSf Conrad. Geolog. Surv. N. Y. : Annual Report, p. 54. 1841.
Adinode^ma erectum (Conrad), Hall. MS., Pal. N. Y. 1877.

S. A. Millkr, in Cat. Amer. PaL Foes. 1877.
** cruc\fanne (Conrad), Hall. MS., Pal. N. Y. 1877.

*' " 8. A. Millkr, in Cat. Amer. Pal. Foss. 1877.

Glyptodesma erectum (Conrad), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 11, figs.

1-10 ; pi. 12, figs. 1-3, 5-9 ; pi. 13. figs. 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 ; basal 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.

154 PALjEONTOLOGY OF NEW YORK.

These striae become more conspicuous upon the margins and upon the wings,
where they are often highly lamellose. The distant lamellse which mark
the body of the shell are sometimes continued upon the hinge, and becoming
stronger, ciu^ve over the margin, giving it a sharply annulated aspect,
which, when preserved in the impression of the hinge-border, might be
mistaken for a more important organic marking. Partially exfoliated shells
show some obscure radiating lines which l>elong to the intimate shell-structure,
and are not external. (These stria) 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 pits radiating
grooves extend toward the margin of the shell.

Ligameutal area extending the entire length of the hinge, comparatively
wide, grooved longitudinally with fine, continuous parallel lines. Hinge with
one or two linear, slightly o})lique, hiteral teeth on the posterior 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
90, 70, and 81 mm., height 100, 99, and 81 mm. ; hinge-line 100, 90, and 90
mm. An example of medium size has a length of 55 mm., height 76 nun.,
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 att^iins 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 usually 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 (jf
lateral teeth varying from one to three ; the cardinal wrinkles and creuulations
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 ligamental
area.

Formation and localities. In the shales and shalv sandstones of the Hamilton
group, from the eastern limit of the formation as far west a,s Canandaigua
lake ; it is extremely abundant in Albany and Schoharie counties ; Cazenovia
and Hamilton, in Madison county, 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 JCII, FIG. 4; and PLATE \m, FIGS. 5-Jl.

Glyptodesina erectwrit v&r. obliquuin, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. J 2, ti^'*.

4 ; pi. 18. figs. r)-ll. 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 distiiu»tly
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 this variety are uniformly smaller. They have been
observed mainly in the soft shales at Pratt's falls, Onondaga county, while the
large erect forms are common in the coarse shales and grit*? of the group in the
eastern portion of the State, and in Madison county.

In examining and comparing the extreme forms, the difference is striking
and distinctive. (For example, the erect forms on plate xi, and the 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 imder 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. obliqtmm.

The description of Avicula erecta, and A. cruciformiSj given by Mr. Connul,
are as follows, loc. cit. :

" Avicula erecta, 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, iicut^jly 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 cruciformis, Conrad, loc. cit, : " Elevated, with both ears greatly
" elongated. Locality — Near Oneonta : This species is remarkable for the great
" proportional height ; very little oblique. Height 3^ inches."

The name of A. cruciformis has precedence in point of time, but the name
of A. erecta has been adopted because the description and figure entitle it to
recognition, and the former name is only applicable to the more extravagant
forms of the species illustrated on plates xi and xii.

158 PALJEONTOLOGY OF NEW YORK.

LEIOPTERIA, Hall.

LeIOPTERIA LiBVIS.
PLATE XVII, FIGS, ft-ll ; AND PLATE XX, FIG. a.

Avictda /crirw, Hall. Gt»olojf. Surv. N. Y. : Rep. Fourth Diat., p. 181. 1843.
Ptenmites IcBvUt, (Hall) S. A. Millkr. Cat. Aiiier. PaL F(w^., p. 2(>2. 1877.
Leiopteria IcBois, Hall. PaL N. Y., voK v, pt. 1. PlatoH and Explanations: PL 17, fig». 5-n. Jan., 1883.

Shell small, siib-rhomboidal ; body obliquely ovate ; length and height nearly
equal ; greatest length below the middle ; margins regularly rounded, some-
what extended on the post-basal side.

Left valve more convex than the right ; the greatest convexity in both
valves is above the middle.

Hinge-line straight on the posterior side of the beak, turning abruptly
downward in front ; entire length greater than the length of the shell.

Beaks obtuse, rounded, inclined forward, situated at the anterior third of
the shell, that of the left valve quiti^ prominent. Umbonal region of 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 by a distinct rounded sulcus
and broad byssal sinus ; margin rounded ; extremity obtuse. Wing trian-
gular, flat, limited by the post-umbonal slope ; margin concave ; extremity
acute.

Test thin, marked with distinct concentric striae of growth, which are
crowded and conspicuous on the wings. There are often obscure traces of
radii, which are more distinct on the wing in casts or exfoliated specimens.

Ligamental area narrow, with a single distinct groove. Some specimens
apparently indicate the existence of an oblique lateral tooth on the posterior
side of the umbo.

One specimen hjus a length of 11 mm., height 12 mm., hinge-line about
10 mm. Another has a length of 10 mm., height 11 mm., and hinge-line 12

160 PALEONTOLOGY OF NEW YORK.

This species bears some general resemblance in form to AcUnopteria decussata
and A. BoydU but is distinguished by the absence of rays. It differs from
L. Greeni, fig. 9, pi. xx, in its more oblique 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.

PLATE X\. FIIJS. 0. li; ANI> PLATE LXXXVHI, FIGS. 21, «.
Ldiypteria Oreeni, Hall. Pal. N. V., vol. v, pt. 1. PlatoH and Kxplanations : PI. 20, tigs. 9, 12. Jan., 1883.

Shell large, sub-rhomboid al ; body moderately oblique, broadly ovate ; length
a little greater than the height ; margins regularly rounded, somewhat
extended post^^riorly.

Valves moderately and nearly equally convex ; similar in character.

Hinge-line straight, equalling or greater than the length of the shell.

Beaks acute, anterior, inclined forward, arching over the hinge in the
left valve ; less prominent in the right.

Ear short, limited by a sulcus and sinus which is deeper in the right valve.
Wing large, triangular, defined only by the abrupt bending of the strise ;
margin concave ; extremity acute.

Test thin, marked by numerous, closely arranged, concentric lines of
growth, and, at somewhat regular intervals, by sharp, projecting lamellose
striae; and corresponding with these, are regular concentric undulations,
which are shown strongly on the cast, and ])ut partially seen on the exterior
surface. The stria) mark the wing in the same manner as the body, and are
crowded on the ear.

Ligamental area narrow, marked hy a single groove.

A large specimen mea^sures 57 mm. in length, 51 mm. in height, hinge-
line 58 mm.

This species reseml>kvs L. Conradi, ])ut is broader, with comparatively greater
height, less olHiquity, and less extended posterior wing.

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

LAMELLIBRANCHIA TA. 161

Leiopteria Rafinesquii.

PLATE XV, FIG. 11 ; PLATE XX, FIGS. 6, 7 ; and PLATE LXXXVIII, FIGS. 27, 28.

Leiopteria Rafinesj^^^U Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 15, ti^. 11 ; ]>!. 20,

figs. 6, 7. Jan., 1883.

Shell of medium size, sub-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 gibbous. 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 beak to the posterior
extremity it is about equal to the lengtli of the shell.

Beak of the left valve acute, directed forward, very prominent, situated
at the anterior extremity of the shell. Umbonal region gibbous, subtendiiif^
an acute angle.

Ear short, convex, obtuse, with a broad 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 striae are 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 striae 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 dimeii-

162 PALEONTOLOGY OF NEW YORK. ^

sions: length 39, 34, and 25 mm., height 41, 38, and 26 mm., hinge-line 37,
39, and 26 mm. The right valve, mentioned above, is 23 mm. in length, 25
mm. in height, and 23 mm. along the hinge-line.

This species resembles the two preceding, but the form of body is more
narrowly ovate, the obliquity appears to be intermediate between the two;
the ear is less strongly defined ; the 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 Sayi, n. sp.

PLATE LXXXVIII, FIGS. 16-20.

Shell above the medium size, sub-orbicular ; body very broadly ovate, scarcely
oblique; height greater than the length; margin nearly straight in front,
thence regularly rounded.

Left valve very convex, gibbous in the umbonal region. Right valve
smaller and less convex.

Hinge-line straight, longer than the length of the shell.

Beaks acute, situated near the anterior extremity of the hinge, prominent,
inclined forward, arching over the hinge-line. Umbonal region ample, sub-
tending a right angle.

Ear small, bending downward, defined by a broad, shallow sulcus. Byssal
sinus narrow. Wing large, triangular, greatly extended along the hinge-line,
defined by the retral bending of the striae ; margin concave ; extremity acute.
The wing of the right valve is very broad, flat, and much extended ; not dis-
tinctly defined.

Surface marked by fine, closely arranged striae of growth, with distant,
elevated lamellae, which are extensions of strong fascicles of strias. These
leave angular concentric folds and undulations in the casts. The striae are

164 PALEONTOLOGY OF NEW YORK.

Leiopteria Dekayi.

PLATE XIX, FIG. 1 ; PLATK XX, FIUS. Id-lS ; and PLATE LXXXVIII, FIGS. 5-10.

Leiopteria Dekayi, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 19, &g. 1 ; pi. 20, figt*.

1(5-18. (19 in error). Jan., 1883.

Shell of medium size, sub-rhomboidal in general form ; body narrowly ovate,
oblique; length about equal to the height; anterior margin nearly vertical
for one-third the length of the shell, thence broadly rounded over the basal
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 the wing not strongly defined.

Hinge-line straight, length a little less than the length of the shell
measured from the anterior side of the beak to the extremity of the wing.

Beaks anterior, acute, prominent, inclined forward. Umbonal region
gibbous above, regularly convex below, subtending an acute angle.

Ear bending downward, with a strong fold in the upper part, limited by
a broad undefined sulcus and shallow byssal sinus. Wing triangular, flat,
defined by the abrupt retral bending of the striae and a depressed line along
the post-cardinal slope ; margin concave ; extremity acute.

Test thin, marked by fine regular concentric strise, which at unequal
intervals are crowded into fascicles, giving an undulated aspect 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 fasciculate 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 younger specimens
from the shales, the surface shows fine regular striae which gradually become
fasciculate as the shell increases in size.

Ligamental area narrow, marked by fine striae ; below this area is a narrow
oblique fold or lateral tooth.

The three specimens figured on plate xx, have respectively the following
dimensions: length 37, 31, and 29 mm., height 37, 30, and 30 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. Rafinesquiiy 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, an,d the post-cardinal slope is more strongly defined.
There is a general resemblance with L. Bigsbt/i, but the body and hinge-line
are longer, the body narrowing more rapidly from the base, and the stria3 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 distributed from
the eastern to the central portion of the State.

Leiopteria Bigsbyi.

PLATE XX, FIGS. 3, U, 1»-15 ; and PLATE LXXXVm, FIG. SJ.

Leuiptena Bigsbyi ^ Hall. Pal. N. Y., vol. v, pt. 1. Plates ami Explanations: PI. 20, figs. 3, 11, 13-1.").

Jan., 1883.

Shell larger than medium size, sub-rhomboid al ; 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 gibbous upon the umbo, less convex towards the base. Right
valve gibbous on the umbo, depressed-convex below, shorter than tlie left
valve.

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

Beaks anterior, acute, prominent, rising above the hinge-line, inclined tor-
ward. Umbonal region prominent, subtending an angle of about 55^.

Ear short, bending moderately downward, with a strong fold at the upj)er
side, limited ])y a broad, undefined sidcus. Byssal sinus shallow. Wing-
triangular, wide, nearly fiat ; margin concave ; extreinity acute. The wing

166 PALEONTOLOGY OF NEW YORK.

of the right valve is less defined than in the left, and the byssal sinus is a
little deeper.

Test thin ; specimens partially exfoliated, or occurring in the condition of
ciists, show sharply elevated, lamellose, concentric striae, which are very dis-
tinct on the wings, and crowded and somewhat fasciculate on the anterior
side and ear. No intermediate finer striae have ])een observed. In well-
preserved specimens the sharp lamellae have undulating margins.

Interior unknown. Ligamental area marked by a single groove.

A large specimen has a length of 43 mm., height 50 mm., hinge-line 37 mm.
Another example has a length of 32 mm., height 33 mm., hinge-line 30 mm.
In the younger shells the height is proportionally somewhat less than in
the older ones.

This species, compared w ith the preceding, has a greater height of body and
shorter hinge-line, and differs in the conspicuous, sharp, concentric lamellae.
In this species the concentric striae do not produce the folds and undulations
which are characteristic of L. Rafinesquii and L. Greeni.

Formation and localities. In shales of the Hamilton group at Pratt's falls,
Onondg-ga county, and in the coarser beds at Schoharie, N. Y.

Leiopteria Mitcfielli.

I*LATK XX, FIG. S; AM) PLATK, LXXXVUI, FIG. 26.
IjeUypt^ia Mitrhelli, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. iTO, fig. 8. Jan., 1883.

Shell large, sub-rhomboidal ; body ovate, moderately oblique ; height greater
than the length ; anterior margin 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 end slightly extended.

Left valve gibbous on the umbo, sloping from highly convex above to
moderately convex below. Right valve unknown.

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

Beak anterior, acute, inclined forward, prominent. Umbonal region prom-
inent, subtending an acute angle.

LAMELLIBRANCHIA TA. 167

Ear short, limited by an undefined sulcus and shallow byssal sinus. Winj»;
large, triangular, nearly flat, defined by the retral curving of the lamellose
striaB ; margin moderately concave ; extremity abruptly acute.

Test thin, marked by regular concentric lines of growth, with distant,
lamellose strisa, which are raised into thin, sharp elevations correspondinjz;
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 49 mm., hinge-line about
47 mm.

This species, in general proportions, resembles A. Bigsbyi ; it differs in the
larger and more extended posterior end, with striae 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, sub-rhomboidal ; 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, j!;ibbous on the umbo. Right valve unknown.

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

168 PALEONTOLOGY OF NEW YORK.

Beak anterior, acute, prominent, inclined forward, rising above the hinge.
Umbonal region gib])ous, abruptly limited on the anterior side by the sulcus,
and on the posterior side sloping rapidly to the wing.

Wing large, flat, triangular, joining the body of the valve below the
middle of the height, limited by the gently retral curve of the strisd ; margin
moderately concave ; extremity acute or mucronate.

Surface marked by regular, equidistant, undulating, lamelliform, concentric
expansions, which become crowded, liner, 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 imbricating, they give an
appearance of radiation.

Interior unknown.

The specimen described has a length of 35 mm., height 37 mm., and hinge-
line about 29 mm.

In general a><pect, this species resem])les Adinopteria 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 species the wing is
marked with strong nidii and a few lines of growth.

These comparisons are nuide from similar casts of the interior of both species.

Formation atid locality. In the coarse grits of the upper part of the Hamilton
group, in the northern part of Schoharie county, N. Y.

Leiopteria Leai, n. sp.

PLATE LXXXVin, FIUS. 2*, -.»:>

Shell small, sub-rhomboidal ; Ijody l)roiully ovate, very moderately oblique ;
height much greater tlian tlie length ; margin regularly rounded from above
the middle on the anterior side, to a similar point on the opposite side of the
valve ; post-basal margin slightly produced.

Left valve very convex; gibbous from below the middle to the umbo.
Right valve unknown.

LAMELLIBRANCHIATA. 169

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

Beak anterior, acute, rounded, inclined forward, prominent. Unibonal
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 strioB, 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 umbo and more convex below than
any of the forms described in this group; the wing is shorter and smaller,
with less extension along the posterior 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 the
southern part of Schoharie county, N. Y.

Leiopteria Gabbi, n. sp.

PLATE LXXXVIll, 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 being 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.

170 PALAEONTOLOGY OF NEW YORK.

Beaks acute, prominent, directed forward, anterior to the 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 from 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 strisB ; margin
gently concave ; extremity acute.

Test thin, marked by fine concentric stria), and at regular intervals by
stronger elevated striie, which give to the macerated shell, and the cast of the
interior, a regular banded surface. These stronger striae are closely arranged
on the anterior side and ear, while on the posterior side they preserve their
equidistant chanK-ter. The right valve is very distinctly marked by the
elevated concentric strite. In l)oth 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 18 mm., height IG mm., hinge-line about
10 mm. Another example has a length of 12 mm., height 13 mm., and
hinge-line alx)ut 11 mm.

The 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 of the Hamilton group ; shores of
Canandaigua lake, and at Norton's Landing, Cayuga lake, N. Y.

Leiopteria Oweni.

PLATE XX, FIG. 10.
Leiopteria Owenij Hall. Pal. N. Y., v<»l. v, pt. 1 Platt's and KxplanatioiiH : PI. 20, fig. 10. Jan., 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.

' below, flat almve, bt'coiiiing convex towards the beak, which is low and
dcariiely rfin;hcs the hinge.

Hiiige-liiii' stniight, about equal to the leiif^tli ol' the valve.

Bcaki! anterior, acute, directed forward.

Ear large, extended, ilefined by a broad suh;u« and marked bystial sinus.
I Wing large, expanded ; margin conoave ; extremity abruptly acute.

Tect thin, marked by fine concentric striiu of growth, which on some
[partw of the eurfat^e are t-rowdud into fiiaei<dea, producing ridges or undula-
tions. Therte are somewhat regular over the whole of the left valve,
' and stronger on the anterior part; on the right valve they are without
regidarity. The right valve also shows radiating lines which appear to
belong to the shell structure, and are quite conspicvious in partially exfoliated
Bpecimcns. The strisa are crowded and lamollose ou the anterior margin
and atijaceut to the byssal siuus ; on the wuig they are closely antl evenly
arranged.

Interior unknown.

One of the imperfect specimens described him an approximate length of
61 mm., height 55 mm., and hinge-line about 55 mm. ; the measurement
along tJie axis of the body, from the beak to the post-basal margin, is
75 mm.

The two Hpecimeins observed are erushod, and the characters of the lei't valve
are very much obscured, whih' tlie right valve preserves more nearly itjs true
proportions. It differs 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 locality. In the t-oft shales of the Hamilton group, Canandai-
gua lake, Ontario county, N. Y.

172 PALEONTOLOGY OF NEW YORK.

Leiopteria Chemungensis.

PLATE XXII, FIGS. 17. 18.

Anieula ChnnungenJtis, Vanuxkh. Geolog*. Sui-w N. Y. : Rep. Thini Dmt., p. 182, tig. 49, No. 3. 1842.
Lei(}p(eria nitida, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanationfl : PI. 22. tigs. 17, 18.

Jan.. 1883.

Shell of medium size or larger, rhomboid-ovate ; body elongate-ovate, oblique at
an angle of about 60° with the hinge-line ; length equal to more than four-
fifths of the height; anterior margin nearly vertical for about one-half
the height of the shell and broadly rounded on the base ; post-basal margin
abruptly rounded.

Left valve convex, gibbous in the umbonal region. Right valve smaller,
less gibbous.

Hinge-line straight, a little longer than the 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, bending slightly downward, defined by a broad
distinct sulcus ; extremity rounded. Ear of right valve flat. Byssal 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 striaB; margin deeply concave in the middle; extremity
produced and acute.

Surface, in a partial cast, marked hy fine concentric strisa, which are
crowded and lamellose on the ear, distinctly marked on the wings, and
appearing on the body as distinct undulations : these in the perfect shell
may have been sharp lamelliform striae.

Interior unknown.

A specimen of the left valve has a length of 30 mm., height 35 mm.,
hinge-line 47 mm. ; the body from beak to post-basal extremity measures
43 mm.

The specimen figured is the original of Avicula Chemungensis^ Vanuxem. 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.

LAMELLIBRANCHIA TA. 173

In the volume of Plates and Explanations this species was referred to
L. Dekayi in the absence of the original specimen, which has since l)eeii
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 LXXXVIII, FIG. 29.

Shell above 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 wing.

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 striaB 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 descril)e(l has a lon<;th of o3 mm., height 42 mm., and

hinge-line o2 mm.

174 PALEONTOLOGY OF NEW YORK.

This species differs from L. Chemtmgensis in ite more erect form, and the ear
is without the strong fold and marked sulcus of that species ; the wing is also
less extended and the margin less concave.

Formation and locality. In the Chemung group in the valley of Cayuta creek,
Broome countv, N. Y.

Lkiopteria Torreyi, n. sp.

VhXTK XXII, FKiS. «, 7; am> PLATE LXXXVIH, VUi. l\.

Shell of medium size, rhomboidal, sub-falcate ; body narrow-ovate, arcuate,
oblique at an angle of less than 45° with the hinge ; height equal to about
two-thirds of tlie lengtli ; anterior and basiil margins broadly curving from
the byssal sinus ; post-l)asal margin produced and abruptly recurved.

Left valve very convex, gibbous in the middle and above. Right valve
unknown.

Hinge-line straight, about equal to the height of the valve.

Beak sub-anterior, directed forward, acute, prominent and arching over
the hinge. Umbonal region narrow, ventricose, well-defined, subtending an
acute angle.

Ear large, bending downward, marked by a strong oblique fold, limited by
a broad, vertical l)yssal depression and shallow sinus ; margin convex ;
extremity apparently obtuse. Wing joining the l>ody above the posterior
extremity, limited by the nearly vertical post-umbonal slope, which makes a
more or less marked sulcus ; margin concave ; extremity produced, acute.

Surface marked by fine stria? of growth which are somewhat regularly
lamellose on the body of the valve.

A left valve has a length of 29 mm., lieight 22 mm., hinge-line 21 mm.

This species differs from L, Chemungensis in its proportionally greater length,
narrower umbo, more convex and oblique left valve, and shorter wing.

Formation and locality. In a sandstone and conglomerate of the Chemung
group near Panama, N. Y.

LAMELLIBRANCHIA TA.

leptodp:sma, Hall.

The species arranged under the generic designation of Lgptodesma present a
very remarkable assemblage of forms, Iteginning (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
anterior end rounded, and the entire shell assuming the form of Mvtilus or
MoDioi,A. Sanodiholites. 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, patulaia; e, arcoidea ; f, mytiloidea. These
relations will be more fully explained under the generic description and discus-
sions in the Introduction to this volume.

Section a, spinifera.
Leptodesma Makckllenbk.

ri.ATK XVII. rid. I!

Mart«Uemie>niu.. PiU. N. Y..

,■. l>l.

I'lntcHamlRxpUniitinna: PI. IT,fi|r- '3. Jni

Shell small, sub-rhomboidal ; body 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 thii^l of tlie
hinge. Umbonal region prominent, sloping abruptly on the posterior, not
well defined on the anterior side.

Anterior end limited by a shallow, obscure sulcus ; margin regularly
rounded. Wing naiTOW-triiU!fi;Lihiv, much extended along the hinge, termin-
ating in a mucronate process ; margin deeply and acutely sinuate.

176 PALEONTOLOGY OF NEW YORK.

Test thin, marked 'by fine, closely arranged, concentric strisa, which are
more crowded anteriorly ; these are crossed by extremely fine radii, which
are chiefly confined to the shallow sulcus, anterior to the beak, and are also
<jbscurely marked on the wing.

Ligamental area marked by two strong grooves. Two oblique linear
depressions along the posterior slope indicate the probable existence of lat-
eral teeth. Other characters of the interior, unknown.

The specimen has a length of 11 mm., height 7 mm., hinge-line 12 mm.

Thi.s .species bears some resemblance to several species in the Chemung
group, but it is comparatively narrower and more oblique.

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

Leptodesma Rogersi.

PLATE XXI, KIGS. 1-9.
i^ff*"hj'iH/i Wtyemi, Hall. Pal. N. Y., vol. v, pt. 1. Plates an<l Kxplanations : PI. 21, figp. 1-9. Jan., 1883.

.Shull of small or medium size, sub-rhomboidal ; body ovate, very oblique;
Krngth greater than the height ; anterior and basal margins broadly rounded ;
[jOftt^'rior margin extended and abruptly recurved.

Valves equally convex above. Right valve somewhat depressed below,
^y^mparatively higher than the left.

Hinge-line straight, longer than the length of the shell.

IVrak.s Hub-anterior, obtuse, nearly erect, prominent. Umbonal region
jribF^iiiii, oblique.

'V\uz anterior extremity is scarcely alate or auriculate, consisting of a
romifU^\ extension, straight above and slightly sinuate at the base. Wing
'-y/ni f/anitively large, triangular, joining the body of the valve near the poste-
rior ^-xtremity, defined by the crowding and curving of the concentric strisB ;
ih^r/trt nearly straight for five-sixths of its extent, then acutely recurving;
i'.yAniffi'tiv i>rolonged into a mucronate spine which extends beyond the poste-
rior limit of the valve. In the right valve the wing is less deeply sinuate.

Test thin, marked bv closely arranged eoncentric strife, which at irre^lar
intervals are crowded into fascicles, producing a gentlj undulated surface.
" On the wing the 8tria> are closely arranged, and just below the hinge-line
are turned backward along the spiniforin extension of the wing.

Interior unknown. Ligainental 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.,
hingo-line about 20 mm. The corresponding right valve has a lengtli 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 the
spine, 20 mm. Small specimens are often less than 10 mm. in length and
height.

This species, occurring abundantly in the Hamilton group, closely resembles
Avicula spinigera of Conrau, from the Cliemuug gi-oup. In tlie comparison of
large numbers of specimens, the differences 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 oblique, and
the sinus in the margin of the wing is narrower and deeper than in the riglit
valve of the Hamilton form.

Formation and localities. lu the shales <tf the Hamilton group at Norwich,
Chenango county ; MiddleviUe, Schoharie county, and Leonardsville, Miulison
county, N. Y.

LeI'TODESMA SPINIOEBUM.

l-l

,aTK XXI. FIOB. l(HS; *KU l-LATE LXSXIX. Tlii.

.>,

Aeicttin miiiiiyern. (Iokbad. i
Ptenmllai rpinigrnui (VonRUi
LrptmifJnna ginaigf-naa (Omi

3o,.r. A™i. Nut. Sei.. Philn.. vol. 8. p. 337. ].!. 11

.), S. A. MiLLKH. fat. kiavr. Pnl Fob«., [.- iOi.

«*Dl. Hall. Pul. N. V.. v->l. v, pt. !. Pliites n,

UI-13. Jan.. 1883.

1. fig. 3. IS4a.

IH77.
r..l Kxpkimti.ni

-'1. fiKS-

Shell of medium size, sidi-rlioniboiihd; body ovate, oblique to the hinge at an
angle of about 45°; length one-third greater than the height ; ante-byssal
23

178 PALEONTOLOGY OF NEW YORK.

margin truncate at the extremity, curving below into the sinus; basal
margin rounded, somewhat abruptly recurved posteriorly.

Left valve regularly convex below, gibbous above 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 giblK)us, sub-
tending an acute angle.

Anterior end short, defined by the oblique byssal depression which extends
to more than one-third the length of the valve l)elow the beak ; 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 below the cardinal extension ; extremity produced into a long
spiniform process.

Test thin, marked at irregular intervals by strong concentric lamellaa, with
intermediate fine strise. The lamellae 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 mm., height 20 mm., hinge-
line to base of spine, 12 mm. A smaller specimen has a length of 20 mm.,
height 14 mm., hinge-line, to base of spine, 12 mm.

This species closely resembles L. Rogersi^ but is distinguished by the oblique
and more extended byssal depression, shorter wing, and more rounded basal
margin.

Formation and localities. In shales ol* the Chemung group, on the Chemung
river above Elmira, and along the Blossburg railroad near Painted Post, N. Y.

LAMELLIBRANCHIA TA. 179

Leptodesma longispinum.

PLATE XXI, FIGS. 14. 17-19; AND PLATE LXXXtX, FIGS. 2-4.

AvictUa longufpiTia, Hall. Geolog. Surv. N. Y. : Rep. Fourth Dist., p. 262, fig. 3. 1843.
Pterinea lonffUtphm (Hall), S. A. Millbr. Cat. Anier. Pal. Foss. 1877.

I^eptodemna langutpinuin. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 21, figs. 14, 17-19.

Jan., 1883.

Shell above the medium size, sub-rhomboidai ; body elongate-ovate, very
oblique ; length greater than the height, often nearly double ; margin from
the byssal sinus to beyond the base broadly rounded; posterior margin
extended and abruptly recurved.

Valves, in young specimens, sub-equally convex ; in older specimens the
right valves are somewhat less convex.

Hinge-liqe straight ; length equalling or greater than the length of the valve.

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 ; margin deeply sinuate, the bottom of
the sinus being close beneath the hinge-line ; extremity produced into an
elongate spine.

Test thin, marked by fine, irregular, concentric striae of growth, which
are abruptly recurved on the post-cardinal slope, and extend along the margin
for nearly half the length of the body before recurving into the wing. The
strisB 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 about 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, and 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

ISii PALEONTOLOGY 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, but much deeper than in the right valve of that
species.

The original specimen is illustrated in figure 14 of plate xxi, and figures 17,
IS, 19 are right valves occurring in the same beds.

This form is associated with Avicula spinigera of Conrad, which is a smaller
shell, less oblique, narrower, and with a more angular anterior extremity.

Formation and localities. In the Chemung group, at Painted Post, Steuben
cr>unty, between Coming and Elmira, and at Chemung Narrows, N. Y.

Leptodesma Shumardi, n. sp,

PLATE LXXXIX, FIGS. 5, 6.

