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SMITHSONIAN

CONTRIBUTIONS TO KNOWLEDGE

VOL. XIV.

IVBRT HAH IS A VALCABLK MEMBER Of SOCIETY, WHO, BT HIS OBSERVATIONS, RESEARCHES, ASD EXPERIMENTS, PROCDBIS

KNOWLIDOI FOB MEN. — SMITOSOK.

CITY OF WASHINGTON:
PUBLISHED BY THE SMITHSONIAN INSTITUTION.

MDCCCLXV.

ADVERTISEMENT.

THIS volume forms the fourteenth of a series, composed of original memoirs on dif-
ferent branches of knowledge, published at the expense, and under the direction, of
the Smithsonian Institution. The publication of this series forms part of a general
plan adopted for carrying into effect the benevolent intentions of JAMES SMITHSON,
Esq., of England. This gentleman left his property in trust to the United States
of America, to found, at Washington, an institution which should bear his own
name, and have for its objects the "increase and diffusion of knowledge among
men." This trust was accepted by the Government of the United States, and an
Act of Congress was passed August 10, 1846, constituting the President and the
other principal executive officers of the general government, the Chief Justice of
the Supreme Court, the Mayor of Washington, and such other persons as they might
elect honorary members, an establishment under the name of the " SMITHSONIAN
INSTITUTION FOB THE INCREASE AND DIFFUSION OF KNOWLEDGE AMONG MEN." The
members and honorary members of this establishment are to hold stated and special
meetings for the supervision of the affairs of the Institution, and for the advice
and instruction of a Board of Regents, to whom the financial and other affairs are
intrusted.

The Board of Regents consists of three members ex officio of the establishment,
namely, the Vice-President of the United States, the Chief Justice of the Supreme
Court, and the Mayor of Washington, together with twelve other members, three of
whom are appointed by the Senate from its own body, three by the House of
Representatives from its members, and six persons appointed by a joint resolution
of both houses. To this Board is given the power of electing a Secretary and other
officers, for conducting the active operations of the Institution.

To carry into effect the purposes of the testator, the plan of organization should
evidently embrace two objects: one, the increase of knowledge by the addition of
new truths to the existing stock; the other, the diffusion of knowledge, thus
increased, among men. No restriction is made in favor of any kind of knowledge;
and, hence, each branch is entitled to, and should receive, a share of attention.

jv ADVERTISEMENT.

The Act of Congress, establishing the Institution, directs, as a part of the plan of
organization, the formation of a Library, a Museum, and a Gallery of Art, together
with provisions for physical research and popular lectures, while it leaves to the
Regents the power of adopting such other parts of an organization as they may
deem best suited to promote the objects of the bequest.

After much deliberation, the Regents resolved to divide the annual income into
two parts — one part to be devoted to the increase and diffusion of knowledge by
means of original research and publications — the other part of the income to be
applied in accordance with the requirements of the Act of Congress, to the gradual
formation of a Library, a Museum, and a Gallery of Art.

The following are the details of the parts of the general plan of organization
provisionally adopted at the meeting of the Regents, Dec. 8, 1847.

DETAILS OF THE FIEST PART OF THE PLAN.

I. To INCREASE KNOWLEDGE. — It is proposed to stimulate research, by offering
rewards for original memoirs on all subjects of investigation.

1. The memoirs thus obtained, to be published in a series of volumes, in a quarto
form, and entitled "Smithsonian Contributions to Knowledge."

2. No memoir, on subjects of physical science, to be accepted for publication,
which does not furnish a positive addition to human knowledge, resting on original
research; and all unverified speculations to be rejected.

3. Each memoir presented to the Institution, to be submitted for examination to
a commission of persons of reputation for learning in the branch to which the
memoir pertains; and to be accepted for publication only in case the report of this
commission is favorable.

4. The commission to be chosen by the officers of the Institution, and the name
of the author, as far as practicable, concealed, unless a favorable decision be made.

5. The volumes of the memoirs to be exchanged for the Transactions of literary
and scientific societies, and copies to be given to all the colleges, and principal
libraries, in this country. One part of the remaining copies may be offered for
sale; and the other carefully preserved, to form complete sets of the wdrk, to
supply the demand from new institutions.

6. An abstract, or popular account, of the contents of these memoirs to be given
to the public, through the annual report of the Regents to Congress.

ADVERTISEMENT. V

II. To INCREASE KNOWLEDGE. — It is also proposed to appropriate a portion of the
/"//'.'//»•. mimiiilly, tn ,-jH'inf «l,ji<-ts of research, under t/te direction of suitable
persons.

1. The objects, tnul the amount appropriated, to be recommended by counsellors
of the Institution.

2. Appropriations in different years to different objects; so that, in course of time,
each branch of knowledge may receive a share.

3. The results obtained from these appropriations to be published, with the
memoirs before mentioned, in the volumes of the Smithsonian Contributions to
Knowledge.

4. Examples of objects for which appropriations may be made: —

(I.) System of extended meteorological observations for solving the problem of
American storms.

(2.) Explorations in descriptive natural history, and geological, mathematical,
and topographical surveys, to collect material for the formation of a Physical Atlas
of the United States.

(3.) Solution of experimental problems, such as a new determination of the
weight of the earth, of the velocity of electricity, and of light; chemical analyses
of soils and plants; collection and publication of articles of science, accumulated
in the offices of Government.

(4.) Institution of statistical inquiries with reference to physical, moral, and
political subjects.

(5.) Historical researches, and accurate surveys of places celebrated in American
history.

(6.) Ethnological researches, particularly with reference to the different races of
men in North America; also explorations, and accurate surveys, of the mounds
and other remains of the ancient people of our country.

I. To DIFFUSE KNOWLEDGE. — It is proposed to publish a series of reports, gicing an
account of the new discoveries in science, and of (he changes made from year to year
in all brandies of knowledge not strictly professional.

1. Some of these reports may be published annually, others at longer intervals,
as the income of the Institution or the changes in the branches of knowledge may
indicate.

2. The reports are to be prepared by collaborators, eminent in the different
branches of knowledge.

vi ADVERTISEMENT.

3. Each collaborator to be furnished with the journals and publications, domestic
and foreign, necessary to the compilation of his report; to be paid a certain sum for
his labors, and to be named on the title-page of the report.

4. The reports to be published in separate parts, so that persons interested in a
particular branch, can procure the parts relating to it, without purchasing the

whole.

5. These reports may be presented to Congress, for partial distribution, the
remaining copies to be given to literary and scientific institutions, and sold to indi-
viduals for a moderate price.

*

The following are some of the subjects which may be embraced in the reports: —

I. PHYSICAL CLASS.

1. Physics, including astronomy, natural philosophy, chemistry, and meteorology.

2. Natural history, including botany, zoology, geology, &c.

3. Agriculture.

4. Application of science to arts. ,

II. MORAL AND POLITICAL CLASS.

5. Ethnology, including particular history, comparative philology, antiquities, &c.

6. Statistics and political economy.

7. Mental and moral philosophy.

8. A survey of the political events of the world; penal reform, &c.

III. LITERATURE AND THE FINE ARTS.

9. Modern literature.

10. The fine arts, and their application to the useful arts.

11. Bibliography.

12. Obituary notices of distinguished individuals.

II. To DIFFUSE KNOWLEDGE. — It is proposed to publish occasionally separate treatises

on subjects of general interest.

^

1. These treatises may occasionally consist of valuable memoirs translated from

foreign languages, or of articles prepared under the direction of the Institution, or
procured by offering premiums for the best exposition of a given subject.

2. The treatises to be submitted to a commission of competent judges, previous
to their publication.

A I) V E R T I S K M K X T.

DKTAILS OF THE SKCOND PART OF THE PLAN OF ORGANIZATION.

This part contemplates the formation of a Library, a Museum, and a Gallery of
Art.

1. To carry out the plan before described, a library will be required, consisting,
1st, of a complete collection of the transactions and proceedings of all the learned
societies of the world; 2d, of the more important current periodical publications,
and other works necessary in preparing the periodical reports.

2. The Institution should make special collections, particularly of objects to
verify its own publications. Also a collection of instruments of research in all
branches of experimental science.

3. With reference to the collection of books, other than those mentioned above,
catalogues of all the different libraries in the United States should be procured, in
order that the valuable books first purchased may be such as are not to be found
elsewhere in the United States.

4. Also catalogues of memoirs, and of books in foreign libraries, and other
materials, should be collected, for rendering the Institution a centre of bibliogra-
phical knowledge, whence the student may be directed to any work which he may
require.

5. It is believed that the collections in natural history will increase by donation,
as rapidly as the income of the Institution can make provision for their reception ;
and, therefore, it will seldom be necessary to purchase any article of this kind.

G. Attempts should be made to procure for the gallery of art, casts of the most
celebrated articles of ancient and modern sculpture.

7. The arts may be encouraged by providing a room, free of expense, for the
exhibition of the objects of the Art-Union, and other similar societies.

8. A small appropriation should annually be made for models of antiquity, such
as those of the remains of ancient temples, &c.

9. The Secretary and his assistants, during the session of Congress, will be
required to illustrate new discoveries in science, and to exhibit new objects of art;
distinguished individuals should also be invited to give lectures on subjects of
general interest.

In accordance with the rules adopted in the programme of organization, each
memoir in this volume has been favorably reported on by a Commission appointed

viii ADVERTISEMENT.

for its examination. It is however impossible, in most cases, to verify the state-
ments of an author; and, therefore, neither the Commission nor the Institution can
be responsible for more than the general character of a memoir.

The following rules have been adopted for the distribution of the quarto volumes
of the Smithsonian Contributions: —

1. They are to be presented to all learned societies which publish Transactions,
and give copies of these, in exchange, to the Institution.

2. Also, to .all foreign libraries of the first class, provided they give in exchange
their catalogues or other publications, or an equivalent from their duplicate volumes.

3. To all the colleges in actual operation in this country, provided they furnish,
in return, meteorological observations, catalogues of their libraries and of their
students, and all other publications issued by them relative to their organization
and history.

4. To all States and Territories, provided there be given, in return, copies of all
documents published under their authority.

5. To all incorporated public libraries in this countrj', not included in any of
the foregoing classes, now containing more than 10,000 volumes; and to smaller
libraries, where a whole State or large district would be otherwise unsupplied.

OFFICERS

OF TUK

SMITHSONIAN INSTITUTION.

THE PRESIDENT OF THE UNITED STATES,

Ex-officio PRESIDING OFFICER OF THE INSTITUTION.

THE VICE-PRESIDENT OF THE UNITED STATES,

Ex offido SECOND PRESIDING OFFICER.

SALMON P. CHASE,

CHANCELLOR OF THE INSTITUTION.

JOSEPH HENRY,

SECRETARY OF THE INSTITUTION.

SPENCER F. BAIRD,

ASSISTANT SECRETARY.

W. W. SEATON, TREASURER.

ALEXANDER D. BACHE, ]

RICHARD WALLACH, EXECUTIVE COMMITTEE.

RICHARD DELAFIELD,

B

REGENTS.

Vice-President of the United Stales.

SALMON P. CHASE, Chief Justice of the United States.

RICHARD WALLACH, Mayor of the City of Washington.

LYMAN TRUMBULL, • Member of the Senate of the United States.

WILLIAM P. FESSENDEN, ...... "

GARRETT DAVIS, " "

SAMUEL S. Cox, Member of the House of Representatives U. S.

JAMES W. PATTERSON, " " "

HENRY W. DAVIS,

WILLIAM B. ASTOR, Citizen of New York.

THEODORE D. WOOLSEY, "of Connecticut.

Louis AGASSIZ, " of Massachusetts.

(VACANCY.)

ALEXANDER D. BACHE, "of Washington.

RICHARD DELAFIELD, ....... " of Washington.

MEMBERS EX-OFFICIO OF THE INSTITUTION.

ANDREW JOHNSON, President of tfte United Slates.

Vice-President of the United States.

WILLIAM II. SEW ARD, Secretary of State.

HUGH McCuLLOCH, Secretary oftlie Treasury.

EDWIN M. STANTON, Secretary of War.

GIDEON WELLES. Secretary of the Navy.

WILLIAM DENNISON, Postmaster- General.

JAMES SPEED, Attorney- General.

SALMON P. CHASE, . . . .' . . CJiief Justice of (lie United States.

DAVID P. HOLLOWAT, Commissioner of Patents.

RICHARD WALLACH, Mayor of the City of Washington.

HONORARY MEMBER.

JAMES HARLAN. The Secretary of the Interior.

TABLE OF CONTENTS.1

PAOI
AI'.TIl'LK I. INTRODUCTION. Pp.16.

Advertisement ........ iii

List of Officers of the Smithsonian Institution . . . iz

ARTICLE II. DISCUSSION OP THE MAGNETIC AND METEOROLOGICAL OBSERVATIONS MADE AT
THE GiRARi) COLLEGE OBSERVATORY, PHILADELPHIA, IN 1840, 1841, 1842,
1843, 1844, AND 1845. Third Section, comprising Parts VII, VIII,
AND IX. VERTICAL FORCE. INVESTIGATION OF THE ELEVEN (OR TEN)
YEAR PERIOD AND OP THE DISTURBANCES OP THE VERTICAL COMPONENT OP
THE MAGNETIC FORCE, AND APPENDIX ON THE MAGNETIC EPPECT OP THE
AURORA BOREALIS; WITH AN INVESTIGATION OP THE SOLAR DIURNAL
VARIATION, AND OP THE ANNUAL INEQUALITY OP THE VERTICAL FORCE ;
AND OP THE LUNAR EFFECT OP THE VERTICAL FORCE, THE INCLINATION, AND
TOTAL FORCE. By A. D. BACHE, LL. D., F. R. S., Mem. Corr. Acad.
Sc. Paris; Prest. Nat. Acad. Sciences; Superintendent IT. S. Coast Sur-
vey. Pp. 72. (Published May, 1864.)

ARTICLE III. DISCUSSION OF THE MAGNETIC AND METEOROLOGICAL OBSERVATIONS MADE AT

THE GlRARD COLLEGE OBSERVATORY, PHILADELPHIA, IN 1840, 1841, 1842,

1843, 1844, AND 1845. Fourth Section, comprising Parts X, XI, AND
XII. DIP AND TOTAL FORCE. ANALYSIS OF THE DISTURBANCES OP THE
DIP AND TOTAL FORCE; DISCUSSION OP THE SOLAR DIURNAL VARIATION
AND ANNUAL INEQUALITY OF THE DIP AND TOTAL FORCE; AND DISCUSSION
OP THE ABSOLUTE DIP, WITH THE FINAL VALUES FOR DECLINATION, DIP
AND FORCE BETWEEN 1841 AND 1845. By A. D. BACHE, LL.D., F. R.S.,
Mem. Corr. Acad. Sc. Paris; Prest. Not. Acad. Sciences; Superintendent
U. S. Coast Survey. Pp. 44. (Published January, 1865.)

ARTICLE IV. ON THE CONSTRUCTION OP A SILVERED GLASS TELESCOPE, FIFTEEN AND A HALF
INCHES IN APERTURE, AND ITS USE IN CELESTIAL PHOTOGRAPHY. By
HENRY DRAPER, M. D., Professor of Natural Science in the University of
New York. Pp. 60. (Published July, 1864.)
§1. Grinding and Polishing the Mirrors ..... 2

§ 2. The Telescope Mounting ...... 27

§ 3. The Clock Movement ....... 38

§ 4. The Observatory . . . 41

§ 5. The Photographic Laboratory ..... 46

§ 6. The Photographic Enlarger . . . . . .51

1 Bach memoir la separately paged and indexed.

xiv TABLE OF CONTENTS.

ARTICLE V. PALAEONTOLOGY OF THE UPPER MISSOURI : A REPORT UPON COLLECTIONS MADE

PRINCIPALLY BY THE EXPEDITIONS UNDER COMMAND OF LlEUT. G. K. WAR-
REN, U. S. Top. Engrs., IN 1855 AND 1856. INVERTEBRATES. By F. B.
MEEK AND F. V. HAYDEN, M. D. Part I. Pp. 158, and five Plates.
(Published April, 1865.)

Introductory Remarks ... vii

I. Silurian Age. Potsdam Period ..... 1

II. Carboniferous Age. Carboniferous Period ... .11

III. Carboniferous Age. Permian Period . . . . .48

IV. Reptilian Age. Jurassic Period ...... 66

Index ......... 129

Explanations of Plates.