JHELL of medium size, sub-rhomboidal ; body narrow, very obliquely-ovate ;
l^ffigth somewhat less than twice the height; margin very broadly curving
from the anterior extremity to the base ; basal margin rounded and abruptly
rc-rrurvcnl at the post-basal extremity.

LoSt valve quite convex; the greatest convexity about one-third the length
of the valve below the apex. Right valve unknown.

IIin;re-line straight; length about equal to the height of the shell.

lif'jik sub-anterior, obtuse, prominent and arching over the hinge-line.
l'njU>nal region gibbous, subtending an acute angle.

Afit^.-rior extremity short, acute, straight above, oblique below. Wing
^ffiall, narrow-triangular, extending to a point below the middle of the length
of the shell ; margin concave ; extremity acute, probably spiniform.

Test thin, marked by lamellose, often fasciculate strisB, which are more
''rowd<.*il on the anterior side and byssal depression, and more regular and
oiftincl on the wing.

lnUinor unknown.

Tlin'^; rjHMMinens of left valves have respectively the following dimensions :
i^^fi'/^ii 12, 10 and '50 mm., height 24, 27 and 24 mm., and hinge-line about
Z'^. Zi and 24 nnn.

This siH-'ries ilifTers from L. longispinum in the wider and somewhat less ohliqiie
tjody, with more regularly rounded posterior extremity ; the sinus in the wing
is less acute and farther below the rai-dina! line, also in the absence of the strong
posterior spine of that species.

Formation and locality. In tlie Chemung group, near Elrnira, N. Y.

LePTOUESMA R0BU8TUM.

vhXTS sxi, naa. la. ib, m; ahu plate lxxxijt, fig, h

Uplodtrim r-Jmntitm. i\\^.\.. Pul. N. V.. vol. v. pi. 1. PWes unfl ExplmmtmnB : PI. 21. fign. iri. 16.20.
Jnii.. IS83,

Shell large, sub-rhomboidal ; bmly 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 tlie valve from the heak. Right
valve moderately convex in the middle, flat below and scarcely gibbous on
the umbo.

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

Beaks nearly anterior, obtuse, sub-erect, very prominent, rising above the
hinge-line. Umbonal region gibbous, prominent, abruptly elevated along tlie
post-umWnai side for more than half the length of the shell, then merged in
the general coinvxity ; ou the anU^-ior side obscurely limited by a bioiid
undefined depression. Umbonal angle acute.

Ant^'Hor extremity scarcely auriculate. Wing small, narrow-triangiihir,
extending about half the length of the valve, defined by the curving of the
strisB ; margin strongly concave, the deepest concavity just below the liiuge ;
cardinal margin thickened and extended into a strong spine. In the right
valve the wing is larger and bromler, and the sinus less deep; the anterior
extremity corres]>onds with that of the left valve.

Test moderately thick, marked by fine concentric striae which become

Iv2 PALEONTOLOGY OF NEW YORK.

more numerous and fasciculate at irregular intervals, producing a slightly
undulated surface, crowded and lamellose on the anterior.

Interior unknown.

A specimen of a left valve has a length, from beak to base, of 43 mm.,
height 29 mm., and hinge-line to the base of the spine 26 mm. A right
valve, referred to this species, has a length of 32 mm., height 27 mm., and
hinge-line, exclusive of the spine, 31 mm.

ThiM .species is larger and more robust than L. longispinum ; the body is wider,
1^* oblique, and less abruptly recurving at the post-basal extremity; the wing
ii! larger and the greatest depth of the sinus not quite so near the cardinal
line ; the striae do not recurve so abruptly forward on the posterior slope ; the
right valve is proportionally higher ; the wing is less deeply sinuate, and the
•piniform extension is shorter.

Compared with L. Mortoniy the body of the shell is less oblique and more
expanded, while the wing is much smaller and the sinus nearer the hinge-line.

Formalion and locality. In the middle portion of the Chemung group at
Painte<l Post, Steuben county, N. Y.

Leptodesma Agassizi, n. sp.

PLATE LXXXIX. FIGS. 17-lU

Shkll of medium size, sub-rhomboidal ; body broadly ovate, oblique to the
hinge-line at an angle of from 50^ to 55° ; length nearly one-third greater than
the height ; anterior margin broadly rounded below the byssal sinus ; ventral
margin regularly curved ; more abruptly curved at the post-basal extremity.

Left valve moderately convex below, more convex above and gibbous on
the umix). Right valve less convex.

Hinge-line straight, about equal to the height of the valve. .

Beaks sub-anterior, scarcely directed forward, prominent, rising a little
alxjve the hinge-line. Umbonal region moderately gibbous, subtending an

acute angle.

Anterior end large, obtuse, tnmcate above and curving below into the

LAMELUBRANCHIATA.

183

f bysi*al winiiK, llmitud hv tin oljliqiie tfepression which reacht-a to near the

► middle of the length of the valve. Wing small, joiuing the body lielow the

middle ; margin oblique below and abruptly concave just beueath the cardinal

I line, recurving and produced into a short spiniform extension. The right

valve is less convex, the wing larger and more extended along the posterior

slope.

Test thin, marked by fine, distant, lamelloae strise with intermediate finer
lines. The stronger strise 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,
I ]-5 mm. Another example has a length of 26 mm., height 19 mm., hinge, to
* base of spine, 15 mm.

This species bears a general resemblance to L. spinigerum, with wliicli it is
[ionietimes fissociated, but the body is more erect and much wider btdow ; the
wing is somewhat wider, the spine shorter, and the strise less strongl}' marked.

Formation and locality. In the middle portion of the Chemung group, ou the
Chemung river, between Elmira and Waverly, N. Y.

Leptohesma protextitm.

PLATE XXI. riG3. M, S3

AniimJa pmU-tta, CnMi
Plurlitm pn^texla {Cnji

I., J.iiir, A.-H,i, N«
.u). S. A. Mtu.n«.

. 8.-i„ PliilH,, vol. viii. [1. 238, j.l. 12. fig. H.
t'n(. Amri'. I'lil. Foea.. p, 303. 1S77.
. N, Y.. vol. V, pt. 1. Plsl.;s iiTuI EiplaDat
•23. Jau., 1RS3.

:PI. 21,^^-8.

Shell small, sub-rhomboidal; body elongate-ovate, very oblique ; length nearly
twice as great iiH the licight ; anterior margin below the byssal sinus, oblique ;
base broadly rounded and abruptly recurved on the post-basal estreniitv.

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 righl valve ia apparently a little smaller than the left.
Hinge-line straight, about equal to the length of the shell.

184 PALEONTOLOGY OF NEW YORK.

Beaks near the anterior end of the valve obtuse, rounded, prominent,
inclined forward. Umbonal region narrow, gibbous for a short space below
the hinge, subtending an acute angle.

Anterior end scarcely auriculate, abruptly rounded in the left valve, pointed
in the right valve, limited by a broad, imdefined depression, which is less
marked in the right valve. Byssal sinus shallow. Wing narrow-triangular,
joining the l)ody near the posterior extremity of the valve, defined by the
direction of the strise; margin deeply concave, the greatest concavity just
beneath the hinge-line ; extremity produced into a sharp spine which extends
nearly as far as the posterior margin of the shell.

Test thin, marked by concentric striae of growth, which are crowded into
fascicles at irregular intervals, giving a somewhat wrinkled or imdulating
surface. On the anterior side the striae are crowded and lamellose, while
they are quite regular and closely arranged over the wing. On the external
shell the striae are elevated into regular, equidistant lamellae. 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 unknown.

The largest specimen observed has a length of 26 mm., height 13 mm.,
hinge-line 20 mm. A similar right valve has a length of 23 mm., height
10 mm., hinge-line 16 mm. The specimens are usually smaller than those
figured.

This species, in form of body and in the concentric striae, resembles
L. longispinum ; but the anterior extremity (especially in the right valve) is
narrower, the wing is extended farther down the body of the valve, and the
spine is less produced.

This shell in its usual condition of preservation (that is, having the spiniform
process of the wing broken off, or the wing partially covered) presents the
characters described by Mr. Conrad, although not illustrated in his figure. A
specimen of this species is labelled in the hand writing of Mr. Conrad, Avtcula
protexta^ and therefore the name is retained.

LAMELLIBRANCHIATA. 185

Formatiun and localities. In the Chemung group at Chemung Narrows, N. Y.,
and Tioga county, Pa.

Leptodesma Becki.

PLATE XXII, FIGS. 3^.

Ltptodesma Becki, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 22, figs. 3-5 (and

figs, t) and 7 in en-or). Jan., 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 gibbous except in the lower part. Right valve less convex.

ffinge-line straight, less than the length of the shell, and greater than
the height.

Beaks at about the anterior third of the hinge-line, obtuse, directed
forward and arching over the hinge. Umbonal region gibbous, scarcely
defined anteriorly, but well-marked posteriorly by the abrupt 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 by concentric striae, which are crowded and somewhat
lamellose in front, and closely and evenly arranged on the wing. The hinge-
line has a single narrow groove.

A left valve has a length of 28 mm., height 17 mm., hinge-line about
22 mm. A detached right valve h^is a length of 29 mm., height 20 mm.,
hinge-line 30 mm.

This species resembles L, robustum in general expression and in the sinus of
the wing, but the body is narrower, more regularly convex, the base less expanded,

186 PALEONTOLOGY OF NEW YORK.

and the basal margin and the stria) along the posterior slope are not so abruptly
recurved.

Formation and localities. In the Chemung group, near Corning, Chemung
county, and Portville, Alleghany county, N. Y.

Leptodesma disparile.

PLATE XXV, FIGS 2-4; AM» PLATE LXXXIX, FIGS. 3, 24.

Tjeptodesma dvtparile* Hall. Pal. N. Y.. vol. v, pt. 1. Platos and KxplanationR : PI. 25, fig*. 2-4.

Jan., 1883.

Shell of small or medium size, sub-rhomboidal ; body ovate, oblique to the hinge
at about 45°; length more than one-thinl greater than the height in the
left valve ; ante-byssal margin oblique, gently curving into the sinus ; basal
and posterior 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-anterior, prominent, rising above the hinge-line, directed slightly
forward. Umbonal region gibbous, subtending an acute angle.

Anterior end large, somewhat produced, limit<Mi by a nearly vertical byssal
depression ; extremity obtusely angular. Wing somewhat large, joining the
body near the posterior extremity ; margin oblique below, concave above the
middle, and produced into an elongate spiniform process. The right valve is
smaller, the wing more extended and less defined, while the anterior end is
large and well defined by the byssal sinus and sulcus.

Test marked by concentric, laniellose ridges with intermediate finer lines
of growth ; the lamella) are sometimes more distinct on the right valve.

Interior unknown.

A left valve has a length of 28 mm., height 20 mm., hinge-line more than
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 umbo, 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. 24-28 (33, 84 ?).

Leptodesma tociaie. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 21, figs. 24-28 (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 below.

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 sub-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 perfect specimens, reaches beyond the
margin of the valve. In the right valve the wing is less distinctly defined,
and the sinus not so deeply concave.

Surface marked by fine concentric strise, which at somewhat regular
intervals are elevated into sharp, conspicuous lamellae, or sometimes into
fascicles of striae 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 PALAEONTOLOGY OF NEW YORK.

A specimen of a left valve has a length of 10 mm., height 7.5 mm., hinge-
line about 10 mm. A similar specimen has a length of 11 mm., height 6.5
mm., and hinge-line about 11 mm. A right valve has a length of 9 mm.,
height 6 mm., hinge-line about 8 mm. Another one has a length of 16 mm.,
height 11 mm., hinge-line about 16 mm.

This is a small and abundant species, often occurring in great numbers on
the surfaces of shaly layers. It is distinguished by its form and the regular
lamellose appearance of the surface.

Formation and localities. In the shales of the Chemung group at Connewango,
Cattaraugus county ; Nanticoke Springs, Broome county, and south of Ithaca,
N. Y.

Leptodesma potens.

PLATE XXI, FIGS. 21, 30; PLATE XXII, FIGS. 11, 12, 19, (20?) 21 ; and PLATE LXXXIX, FIG. 7.

Leptode^in/i potens^ Hall. Pal. N. Y\, vol. v, pt. 1. Plates and Explanations: PI. 21, figs. 21, 30; pi. 22,

figs. 11, 12, 19, 21. Jan., 1883.

Shell large, sub-rhomboidal ; body ovate, oblique, broad below ; length more
than one-third greater than the height ; ante-byssal margin sub-truncate,
erect, oblique below ; basal margin broadly curving ; posterior margin broad,
extended and abruptly recurving at the upper extremity.

Left valve convex, gibbous above ; the greatest convexity at one-third the
height of the shell from the beak. Right valve almost equally convex, more
abruptly gibbous on the umbo, and comparatively shorter and wider.

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

Beak sub-anterior, obtuse, erect, prominent, arching over the hinge.
Umbonal region gibbous, very prominent, limited 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 ; posteriorly limited by the
abrupt post-cardinal slope. Umbonal angle acute.

Anterior extremity extended and angular. Wing large, triangular, joining
the body near the posterior extremity, distinctly limited ;• margin broadly

189

siiiuato; extremitj produced into ii strong spine (the extent nf which is
unknown).

Surface marked by strong coneentrie lines of growth, whicli an- crowded
into xnialt fascicles at irregular intervals on the body of the shell, Jind become
hunelloKe expansions nn the anterior. On the wing they appear iis sharp
e<iuidiKtiint hiinella>. Casts of the Int^-rior show the concentric slriiB in a
mibdued condition.

Interior unknown.

The largest left vatve observed has a lengtli, mesisured from beak to base,
of 62 mm., height 46 ram., 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 tliis species has a length of 36
mm., height 28 mm., and hinge-Line, to base of spine, 35 mm.

This species more nearly resembles L. robustum than any of the forms here
described ; but it is larger, the wing proportionally larger and distinctly limited,
and the sinus of the wing more central. The right valve is also more convex
and the wing more deeply sinuate. It occurs in the upper meiubers of the
Chemung group, associated with Spirifera Verueuili, while L. robustum is found
only in the middle of the series.

It is a larger and more robust shell than L. Morloni. and the right valves
are very milike.

Formation and localities. In the Upper Chemung group at Olean, Portville,
Casaadaga lake, and In loo,"!e specimens cf)llected near Panama, N. Y.

Leptodesma potens, var, jdvens.

I'LATE XXU. FIU 10.

r^ixUtna jyteiiM, mr junrim. Hall. PiJ. N. Y.. vuI. v, |iI. I. Pktes iiiirl p:x|ilitQiilli>iis: I'l. 22, tig. Ifi.

J»n,. IBB3.

Shell small, rhoinboidal; body ovate, oblique; the greatest length mure than
once and a lialf the height; anterior margin oblique, very broadly curving
below; post-basal extremity rounded and abruptly recurved.

Left valve convex below, very giljbous and ventricose in the middle and
above. Right valve unknown.

190 PALEONTOLOGY OF NEW YORK.

Hinge-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-line and inclined slightly forward. Umbonal region
ventricose, obscurely limited anteriorly by an undefined depression, and on
the posterior side by the abrupt and almost vertical post-umbonal slope.
Umbonal angle acute.

Anterior end short, triangular ; extremity acute. Wing broad-triangular,
joining the body of the shell near the posterior end; margin regularly
concave ; extremity acute.

Test thin, marked by extremely fine, regular concentric strisB, which are
crowded into fascicles on the anterior end.

Interior unknown.

The specimen described has a greatest length of 25 mm., height 15 mm.,
hinge-line 22 mm.

This shell resembles L. potens^ but it is apparently more extended and acute
in front, sub-truncate on the posterior end ; the wing joins the body near
the posterior extremity, and its margin is less deeply sinuate than L. potens.
T\iiMi variations appear in comparison with the older individuals of that species
and cannot be taken as positive evidence of specific difference, while at the
fsarne time their common characters may be insufficient to unite them.

FffrmatUm and locality. In the Chemung group at East Randolph, Cattaraugus
^>^ifttv, N. Y.

Leptodesma Mortoni.

PLATE XXI, FIGS. Jtt), 31, 32; AND PLATE LXXXIX, FIGS. 9-11.

§^l4/A^jrtita MorUmi, Hall. Pal. N. Y., vol. v, pt. 1. Platen and Explanations: PI. 21, fig8. 29, 31, 82

(pi. 22, %. 20 in error). Jan.. 1883.

hntix alxive the medium size, sub-rhomboidal ; body elongate sub-ovate, very
oblique ; length more than one-half greater than the height; ventral margin
hnr4/l\y curving to the base ; the posterior margin extended and abruptly

LAMELLIBRANCHIATA.

191

Left valve convex, gibbous above. Right valve depressed-convex below,
and abruptly gibbous at the umbo.

Hinge-line straight; length less tlian the length of the «hell.

Beaks sub-anterior, obtuse, erect, prominent, arching over the ciLrdinal
line. Umbonal region gibhoua and gradually sloping down to tlic general
convexity, abruptly limited on the posterior side, subtending an acute iUigle.

Anterior end extended, acute and nasute. Wing large, triangular, slightly
convex, joining the body of the shell more than two-thirds of tlie length
below tlie beak; margin symmetrically concave; extremity produced and
very acute. In the right valve the anterior eud is broad and flat ; tlie wing
in large, with no defined limit between it and the body of the valve.

Surface marked by elevated concentric strias which, at irregular intervale
are fasciculate, producing undulationw on the surface. This character is often
marked on the front of the shell where the fascicles are compoeed 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., hiuge-line about 38 ram. Another example has a
length of 45 mm., height 25 mm., hinge-line 32 mm. A right valve measures
43 mm. m extreme length, height 30 mm., hinge-line about 34 mm.

This species bears some resemblance to L. robustum, but the body i.s more
oblique and not so broad below ; the anterior extremity is acute ; the wing
larger, more extended along the valve and very symmetrically concave oq the
margin. The form of the shell is very similar to L. longispinum, but (Hffers
by its larger wing, the broiuler 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, AUegliauy county, N. Y.

192 PALAEONTOLOGY OF NEW YORK.

Leptodesma Billingsi, n. sp.

PLATE LXXXIX. FKiS li-l.V

Shell large, sul)-rh()nil)oi(lal ; l)0(ly elongate-ovate, or sub-cylindrical, very
oblique; length about twice the height; ante-byssal margin rounded,
l)ecoming straight or slightly concave at the sinus ; ventral margin broadly
curving; posterior margin extended, acutely recurved at the post-basjd
extremity.

Left valve gibbous on the umbo, convex below. Right valve unknown.

Hinge-line straight ; length, including the spine, nearly equal to the length
of the valve.

Beak sub-ant<?rior, ol>tuse, slightly oblique, prominent. Umbonal region
somewhat gibl)ous, subtending an juuite angle.

Anterior end limited by a shallow l)yssal depression, acute and nasuto 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 fine concentric striiB which are abruptly archeil on
the posterior slope, regular upon the wing, and crowded into fine irregular
fascicles which are conspicuous on the anterior. Some specimens show sharp,
elevaUnl, lamellose striie at equal distances on the surface of the body. The
surface characters varv with the different states of exfoliation and maceration.

The largest specimen observed has a greatest length, from beak to base,
of 57 mm., height 3G mm., hinge-line, to base of spine, 35 mm. A small
example of the left valve has a length of 34 mm., height 18 mm., and hinge-
line about 35 mm.

This species is more elongate and obli(iue than L. longispinum^ the wing extends
farther down along the posterior slope, and the anterior extremity is fuller and
more iu*ute.

Formation and localities. In the Chemung group at Panama, N. Y. Other
specimens from near Klmira, N. Y., and Mansfield, Tioga county, Pa., are
referred to this species with reservation.

LAMELLIBRANCHIATA. 193

Leptodesma Matheri.

PLATE XXII, FIGS. 8, 9, 10; and PLATE LXXXIX, FKi. 25.

Ijeptodesina MalherU Hall. Piil. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 22, figs. 8-10.

Jan., 1883.

Shell of medium size, rhomboidal ; body ovate, oblique at an angle of 45° with
the hinge-line ; length about one-half greater 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 above. Right valve
shorter and less convex.

Hinge-line straight ; length much less than the length of the valve, but
nearly equal to the height.

Beaks at about the anterior third of the hinge, obtuse, directed slightly
forward, not very prominent. Umbonal region moderately gibbous, sub-
tending an acute angle.

Anterior end produced, Hattened, acute at the extremity. Wing 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 fasciculate on the
body of the shell, producing an undulated appearance. The striae are
sub-lamellose on the anterior and regular over the wing.

Interior unknown.

A left valve has a length of 35 mm., height 23 mm., and hinge-line about
28 mm. A similar right valve has a length of 29 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. polenSj 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.

Leptodesma Stephani, n. sp.

PLATE LXXXIX. PIGS. a^22.

Shell above 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
aliove, 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 gibbous at the umbo.

Hinge-line straight, equal to about 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
lK)dy at less than one-fourth the length of the valve from the posterior
extremity; margin very oblique below, deeply concave above; the greatest
depth of the conravity is above the middle, whence the margin is abruptly
n-curved and produced into a spiniform extension.

Tost of moderate thickiwss, marked by nearly equidistant lamellose
(M>nc4;ntri(! striie, with intermediate finer striaB of growth. The lamellose
HtriiJU an^ sulxhied upon the wing, and very strong and irregular on the
anUtrior side.

[nU*rior unknown.

A large HpecMinen of this species hiv^ a length of 43 mm., height 25 mm.,
and hing(?-linc^ about *{:{ mm. A somewhat smaller example has a length
of '57 nun., bright 25 mm., and hinge-line 30 mm. A right valve measures
:{:{ mm. in Imgtli, 21 mm. in height, and hinge-line 28 mm.

TIiIm H|ic<'irM n'H(Mnbh»s L, Matheri with which it is associated, but differs in
iU finuiU'r obli(|iiity, nion* elonjrate outline, more extended and flatter wing,

LAMELLIBRANCHIA TA. 195

which is more deeply concave on the margin and with the extremity more
produced; the anterior extremity is also larger and apparently not produced.
The right valves of the two epecies are very unlike.

Formation and localities. In the Upper Chonunif;: group at Bradford, Pa., and
doubtfully occurring near Elmira, N. Y.

Leptodesma lepidum.

I'l.ATK XXI, Flil. 10; iMi PLATE LKXXIX, RU 10.

Uplvdemaa Uplduia. Hiu.. Pal. N, V., vol. v, pi. 1. PUtps uml ExpUoftlions: Pi. 21. fig. 40, Jan..l88B.

Shell of medium size, narrow, sub-rhombuidal ; body narrowly ovate, somewhat
straight on the po.-<terior slope, oblique 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 broafUy rounrled to the posterior
extremity, which is abruptly recurved.

Left valve regularly convex below, gibbous above. Right viilve very
depressed-convex, nearly Hat below, moderately convex on the umbo,
considerably smaller than the left.

Hinge-line straight; length mure tlian two-tliirds 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 depres-sion. Wing narrow-triangular, joiuing the body at about one-
fourth the length from the posterior extremity; margin deeply concave,
L^niptly recurved along the cardinal line, and extended into a spiniform
'process. 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 striae are more diatant and more even in their character.

196 PALAEONTOLOGY OF NEW YORK.

Interior unknown.

A left valve of medium size luus a length of 41 mm., height 22 mm., length
of cardinal line about 35 mm.

This species differs from L. Hector in its greater obliquity, broader lx)dy
below, more produced and abruptl}' 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 the central portion of the Chemung group at
Philipsburg, Alleghany county, N. Y., and below the conglomerate (same
position) in Sullivan township, Tioga county. Pa.

Leptodesma curvatum.

PLATE XXV, FIG. 6.
Leptodesma curvatum. Hall. Pal. N. Y., vol. v, j>t. 1. Plut(\s anci Kxplaiintions : PI 2.*), tip. .'). Jan., 1883.

Shell above the medium size, rhomboidal; body ovate, sub-arcuate above,
oblique at an angle of nearly 30^ with the hinge-line ; length and heiglit as 7
to 4 ; ante-byssal margin oblique above, curving into a long, shallow sinus ;
l)asal and posterior margins forming a brojid, continuous curve, and abruptly
recurving at the post-basal extremity.

Left valve regularly convex below, gibbous above the middle. Right
valve unknown.

Hinge-line straight; length about equal to the length of the valve, but not
fully seen, as the spiniform termination is imperfect.

Beak sub-anterior, prominent, directerl forward. Umbonal region gibbous,
subtending an acute angle.

Anterior end large, abruptly acute at the extremity, limited by a distinct,
nearly vertical byssal depression. Wing narrow-triangular, joining the body
at the posterior extremity; nuirgin very oblique l)elow, concave above,
al)ruptly recurved just below the (cardinal line and extended into a spiniform
process. In a cast of the left valve the wing is distinctly separated from
the body by a marked furrow.

LAMEUJBRANCHIATA.

197

Test moiltriitely tliit^k, marketi by elevated lanipllose stria', with finer
iDtermt'diate lines.

Interior unknown.

The wpt'cimen described has a length of 42 mm., height 24 mm., hinge-
line, to base of spini', 'M'l mm. The spine is probably extended from "5 to
10 mm. beyond.

This tipecies resembles ]j. kpidum, l)iit 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, Cattaraugus
county, N. Y.

Section b, umbonata.

LilPTODESMA MedoN, u. «p.

SHELL of medium siiw.', aub-rhomboidal ; body broad-ovate, oblique at an angle
of alxjut 60° with the hinge-line ; length nearly one-third greater than the
height ; ante-hyssal margin curving slightly outward, concave at the sinus ;
basal and posterior margin.** 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 left \'alve.

Hinge-lino straight; length a little greater than the height of the shell.

Beakx at about the anterior third of the hinge, acute, prominent, arching
over the hinge-line. Umhonal region gibbous, descending almost vertically
on the posterior, and sloping abruptly on the anterior side. Umbonal angle
acute.

Anterior end shoit, 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 PALAEONTOLOGY OF NEW YORK.

Test thin, marked by concentric striae, which, on the body 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., height 22, 25 and 23 mm., and
hinge-line 25, 27 and 25 mm.

In this species the body of the shell resembles L. robustum and L. potens^ but
is less oblique to the hinge-line, the wing, less defined, and its posterior
extremity not produced into a spine.

Formation and locality. In the upper part of the Chemung group, Lawrence-
ville, Tioga county, Pa.

Leptodesma umbonatum.

PLATE XXII, FIG. 18 ; and PLATE XC, FIG. 9.

Leptodestna umbonatum. Hall. Pal. N. Y., vol. v, pt. 1. Platen and Explanations : PI. 22, fig*. 13.

Jan., 1883.

Shell of medium size, rhomboidal ; body oblique, narrowly ovate ; greatest length
one-lialf 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 about the anterior third of the cardinal line, directed slightly
forward, prominent and arching over the hinge. Umbonal region narrow
and ventricose, defined anteriorly by a broad, shallow depression, which is
nearly vertical to the hinge-line, and posteriorly by the abrupt depression of
the body.

Anterior end acute, triangular. Wing rather large, triangular, convex,
joining the body of the shell near the posterior extremity ; margin broadly
concave ; extremity produced, acute.

LAMELLIBRANCHIATA. 199

Test thin, marked by fine concentric linea of growth wliich are irrcgnl.irly
crowded into small tiisdicles, producing a alightly undulated appearance.
The strise are strong and regular over the wing.

Interior unknown.

The left valve described has a length of 41 mm,, height 27 mm., hingc-linc
about 38 mm.

This species bears some general resemblance to L, potenx and L. robuslutn, Imt
the body 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. ttmbonatum
var. depressum. PI. xxii, lig. 14., but difters 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 upper part of the
Chemung group, Twenty-mjie creek, Chautauqua comity, N. Y.

LEPTODESMA UMBOfJATUM, Var. DEPfiESSUM.
PLATE XXU, riG. U ; AKD rl.ATE XC, FIG. m,

Lfploiliitina umhi'iialtiiH, mr. i^-jtri^iuin, HjUJ.. Pal, N. Y., vol. v, jit. I. Platiss and EifilHiiiilitiun ; !M. •I'l.
dg, 14. Jan., 1883.

Shell of medium size, rhomboidal ; body very oblique-ovate ; length once and
a half greater than the height ; ante-byasal margin, below the acute extrem-
ity, regularly curving into the ventral margin ; posterior extremity produced,
with the margin gently recurving into the wing.

Left valve convex below, gibbous above. Right valve smaller, a little less
convex, abruptly gibtx)us on the umbo.

Hmge-line straight, somewhat less than the greatest length of the shell.

Beaks sub-anterior, obtuse, ilirected slightly forward, very prominent,
arching over tiie hinge-line.

Anterior end short, large, limited by a broad, undefined depression ;
extremity produced, acute. Wing large, triangular, not distinctly defined.

200 PAL2E0NT0L0GY OF NEW YORK.

joining the body near the posterior end ; extremity produced, acute, and
probably extended into a short spine.

Test marked by fine strise of growth which are irregularly fasciculate,
producing a slight undulation of the surface. The striae are lamellose on
the anterior side and regular on the wing.

Interior unknown.

The specimen described has a greatest length of al)out 40 mm., height 25
mm., and hinge-line 35 mm.