ARTICLE VI. CRETACEOUS REPTILES OF THE UNITED STATES. By JOSEPH LEIDY, M.D.,
Professor of Anatomy in the University of Pennsylvania, Curator of the
Academy of Natural Sciences of Philadelphia. Pp. 140 and twenty plates.
(Published May, 1865.) •
Introduction . . ... . . .1

Sauria ......... 5

Chelonia . . . . . . . . .104

A Synopsis, in which an attempt is made to define more closely the Genera

and Species of Reptiles whose remains are described in the preceding pages 1 1 5
Index ......... 121

References to the Plates 123

SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE.
172

PALEONTOLOGY

OF TH1

UPPER MISSOURI

A REPORT UPON COLLECTIONS MADE PRINCIPALLY BY THE EXPEDITIONS UNDEE
COMMAND OF LIEUT. O. K. WARREN, U. 8. TOP. ENGRS., IN 1855 AND 1856.

INVERTEBRATES.

BY

F. B. MEEK AND F. V. HAYDEN, M.D.

PART I.

ACCEPTED FOR PUBLICATION, MAT, 1864.

COMMISSION

TO WHICH THIS PAPER HAS BEEN REFERRED.

ISAAC LEA.
Prof. JAMES D. DANA.

V

JOSEPH HENRY,

Secretary S. I.

COLLINS, PR1NTEB,
PHILADELPHIA.

TABLE OF CONTENTS.

Introductory remarks .

I. SILURIAN AGE. POTSDAM PERIOD.

PAOI

MOLLUSCA 1

Class BKACHIOPODA .... 1

Family LINCIULID.S .... 1

Genus LINOULEPIB .... 1

Lingulepis pinuiformis . . 2

prima ... 3

Genus OBOLELLA .... 3

Obolclla nana ... 4

Class GASTEROPODA .... 4

Subclass Pteropoda .... 4

Order THECOSMATA . . 4

Family CAVOLINID.S ... 4

Genus THKCA .

Theca gregaria

ARTICULATA ....

Class CKU8TACEA .

Subclass ENTOMOSTKACA
Order TRILOBITA .
Family I'AKAIH «.\ MM: .
Gcuus AORAULOS
Agranlos
Agranlos Oweni

II. CARBONIFEROUS AGE. CARBONIFEROUS PERIOD.

PROTOZOA 11

Class RmzopODA 11

Order FOKAMIMFERA . . . .11

Family CAMKIUMIU: . . .11

Genus FUBULINA ... 13

Fusulina cylindrica . . 14

MOLLCBCA 16

Class BRACITIOPODA . . . .16

Family SPIRIFERID.S .... 16

Genus SriRimi . . . .17

Snbgenns SPIRTFER ... 19

Subgenus TRIOONOTRBTA . . 19

Subgeuus MARTINI A . . .19

Spirifer planoconvexus . 20

Family PRODUCTIONS . . . .21

Genus CIIONETES .... 22

Chonetes mncronata . . 22

Family STROPIIOMKNID^B ... 23

Genus HEMIPRONITES ... 24

Hcmipronites crassus . . 26

Class LAMELLJBRANCHIATA ... 27

Family PTERIID.S «=(AVICULIDJB) . 27

Subfamily PTKRIMI.S ... 28

Geuns .M VAI.I.N A . 30

Til

PAO»

5

5

7
7
7
7
7
7
7
9
10

Myalina pcrattennata . 32

subqnadrata . 32

Subfamily PTERIIN.S ... 28

, Subfamily MELINIKA ... 28

Family CRABSATELLIU^ ... 34

Genus PLEUROPUORUS ... 34

Plenrophorus occidcntalis . 35

Family ANATINHXS .... 36

Genus ALLORISMA .... 36

Allorisma snbcnneata . . 37

Genus SEDOWICKIA ... 38

Sedgwickia topckaensis . . 40

? concava . . 41

? altirostrata . . 41

Genus Chtcnomya . . . .42

Cluunomya leavenworthensis . 43

Cooper! . . 44

Class GASTEROPODA .... 44

Subclass PROSOBRANCHIATA . . 44

Order RIPUIDOQLOSSATA . . 44

Suborder PODOPTHALMA . . 44

Family PLECRoroMARriD.fi . 44

Genus PLEUROTOMARIA . 45

Pleurotomaria humerosa 46

subturbinata 47

IV

TABLE OF CO Is' TENTS.

III. CARBONIFEROUS AGE. PERMIAN PERIOD.

PAGE

MOLLPSCA

Class LAMELLIBRANCHIATA . .48

Family PECTINID^E . .48

Subfamily PECTININ^B ... 48

Subfamily AVICULOPECTININ.ZE . 50

Genus AVICULOPECTEN . . 50

Aviculopecten ? . 50

McCoyi . 50

Family PTEEIID^; . . .51

Subfamily PTERINHN^; . . .51

Genus MYALINA . . . .51

Myalina aviculoides . . 51

permiana . . 51

Subfamily PTERINIINJE . . .53

Genus EUMICROTIS ... 53

Eumicrotis Hawni . . 54

var. ovata 55

Subfamily MELININ^E . . .56

PAGE

Genus BAKEVELLIA . . .56

Bakevellia parva . . 57

Family TRIGONIID.*: . . . .57

Genns SCHIZODUS . . . .58

Schizodus ovatus ... 59

Family NUCULID^; .... 59

Subfamily NUCULANIN^E ... 60

Genus YOLDIA .... 60

Yoldia ? subscitula . . 60

Subfamily MALLETIN^E ... 60

Family CRASSATELLID^E . . .61

Genus PLEUROPHORUS . . .61

Pleurophorus ? subcuneatus . 61

? Calhouni . 62

Class CEPHALOPODA ... \ 63

Order TETRABRANCHIATA ... 63

Family NAUTILID^E ... 63

Genus NAUTILUS .... 64

Nautilus eccentricus . . 65

IV. REPTILIAN AGE. JURASSIC PERIOD.

RADIATA . . .66

Class ECHINODERMATA . . . .66

Order CRINOIDJE .... 66

Family PENTACRINID^E ... 66

Genus PENTACRINITES ... 66

Pentacrinites asteriscus . 67

MOLLUSCA 68

Class BRACHIOPODA . . . .68

Family LINGULID-S; .... 68

Genus LINOULA . . . .68

Lingula brevirostris . . 69

Family RHYNCHONELLID^E . . .70

Genus RHYNCHONELLA . . .70

Rhynchonella ? . . 71

Class LAMELLIBRANCHIATA . . .72

Family OSTREID^E .... 72

Genus OSTREA . . . .72

Ostrea Engelrnanni . . 73

Genus GRYPH^EA . . . .74

Gryphaea calceola var. nebrascensis 74

Family PECTINIDJE . . . .76

Subfamily PECTININ..E . . .76

Genus CAMPTONECTES . . ' . 76

Camptonectes bellistriatus . 77

? extenuatus . 78

Family PTERIID.*: .... 79

Subfamily PTERIIN./E ... 79

Genus PTERIA . 79

Subgemis OXYTOMA . . 80

Pteria Munsteri . 80

Genus EUMICROTIS . . .81

Eumicrotis curta . . 81

Family TRIGONIIDJE . . . .82

Genus TRIOONIA .... 82

Trigonia Conradi ... 83

Family MYTILID^! . . . .84

Genus VOLSELLA .... 85

Volsella pertenuis . . .86

formosa ... 86

Family ARCID.E 87

Subfamily ARCING .... 88

Subfamily MACRODONTINJE . . 88

Genus GRAMMATODON ... 89

Grammatodon inornatus . 90

Subfamily AXININJE ... 88

Family UNIONID^E .... 90

Genus UNIO 92

TJnio nucalis ... 92

Family CRASSATELLIDJE ... 93

Genus ASTARTE .... 93

Astarte fragilis ... 94

Astarte inornata ... 94

Family TANCKEDIID^; ... 95

Genus TANCREDIA .... 95

Tancredia Warrenana . . 96

? ffiquilateralis . . 96

Family CARDIID^: . . . .97

I \ i: I . i: .. i OOHTK NTS

MM

Genus PROTOOARMA ... 97

I'rutix-anliii Sliumurili . . 9S

Family ANATIMP.E .... '.'-'

Qeiius Mv.\i iri.-i .... 99

Myarilr* in . . Itid

sulH'Ui|>ticus . . lul

Genus TIIUACIA . . . .lul

Thrucia ? MiMirvis . . 102

? arcuutu , .102

Genus PHOLADO.MYA . . .102

rholiulotnyu humilis . . 104

"i>.\ .... 105

Slllx-lu-^ I'l I.M'lNIFERA . . . 105

Order F.NOPERCULATA . . .105

Suborder I.iMxoriiiiA . . 105

Family I.iMS.sm.*: . . . 105

Subfamily LIMN^IN^B . . 105

Subfamily I'IIYSIN^E . . 105

Subfamily PLANORBIN.S . 105

Genus PLANORBIS . .106

Planorbis veterans . 107

Subclass PROSOBRANCHIATA . .108

Order RIPHIDOGLOSSATA . . . 108

Suborder PODOPTHALMA . . 108

Family NKRITID/E . . . 108

Genus NERITELLA . .108

Neritella nebraacensis . 109

Order CYCIX)BRASCHIATA . .110

? Family DENTALIID^ . .110

Geuus DENTALIUM . . .111

Dentalium subquadratum 111

PAOB

Order CTENOBRANCIIIATA . .111

Suborder KOSTRIFEBA . . .111

Family VALVATIB^ . .111

Genns VALVATA . . . 112

Subgcnus TROPIDINA . 113

Valvata? acabrida 113

Family VIVIPARIH.K . .113

Genus Vi vi PARUS . .114

Yiviparus Gilli . .115

Genus LIOPLACODES . .115

Lioplacodes Teternus . 116

Class CEPHALOPODA . . . .116

.Order TETRABRANCHIATA . . .116

Family AMMONITID^E . . .116

Trigonelletes . . .118

Genus AMMONITES . . .121

Ammonites cordiformis . 122

Ammonites Henry i . .123

Order DIBRANCHIATA . . . 124

Suborder DECAPODA . . .124

Family BELEMNITID.& . . . 124

Genus BELEMMTES . ... 124

Belemnites densus . .126

ARTICULATA 127

Class ANNULATA 127

Order TUBICOLA . . . .127

Family SERPULID.S . . .127

Genns SERPULA . . . .127

Scrpula ? . .128

INTRODUCTION.

THE following Memoir is the first part of a work intended to contain descriptions
and illustrations of the inverteliratc fossil remains collected by the Exploring Expe-
ditions under the command of Lieut, (now Maj.-Gen.) G. K. Warren, as well as
by Dr. Ilayden and others, in the Upper Missouri country.1 It was originally pre-
pared with the expectation that it would form part of Lieut. Warren's official report
to the War Deportment, fast circumstances having prevented the final completion
of the hitter, with the concurrence of Lieut. Warren, the Memoir was offered to the
Smithsonian Institution by the authors for publication in the Smithsonian Contribu-
tions to Knowledge.

Much the larger proportion of these collections being from the Cretaceous and
Tertiary rocks, which occupy almost the entire surface of the great area explored,
it was at first intended to confine the work entirely to the full illustration and de-
scription of the fossils of these two epochs. The subsequent interesting discovery,
however, of Jurassic and Primordial rocks, with the intermediate Carboniferous
beds at the Black Hills and a few other localities, and of the Permian in Kansas,
rendered it necessary that some attention should also be given to the organic
remains of these older deposits. Yet as the Carboniferous beds, which are very
fossiliferous, only occupy inconsiderable portions of the country to be reported upon,
while a large number of the fossils occurring in them are identical with forms already
published in various State and General Government Reports, and elsewhere, it has
not been deemed desirable to attempt to include all the known species from the
rocks of that age within the field of exploration, as this alone would require an ex-
trusive work. The plan adopted, therefore, is to give full descriptions and figures
of all the known Tertiary, Cretaceous, Jurassic, and Primordial fossils of this region;
together with the new, and a few otherwise interesting forms, contained in the
collections from the Permian and Carboniferous rocks of Kansas and Southeastern
Nebraska.*

The first part of this work, now presented, includes the Primordial, Carboni-
ferous,8 Permian, and Jurassic species, which constitute but a small proportion of

1 This great extent of country was formerly known under the general name of Nebraska Territory,
but has been recently divided into Dakota, Nebraska, and Montana Territories.

• No middle or upper Silurian, or Devonian beds, have yet been identified by fossils, at any
locality in the country explored, north of the South Pass.

1 It is proper to state, for the information of those not acquainted with the geology of the western
Territories that the few carboniferous species here figured were not selected, with one or two excep-

( vii )

INTRODUCTION.

the whole. The next part, which will be the largest, will contain the Cretaceous
species, and the third the Tertiary. Along with the second or third part, an intro-
ductory chapter will be presented, giving a general sketch of the geological forma-
tions from which these fossils were collected ; their geographical range, lithological
characters, thickness, &c. ; with remarks . on their relations to formations further
eastward, both in this country and Europe.

In order to make the work as useful as possible to students, descriptions of the
genera and families to which these fossils belong have also been added. Under
each family, all the genera, both recent and fossil, believed to be properly included,
are mentioned ; while the relations of the genera described are discussed, and at the
head of each generic description the synonyms, with full references, are given; like-
wise, when known, the etymology of the name, and the typical species of each genus.
The probable periods at which the several genera, as denned, were introduced, when
they attained their maximum development, and at what time they seem to have
died out, if not represented in our existing seas, are also stated.

The portion of the work now presented, contains a larger amount of text, in
proportion to the number of species figured and described, than will be found in
the succeeding parts, in consequence of the fact that descriptions of a number of
genera and families are here given which it will not be necessary to repeat, the plan
being to refer back to these descriptions when other species belonging to any of
these groups come to be mentioned subsequently.

From the references at the head of the specific descriptions it will be seen that
preliminary notices of most of the species have been published, from time to time,
under the joint names of the authors, in the Proceedings of the Philadelphia
Academy of Natural Sciences. Subsequently these descriptions have been almost
entirely rewritten, and extended, by the senior author (Mr. Meek), who has like-
wise prepared the accompanying descriptions of genera and families, with the
remarks on their relations, geological and geographical range, &c.

The authors avail themselves of this opportunity to acknowledge their obligations
to Prof. Henry for the use of rooms, books, and other facilities at the Smithsonian
Institution, during the progress of the work: also to Prof. Dana and Prof. Agassiz,
for the use of a few rare works, not in the Smithsonian library.

They are also under obligations to most of the geologists and palaeontologists of
the country, either for information in regard to types described by them, or respect-
ing the geological range of particular forms in their several fields of observation.
In this connection they take pleasure in mentioning the names of Mr. T. A. Conrad
and Mr. Wm. M. Gabb, of Philadelphia; Dr. B. F. Shumard, of St. Louis; Mr. E.
Billings, of the Canadian Geological Survey ; Prof. George H. Cook, State Geolo-
gist of New Jersey ; Mr. A. H. Worthen, State Geologist of Illinois ; and Prof. A.
Winchell, State Geologist of Michigan.

tions, as examples of the more characteristic forms found in rocks of that age here, but because they
are either new to science, or have not been previously well illustrated in this country. Geologists,
however, may rest assured that they all occur directly associated with all our most common western
Coal Measure species.

INTRODUCTION. i.

To the several conchologists and laborers in other departments of Natural History,
with whom they have more or less freely communicated, and from whom they have
rerehed occasional suggestions, they desire to express their thanks, without having
it thereby understood that any of these gentlemen are responsible for conclusions
finally adopted. Those to whom their acknowledgments are more especially due
are, Dr. Win. Stimpson, and Prof. Theo. Gill, of Washington, D. C. ; Dr. A. A.
Gould, of Boston ; Dr. Isaac Lea and Mr. Geo. W. Tryon, of Philadelphia ; Dr.
P. P. Carpenter, of Warrington, England ; Mr. W. G. Binney, of Burlington, New
Jersey ; Mr. J. G. Anthony, of Cincinnati ; and Mr. Temple Prime and Thomas
Bland, of New York.

Most of the published works on Geology, Palaeontology, and Conchology have
been consulted during the preparation of the work, and a list of these will be
appended to one of the succeeding parts.

PALEONTOLOGY OF THE UPPER MISSOURI.

SILURIAN AGE,

(POTSDAM OE rSlMOBDIAL PEKIOD.)

MOLLUSCA.

CLASS BRACHIOPODA.

FAMILY LINGULID^E.

Shell subcqnivalvc, hingeless, oblong, oval, subtrigonal, or suborbicu-
lar. covered with a corneous epidermis ; texture subcorneous or testaceous;
structure laminated and minutely tubular or more or less compact; in-
terior without calcified spiral or loop-like appendages.

Animal with elongated fleshy, subspiral oral arms, situated on each
si (It; of the mouth, and fringed with numerous cirrhi; attached by a thick
peduncle passing out between the beaks of the valves; mantle highly
vascular, and iViuirnl with corneous Betas.