This form differs from L. umbonatvm in the lesser convexity and greater width
of the lower part of the body ; less abrupt depression on the anterior side from
the umbo ; the posterior slope less elevated and defined below the middle, and
a much larger ante-byssal portion of the shell.

Formattm and locality. In the upper part of the Chemung group, Napoli
Centre, Cattaraugus county, N. Y.

Leptodesma naviforme.

FLATK XXII, FIG. 15 ; and PLATE XXIII, FIG. 1.

Leptodesma uavifontif. Hall. Pal. N. Y., vol. v, pt. 1. PlatoH and Explanations: PI. 22, fig. 15;

pi. 23, ti^r. 1. Jan., 1883.

Shell below the medium size, rhomboidal ; body very oblique, short-ovate ;
length more than one-third greater than the height; anterior extremity
subtruncate ; margin curving to the broadly rounded base ; posterior margin
slightly produced, gently curving forward, nearly vertical.

Left valve convex below, very gibbous above the middle. Right valve
depressed-convex below, gibbous above.

Hinge-line straight, more than one-third greater than the height of the
shell.

Beaks obtuse, situated at the anterior fourth of the hinge-line, prominent,
directed slightly forward. Umbonal region gibbous, sloping abruptly into
the wing.

201

Autcrior end ribort, acute. Wing large, not distinctly limited, extending
ftlmost to the posterior extremity ; margin scarcely concave below ;
extremity produced, acnte.

ITest marked by fine concentric utrise, which are crowded into fascicles at
nearly equal intervals, rounded upon the upper part of the body, mid Huli-angular
on the lower part. The strise arc crowded and lamellofte 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 by strong interrupted radii
which appear to belong to the intimate structure 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 iisaociation
Inis a length, from beak to base, of 2f) mm., height 18 mm., and hinge-line
aliout 25 mm.
IlK
Shi

This species is quite unlike any here described.

Formation and locality. In the lower beds of the Cheuumg group at the
Inclined Plane, near Ithaca, N. Y.

Leptodesma Cadmus, d. sp.

I'LATE XC, FIGS. II, 7.

Shell of medium size, rhomboidal ; body oblique, narrowly ovate or sub-
cylindrical ; length nearly one-third greater than the height; ante-byssa!
margin somewhat vertically truncate, sloping below into the broadly curving
base ; posterior margin abruptly curved.

Valves convex, gibbous al)ove ; the right valve smaller than the left.
Riuge-Iine straight, nearly equal to the height of the shell.
Beaka 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 PALEONTOLOGY OF NEW YORK.

Anterior end small, terminating in a narrow nasute extension. Wing
comparatively large, triangular, joining the body near the posterior end ;
surface concave; margin gently sinuate; extremity produced into a short
spiniform extension.

Test thin, marked by fine concentric striaB, 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 body of the right
valve the striae form sharp, lamellose elevations at somewhat equal intervals.

The hinge is marked by 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. vmbonalum var. depressum^ but differs in its smaller
and narrower anterior end and more cylindrical body, and wing without a broad
sinus in the miirgin.

Formation and localities. In the upper beds of the Chemung group, Steuben
county, N. Y., and Tioga and Bradford counties, Pa.

Leptodesma Creon, n. sp.

PLATE XC, FIGS. 11-13.

Shell below medium size, sub-rhoniboidal ; body ovate, oblique to the hinge-
line at an angle of about 5-3^ ; length nearly one-third greater than the
height; ante-byssal margin slightly oblique or rounded, distinctly sinuate
]>elow, then gently curving to the broml ])ase ; posterior margin broad, join-
ing the wing without interruption.

Left valve convex below, gib])ous above. Right valve less gibbous than
the left and more expanded.

Hinge-line straight ; length a little greater than 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, IimitetJ by tlit abrupt slope of the posterior side. UmboiiiU iingle
acute.

Anterior end large, short, rounded, curving into the byaaal sinus, defined
by a marked byssal depression; extremity acute. Byssal sinus marked by a
bn>ad, t^hallow 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 uito 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 2.^ mm.
A smaller specimen has a length of 29 ram., height 20 mm., hinge-line
22 mm.

This species resembles in general expression L. unibonatum 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, tlie extremity less
produced, and the umbonal region not so abruptly gibbous.

Formalion and locality. In thi- upper part of the Chemung group, Lawrence-
villc, Tioga county. Pa,

Leptodksma Demos, u.

I'l.ATlS XV. FIGS. W, Ifl.

SiiKLi, of medium size, rliomboidal ; body very oblique, narrowly ovate ;
extreme length more than one-third greater than the height; ante-hyssal
margin oblique, rounded below, concave at the sinus; basal margin broadly
rounded ; posterior mai'gin 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.

Be&ks situated at about the anterior third of the hinge, prominent,

204 PALAEONTOLOGY OF NEW YORK.

directed forwaixi and rising a little above the cardinal line. Umbonal
region gibbous, defined on the anterior by the byssal depression, and on
the posterior by the slope of the side.

Anterior end large, limited by an oblique byssaJ depression, angular at the
extremity and rounded below. Byssal sinus extending to a point more than
one-third the height of the valve below the ])eak. Wing narrow-triangular,
not distinctly limited; margin oblique, slightly convex, recurving just below
the hinge-line ; extremity angular.

Test marked by fine, irregular strise, 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 imd more elongate than in
L. Oreoriy and the wing smaller and less distinctly defined. It resembles
L. LichaSy but differs in its more gibbous umbo, stronger byssal depression, less
oblique margin of wing, with less acute termination and proportionally shorter
body.

Formation and locality. In sandstones of the Chemung group at Lawrence-
ville, Tioga county, Pa.

Leptodesma Loxias, n. sp.

PLATE XC, FIG. 14.

Shell of medium size, rhomboidal ; body ovate, niirrow above, oblique to the
hinge-line at an angle of about 40^ ; height 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 th«

205

anterior third of thf liiuge. Umbunal region uarrow and gibbous, subtend-
ing an acute angle.

Anterior end limited by ft broa*l, nearly vertical byssal depression which
extends one-half the height of the valve ; margin convex ; extremity
acuminata?. Wing triangular, not distinctly limited, joining the body near
the posterior extremity ; margin oblique, nearly straight, eoucave just
bt-'neath tliL- hinge-lino ; extremity mucronate,

Tei^t thin, marked by fine concentric strife, whieli are regular over the
body anrl wing and strongly lamellose and fasciculate on tlie anterior end.

Interior unknown.

A small left valve ha.s a greatest lungth of 28 mm., height 17 mm., hinge-
line 21 mm.

This species ia distinguished from L. Creon and L. Demus by ita narrower
anterior end and more rounded ventral margin.

Formation and localiti/. In the Chemung group, Lawrenceville, Tioga county,
Pa.

Leptobesma Mentor, n. ep.
ruTK xu fu, a, AKi. i-r.ATK xxui, riu u?

Shell of medium size, sub-rhomboidal ; body elongate-ovate, narrow at the
anterior end, oblique, making an angle of about 40° with the hinge-line;
length one-third greater than the height ; ante-byasal margin oblique, curving
into the gently depreused sinus ; basal margin l)ri)adly curving into the
rounded posterior extremity.

Left valve nioderat*jly convex in the lower part, becoming convex in the
middle and gibbous above. Right valve imknown.

Hinge-line straight; length about equal to the height of the valve.

Beak sub-anterior, directed forward, acute, but little elevated above the
hinge-line. Umbonal region abruptly, or sub-angularly gibbous, narrow,
subtffliding an acute angle.

Anterior end small, narrow, limited by an oblique byssai depression which
reaches about half way down the body of the shell ; extremity pointed.

206 PALAEONTOLOGY OF NEW YORK.

Wing joining the body near the post-extremity of the shell, defined by a
shallow groove ; margin oWique, straight, apparently slightly concave just
below the cardinal line.

Test thin, leaving upon the cast the marks of the striae of growth which
have been somewhat fascicled upon the body, giving it an obscurely undulated
appearance.

Interior unknown.

A specimen of this species hais a length of 35 mm., height 24 mm., and
hinge-line nearly 24 mm.

This species resembles L. Orodes^ but differs in its greater obliquity ; the
body is more attenuate toward the anterior, and the wing is distinctly limited.

This one, and several other species, have shown the 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.

PLATE XXV. PIGS. 6, 9, (10?); asi> PLATE XC. FIG. 8.

Leptodesma Orodes^ Hall. Pal. N. Y.. vol. v, pt. 1. Plates and Explanations: PI. 25, figs. 6, 9(10?).

Jan., 1S83.

Shell of medium size, sub-rhomboidal ; body ovate, oblique to the hinge-line
at an angle of about 55^ ; length one-fifth greater than the height ; ante-
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 becomes gibbous. Right valve
unknown.

Hinge-line straight, a little less than the height of the valve.

Beak sub-anterior, directed forward, moderately prominent, scarcely rising
above the cardinal line. Umbonal region abruptly gibbous, subtending an
angle of about 30^.

LAMELLIB RANCH! ATA. 207

Anterior end short in the direction of the hinge-liuo, 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 cai-dinal line.

Test thin ; casts of the inferior oliscurely marked by fine strite of growth
which are mometiraes 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 hits a length of 25 mm., height 20
ram., and hinge-Hue IB 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 hits the same general aspect, but is proportionally
wider l)elow 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, rostrala.

Leptodesma extenuatdm.

i'latk xsu, klu 28 , .isi- plate xc, figs. 17, 18

Ltphtiirsma rjUiiiuitam. 11*1.1- Pnl. N. V., v.il. v, pt. l. PUtes and ExjilaiiationB : PI, 33, fig. 33.
Jim., 1R83.

SnELL of medium size, elongate, semi-ovate ; body narrowly oyatc and oblique
to the hinge-line at an angle of aliout 30°; length nearly twice tlie height;
ante-byssal margin very oblique, scarcely depressed at the sinus, thence nearly
straight to the broadly curved base ; posterior margin abruptly recurved.

208 PALEONTOLOGY OF NEW YORK.

Left valve moderately convex below, gibbous on the umbo. Right valve
flat below, depressed-convex in the middle, and more convex above, propor-
tionally wider than the left, and distinguished by its depressed-convex form.

Hinge-line straight ; length greater than the length of the valve.

Beak of left valve sub-anterior, Jicute, directed forward, rising slightly
above the hinge-line. Beak of right valve depresse<l, not rising above the
cardinal line. Umbonal region of left valve moderately gibbous, subtending
a very acute angle.

Anterior end greatly extended, acute, rostrate, limited by a shallow byssal
depression. Wing narrow-triangular, joining the body at the posterior
extremity, defined by the recurving of the striae; margin abruptly and
symmetrically concave; extremity profUiced beyond the posterior limit of
the shell.

Test thin, marked by fine, sharp, closely arranged, concentric striae, which
are sometimes fasciculate upon the body and anterior side, and very distinct
upon the wing. Partial casts of the interior of the left valve give indications
of fine radii which appear to belong to the intimate structure of the shell.

Characters of the interior unknown.

A left valve has a length of 82 nmi., height 16 mm., and hinge-line
37 mm. A right valve has a length of 34 mm., height 19 mm., and hinge-
line 40 mm.

This species is distinguished by the great length of the hinge-line, its narrow
outline, and anterior extension. It approaches Pteronites in character, but
differs in having a distinct wing, more depressed form, and a recurvation of
the striae along the post-umbonal slope.

Formation and localities. In the Chemung group, Philipsburg, Alleghany
county, N. Y., and Kelly's creek, Tioga county, Pa.

LAMELLIBRANCHIATA.

Leptodesma Hector, d.

PLATE XC, (

Shell of medium size, siib-rhomboidal ; body narrowly elongate-ovate, oblique
at an angle of about 'M\° with the cardinal line ; length a little more than
once and a half the height ; ante-byssjil margin oblique, curving into -a broad,
shallow sinus ; ventral margin broadly curved ; posterior margin iibruptly
recurved.

Left valve moderately convex below, narrowly gib)ioii8 above. Right
■ vaJve depressed below, gently convex above.

Hinge-line straight; length equal to about four-liftlis of the lengtti of the
valve.

Beaks sub-anterior, directed forward, acute, slightly elevaterl above the
binge. Umbonal angle very acute.

Anterior end narrow, small, produced into an acute extension, defined by
a Bhallow byesal depression. Wing large, joining the body at three-fourths
or more of its length from the beak : margin very oblique below, deeply
sinuate just beneath the cardinal line, turning abruptly backward and
terminating in a spLniform extension. The wing of the right valve is
Hcareel^' defined, and the sliell has a somewhat broadly spatulate aspect.

Test thin, marked by fine, close, concentric stria}, and, as usually seen,
the surface shows nearly equally distant lamellose striae 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 obscure Indications
of the striation of the shell.

Muscular impression in the right valve large, sub-circular, placed Ih'Iow
the middle of the length of the posterior slope.

A left valve, of tlie usual size, has a length of 35 mm., height 20 mm,,
hinge-line 27 mm. A email specimen has a length of 20 mm., height 12
mm., and hinge-line lf> mm. Youug shells of this species are more gibbous
than the older examples.
27

210 PALAEONTOLOGY OF NEW YORK.

This species resembles, in its general form, L. extmuaium^ but the body is
narrower at the beak, the wing less extended, 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.

Leptodesma Clitus, n. sp.

PLATE \< . FIG. '1\.

Shell of medium size, narrowly sub-rhoml)oidal ; body elongate-ovate, oblique
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. Umbonal
region gibbous, subtending an acute angle.

Anterior end narrow, prolonged into a rostrate extension, defined by a
strong byssal depression. Wing narrow- triangular, joining the body near
the posterior end, defined only by the abrupt recurving of the striaa ; margin
deeply and abruptly concave, the deepest concavity about the middle ; the
extremity is an acute extension of the cardinal line.

Test thin, marked by fine concentric striae, which are fasciculate upon the
body, leaving the cast marked by gentle undulations, which are lamellose and
elevated on the anterior side and rostral extension, and elevated on the wing.

Interior unknown.

A left valve has a length of 37 mm., height 20 mm., hinge-line 32 mm.

This species differs from L. extenuatum in its broader botly, shorter hinge-line,
and narrower wing ; the stria3 bend more abruptly forward along the post-
cardinal slope, and the wing margin is more deeply concave.

Formation and localities. In shales of the Chenmng group at Kelly's creek
and Mansfield, Tioga comity, Pa.

LePTODESMA TaCNCATUM, Q. gp.

PLATE XC, riGS

^nELL above the medmm size, eub-rhomboidal ; bmly ovutt'-elongate, oliliijut' to
tbf binge-lint! at un angle of (iboui 36° ; length two-thii'drt greater than the
height; nntc-hysyul margin oblique and often abruptly truncate, curving into
the sinus ; broadly rounded nlong the ventral margin, and more rapidly curv-
ing on the post-basal margin.

Left valve gently convex below, bt-coming more convex above, and some-
what gibbous on the uml)o. Kigbt valve lest* convex, flat 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 somewhat promi-
nent; in the right valve not elevated above the hinge-line. Umhonal angle
acute.

Anterior end obtuse, tnmcatc, abruptly angular- at the cardinal margin,
limited by a slightly oblique byssal depression. Wing large, triangular,
joining the bo<iy 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 tlie right valve the wing is le.«s defined, and the
anterior end is more strongly truncate.

Test tbin, marked by sharp, elevated, distant, concentric stria", with
intermediate finer lines of growth. The stronger stri^ are regular upon the
wing and posterior part of the .shell, fasciculate on the anterior side, and
stronger and lanieltosc on the anterior extremity.

Interior unknown.

A left valve has a length of 38 mm., height 22 mm., and hinge-line 37 mm.

Thi» species may he known by its truncate anterior end. The form of the
body is very similar to L. exlenyatum, but it is somewhat more convex and a
little wider ; the wing margin is less coucave 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.

212 PALEONTOLOGY OF NEW YORK.

Lbptopbsha Cobtdon, n. sp.

PLATE XC, Fia. U.

Shell above the medium size, -sub-rhomboidal ; body narrowing very rapidly
toward the beak, oblique to the hinge-line 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 thinly 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 which produces a long, gentle curvature in the
margin of the valve. Wing narrow, joining the body at nearly the posterior —

extremity ; margin abruptly recurved below and somewhat deeply concave a —

little below the cardinal line ; extremity forming a spiniform extension.

Test thin, marked by fine concentric striae, which are fasciculate on (hi ^^

body at unequal distances, and sharply elevated and more distinct on Ihi m _ -^

wing.

Interior unknown.

A left valve of medium size has a length of 42 mm., he^ht 25 mm. — -^r"^--
hinge-line about 40 mm.

Compared with L. CHtus, the body of the shell is more elongate-ovate or^L^^ *^'
sub-spatulate, narrowing more rapidly toward the post^extremity ; the wing i -£" "

wider and the sinuosity less deep, its greatest depth being near the cardina^^ — ^•- *•
line.

Formation and hcalihj. In the Chemung group, Kelly's creek, Tioga conn t^^^ — ^n-jyt
Pa.

LAMELLIBRANCHIATA. 213

Leptodesma Jason, n. sp.

PLATE XCI, FIGS. 4-«.

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 byssal sinus ; thence nearly
straight to within one-fourth the length of the valve from the posterior
extremity, which is regularly and broadly rounded.

Left valve regularly convex below, narrow and gibbous above. Right
valve depressed-convex below, more convex above, and moderately 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 giblxous, 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, terminating in a short spiniform extension. In the right valve the
wing is proportionally larger and less defined.

Test thick, marked upon the body and wing with sharp, elevated,
lamelliform striae and intermediate finer striae ; on the anterior the striae are
fasciculate.

Interior unknown.

A large left valve has a length of 40 mm., height 26 mm., hinge-line 32
mm. A right valve has a length 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 striae are

214 PALEONTOLOGY OF NEW lu^.^.

much stronger. In all these characters it also differs more extremely from
L. extermatum.

Formation and locality. In compact sandstone of the Upper Chemung group,
alternating with some red beds, on Seely creek, Tioga county, Pa.

Leptodesma Pelops, n. sp.

PLATE XC. FICi> 28. ».

Shell larger than the medium size, sub-rhomboidal ; 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 byssal
sinus ; posterior margin very broadly curving.

Left valve depressed-convex below, gradually becoming more convex above
the middle, and somewhat gibbous on the umbo. Right valve unknown.

Hinge-line straight, nearly equal 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
produced and acutely angular.

Test marked by distant, sub-equal, lamellose elevated striaa, with finer
intermediate strise. The stronger striae 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, i
* slender lateral tooth.

A large left valve has a length of 44 mm., height 28 mm., and hinge-lir
42 mm.

This form is more oblique, and the wing is longer and narrower than
L. Orodes.

LAMELLIBRANCHIA TA. 215

Formation and locality. In the Upper Chemung group, Mansfield, Tioga
county. Pa.

Leptodesma Orcus, n. sp.

I»LATK XC. FIG 23

Shell of medium size, sub-rhomboidal ; 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, slightly impressed
at the sinus, nearly straight along the base and regularly rounded posteriorly.

Left valve symmetrically and gently convex below, 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 byssal depression ; extremity
acute. * Wing of medium size, joining the body about three-fourths its length
from the beak ; margin abruptly curving forw^ard 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 part 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 proportions 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 striae less sharply elevated, curving more forward along the
posterior slope, and more abruptly recurved under the cardinal line.

Formation and locality. In the Chemung group at Kelly's creek, Tioga county,
Pa.

216 PALEONTOLOGY OF NEW YORK.

Leptodesma Lysander.

PLATE XXII, FIG. thJ; AM) PLATE XC, FIG. W.
L^'ptodutma Lysander, Hall. Pal. N. V., vol. v, pt. 1. Plat«»s and KxplaTiatioiiH : PI. 22, fig*. 22. Jan., 1883.

Shell of medium size, sub-rhomboidal ; boiiy ovate, abruptly narrowing
toward the front, o]>liquc to the hinge-line at an angle of about 45^ ; length
one-third greater than the height ; ante-byssal margin oblique above, curv-
ing into the marked sinus, regularly rounded along the base and posterior
extremity.

Left valve depressed-convex below, more convex above, and moderately
gibbous on the umbo. Right valve unknown.

Hinge-line straight, about equal to the 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 striae, with sharp lamellaa at nearly regular
intervals over the body and wing, becoming crowded and fasciculate on the
anterior of the shell.

Interior unknown.

A specimen has a length of 35 mm., height 24 mm., and hinge-line
33 mm.

This species differs from L. Corydon in its shorter and broader form ; the
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 Chemung group at Kelly's creeks
and Mansfield, Tioga county, Pa.

LAMELLIBRANCHIATA. 217

Leptodesma nereus, n. sp.

PLATE XC, FIGS. 31^33.

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 umbo.

Hinge-line straight, less than the length of the valve.

Beaks sub-anterior, acute, directed forward, rising slightly above the
hinge-line. Umlx)nal region gibbous in the left valve, narrower but equally
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 striae, 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 Ime 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 length of 34 mm., height 24 mm., and hinge-line
28 mm. A right valve has a greatest length of 31 mm., height 20 mm., and
hinge-line 25 mm.

218 PALEONTOLOGY OF NEW YORK.

This species resembles L. Orcus, but the wing is wider, less deeply and
abruptly sinuous, and the striae turn more abruptly forward at the junction
of the body and wing. 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, sub-rh(miboi(hil ; body ovate, rapidly narrowmg toward
the beak, oblique, making an angle of a))Out oU° with the hinge-line ; length
one-third greater than the height; ante-lnssal margin oblique and curving into
the distinct sinus ; ventral margin gently curved, joining the broad, rounded,
posterior extremity.

Left valve gently convex below, becoming more convex and slightly
gibl>ous above the middle. Right valve depressed in the lower [K)rtion,
in the middle and a]K)ve about eciually 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, but little elevated above the
hinge-line in the lel't valve. Umbonal region narrow, and abruptly gibbous.
In the right valve the beak is depressed, and the umbonal region a little
less gibl)ou8 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 moderately concave, the greatest concavity being above
the middle, from which point it turns abruptly outward and the extremity
is proiluced into a spiniform extension. In the right valve the wing is less
distinctly limite<l from the Ijody than in the left.

Te.«t thin, marked by 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.

■

lAMELLIBRANCHlATA. 21!)

Muscular impression large, oub-circulftr, situated below the middle of the
posterior slope. The palliii! line extonda from the lower part of the muscu-
lar impression, parallel to the basal and anterior margins, into the cavity of
the beak. Ligamcntal area wide.

A left valve of this species has a length of ^-i-i mm., height 26 mm., and
hinge-liue 33 mm. A somewhat larger right valve has a length of 38 mm.,
height 28 mm., and hinge-Une 33 mm.

Formation and locality. In the shales of the Chemung group at Canton, Brad-
ford county. Pa.

LEPTnUESMA ObOS, U. Sp.

SuKLi. above the inerliiim size, sub-rhombuidal ; body broadly ovate, abruptly
wntracted towards tlie anterior end, oblique at an angle of about 50° with
the hinge-line; ante-byssal margin olflique, curving into the marked sinus,
thence gently curving to the posterior extremity, which is broadly rounded.

Left valve deprpHsed-couvex below, moderately convex above. Right
valve unknown.

Hinge-line straight: length about five-sixths the greatest length of the
valve.

Beak sub-auterior, directwi forward, slightly rising above the cardinal line.
Umboual region moderately gibbous, subtending an acute angle.

Anterior end triangular, abruptly acute at the extremity, defined by 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 juid terminating in a
sharply angular extension of the cardinal line.

Test thin, marked by sharp, elevated, concentric Btrise with finer inter-
mediate ones. The strongei- stria) lu-e regular on the wing and posterior
Bide; 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.,
height 32, and 30 mm., hinge-line 40, and 35 mm.

This species resembles L. Pelops^ but the body is broader and less oblique,
the anterior portion not so attenuate, the wing somewhat wider, the greatest
sinuosity in the margin of the wing being nearer to the cardinal line, and the
extremity of the wing more acuminate.

Formation and locality. In shales of the Chemung group, Mansfield, Tioga
county. N. Y.

Leptodesma aliforme.

PLATE XXII, FIG. 28 ; AM) PLATE XCI, FIG. 2.
I^ptodrmna aliforme^ Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 22, fig. 28. Jan., 1883.

Shell large (right valve), elongate, triangular ; body narrow, spatulate, oblique
at an angle of about 30^ with the 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 posterior
extremity, which is abruptly rounded.

Right valve nearly flat below, depressed-convex in the middle, slightly
gibbous in the umbonal region. Left valve unknown.

Hinge-line straight ; length equal to the greatest length of the shell.

Beak sub-anterior, depressed, directed forward.

Anterior end narrow-triangular ; extremity attenuate, very acute. Wing
narrow, elongate, triangular, extending to the 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 striaB.

Muscular impression large, situated at about the middle of the length of
the posterior slope. Pallial line continued parallel to the anterior side, with
slight interruptions, nearly to the beak. The hinge is furnished with a slen-
der, oblique lateral tooth.

LAMELLIBRANCHIATA. 221

The specimen described is 60 mm. in length, with a height of 29 mm.,
and hinge-Une 61 mm.

This species bears considerable resemblance to L. extenuatum in the characters
of the right valve ; but it is proportionally narrower, the posterior extremity
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. 12; an'I» 1»LATK XCI, FIG. A.
Ltptotlemna rttde* Hall. Pal. N. V'., vol. v, pt. 1. Plates and Explanations: PI. 25, tig. 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 curvmg into the broad
sinus ; ventral and posterior margins broadly rounded.

Left valve convex below, becoming narrow and gi])bous 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 striaB, 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 of 51 mm., height 37 mm., hinge-line a>x)ut
42 mm.

Specimens of this species usually present a very rough and irregular aspect
from the chanicter of tlie sliell, with its strongly lamellose structure and the
coarse matrix in which it is usually found. The specimen figured is a cast of
the interior, and is distinguished by the broad posterior end and abrupt naiTowing
toward the front, the obtusely sub-angular umbo, and the large anterior end.
In a crushed specimen retaining both valves, the right valve is almost equally
convex with the left; the surfjice is less lamellose and presents only gentle
undulations.

Formation and locality. In a coarse sandstone of the upper part of the
Chemung group, on the roiwl from Olean, N. Y., to Smethport, Pa.

Leptodesma Biton, n. sp.

PLATE XCl. FKi 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. Right valve unknown.

Hinge-line straight, greater than the height of the valve.

Beak sub-anterior, directed forward, but little elevated above the hinge-
line. Umbonal region abruptly gibbous, subtending an acute angle.

Anterior end produced, narrow, acute at the extremity, limited by an
oblicjue, shallow byssal depression. Wing large, joining the body at the
posterior end, not distinctly separated ; margin slightly oblique below, gently
concave a])ove the middle, and curving slightly outward just below the car-
dinal line.

Test thin; cast nuirked by fine concentric striae of growth, which, at

LAMELLIBRANCHIA TA. 223

intervals, have been elevated into fascicles, and on the external shell, were
probably sharp lamellose striae.

Interior unknown.

The specimen described has a length of 50 mm., height 31 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. Maclurii 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 Smethport, McKean county. Pa.

Leptodesma Lesleyi, n. sp.

PLATK XCr. 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 ])roadly 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 sul)tending a very acute angle.

Anterior end large, limited by a broad, distinct, oblique byssal depression ;
extremity flattened and acuminate. Wing large, triangular, joining the
body near the post-basal extremity, limited by the a])rupt forward ])ending of
the striaB ; 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 fascicu-
late and lamellose on the ventral side and anterior end, and are shown on
the wing as sharp, elevated, regular striae. Some specimens preserve fine
regular striae on the body of the valve, but they are usually somewhat irreg-
ular and lamellose. In an exfoliated and macerated condition they show
fine radiating lines which probably belong to the intimate structure of the
shell.

Ligamental area (as preserved in an imperfect right valve) 1.5 mm. wide,
and marked by very fine, minutely undulating longitudinal striae. 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, aviforme, but is distinguished by its more
oblique form, and wider anterior end. Specimens are quite abundant in an
argillo-calcareous sandstone of the Upper Chemung group, associated with
Spirifera Vemeuili.

Formation and locality. In the Upper Chemung group, Auburn township,
Susquehanna county, Pa.

Leptodesma aviforme, n. sp.

PLATE XCI, FIG. 8.

Shell large, sub-rhomboidal ; body elongate-ovate, broad behind, and rapidly
narrowing toward 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 gently 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. Umbonal 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, ha,s a greatest width of from 25 to 28
mm., and measures from 12 to 14 mm. in the narrow part between the beak
and the byssal sinus.

This species differs from L. Pelops in the longer and more erect 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.

J*LATE X( I. FIG. I).

Shell of medium size, rhomboid-ovato, 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 vontral margin ; })osterior margin abruptly rounded

and recurved.

226 PALEONTOLOGY OF NEW YORK.

Left valve moderately convex in the middle, gibbous on the umbo,
depressed-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
the middle of the cardinal line. Umbonal region gibbous, subtending an
acute angle.

Anterior end comparatively large, produced into a nasute extension.
Wing small, narrow-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 umbo 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. In the Chemung group, Lawrenceville, Tioga county.
Pa.

Leptodesma patulum, n. sp.

PLATE XCI, FKiS. 10, II

Shell above the medium size, sub-rhomboidal ; body 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, scarcely gibbous above, similar in form ;
the right valve being a little smaller and less convex than the left.

Hinge-line straight, somewhat longer than the height of the shell.

Beaks at about the anterior third of the hinge-line, directed forward,

LAMELLIBRANCHIA TA. 227

somewhat prominent. Umbonal region moderately gibbous, not strongly
defined. Umbonal angle acute.

Anterior end large, produced into a nasute extension. Wing large,
joining Jthe 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 regidar 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. jlaccidum in its much larger wing, which is more
extended along the body of the shell. It is less convex and the umbo less
gibbous than in any of the preceding species.

Formaiion and locality. In the upper part of the Chemung group at Mans-
field, Tioga county, Pa.

Leptodesma complanatum.

PLATE XXII, FIG. 1.

Leptvdttnna cmnplamituuu Hall. Pal. N. Y., vol. v, i)t. 1. Plates ami Kxiilanatioiis : PI. 22, tig. 2.

Jan., 1883.

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 height of tlie sliell.

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 striae, which are more
crowded anteriorly, and very regular on the wing.

Interior unknown.

The specimen (lescri])ed, which is a separate left valve, has a length of
28 mm., height 20 mm., and hinge-line 18 mm.

Formation and locality. In the shales of the Chemung group at Philips-
burg, N. Y.

Section «, arcoidea.
Leptodesma Maclurii.

PLATE XXV, FIGS. 8, 13 ; AND PLATE XCI, FIGS. 13, 14.

Lfptodesina Maclurii, Hall. Pal. N. V., v(»l. v, pt. 1. Plato.s and Explanations: PI. 25, figs. 8, 13.

Jan., 18S3.

Shell large, rhomboidal ; body elongate, sub-elliptical, oblique, making an angle
of about 45° with the hinge-line ; length more than one-third greater than
the height ; ant<»-byssal margin oblique, gently curving into a long, shallow,
undefined sinus ; ventral margin nearly straight, curving abruptly into the
posterior margin, which is rounded and abruptly recurved.

Left valve moderately convex in the lower part, becoming gibbous and
Hub-angular along the line of the axis to the beak. Right valve distinctly
arcuate^ less convex, narrowly giblvous in the umbonal region.

Hinge-line straight; length about equal to the height of the valve.

lieaks Hu])-antt^rior, directed forward, but little elevated above the hinge-
line in the left valve, depressed in the right. Umbonal angle acute.

Ant<»rior end narrow-triangular, limited by an oblique depression which
<*xt<*ndH nearly one-third of the length of the valve to the byssal sinus.

230 PALEONTOLOGY OF NEW YORK.

Hinge-liue straight ; 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. Unibonal region angularly
gibbous above, abruptly defined along the posterior slope. Umbonal angle
acute.

Anterior end short, angular. Wing an undefined, narrow-triangular
expansion; margin straight or a little concave; extremity very slightly
produced.

Test moderatelv thick, marked bv fine concentric strise, which are
fasciculate on the ))ody of the shell, and crowded and lamellose over the
anterior side.

Interior unknown.

A large left valve has a length of M) mm., height 36 mm., and hinge-
line 37 mm.

This species is distinguished from L. Lichas by its larger and stronger form,
being very gi))bous 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-])yssal 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, obtuse, moderately elevated,
directed forward. Umbonal region gibbous, not well-defined anteriorly,
abruptly depressed on the posterior. Umbonal angle acute.

lAMELLIBRANCHTATA.

227

somewhat promiiioiit. Uiiiboiiiil region moderately gibbous, not strongly
defined. Umbonal angle acute.

Anterior end large, produced into a na«iite extonsion. Wing large,
joining ^ho shell at the post<?rior extremity ; miirgin scarcely concave,
abruptly produced along the hinge-line.

Test marked by fine lines of growth which ai-c irrcgiUarly fjiiJciculate,
sometimes appearing an equidistant, sharply elevated laincllo! ; 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 hi^s a length of 40 mm., height 26 mm., and
hinge-Une 28 mm. A Himilar right valve has a length of 3G mm., height
24 mm., and hinge-line 27 mm.

This species differs from L. Jlaccidum in its much larger wing, which is more
extended along the body of the shell. It is less convex and tlie und)o less
^bbous than in any of the preceding species.

Formation and locality. In the upper part of the Chemung group at Mans-
field, Tioga comity, Pa.

Lrptodesma complan.\tum.

i'late sxii, fig -j

. I'Ml. N. v.. vol, V. [It. I. rinlPH i>

Jnr

1883.

Shell of medium size, obli(]uely semi-elliptical ; body sub-ovate, moderately
oblifjue ; length one-tbird gi-eater than the height; ante-byssal margin sub-
truncate, gradually curving into the broad ventral margin ; posterior mai-gin
abruptly rounded.

Leil valve depressed-convex, a little gibbous on the umlio. Riglit valve
unknown. a

Hinge-line straight ; length lees than the height of the shell.

Beak acute, incurved, directed forward, moderately prominent. Umbonal

232 PALAEONTOLOGY OF NEW YORK.

extremity, undefined; margin straight or slightly concave, very oblique;
extremity slightly produced, angular.

Test marked by regular, even, concentric stria?, which, when well preserved,
are elevated and lamellose, and arc (crowded and fasciculate on the anterior
end of the shell.

Interior unknown.

A nearly entire left valve has a greatest length of 45 mm., height 20 mm.,
and hinge-line 26 mm. A simihir right valve has a length of 37 mm.,
height 18 mm., and hinge-line 22 mm.

This species is very similar to L, Lichas, l)ut differs in the greater convexity
of body, undefined byssal depression, and narrower wing.

Formation and locality. In the middle portion of the Chemung group at Mans-
field, Tioga county, Pa.

Leptodesma Lichas.

PLATE XXI, FIGS. 31^-39 ; AND PLATE XCI. FIGS. 1«. 20.

Leptodesma Liclms, Hall. Pal. N. Y'., vol. v, pt. 1. Plates and Explanations: PI. 21, figs. 35-39.

Jan., 1S83.

Shell of medium size, sub-rhoml)oidal ; body sub-cylindrical, very oblique ;
length nearly twice the height ; ante-byssal margin subtruncate, extending
below to the broad, gently curving l)ase ; posterior margin abruptly recurved.

Valves very convex above, gently convex toward the posterior extremity,
making the body somewhat cylindrical. Right valve probably a little
shorter than 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 byssal 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.

229

Wiug large, umlefined ; margiu very otilitiue in the lower part, slightly
concave above, the gruat«8t concavity being a little below Ihe hinge-margin ;
extremity produced into mi angular extension. The right valve shows less
distinction between the bo<ly of the valve and the wing.

Test thin, mai-ked by distant laraellose lines of growth with 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 uuknowu.

Hinge, posterior to the beak, furnished with a sleuder lateral tootlj

A left valve of this species has a length of 55 mm., height 3o mm., hinge-
line 37 mm., and the body, at the posterior end, having a width of 25 mm.
A right valve lias 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 iji tlie same rock. The species is
distinguishetl by its straight ventral side and the nearly parallel direction of
the sides of the body in the left valve.

FormalioTi and localities. In a coarse sandstone of the Upper Chemung group,
on the road from Olean, N. Y., to Smethport, Pa., and at Bradford, Pa.

Leptodesma abcifobme, n. sp.

PLATE ICI, FIG. Vi.

Shell large, narrow, sub-rhomboidal ; body sub-cylindrical, oblique at an angle
of about 30° to the hinge-line ; length nearly' ono-half greater than the
height; anterior margin oblique, merging into the broad, low ciu-vatiu-e of
the ventral margin ; posterior margin abruptly rouuded and curvmg 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 lieight
of the valve. The right valve is less gibbous, but otherwise similar to the
left.

234 PALAEONTOLOGY OF NEW YORK.

Anterior end convex, limited hy 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 ol)lique, straight or slightly convex ;
extremity obtuse-angular. An imperfect right valve presents about the same
characters of wing.

Test marked by fine strise 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, l)road, sub-quadrate form. It has
very much the aspect of Modiomorpha, l)ut clearly belongs with L. Phaon and
L. LichaSy 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. FKi. 41.

Shell of medium size, rhomboid-ovate ; body narrowly ovate and rapidly
attenuate toward the beak, ol)liquo, 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, sloi)ing 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 forward, scarcely rising above the hinge-

234 PALEONTOLOGY OF NEW YORK.

Anterior end convex, limited by a shallow, oblique, byssal depression which
is nearly as long iis 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 by fine strise 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 Modtomorpha, 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. FK;. 41.

Shell of medium size, rhomboid-ovate; body narrowly ovate and rapidly
attenuate toward the beak, ol)lique, 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, sloi)ing 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 forward, scarcely rising above the hinge-

LAMELLIBRANCHIA TA. 235

line. Umbonal region narrow and moderately gibbous, subtending a very
acute angle.

The byssal depression reaches the margin 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 striae 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
^uid more acute, the byssal sinus not extending so low on the body of tlie
Talve, 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 ; ANI> PLATE XCL FHiS. 22-25.

I/q^todestiM mytUifortne, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 25, tigs. 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.

234 PALAEONTOLOGY 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
Ijody 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 by fine 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 s])oiMos is distinguisheil by its short, broad, sub-quadrate form. It has
v('ry niu(*h the aspect of Modiomorpha, but clearly belongs with L. Phaon and
Ij. lAvhas, Whi(*h are among tlie extreme variations of the species of Lepto-

Fonnatimi and locality. In the Upper Chemung group, Lindley township,
StiMibrii county, N. Y.

Skc'Tion /, mytiloidea.
Lkptodesma acutirostrum, n. sp.

TLATE XCI, FK;. «1.

Hm-AA' "f ifH'diiini size, rhomboid-ovate; body narrowly ovate and rapidly
;iflMiijjtti? toward the l)eak, ol)liquo, making an angle of a little less than
i;/' with the hing(»-line; length nearly one-third greater than the height;
;irit<' l;y?^Nil margin obliiiue, sloping into the shallow sinus; broadly rounded
K#'l//w, th<- nir vat lire continued into the posterior extremity.

Li'Ct vnlv<* dc|)ress(»(l-ronvex in the low^er part, moderately convex in the
roid/ll^-, and y^^V^^^^y giJ>l><>ii« above. Right valve unknown.

|hn/-'-lifM- Hmight, h^ss than the height of the valve.

|t#;ik ;uit<Tior, uiiiite, directed forward, scarcely rising above the hinge-

LAMELLIBRANCHIATA. 237

PTERONITES, McCoy.
Pteronites profundus.

PLATE XXII. FIGS. 25, 26, 27.

PteroniteM profnnduBj Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 22, figs. 25-27.

Jan., 1883.

Shell large, longitudinally 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 with
Spirifera Vemeuili near Olean, Alleghany county ; in the vicinity of East Ran-
dolph, and other places in Cattaraugus county, N. Y.

Pteronites rostratus.

PLATE XXn, FIQ. 24.
Pteronites rostratuSt Hall. Pal. N. Y., vol. v, pt. 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 strisB, 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 fipont.

The umbonal region shows a few concentric undulations, which are not
continued to the middle of the length of the valve.

240 PALEONTOLOGY OF NEW YORK.

PALiEOPINNA, Hall.

PALiEOPINNA FLABELLA.
PLATB XXV, FIG. 18; and PLATE LXXXVII, FIG. 4.

PcdCBopinna flabella. Hall. PaL N. Y., vol. v, pt. 1. Plates and Explanations: PI. 25, fig. 18.

Jan., 1883.

Shell large, bro*adly semi-ov.ate, 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 oblique, sub-truncate.

Left valve depressed-convex in the posterior and ventral portions,
becoming more convex above and moderately gibbous in the umbonal region.
Right valve unknown.

Hinge-line straight, equalling the greatest length of the shell.

Beak anterior, 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 striaB of growth which are cancel-
lated by fine sub-equal radii ; in the cast the concentric and radiating striae
are of nearly equal strength. On 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 the hinge-line of 80 mm.,
height 40 mm. ; measured along the axis of the body the length is about 70
mm., and the anterior truncation is 25 mm. long.

240 PALEONTOLOGY OF NEW YORK.

PALiEOPINNA, Hall.

PALiEOPINNA FLABELLA.
PLATB XXV, FIG. 18; and PLATE LXXXVH, FIG. 4.

PcdcBopinna flabella, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: 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 oblique, sub-truncate.

Left valve depressed-convex in the posterior and ventral portions,
becoming more convex above and moderately gibbous in the umbonal region.
Right valve unknown.

Hinge-line straight, equalling the greatest length of the shell.

Beak anterior, terminal, prominent, directed forward, scarcely rising above
the cardinal line. Umbonal region subtending an acute angle.

Test thin, marked by regular concentric striaB of growth which are cancel-
lated by fine sub-equal radii ; in the cast the concentric and radiating striaa
are of nearly equal strength. On 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 the hinge-line of 80 mm.,
height 40 mm. ; measured along the axis of the body the length is about 70
mm., and the anterior truncation is 25 mm. long.

LAMELLIBRANCHIA TA. 241

The specimen described is a ciist of the interior, preserving the surface
markings in a subdued condition. Tlie anterior margin appears to have been
slightly incurved and tlie truncation resembles that in some forms of Solen.

Formation and locality. In the Oriskany sandstone, Schoharie, N. Y.

Pal.eopinna recurva.

PLATK XAV, Flu. 1«.
Palaopinna rtcurva. Hall. Pal. N. Y., vol. v. pt. 1. Platos nn<l Kxplnnations : PI. 2;'), tig. 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 toward
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 sis far as the posterior
margin ; the body is also more oblique and less convex.

Formation and locality. In limestone of the Upper Helderberg group,
StiifTord, Genesee county, N. Y.

242 PALEONTOLOGY OF NEW YORK.

ECTENODESMA, Hall.

ECTENODESMA BIROSTRATUM.

PLATE XXllI, F1G8. 27-:W ; AXI> PLATE IJCXXIV, FIG. iO.

Ect-enodesrna btrostratum. Hall. Pah N. Y., vol. v, pt. 1. Plates and Explanations: PI. 23, tigs. 27-30.

Jan., 1S83.

Shell large ; body ovate, oblique ; height greater than the length ; margin
regularly curving from the base of tlie 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, much longer than the length of the shell, and, in
extreme specimens, more than once and 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 of the body, subtending an acuto 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, flattened and sometimes bifurcate below ; similar but more acute radii
continue over the posterior wing. In the right valve the rays are more
numerous, finer 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 by fine, even, concentric striae of
growth.

LAMELLIBRANCHIA TA. 243

The specimens show an oblique lateral tooth, with obscure indications of
anterior teeth or folds. Ligamontal area narrow, marked with fine parallel
striao.

A left valve has a length of 45 mm., height 50 mm., hinge-line, when
entire, alK)ut 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
linge-line on lx)th 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.
Llmoptera pauperata.

TLATK XXVI, FKi. \

•f^lmtypUm jKtitix^rain, Hall. Pivlim. Notico Liiin. Sh»»ll.s «»tc., pt. 2, !>. KJ. T>oc , 18(50.

Pal. N. v., voL V. ]>t. 1. Platf»s and Explanations: PI. 26, fig". 5. Jan., 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. Right
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 body of the shell.
Um)K)nal region moderately gibbous, abrupt on the anterior, and more gently
sloping on the posterior side.

Auricle and byssal sinus unknown. Wing large, triangular, not distinctly
limited from tli(» body, and extending nearly to the post-l)asal extreinitj' of
the shell ; margin slightly concave ; extremity abrupt (rectangular .?).

244 PALEONTOLOGY OF NEW YORK.

Test marked by strong rounded radii, with alternate smaller ones ; or finer
])ifurcating ra^'^s between, which are somewhat curved as they approach the
beak. The entire surljice of the shell is marked by fine concentric striae,
which become crowded and lamellose, o])scuring and partially obliterating
the rays ; the striae on the lower part of the ])ody 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 lamellae.

Interior characters and ligamentxil 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 itamilton 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.

Ltmoptera cancellata.

PLATE XXVI. FI(;S. 1-4 : axd PLATE XCH, PIGS. 1-3.

Ltmoptera canvellnta^ Hall. Pi-olim. Notico Lam. Shell8, etc., pt. 2, p. 16. Dec., 1869.
" *• ** MiLLKR, Cat. Amer. Pal. Foss., p. 193. 1877.

Pal. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 26, figs. 1-1.
Jan.. 1883.
Liitwptera cancellata^ var. wcidctut^ II. axd W. Twenty -Fourth An. Rep., N. Y. State Museum Nat. Hi^t.,

]). 199, pi. 11, tigs. 12-15. 1872.

Shell large ; body sub-erect, broadly ovat^ ; axis nearly vertical to the hinge-
line ; wing expanded ; height and length nearly equal ; ventral margin
very broadly rounded; ant<}rior 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

246 PALEONTOLOGY OF NEW YORK.

This species is distinguished by its erect form, the broad flat interspaces
between the radii, and the reguhir sharp concentric striae.

Formation and locality. The specimen is from the higher beds of limestone
at the Falls of the Ohio, which are of the age of the Hamilton group.

LiMOPTERA MACllOPTERA.

PLATE XXIV. FIG U; PLATK XXVI. FIGS (J-9 ; PLATE XXVII, FIGS I-IO ; PLATK XXVIII, FIGS 4,5: PLATE

XXIX, FIGS. 1-4; AND PLATK X(1I, FKiS. 4-».

fAnut ftmcmpfcm, Coxrad. Anniitil Report N. Y (T(»olc)^^ Siirv., p. 117. 1838.
Lhiioptem macnrptera (Conrad), Hall. Pivlim. Notice Lani. Shells, etc., pt. 2, p. 17. Dec, 186t*.
•* ** ** S. A MiLLKR, Tat. Ainer. Pal. Fos». 1877.

Hall. Pal. N. Y., vol. \\ pt. 1. Plates and Explanations: PI. 24, tijc. 14;
1)1. 2«). tip*. (5-9 ; pi. 27, figs. 1-10 ; pi 28, fig.-^. 4, 5 ; anci pi. 29.
fife^. 1-4. Jan., 1883.

Shell large ; including the cardinal expansions, the form is subquadrate ; lK)dy
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 unequal. Left valve ranging from moderately convex to
very gibbous, often somewhat regularly arcuate from l)eak to base. Right
valve smaller than the opposite, in young specimens nearly flat below,
depressed-convex in the middle, and more convex in the umbonal region ;
in specimens of medium size there is often a greater convexity in the upper
•part, and in very old specimens the surface is depressed-convex and 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 prominent, acute, inclined forward, rising alK)ve and
arching over the cardinal line, situated anterior to the middle of the body of
the shell. Umbonal region prominent, convex in young shells and gibbous
in older ones, limited anteriorly by a distinct sulcus, and posteriorly by the
abrupt umbonal slope. Beak of right valve acute, scarcely rising above the
hinge-line, defined anteriorly hy the l)yssal sulcus, and posteriorly by the
abrupt depression and distinct limitation of the wing, Umbonal angle acute.

LAMELLIBRANCHIA TA, 247

Ear snially well-detineJ in young speeinieii.s, and scarcely increasing in
size in proportion to the growth of the shells, limited by a distinct byssal
depression ; extremity rounde 1. 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-
equidisbmt, rounded radii, with slightly concave interspaces, in which are
oft^n finer, or obscrnxdy developed jays ; 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 striae, which are
more distant and conspicuous on the right valve. In the young shells, the
radii are conspicuous on the wing ; thoy 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 surftice is marked by
strong, irregular, concentric, lamellose undulations. The radii oft<in 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 striae. There is a conspicuous obliijue 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 oo nmi., and hinge-line 32 mm. The margin of the left
valve, which remahis in the matrix, shows it to have luid a length of 42 mm.,
and a height of 53 nun. Another specimen, with the two valves attached,
has the left valve T-") mm. and the right valve O-j mm. in height, wdiile the

248 PALAEONTOLOGY OF NEW YORK.

length of the two valves respectively is 63 and 43 mm. In another
specimen (plate xxvii, figs. 6 and 7), where the two valves are in juxtapo-
sition, 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 broken away to the line of junction of the two valves.
The proportional dimensions of the left valves are subject to much variation,
as is shown in plate xxvii, figs. 2 and 3.

The measurement of two large specimens gives respectively, length 78
and 74 mm., height 90 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., height 103 mm., and
hinge-line 84 mm.

The young shells of 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 characteristic of the genus.

The form and proportions of the fossil are subject to great variations 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 extremes. Some of the distorted forms are illustrated on plates
xxviii and xxix. In the older specimens, the obliteration or obsolescence of
the radii below 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, and the margin sinuate,
while the surface is distinctly marked by the radii. These features are
gradually lost as the shell advances in age, until the margin of the wing
becomes nearly or quite direct, the extremity of the wing obtuse, and the
surface marked only by the concentric striae of growth. In old specimens the
ear is often obscure, and scarcely retains the proportionate size of that
appendage in the younger shells.

Formation and localities. In the Hamilton group, at Cazenovia and other
localities in Madison county, and in Otsego and Onondaga counties, N. Y.

LAMELLIBRANCHIA TA. 249

LlMOPTERA 0B80LETA.
PLATE XXIX. FIGS. 5, 6; PLATE XXVI, FIG. 10? ; AND PLATE XCII, FIG. 10.

Xjtuutptera otsoletOt Hall. Prelim. Notice df Lam. Shells, etc., pt. 2. Dec, 1869.

Pal. N. Y., vol. V, pt. 1. Plates and Explanations : PI. 29, figs. 5, 6. Jan., 1883.

•« «• t«

Shell large; body ovate, erect or slightly oblique; height greater than the
length ; basal margin 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 ])elow, 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 above 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 striaB 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
strisB 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 striae 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

250 PALEONTOLOGY OF NEW YORK.

mm. ; 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 oblite-
rating the nidii ; but L, macroptera, with its more convex form, and marked by
it« charact<jristic 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 XXVIir. FIGS. 1-8.

Lhnoptera cnrrata. Hall. Pit'liiii. Notice. Lnni. S1m»11s, ot**., i)art 2, p. 18. Di>r., 1800.

Pal. N. Y., vol. v,pt. 1. PhitoH and Explanations; PI. 28, fiffP. 1-3. Jan.. 1883.

Shell large, sub-rhomboid-ovate in outline ; body broiidly 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 l)elo\v, becoming somewhat gibbous
on the umbo. Left valve, with the beak, very prominent and incurved ;
beak of right valve rising but little al)()ve the hinge-line.

Test thick, marked by strong rounded radii with intermediate finer lines
which become oljsolete on the lower part of the valve. The radii are crossed
by fine, closely arranged stria} of growth, which at intervals are crowded and
lamellose, especially toward the margin of the valve.

The internjd cast shows the anterior muscular impression situated at the
extremity of the rostral cavity, from which the pallial line, marked by a
row of strong pustules, extends nearly parallel to the 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

252 PALEONTOLOGY OF NEW YORK.

BYSSOPTERIA, Hall.

Byssopteria radiata.

PLATE XXXII. FIGS. 21, 22; and PLATK LXXX, FIG. 11.

Mytilarca radiata^ Hall. MS. 1877.

*• •♦ S. A. MiLLBR. Cat. Amer. Pal. Foaails. 1877.

BysstypUria radiata. Hall. PaL N. Y., voL v, pt. 1. Plates and Explanations: PI. 32, fi|CF. 21.22:

pi. 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. Entire
surface marked by striae of growth which become elevated into fascicles
toward 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 locality. In the Upper Chemung group at Mansfield, Tioga
county. Pa.

254 PALJEONTOLOGY OF NEW YORK.

Mytilarca (Plethomytilus) ponderosa.

PLATE XXX, FI«8. '2-7.

Mytilan-a }nm(ler(Vta^ Hall. Pi*eliin. Notice Lam. Shelb*, etc., pt. 2, p. 21. Dec.. 1809.

** •* Halt.. 8. A. Millkii, Cat. Am«»r. Pal. Foss. 1S77.

PlethoMytilwf jtofiderosus, Hall. Pal. N. V.» vol. v, pt. 1. Plates an<J Explanations: PI. 30, tigs. 2-7.

Jan., 1883.

Shell very large ; body acutely ovate, erect ; height three-fifths the length ;*
ventral margin nearly straight or slightly concave for- about one-half the
length of the shell ; posterior and basal margins abruptly rounded ; dorsal
margin gently curved to the extreniity of the hinge-line.

Valves equal, regularly convex posteriorly, gibbous above and in the
umbonal region.

Hinge-line straight and short. Beaks anterior, prominent, rising much
above the cardinal line, moderately incurved. Ventral side concave with a
slight inflation of the margin at the byssal opening. Dorsal side sub-alate.

Test thick, marked by concentric striaB of growth which become lamellose
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 length of 135 mm.,
height 80 mm., breadth 80 mm. A small example has a length of 36 mm.
and height 23 mm.

This species differs from Mylilurca (P.) arenucea in its greater size and gib-
bosity; from M. {Plethomytilus) cordiformis, IIall=M. (P.) myilimera, Conrad,
and M (P.) ovata, Hall, from the Lower Ilelderberg group, in its more elongate
form and more attenuate apex.

Formation and localities. In the limestone of the Upper Helderberg group,
Helderberg mountains, Albany county, N. Y. ; Chirence Hollow, Erie .county,
N. Y. ; and in limestone of the same age at Columbus, Ohio, and Walpole,
Ontario.

*In th<' mytili)i(i forms tlie leng-th is measm-ed fi-oni tho beak to the iK)stenoi- exti-eniity and the heig'ht is
at right angles to this. The breadth repre^onls the co-i.o::it> of the valves.

LAMELLIBRANCHIATA, 255

Mytilarca (Plethomytilus) oviformis.

PLATE XXXI, FIGS. 1-8 : and PLATE LXXXVII, FIG. 8.

Inoeefam^u orifonnitt^ Conrad. Jour. Acad. Nat. S«'.i., Phila., vol. viii, p. 24(5, j)!. 13, fig* 7. 1842.
MytUarca orifomilM (Cojf rad), ^Iall. Pi*elini. Notice Lam. Shells, etc., x>t. 2, p. 21. 1809.
PletkomytiluM oriformis (Conrad), Hall. Pal. N. V., vol. v,' pt. 1. Plates and Explanations: PI. 31,

tip*. 1-8. 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 byssus.
Dorsal iside sub-alate.

Test thick, marked by fine, close stria? 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 o])li(|uo folds which may have been lateral teeth.
Other characters of the interior unknown.

A large specinu^n has a Ic^ngtli of 74 mm. and height 55 mm. A small
example measures 25 mm. in longtli and 17 mm. in height.

This form differs from M. (P.) ponderosa in its greater proportional height,
Smaller size, and lesser gibbosity.

Formation and localities. In the shales of the Hamilton group at numerous
localities in Schoharie, Otsogo, Onondaga, Ontario, Livingston and Erie
oounties, N. Y.

256 PALEONTOLOGY OF NEW YORK.

Mytilarca (Plethomytilus) Knappi, n. sp.

PLATK LXXXVII, FIG. 13.

Shell of medium size ; body ovate, obtuse, broad below ; height nearly equal
to the length ; ventral margin rounded with a slight sinuosity at the byssal
opening; dorsal margin broadly rounded.

Right valve moderately convex below, somewhat more convex in the
umbonal region. Left valve unknown.

Hinge-line less than the height of the shell. Beak obtuse.

Test thin below, thicker on the upper part and cardinal line. Surface
marked by fine, regular, elevated striae of grow^th.

Ligamental area narrow, coarsely striated longitudinally.

Interior unknown.

The right valve described has a length of 48 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 mac*eration and compression. It is
however clearly distinct from any of the forms here described.

Formation and locality. In the shales of the Hamilton group on the shores
of Skaneateles lake, N. Y.

Mytilarca pyramidata.

PLATE LXXX, figs. 1-3.
Mytilarca puramxdata. Hall. Pal. N. Y'., vol. v, pt. 1. Plates and Explanations : PI. 80, tigs. 1-3. Jan., 1883.

Shell of medium size ; body 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 curving to the
beaks.

Valves equal, convex, gibbous above, and sub-angular along the anterior
umbonal slope. The ventral side is rectiingularly incurved.

LAMELLIBRANCHIATA. 257

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 smooth, but show-
ing lamellose striae on the pallial margin.

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 county, N. Y.

Mytilarca umbonata.

PLATE XXXII, FIGS. 1-7.
Mytilarca umbonata. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanatioif^ : PI. 32, figs. 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 umboiial slope obtusely angular, concave
between this and the ventral margin. Dorsal side not alate.

Hinge-line short. IJeaks 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., breadth 19 mm.

This species diflfers from M. Chemungensis in its shorter and more gibbous
torm ; the beaks more elevated and erect.

Formation and localities. lu the Middle Chemung group, Ithaca, N. Y., and
^ear Mansfield, Pa.

258 PALAEONTOLOGY OF NEW YORK.

Mytilarca Chemungensis.

PLATE XXXn, FIGS. 8-11, IS, 14.

Inoceramus Chemungefisis, Conrad. Jour. Aca<l. Nat. Sci., Phila., vol. 8, p. 246, pi. 13, fig. 9. 1842.
MytUus Chemungensis (Conrad), Phillips and Salter. Memoirs Geolog. Sui'\'. of Great Britain, vol. 2, pt.