This family includes the four known genera, Lingula, Lingulepia, O&oZtw, and
Ol,,,l, II, i Y It was introduced at the dawn of the Silurian age, and is represented in
all the succeeding formations, as well as in our existing seas.

Genus LINGULEPIS, HALL.

Sgno*. — Linyula (sp.), Owns, Report Wisconsin, Iowa and Minnesota, 1852, p. 583 ; HALL, Poster & Whitney's Report
Lake Sup. part ti, 1851 , p. 204 ; MKEK & HATDRH, Proceed. Acad. Phila. 1858, p. 49 (not Liayula, BBD.I. 1792).
/.iMi/M/./iin, HALL, Sixteenth Ann. Kept. Regents' University , N. Y., 1863, p. 129.
Elym. — Lingulii, a little tongue ; Xwrtc, a scale.
Type.—Lingula pinmiformll, Own.

Shell thin, subovate, or subtrigonal ; composition and stnicture as in LinguJa.
Ventral or larger valve with beak more or less produced and pointed ; visceral
scar trilobate, with a longitudinal raised mesial line or septum — lateral divisions
diverging and usually longer than the middle one. Dorsal or smaller valve with
the beak less produced than that of the other ; visceral scar flabclliform.

The above description is mainly as given by the author of the genus, excepting
that we have described the markings seen within the valves as visceral scars instead
of muscular impressions, and left out a few such characters as " inequivalve, equi-
lateral," &c., which being common to all the genera of the family, and indeed normally
characteristic of the whole class, need not be repeated in a generic description. We

1 February. 1804. ( 1 )

2 PALEONTOLOGY OP THE UPPER MISSOURI.

would remark, however, that we have had an opportunity to examine a collection
of the typical species from the falls of St. Croix, recently deposited in the museum
of the Smithsonian Institution, and that we have seen the peculiar visceral scar
shown in the form supposed to be the smaller or dorsal valve of the same. The
specimens of the other valve, we have seen, are not in a condition to show so clearly
the trilobate visceral scar, though a few of them exhibit traces of its outline.
From the examination of these specimens, and the published figures, we are clearly
satisfied that these internal markings are the scars of the visceral sack, and not, as
has been supposed, " muscular impressions." The impressions of the posterior
occlusor muscles are located much as in Lingula, one on each side of the middle
lobe of the visceral scar, in the sinus between it and the lateral lobe on each side.1
In the other valve the minute impressions -of these muscles are placed apparently
within the middle lobe of the flabelliform visceral scar, much as in Lingula, except-
ing that they are closer together, and located a little farther back.

It will thus be seen that the arrangement of the muscular system in this ancient
type has yet to be clearly defined, and that it is much more nearly related to the
genus Lingula than has been supposed ; though the differences in the nature of the
visceral scars, and the general form of the shell, were probably coincident with
differences in the structure of the animal that would place this type in a distinct
genus from our modern Lingulas.

The only species yet positively known to possess the characters of this genus, is
from the base of the Silurian System, though it is probable many — possibly all —
of the older Palaeozoic species usually referred to the genus Lingula, will be found
to belong here. Until the interior of many species have been examined, nothing
can be known in regard to the geological range of the genus. So far, however, as
can be determined from external form alone, it seems to range up at least to the
Medina Sandstone of N. York Upper Silurian Series — Lingula cuneata of Conrad,
from that rock, having more nearly the outline of the typical species of this genus
than that of the modern Lingulas.

langnlepis pinniformis.

(PLATE I, Fig. 1, a, 6.)
Lingula antiqva, HALL, Foster & Whitney's Report Lake Superior, 1851, p. 204, pi. xxiii, Fig. 2. — MEEK & HATDEN,

Proceed. Acad. Nat. Sci. Phila., March, 1858, p. 49 (not HALL, 1847).

Lingula pinniformis, OWEN, Rept. Geol. Wisconsin, Iowa, and Minnesota, 1852, pi. i, B, Figs. 4, 6, 8, &c.
Lingulepis pinniformis, HALL, Sixteenth Report Regents' University, N. Y., 1863, p. 129, pi. vi, Figs. 14 and 16.

Shell subovate, or ovate-subtrigonal, rounded in front and angular at the beaks, moderately convex ; sides con-
verging to the beaks, with straight or concave outlines. Beaks more or less produced, that of the larger valve
attenuate and acutely pointed. Surface marked by rather obscure concentric strise, which are sometimes crossed by
faint radiating lines, usually moat apparent on exfoliated surfaces, and generally quite distinct near the front, on
the interior surface, and on internal casts.

Length, 0.68 inch ; breadth, 0.50 inch. Other individuals in the collection proportionally wider.

This shell agrees so nearly in outline with the Escanaba form figured by Prof.

1 On comparing the trilobate visceral scar of the larger valve in Lingulepis, with that of the same
valve in the recent Lingula analina, as figured by Mr. Davidson (Mon. Carb. Brach. Grt. Brt., p.
200), it will be seen that they are very similar, excepting in the greater prolongation of the lateral
lobes in Lingulepis.

SILURIAN AGK 3

I Tall, in Foster and WhitmVs Report, as a variety of I.'nujiilo until/tin, that we were
led to refer it to that species, not having .specimens of the New York shell at hand
for comparison. Nor had \ve at that time within reach, specimens of the Wisconsin
form no\v made the t\pe of the new genus I.imjulepis. On comparison with speci-
mens of the latter, howe\er, we find our shells agree so nearly with them that we
do not feel fully warranted in considering them distinct, though some slight
differences seem to be ohsenahle. They have the same general form and attenuate
beak. but. appear to differ in having the beak of the larger valve more flattened
to\\ards the pointed extremity ; still the species jiiiini/nnnix seems to vary some-
what in this respect, and as our specimens are in a bad state of preservation we arc
not sure these differences are constant.

Should a comparison of better specimens show our shell to be distinct, it may
take the name l.iu</nf> j>i* dakalmuit,

Lot-iif i/i/ iiif/ fHisitinn. Central part of Black Hills, Dakotah Territory. Pots
dam Sandstone, at the base of the Silurian system. (No. 1026o, type of description
and figure, Smithsonian Collection.)

priiua.

(PlATE I, Fig. 2, <I, b.)

Limgula prima (CoKRAD) HALL, Palnont., New York, 1, 1847, 3, PI. I, Fig. 2, a, i.— HALL, Foster and Whitney's
K.-|,t. Uke Superior, 204, 1851, PI. xxiii, Fig. 1.

shell small, ovate, rather gibbous, and comparatively thick ; rounded in front ; sides more or less convex in outline :
beaks obtuse and convex ; surface marked by obscnre lines of growth, and more or less distinct radiating stria ;
the latter moat strongly defined on exfoliated surfaces.

Length, 0.18 inch ; breadth, about 0.14 inch ; convexity (larger valve), 0.03 Inch.

Our specimens are generally worn, or more or less exfoliated, but as near as can
be determined they seem to agree with the above cited New York species. We
refer them to the genus Lin <////<///«, provisionally, not having seen the muscular
impressions, but believing it to be more than probable that most, if not all of the
older Palaeozoic species of this general form, will be found to possess the internal
characters of that genus.

We would have suspected that these shorter and more oval specimens might be
the dorsal valves of the pinrriformw, were it not for their smaller size, and the fact
that they are much more convex than those supposed to be the smaller valve of that
speries from St. Croix River.

Locality and position, same as last. (No. 1027a, and 1027i.)

Genus OBOLELLA, BILLINGS.

Sy»on __ Oboltlla, BILLIXOS, New. up. Sil. Foss. Nov. 1861, 7, fig. 6, a, b, e, d.

Aviculal (dewinamata), HALL, Pal. New York, I, 1852, p. 292, pi. 80, f. 3.

Litgulat (desqnamata), HALL, Twelfth Kept. Regents' University, N. Y., Oct. 1859, p. 66.
Elym. — Diminutive of Obolui, the name of a small Greek coin.
Type.— Oboltlla chromalica, BlLLlBGS.

" Shell ovate circidar or subquadrate, convex or plano-convex. Ventral valve
with a false area which is sometimes minute and usually grooved for the passage
of the peduncle. Dorsal valve cither with or without an area. Muscular impres-

4 PALAEONTOLOGY OP THE UPPER MISSOURI.

sions in the ventral valve, four ; one pair in front of the beak near the middle or in
the upper half of the shell, and the others situated one on each side near the car-
dinal edge. Shell calcareous. Surface concentrically striated, sometimes with thin
extended lamcllose edges."

" In general form these shells somewhat resemble Obolus, but the arrangement of
the muscular impressions is different. In Obolus the two central scars have their
smaller extremities directed downwards, converging towards each other; but in
this genus the arrangement is exactly the reverse." — BILLINGS.

The six or eight known species of this genus, are small shells, and all occur near
the base of the Silurian System. The group has a wide geographical range.

Obolella liana.

(PLATE I, Fig. 3, a, b, c, d.)

Obolella nana, MEEK & HAYDEN, Proceedings Acad. Nat. Sciences, Philadelphia, October, 1861, 435. — HAYDEN, Amer.
Journ. Sciences, XXXIII, 1861, 2d ser. p. 73.— DANA'S Geology, p. 187, Fig. 244 A.

Shell very small, subcircular or transversely suboval ; moderately convex ; rather thick ; front broadly rounded ;
sides more narrowly rounded. Beak of dorsal valve short and obtuse. Ventral valve proportionally a little longer
than the other, or about as wide as long, and having a slightly more prominent beak ; without a distinct mesial
ridge within ; scar of anterior adductor muscle ? located behind the middle ; impressions of sliding muscles narrow ;
cardinal area rather narrow and flattened ; groove for the passage of the peduncle shallow. Surface marked by a
few small concentric grooves or impressed striae ; exfoliated specimens showing small regularly disposed radiating
striae.

Length of dorsal valve, 0.15 inch; breadth of do., 0.17 inch; convexity, 0.15 inch. Length and breadth of a
ventral valve of a smaller specimen each, 0.14 inch.

This species is so closely allied to Obolella chromatica of Billings, the type of the
genus ("New Species, Lower Sil. Foss."p. 7), that we were inclined to regard it as
specifically identical, until we had an opportunity to compare it with specimens of
Mr. Billings' species sent to us by him. On comparing it with these, we find it is
more convex, and proportionally broader, while its concentric markings are stronger.'
The substance of its shell differs in showing radiating strias on the inner lamina)
of exfoliated specimens.

Locality and position, same as last. (No. 1025.)

CLASS GASTEROPODA.

SUB-CLASS PTEROPODA.

Order ThccosiiinUi,

FAMILY CAVOLLNTD^E.

Shell non-spiral, symmetrical, more or less elongate-conical, or subglo-
bose, curved or straight ; the subglobose, and a few of the more elongate
forms, provided with lateral fissures for the passage of the mantle.

Animal with two united wing-like fins, but without a foot ; abdomen
large ; gills in pairs on the ventral side within the mantle cavity, trans-
versely plaited and ciliated. Internal superior organs of generation on
the right side. Lingual teeth 1, 1, 1 (in Cavolina), claw-shaped.

SILURIAN AC K 5

This family includes tin- following genera represented in our existing Roas, \\/ .
( 'iifilinn, /'I, in;, j, us, (_'li<>, /l<i/<mtiti>/i, ,SV///Wa ami Ctn-'urin. The extinct g«'licra
nio-t probably belonging here, are '/'/// «i/. Suit, />//<». \'<ii/in> /In and l't< r<>t]n<-a f The
fn-sil shells ( 'nun/, ifiu and ('i>/»,/>n'»n, are also generally referred to this family, but
if there is no mistake about the c \i-ti are of «.epta and a sipliunrlc in the former
genus (sec Cnniiliirin tn-nhmeitHi*, Pal. X. Y. Vol. 1, p. '.''.'I, f. 4), it would be ex-
cluded, not only from this family, but probably from the subclass J'Ur«j>i«la.

Genus THECA, SOWERBT.

Synon — Thtca, J. de C. SOWIBBT, MSB., In Morris' Memoir, Strexelsckl's N. 8. Wales, 1845, p. 389.

]*u3iHnculu>, BABBAHDE, Nenes Jahrb. far Min. 1847, p. 364.
Etymtit. — 3'xt, a sheath, case or covering.
Typr.—THeca lanceolata, MORRIS.

Shell thin, more or less elongate-conical, nearly or quite straight ; aperture and
section trigonal or subtrigonal ; surface smooth or striated. (Animal unknown.)

According to Prof. Barrandc (who had not seen the description of the genus
Theca at the time he proposed the name Puginncvlus), the aperture of these little
shells was closed by a triangular shelly operculum. This would seem to be a rather
anomalous character in the family to which this group appears to belong.

The genus Theca commenced its existence amongst the earliest forms of life
during the primordial period, and its remains are found in various parts of the
Silurian system, both upper and lower; though it probably attained its greatest
development during the deposition of the Lower Silurian rocks. It is also known
to range up into the Devonian, two species having been described by Sandberger
from deposits of that age in the Rhcinish Provinces. As one species — T. aculeata,
Hall — has been discovered in beds in this country holding a position near the
dividing. line between Devonian and Carboniferous rocks, it is probable the genus
did not become entirely extinct until some time after the close of the Carboniferous
epoch.

Theca

Thtra (Puyiunculut) gregaria, MURK & HAYDBH, Proceed. Acad. Nat. Sol. Fhila., December, 1861, p. 436. — DASA'S
Geology, p. 187, Fig. 244 B.

Shell small, straight, acutely conical ; dorsal side compressed or nearly flat ; ventral side rounded ; lateral mar-
gins obtusely angular, and converging regularly at an angle of about 18° to the pointed lower extremity ; aperture
and transverse section nearly semicircular, or forming rather more than half a circle ; lip on the flat or dorsal side
somewhat produced, and rounded in outline ; surface of casts nearly or quite smooth.

Length, 0.45 inch ; breadth, 0.16 inch ; convexity, 0.10 Inch at the aperture.

d

Tkeca gregaria.
a. Ventral tide. 6. Dorsal side. <•. Side view. d. Transverse section.

These delicate little- shells must have existed iu great numbers, since on a single
flat piece of sandstone, not more than sL\ by eight inches across, we have counted

6 PALAEONTOLOGY OP THE UPPER MISSOURI.

near two hundred individuals, and yet they occur in all parts of the mass, so that
every new surface exposed in splitting it, is seen to be covered with them. They
are not crushed or distorted in the slightest degree, and are all casts, the shell
itself being in no instance preserved.

The species is allied to Theca? triangularis, Hall (Palscont. N. Y. Vol. I, p. 313,
PI. Ixxxvii, Fig. 1 a, 5, c, d), but never attained near so large a size, and is more
rounded on the ventral side. It is probably more nearly related to T. primordialis,
Hall (An. Kept. Geol. Survey "Wisconsin, 1861 1 p. 80), but never attains more than
about half the linear dimensions of that species, and we have seen no traces of the
arching undulations on its flat side, mentioned in the description of T. primordialis,
though some of the impressions in the matrix show very faint indications of fine
arching transverse stria? on this side. In size and form it agrees quite closely with
Salterella dbtusa of Billings (New. Sp. Low. Sil. Foss., p. 18, Montreal), but it seems
to be a thinner shell, and shows no evidences of being composed of successive
layers, nor is it provided with the sharp annulations seen in the type of that genus.

Locality and position. Near the head of Powder Eiver, in Big Horn Mountain,
Idaho Territory. From the Potsdam or Primordial Sandstone. (No. 1181.)

S1LUU1AK AUE.

ARTICULATA.

CLASS CRUSTACEA.

ORDER t Trilobita.

FAMILY PAEADOXID^E.

ll<-ail \\rll developed, sometimes very large ; facial sutures generally
sultparallrl, especially the anterior portion; ribs each provided with a
longitudinal furrow. Thorax larjre, consisting of from twelve to twenty
» •-infills. J'yjridium very small, and always with few segments.

This family includes the genera Paradoxiden, Olenus, Olenellus, Peltura, Sao,
>/ni/ii*, Trin rf/irits, Agraulas, EUipaocqtkdhtt, ConocorypJte,1 and probably
Otoriocephalitt, Onpioephaku sod. Menoeepfalitt. It embraces a con-
siderable number of species, some of which attain a very large size. They are
jjeiierally rrmarkablc for the great development of the thorax, compared with the
Miiall si/e of the ])y^idiiim. The whole family, with the exception of Triarthrus,
seems to be mainly, if not entirely, confined to the Primordial or oldest group of
fossilifcrous rocks.

Genus AGRAULOS, CORDA.

Synon. — Arinn, BARRAlcnx, Note I'n'liin. 1846, 12 (not Fenusac, 1819).