1, p. 365, pi. 20, figs. 10, 11. 1848.
Mytilarca Chemungens'ui (Conrad), Hall. Prelim. Notice Lam. 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 ei-ror). Jan., 1883.

<( t( i* t(

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 umbonal slope is obtuse,
sloping nearly vertically to the ventral 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 53 mm. and height 26 mm. An
elongate form has a length of 66 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 the middle portion of the Chemung group,
Rockville, Hobbieville and Phillipsburgh, Alleghany county, and East
Randolph, Cattaraugus county, N. Y.

LAMELLIBRANCHIA TA. 259

Mytilarca carinata.

PLATE XXXII. FIGS. 15-ly ; AND PLATE XXXUl, FIG. 8.

MytUarca carinata^ Hall. MSS. 1877.

•• •* •• S. A. MiLLKR, ill Cat. Ainer. Pal. Fo.ss., j). 107. 1S77.

" *• '* Pal. N. Y.. vol. V, pt. 1. Plates ami Ivxplanatioiis : PI. 8:^, i\gs. 15-10.

Jan., 1S83.

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 gi}>bous 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 striae of growth, which are
crowded on the anterior side and toward the l)ase.

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 h.'is a length of* ^(1 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 diflfers from M, Chemungensis 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 regularis, n. sp.

PLATE XXXII, FIG. 12.

Shell above 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, oblique. Beak nearly erect, acute and abruptly
attenuate.

Test thin, marked by fine elevated concentric striae which are 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. occidentalis and less
elevated along the umbonal slope.

Formation and locality. In a sandstone of the Chemung group, near Leon
Centre, Cattaraugus county, N. Y.

Mytilarca attenuata.

PLATE XXXn, PIG. 20.

Mytilarca (Utenuata, Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. 23. 1869.

" Pal. N. y., vol. V, pt. 1. Plates and Explanations : PL 32, fig. 20. Jan., 1883.

«< «i

Shell above medium size ; body extremely elongate, sub-cuneiform ; length
nearly three times the height ; ventral margin nearly straight for almost the
entire length, with a slight depression at the byssal opening; posterior

262 PALEONTOLOGY OF NEW YORK.

This species is somewhat intermediate to M. Chemungensis and M. re^ularis^
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 be
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 ; ani> 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 striaB, which, at irregular intervals, are
crowded into fascicles, leaving varices upon the surface of the cast.

Interior unknown.

The specimen described has a length of 46 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, pt. 1. Plates and Explanations: PI. 33, fig. 22 Jan., 1S83-

Shell large ; body broadly sub-elliptical, abruptly narrowing toward the bealc
on the dorsal side ; length one-third greater than the height ; byssal

^\^

LAMELLIBRANCHIA TA. 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 imknown.

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 XXXni. FIGS. S-6; AND PLATE LXXXVn, FIG. 11.

MytUua occidentcUis, Whitb and Whitfibld. Proc. Boston See. Nat. Hist., vol. viii, p. 297. 1862.
MjftUarca occidentaJ'ut (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., 1883.

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 striaa, which at irregular
intervals have been raised into imbricating lamellae, leaving strong varices
on the cast.

Interior unknown.

A specimen has a length of 52 mm. and height 26 mm.

This species is distinguished from M. Chemungensis by its straighter form,
erect beaks, and convexity along the medial line.

Formation and locality. In the Yellow sandstones, at Burlington, Iowa.

Mytilarca fibristriata.

PLATE XXXni, FIGS. 6, 7 ; and PLATE LXXXVU, FIG. 6.

MytUus fibristriatust White and Whitfibld. Proc. Boston Soc. Nat. Hist., vol. viii, p. 296. Feb., 1862.

" Whttfiddmniis, Winchell. Proc. Acad. Nat. Sci., Phila., p. 413. Sept., 1862.

" «• " ** " p. 11. 1863.

Mytilarca fibristriata^ (W. and W.), Hall. Prelim. Notice, Lam. Shells, etc., pt. 2, p. 24. 1869.

" fibristriata (W. and W.) {fimbristriata, in error). Hall. Pal. N. Y., vol. v, pt. 1. Plates and

Explanations: PI. 33, figs. 6, 7. Jan., 1883.

Shell of medium size ; body very elongate, narrow 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. Umbonal region
narrowly gibbous.

Test thin, marked by fine, thread-like, undulating radii, which are
more or less interrupted by the fine concentric striae.

Interior unknown.

A specimen has a length of 48 mm., and height 22 mm.

This species is distinguished from M. occidentalis 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, Iowa.

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 retusa.

PLATE XXXm, FIGb. 1, 2.
Ofossdettia rettuta. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 30, figs. 1, 2. Jan., 1883.

Shell of medium size ; body very oblique, rhomboid-ovate, sub-arcuate ; length
one-third greater than the height ; ventral margin nearly straight for two-
thirds of the length, inflated at the byssal opening and concave below,
thence abruptly curving into the broad basal and dorsal margin.

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 by lamellose concentric lines of
growth which at irregular distances are crowded into fascicles.

Ligamental area and interior unknown.

The specimen described has a length of 49 mm., height 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.

268 PALEONTOLOGY OF NEW YORK.

MoDiOLA (Mytilops) metella.

PLATE XXXin, FIGS 23, U ; AND PLATE LX XXVII, FIG 9

Modiola meteUOf Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. 1. 1869.

Mytilops (Modiola) metella. Hall. Pal. N. Y., vol. \% pt. 1. PlatoH and Explanations: PI. 33, li^. 23, 24.

Jan., 1883.

Shell large; body narrow elliptical, sub-arcuate, obliquely truncate on the
anterior dorsal side ; length more than twice the height ; ventral margin
gently curving, nearly straight for three-fourths 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 the middle of the length, and gibbous in
the umbonal region.

Hinge-line oblique, about equal to the height of the valve. Beaks small,
appressed.

Test thin, marked by concentric striaB.

Ligamental area marked by two slender grooves. Other interior characters
unknown.

A specimen has a length of 57 mm., height 25 mm., and hinge-line 24 mm.

This species diflfers from M. pracedens in its larger form, which is less
expanded posteriorly, less angular and gibbous along the umbonal slope, and
without radii on the surface so far as can be determined in the specimens.

Formation and localities. In a conglomerate of the Chemung group, at
Panama, and in a boulder of similar rock on the road from Ellington to Cherry
creek, Chautauqua county, N. Y., and at Warren, Pa.

PLATE I.

AVICULOPECTEX ClEON.

Pajce 6.
Fig, 1. The left valve of the spe<nimMi dosrrilMMl. The siwciineii is not so nearly entiiHj as i*ei»re8ent4;d
in the tig^u^^

Upp«;r llelilerberg" ^roup. Cchnnhics^ Ohio.

AviCULOPECTEX IGXOTU8.
Page 33.

Fig. 2. A left valve, from which the shell hjus been almost entirely exfoliated.

U])per IleMerbery: gmup. JVr^/r Victor, Ont(irw Co., N. Y.

AVICULOPECTEN (PxERlNOPECTEN?) TERMINALIS.

Pago 32.
Fig. 3. A left valve enlarged to two diametei*s.

Upper Helderberg group. IVUliam/tvUU, Erie (h,, ]S\ Y.

Ptekixopkcten INSONS.

Page 69.
Fig. 4. The exfoliated left valve desc'rihed, enlarged to two diametei*s.

Upper Heldei'berg groiij). IVcsUr/i N. Y.

Lyriopecten Dardanus.

Page 4J.

Fig. T) A view of an imj)erfect left valve, taken from a gutta-p<Mr,ha impression of the natural mould,
llie specimen is more exte,n<led on the anterior side than is i*epivsent4»d in the figure, and
thei-e is an intermediate set of finer rays, also, not shown.
Upper Helderberg gn)ii]>. /> Hoy, N. Y.

Pterinopecten multiradiatus.

Page 67.
Fig. 0. The left valve described.

Fig. 7. A view of the impression left in the matnx.

Upper Helderbei'g group. iStafftyrd, Genesee Co., iV. 5''.

AviCULOPECTEN INSIGNI8.

rage 31.

Soe Plates 3 and 81.

Fig. 8. An imperfect left valve, cnlargetl to two <Hnmetei*s.

Hamilton group. /Stafford, Genesee Co., N. Y.

AviCULOPECTEN PECTENIFORMIS.

rage 4.
Fig. i*. The original specimen <lescrib«Hl.

Uppei" Helderberg group. tSchoUarle, N. Y.

PLATE II.

Lyriopeoten interradiatus.

Pace 44.

See Plate 82.
Fig. I. A small left valve.

Fig-. 2. A 8i>ecimen of medium size.

Fig. 3. The light valve belonging t^) the left valve, tig. 1.

Fig. 4. The right valve of tig. 2.

Hamilton giH)up. PtUtonham^ Sckoharie Co,, N, F.

AviGULOPBOTBK BELLUS.
Page 89.

See Plate 81,
Fig. 5. A small left valve, X 2.
Fig. H. A similar left valve, X 2.

Fig. 9. A specimen pi-eserving both valves, showing their (M>m(>ai*ative form and i^elations, X 2.

Hamilton gi*oup. Near BelU^tva, N. Y.

AVICULOPECTEN ORNATU8.

Page 37.

See Plate 8.

Fig. 7. A small specinwii pit'.si^rving both valves slightly dieplaced, and the right one imi>erfert ;

showing the ft>rm aiul ornamentation, X 2.
Fig. 8. A larg«r specimen, similar to the ])n»ceding, but with the surface characters partially obliterate<l

from maceration, X 2.

Hamilton gn)up. Cawnid-aigii'a lake, N. Y.

PtERINOPEOTEN UND08U8.

Page n.
See Plate 82.

Fig. IQ. A small left valve, showing the gi-eat proiK)rtional length of hinge-line in the young shell.

Hamilton group. Canandaigua lake, N. Y,
Fig. 11. A large left valve, having very distant equal itidii.

Hamilton group. Bethanyj N. Y.
Fig. 12. A right valve, showing numerous concentric undulations.

Hamilton gi*oup. CaftaruUiigua lake, N. Y.
Fig. 18. A right valve preserving two strong undulations in the umbonal region, moi-e subdued concentric
lines below, and nnmerous tine radii.

Corniferous limestone. Clarence Hollouc, N. Y.
Fig. 14. A right valve pi*eserving a portion of the test on the upper antenor side and anterior ear.

Hamilton gi*oup. Canandaigtui lake, N. Y.
Fig. 15. A characteristic right valve.
Fig. IH. A large right valve, showing numerous concentric undulations.

Hamilton group. CanandaigiM lake, N. Y.
Fig. 1 7. A small specimen preserving both valves and showing strong undulations.

Hamilton gi*oup. Canaiidaigua lake, N. Y.
Figs. 18, 19. Two nearly entii*e large left valves.

Hamilton group. GeneseOf Livingston Co», N. Y,

PLATE III.

AVIOULOPECTBN IdAS.
Pa«el3.

See Plate 24.
¥1g. 1. A small ri^ht valve.

Hamilton group. Fultonham, Schoharie Of)., N. Y.

Fig. 2. A largvr «»xampl« of more nearly normal proj>ortioiw.

Hamilton jrroup. Dnritn, N, Y.

AVICULOPEOI'EN SGABRIDUS.

rage 7.
Pig". 3. A young" inilividual. apparently, <)f this sptM.*it*s, slightly nari'«)we<i by compivsHioii.

HainiltxMi group. Belloiut., N. Y.
Pig". 4. A hrft valv»» with tho surfnxie much ilLstort***!, Imt juM'stM-ving a v«»ry poi-fert outline.

Hamilton gT<»up. Canandahj^ui Jake^ N, 1".
Pig". j>. The ranlinal portion of a right valv»».

Hamilton gn >up. ISchiiharle Co,, JV, Y.
I?*i|r. tJ. A left valv«.' of mf«liuni size ; imjM'rffM't at the ranliiuil rxtn'uiitit's.

Hamiltnii gn)U]>. Dtlphi f\i/h, N. Y,
l?!^. 7. All imperf»M*t ni^ht valve pn*si»rving thn surface chanu'.ters of th<» ♦•ai's, as obtained from the

matrix after the removal of th«» pjHn'impn.
H'ig'. 8. An enlargt»m«Mit from the sui'faee of a specimen pn^serving the; test.

Hamilton group, f/tfiesfo, Livingston Co., SV. V.
li^ig". 9. An Hnlarg«Mn<'nt of th<» surfa<'«» of specimen, tig. 7, tak»Mi from the niithile of the valve.
V'ig'. 10. A largt* h»ft valve ]ires«»rving a very perfert outline, with a portion of the tr»st adhering to the lower

ant«»rior portion.

Hamilton group. BelUf/ia, N. Y.
li'ig'. 11. An enlargrment of a jiortion of the test of the pi-ecetling spe«Mm«'n.
^^ig". 12. An enlarg«'in»Mit fi-oin the surfac'e of a spe<*imen denmled of th«* tr»st.

Hamilton gi*ouj>. f'rimked lake outlet, N. Y.

PLATE m— Continued.

AVIOULOPEOTEN INSIGNIS.

Page 34.

iSee Plates 1 and 81.

Pig. 13. The int<»rior of a right valve imbedded in shale, showing the omainentation as it ap|)ears on the

interior of the shell.

Hamilton g^up. Hamburg, Brie Co., N. F.

AviOULOPEOTEN OENATU8.

Page 87.
See Plate 2.

Fig. 14. The intenor of a left valve imbedtled in shale, X 2.

Hamilton group. Canandaigua lake, N. Y.

AVICULOPECTEN MUORONATUS.

Page 38.

Pig. 15. The interior of a left valve imbedded in shale.

Hamilton group. Dresden, Yates Co., N. Y.

AviCULOPECTEN LAUTUS.

Page 14.
See Plate 81.

Pig. 16. The interior of two attached valvess inibetlded in shale, showing their comparative form and pro-
portions.

Hamilton gi*oup. West Bloo^nfield, N. Y.
Fig. 17. The interior of a left valve pi-eserved as the preceding. Another figure of this specimen is given
on plate 81, fig. 5, t^iken from an impi-ession of this mould.

Hamilton group. York Centre^ Livingston Co., N. Y.

AviCULOPECTEN EXACUTU8.

Pago 8.

Pig. 18. The interior of a left valve iml)edded in shale.

Hamilton gn>up. Haviburg, Erie Co., N. Y.
Pig. 19. A small left valve with the anterior ear impei"fect.

Hamilton group. Canandaigua lake, N. Y.
Pig. 20. A large imperfect left valve. ITie beak is represented as too acute, and the concentric lamellie
ai*e not shown jis on the specimen.

Hamilton group. Hamburg^. Erie Co., N. Y.
Pig. 21. A left valve denuded of the test. The specimen shows the pallial line and muscular impression,

as described in the text.
Fig. 22. The upper portion of a right valve pi*eserving the test.

Hamilton group. Hamburg, Erie Co., N. Y.

PLATE IV.
Lyriopecten parallelodontus.

Page 40.
Fig. 1. The exterior of an impeHV'ct ri^ht valve, as <)btaiiu»«l fn)ni an impression of the exterior of the

shell in the matrix. The sinns in the margin of the posterior eAT is represented as too deep.
Fig. 2. The interior mould of the pi'ccoding valve, showing the ligamental gnwves. The specimen ahv)
preserves traces of th<; pallial line and muscular impivssion.
S<'hoharie grit. Albany Co., N. T.

Lyriopectten orbioulatus.

Page 42.
See Plate 82.

Fig. 3. The interior of a small left valve imbeii<h»d in shale, showing a very pei-fect outline.

Hamilton gi-onp. Grent>se<K Liwngstoti Co., N. Y.
Fig. 4. The exterior of an exfoliated loft valve. This specimen is the original of tig. 1, p. 202, Geolog.
Rept. Fourth Dist. N. Y.

Encrinal limestone of the Hamilton gn)up. i^hore of Lake Erie, N. Y.
Fig. 5. A left valve preserving a portion of the canlinal ai*ea. The ligamental area in the specimen shows
several longitudinal grooves much stronger than repi*oseut*Ml ; the figunt is also too narrow
and the anterior ear too obtuse.

Hamilton group. Baileytovm, X. Y.
Fig. 6. A \&rgt}, left valve, showing the obliquity of the l>ody consetpient to age, and the comparatively
short hinge-lino, although the latter is n'iprt?sente<l as too short in the figure.
Hamilton g7*oup. ^fos('mCt JV. Y.
Fig. 7. A portion of the ligamental area of the right valve of speciniou X 3. showing th«* longitudinal
grooves, with a slight IxMiding outward under tho beak.

Hamilton grou]). York Centre, Liv'mystoti Ct., N. Y.
Fig. 8. A larg(» left valve pres«^rving some portions of the tost, and othorwise cjuite imj)orfe<!t fi*oni mace-
ration and exfoliation.

Hamilton gi'oup. CaiuuuUiigua lake, N. Y.

Lyriopecten macrodontus.

Page 4<>.
See Plate 8.

Fig. 9. A large impei-fect mould of the int4'rior, showing the coarse gi*ooves of the ligamental ai*ea.
The muscular impression is preserved in the specimen, but is not i*epresented in the figure.
Hamilton gi'oup. Worcester, OUeyo Co., N Y.

Lyriopecten anomi^eformls.

PageSS.
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
rays, as represented, are too strong ; they should be fine, imdulating and unequal in size.
Chemung group. Chemung river. Upper Narrows, N. Y.

Lyriopecten tricostatus.

Page 48.
See Plates 7 and 10.

Fig. 11. An imperfect left valve. By a fault in the lithography, the secontlary aiid tertiary rays ai*e
i-epresented too nearly alike, instead of alternating in size and strength.
Hamilton group. Near Summit y Scht)1uirie Co., N. Y.

PLATE V.

Pterinopeoten Vertumnus.

Page 71.
See Plate 83.

Pigs. 1-6, Left valves of various sizes, showing slight variations in outline, and considerable variation in

the number and strength of the rays.
Fig. 7. A small right valve. The hyssal sinus is not i-epresented sufficiently deep

Fig. 8. A specimen preservhig both valves, showing their comparative form and suKace onianjentation.

Hamilton gi-oup. Schoharie Clr>., X, F.

AvIOUTiOPEOTEN fasoioulatus.

Pa^ 11.

See Plate 81.
Figs. 9, 10. Two small left valves.

Hamilton group. FuWniham, Schoharie Co , N. Y.
Fig. 11. A left valve. Another figrure of this s[>ecimen is given on plate 81, fig. 8, showing the concentric
stHffi.

Hamilton gi-oup. CoHhion^ OnUir'w 0>., N. Y.
Fig. 12. A left valve which is much produced j)OHtiM'iorly. Th« specimen is imperfect at the beak, and is
restored in the figui*e.

Hamilton group. F^ultwi?iam, Schoharie Co.^ N. Y.
Vig. 13. An impei-fect left valve, showing strong fasficles of railiating striae.
Figs. 14, 15. Two large left valves, with simple thnmd-like striap ornamenting the surface.
Fig. 16. A small right valve of this species

Hamilton group. Sc7u)harie Co.^ iV. Y.
Fig. 17. A left valve pi-esenting great iri-egularities in the radii, due to accident and intermittent growth.

Hamilton group. Cazeiuwia, jY. Y.

AvICULOPECTEN PRIN0EP8.

Page 1.

See Plates 1, 6, 24 and 81.

Fig. 18. A small left valve preserving a portion of the test.

Hamilton group. Canaiidaiffua lake, iV. Y.
Fig. 19. A portion of the test enlarged, showing the surface ornamentation.
Fig. 23. An imperfect left valve.

Hamilton gi-oup. Western N. F.
Fig. 24. An entire and characteristic right valve.

Hamilton group. Cazenovia, iV. Y.

AVIOULOPEOTEN FORMIO.
Pagpe9.

Fig. 20. An imperfect left valve of the species. The margins of both ears are represented an too concave
in the figure.

Hamilton group. FiUtofihatrit Schoharie Co., N. Y.
Fig. 21. A smaller specimen i-etaining both valves.

Hamilton group. Madison Co,^ N. Y.

AviCULOPECTEN PhOROUS.
Page 10.
Fig. 22. A left valve pi^eserving a nearly entii*e outline.

Hamilton group. Schoharie Co., N. Y.

PLATE VI.

AVICULOPECTEN PKINOEPS.

Page 1.
See Plates 1, 5, 24 and 81.
Pig. 1. A large left valve, much extended posteriorly.

Hamilton group. Seneca lake^ N. Y.
Pig. 2. The impression of the exterior o/a large right valve, showing the ligamental 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. Y,
Pig. 3. An impression of the interior of a right valve. The striated ligamental area is shown in the

specimen, but not represented in the figure.

Hamilton group. HamilUm, Madison Co,^ N. F.
Pig. 4. An imperfect left valve.

Pig. 5. The right valve attached to the preceding, showing the comparative size and ornamentation.
Fig. 6. A small oblique left valve. The hingfe-line should be representee! as straight, and with a strong

ligamental area.
Fig. 7. A specimen preserving both valves.

Hamilton group. BarodinOt 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 represented, 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. HamUtony N. Y.
Pig. 9. An imperfect left valve.

Hamilton group. Skaneateks lake, N. Y.

■ 1

PLATE VII.

AVIOULOPECTBN DUPHCATU8.

Page 17.

See Plate 81.
Pig. 1. An imperfect right valve.

Chemimg grou|). HubbiemUe^ N. Y.
Fig. 2. A left valve, which hIiow.s the prevailing character of the 8i>ecie8 in having the anterior nide longer

and moni exteiuletl than the jKxstenor. The original of the species.
C-hcmnng grnup. PfiUipsbtirg, Alleghany O/., N. Y.
Kg. 3. A Homewliat larger left valve.

Chemung gi-oup. Moikoille, AUegliany Co,, N. Y.
Fig. 4. The snrfm^e of a spt?cimen enlarged to three diameters.

Chemung ^*CMj]). RockmlU, N. Y.
Fig. 5. A left valve. The outline of the figure is somewhat too high and too short, and Ixtai's an nnnatural
resemblance to the succt^'ding species.

Chemung group. Rttckville^ N. Y.
Fig. 6. A right valve. ITie figure i-eprosents the bo<ly too shr>rt, the stnie too sharp and the beak t4M)
obtuse.

CHieuiung gi"oup. Jiaat RaiuJUilph^ N. Y.

Fig. 7. A i^mall left valvp.

Chemung gi-oup. HtH'krfWc, JS. Y,

AVICULOPECTEX RUG J*:ST HIATUS.

Page 16.
See Plate ^<l.
Pig. 8. A small left valve nearly en tin', showing the usual form of the speries.

Chemung group. Philipsbwt'g^ N, Y,
Fig. 9. A larger left valve of similar rharaeter to the pivceding.
Fig. 10. An enlargemtjnt of the surface, showing the character of tin* ornamentation.
Pig. 11. A nearly entin* right valve.

(.-heiiiung gifiup. RiM-kvUle, N. Y.

AVICULOPECTEN CAXCELLATUS.

Page is.
X^'ig. 12. A i-ight valve, showing the iisiuil form an<l proportions.

Chemung group. PfiUi})M)ftrg, N. Y.
l?^g. 14. A i-ight valve pr«?s<.*rving tlu' eai-s and surface markings in a very pei-fect condition.

Chemung group. Connoango, Catfaraugwt CSw., N. Y.
^Ig. 15. An enlargement of the preceding .'*pe<'.inu'n to two diametei-s.
l^'^g. 16. The interior imj)res.sion <tf a right valve, with radii partially i>reserve<l.

Chemung group. Wtatfidd, N. Y,
^^ig. 17. An enlargement <if a small idght valve to two diametei-s.

Chemung group. Conincango, N. Y.
^ig». 18, 19. A right valve, natural size and enlarged. The sp«^cimen is somewhat distorted fi*om pressure,

and does not repres<;nt the normal fi»nn of the shell.
Chemung group. RiHikville^ N. Y.

AVICULOPECTEN ItyS.

Page 20.
I'^ig. 18. The right valve descrilwd.

Chemung group. Ccncust ngo, y. Y.

AviCULOPECTE\ SQUAMA.

P.ige 27.
Fig. 20. A right xalvn •'iilai'gi*d to t\v<» di;nn«*t»'rs, >h<»winir th«' form, eai-s and surface markings.

(,'lnMuung gr(.iup. PluJ'ipslmry, N. Y.

PLATE VII— Contlnaetl.
AviCULOFECTEN DOLABKIFORMIS.

Fig-. 21. A light valve enlarged to two iliametei's. The eniv shoiihl show, m the figure, I'ays similar to
tho8P on the bo<ly of the valve. This tigin-e w fnmi the original 8|-»ecimen of the species.
Chemung group. Ph'dijysburg^ N. Y.

AVICULOPECTEN CONVEXUS.

Pa>re *2x.
Fig. 22. A left valve enlarged tt* two <lian»etei*s. 'Hie nntiM'ior ear should show a slight sinus in the

margin for the bys.sus.
Fig. 23. A protile of the preceding, showing the convexity of the valve. (Original of tig. 6, p. 264, Geolog.
Kept. FouHh Dist. N. V.)

rhemung gi*oup. HockviUe^ N. Y.

AviCULOPECTEN SIGNATU8.

Page 2U.
Fig. 24. A left valve enlargetl t<) two diamet^'i-s, showing the ^form and surface markings. (Original of
tig. 5. p. 264, Geolog. Rept. Fourth Dist. N. Y.)
Chemung gnnip. Jittekvine, N. Y,

LyRIOPECTEN P0LYIK)RII8.
Page 50.

Fig. 25. 'Hie left valve destn-ibed. Thn byssal sinus shouhl 1k» <leej>er than repivsented.

(^hennuig gi-oup. (-asito/Uign^ y. Y.

LyRIOPECTEN TR1C08TATU8.
Pa^fC 48.
See Plates 4 and 10.
Fig. 26. An eidargement to two diamet*M*s of a portion of tlie surface of a sj)eeimen of this sjHH'ies.

Chemung gi-oup. ^far Khnh'a„ y. Y.

AviCULOPECTEN TENUIS,

Viige 39.
See Plate 81.
Fig. 27. A left valve, showing the fonn and surfuc«» markings. The specimen ab*o shows the muscular
impression and pallial line.

Chemung gi'oup. liini loip/t, y. Y.
Fig. 28. A hu'ger specimen of the same. Another tigun^ is given on plate 81, showing moi*e clearly
the chara<!t«iv of the sjiecies.

Chennnig group. iNVar Soliunarutu xV. Y.

AviCULOPECTEN (?EL8rS.

P'igs. 29, 30. A right vadve, natural siz«* an<l enlarged.

Ch«»mung group, ^^ftlatnamui, y, Y.

AviCULOPECTEN ELLIPTICUS.

J'age i'l.
Fig. 31. A nearly entire left valve of this species.

(^heniung grou]). Meadvilfe, Pa.

AviCULOPECTEN PATULU8.
Pagre -24.
Fig. 32. A small right valve iis obfaineil IVom tl»e inii>n'ssioii in th«» matrix. Tlie ears ai-e ]>artiallv
restored in the tigure.

Chemung group. iSalainama^ N. Y.
Fig. 33. A large left valve, showing the charactei*s of the shell as obtained from an impression in a fine
conglomerate. The hinge-line should be repi*esented ii» straight.
CTiemung group. xWar Salamam^^ S. Y.

PLATE VIII.
Pterinopectex sudorbicularis.

Page «0.
S«M' Plata's 24 aiKl 82.

Fig". 1. A nearly <^iit'.iv left valve. The rays an» stroiij^ly or«'milate«l in th«» speeinien &i\i\ do not bifurcate
as repre»w^nted, but inei*eart« in number by intei*stitial addition.
Cheniung" gTOui>. New AlbiiMf Cattaraugun Co., N. T.
Fig-. % A view of another individual. (The original of fig. 1, p. 264, Gteol. Rept. Fourth Diet. N. Y.)

Chemung 'group. HdbbleciUe, N. Y.

PtERINOPECTTEN CRENIC08TATU8.

Page 78.
See Plate S2.

Fig. 3. An impei'fect left valve showing* tin* ('renulate rays.

(^heninng" group. Contncnngo, N, Y.
Figr. 4. A large left valve This specimen is renlrawn' on i)late 82, tig". 14, and i*epreHenta more fully the
fonn and surfat'e onnnnentation.

(^hemung gnnip. Anyelicn, N. Y.

Pterinopecten Nei^'unus.

J*age 79.
Figr. 5. A small left valve, imperfect on the post-canlinal nnirgin.

Cheminig gi^ouji. PhUvpHburg, N, Y.
Fig. 6. A larg^ impei-fect left valve.

(^emung group. PhVlpsbury, N. Y.
Fig. 7. An imj>ei*fect light valve. The spe<'.imen is obsrure and is ernmeously represented as a left
valve.

(Chemung g^roup. Angelhu^ N. Y,

LyRIOPECTEN MAGNIFICU8.
Pagu fil .

Fig. 8. A large left valve obtaine<i from an impi-ession of the matrix. The ligami^ntal ai>»a should be
I'epi'esented as longitudinally striate near the beak.
C^hemung grouj*. Movfroac, Pa.

■

Lyriopecten macrodontus.

Page 4«.
S<»e Plate 4.