Ilmr, CORDA, Prodr. 1847 (not Oken, 1815, nor Lesson, 1837).

Ayraulot, CORDA, ib. 1847.

Arionidet (BABBAKOK, MSS.), Bnosx, Index Pal., 1848, 103.

Arioncllui, BABRAKDE, Syst. Sil. Boh. 1852.

Crtpictphaluit (part), OWBX, Report Geol. Surrey, Wisconsin, Iowa and Minnesota, 1852, p. 876.
Elymnl. — AXP*VA»C, daughter of the Bret King of Athens.
Type. — Arion ceticephaliu, BABBANDE.

Entire animal more or less elongate-ovate, distinctly trilobate. Head forming
more than a semicircle, nearly straight behind ; glabella conoid-subovate, provided,
in young examples, with three or four lateral furrows, which are usually nearly or
quite obsolete in the adult, margined in front by a more or less developed border
connecting with the cheeks on each side. Facial sutures widely separated, ex-
tending and converging forward from the eyes so as to intersect the anterior
margin within a point where a line would strike it if drawn through each eye,

« Conocoryphr, Corda, 1847 = Conocephalus, Zcnker, 1833 (not Thunbcrg, 1812) ~ Conocepha-
lites, Barrande, 1852.

8 PALEONTOLOGY OP THE UPPER MISSOURI.

parallel to the longer axis of the body ; behind the eyes they diverge and extend
backwards, so as to cut the straight posterior margin somewhat within the lateral
angles. Cheeks small and narrow ; eyes small. Hypostoma oval, truncated ante-
riorly. Segments of body in the adult of the typical species, sixteen ; in the pygi-
dium three.

As stated by Barrande, this genus presents several points of analogy to Para-
doxides, particularly in the arrangement of its facial sutures, and the great number
of its thoracic segments, as well as in the small size of its pygidium. In Europe it
is only known to have been represented by the single typical species, which is con-
fined to the primordial zone. Several species have been described from rocks of
the same age in America, and the genus is not certainly known to have existed
after the close of the Primordial epoch.

We would with pleasure adopt the name Arionellus, proposed for this genus by
Prof. Barrande, in his splendid work on the Trilobites of Bohemia, if we could do so
consistently with the just and inflexible law of priority, which we have endeavored
to obey in all cases. The fact that Corda's first name, Herse, was applied to a young
individual, would not, we should think, be a sufficient reason for setting it aside,
especially as no doubt can be entertained of its generic, and even specific identity
with the type of Arionellus. It cannot stand, however, for the reason that it had
been used by Oken, in 1815, for a genus of Lepidoptera, and by Lesson for a genus
of Birds in 1837. The next name, then, that we are compelled to consider, is
Agraulos, which Prof. Barrande thinks should be rejected, in consequence of its
similarity to Agraulis, used by Boisduval, in 1836, for a genus of Lepidoptera.
These names, however, seem to us to be sufficiently distinct to prevent confusion ;
certainly they are as much so as many others retained in various departments of
natural history— such, for instance, as Trigonia and Trigoiia, in Conchology, Cy-
prina and Cyprinus, in Conchology and Ichthyology, and Pica and Picus, in
Ornithology.

We should also feel constrained, on the same principle, to adopt Corda's first
name Conocorypfo, instead of Conocephalus or ConocepJialites. The reasons for so
doing will be better understood by the following statement of the synonymy of
this genus. In the first place Zenker named it Conoceplialus, in 1833. Finding
this name had been used, however, in 1812, for a genus of Orthoptera, by Thun-
berg, he changed it in the explanations of his figures in the same work, to
Trigonocephalus, which had also been previously used by Oppel for a genus of
Reptiles, in 1811. In 1847, Corda applied the three generic names, Conocoryphe,
Ptychoparia and Ctenocephalus to three species of this same genus of Trilobites.
• In 1852, Prof. Barrande, seeing that none of the older names could be adopted for
this group, also rejected Corda's names, on the ground that he had, Avithout suffi-
cient reason, divided the genus, and that as no one of his names was applied to the
whole group, he was opposed to retaining either of them, and consequently pro-
posed the new name Conocephalites. The law of priority, however, requires us to
adopt the first unoccupied name in this and in all other cases where no doubt can
be entertained in regard to the generic identity of its type with the types of the sub-

SI I.r HI AN A OK. 9

sequent!) proposed genera. The other names applied },\ Cm-da fall into the list of
•ynonynu, juri a> it'the\ had IK en proposed l>\ an\ other author at an\ subsequent
time.

Owciii.

Arlom.llui (rr<-;,,V./,Aa/iii) Ovmi, UKEK & lUti.px, I'roceed. Acad. Nat. Sol. Phlla., December, 1861, p. 43«.
ArioHttlmtt thctni, UKKK It UATI.KX, Am. Jour. Bel. Bee. Bcr. XXXIII, 74, January, 1862.

-. -mi . in-iilar, or nearly semlelliptic in outline, iU length equalling about two-third* its breaillh, rather dis-
tiiu-tly convex ; posterior margin more or \ea concave in outline, anil provided with a deep, rounded marginal
along each lateral slope. Glabella oblong-subovate, rather gibboat, elevated above the cheeks and tapering
towards th« rounded front with slightly convex lateral margins ; greatest convexity near the middle and behind ;
separated from the cheeks, on each side and in front, by a distinct furrow ; neck furrow passing entirely across, but
>! i. litly •!.•.-]. .TOII each .tide than at the middle ; lateral grooves three, very short, obscure, or (In casts) nearly obsolete,
:ui.i I. nt .-Ii.-litly ..l,li,|»... (Yrvk-al segment a little convex at its posterior outline, less eliirated than the glabella,
.Aiit--n.il >1«>(K- in advance of the glabella less than half as wide as the length of tin- latter, and provided with a
distinct, ronnilml transverse furrow, which pause's around slightly in front of the middle of the space parallel to
the anterior and antero-lateral margins. Cheek* convex, and sloping towards the lateral and autero-lateral bor-
ders. (Surface and facial sutures unknown.)

Length of cephalic shield, measuring from the posterior side of the neck segment to the front margin, 0.57 Inch ;
greatest breadth, measuring across at the posterior extremities of the cheeks, 0.87 inch ; height, 0.31 inch. Length
of glabella, including the Deck segment, 0.40 inch ; breadth of glabella, 0.35 inch.

D

^^^ ^^^ llrld of« Tounf

Proal* view of haul. \M I I indindu.i

Agraulut (lietnl.

A. Side view of a cephalic shield of Ayrattloi Owtni, the position of the eyes (which have not been distinctly seen)
Indicated by a dotted line.

/.'. Another view of the same, and of a sin.ill pygidinm supposed to belong to the name species, with the body restored
in outline. In this cut the marginal furrow pausing around the front of the head is made to terminate rather
too abruptly on each side; while the lateral furrows of the glabella are Indicated too distinctly. In the
specimens these furrows are very obscure, and it is difficult to see whether there were only two, or more on
each side.

I'. Head of a young individual, same species.

Tlu> only specimens of this species yet obtained are casts, which show no traces
of the sutures, and retain no remans of surface <rraiuilations, stria>, or other mark-
ings, if there ever were any. Nor are they in a condition to show whether or not
the jxjstero-lateral extremities of the hueklcr are pointed, though they probahly arc.
At a point nearly opposite the middle of the glahella, there is on each cheek, less
than half way down the slope from the furrow l>etwcen the fixed cheeks and the
glahella, the remains of a small eye, though the specimen heing unfortunately a
little defective here on both sides, the exact form of these prominences cannot
be clearly made out.

In the same slab containing the cephalic shield above descrilx-d, we observe a
p)gidium which probably belongs to the same species. It is sub-semicircular in
form, moderately convex, and rather distinctly, as well as nearly equally trilobate.

2 February, 1864.

10 PALAEONTOLOGY OF THE UPPER MISSOURI.

Its middle lobe is more prominent than the lateral, and shows three segments ; the
lateral lobes appear to have only two segments.

Compared with Prof. Barrandc's beautiful figures of the variable typical species,
A. ceticephalus, of its own size, the head of our species is more regularly rounded
in front, and differs in having a distinct anterior marginal furrow, while its glabclla
is proportionally longer. A specimen of a much smaller individual in the same
matrix, shows this species to have been also much less variable in the characters
just mentioned, at different periods of its growth, than A. ceticephalus. Again, if
the pygidium mentioned above belongs to the species under consideration, it was
larger in proportion to the largest head we have seen, than in the European species.

Dr. Shumard and Mr. Billings, to whom we sent sketches of our species, regard
it as being clearly distinct from any of the forms described by either of them from
the Primordial rocks of Texas and Canada.

As the specimens of this Trilobite came in after our plates were made up, we
could not well introduce figures of it there, but the annexed wood-cuts will give a
tolerably good idea of its general appearance.

Locality and position. Near the head of Powder River, in the Big Horn Moun-
tains, Dakota Territory. From the Primordial or Potsdam Sandstone Group. No.
1180, collection of the Smithsonian Institution. (Type 1180a.) Discovered by the
Exploring Expedition under the command of Captain William F. Raynolds, U. S.
Topographical Engineers.

Agraiilos?

(PLATE I, Fig. 4.)
Comp. Crepicephalux, OWEN, Report Geol. Wisconsin, Iowa, and Minnesota, 1852, PI. I. A. Fig. 18.

The specimen of this species we have figured is an internal cast of a part of a
cephalic shield, in a coarse brown sandstone. It is not in a condition to show any
traces of the facial sutures, or even the form of the entire glabella, nor the position
of the eyes, if they exist. Hence we cannot determine with much confidence to
what genus it belongs, nor can we give any characters by which the species can be
identified. As near as can be determined, it seems to be similar to some of the
forms figured by Dr. Owen under the name Crepiceplialus. It also resembles the
foregoing species from Big Horn Mountain, and may possibly be the same. Still,
as it presents some slight differences, it may prove to belong to another species.
Although a mere fragment, we have thought it should be figured, since, as far as
its affinities can be made out, it corroborates the evidence of the other fossils in
regard to the age of the formation.

Locality and position. Central part of the Black Hills, Dakota Territory. Pots-
dam or Primordial Sandstone. No. 1024.

CARBONIFEROUS AGE. 11

CARBONIFEROUS AGE.

(CABBOJUFEROl'8 PERIOD.)

PROTOZOA.

CLASS KHIZOPODA.
ORDER Forauiiiiifcru.

FAMILY GAMERIXID^E.

Shell comparatively large and dense, discoid, lenticular, fusiform, cylin-
drical, oval, or subirlobose in outline; syiumctrically involute, or nircly
somewhat obliquely spiral. Last volution generally embracing all the
others, so as to present, in the typical genera, the form of an Ammonite or
.\uiitihix. Septa nearly always double, each chamber having its own
walls, which, without exception, diller from the rest of the shell in beiui;-
destitute of the ordinary tubular structure, so that the chambers are only
connected by the principal aperture, and a few large " orbuline" pores.
Canal system radiating between the double walls of the septa, generally
well developed and connected with the "intermediate skeleton," secreted
apparently for the consolidation of the entire structure. Aperture in the
typical forms a narrow fissure placed symmetrically between the outer
wall of the penultimate whorl, and the inner side of 'the last or outer
series of chambers ; sometimes partly closed by a shelly secretion so as
to leave only a series of pore-like openings; in Ampkittogfaa placed on
the under side of the spiral plane.

In Dr. Carpenter's beautiful and elaborate Memoir on the Fora mini/' m,1 pub-
IMird by the Ray Society, in 1862, the genera included in this family (there called
Xiniiiiitiliniila) arc the following, — in part, however, under other generic names,
viz.: Camerina, — (Atimwiti/i/es, Lamk.) Amphisteyhm, OjH ,;-u/iini, Kl/>/tidium,=
(PolystotneUa, Lamk.) ffeterofitcgina, Cycloclypeus, Orbitotdes and Funilina. It in-
cludes the largest and most highly developed of the Foraminifera, as well as those
possessing the most densely constructed shells. The living examples are mainly
confined to the tropical and temperate seas, the larger types occurring in the tropics.

In regard to some of the names here adopted, a word of explanation may not
be out of place. First it will be observed we use Bruguicrc's name

« To which we arc mainly indebted for the characters given in the above description.

12 PALEONTOLOGY OF THE UPPER MISSOURI.

instead of Nummulites, Lamarck, or Niimmulina, D'Orbigiiy ; and as this is usually
considered the typical genus of the family, we have adopted the family name
Camerinidce, instead of Nantiloida>, or Nummulimdw. Our reason for restoring
Bruguiere's name, is, that it has priority over all the other regularly proposed
genera. It was also adopted by Cuvier, in 1798, as well as by Lamarck himself in
1799,1 and of course previous to the publication of Nummulites and Nummulina.
This will be better understood by the following glance at the history of the genus: —

Previous to the introduction of the binomial nomenclature by Linna?us, these
fossils were known to the early writers by such specific phrases as " HeUcitcs niger
foliolis candidus," " Pierre lenticulaire," " Nummi lapidi," " Pierres numismaliq," &c.
In 1792, however, Bruguiere proposed for them the generic name Camerina (Encyc.
Moth. I, 396), giving at the same time a tolerably good description and history of the
genus, occupying three and a half of the quarto pages of the Encyclopedia, followed
by descriptions of the four species — Camerina-lceviyata, C. striata, C. tuberculata, and
C. nummularia — all of which have been recognized by the later writers as belonging
to the genus subsequently named Nummulites, by Lamarck, and still later, Nummu-
lina, by D'Orbigny. It was in his Syst. An., published in 1801, page 101, that
Lamarck first proposed the name Nummulites, adding little or nothing to what Bru-
guiere had published. In 1804 (An. Mus. V, 237), he ranged Bruguiere's species
under the new generic name Nummulites, with very nearly the same descriptions, and
references to figures and descriptions of previous authors given by Bruguiere, as lie
did again in 1826 (An. sans Vert., VIII, 627). In 1825, D'Orbigny, supposing
the genus had living representatives, gave a third name, Nummulina. At various
times other names were proposed for this group by other authors, but as none of
them antedate Bruguiere's, and they have all been dropped out of use, they have
no bearing on the question of priority, and need not be cited here.

Now we cannot recognize any right or authority for the changes made by
Lamarck and D'Orbigny. Surely it cannot be urged that Bruguiere's erroneous
opinion in regard to the affinities of the Foraminifera is a reason for setting aside
his name, when Lamarck and D'Orbigny also classed them with the Molhisca.
But even if they had discovered the true affinities of the genus, or of the order to
which it belongs, this would not have given them the right to change a regularly
established generic name ; for if we admit such a rule, there would be no end to
changes, since natural history is constantly advancing, and improvements in the
classification of animals and plants are continually being made, and may be ex-
pected for a long time to come, as the affinities of the various groups are better
understood. Such a rule, for instance, would have given Dujardin the right to
change the names of all the genera of the entire order, when he in 1825 discovered
that the Foraminifera are not Cephalopoda, nor even Mollifies at all, but Protozoa.

Nor can we admit D'Orbigny's right to change Lamarck's name Nummidites (had
it been well founded) to Nummulina, if he had found a living species of the genus :
since it has many fossil species, and it would be an absurdity to designate the
living species of a genus by one generic name, and the fossil species by another,
while the name most applicable to the fossil species has priority. Does any Con-
chologist, for instance, think Swainson's name Volutilithes should be changed

1 See Prodr. p. 80, where his only cited example is C. Isevigata, Brug.

(A U CONIFEROUS A(JK. 13

because a living species .if that ^roup was found at tin- CajM? of Good Hope '. Or.
if a naturalist should dredge up from the bottom of sonic unexplored sea, a living
Ammonite, \\oiild l'ala-ontolo^i>ts admit his ri^lit to change tlic name of tin- genus '.
The oilier instance where we have restored an older name, is in adopting
J:'/]>/tiiIii/in, Montfort, instead of J^li/xlonii II, t, Lamarck, Mont fort's name having
lieeu published in Isos, in his('onch\l. S\>t.. \"ol. I, pp. 14-15. It is true, not
\er\ much can lie said for his figure or di-scriiition, hut as he refers to the figures
and description of Yon Fitdiell and Yon Moll, so that later authorities do not
hesitate to identify the t\pe of his genus with : s of /'o///.-.V«m<//«, I.amarck.

which name was not published until IS'J'J, we feel hound to adopt his name. The
fact that he -,'ave some ti\e or six oilier generic names to other species and varii ti. ^
of the same genus on subsequent pages of liis work, does not alter the rase, for it
matters not how many names an author may give a genus, we are bound to adopt
hi> lii-st. name, if not pre-oceupied, and his t\pe can lie identified, and (lex's not
belong to a previously described genus ; the subsequent names of course falling
into the list of synoimns.

Genus FUSULINA, FISCHER.

Sg*on.— Futvlino, FiariiPH, Oryet. du Gonv. de Moecoo, 1837, p. 126.— D'OBDIO.IT, ID Mun-liiMm. Wrneuil A Kejrser-

ling's Geol. RUM. II (part ill, Pal.), 1845, p. 15.— Cosu., KU-iuent. de Geol. Str»l., II, 18f.2, 109.
liorrUt (ap.), EiiBE.MiKuii, Berliu Moiuttsb. 1842, 274 (not Montfort, 1808).
Elym.—funa, a spindle.
Type. — Ftaulina eylindriea, FISCHER.

Shell regular, equilateral ; fusiform, cylindrical or subglobose, according to its
greater or less elongation in the direction of the axis, sometimes constricted
around the middle; symmetrically involute so that each turn envelops all the
preceding at all stages of growth. Surface with nearly parallel, subequidistant
furrows coincident with the septa within, and running in the direction of the
axis. Aperture a narrow slit confined to the central region. Foramina passing
through the external walls of the chambers, of moderate size. Septa compara-
tively narrow in the middle, and gradually widening towards the extremities;
apparently composed each of a single lamina; regularly undulated laterally, so as to
partly subdivide each intervening chamber on each side of the broad mesial avenue
(connecting the different chambers) into a series of small alternately arranged cells
connected together by narrow galleries. Internal canal system, and "intermediate
skeleton" apparently wanting.

The shells of this genus present the various modifications of form, and much the
general appearance of the genus J/<W//m, from which, however, they can be
ily distinguished by their aperture consisting of a single mesial slit, instead of
a single or multiple series of round or oval openings extending along the entire
length of the shell. They also differ entirely in their internal structure, the differ-
ent chambers in I-',I*H/;II>I being connected with each other by the single broad
slit corresponding to the aperture in the last or outer septum, and not sub-

14 PALAEONTOLOGY OF THE UPPER MISSOURI.

divided by revolving septa; while in Ahcolina there is another system of sub-
ordinate septa crossing the longitudinal scries at right angles, and thus forming
a complex system of chambciicts connected by openings passing through the
principal septa, and corresponding to the numerous apertures in the last or outer
septum. The surface in Alvcolina is also marked in addition to the longitudinal
furrows, by another series of smaller revolving linear depressions, coincident
with the series of secondary septa. We observe Dr. Carpenter speaks with some
doubt in regard to the foramina in the walls of the shells of Fusulina, though
he thought he had seen indications of them. On making a transverse section
of one of our Kansas specimens, we were enabled to see these foramina distinctly,
under a high magnifying power, by transmitted light. Fig. 6, c, PI. I, illustrates
their appearance. We saw no satisfactory evidences of an intermediate canal
system, though some of the septa seemed to exhibit slight indications of being double.

So far as known, the genus Fusulina is mainly, if not entirely, peculiar to the
Carboniferous System.1 In the Old World, it seems also to occur only in the Sub-
carboniferous Series, particularly in Russia. In this country, however, at any rate
east of the Rocky Mountains, it has only been found in our Coal Measures. It is
represented by one or more species, in great numbers, in the Coal Measures of
some of the Western States, particularly in southeastern Nebraska, western Iowa,
eastern Kansas, and portions of Missouri, Arkansas, Texas, Illinois, and, according
to Mr. Verneuil (Am. Jour. Sci. (2) II, 1846, p. 293), in Ohio.

A species (F. hyperLorca, Salter) was discovered in carboniferous rocks as high
north as 76° 30', at Depot Point, Albert's Land.

Fusulina cylindrica

(PLATE I, Fig. 6, a, b, c, d, e,f, g, h, i.)

Fusulina cylindrica, FISCHER, Oryct. du Gouv. de Moscou, 1837, 126, pi. xviii, fig. 1-5.
Fusulina depressa, FISCHEK, ib., pi. xiii, fig. 6-11.

Fusulina cylindrica, MEEK & HAYDEN, Proceed. Acad. Nat. Sci. Phila. December, 1858, 260.
Fusulina cylindrica, var. ventricosa, MEEK & HAYDEN, ib., 261.

Shell fusiform, more or less ventricose in the middle, somewhat obtusely pointed at the extremities, which
generally have the appearance of being a little twisted. Surface smooth excepting the septal furrows, which are
moderately distinct, more or less regular, and a little curved as they approach the extremities. Aperture rather
short, very narrow, and rarely visible as specimens are usually found. Volutions six to eight, closely coiled, the
spaces between (near the middle) being rarely more than twice the thickness of the shell walls. Septa from
twenty to about thirty-three in the last turn of adult specimens, counting around the middle ; comparatively
straight near their outer margins, but strongly undulated laterally within. Foramina passing through the outer
walls of the chambers, distinct in well preserved specimens ; as seen in transverse sections near the middle of the
shell, somewhat radiating, and numbering in the outer turns of a medium sized shell, from twelve to twenty
between each two of the septa.

Length (of a slender specimen), 0.37 inch ; diameter, in the middle at right angles to the axis, 0.13 inch.
Length (of a ventricose individual), 0.38 inch ; diameter at right angles to the axis, near the middle, 0.20 inch.
Types of figures and description, 1029, 1028.

The little shell described above, agrees so nearly with the figures and descrip-
tions of Fusulina cylindrica of Fischer, that we are at a loss to find constant

1 Dr. Shumard describes a gigantic species attaining a length of two inches, from rocks in Texas
supposed to be of the age of the Permian System of Europe (see Trans. St. Louis Acad. Sci. I,
397). From the description, however, we should suspect that it may belong to an allied, but distinct
genus, since the aperture is said to extend the entire length of the shell.

CARBONIFEROUS AGE. 15

characters by which it oau be separated from that species; at any rate by the
figures and descriptions we ha\e \et seen. Still it is not improbable that a direct
comparison with specimens of the Russian species would enable us to point out
characters by which they could be distinguished. At one time we supposed that
some \entricose specimens found by us in Kansas, might be separated as a variety
from the more common slender forms; but further comparisons have satisfied us
that they cannot be regarded as a sufficiently marked variety to make it desirable
to designate them by a different name, there being every gradation between these
t\\o extremes. In case they should all, however, prove to be distinct from Fischer's
species, the name veniricosa may be retained for the American type.

Lomliti/ inn! jM,sition. — The species here described ranges from Ohio to Kansas
and southwestern Nebraska, and south to Texas. It seems to be more common,
however, west of the Mississippi than east of it, and we have no knowledge of its
existence east of Ohio. *It probably occurs in western Kentucky, though we have
never seen specimens of it from that State. It is common in portions of Missouri.
At all the localities mentioned, it is found only in the Coal Measures.

The specimens here figured and described are from Juniata, on Kansas River,
Kansas, where it occurs in great numbers.

16 PALAEONTOLOGY OF THE UPPER MISSOURI.

MOLLUSCA.

CLASS BRACHIOPODA.

FAMILY SPLRIFERID^E.

Shell free, inequivalve, varying greatly in form and ornamentation
according to the genera and species ; with or without a cardinal area ;
oral appendages large, provided with calcified, ribbon-shaped supports,
which are spirally coiled so as to form two cones^ the apices of which
are directed outwards towards the lateral margins of the valves. Shell
structure fibrous only, or fibro-punctate.

Animal unknown, apparently sometimes attached by a muscular
peduncle.

Paleontologists generally place in this family all the Brachiopods known to
possess calcified spiral oral appendages, however these appendages may be arranged
or attached. We agree with Mr. Woodward and some others, however, in sepa-
rating from it the genus Atrypa, which differs from the other genera usually placed
in this family, in having the cones formed by its spiral oral appendages placed with
their apices directed vertically instead of laterally, thus apparently indicating
affinities to the Rhynchonellidce (probably also including Stenocisma1 and Oceloepira),
in which the fleshy oral arms are similarly arranged.

The great differences of form and other characters presented by the other genera
usually embraced in this family, render it also highly probable that they belong to
more than one family ; but as we can scarcely ever hope to know enough of the
affinities of these extinct genera to successfully separate them, it is not probable
that any attempt of that kind would meet with much favor. The entire family is,
so far as known, extinct, and none of the genera appear to range above the Lias.

The groups falling within this family, as here defined, are Trigonotreta, Martinia,
Spirifina, Spirifer, Syrimgoihyrie, Cyrtina, Suessia, Trematospira, Sjnrigera, Merista,
Pentagonia,2 Nudeospira, Uncites, Retzia, Rhynchospira, Acambonia, &c.

1 In the Fifteenth Report Regents University of N. Y., 1862, p. 154-5, Prof. Hall proposes the
name Zygospira for a genus of which Producta modesta, Say, is the type. It seems, however, that
Mr. Conrad had suggested for this shell the generic name Stenocisma; which Prof. Hall proposed in the
first Vol. Pal. N. Y. (1847, p. 142) to adopt, should this type prove to belong to a distinct genus. As
there was, therefore, no necessity for a new name, Stenocisma will have to take precedence over Zygospira.

* The name Pentagonia was proposed by Cozzens, in 1846 (Ann. Lye. N. Hist., N Y., IV, p. 158),
for a genus, or subgenus of peculiar angular Meristoid shells, of which Pentagonia unisulcata
(= Atrypa unisulcata, Conrad, = Pentagonia Persii, Cozzens, = Meristella (Gonioccelia) unisulcata,
Hall) is the type. In 1861, Prof. Hall suggests the name Gonioccelia for the same type (Fourteenth
Rept. Regents University of N. Y., p. 101). Cozzens' name having priority, however, must be adopted
for the group, whether we consider it a genus or a subgenus.

CARBON I I'KROUS AGE. 17

(i.nus S1MKIFER, SOWERBY.

Sy*o*. — Ifyitrroliln, Anomitrt and Terrl,rntulilti (part) of early author*.

/ .'.r<i/u/,i (part), LAMAK. K, I'rodr. 1799, 85 (not of author* generally).

r./rr, SUWKUHT, Miii. Conch. II, 1815, 42.
Triyo»oir,t:,, K.KMO, loon. Beet. No. 70, 1825.— Bmoxx, L«lh. Qeog. 1837, 77.— KMO (put), Monog.

IVrui. FOHH. Kuglaud, Is.'.o, 11;,;.

f 'A..ri.</i'fr*, KIHCUER, Prodr. «nr le Chorii-tites tloto. 1825, xx.
/'.//Ayr". DALXAH, Kongl. Vet. Ac. Handl. 1827.

•i, D ALMAS, ib., 1827.

>>//-i/rr.i, SOWIBBT, Ind. to Min. Con. 1825 ; and of several later author*.
'i«i'.i, McCor, Synop. Carb. FOM. Ireland, 1844, 139.
«/«ri« (part), McCoi, ib., 142.

Itrackjtkyru, Mct'oT, Ib., 144.

Ambocalia, HALL, Thirteenth An. Rept. Regents Unirenlty of N. Y., 1860, 71.
t'tymol. — Spira, a spire ; frro, to bear. •

Type. — Sjiiri/er cutjiiilatui, SOWE

Shell more or less triangular, semicircnkr, transversely elongate, or subglobosc,
with or without a mesial fold and sinus; lateral margins rounded, angular, or
sometimes produced into mucronatc, wing-like extensions ; structure impunctate ;
surface plicate, costute, striate or smooth — sometimes roughened by minute
granular or spinous projections. Cardinal line straight, as long as, or shorter
than, the greatest transverse diameter of the valves. Hinge articulated by short
teeth and sockets, and provided with a more or less developed cardinal area in
each valve ; that of the ventral valve being larger than the other, flat or arc-lied,
and generally inclined back over the hinge— divided by a triangular foramen
usually more or less (sometimes entirely) closed by a false deltidium, which is
occasionally pierced by a small circular or oval aperture near the beak ; area of
dor>al or smaller valve narrow, often linear, divided in the middle by a wide open
fi-Mire which is partly or entirely occupied by the cardinal muscular process.
Beak of ventral or larger valve more prominent than that of the other, incurved or
more or less nearly straight, that of the smaller valve short, and nearly always
incurved,

In the interior of the dorsal valve the large spiral supports of the labial arms are
attached by their crura to the hinge plates, some distance from which they are
nearly or quite connected by a small process extending inwards from each. The
cardinal muscles seem to have been attached to the cardinal process, under, and in
front of which, the four large scars of the adductor muscles occur. In the larger
or ventral valve the cardinal teeth are placed one on each side, and at the base of
the foramen, and fit into corresponding sockets in the other valve; beneath the
hinge these teeth are supported by the strong dental lamina*, which vary much in
size and form, according to the species, and arc supposed to have received on their
inner sides the muscles of the peduncle. A considerable portion of the central
region of this \nl\e is occupied by the muscular MtM, which are generally divided
by a mesial ridge. Immediately on each side of this ridge occur the small longi-

3 March, 1864.

18 PALAEONTOLOGY OP THE UPPER MISSOURI.

tudinally oval scars of the adductors, and outside of these the scars left by the
cardinal muscles.

Some difference of opinion exists in regard to the particular species that should
be considered the type of this genus. Most authors have fallen into the habit
of viewing Spirifer striatus as the type, mainly, we believe, because Sowerby first
discovered internal spiral appendages in that species, and had announced this dis-
covery before the Linnsean Society in a paper read in 1814, but not published until
during the following year, about the time the second volume of his Mineral Con-
chology, containing his description of the genus Spirifer, issued from the press. It
is worthy of note, however, that he does not propose, in this paper, to establish a
new genus upon Spirifer striatus — (which he there designates by the old name
Anomia striata) — nor upon any other species, though he does allude to Spirifcr
cuspidatus, in a foot-note, appended some time between the reading and publication
of the paper, as being figured in his Mineral Conchology as " Spirifer cuspidatus"
So that even admitting that this paper was distributed a few months earlier than
•the second volume of his Mineral Conchology, Spirifer cuspidatus would still be
the first species in connection with which we have any evidence he ever .used the
name Spirifer. It is also the first and only species described by him at the time
that he founded the genus in the second volume of his Mineral Conchology, while
he there makes no allusion whatever to the species striatus. It has been objected,
however, that he admits in his remarks after the description of S. cuspidatus,
immediately following the description of the genus Spirifer, that he only inferred
from analogy, that this species possessed internal spires. In this inference, how-
ever, later discoveries show that he was correct; so that the name Spirifer, as well
as all the characters mentioned in his description of the genus, arc as applicable to
S. cuspidatus, as to the species striatus. Hence we think that in accordance with
the laws of priority S. cuspidatus should be regarded as the type of the genus.

We are not, however, in favor of so rigidly carrying out this rule as to invariably,
and under all circumstances, regard the first species mentioned or described in con-
nection with a new generic name, as its type, especially when that particular
species may happen to present some important characters directly opposed to those
given in the generic description, while another species described at the same time
does exhibit these particular characters. But when an author describes a new
genus, and at the same time describes but a single species, which presents all the
characters given in the description, although he may have only inferred from
analogy that it possessed some particular one of those characters he had not seen,
we are compelled to regard that species as the type of the genus. The fact that
he may have at some previous time seen this character in another form subse-
quently referred by him in another volume to the same genus, as Sowerby did with
Spirifer striatus, cannot, we should think, invalidate the claims of the first species
(S. cuspidatus') to be regarded as the type.

If we are right in these conclusions, Dalman's name Cyrtia becomes exactly
synonymous with the genus Spirifer, since it was founded for the reception of
species possessing precisely the characters of the typical forms of that genus ; while
the species usually viewed as typical Spirifers, must form a distinct sub-generic or

CAUHOXIFEIIOUS A(J K. 19

generic group, to which Kimig gave the 11:11111- Tri<j«ii»trtl^, subsequently adopted
liy Trot'. Bronn, :ind \>\ Prof. King.1

\- lii-n- <li 'lined and t> pitied, it will lie seen that tlii^ i;eiiii- inelndo two rather
marked sections, with one or more le.>s distinctly detined groups, \shich maybe
characterised as follows: —

1. Spirifer (proper), SUWUBT, — Cyrtla, DALMAIC, and othert.

SI,. -11 trigonal, nearly always cosUte or strlate ; hinge generally a little lest than the breadth of the valves,
more or less angular at the extremities ; ventral valve very prominent or pyramidal ; beak straight or a
little . iir. . I ; ar«a Urge and triangular; foramen closed by a fal»e dvltidium, generally pierced by a imall
round or oral aperture near the apex of the beak ; dorsal valve comparatively compressed, semicircular.

'£. Trieoiiotrt-tn, Kouuo,— ftpirifcr, of most authors.