Fig. 0. A loft valv«s incorrectly repivsenteil as nearly t-ircular, although in the specimen it correaponds
in form with fig. 10. nie liganiental anra is also shown in the siHicimen.

Hamilton group. Hamiltoiu N. Y.
Fig. 10. A large left valv(!. Th<* anterior margin is ri*stnr«'d in the tiguiv.

Hamilton group. Hamilton, N. Y.

CrENIPECTEN WlNCIIELLI.

I. li Sb 4i BnwQ Hghl v&lvea Bhowiiig the form of this vaJve Mid tbe obaoleeceut BUi-fM« iiiwlunfc«.
Fig». 3S, SB. 37. Tkree l«rt vaIvm, Vig. 25 iacoi-i«cUf i-«preHcntfl the Apecimen aa huving the fuiin of »

lij^hl vrIvc. I'hii tjditk nhcinl'I tiiiii iillgiitly tfiwaiii thi> Infl and thn ptinl
sboulil bv inuiv i^Kturjili'il,
Fig'. S8. The iippi^r piirtiuii nf n left volvo, ouIni'giMl tti twu diftiiiut«rs. shtiwiu); tho foi-m uiiU ;<

fharficti^i-e of thi< eni-H. and the ti'ftiwvurHe ll^'iinicnl»l itrvov^n or i;fu'tila^i< pile.
Fig-. B9. An eiilnr^irimt of the siirfnoe ns nlitoitutd from nn unpi'BBsiun tnkao in the iialunil moiilil

PiR. 80. An enlurnreinetit ne rbomi in »in iinyi-wcimi uf llie I'xti-i'ior l^ft in Ihv iiinti-ix.
Wnvorly siuiilstAii'i. N'noarJt. Oh'w.

AviCULOI'ECTBN (CRE.SirEOTKN?) iNrULTUS.

Pif. 3, An impif miuii uf tlin int'-nor of ii light vmIvu.
Cbfiiiiing g-TOUp. Oleaa, N. Y.

AvicuLoPEOreaf Caroli-

P*geW.
Vig- S. A ):tirliiilly exfoli&ti^d left valve.

Waverly fuindHtone, Krwark. Ohio.

Grenipectejj ohbnuutus.

FigB. fi-8. 'I'hit*e Ipft volveB vnryinp somewhat iu foiia aiid iibliciuity. i

Chemting' p'oup. RoekvUlr. Alltfflirwm iii., N. Y.
Vig. IB, A ri(rht vuJve showiiiff the form of thia valve aud tht- i^w of minuUt cai-ltlage-iiito along the
The pdHtflrior ew is tint suffldentlj' pxttnidi--d iii the lij^re.

CTiGinniiif gTimp. Phltipulnirji, Altrgftani/ f\>„ if. T.
fig. Id, A H^ht v»lv<>. The poftlei-ior eiu-iii the Mjii'dmi.'n iH Buniewhail&i'g^r thnu re]Mi<aflii1j?'l,
Vig. 17. An nnlargemimt, to two lUnniAterB. Bhnwintr thi vnw of .■iii'lilagn-pita iilrmg' the hintp?-

nhomuiiK RTOUp. BotrlniH*. N. Y,

I- in*rpn

CrENIPECTEN AMPLU8.

Page 81.
Fig*. 9. A left valve showing the cartilage pits along the hinge. The ])08teri()r ear as i*epre8ented is too

long, giving the figure the aspect of the nght valve.
Fig. 13. A large left valve. The figui*e should be extended fully 3 mm. on the poetenor side to cori*eBp()nd

with the specimen.

Fig. 18. An imperfect spjecimen, Boniewhat distorted fi-om pressui-e, and referi*ed to this species with some

doubt.

Chemung gi'oup. RockviUet N. Y.

Lyriopecten fasoiatus.

Page 66.
Fig. 10. An imperfect left valve.

Fig. 11. An enlargement of a portion of the surface showing the fasciculate radii and concentric strie.

Chemung group. Leon^ Cattai'ougus Co., N, Y.

Crenipecten Leon.

Page 88.
See Plate 83.
Fig. 12. A left valve of this si>ecies. Another figure of this Hpecimen is given on plate 83 showing nun-e
cori-ectly the charactei-s of the hinge and the fonn of the valve.
Chemung group. L&m, Cattaraugus Co., N. Y.

Crenipecten impolitus.

PaireBS.
See Plate 83.
Fig. 14. A large left valve showing the form and proportions of this species. The specimen preserves
traces of distant radiating lines which are not i*epresented in the figui*e.
Chemung group. Glean, N. Y.

Crenipecten obsoletus.

Page 84.
Figs. 19, 21. Left and right valves. Fig. 21 is fram the original specimen of the species.

Chemung gix)iip. Philipsbiirg, iV. Y.

Crenipecten glaber.

Page 86.
Fig. 20. A view of the original specimen of fig. 10, p. 264, Seolog. Rept. Fourth Dist. N. Y. 1843.
Fig. 22. A larger specimen referred with some doubt to this specimen.

Chemung group. Alleghany Co., N. Y.

Crenipecten micropterus.

Page 86.
Fig. 23. A right valve showing the form and surface characters.

Chemung group. Philipsburg, N. Y.

Crenipecten liratus.

Page 87.
See Plate 83.
Fig. 24. A left valve. Another figure of this specimen is given on plate 83, to show the size of the ears as
preserved in the specimen.

Chemung group. East Randolph, N. Y.

PLATE X.
Lyriopecten Priam us.

S«*e Plate 82.

Fijf. 1. A left valve, showing the form and surfiw'e chanu'tiM-s. The tigiiiti should also show nuineniiis fine

rays on the iK)sterior ear.
Fig. 2. A similar left valve, showing consijlerable variation in the surface characters, and stn»ng liga

mental area with a central cartilage-pit.

Chemung group. Franklin, Dvlaxcnre Co., iV. Y.

AvICULOPECTEN' STRIATUS.
Payc' '2*2.

Pig. 3. A left valve ; the original of fig. 7, p. 2f>4, (leolog. Ri»pt. Foui-th Dist. N. Y. 1843.
Fig. 4. An enlargement of the same, showing mon» distiiu'tly the chanu'tei*?* as dt»scribe<l.

Chemung gi*ou]). Painted Pont, Stvulnn Co., y. Y.

Lyriopfx^ten anomkeformis.

S«'e Plates 4 and Si>.

Fig. 5. A left valve. This sjiecimen is more C(>rrt»ctly r<»prfSHiitt»d on plate 8*2, fig. 2.

Chenumg gi*oup. (^htmuny rvvrk, X. Y.

Lyriopkciex tricostatus.

PjiKe ^.
See Plates 4 and 7.

Fig. 6. An impei-fect left valve preserving a jwrtion of the striateil ligamental aiva and the CArtilage pit.

Chemung gi'oup. Chemung Co., N. Y.
Fig. 7. A small left valve with the posterior side undeveloped fi-om a<*<*.ident or natural deformity.

Chemung group.- Near Klmira, N, Y.
Fig. 8. A large left valve, showing the byssal notch on th«» anterior si<ie and the cx>mpai*ative size of the
anterior and post<»rior eai-s. The post^^rior ear in the sp*H!imen, shows several olyscurt* raya
and the ligamental area is strongly striated.

Chemung git)up. Near Elinira, N. Y.
Fig. 9. A fragment of a large left valve preserving a moi'e extended posterior ear than usual. The

anterior ear is too much extended in the figmv and should l)e i-epresent^d as in fig. 8.
Fig. 10. A left valve with a x)ortiou bi*oken away, showing what appears to be the right valve beneath.
The stitmger radii should be continu(uis over the interval occupied by the other valve, and
the finer lines on that valve should be of the same character as on the left valve.
Chemung gi-oup. 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.

PLATE XI.

Glyptodesma erectum.

Page 153.
See Plates 12, 13, 25, 86 and 87.

Figs. 1, 2. Two opposite valves of the -same individual. Fig. 2 shows the muscular scar and also gives

the comparative elevation of the beaks of the two valves. The left valve of the specimen

also shows the pallial line and muscular impression, which are not represented in the

figure.
Fig. 3. A more entire left valve, having the ears but little extended.
Fig. 4. A right valve having the <!ardinal angles much "produced.

Hamilton group. PtdUmhain, Schoharie Co., N. Y.
Fig. 5. A smaller right valve, showing one of the oblique latei*al teeth.

Hamilton group. Cazejwnia, N. Y,
Fig. 6. A right valve, showing a pi-oportionally greater breadth and moderately extended cardinal

expansions.
Fig. 7. A portion of a large left valve with vei*y large caixiinal alations.

Hamilton group. Madiaon Co.^ N, Y.
Fig. 8. A left valve. Another figui'« of this sjiecimen is given on plate 86, fig. 6.

Hamilton group. Cazenovia., N. Y.
Fig. 9. A large left valve with short broad cardinal angles and unusual height. The impression of the

ligamental area is longitudinally striated.
Fig. 10. A left valve with the cai*dinal angles nari*ow and unusually extended. This form is the Avicula

crucifonnis, Coxrad. Ann. Rep. p. 54, 1841. The specimen preserves the pallial line and

muscular impi'ession, which are not shown in the figui'e.

PLATE XII.

Glyptodesma erectum.

Page 153.

See Plates 11, 13, 25. m ami 87.
Pig". 1. A left valve.

Hamilton group. Cn^etuyvia* *V. Y,
Fig. 2. A vievf of right valve showing pallial and muwulai' inipi-essions.

llaniilt<>n group. Cazenomit N. Y,
Fig. ,S. A left valve pi-eserviug «ti*ong, conceiitri**, lainplloso surfm-e iiiarkingn.

Hamilton group. Madison (h., N. T.
Fig". 5. A small nght valve presei^-ing the lateral U»eth.

Hamilton group. Schoharie Co., N. Y.
Fig. 6. A very <!onvex left valve. The radiating line.«» are n^presented too sti-ongly in the figure.

Hamilton jfroup. HnmilUm, yfadison Co., N. Y.
Fig. 7. The right side of a cast showing a very distinct muscular scar and pallial line. The apparent
double impi-ession of the muscular scar is i)rohably due to an iri'egxilar growth of this part
during its advancement.
Fig. 8. A very larg« and erect left valve, with the cardinal angles much extended. It is of the form of

Avicula €ruc\formis, Conrad.
Pig. 9. A very 1arg« left valve with the test partially exfoliated.

Hamilton gi'oup. Jefferson, Schoharie Co., N, Y.

Glyptodesma erectum, var. obliquum.

Page 155.

See Plate 13.

Fig. 4. A .small left valve nearly complete in form and outline.

Hamilton group. Cnnan/fnigtia lake, N. Y.

Mk.jMiwJ<AV

PLATE XIII.
Glyptodesma ereotum.

PRjce 153.
See PUtes 11, 12, 25, 86 and 87.

Fi|f. 1. The right valve of an indiWdual which preserves both valves. This valve retains its normal
form and shows the muscular scar and pallial line, while the left valve is distorted by
compression.
Fig". 2. An imperfect left valve, showing* the muscular scar and pallial line.

Hamilton group. Madistm 0>., N. Y.
Fig. 3. The left side of a specimen retaining the gi*eater portion of the shell ; on the umbo are some

pustules which indicate points of attachment for small umbonal muscles.
Fig. 4. The opposite valve of the preceding si)ecimen, showing the muscular scar and pallial line.

Hamilton group. Hamilton^ Madison Co.., N. Y.
Fig. 12. An inteimal mould of the upper part of a left valve.

Fig. 13. The interior ds obtained fi-oin an impi-ession of the pi*eceding, in gutta-percha, showing the
cardinal folds.

Hamilton group. PratVs faUsy Oiutiidaga Co., N. Y.
Fig. 14. A view of the right side of a specimen retaining both valves, showing the pallial line, muscu-
lar imp]*ession, and the comparative size of the two valves.
Hamilton group. Madimni Co., N. Y.
Fig. 15. A profile view of a specimen, showing the I'elative form of the valves and the depth of the shelL

Glyptodesma erectum, var. obliquum.

Page 156.
See Plate 12.
Fig. 5. An internal mould of a left valve.

Fig. 6. A view of the interior as obtained from a gutta-percha impression.
Fig. 7. An enlargement of the caiH.linal portion.
Figs. 8, 9. The left and right sides of a specimen which retains the muscular scars and pallial lines,

and shows the charactei-s of the hinge in the left valve.
Fig. 10. An enlargement of the cardinal portion of the preceding specimen, showing the characters of
the ligamental area and cardinal folds.

Hamilton group. Onondaga Co., N. Y.
Fig. 11. An imperfect left valve.

Hamilton group. Madison Co., N. Y. •

PLATE XIV.
Pterinea flabella.

Vhge 93.
8oe Plates 15 and 83.

■

Pig. 1. A left valve of a small specimen of more than usual obliquity.

Hamilton group. Eastern N. Y.
Fig. 2. The left valve of another specimen, g^ven to show the appearance produced by having a |K)rtion
of the margin and wing removed.

Hamilton group. Eastin'n N. Y.
Pig. 3. A left valve of a well preserved specimen of medium size, showing the general form and char-
acters. Hamilton group. EasUm N. Y,
Pig. 4, A left valve somewhat narrower than the pre<!eding.

Hamilton gi'oup. PratVs Falls, Onondaga Co., N. Y,
Fig, 6. A left valve haWng a broad body and extended wing.

Hamilton group. Tally, N. Y.
Pig. 6. A large imperfect specimen with an unuHually large wing.

Hamilton group. Madison Co., A. Y.
Pig. 7. An imperfect left valve of narrow, erect form, showing th*» Mtriated ligamental ai*ea.

Hamilton group. JSkan/^ateles lake, xV. Y.
Pig. 8. The left side of a specimen from which the shell has been removed leaving only the marks of the
stronger radii in the cast, a common condition of tht* specimens from the hard calcareous layers.

Hamilton gi'oup. Delphi, N. Y.
Figs. 9-13. A series of right valves ; tigs. 10, 11 and 12 boiiig the reverse of figs. 2, 8 and 6, respectively.
Fig. 14. A profile view of the specimen tigs. 8 and 11, showing the comparative depth of the valves.
Fig. 15. The internal mould of a right valve, showing the anterior and posterior muscular impressions,
the pallial line with the cardinal and lateral teeth.

Hamilton group. Pratfs falls, Onondaga Co., N. Y,
Fig. 16. The interior from a gutta-percha mould, showing the form of the teeth and the muscular scars.
Pigs. 17, 18. The vertical and cardinal views of a natural internal mould of a fragment of a left valve
showing the characters of the interior.

Hamilton group. Otsego Co,, N, Y.
Fig. 19. The interior, as obtained from a gutta-percha impression.
Fig. 20. The internal mould of a small left valve preserving the hing^e characters and muscular scars.

Hamilton group. OUtego Co., N. Y,
Fig. 21. The inner surface of the cardinal portion of a left valve showing the ligamental area.

Hamilton grroup. PratVs Falls, Onondaga Co., N. T.

Page »:{.

Se»» Plates 14 and 83.
Fijr. 1 . An imperfect l«ft valve.

Upper HelderlMM'if limestone, i^iafford, Gerw^ee Co.^ iV. V.

Fig-. 4. The internal moulti of a small left valve, showing the hinge charactei's anci the miiseulai

impi'essions.

Hamilton group. Otaego Co,^ N. Y.

Fig. 5. The interior as obta-ined from an impn»8sion in giitta-peirha.

Fig. 6. A left valve, having the wing uniiaually larg<» an<l extremely extended.

Chemung group. Mansfield, Pa.

Fig, 8. An enlargement of surface where the int«'rm«Mliate radii are nearly equal.

Fig. 9. An enlargement of surface showing the alternating small radii, and strong, concentric lam

ellose striffi.

Hamilton group. SkaneateUs lake, N. Y.

Fig. 10. An enlargement of a specimen preserved in calcareous shales, showing strong lamellae and ver^

unequal radii.

Hamilton group. Hamburg, Erie Co., N. Y.

The weathering of specimens like the one represented in Fig. 10 often obliterates the finei

surface ornamentation, and leaves the larger rays with transverse ridges marking the plaa

of the stronger lamellse, giving them a nodose character. A specimen in this condition wa

described by Mr. Conrad as Atnciila tuferculata, with distant tuberculated ribs and interme

diate stri®. . . Ann. Rept. Geolog. Surv. N. Y., p. 117, 1838. This name should hav<

been cited in the synonomy of Avicula fiabelia, ])age 93 of this volume.

Pterinea pinguis.

Page 92.
See Plate 83.

Figs. 2, 3. Casts of two imperfect left valves. The specimen fig. 2 is re-drawni on plate 83, fig. 13, to shov

the form of the beak and proj^oi-tions of the valve.

Upper Helderberg grou]). Near Columbus, Ohio.

Pterinea dispanda.

Page 97.
Fig. 7. llie left valve described, showing the form and sui-face characters.

Chemung group. MannfiA-ld, Pa.

Leiopteria Rafinesquii.

Page 161.
See Plat(\s 20 and 88.

Ki^. 11. A*left valve, slightly imp^'i-fect at the extn^mity of the wing. 'Hie nnrich' i.s 8<»nu'what t(M> n
extende<l in the figure.

Upper HelderlMM'g limestone. Dehncdrt, OhitK

Glyptodesma occidentale.

I*a;re 157.
St;e Plate Sr>.

V'ni. 12. All imperfect left valve. This specimen is better representeil on pljite S(», tig. *.♦.

Upper Helderberg limestone. P\ills of tht dhlo.

PLATE XVI.

Pterinea consimilis.

Pagt3 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, shoeing a very bii)ad striated ligamental area.

Chemung group. Near Elmira, N. T.
Fig. 9. A similar left valve of somewhat shoi-ter form.

Chemung gi-ouj). Near Elmira, N. Y.
Fig. 11. A left valve, showing some iiTegularity in the concentric markings of the shell along the ven-
tral margin ; pi'obably due to a natural iri*egularity in the growth of the shell.

Chemung group. Near Elmira, N. Y,

Pterinea Chemdngensis.

Page 98.
See Plate 84.

Fig. 3. A right valve, showing the form and surface ornamentation.

Chemung gfroup. Chetnung river. Upper Narrows, N. Y.
Figs. 7, 10. Two left valves of very erect form.

Chemung group. Chemwng Narrows, N. Y.
Fig. 12. A left valve, more oblique than the preceding.

Chemung gproup. Chemung river. Upper Narrows, N. Y.

Pterinea prora.

Page 102.
Fig. 4. An imperfect right valve, l^e specimen shows the pallial line and muscular scai*.

Chemung group. Near Ehnira, N. F.
Pig. 13. The right side of a specimen presei'ving a part of the right valve lying in the impression of
the left one.

Chemung group. Near Elinira, N. Y.
Fig. 14. An impression of a right valve, retaining a portion of the left valve around the pallial margins.

Pterinea rigida.

Page 101.

Figs.j5, 6. Twt) left valves, showing the characteristic form and oi-namentation of the 8i)e(nes.

Chemung group. Cheinung Co., N* Yr

PLATE XVII— Continued

Pterinopectkn spondylus.

Page 65.
Fig". 16. The interior of a left valve showinpr the spinou.s processes of the i*ays projecting" from the pallia!
margin, enlarged to two diainetei-s.

Hamilton gronp. Canandnigua lake* N. Y.

Pterinopeoten conspectus.

Page 66.

Fig. 17. The exterior of an imperfect right valve as obtained from a gutta-percha cast of the natural mould.

Hamilton group, t^kaiieatelen lake, N. T.
Fig. 18. An exfoliated left valve.

Hamilton group. Skaneateles lake, N. Y.
Fig". 20. A specimen preserving" the fine intermediate rays of the test.

Hamilton group. Darien, GerwJtee Co.. N. Y.
Fig". 21. A left valve with the test removed. The ear is represented as too oblique io the figure.

Hamilton gnx)up. Skaneateles lake, N. Y.

Pterinopeoten intermedius.

Page 68.
See Plate 83.
Fig. 19. A left valve enlarged to two diameters.

Hamilton gi*oup. Cayiiffa lake, ?f. Y.

Pterinopeoten filitextus.

Pago 67.

See Plate 82.

Fig. 22. A right valve preserving the test and showing the fonn of this valve.

Hamilton group. FVom a houLder^ Pine Valley, ChemuTig Co., N. Y.

Actinopteria subdecussata.

Page 110.

See Plate 19.
Fig. 23. A small left valve.

Fig. 26. A somewhat larger exami>le.

Pig. 26. An individual of. medium size showing the fonn and surface markings.

Fig. 27. A left valve, a large portion of which is breken away, showing the interior of the right valve.

Fig. 29. A large left valve.

Fig. 30. A right valve showing a greater extent of the wing than in the opposite valve.

Fig. 31. A specimen of medium size, showing the interior of the left valve occupied by a poi*tion of the

right, and repi-esenting the diflference in the strength of the surface markings on the two

valves.

Hamilton group. All from (^ananrlfiUjiut. lake, fxcept fig. ^ which ^^ from BelUma,
Yates Co.. N. Y.

Actinopteria decussata.

Page 111.

S«.^H Plates 18, 20 and 84.
Fig. 24. A small loft valve.

Hamilton group. Dresden, Yates Co., N. Y.

Fig. 28. A large loft valvo with the teat removed, showing the usual fomi of the shell.

Hamilt(>n group. (Uinandaiifua lake, N. Y.

PLATE XVIII.

ACTINOPTERIA DECUSSATA.

Page 111.
See Plates 17, 20 and 84.

Fig. 1. A large right valve, pi*eserving the lainellfe of the test.

Encrinal liineatoiie of the Hamilton group. Eighteen MUe creeks N. Y.
Fig. 2. The right valve of a specimen preserving both valves. The left valve is i-epi'esented in fig. 9.

Hamilton group. York^ Livingston Co.^ N. Y,
Fig. 3. A right valve. The specimen preserves several rays on the wing which are not i*epi'«sented in
the figure.

Hamilton group. Ghneaeo, Livingston Co., N. Y.
Fig 4. A small right valve showing the ra<lii on the wing.

Hamilton group. Ontario Co., N. Y.
Fig. 5. A small left valve.

Hamilton group. Canandaigua lake, N. Y.
Fig. 6. The left valve of the specimen, fig. 4.
Fig. 7. A left valve preser\'ing a portion of the t«st on the anterior end.

Hamilton group. Livingston Co., N. Y.
Fig. 8. A cast of a left valve.

Encrinal limestone of the Hamilton gix)up. ^Eighteen MUe creek, N. Y.
Fig. 9. The left valve of the specimen fig. 2.
Fig. 10. A left valve showing very tine? surface I'adii.

Hamilton group. York, Livingston Co., N. Y.
Fig. 11. A similar specimen of more elongate form.

Hamilton group. Beltvna, Yates Co., N. Y.
Fig. 12. A large left valve preserving the greater portion of the test.

Encnnal limestone of the Hamilton group. Eighteeii Mile (reek, Erie Co., N. Y.
Fig. 13. A left valve enlarged to two diameters showing the characters of surface in a well-preserved

specimen.
Pig. 14. A farther enlargement of the surface, to show the elevated lamelUe and the mode of inci-ease of the

radii.
Fig. 15. Cardinal view of a specimen pi-eserving both valves partly opened.

Hamilton group. York, Livingston Co., N. Y.

PLATE XIX.

Leiopteria Dekayi.

Page 164.

See Plates 20 and 88.
Fig. 1. A small left valve. The specimen shows no indications of rays such as are repi*esent< d in the
figui*e. Hamilton group. Coirperstowri, iV. F.

ACTINpPTERIA BOYDI.

Page 113.

See Plate 84.
Figs. 2, 3. Two left valves pre8er\nng the surface ornamentation.

Hamilton group. Sclioharie Co.^ N. Y,
Fig. 4. A left valve.
Fig. 5. A small left valve.

Hamilton gi't)up. Jeffei'son^ Schoharie Co., N. Y.
Fig. 6. A right valve with an unusually extended wing.

Hamilton group. Fultxriiham^ Schoharie CV)., N. Y,
Fig. 7. The exterior of a right valve, as obtained from a gutta-percha impression of the natural mould,
showing the spinous processes of the lamelljF.

Hamilton group. Fultonhum, Schoharie Co,, N. Y.
The pi^eceding figui*es repi*esent the forms described as Avicula qtuidrula, Conrad.
Fig. 8. A small left valve. The eai* should be represented as somewhat oblique.

Hamilton gix)up. Jeffei'son, Schoharie Co.^ N. Y.
Figs. 9-11. Three left valves showing grailation in size and slight differences in form and surface char-

actera.
Fig. 12. A small right valve enlarged to two diametei-s. Another figure of this specimen is given of the
natui*al size in fig. 17, pi. 84.

Hamilton gi*oup. Havdltoiif Madison Co. , N. Y.
Figs. 13-15. Three left valves differing slightly in form and surface ornaments.

Hamilton group. Scliofiarie Co., N. Y.
Figs. 16-20. A series of left valves i^epi-esenting the type A. Boydi of Conrad.
Figs. 21-23. Right valves associated with and coriHisponding to the pi^eceding.
Fig. 24. Two individuals, each retaining both valves in contact.

Hamiltoa gix)up. Figs. 16 and 17 are from Schoharie county ; the others are from
Orwiidaga and Madison counties, N. F.
Figs. 26, 27. Two large left valves.

Hamilton gi*oup. Cazenovia, Madison Co,, N. Y.
Fig. 28. The right valve of the specimen, fig. 26, showing the comparative size of the two valves.
Fig. 29. Canlinal 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 concenti'ic striae.

Hamilton gi'oup. Cazenovia^ N. Y,

ACTINOPTERIA 8UBDE0USSATA.
Page 110.

See Plate 17.
Fig. 25. A left valve showing the charactei-s as pi-esei-ved in a coaree shale.

Hamilton group. Cazenovia, N. Y.

AOTINOPTERIA PEROBLIQUA.

Page 116.

See Plate 84.
Fig. 31. The right valve of the specimen described. The left valve of this specimen is figured on plat« 84,
fig. 14. Hamilton group. Cazenotna, N. Y.

PLATE XX.

Leiopteria Conradi.

Pa^e 159.

Seo Plate SS.
Fig". 1. A large left valve.

Harnilti)ii group. Onimndaigtm lak(\ X. T.
Fig". 2. A sjiecimen <»f medium size showing sti'ong' eonc«»iitnc nndiilatioiis.

Hamilton group. Beliona, Yates Co., X. Y.
Fig. 4. A left valve. Another tig-ui-e of this 8i)ecimen is jriven on plat^ 88, tig. 3.

LeI01*1'ERIA BiGSBYl.

I»Hge liwi.

See Plate 88.
Figs. 3, 11. Two left valves showing the form of the shell an<l the tine concentnc stria*.
Fig«. 13, 14. Two right valves.
Fig". 15. A larg-e left valve.

Hamilton group. Schoharie Co., N. Y.

Leiopteria l.evis.

pRge 158

See Plat4- 17.
Fig. 5. A left valve enlarged to two diametei-s.

Hamilton gi-ouj). Ontario Co., N. Y.

Leiopteria Rafinesquii.

P&go 161.
See Plates 15 and 88.
Fig. 6. A small left valve.

Hamilton group. JS)ka?ieatele,s lake, N. Y.
Fig. 7. A larger example showing i-egular (nnicentric unilulations of the surface.

Hamilton group. lidhma, Yates Co., N. Y.

Leiopteria Mitchelli.

Page 166.
See Plate 88.
Fig. 8. A left valve of this species.

Hamilton group. From a Imiddrr in the toicii of CatJierine, Schuyler Co., N. Y.

Leioi'teria Greeni.

Pago 160. •

See Plate 88.
Fig. 9. A large individual i*etaining both valves partly opened, showing the left valve and the cardinal
view of the right valve.

Hamilton gi*oup. Bellona, Yates Co., xY. F.
Fig. 12. An imi)erfeot left valve preserving a i>ortion of the test and showing the regular concentric

lamelliP.

Hamilton gi'oup. i'Vom a houhUr in the tomi of CaiJieriiie, Schuyler Ok, N. Y.

Leiopteria Oweni.

Page 170.
Fig. 10. The specimen described, showing the right valve and the umbo of the left.

Hamilton group. Cannndaigiia lake, X. Y.

Leiopteria Dekayi.

Page 164.
See Plates 19 and 88.
Figs. 16-18. Three left valves diffenng somewhat in form and obliquity.

Hamilton gi*oup. Otsego Co., X. Y.

ACTINOPTERIA DECUSSATA.

Page 111.
See Plates 17, 18 and 84.
Fig. 19. A i*ight valve. Tlie specimen shows the pallial line and muscular impi*ession which features are
not represented in the tigui»e.

Hamilton group. Madison Co., N. Y.

PLATE XXI.

Leptodesma Rogersi.

Page 176.
Fig". 1. A small hlcK'k showing two rigrbt valves of this species, X 2.
¥ig. 2. A large right valve preserving the muci*oiiat« extension of the wing, X 2.

Figs. 3-8. A series of left valves varying in size and general proportion. Fig. 7 also shows a right valve.
Fig. 9. A right valve of somewhat higher fonn than usual.

Hamilton group. Norwich^ Cfienaiigo Co., N. Y.

LErrODESMA SPINIGERUM.

Pag© 177.

See Phite 89.

Figs. 10-13. Four left valves showing slight variations of form and length of spine.

Chemung group. Painted Post, i^teid)en Co., N. F.

Leptodesma loncispixum.

Page 179.

See Plate 80.

Fig. 14. A left valve. This specimen is the original of fig. 3, p. 262, Geol. Kept. Fourth Dist. N. Y.
Rgs. 17-19. Three right valves.

Chemung group. Painted Post, iV". I".

LEirrODESMA ROBUSTUM.

Pago 181.

[See Plate 89.

Figs. 15, 16. Two left valves showing the form and convexity of the shell. The striae on the post-umbonal slope

should extend farther along this slope than represented, before recurving into the wing.
¥lg. 20. A right^ valve.

Chemung group. Painted Post, N. T.

1*L.\TK XXI-Continuf.'.

Lkptodenma potens.

l*a;?e iss.
SCO Flutes 2-J aivl SD.

Ki^^ 21. A ri«^]it v«lve n^forn.'il io this sj)«'oios.

(^hoinuiig-firron]). Covnoaugtu CoiUti'auffu.s Co., y. Y.
Fip. HO. A loft vnlv«* showing" the form and projiortions of tho j<h«»ll.

rhominig- p^Toup. Porhulit\ Catftirauf/iis Co., iV. Y.

Lefi'odesma pkotextum.

Fi^. 22, 23. A h.'ft an<l a ri^''ht valve in the same assneiatii»n.

Chemung'- ^Tou J >. Che.mnug r'mr, Uj^im r XanoiiVt A', i'.

LePTOPKSMA NOCIALE.
Pn*re is?.
Fijrs. 24, 2;"). Two left valves showiiifr tlie ^'orm nf the shell ami siirfaee ornamentation, X 2, from fig". 27.

Chemnn^ g"i*oui). f'ourwtiiKjn, (Utttavanyus Co., N. Y,
Fi^. 2(». An enlar^etl view of a ri^ht valve from the same blotrk.
Fi^. 27. A fragment of stone with several valv«»s of this speeios, natural size.
Fiff. 28. An impression of a left valve, retaining" a part of the rigfht valve in place.

Chemung" grronp. Connroiiifttj Cattarnuffm Co.^ N. Y.
Fig". 38. A frag"m«mt of i-ock with a rig"ht an<l a hrfl valve showing: their comparative form.

C.^hemung: g-ronp. Br(Mtint\ Co., X. Y.
Fig:. 34. A rig"ht valve of larg"er si/e and l)i*oader form, .•is.v;ociated with tig", 33. The extremity of the wing,
shonld be j)roduced farther than is represt^itrd. This and the preceding tigure ai*e referred
to this species with some (h)ul>t.

Leitodesma Moutoni.

J\jge IIKJ.

See Plate 89.

Figs. 29, 31. Two left valves varying somewhat in si/e and propiu'tions.
Fig. 32. A right valve. This specimen is redrawn on plate 89, tig. 10.

Chemung group. Porlmlh\ Caitaraiigits Co., N. Y.

Le1*T()DESMA LlCHAS.

PaffO 232.

Se«' Plate 91.
Figs. 35-37. Three left valves.

Fig. 38. A large loft valve of this siXM'ies. The cardinal extremities sln)uld be produced in the figure to

coiTespond with fig. 37.

Fig. 39. A small nght valve.

Chemung group. Pliilipaburg, AJleghan}i Cn., iV. }'.

LeITODESMA LEPIDITM.

Page lO.').
See Pint.' S9.

Fig. 40. A left valve, as seen lying in th«' rock, ami with a i)art of the right valve in place. The conca\'ity
of the margin of the wing is i^'pn'seutctl as too dec]).
Chemung" group. Phllipshnrgy X. Y.

PLATE XXII— Continued.

Leptodesma umbon'atum, var. depressum.

Puge 199.
StM> Plate 00.
Fig. 14. The specimen described. Another fi<riire of this specimen is g-iven on plate 90, fig. 10.

Chemung group. Kajvili, Caltaravyus Co.. N. F.

Leptodesma naviforme.

I'affc 200.
See Plate 23.
Fig. 16. The left valve described. The anterioi- end should be- represented as more extended and acute,
and the exti*emity of the wing as mucronatc.
Chemung gi-oup. JVifa?* Ithaca^ N. T.

Leptodesma potens, var. juvexs.

Pajre 189.
Fig. 16. A left valve.

Chemung group. JSast Iia/nb)lp7i, Cattarartgu^ Co.<, N. T.

Lkioptkiha Ciihmijn(;ensis.

ViXiHi 172.
Figs. 17, 18. Opposite views of the original specimen sliowiug the left and right valves. The right valve is
imbedded vertically in the rock and htis Immmi mu<!h shortened by the shrinkage or compression
of the layei's, while the surface of the shell has been slightly wrinkled from the same cause.
Chemung group. JiJit/ftt mlhs north of Binyhamtoiu N* Y,

^ Lei^tode.^ma Lysander.

I'ajct) .M«.

See rijite 90.

Fig. 22. A left valve. Tlie figui-e is partially r^^.-itored and should ivjiresent the body as considerably wider.

Chemung group. MansJUId, Tioga Co.^ pa.

Leptodesma extenitatum.

l*ap:e i*07.
See Plate 90.
Fig. 23. An impei*fect left valve. Another figure of this s])ecimen is given on plate 90, fig. 17.

Chemung group. Phillpshuryy Allafhany Co., N. Y.

Pteron'ites rostratus.

Page 238.
Fig. 24. The left valve described.

Chemung group. IlockvUlc, N. Y,

Pteronites profundus.

J'age 2:i7.
Fig 25. A small left valve.

Chemung group. New Albion, Cattornugu^ Co., N. Y.
Fig. 26. A larger example. The anttjrior side shouM show i-eguhir concentric undulations.

Chemung gi*<Mip. Jiandoljt/t, Cattaraugus Co., JN. Y.
Fig. 27. A large individual, imperfect on the anterior end.

Chemung group. Near Clean, iV. Y,

Leptodksma aliforme.

Vti'^o 220.
Soo Plato 91.
Fig. 28. A right valve. This specimen is redrawn o;i plate 91, fig. 2, and represents more clearly the
specific charactei*s.

Chemung group. Near Angelica. Alleghany Co., N. Y.

PLATE XXIII— Con tinuetl.

I^YCHOITERIA SIXI'OSA.
Pa^* 130.

See Plate 85.

Fig. 13. A left valve showing the form and surface characters. The wing should be limited by a shallow

furrow.

Chemung group. iViar Smcth-porU 2^(i,

LErroDESMA Mentor.

Vugc 205.
Soo Phito IM).

Fig. 15. An imperfect right valve supposed to belong to this s])eoies fiimi its assotdation.

Chemung group, ^fur Smdhport, Pa.

Ptvciioptehia Sao.

l»age U%
See Plate S.-».

Fig. 16. A left valve of medium size. The fold an<l furn>w of the wing should 1)0 represented as stronger.
Fig. 23. An associated right valve.

Chemung group. Panama, ('hafttavqua Co., X. T.

Ptyciiopteima Salamanca.

Figs. 17, 18. Two left valves showing the form (»f the shell and surface chnractei*s. Fig. 18 should show an
alar fold similar to flg. 17.

Fig. 19. A cai-dinal view of the specimen, tig. 18, showing the ivlativ** convexity of the valves and the com-
parative eltjvation of the beaks.

Fig. 20. The right side of a sjiccimen preserving;' botii valves partly <^p«Mied,

Chemung givup. Acar Salamnura, ?^, Y,

Ptyciiopteria alata.

Page la*.

See Plate 85.
Figs. 21, 22. Two small right valves.
Figs. 25, 26. Two larger characteristic right valves.

Chemmig gi-oup. Salamanca, iV. Y.

Ptyciioi*ieria Eucrate.

Page; l.«.
See Plate 85.

Fig. 24. The right side of a sj>ecimen i»reserving lM>th valv<»s.

Chemung gi*oup. Panama, N. Y.

Ectenodesma iurostratum.

Page 242.
See Plate 84.

Fig. 27. A right valve i*eferred to this species, showing th«' form, sui'face ornamentation and strong, oblique
lateral tooth.

Chemung group. Kour miles north of Chrnango Forks, N. Y.
Figs. 28-30. Three left valves in difTerent degre«\s of i>res(?rvation, showing some variation in form and
surface markingrs.

Chemung gi'oup. Franklin, Dila^aire Co., N. Y.

PLATE KXIV— ConUimed.

Pterinea (Vertumnia) REVERSA.

Pago 104.
See Plate 84.

Fig. 6. A large right valve. Another figure of this apecimen is given on plate 84, fig. 24, tojshow the
obsolescence of the rays on the wing.

Chemung group. Elmiraj N, Y.
Fig. 12. A specimen with the valves united along the hinge, showing the convex right valve and flat or
concave left valve.

Chemung group. Chemung river^ Upper Narrows, N. Y.

Aviculopecten princeps.

Paffo 1.

Ree Plates 1, 5, 6 and 81.

Fig. 7. An enlargement, to two diametoi*s, of the impression of tho hinge, showing the striations of the
ligamental area.

Hamilton group. Cazenorln^ N. Y.

Lyriopecten cymbalon.

Pago 47.
Fig. 8. A large, j)erfect left valve. The specimen shows a striated ligamental area.

Hamilton group. Prom a boulder near Ehnira, N. Y.

Pterinea (VertUxMnia) avis.

Page H>5.
Rg. 9. An imperfect right valve.

Chemung group. Near Elmira^ N. Y,
Fig. 11. A large, convex right valve. The figure should be I'estored at the cardinal angles to correspond
with fig. 13.

Chemung gi'oup. MansfieUU Pa,
Fig. 13. A nearly entire left valve. The b^'ssal sinus should be a little deeper than is represented.

Chemung group. Near Elmira* N. F.

Pterinopecten suborbicularis.

Pago 80.
See Plates 8 and 82.

Fig. 10. A view of a large and very perfect left valve. The radii increase by interstitial addition and not
by bifurcation as is represented in the figui*e.

Chemung group. Elm Valley, Alleghany Co., N. Y.

LiMOPTERA MACROPTERA.

Page 240.
See Plates 20, 27, 28, 29 and 92.

Fig. 14. A small right valve showing the form and surface ornamentation.

Hamilton group. PratVs Falls, Onondaga Co., N. Y,

Allocardium ai.ternatum, gen. et sp. nov.

Fig. 15. A view of the spec^'men enlarged to two diameters. The relations of this shell are not apparent.
It has the aspect of a bivalve shell in the characters of the rays and the cardinal auricnlation,
and somewhat resembles Hippagus and Trigoniluxa. With the present material it cannot
be satisfactorily arranged with any known genus of molluscs.
Hamilton group. Cayuga lake, N Y.

PLATE XXV— Conlinuca.

Leptodesma Orodes.

Pnflre JOe.
See Plate 90.

Figs. 6, 9. Two left valven. The apociiuen tig". 0, is redrawn on pi. 90, tif*". 8.

Pig. 10. A large left valve Honiewhat dirttort-iHi by presHure and njferred to the 8i>ecie.'» with doubt.

Chemung group. Near Smethjhyrt^ Pa.

Leitodesma mytiliforme.

J'age 235.
See Plate 91.

Figs. 7, 11. A light and left valve. Other illustrations of these apecimens are given on plate 91, tigs. 22
and 24, showing more clearly th(» siwritif. charwters.
Chemung gi'oup. Netir /SinefJij^ort, Pa.

Leptodesma Maolurii.

Vttge 228.
Se.> Plate 91.

Fig. 8. A right valve. See tig. 14, pi. 91, for anoth'M* tigure of this specimen.
Fig. 18. A left valve. Another figure of the si^ecinion is given on plate 91, fig. 13.

Chcniimg gi-oup. Near SimtJt2y>rtt Pa.

Leptodesma rude.

Vagc 221.
See Plato 91.

Fig. 12. The left valve described. See fig. 3, pi. 91.

Chemung gi-oup. Near SimthjnH, Pa.

Glyptodesma erectum.

Pago 153.
Stw Plates 11, 12, 13, 80 and 87.

Fig. 14. An internal mould of the upper portion of n left valve showing the lateral teeth and striated
ligamentiil area. The large srar 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 mustnilar impi^ession.
Hamilton group. Prom a boulder near Nichols, N. Y.
Fig. 15. An intenial cast of a right valve, showing the pallial line and imprint of a sti-ong posterior toolh.

Hamilton gi'oup. Otsego Co., N. Y.
Figs. 10, 17. A right and a left valve as preserved in a cherty limestone.

Hamilton group. Indiana.

Pal^opinna flabella.

Pago 240.

See Plate 87.

Fig. 18. The left valve described. See plate 87. fig. 4.

Oriskany .san<lstone. ^Srhoharie, N. Y.

PALiI':OPINNA RECURVA.

Pago 241.
Fig. 19. A view of a large imp<»rfect loft valve.

Tpper Helderberg group. Slnffttrd, Gene. tee Co., N. Y.

PLATE XXVI.

LlMOn^ERA CANCELLATA.

StMi Piatt* 92.

Fig. 1. The left valve of aspor.imen. Anothor ti^iin^ of thi.s valve is g-iveii on plaU* 92. fig. 8.

Fig. 2. The right side of the .'^ame. The i)allial line ami ninsmlar inipn^ssion are visible in each valve

l>iit are not repivsented in the tigiin».
Fig. 8. A cardinal view, showing at a. a', the tilling of the mnbonal a(ldiict<)r inuHiMdar attachment where

the pallial line terniinatea.
Fig. 4. An enlargement of the surface from the left valve.

Hamilton gi'oup. Falls of the. Ohio,

LlMOPIERA PAUPERATA.

Page -^43.

Fig. 5. View of an imp<.»rfect left vah-e. The radii on the wing and posterior side of the body are not
made suiHciently distinct.

Upper Helderberg group. Stafford, Grne^ec Co., N, Y.

LiMOPTERA MACROPTERA.

Pafre 246.
See Plates 24, 27, 28, 29 and 92.

Figs. 0, 7. Two loft valves showing the striations of the hinge area.

Hamilton gj'oup. McuUson Co., N. Y.
Fig. 8. The protile of a timall specimen which hju^ boen laterally conipre.«*sed, giving moi-e than the natural
rotimdity.

Hamilton group. Caznunmi, N. Y.
Fig. 9. A view of the left valve showing fewer and sti'onger radii than usual.

LlMOPPERA OBSOLETA?
Page 249.

See Plates 29 and 92.

l^g. 10. A view of the upper porti<m of th«^ right si<le of a specimen, showing the broatl striated ligamental
ai*ea of the left valve.

Hamilton group. Cazenovia, N. Y.

PLATE XXVII.

LiMOPTERA MACROPTERA.'

Paare 246.-
See Plates 24, 2G, 28. 29 and 92.

Fig. 1. The right valve of a small individual which i« veiy perfect in form.
Fig. 2. A small right valve.

Hamilton group. Summit, Schoharie Co., N, Y,
Fig. 3. A somewhat larger example.

Hamilton gfi*oup. Lebanon, Madison Co.„ N. Y.
Fig. 4. A left valve obliquely 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 *8 desciiption.

Hamilton group. Mailvton Co., N. Y.
Figs. 6, 7. Two views of a specimen which shows very distinctly the character of the surface.
Fig. 8. A canlinal view of a largo siM»cinien. The figure was intended to show the striated area of both
valves and a vertical depression undor the beaks as if fn)m a receding cartilage pit ; but
these features have imfortunately been lost in the lithography.
Fig. 9. A cardinal view of an individual distorted by lateral compression. The internal mould shows one
distinct point of niuscidnr attachment on the apex of each valve. See plate 28, fig. 4, for an
illustration of the right valve of this si>ecimen showing the umbonal muscular impression and
pallial line.

Hamilton group. Madison Co., N. Y,

PLATE XXVIII.

LiMOPTERA CUUVATA.

Pago 250.
Fig". 1. A large left valve Hhowing" the anterior curvature of the beak and the alternation of the ra<lii.
Fig. 2. An internal cast of a left valve hhowing tlie iuU'r-pailliiil area covei*e(l with small pustules which
wei-e apparently the points of attachni«?nt for unihonal muscles. The sperimen shows the pal-
lial line and muscular impression.
Fig. 3. The left valve of a large specimen, showuig the wing and some traces of the radii. The jH»st-hasal
margin is not sufficiently extende<l in the tigui'e
Hamilton group. Mad'iston Co.^ N. Y.

LiMOPTERA MACROPTERA.

Page 246.
See Plates 24, 26, 27. 20 and 02.

Fig. 4. The right side of a laterally compressed speoinuMi, represented on pi. 27, tig. 9, an<l pi. 20, fig. 2.

The umbonal scar is here shown in its trtie position.
Fig. 5. The left side of an unusually elongate si)erimen, due in part to the bi-eaking away of the margin

of the left valve U^ the margin of tlie i-ight valve.
Hamilton gi'oup. Maxlison Co,, N. F.

PLATE XXIX.

LiMOPTERA MACROPTERA.

Papc 216.
See Platea 24. 26. 27, 28 and 92.

Fig. 1. Th«» ripfht side of the specimen fig. 8, plate 2G.

Fig. 2. A view of the left side of the Hi>ecinien fig. 9. pi. 27, and fig. 4, i)l. 28.

Fig«. 3, 4. The pi-ofile and left \'iew8 of a much distorted Hpeeimen, showing the effects of compre^on.

Hamilton group. Madison Co., N. Y.

LiMOPTERA OBSOLETA.

Page 249.

See Plates 26 and 92.

Fig. 5. The left side of a specimen slightly imperfect on the anterior side, but showing the usual surface
characters.

Hamilton group. HamUton^ Maduton Co., N, Y.
Fig. 6. A left valve showing the sui*face characters and the striated ligamental area.

Hamilton group. Cayuga lake, N. Y.

PLATE XXX.
Mytilarca (Pletiiomytilus) arenosa.

Page 253.

See Plate 87.
FifT. I. A light valve of medium size.

Schoharie grit. Schoharie, N. Y,

Mytilarca (PLEXHOMrriLus) ponderosa.

Fig. 2. A right valve of a nmall 8pecimen.

Fig. 3. A left valve of a larger specimen, showing considerable extension of hinge-line.

Fig. 4. A left valve of medium size.

Upper Helderberg group. Clarcu^ HolhiP, Brie Co., N, Y.
Fig. 5. The under side of the rastral portion of a specimen showing the gi^eat breadth of the striated liga-
mental area. The margin of the shell is compressed and bent inwards on the anterior 8ide
showing the surface stria;.

Upper Helderberg gi-oup. Colmabus, Ohio.
Figs. 6, 7. The pi-ofile and left views of a large specimen entirely denuded of the test.

Uj^per Helderberg gi*oup. Columl/ua, Ohio.

PLATE XXXI.

Mytilarca (Plethomytili-s) oviformis.

Page '2r>5.
Sec Plate 87.

Fig". 1. A left valve of a yonng" shell of elong^ate form.

Hamilton g-nnip. Cayuga lake, X. Y.
Fig". 2. A left valve of the ordinary si/o, ahowing- tln» striated hinge-area and thn»e poati^rior teeth on the
wing which are not snffirieutly marked in the lithography.

Hamilton g-roup. Cayuga lake, X. Y,
Fig. 3. A right valve showing the strong ligamental area.
Fig. 4. A more elongate form with attennate beak.

Hamilton group. York Centre, TAvlngston Co,, N. Y.
Fig. 5. The anterior side of a compressed specimen preserving the valves in contat^t at the hinge, but
widely parted below.

Hamilton group. Geneseo, L\ringst^ii Co., N. Y.
Fig. 6. A large right valve ^^'idened below by compression. •

Hamilton group. Seneca lake, N. Y.
Fig. 7. A cast of a small elongate right valve. The beak has been removed to show the ligamental ai'^a ;
the thi'ee oblique lateral teeth are seen on the post-cai*dinal angle.

Hamilton group. Caiiand<iigiia laJce, N. Y.
Fig. 8. A large, broad right valve showing an unusually short hinge-area.

Hamilton gix^up. Bellona, Yat^ Co., N. Y,

GOSSELETTIA TRIQUETRA.
rage 266.

See Plate 87.

Fig. 9. A view of the left vaJve of a young individual of this species.

Fig. 10. The right side of a very ventricose specimen pi-eserving the natural form. Supposed to be the

original specimen.
Figs. 11, 13, 14. The Left, cardinal and ])Osterior views of a specimen pi-eserving 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 spe<'imen showing the anterior muscular impressions.

Hamilton group. Onondaga Co., N. Y.
Fig. 15. A partial cast of a left valve. The beak hius been removed \o show the strong anterior teeth and
anterior muscular impression.

Hamilton group. Faltonhavh, Schoharie Co., N. Y.
Fig. 16. A large left valve preserving the surface markings and the ligamental area.

Hamilton group. Fultonham, Schoharie Co., iV. Y.
Fig. 17. A large right valve.

Hamilton group. Madison Co., N. Y.

PLATE XXXIT.

Mytilarca umbonata.

I'agc 'if)?.
Figs. 1-4. The right, loft, anterior and posterior views of an individual preserving both valves. The
specimen has bocMi slightly coni))i*cssed laterally, giving an unnatural sharpness to the rostral
portions.

Chemung group. Ithaca^ N. Y,
Figs. 5, 6, 7. The posterior, anterior and right sides of a specimen. Fig. 6 shows what appears to be the
pallial line terminating near the beak.

Chemung group. Mam*tfi^ldy Pa.

Mytilarca Chemunoensis.

Fig. 8. A small right valve showing the striated ligamtMital ai*ea.

Chemung group. PhUlpslturg, Alh(jhany Co., iV. F.
Fig. 9. A left valve with the beak partially broken away showing the small cardinal t«eth.

Chemung group. liockvtlle^ Alleghany C'o., iV. T.
Fig. 10. The interior of a left valve fi-om an impression in the shale, showing the striated hinge-area.

Chemung gi*oup. Rockville^ xY. Y.
Fig. 11. A small. bi*oati right valve.

Fig. 13. An impi*e.ssion of the margin of a large left valve, showing the form of the hinge and its breadth as
extending within the margin of the .<hell.

Chemung group. RorkvWt, y. Y.
Fig. 14. A very narrow and erect left valve showing also the striations of the hinge.

Chemung gi*oup. East Rnndvlph^ N. Y.

Mytilarca reoularis.

Pagfc *2«>(>.
Fig. 12. A left valve showing the bi'oa<l rounded form an<l straight ei-ert beak.

Chemung gi*oup. Leon Ctntre, Cattnraugtis Co., X. Y.

Mytilarca carixata.

I'lXfi^c 2.V.).
See Plate 33.
Fig. ir>. A small left valv(j.

Chemung group. Near Elvdra^ X, Y.
Fig. If). A small right valve showing the form of the shell.

Chemung group. Favtoryv'iUe^ Tioga Vo.^ N, Y.
Figs. 17, 18. Two opposite valves .showing some variation in the form of the shell.

("heinung group. Near Elmira, X. Y,
Fig. 19. An internal (!aHt preserving impressions of the cardinal and lateral teeth and showing the striateil
ligamentnl aii^a.

Chemung group. Neur Ehn'ira, N. Y

Mytilarca attenuata.

Pajre 260.
Fig. 20. A left valve showing the eivct subearinate form and attenuate beak.

Chemung group. Kimira, X. Y.

Kyssopteria radiata.

Pajre iV).».

See Plate 80.

Fig. 21, A right valve imperfet't at the beak, but showing the surface chamctei-s an<l angular anterior side.

Fig. 22. An imp««rfe«'t left valve which shows the general outline. The radii are not so distinctly duplicate

as on thi» otlnM* spivimen.

Ch«Munng gn^up. Mansjitld, Tioga Co., Pa.

PLATE XXXIII-ContinutMl.

Mytilauca CAKINATA.

Page 2ft9.'.

See Plate 32.

Fig. 8. An'enlargeineiit of the cardinal ]>orti(>n of tig. 19, plate 32. aa obtained fi-om an impreaaion, showing
more clearly the hinge cliaractei-s.

Chemung group. Ntar Elmlra^ N. Y.

MODIOLA (MyTILOPS) PRiECEDENS.

Page 2C7.
Pig. 9. A small left valve deniuletl of the strijp.

Figs. 10, 11. Cai-dinal views of two BperimenK with the valves partly openetl.
Fig. 12. A small right valve.

Fig. 13. A left valve of medium size, preserving the surfmre striw.
Fig. 14. An elongate right valve, showing the aurfiu-e (!hara<;tei*s.

Chemung group. Oieari, N. Y.
Pig. 15. A inght valve, pi*obably of this species but showing no surfwre striie.

Chemung group, ^methport. Pa.
Fig. 10. ITie cardinal view of a specimen, with both valves stnmgly striate.
Fig. 17. A large broad si>etrimen pi-eserving the 8urfa<'e markings.
Fig. 18. The anterior view of an example showing nearly equal c<mvexity of Iwth valves.

Chemung gix)up. Olean^ N, Y.

Mytilarca simplex.

Page 261.

Fig. 19. A large right valve, showing varices of growth.

Fig. 21. A smaller left valve. The l)eak should Iw <lirerted slightly to the left to give the proi>er expres-
sion to the figure.

Chemung gi*oup. Smet-hpiyi'U Pa.

Mytilarca gibbosa.

Page ti62.

See Plate 87.

Pig. 20. The left valve des<'ril)ed. Another figure is given on plate 87, fig. 7.

Chemung group. Napolit Cattaraugus Co., N. Y.

Mytilarca lata.

Paire 262.
Fig. 22. A right valve showing the bi*oad form of the shell.

Chemung group. Randolph, N. Y.

Modiola (Mytilops) metella.

Page 2C8.
See Plate 87.

Figs. 23, 24. Two right valves showing the general form of the shell. A figui*e of another specimen is given
on plat^ 87 in the same posititm as the tigui*es of M. pnBctdena on the present plate for a better
comparison.

Chemung gmuj). CJtatttauqtia Co., N, Y.

PLATE LXXXt-ConUtmed.

AVICULOPECTBN TENUIS,

Page 30.
See Plate 7.

Fiff. 6. The left valve represented on pi. 7, fig. 28, redrawn to show the true form and ornamentation,
with the pallial line and muscular impression.

Chemung group. Near Salamanca, N. t.

AVICULOPECTEN INSIQNIS.
Page 34.

See Plates 1 and 3.

Fiff. 7. A left valve preservings the form and proportions in greater perfection than shown on the previous
plates. Hamilton group. StaffonU Genesee Co., N, T,

AVIOULOPEOTEK BELLUS.
Page 85.

See Plate 2.
Fig. 8.. A right valve, X 2.

AVICULOPECTEN DUPLICATU8.

Page 17.
See Phite 7.

Fig. H. A hid valve sho^nng the coarse radii on the pallial margin.

Chemung group. Maiisfidd, Pa,
Fig. 10. An entire right valve.

Cliemung gi-oup. Manafield^ Pa,

AviCULOPECTEN RUOJE8TRIATUS.

Page 15.
See Plate 7.

Fig, 11. A right valve preHerving the surface characters with considerable perfection.

C*heinung group. Rot-kmlle, N. Y.
Fig. 12, f^veral of the ratfii, of the preceding specimen, enlarged two diameters to show the changes in
Htirfa(;e ornamentation from the heak to the base.

AviCULOPECTEN PRINCEP8.

Page 1.

See Plates 1, 5, 6 and 24.

y,f(, IZ. A right valve showing the pallial line and muscular impression.

Hamilton group. LudXovmUe, N, Y.
F^g 1 1' A it|ie«dmen with a portion of the left valve i*emove<l showing the interior of the right valve and
the difference in size between the right and left valves.

Hamilton group. MvtUmviUe, Ontario Co., N, Y.
K,g- I'f* A left valve as pi-eserve*! in limestone.

Hamilton group. Delaware, Ohio.
F.g K» A Hif^:im*;n preserved in a soft shale showing strong regular concentric strife.

Hamilton group. Livingston Co., N, Y.
F./ 17. An individual vertically imbedded in the shales showing the effects of compression and distortion.

Hamilton group. N. F.

LtBIOPECTES oaBIODLAHIS.

Pwo a.

See Plate 4.
, Tig. 3, A specimen with lie upjier perlion of thi> Iiift vnlve iijiniived, nhowiiig the PKlorior imrreHBi(>n of
the right vttlve and the comparative aiie of Ihi' two viUvfls,
Hamilton gron]). Oznartibiiffua lake, N. T.

PtERINOPBOTBS 8UBORBICDLARI8.

See Plates S and 24.
Kg. i. i right vnlve of thia species ahowing' thp deep byaaul wi
Chemung group. J(an4lfoW. fa-

XiXSIOFSfTTES INTBKRADUTUS.
PAgeU.
8eo Plat* a.
tig. S. A Inriffl It-ft valie showiug' the fiurfiLi:e oi'u.i mentation and the lig-aim-iitaJ a
H ami lion gi-oup. Schoharie Cb.. N. T.

Ltkiofeothn Piuamum.

I'affS N.
See PIrtte 1(1.
Fig. 6, \ rl^-ht valve of this Species.