S1..-11 usually with both valves convex, marked as In the fort-going; lateral extremities generally angular,
often acutely so ; hinge line usually extended. Roth valves with beaks more or leas incurved ; area
variable in size, but rarely if ever so extravagantly developed as In some of the typical Spirifen ; foramen
open or more or lens closed by a false deltldinm without a perforation.

J-'.rumple. — £pirif<r ilriatui, SowxBBT.

8. Murtjnia, McCoy, — Amboratia, HALL.

Mi. II snbgloboae, or transversely or longitudinally oval, smooth or rarely with compressed rounded OOHUB;
often beset with minute hair-like spines. Hinge short, scarcely ever equalling the greatest transverse
diameter of the valves; lateral margins rounded, or rarely obtusely angular; beak of ventral valve
incurved ; cardinal area comparatively small ; foramen, and false deltidlnm as in Triyonolrela.
Type. — $pirif< r ylabrr, SOWEBBT.

The genus A)«Y//I /•//»< of D'Orhigny, is also often considered a subgcnus under
>/»//•//;/•. The coincidence, however, of a punctate structure in these shells, with
the presence of a prominent mesial septum in the ventral valve, would seem to
indicate important differences in the structure of the animal, such as would warrant
its separation as a distinct genus.* So also with Ci/rliini of Davidson, which was
formerly included with the forms we here regard as the typical Spirifcrs, tinder the
name ( ';/rt'«i. Mr. Davidson has, however, very properly separated these shells, on
account of their punctate structure, and the peculiar development of the dental
laminae of the ventral valve, which are produced inwards, and coalesce into a single
me-ial septum, extending from the extremity of the beak, almost to the anterior
margin, thus giving the interior more the appearance of Pt-ntamerus than Spirifer.
As Mr. Hillings has, however, discovered internal spiral appendages in one of these
shells, and they all possess a well-developed cardinal area, we cannot doubt the
propriety of including them in the A///V/A riitn •, though we think, as above stated,
that they should constitute a distinct genus from all the other groups.

As thus freed from the punctate species, the typical Spirifers (= Cyrtui, Dalman)
are found to pass by such insensible gradations into the Trigonotreta group (= the

« In his valuable work on the Permian fossils of England, Prof. King regarded Spirifer cuspidatus
as the type of the genus, and adopted Kocnig's name Trigonutreta for the shells generally considered
typiml Spirifers. It is said, however, that he subsequently changed his views in regard to the type
of Spirifer.

1 I avail myself of this opportunity to refer to the genus Sfririferina, a species described by me
timli-r the name of Spirifera pulchra (Proi-cod. Acini. Nat. Sci. July, I860, p. 310), brought liy
Ciipt. Simpson from Nevada Territory. Sections of it show very distinctly a coarsely punctate, very
flm-ly fibrous structure; while casts of the interior exhibit a deep slit left by the mesial septum in the
l>cak of the ventral valve — F. B. M.

20 PALEONTOLOGY OF THE UPPER MISSOURI.

usual type of Spirifer as generally understood), that we cannot see how the
can be separated more than as sections or subgenera.

It will therefore be seen, that in our present state of knowledge, -it seems to be
most natural to exclude entirely from the genus Spirifer, all the punctate species.
Entertaining these views, it becomes necessary for us to explain why we have placed
Ambocoelia, which has been described as " fibrous (or fibro-punctate)" with " lustre
pearly," as a synonym of Martinia, one of the sections of Spvrif&r.

Our reasons are, in the first place, that we see nothing in the form and external
appearances of the type of this proposed genus, to separate it from Martinia ;
especially since the closely allied Amboccelia gemmula, of McChesney, which was
also included by the author of Amboccelia in that group, sometimes has its dorsal
valve a little convex — indeed occasionally as much so as the scarcely distinguishable
European Spirifer Urei and S. Clanyanus — though it is more frequently flat or
concave as in the type of Ambocoelia. Again, we know from an examination of
New York specimens of the type of Ambocoelia, in the collection 'of Mr. Worth en,
State Geologist of Illinois, that it has internal spires arranged as in Spirifer.
Thinking, however, that the punctate structure, and the supposed pearly lustre
of this type, might warrant its separation, we subjected authentic specimens of it
from the Hamilton Group, New York, to a careful microscopical examination, both
in polished sections, and in thin broken fragments, and although we could distinctly
see the usual fibrous structure so generally characteristic of the Brachiopoda, we
failed to detect any traces of perforations, even by the aid of a high magnifying power.

In regard to the lustre, we think the word "pearly" must have been inadvertently
written, or wrongly printed, for although fractured surfaces of this shell present a
shining, somewhat silvery appearance, not unusual in the shells of fossil Brachiopoda,
it cannot be said to be pearly, as that term is usually understood by Conchologists.

From these facts we do not feel prepared to admit Ambocoelia even as a distinct
section from Martinia, until some more reliable differences can be pointed out.

The genus Spirifer, as here characterized, commenced its existence during the
Lower Silurian epoch, and ranges through the more modern formations into the
Triassic rocks.

Spirifer (Martinia) pla no-con vexns.

Spirifer plano-convexus, SHUMARD, Report Geol. Survey Missouri, 1855, part Palieontology, 202.

Amboccelia gemmula, McCnEbNEY, New Palaeozoic Fossils, 1860, 41.

Amboccelia yfmmula, HALL, Thirteenth Report Regents University, N. Y. 1880, 71.

Comp. Sp. Urei, FLEMING, Brit. Animals, 1828, 376.

Shell small, plano-convex or concavo-convex, young individuals usually longer than wide, adults wider than
long ; hinge line always shorter than the greatest transverse diameter of the valves ; lateral margins and front
rounded ; surface apparently smooth excepting a few concentric marks of growth — but when examined with a
magnifier, it is sometimes seen to be beset with the bases of minute hair-like spimiles. Dorsal or smaller valve
slightly convex near the beak, but usually concave around the front and antero-lateral margins, especially in
adult individuals ; trnnciito-orbicular in outline, usually very faintly depressed at the middle of the front ; beak
very small, not incurved, nor projecting beyond the cardinal margin ; area about half as wide as in the other
valve, flat, and standing nearly at right angles to the plane of the valve ; foramen extending to the beak. Ventral
valve strongly convex, sometimes very faintly flattened along the middle, but without a mesial sinus ; beak very
prominent, gibbous, and distinctly arched back over the hinge ; area moderate, triangular, arched, well defined,
and generally longer on the hinge side than the lateral margins ; foramen usually higher than wide, provided with
slightly raised lateral margins, not closed (so far as known) by a pseudo-deltidium. (Muscular impressions
unknown.) Spiral appendages each consisting of six or seven distant turns.

CARBONIFEROUS AOB. 21

Length of a Urge in.lmdual, O.:il inch ; breadth, 0.36 inch; conrexity, 0.23 inch. Longth of a young shell,
.2T iuoh; breadth. O.£l inch; courexity, 0.15 inch.

a b e

d •

Spirtfrr (Mnrlinia) plamo-rnnvtrui.

a. Side riew of medium iiied specimen, i. Ventral view of same, e. Donal rl«w of tame. d. Donal riew ot a
larger transverse specimen, showing the area and foramen, t. Hinge and internal view of a separated ventral.

This little shell seems to agree exactly with the species described by Dr.
Shuinanl under the name .V////-/A /• />/rr/<o-<-o/«r.r»«, and by Mr. McChesney, as £
iji iinniilii, excepting that none of the (twenty or thirty) specimens we have seen
show the taint medial depression or sinus in the ventral or larger valve, mentioned
by these gentlemen. As some of them, however, show a very slight flattening of
the inidille of this valve, it is probable other individuals may possess an obscure
narrow sinus. It is worthy of note that the descriptions given by these gentlemen
agree quite as well with the European S. Urei, and we arc strongly inclined to the
opinion that the form described by them, as well as that now before us, really belongs
to that well known species. Still, as our specimens nearly all differ from all the
figures of that species we have seen, in having the smaller valve, especially in adult
examples, a little concave, and the ventral valve destitute of a mesial sinus, while
they attain a much larger size, we have concluded to place them provisionally under
Dr. Shnmard's name i>l<mtnxnrexuA.*

As the closely allied Spirifer (JfiwfMMa) itmlxmatus (= Orthis nmbonata, Conr.),
I'm- \\ liich the new generic name Aniloccelia has been proposed, is described as having
a " fihro-pnnctate" structure, we examined the structure of the species under con-
sideration \ er\ carefully, by transmitted light under a high magnifying power, to see
if we could detect the presence of punctures ; but after repeated trials we failed to ob-
serve any traces of them, though we saw distinctly the usual fibro-prismatic structure.

LucnUh/ iiinl jH>x!iii>n. — Manhattan, on Kansas River; Upper Mill Creek, and
at \arious other localities in Eastern Kansas. Coal Measures. (Type of descrip-
tion and figures, 996, a, 6, e.)

•

FAMILY PRODUCTION.

Shell free or attached by the substance of the beak, concavo-convex ;
valves articulated by teeth and sockets, or retained in place by the action
of imiM-Irs only; hinge with or without a cardinal area; oral append;!
without calcified supports, and probably ileshy and spiral; surface more
or Ic^s spinous; substance fibro-punctate.

Animal unknown.

1 Since this was in type we linvr received a letter from Dr. Shnmard, to whom we had sent the cuts
of this species, in which he says he has uo doubt of its identity with his jS'. jilano-convexut.

22 PALAEONTOLOGY OP THE UPPER MISSOURI.

This family includes the genera Productus, Straplialosia, Aidosteges, and Chonetes.
It commences in the Silurian rocks, and ends with the Permian, being a strictly
Palaeozoic group.

Genus CHONETES, FISCHER.

Synon. — Pectenites, Pectunculttes, and Pectunculus (sp.) of tlie early authors.

Pecten, USE, Hist. Kuthenglen, 1793, pi. xvi, fig. 10-11 (not Miiller, 1770).

Jlysterolites and Terebratulites (sp.), SCHLOTH. Petref. 1820, 256, pi. xxix, fig. 3.

Productus (sp.), J. de C. SOWERBY, Min. Conch. IV, 1823 (not 1815).— BDCH (sp.), Abh. der K. Akad. Wiss.

1841, 33.

Leptcena (sp.), GOLDF. Germ. Tr. de la Beche's Geol. 1832, 523 (not Dalm., 1828.)
Chonetes, FISCHER DE WALD. Oryckt. Mosoou, 1837, 134.— KONINCK, An. Foss. 1843, p. 206. ; Id., Monogr.

M^moires Soc. Liege IV, 1847, 1. — GEINITZ, Grundr. der Verstein. 1846, 517. — HALL, Palseont. N. Y.,

II, 1852, 64.
Strophomena (sp.), HALL, Geol. 4th Distr. N. Y. 1843, 72 and 180.

Etym. — x""1) a lit*'6 DOX-

Examp. — Chonetes Dalmaniana, DE KONINCK.

Animal unknown. Shell transversely semicircular, concavo-convex, compressed,
greatest breadth usually on the hinge line ; area common to both valves. Ventral
valve convex, usually depressed along the hinge; area generally broader than
that of the other valve, and inclined more or less back over the hinge — angular
and armed along the margin with a row of tubular spines; foramen partly or
entirely closed by a false deltidium. Dorsal valve concave ; foramen replaced
by a prominent bifid or trifid cardinal process. Surface of both valves sometimes
nearly smooth, but generally ornamented by concentric marks of growth, and fine
radiating strise, or rarely large plications.

Hinge with two cardinal teeth, located one on each side of the foramen of the
ventral valve, and fitting into corresponding pits in the other. Interior of both
valves provided with a narrow more or less distinct mesial ridge, extending at
right angles from the hinge, part of the way across, between the muscular im-
pressions. Scars of the cardinal muscles in the ventral valve, ovate and somewhat
oblique ; those of the adductors very small, and placed between the impressions
of the cardinal muscles and the mesial ridge. Dorsal valve with four small
adductor muscular impressions, and two short linear hook-shaped vascular scars.
Interior of both valves more or less granulated.

This genus was introduced during the Lower Silurian Epoch, and continued its
existence at least to the close of the Carboniferous, in which it attained its maxi-
mum development.

Chonetes mucronata.

(PLATE I, Fig. 5, a, b, c. d, e.~)

Chonetes mucronata, MEEK & HAYDEN, Proceed. Acad. Nat. Sci. Phila. 1858, 262.

Compare C. Smithii, NORWOOD & PBATTEN, Jour. Acad. Nat. Sci. Phila. 1857, 24, pi. ii, fig. 2.

Shell rather large, compressed, semicircular, having its greatest breadth on the cardinal border, which is extended
into mucronate angles. Surface ornamented by a few subimbricating concentric marks of growth, crossed by very

C iRBOVl I i: i:ors .\ «E. 23

(Inc. i.l>»(-nrc, reeular, closely set radiating strlv, about one hundred and Hfly of which may b« counted around the
.> l.-n- fi.-l.i or mil.- of ti.i-m in-fiipy the »|«ce of one line.

Larger or dental valve depru««r<l, having usually a broad, very shallow undefined mesial depression extending
from tin- fiont toward* the Iwak ; cardinal margin armed with from eii;ht to twelre oblique spines on each side of
tli.- I .-.ik ; area of moderate l.r.-.i.lth ; deltoid a]MTtur« very broad snbtriangular, the upper angle being rounded
aixl the margin) more or leas projecting; impressions of cardinal munle tubovate, diverging, attenuate above;
allii t..r mus.-iilar Hears small, narrow, snbelliptical ; mesial ridge small, slight!/ prominent, and scarcely ever
reaching the im>l<lle of the valve.

l''.r-.-il or smaller valve following nearly the curve of the other; beak and central region concave; ears flat ; area
well developed but narrower than that of the other valve, provided with menial prominence, which, together with
tin' -mall bifld cardinal process projecting from its inner side, nearly or quite closes the foramen of the opposite valve.
r'r.'in the hase of thin process there are extending on the inside of the valve five radiating ridges, two of which pass
i.l.li.|ii.-ly oiitw.u.N alontf th« inner margins of the dental pits, while a third extends at right angles to the binge a
little nii'i.- t h.m half way across towards the front of the valve ; the other two ridges are much shorter and occupy
intiTiiieiliatH positions between the central and lateral ridges, and are directed obliquely outward and forward.
Interior of both valves more or less grannlote, the larger grannies being arranged over a semicircular belt a little
within the honliT, which latter is occupied by very fine radiating granulose stria.

Length, o.t;.' inch ; breadth on hinge line, 1.13 in.-h.

This shell is \( TV closely Allied to f'/nii,,t'» \;/< ///,/; of Norwood & Prattcn, and
may ])ossihl\ prove to be only a variety of that species. It differs, however, in
being generally much larger, rather more compressed, and proportionally longer on
tin- hinge line; its ear- are also often much more extended and pointed than those
of i'. SinitliH. Another difference is that the coarser granules of the interior seem
never to be scattered over the central region of the valves as in Norwood & Pratten's
speeiev Again, the area of is -mailer valve ranges more nearly at right angles to
the plane of the shell than in Illinois species.

Lof<i/i/i/ nnd position. — Near Fort Ililey, Kansas Territory. Coal Measures.
(Type 1066.)

FAMILY STROPHOMENID^.

Shell attached or free ; valves both convex, or one convex and the other
flat or concave ; hinge line straight, and provided with an area, which is
common to both valves, but usually wider in the ventral than the dorsal
valve : arms without calcified supports, being probably fleshy and spirally
coiled ; shell structure fibrous only, or fibro-punctate.

Animal unknown.

This family includes Orthis, Hemipronites, Klitambonites, Strophomena, Leptcena
and Tr<>i>i<l<>lt I'fiu. Some authors also include in it the genera Chonetes and
Porambonites, but, as Mr. Davidson has demonstrated, the former belongs to the
Productidff ; while the affinities of the latter remain somewhat doubtful.

This group presents one of the many interesting examples in the fossil world, of
an entire family, embracing several genera, and a great number of species, which,
after existing for immense periods of time, became entirely extinct, long before the
dawn of the present epoch. It is mainly a Pala?ozoic family, since it appeared
almost with the beginning of life, and became wholly extinct at the close of the
Permian period, excepting the genus /.</>/" mi, which continued to be represented
by a few species until about the close of the Liassic period.

24 PALAEONTOLOGY OF THE UPPER MISSOURI.

Genus IIEMIPRONITES, PANDER.

Synon.—Terebratuhtes (sp.), Senior. Akad. Munch., VI, 1816, 28.
Hemipronites, PAKDEB, Beitr. zur Geol. Russ. 1830, 75.
Klitambonites (part), PAXDER, 1830, Ib., 70.
Gonambonites, PANDER, Ib., 1830, 77.

Spirifer (sp.), PHILLIPS, Geol. York. 1836, II (not SOWERBT, 1815).
Lepttena (sp.), J. DE C. SOWEKBY, Min. Conch. 1840 (not DALMAN, 1828).
Orthit (sp.), POETLOCK, Kept. Geol. Lond. 1843, 456.— KONINCK. An. Foss. Belg. 1843, 222.— HALL, Geol.

Kept. I wa, I part ii, 1858, 640 and 713 (not DALMAN 1828).
Orthisina (part), D'ORBIONY, Compt. Rend. XXV, 1847, 267. — DAVIDSON, Brit. Foss. Brach. I, Gen. Introdnc.

1854, 104. Orthisina (sp.), SWALLOW, Trans. St. Louis Acad. Sci. 1, 1858, 219. — MEEK & HAYDEH, Proceed.

Acad. Nat. Sci. Phila. Dec. 1858, 260.— HALL, Thirteenth Kept. Regents University N. Y. 1860 (not

D'OKBIOHT, 1849).

Hemiprionites, AGASSIZ, Nom. Zool. Mol. 1846, 41.

Streptorhynchus, KING, Permian Foss. England, 1850, 107. — DAVIDSON, Brit. Permian Brachiopoda, 1857,
29. — HALL, Thirteenth Report Regents University N. Y., 1860, 112; also Sixteenth Kept. Dec.
1863, 61.

Etym. — Kpi, half; «•{»•», prominence.
Type. — Hemipronites tumidus, PANDEB.

Shell varying from truncatoorbicular to semicircular, or orbicular subquadrate,
more or less convex, the inequality of the valves varying greatly with the species ;
surface marked with radiating, generally straight striae, and sometimes with
rounded radiating plications. Hinge usually shorter than the greatest breadth of
the valves ; provided in the ventral or larger valve with two teeth, situated one
on each side of the mesial fissure, and fitting into corresponding sockets in the
other valve. Structure probably always impunctate.

Ventral valve with its beak more prominent than that of the dorsal, often bent
or twisted, but not regularly incurved; area generally high, sometimes extremely
so, its mesial fissure always closed, in adult shells, by a convex pscudo-deltidium.
Hinge teeth supported within by two dental plates, which converge under the area
towards the beak. Scars of cardinal and adductor muscles occupying about one-
third to one-half the length of the valve (between the beak and the middle), and
forming two elongated oval impressions, more or less deeply excavated, one on each
side of a mesial ridge or septum.

Dorsal valve generally with its beak compressed and projecting little beyond
the cardinal margin ; area usually very narrow or rudimentary. Cardinal process
large, prominent, and bifid; either slightly convex or concave on the inner side,
with each division more or less grooved or emarginatc at the extremity of the
outer side ; on each side of, and connecting with this, are the well-developed socket
plates. At the bottom of the valve the quadruple scars of adductor muscles occupy
about one-third the length of the valve, being arranged in pairs on each side of a
short mesial ridge.

The shells belonging to this group, although usually regarded as constituting
a section or subgenus of Orthis, present sufficiently marked differences to rank
as a distinct genus. In the first place they differ in having the foramen always

CARBONIFEROUS AGE. 25

cloxed liy a false deltidium, instead of being ojx'n, and hence they could
scarcely have l>cen attached !i\ a peduncle, unless it mav have been during the
carl) xt;i-, x nt' growth. Attain, they liavi> tin- beak of tin- ventral valve often
niurh more produced, and more or !«•-> twixted m- distorted as if from ha\ ing been
attached hy the substam ••• of the shell. They aKo have tin- dental lamina' of the
ventral valve lex-, prominent, and converging under the area towards the beak,
instead of extending further within the val\e. The cardinal process of tlic other
valve ix likewixe more developed, and the inner socket walls nnieh lexs so. A still
more important difference, if it should pro\e to be constant, as seems to be the
• •axe, ix tin- nierelv tiliroiis shell structure in this group, and the tibro-punctate
structure in O /•////*.

This genus has also been confounded with Klit*nnl*>n /'//.-•, 1'ander (= Orthisina,
D'Orb.). but Mr. Davidson hax sliown these two groups to be distinguished by well
detined external and internal characters. For instance, in KHtninlttmit&t there is a
well developed area, provided with a covered fissure in each valve; while in Ifemi-
j,,;,,iit>.-< ( Stn i>t<>rli >j iirh nx) the area of the dorsal valve is generally narrower merely
rudimentaiv. A^ain, in l\'lifiiinl»tn!tes the false deltidium covering the fissure of the
larger or ventral valve is pierced near the beak by a rounded or oval aperture never
seen in ILiiiifii -nnitt'K. The beak of the ventral valve of I\lil<tinlxniit»< likewise
differs in never being twisted, as we often see in Hemipronitee, and its area is
generally more inclined towards the front of the shell. In the former group the
cardinal pmeexs also differs in being formed of a single projection, with two small
lateral depressions, and is covered by the false deltidium; while in Ih >ni/> r< >nili A
tliix process is bilobate and exposed. These groups are likewise distinguished by
differences in the details of the musctdar impressions.

There are a few peculiar plicated shells, with a more or less distorted beak and a
liiyh triangular area provided with a closed fissure, found in the Coal Measures of
Kansas and New Mexico, which appear to form a section of this group, though
they may be generically distinct. Orthixina miiuxniriana and O. Muiin>ir<li<in(i, of
Swallow — as well as X/ri jifor/ii/iir/nt* t*'r!</, ntnH* and ,V. /-///•<///</</////.-, of Nevvlierry,
are American examples of this type. /'/•<*//«•///.•< ,.,•/////«* of Kichwald, from the
Carboniferous rocks of Russia, and >'//•//)/<,//<///,<////.•. /»ctini/ormis, Davidson, from
India, also belong to this plicated section.

This genus was first made known by Pander, in 1830, in the work cited in the
synonymy at the head of this description, under the name KKtambonUet. He in-
cluded, however, under this name, two groups regarded by him as subgenerically
distinct, the first of which he called Pronites, and the second 11< n<i/> /-(mites. The
tvpical species of his group Pronites (P. adscendent, Pander) being also the type
of the including genus Kliiii>iil*,ii!fc*, the name Pronite* must be regarded as merely
a xvnonvm of l\Ht,imbonitex, since it would be an absurdity to retain a separate
Mibgeneric name for the typical species of the including genus. In addition to
this the name Pr<>,,ii,x had been used in 1811 for a genus of birds b\ llligcr.

The species adscendenn, the type of h'/i/mnbonites, presents all the generic
characters of the group to which D'Orbigny subsequently gave the name Ort/ii^iim ;
while the typical species of the other supposed subgeuus, J/tiiiij>ni>u'lcn(II.tnin!<lii*,

4 February, 1864.

26

PALAEONTOLOGY OP THE UPPER MISSOURI.

Pander), is a true Streptorliynchus of King. Now, as these two names of Pander's
clearly antedate those proposed by D'Orbigny and Prof. King, and there can be no
doubt in regard to the types of Pander's groups, the law of priority compels us to
adopt his names. The fact that he did not clearly define his genera, and proposed
many species based upon mere varieties or individual modifications of a few species,
is no reason for setting aside his generic names, when his figures and descriptions
leave no doubts in regard to the genera to which his types belong.

The genus Hemipronites was first introduced during the deposition of the Silurian
rocks ; H. deformis (= Orthis deformis, Hall, Pal. N. Y., Vol. Ill, p. 174, pi. xiii, 3
a, b) and H. Woolworthanus (= Strophomena Woolworthana, Hall, ib., p. 192), from
the Lower Helderburg rocks of N. Y., being Silurian examples of this group.
The genus also occurs in the Devonian, Carboniferous and Permian rocks, probably
attaining its maximum development in the Carboniferous. It seems to have become
extinct before the commencement of the Triassic period, as we have no well
authenticated knowledge of its existence in beds of that age.

Hemipronites arctistriatus, H. alternatus (= Orthisina arctistriata, and 0. alter-
nata, Hall, Thirteenth An. Kept. Eegents University, N. Y., Dec. 1860, p. 80 and
81)1 and H. proximus (== Hipparionyx proximus, Vanuxem, Rept. 3d Geol. Dist.
N. Y., 1842, p. 124) are American examples of this genus from Devonian deposits.

Hemipronites crassus.

(PLATE I, Fig. 7, O, 6, C, d.)

Orthisina crassa, MEEK & HAYDEN, Deo. 1858, Proceed. Acad. Nat. Sci. Phila. 260.

Shell of medium size, snbquadrate, rather compressed, becoming thickened with age ; hinge nearly or quite equal-
ling the greatest breadth of the shell ; front broadly rounded ; lateral margins meeting the hinge nearly at right
angles, sometimes slightly sinuous near the hinge. Surface ornamented by numerous straight radiating striae,
which number near the beaks some thirty or forty to each valve, but increase by the implantation of others between,
so as to form one hundred to one hundred and twenty-four around the margin ; crossing these striae are numerous
fine elevated concentric lines, which are not only quite distinct in the depressions, but on well preserved specimens
are prominent upon the strise, to which they impart a creuulated appearance, as seen by the aid of a lens. Adult
specimens generally have also several strong concentric imbricating marks of growth.

Larger or ventral valve nearly flat ; cardinal edge sloping a little to the lateral margins ; beak somewhat promi-
nent, and often distorted, or slightly twisted to one side ; area flat, rather broad, and usually inclined backwards
over the hinge — angular along its margins ; pseudo-deltidium thick, prominent, nearly or quite closing the foramen ;
cardinal teeth not very prominent ; scars of the adductor muscles large, separated by a sharp, rather prominent
mesial ridge, and in old shells deep and well defined.

Dorsal valve moderately convex in the middle, and flat or concave on each side of the slightly convex umbo ;
cardinal process rather narrow. Interior of both valves marked by radiating striae around the borders.

Length of a rather large specimen, 1.25 inch ; breadth, 1.30 Inch ; convexity of the two valves, 0.46 inch.

At the time we first described this as a new species we had not seen accurate
figures of several analogous European forms now regarded as varieties of H. crenistria
(= Spirifer crenistria of Phillips). Since seeing Mr. Davidson's excellent figures
and descriptions of the various forms now included by him under that name, we are
led to doubt whether our shell is entitled to rank as a distinct species. Indeed,
supposing H. crenistria to vary to the extent admitted, it would seem to be im-
possible to assign any very definite limits to such a protean species, and hence it

1 Prof. Hall subsequently, in a foot-note on p. 112 of the same Report, refers these species to
Streptorhynchus.

CA K li()\ I I i: 110US A«. 27

would probably include our shell — which aijrei •> \. i\ closely in Conn and snrface-
markini;s with MIMIC lit' thosi- figured !>y Mr. Davidson. In t'unu it serins to be
most nearlv allied to the s|,, , 1,-s nr \ariet \ ,•,/.//.///* of Phillips, hut differs in having
its stria' of nearly uniforin si/e. Internally it also differs from that and all tin-
other analogous species or varieties, of \\hich \\e ha\e seen figures, in haunt; the
cardinal process ,,f the dorsal \;d\e proportionally narrower, and the socket plates
\\idely divergent. The innscnlar and \isceral impressions of its ventral \al\e,
as ma\ he seen 1)\ our figures, occupy a |iroportionally larger space, extending out
as the\ do aliont half the distance from the hinge to the front; while in the forms
figured liv Mr. Davidson, they only extend about one- third of the distance from
the hinge to the front. These differences, how i \c r. may not be of specific value.

Lix-<iHii/ 'in'/ //.<s,v;,,,,. — I.eaM-nworth City, Kansas, from a bed nearly on a level
with the Missouri Ki\er. Coal Measures. (No. 1010.)

CLASS LAJMELLIBRANCHIATA.

FAMILY PTERIID^E.

(-AVICCLID^B.)

inrquivalvo, inequilateral, composed of an inner laminated pearly
. and ;in (niter prismatic substance; left or upper valve always more
convex than the other. Anterior margin of the right valve generally
mure in less simmns for the passage of the by ssus. Cartilage submarginal,
simple, and placed in a single cavity or depression near the beaks, or
divided and distributed in a series of furrows crossing the cardinal facet
at right angles — or, in some of the older fossil genera (if distinct at all
from the ligament), occupying linear furrows in the cardinal area or facet,
ranging more or less nearly parallel to the hinge line. Hinge with or
without teeth. Scar of adductor muscle large and usually sub-central ;
anterior muscular impression generally small and placed near the beaks,
sometimes moderately developed. Pallial line simple, often irregularly
dotted.

Animal, in the existing typical genus, with mantle margin freely open
and doubly fringed ; foot small, grooved, and having the power of spinning
a byssus ; palpi large ; gills two on each side, crescent-shaped, free or
connected with each other posteriorly, and to the mantle.

The above diagnosis is drawn up so as to include species belonging to three sub-
ordinate groups, the first of which, so far as known, has no living representatives,
and seems to be mainly confined to the Palaeozoic rocks. The other two groups
(the Heri'mai or ArimH,,,,-, and Melinina:) arc both represented by living species
in our existing seas. These three sections or subfamilies may be characterized as
follows : —

28 PALEONTOLOGY OF THE UPPER MISSOURI.

1. Pterinilnae (or Pterinia group).

Cartilage apparently occupying a series of linear furrows, ranging more or less nearly parallel to the cardinal

margin, in a usually broad, flattened cardinal facet or area. Anterior muscular scar sometimes moderately

developed and deep.
Includes Pterinia, MyaUna, AmbonycMa, and probably Actlnoilesma, Grypktrkyndnu,' Eurtjdesma, and several

undefined Paleozoic groups. A part of the species referred to the genus Megambonia (3f. avicu/aides, M.

lamellosa, &c., HALL), will probably be found to belong to this subfamily, if not indeed to the genus Pterinia,

while the typical species appear to belong to the family Arcidse.

2. Pteriiiiae Cor Aviculinas).

Cartilage mainly or entirely confined to a single more or less defined depression or cavity behind the beaks.
Anterior muscular impression very small.

Includes Pteroperna, Pteria (or Avicula), 3fargaritifera, Malleus, Aucella and Ettmicrotis.1 The following
extinct genera also probably belong here, viz. : Monotis, Halobia, Pteronites and PouidoHoaia, with appa-
rently some undescribed fossil genera.

3. Melilliiiae (Perna or Isoynomon group).

Cartilage divided and distributed along the hinge in a series of furrows crossing the cardinal area at right

angles to the hinge line. Anterior muscular scar generally very small.
Includes Crenatula, Melina (= Perna, BKUG. not ADANSON), BakevtUia, Gervillia, Inoceramus and Pulvinites.

The first two of these sections seem to be more nearly related, in some respects,
to each other, than either is to the third ; and it is not improbable that they will
be found connected by a few Triassic and Jurassic forms presenting intermediate
characters, when the hinge and interior of a greater number of species are known.
The Jurassic genus Pteroperna, for instance, has hinge teeth analogous to those of
Pterinia, with apparently a cavity or depression for a cartilage, similar to that of
Avicula. Such exceptional cases, however, cannot be urged as a reason for not
admitting the convenience of sections or intermediate groups between families and
genera, for it is highly probable that if AVC knew all the characters of all the species
that ever existed, from the beginning of animal life to the present epoch inclusive,
we would find all our groups blending imperceptibly together, or at least very far
from being so sharply defined as they appear in works on natural history.

The Pterinia group, or subfamily, probably includes most of the Palaeozoic
species usually referred to Avicula, especially those from the Silurian and Devonian
rocks. Indeed, we very much doubt the existence, during the deposition of the
Palaeozoic rocks, of true Aviculas, as that genus is known to Conchologists, and
typified by the existing A. Jiirundo. At any rate, we have never seen a specimen,
nor can we remember a figure, of any species showing the hinge of a true Avicula,
from any of our American Palaeozoic formations. All the Silurian and Devonian
species .with which we are acquainted, the hinge of which has been seen, appear to
want the cartilage cavity of the modern Aviculas, and have the striated hinge facet,
or the oblique hinge teeth (one or the other or both) of Pterinia, more or less dis-
tinctly marked. In addition to this, most of the Silurian and Devonian, as well as
many of the Carboniferous species, the hinge of which is unknown, present more
the external appearances of the European species figured by Goldfuss and others,
in which the internal characters of Pterinia are known to exist.

Prof. McCoy some time since referred three of our American Paleozoic species —
A. demissa, A. pleuraptera and A. subfalcata — to Pterinia ; and the figures of A.