Ohemang group. I'^anJeliv. Selamire Ci>., jV. Y.

pTEIilKOPBCTEN UNUOSUS.

flev 79.
See Plalc 3.
Pig. 7, A left valvB with oomparatively few radii, anil (he alrimg I'harDclcrlttic raincentrir iindnlnliiins.
namSlton gmiip. Bethaay, N. Y.

PTERltfOPECTEN KEFLEXU8.
PagaU.
V\g. 8. A view of the inlei-ior of a left valve.

Comiferoua liraealone. Ohio falls.

PnCBmOPBCTEX FTLfnXTCS.

Page 47.

S*» PUte 17.

Fi^. d. A Ap^fnm^n ^ht^vin^r tfa^ Lntmi jr ijf dk# right Tilre And praerving tlie pallial margin of the left

T»Ive. Jbumlzt'jn grc ap. Oaowifay croei:, JT. F.
Fig. 10. ka ^nlarmiMTit. v^ rhr*« diAm«ii?n» of a portkm of th« flmface of tiie ^lediiMn illustrated on plate
IT. fg. 22.

iUmfl^x: g7«:ap. #Vni m homUtr. Pirn VmlUf, jST. F.

PrCRCrOFECTES DISPAXDUS.

Fig. 11. A rigfi: ralvi? of difi» sj
Fig. 13. A left valve.

Fig. 13. Tbe imperfect left valve .lea«rrtbe*.L siowiag tb<e irkanKteraoc nodose radii.

Ooniiiertutf linMffU'ae. t'^k'/mU^

PtKKINOPBCTKX CMaaCX^STATCS.

See Flase *.

Fig. 14. The »i»e^'imen i^lale !\ Kg. -k n^lrawn ami re«rti*r>Nl in outline k^ sliow tlie entire form and details
of surftwt* vhara*,*ler*.

Oheniung gnmp. .Vcur Attf^iU-a^ S. Y.

l^rBKlNOPECTKX ERECTUS.
• P«^77.

Fig. I ft. A »j»eoiuM>u with the up|»er ix>Hion of the left valve broken away, showing the interior of the

right valve.
Fig. 16. A loft valve of nuHlium suze.
Fig. 17. A largt* left valve,

(^honuuig gnn»p. 7Mci<ti, y. Y,

I^KRINOPEOTEN (A VICULOFEOTBN ?) 8TRICTU8.

Page 74.
See Plate 34.

Fig. lA. A left valve, associated with the right valve illustrated on plate 34.

Chemung group. iVear Elmlraj N. Y.

I^ERINEA (VeRTUMNIA) RBPROBA.

Page 106.
Fig. 19. A left valve.

Fig. *20. The convex right valve of a larger individual than the preceding.

rhemung group. Ithaea, N, Y.

AVXOULOPEOTEN (PtERINOPECTBN) INVALIDUS.

Pago SI.
See Plate 1.
Fig. 21 • '^^^^ 1<'^*^ valve, fig. 18, plate 1, <lrawn of natural size, showing the trae form and proportions.

Marrellus shale. Cherry Valley, N. Y.

PLATE LXXXt-ConUtmed.

AviCULOPECTBN TENUIS,

Page 39.
See Plate 7.

Fig, 6. The left valve represented on pi. 7, fig. 28, redrawn to show the true form and ornamentation,
with the pallial line and muscular impresMon.

Chemung (froup. Near Salamanca, N. t,

AVICULOPECTEN INSIQNIS.
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, Chneaee Co,, N, T,

AVIOULOPEOTEK BELLUS.
Page 35.

See Plate 2.
Fig. 8.. A right valve, X 2.

AVICULOPECTEN DUPUCATU8.

Page 17.
See Plate 7.

Fig. 9. A left valve showing the coarse radii on the pallial margin.

Chemung group. Afaiisfieldf Pa.
Fig. 10. An entii-e right valve.

Chemung gi'oup. Mansfield, Pa,

AviCULOPECTEN RUO-E8TRIATU8.

Page 15.
See Plate 7.

Fig. 11. A right valve pi^eserving the Bui*facc characters with considerable perfection.

Chemung group. Hockville, N. Y,
Fig. 12. Several of the ratlii, of the precedinK" specimen, enlarged two diameters to show the changes in
surface ornamentation from the beak to the base.

AviCULOPECTEN PRINCEP8.

Page 1.

See Plates 1, 5, 6 and 24.

Fig. 13. A right valve showing the pallial line and muscular impression.

Hamilton group. LudlowviUe, N, Y.
Fig. 14. A specimen with a portion of the left valve removed showing the interior of the right valve and
the difference in size between the right and left valves.

Hamilton group. Muttonville, Ontario Co., N, Y.
Fig. 15. A left valve as pi^eserved in limestone.

Hamilton group. Delaware, Ohio.
Fig. 16. A specimen preserved in a soft shale showing strong regular concentric stiHse.

Hamilton group. LwingaUm Co., N. Y.
Fig. 17. An individual vertically imbedded in the shales showing the effects of compression and distortion.

Hamilton group. N. Y,

PLATE LXXXn— Continaed.

PtEBINOPECTEN FILrrBXTUS.

Page 67.

See Plate 17.

Fig*. 9. A Bpecimeii showing' the ititenor of the right valve and presernng the pallial margin of the left

valve. Hamilton gi*oui). Onondoffa creek, N. T.
Fig. 10. An enlargement, to three diameters, of a i>ortion of the surface of the specimen illustrated on plate
17, fig. 22.

Hamilton group. Fkvm a boulder, Pine Valley, N* Y^

Pterinopecten dispandus.

Page 76.
Fig. 11. A right valve of this species.

Fig. 12. A left valve.

Chemung group. Man^JUHd, Pa.

PtERINOPECTBN NOD08U8.
Pa«e6U.
Fig. 13. The imperfect left valve described, shovring the characteristic nodose radii.

Comiferous limestone. Ohio falls.

PtERINOPECTEN CRENICCN3TATU8.

Page 78.
See Plate 8.
Fig. 14. The specimen plate 8, fig. 4, i*edrawn and restored in outline to show the entire form and details
of surface characters.

Chemung group. Near Angelica^ N. Y.

Pterinopecten erectus.

Page n.
Fig. 15. A specimen with the upper portion of the left valve broken away, showing the interior of the

right valve.
Fig. 16. A left valve of medium size.
Fig. 17. A large left valve.

Chemung group. Ithm^i, N. Y.

Pterinopecten (Aviculopeoten?) strictus.

Page 74.
See Plate 24.
Fig. 18. A left valve, associated with the right valve illustrateil on plate 24.

Chemung group. Near Elmira, N. Y.

Ptebinea (Vertumnia) reproba.

Page 106.
Fig. 19. A left valve.

Fig. 20. The convex right valve of a larger individual than the preceding.

Chemung group. Ithaca, N. Y.

Aviculopeoten (I^erinopeoten) invalidus.

Pago 31.
See Plate 1.
Fig. 21. The left valve, fig. 18, plate 1, drawn of natiu'al size, showing the true form and proportions.

Marcellus shale. Cherry Valley, N, Y.

IM-ATK LXXXIII— Continued.

PTERINOrECTEN EXFOLIATUS.

Pago tfl.

Scte Plate 1.

Fig. 6. A left valve as obtained fi-oni an impression of the matrix, showing* the fonn and surface characters.
Fig. 7. A large imperfect left valve with the test almost wholly exfoliate<l and pi^esenting a strong contrast
with the preceding.

Limestone of Mai*celhis shale. Genesee Co., N. Y.

CRENiPEcrEN Leon.

V&gQ S8.

S*'e Plate 9.

Fig. ^ 8. The left valve descnbed showing the hinge charactei-s and form of the valve.

Chemung group, /^^m, (Jattaraugus Co., N. Y.

CrENIPECTEN LIRATU8.
Page ^.

See Plate 9.

Fig. 9. A left valve showing the form and size of the eai*a given in correction of tig. 24, plate 9.

Chemung group. Omtincattgo, Cattarau{/tis Co., N. Y,

CrEN I PECTEN IM POLIT US.
Pago 83.

See Plate 9.
Fig. 10. A small left valve.

C^hemung group. Ohan, iV*^. 1".

1^'ERINEA FLABELLA.

l»ago U3.
See Plates 14 an<l Kk

Fig. 11. A large left valve showing but three strong radii.

Chemung group. LawrenretUle, Tioija Co., Pa.
Fig. 12. The internal mould of a left valve, showing the ligamental area, lateral and cardinal teeth, pallial
line and both muscular impi^essions.

Hamilton group. Schoharie Co., N. Y.

PtERINEA PINGUIS.

Page 9-2.

See Plate 15.

Pig. 13. A left valve showing the form and proportions ; redrawn from the specimen of fig. 2, plate 15.

Upper Helderberg gi*oup. Near Colninl)ii8, Ohio.

PtERINEA GRANDI8.

Page 91.
Fig. 14. A large left valve impei-fect on the anterior end.

Upper Heldei'berg group. Lexington, Scott Co., hid.

PLATE LXXXIV— Continued.

ACTINOPTERIA AURICULATA.
Pago 121.
Fig". 15. The left valve deacril)0(i showing' thf» larg'e anterior ear.

Chemung group. TjawreiweviUe, Tioga Co., Pa.

ACTINOPTERIA BOYDI.
Pago 113.

See Plate 19.
Fig". 16. The left valve of the specimen figs. 20, 28, 20, plat€ 19, redrawn to show the pallial line and
muscular impressions.

Hamilton group. CazetKma, N. Y.
Fig. 17. A small right valve showing the hinge characters, pallial line and muscular iinpi'essiou. This
figure is the natural size of the specimen represented in figure 12, plate 19.
Hamilton gix)up. Hamilton, Madison Co., N, T,

AcTiNOirrEiuA theta.

Page 125.
Figs. 18, 19. The right and left valves of the specimen described.

Chemung group. Ithaca, N. Y.

ECTENODESMA BIKOSTRATUM.

Page 24'i.

See Plate 23.
Fig. 20. The left valve i-epresenteil on plate 23, fig. 30, redrawn to show the extent of the wings.

Chemung group. FravkUn, Delaware Co., N, Y.

PtERINEA C1IEMUNGENSI8.
Pago 98.

See Plate 16.
Fig. 21. A large left valve of this species showing the form of the shell and the interrupted rays with the
fine concentric striie of the surface.

Chemung group. iYlear Bath, N. Y.

Pterinea INTERSTRIALIS.

Pago 96
Fig. 22. An imperfect left valve.

Chemung group. Chemung Narrows, N. Y.

Pterinea consimilis.

Pago 100.
See Plate 16.
Fig. 23. A left valve showing the ligamental area, cAixlinal and lateral teeth, pallial line and muscular
impression. Rome i>ortions of the test are remaining on the lower half of the valve.
Chemung group. T^ioga Co., N. Y.

Pterinea (Vertumnia) reversa.

Page 104.
See Plate 24.
Fig. 24. The specimen i-epresented on i>late 24, fig. 6, redrawn te show the absence of strong rays on the
wing.

Chemung group. Elmira, N. Y.

PLATK LXXXV-Continuo«l.

Ptychoi*tekia Bekcfieri.

Pago U3.
Kig. 21. An entii'O l«ft valve showiiifr its g-ihbous tin«l aivnate form.
Fig". 22. A ri|rht valve of this spe<nes.

Ohemung^ giH)up. JVan'm., Pa.

Ptyciiopteria lata.

Fig-. 23. An entire left valve.
Fig". 24. A larger left valve.

Fig. 25. A inglit valve showing' its <r()nij>anitively strong alar fold.

Chemung gniuj). Warren, Pn.

Ptvchopteuia alata.

VufCQ i:J9.
StM» Plate 23.
Fig. 2G. The jiosterior half of a left valv«». showing the Rubangiilar iHwterior «lo]w».

Chemung group. Snlamawa, N. T,

Ftychoptkkia Kucrate.

PufTO 133.
See Plate 23.
Fig. 27. A left valve of this specie.**.

Fig. 28. A small left valve.

CTiemung group. Paimitia^ N, Y.

PrYCiioprERiA Galene.

l*a>re 142.
Fig. 29. A left valve flattened l»y pivssure.

Fig. 30. A smaller left valve pn'serving tho normal proportions of the si>ecies.

Fig. 31, The right valve of a 8j)eciinen piH»s«u*ving l)oth valves.

Chemung group. Warreiu Pci.

Ptyciiopteria Tiiai.ia.

Pn^re US.
Fig. 32. A small right valve.

Fig. 33. A medium sized left valve showing the short gibbous form of the shell.

Chemung group. Allrylmny iSprim/s, JVarren Co., Pa.

Ptyciiopteria trioonalis.

PaffO 140.
Fig. 34, A small left valve showing the form ami oharaetei's of the spiM'ii^s.
Fig. 35. A large imperfect left valve.

Chemung group. Panama^ N. Y.

Ptyciiopteria Vanuxemi.

Pago 151.
Fig. 30. A portion of a large li?ft valve, showing the peculiar form of the body and the surface eharacters.

Chemung gi*oup. Warren, Pa.

Ptychopteria lobata.

Pairo 150.
Fig. 37. A left valve showing the shoH form of the valve and the strong alar plication.

Chemung group. Warrt n. Pa.

PtYCIK )PrERIA PERIJVTA.
Pajre 147.
Fig. 38. A right valve of this speries.

Fig. 39. A left valve showing the form and surface markings.

Chemung group. Warren, Pa.

PLATE LXXXVI.
Glyi*todesma erectum.

, rage 153.
Soe Plates 11, 12, 13, 2.') and 87.

Fig. 1. A left valve of a small individual.

Hamilton groiip. Fabifta, Onondaga O)., JV". Y.
Fig". 2. The right valve, as seen lying within the left, showing it.s form and comparative size.

Hamilton gi*oup. Cayuga lake, N. Y.
Fig. 3. The hinge of a specimen, showing the striate*! ligamental area and strong cardinal folds.

Hamilton group. Delphi, Onondaga. Co., iV. Y.
Fig. 4. A small left valve with small anterior wing and very large postenor wing, also showing one of the
oblique lateral teeth.

Hamilton group. Cayuga lake, N. Y.
Fig. 5. The anterior i)rofile view of a \^ry perfect sj)eciinen ix'taining the test, showing the comparative
convexity of the valves.

Hamilton group. PratVtt falls, Oiumdagu Co., N, Y.
Pig. 6. The left valve tig. 8, j)late 11. redrawn to show the ligamental area, lateral teeth and muscular
impression. The tubular markings ai'ound the margin are the remains of the excavations
made by boring sponges.

Hamilton group. Cazenopia, iV^ Y,
Fig. 7. A large i-ight valve, sh{>wing the lignnienttil are;i, jmllial line, mus^cular impression and umbonal pits.

Hamilton gi*oup. (rilbcrt^KVille, Oistgu Co., X. Y.
Fig. 8. A left valve pi*esenting the same int(»nial eharaotei's as the preceding, together with two strong
lateral teeth.

Hamilton group. Albany Co., iV. Y.

Glyptodesma occh^entale.

VngQ 157.
See Plate 15.

Fig. 9. The specimen of lig. 12, plate 15, redrawn to show the I'lHjet form of the body and extent of the
posterior cai'dinal expansion.

Upper Helderberg group. Falls of the Ohio.

PLATE LXXXVIl— Continued.

MyxrLARCA FIBRISTRIATA.
PaRe264.

See Plato 33.

Fig". 6. The left valve tig*. 6, plate 33, redrawn to show the true form of the anterior side. ITiis species is
the only radiate form of the g^nus yet described and more perfect material may show
charactei*s which would exclude it from Mytilarca.
Yellow sandstone. Burlington^ Iowa,

Mytiij^rca GIBBOSA.

Page 262.

See Plate 33.

Fig. 7. The left valve fig. 20, plate 33, reilrawn to show mora clearly the entire form of the valve.

Chemung group. NapoH, CattaraxiguslOo., N. Y,

Mytilarca (Plethomytilus) oviformis.

Pago 255.
See Plate 31.

Fig. 8. The upper portion of a right valve showing the oblique posterior teeth of the hinge.

Hamilton group. ForAr, Livingston Co., N, T,

MoDioLA (Mytilops) METELLA.

Page 268.

See Plate 33.

Fig. 9. A right valve showing the form and proportions of the shell.

Chemung group. Warren, Pa.

Mytilarca (Plethomytilus) arenacea.

Page 253.

See Plate 30.
Fig. 10. A left valve.

Schoharie grit. Schoharie, N, 'Y.

Mytilarca occidentalls.

Page 263.
See Plate 33.

Fig. 11. The left valve fig. 5, 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, Iowa.

GOSSELETTIA TKIQUETRA.
Page 265.

See Plate 31.
Fig. 12. A large right valve of elongate form.

Hamilton group. Fidtonham, Schoharie Co., N. Y.

Mytilarca (Plethomytilus) Knappi.

Paff0 256.

Fig. 13. The right valve described, showing the form of the shell and the striated ligamental area.

Hamilton group. Skaneateles lake, N. Y.

PLATE LXXXVIII-Continued.

Lkioptkria Sayf.

PuKO 162.
Fig". If). An ini]x»rf(»ct U*ft valv<* preserving^ very tine <'()nceutri<r linos.

Hamilton groiq). Norton. << fjindhtg, Vayuga laMc, A. 1'.
Vi^. lo. The left valve of a speeinien preserving- 1m th valves, showing" the extent of the wing- and g-eneral
form of the shell.

Hamilton gronp. fAvnujatoii (\>,, N. Y.
I'ig:. 17. The right valve of a large specimen with the valves partially openiMl.

Hamilton g-rou]). BdUma, iV. 1".
Fig-. 18 A left valve presorvingp the auricle and wing- n»»arly entire. The hody of the .shell has l)een subjected
to pi*essure and <list<n'lion in the s()ft shah* and does not i*epreaent the true fonu and obliquity.

Hamilton group. BtUoitu, xV. Y.
Fig", li). An imperfect left valve as pi*eserve<l in a coai-se g-rit.

Hamilton grouj). Tjeonardsvillt, MndUon Co., N. Y.
Fig. 20. A small left valve of considerable gibbosity.

Hamilton g-i*oup. Srhofinrh' Co., y. Y.

Leiopteria Greeni.

Page 160.
See Plate 20.
Fig-. 21. A larg-e left valve. The lig-ju*e is ivstoi*ed on the beak and antcinor side.

Hamilton group. Belhma, Yates Co., N. Y.
Fig. 22. An imp«»rfect right valve.

Hamilton gn)up. Cnnondaigua lake, N. Y.

LEIOPTERfA BlGSBYI.

Pa^e 1(15.
See Plate 20.
Fig. 28. A small right valve refeiTed to this species.

Hamilton group. N, Y.

Leiopi'eria Leai.

Page 1(».
Fig. 24. A small left valve.

Fig. 25. A larger imperfect left valve associated with the [)ii»ceding.

Hamilton group, i^chohane Co.y X, Y.

Leiopteria Mitohelli.

Pago 166.

See Plat4i 20.

Fig. 26. A larj.e imi>erfe.ct left valve as obtained from the impn'S.sion of the exterior of th<» valve in the

matrix.

Hamilton group, f^ichoharle Co., X. Y.

Leioiteria Rafinesquii.

Page 161.
See Plates 1') an<l 20.
Fig. 27. A nearly entire left valve showing the form and the strong roncentri*' undiUations. ,

Hamilton grouj>. BtlUma, N. Y.
Fig. 28. A right valve referred to this sj>ecies. The specimen is imj»erfect at the l>eak and extremity of
the wing.

Hamilton group. Ltoiiard^mlle, N. Y.

Leioiteria linuuiformis.

Pago 173.
Fig. 29. A left valve, denuded t)f the test, showing the general f{»rm with tin* pallial line and muscular
im]»ression.

Chemung group. North of Binghamton, N. Y.

PLATE I.XXXIX— Contiiiuctl. =

LkPTODESMA MoilTONI.

Pnpe IJW.
S«M' Plato 21.

Fig". 9. The specrinien tig". 31, plate 21, ifxlrawu to show tho form of tho Iwxly and size of the wing'. •

(^heniung" grouji. Portriiie^ Citttaiwcgwi Co,, N. Y.
Fig". 10. The i-ig-ht valve fig". 32, plate 21, i-edrawn to show the pi'oper form and charactei's of this valve.

Cheminig group. Portviik, N. Y.
Fig. 11. A (tanlinal view of a specimen, preserving the valves partially ojien and showing* their comparative
size. Chemung g-itnip. TAWe Gniesee, N. Y,

Leptodesma Billingsi.

Page 192.
Fig". 12. A large left valve.

Chemung group. Panama, N. Y. •

Fig. 13. A right valve agreeing in form and proportions with this species, l»ut ivferi*ed with some doubt
on account of the geological position.

Chemung group. Near Ehiiira, N. Y.
Fig. 14. An imperfect left valve of somewhat different form.

Chemung group. Panama, N. Y.
Fig. 1."). A small left valve fi*om the same horizon as the specimen tig. 13.

IjEPTODESMA LEPIDUM.

VugQ 19ft.

See Plate 21.

Fig. 16. A left valve .showing the form and surface mnirkings.

Chemung grouj). T'toyn Co., Pa.

Leptodesma Agassizi.

Page IK-2.

Figs. 17, IS. Two left valves showing the characteristic form of this species.
Fig. 19. A sum 11 right valve.

Chemung grouj). Near Kiviira, N. F.

Leptodesma Stephani.

Page 194
Fig. 20. A right valve.

Figs. 21, 22. Two left valves .showing the usual charactei*s of the species.

Cliemung group. Bradford, Pa.

Leptodesma disparile.

Pago 18G.
See Plate 2.5.

Fig. 23. A right valve showing the form and oniament^tion.
Fig. 24. A small left valve preserving the spiniforni proce.ss.

ChlMuung group. McKean Co., Pa.

^ PLATE

^^^^^^^^^^ 6 — IJmbonala.

LrPTODKkMA MEtK>N.

Hb«

1 ;(. 'Iliri?*- l"ft nilvfl VMrjiiitt »iimi-wh»il in form ivml Hiz--.

FiB-

4. A right valvi^ uf (his spMJcs.

Cheiiiiin)^ )tr<>»\\. La.v>rtnan'Ulr, T'uiga Co.. Pa.

Lkptodessia Mestok.

p>K3ae.

am- plutx :ai.

1*.

6. A kfl vulva at the iisiwl form.

LbIT^IiBSMA C-AIIMUS.

P»»o SOI.

^H F'C.

11 A Wn lalio cif a Kpoejmmi prcBcrviiitt '">'•' valves |n»rlly np'Tii.

Chpitiimir KToup. fHiailliJUId, Brwifivi Co., n.

^^* ««.

7, A \iiiyv left vilvp.

Chi-inunp e''""V- Wrabn. C.'.. JV. 1'.

Lr-iTonKsMA Orodks.

rngu Wfl,

■

»ViR Plato 2S.

1 r.,.

H. Tim i.|«-din(tu fig. B, pint* 2S. ™li-uwn tu -.hiw IVi" ti'ii.. romi of 11.^ IhhIj' «j.,| win^-.

Leptodesma UMBONATDM.

FlKWlBM.

Kw Plal« 23.

^^ 1^.

9. 'riiM uiiMiiliiiBii tiff. 13. |il«'"' ^^- ri'Jrawii tn sliuw il» i'rii|"T fi'nii nnil pi'nporliimi".

Cht-mnuB uri-oiiii. T:Fir»ly .Mi'f '-rir.k. Cliaiilanqiui f."o.. jV. i",

^^^^v

LbPTODESMA nMllONATCM, Vlir. rtEPBRSflUM.

PlKK" lO".

Ri-i. l'l.,t« 22.

^■Pi.r.

ID, Thf .|.e«in«!i. Ii(t. M, plnl« IB. rBatmwii nii.l iTwU.ivd in rtiitUnc.

^H '

Ch'-rnimK kt-iuj.. Hapoll Cr^itn, nall«i-anffus Co.. N. 7,

Lbitoubsma Cbeon.

PiWeSM.

^^mi^

U, 13. Two left v»lv«H nhnwln^ lOigUt iliRt-nniw* iti fdriti nnil Piii-riiiv iiiui-kiugB.

^^B-Vlir^

18. A rl^ht valvn.

Chemung gwi up. lAimr*nm<Ule. IH-yn (h.. {"a

LrPTODESMA IjOXIAK.

^V <"'''

U. A i'^rt v«lv*i of thi- t.p.-H«n.

Oh"iHiiri(- ifT'iup. lMiamifrKill4t, n>ffo. (ju., f,^

Lei-todesma Demos.

Phiu :-m.

^^^ Rp^

15, Ifi. A rltfhl j«ia Ifft v»Uc shnwitiR- IIil^ l.ki.kI rnriii (if Uw nhdl.

Clieiiimi).* ifrfiii|i. Lawrrntmlllr. T^iapt Co.. Pa.

c — Rostrata.

LKlT01>BMMi EXTBSUATUM.

P«go9<".

. The spei-i
1, A rig'hl V

len lifT, 2a. phtt.' 22. rpclniwu to show th(! uiiMre
Ive with thp t.'f^t ii>mnveil shnwinfj Ihf imllinl 1i
Chetiiiinif group. Mansfiit'l. TiognCo.. Pa,

PLATE Xri~Coiitiiiuo<l.

Leitodesma Maclitrii.

Pai2:c 'iit<.
See Plato 25.

Fig". 13. A larg'e left valvo of this sixtjoh. Thi.*^ H«rmM? is g-iviMi in corivrtion of tij^. 18, plate 25.

Chemung' group. Near SmrtfiiH)rt, Pa,
Fig. 14. The nght valve tig-urrd on plate 25, tig. 8, ivdrawn to roircct the outline.

Cheuiung group. iN'ear Sinetftjuni, Pa.

Lefix)desma quaduatum.

rage 233.
Fig. 15. The left valve {le.»*<*rilHMl.

Chemung gi*(>up. ^ttuOen Co., N. Y.

LePTODESMA PROPINQUUM.
:Pago 231.
Fig. It). A nearly enti^*e left valve, showing the form an<l charnctei-K of th<? Bjxicies.

Chemung grouj). Manafitldy Pc-
Fig. 17. A similar rig-ht valve.

Chemung grouj). MatisJU:l(i, Pfi.

Lei*todesma Piiaon.

Pago 230
Fig". 18. A h»ft valve of this speeies.

Chemung gi*oup. MaiusJitUf, Pa.

LePTODESMA LiClIAS.

Pngo '232.

See Plate 21.
Fig. 19. A small left valve.

(^hemung g^roup. iSteuf>t7i Co., N. Y.

Fig. 20. The left valve figure<l on plat<* 21, tig. 37, re<lra\vn to corrert the outline.

Chemung group. PhUipahurff, N. Y.

f — Mytiloidea.
Leitodesma acutirostrum.

Pugo '234.

Fig. 21. The left valve descrilM^d, showing the form of the Ixuly and the acute anterior end.

Chemung group. 'Wari'en, Pa.

LeITODESMA MYTILIFORME.

Page 2X}.

Soe Plat<» 2.').

Fig. 22. The right valve tiguit'd on jilate 25, tig. 7. re<lrawn to correct the outline an<l the form of the body.
Fig. 23. A small left valve.

Fig. 24. A view of h»ft valve given in cori*oction of fig. 1 1, plat«' 2.").
Fig. 25. Two left valves as preserved on the surfac*' of a piece of sandstone.

Chemung gronj). Iloaxlfrmn Olean to fi!m<t?iport. Pa.

PLATE XCII.

LiMOPTEKA CANCELLATA.

Vage 241.

S<*e PlaU» 26.

Pip*. I, 2. Two small left valves differing* in the frequency of the radii.,'

Hamilton gr(>up. Fails of the Ohio.
Fig". 3. The left side of the orig'inal apeciin<»n, r»>drawn t^) show the ••estoretl outline, the pallial line and
tnu^'ular impression.

Hamilton g^roup. Falls of the Oh'io.

LlMOri'ERA MACROPTEUA.

Page 246.
See Plates 24, 26. 27, 28 and 29.

Kijf. 4. A small gibbous left valve showing" numerous tine radii.

Hamilton group. Delphi, Onondaga Co., N. Y.
Fig>*. .'), 6. The rig-ht and jn-otilc views of a small specimen showing the form and <'onvexity of th(» shell.

Hamilton g-rouj). PratVn falls, Omtndaga Co,, N. Y.
Fig. 7. An outline of a largt; right valve.

Hamilton gi*oup. tSclwhane Co , N. Y.
Fig. S. A left valve preserving* very marked surface charactei*s.

Hamilton grouj>. DelphU N. Y.
Fig. 9. A rig'ht valve showing the marke<l radii on the undwtial region an<l their gra<lual obsolescence
towanl the margin of the valve. The hinge preserve's the striated ligamental area, the
oblique lateral teeth an<l three obscure ranlinal folds ant4»rior to the beak.

Hamilton gi-ou]). PraiVs falls, Onondaga Co., N. Y.

LlMOFFEUA OBSOLETA.

Page -249.
See Plates 20 and 29.

Fig. 10. A larg«» left valve, showing the form and siirfa<;e characters an<l a portion of the ligamentul area.

Hamilton group. PratVs falls, Onondaga Co., N. Y.

BRA

3 bias DOS Abb 7b7

Stanford Uniyenity Libi
Stanford, Calif omii

Sctoni tUa book «■ or bafan 4«

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