1 See American Journal Sci. and Arts (2d ser.), XXXVII, March, 1864, 217. s Ib. 21G.

CARBON" IF EROUSAOB. 09

ix, Hull, show traces of the broad striated area of that genus. A. jlnl*ll,t,
Conrad, from tin- Hamilton group, has also been found to IK- a true I'll /•////'«/.' From
all that is therefore known in regard to the affinities of these extinct shells, we may
safely infer that probably all of our Silurian and Devonian species, usually referred
to A'-i'-i/fji, especially those of the Hamilton and Cheiming groups, will be found to
possess the characters of I'ti i-iniii. or of undescrihed genera.

It is a fact worthy of note, that \\hile the existing genera of the family l'l> /•/'/«/.»
or .\i-ii-nli, In , form a group at once so natural and distinctly defined that Coucholo-
gists meet with little difficulty in deciding what particular forms it should include,
the boundaries of the family were not always so sharply marked. For, when we
undertake to classify the numerous extinct genera that were introduced, lived out
their term, and passed out of existence at various periods during the immense
interval of time between the first introduction of this type of life and the present
epoch, the case is \ery different ; since \\e tind amongst the vast numbers of fossil
speeies, types presenting \arions intermediate gradations between the modern
representati\es of this and some of the allied families. For instance, no Concholo-
gist could he for a moment in doubt whether any particular species or genus of our
existing mollusks belongs more properly to the Ari>-n/i</<r, or to the IMlnitlce. Yet
in tracing these two families, by their fossil shells, back into the distant past, we
meet \\ith various types presenting such an assemblage of characters as to often
render their proper distribution more difficult; especially since we have only the
lii,rlit of analogy to guide us in our conclusions respecting the structure of the
softer parts of these extinct forms. Some of these peculiar species were formerly
referred by many Palaeontologists to the genus Pteten, and by others to Avicvla ;
and even now, since the genus Arii-tilnpecten has been established for their recep-
tion, authors are by no means agreed whether this genus should be classed with
the J '><•//', i i</ir or the .•!/•/• •////»/< r.

Again, no one having even a small amount of conchological knowledge, need be
at a loss in deciding to which of the two families, An-lilir or Aviculida?, any of our
existing species of bivalves belongs. Yet in passing from group to group of the
A f I'l/n , from the recent typical examples through some of the other modem forms,
and thence through various extinct types, it will be observed that the hinge plates,
or denticles, become more and more oblique, until in some of the Palaeozoic genera,
such as Ci/rffntonfii. Vninisniiiii, Dolabra, &c., only a few obscure divisions are to
be seen at the remote extremities of the hinge, ranging nearly or quite parallel to
the cardinal margin, as in Rnki-r, ////?, /'t,rin in, and other genera apparently belonging
to the Ari'fiili'lir. In addition to this, in many of the extinct groups of Ari<-n/i,/,i ,
such, for instance, as Gryphorhynchm, Myallim, B<ik> i;lli<i, £.?., there is as well a
de\ eloped cardinal area, as we generally see in the Arcidce ; while this area in

o remarks on the family Aviculidte, by F. B. Meek, Am. Jour. Sci. and Arts (2d s« r.) V..I
\.\.\\ II. March, 1864, 46.

30 PALAEONTOLOGY OF THE UPPER MISSOURI.

several of these ancient types is provided with cartilage furrows, as in the Arcidce.
Again in Pterinia, and some species of Bakevellia, we see the anterior muscular
impression comparatively so well developed, that one can scarcely believe it was
not made by a true adductor ; while the eccentric position of the posterior muscular
impression would seem also to favor the same conclusion ; and yet in all their other
known characters these forms agree with the Ariculidce.

In another direction, some of these ancient groups of Aviculidai seem to show a
disposition to shade off towards the MytilidoK or Dreissenidce. Amongst the Carbo-
niferous and Permian species of Myalina, for instance, we see shells presenting
apparently exactly the form and general external appearances of the existing genera
Mytilus and Dreissena, to which even yet some Palaeontologists will persist in re-
ferring them. On a closer inspection, however, these Carboniferous and Permian
species, when we can find them with the two valves united, are seen to be always
a little inequivalve, while their hinge also diifers from that of the Mi/tilidce and
Dreissenidce, in having a flat cardinal area, with longitudinal cartilage furrows. In
addition to these differences, we have ascertained that the shell structure of at least
two species of Myalina (M. perattenuata, M. & H., and M. angnlata, Meek &
Worthen) is minutely prismatic, as in true Avicida.1 It is true the same struc-
ture has also been observed by Dr. Carpenter in the inner layer of Dreissena ;
but the unquestionable inequivalve character of Myalina, in connection with its
peculiar cardinal area, and the fact that these shells are always found associated
with marine types, are sufficient evidences that they have no very close affinities
to Dreissena.

SUBFAMILY PTERINIIN^E.
Genus MYALINA, KONINCK.

Synon. — Mytilus (sp.), SOWEKBY, and others (not LAMAECK, 1801).

Myalina, KONINCK, An. Foss. 1842, 125 (not CONKAD, 1845).

Aucella, GEINITZ, Dyas, 1861 (not KEYSEKLING, 1846, nor McCoy, 1855).
Etym. — ? Mya.
Examp. — Myalina lamellosa, KONINCK.

Shell mytiliform, or subrhomboidal, extremely inequilateral, moderately inequi-
valve, more or less oblique ; valves apparently a little gaping and slightly sinuous
in front for the passage of the byssus. Beaks pointed and nearly or quite terminal;
sometimes provided with an internal shelf or septum apparently for the attachment
of the anterior muscle. Surface smooth or with concentric markings of growth,
which, in some species, form imbricating laminae. Hinge nearly or quite edentu-
lous ; ligament area usually broad, and marked by distinct cartilage 1 furrows
parallel to the hinge line. Muscular and pallial impressions apparently as in Pteria.

Animal unknown.

1 See Am. Jour. Sci. XXXVII, March, 1864, 214.

OAR ''•<» N M-KROUS AGE. 31

Prof. Koninck described tliis genus as being cipiivalve — nn error into which he
doubtless led b\ the distortion of his specimens. IV'f. McCoy subsequently
des< ribed it as inequi\ ;d\e. which is undoubted!) correct, as we know from the
stiuh of our American species. As remarked b\ 1'mf. Koninck, the species oft in
dosi 1\ reseinlile Mi/til n.t and /'• n/n (Hrug. not Adanson) in form ; hut the inequality
of the vahes, and the broad striated cardinal area, will distinguish tlieni from tin-
first — and the absence of deep \ertical cartilage furrows in the hinge area, from the
latter. They seem to he e\en more closely allied to the fresh-water genus Dreiatena,
\\ ith which some of the species agree c\actl\ in form, excepting the slight inequality
of the \al\es. They also sometimes possess an internal shelf or septum in each
beak, as we see in that genus. \Ye ha\e likewise discovered that the shell struc-
ture is prismatic, as seen under a high magnifier, by transmitted light, as in the

!>,, 'I.-M i, 'nl, i and Ari'i -iili'lu.

\\ 'ere it not for the broad striated area, and the inequality of the valves, we
would certainh be inclined, from all the facts, to place this genus in the Dreissenidce,
instead of the J »•//•////</«•. The prismatic structure of which we speak, settles the
question in regard to these shells being distinct from the family Mi/tilidte ; but as this
structure occurs Ixith in the l)r> /.<.-•» n!<ln- and the .-I o'< »/,V/,p, it is not alone so conclusive
in regard to the relations of these shells to these two families. Further examinations,
howe\ er, may yet enable us to decide this point, since in the Aviculidte the inner layer
of the shell is not prismatic, but pearly, and the outer layer only is prismatic ; while
in the Dr> •!.•<*• a'ahr there is no pearly interior — the inner layer being prismatic, as
are the succeeding portions, excepting the very exterior. As the nacreous portion
of shells is most frequently destroyed during the process of fossilization, it is diffi-
cult to determine very satisfactorily whether it was really the inner or outer layer
in which we saw the prismatic structure — the shell being very thin, and apparently
more or less exfoliated in the specimens examined. Our impression, however, in
that it was the outer layer, or at any rate not the innermost; which would favor
the conclusion that these shells belong to the AviculicUe, as their inequivalve
character, and broad cardinal area indicate.

The annexed cut shows the prismatic structure as seen in a fragment of MycUina
angulata, placed in Canada Balsam, under a magnifying power of about 350
diameters.

Shell rtructure of Myalina angvlata, magnified 350 diuneton.

The genus Myalina seems to have been introduced during the latter part of
the Devonian epoch, or soon after the beginning of the Carboniferous, and pro-
bably attained its maximum development during the deposition of the Coal Mea-

33 1'AL.EONTOLOGY OF THE UPPER MISSOURI.

sures.1 It also occurs in the Permian rocks, and may possibly range up into the
Trias.

ITIynliiia perattenuata.

(PLATE I, Fig. 12, a, 6.)
Myalina perattenuata, MEEK & HAYDEN, Trans. Albany Institute, IV, March 2, 1858.

Shell very thin and fragile, obliquely elongate, narrow and slightly arcuate ; valves convex anteriorly, and com-
pressed behind. Beaks pointed, terminal and attenuate ; hinge line equalling rather more than half the entire
length of the shell, and ranging at an angle of about 50O above the oblique anterior margin. Posterior border
sloping from the end of the hinge, nearly parallel to the anterior side above, and rounding to the narrow antero-
basal extremity below ; anterior margin of the valves a little arcuate, and rather abrnptly deflected inwards from
the umbonal ridge above the middle, and in outline nearly straight below. Umbonal slopes prominent from the
beaks down the anterior side. Surface with obscure subimbricating marks of growth.

Length from the beaks to the postero-basal extremity, 1.50 inch ; breadth, 0.65 inch; convexity, about 0.44 inch.

This species will be recognized by its slender attenuate form, and very thin shell.
Like other species of the genus, it seems to have varied more or less in form, a
portion of the specimens being straighter on the anterior margin than others.
We know of no species with which it is liable to be confounded. Myalina (Modiold)
minor, Lea (Jour. Acad. Nat. Sci. Phila., Vol. II, 2d scr., p. 205) seems to be an
analogous species, but is more finely and regularly striated.

Locality and position. — Opposite the northern boundary of Missouri, on the
Missouri River. From seams of yellowish magnesian limestone, in the Coal
Measures. (Type 1022a.)

1I> alina subqiiadrata.

Myalina subquadrata, SHUMARD, Geol. Report Missouri, part Palaeontology, p. 207, pi. C, fig. 17, a, b.

Shell attaining a large size, compressed and somewhat alate in the postero-dorsal region, and convex anteriorly—
considerably higher than long ; posterior margin forming a broad gentle curve, being nearly straight and ranging
almost vertically near the middle, and curving forward so as to intersect the hinge at an obtuse, undefined angle
above, while below it arches regularly forward into the rather narrowly rounded base ; anterior margin thickened
within above, broadly arcuate or concave in outline, its curvature being nearly parallel to that of the posterior
margin. Beaks terminal, directed forward ; umbonal ridge most prominent and oblique above, and in adult sheila
carving downwards so as to range nearly vertically near the middle. Hinge line straight, and ranging nearly at
right angles to the longer, or vertical axis of the valves ; cartilage furrows distinct, straight, and in mature shells
numbering about ten or twelve ; area broad. (Muscular impressions unknown.)

Height about 4 inches ; antero-posterior diameter at the middle, 2.40 inches ; convexity of a left valve, 0.83 inch.

1 Prof. Hall refers an Upper Silurian shell, from the Clinton Group (Pal. N. Y. Vol. II, p. 100,
pi. xxx), to this genus ; but as his specimen is an imperfect cast, its true relations remain doubtful.

CARBONIFEROUS AGE.

ifyalina nbqvndrala.
A. Outside of a left valve somewhat weathered. D. Hinge view of same.

In size and general appearance this shell resembles Myalina subquadraia, of
Shumard, to which we have concluded to refer it provisionally, on the authority
of Dr. S., to whom we sent the above cuts for comparison. It will be observed,
however, on comparing our figures with those of the typical specimen of M. sub-
quadrata, published in the Missouri Report, that our shell differs in having its
posterior margin curving forward above, so as to intersect the hinge (as may be
seen by the direction of the lines of growth) at an obtuse undefined angle, instead
of being nearly straight and intersecting tin- hinge at right angles. This peculiarity
gives a different expression to the posterior outline of the shell, that had led us to
think it probably distinct. Should it be found, when we can have an opportunity
to compare a series of specimens, that this difference is constant in adult examples,
the propriety of separating these two forms can scarccjy admit of a doubt, in
which case the form under consideration may be designated as Myalina ampla.

Locality and position. — Leavenworth City, Kansas, from a thin layer of impure
limestone near the level of the Missouri lliver. Coal Measures. (Type No. 998.)

5 April, 1804.

34 PALAEONTOLOGY OP THE UPPER MISSOURI.

FAMILY CRASSATELLID^E.

Shell generally thick and strong, equivalve, oblong, oval, subcircular
or subtrigonal. Surface covered with a brownish epidermis, and often
ornamented with radiating or concentric costre. Hinge with generally
strong cardinal teeth; ligament external or internal. Muscular im-
pressions usually deep and well defined ; pallial impression simple or
very slightly sinuous.

Animal (in the typical genus) with mantle lobes only united by the
branchial septum ; margins of inhalent orifices cirrhated ; foot moderate,
compressed, more or less triangular, and grooved. Palpi triangular ; gills
unequal, outer semi-lunar, inner widest anteriorly.

Authors differ in regard to the limits of this family, some including in it several
genera which others refer to the Veniliidce1 (= Cyprinidce), or to-some of the allied
families. The existing genera most generally placed here, are Astarte, Gouldia,
Crassatella, Cardita, Carditamera, Thecalia, Trapezium, Coralliophaga, &c. It also
includes the following extinct groups, viz. : Venericardia, Pachydomus, Astartella,
Cardinia, Carbonocola, Astartila, Pachycardia, Pachyrisma, Megalodon, Mecynodon,
Hippopodium, Myoconcha, Opis, Pleurophorus, CleidopJiorus, Erycinella, Woodia,
Lutetia, and probably Cypricardella, MatJieria, Cypricardina, Anodontopsis, Cur-
tonotus* &c.

Genus PLEUROPHORUS, KING.

Synon. — Nuculites (sp.), CONRAD, Ann. Report Geol. N. Y. 1841, 48.

Pleurophorus, KINO, Ann. Mag. Nat. Hist. XIV, 1844, 313. — DK VERNECIL, Bull. Soc. Geol. Pr. 1844 (2d ser.)
1.— KINO, Monogr. Perm. Foss. Eng. 1850, 180.

Cleidophorus, HALL, Palasont. N. Y. I, 1847, 300.

Clidopkorus, McCoy, Palaeozoic Fossils, 1852, 273.
Etym. — irlivfb, a rib ; <t>i/>», to tear.
Type. — Area fostata, BROWN.

Shell generally small, longitudinally oblong or subovate, inequilateral ; cardinal
teeth two in each valve, interlocking alternately, and more or less divergent;
posterior lateral teeth one to each valve, the receiving tooth in the left valve.
Anterior adductor muscular scar deep, and bounded posteriorly by a ridge ; pallial
line simple.

This genus may be distinguished from Cardita, by its depressed, elongate form,
as well as by its upper cardinal tooth in the right valve being elongated posteriorly,
and by having true posterior lateral teeth. From Cypricardia, and Carbonocola, it
differs in having the receiving tooth in the left, instead of the right valve. From
Carditamera, with which it agrees in the arrangement of the lateral teeth, it differs

» The name Cyprinidne having been long in use for a family of fishes, ought not to be retained for
this group.

9 It is desirable that the author of this genus should select another name for it, Curtonotus having
been used by Hann for a genus of Crustacea, in 1835.

CAUBOXIFKKOUS AGE. 35

in having a short upper cardinal tooth ; and in being destitute of anterior teeth.
It also r< -t 'lulilcs ('<>i-alli<,j,/t<i<j,i, from which, however, it is clearly distinguished by
its simple pallial line.

Prof. M'('o\. \N!IO lias had an opportunity to compare t\pical specimens of

f '/• i,li,j,/tni-nt<, with examples of J'/, n, i,],/,,, ,•</.< showing the hinge, sa\- 1 1 icy agree

tly in their dentition, and it is on his authority that we here regard them as

synonymous. Our description of the hinge is taken from Prof. King's carefully

written description of /'// n,-"/>/t<>rit.-<.

Prof. Hall's name, lioui M r, ma\. we think, be properly retained in a subgcneric
sense, for a section of this group probably confined to the Silurian rocks. This
subgenus may lw distinguished from the t \pical costated species found in the more
modem formations, by the following characters: —

HALL.
Shell without radiating pottero-donal cost*. Internal ridge bounding the tear of the anterior adductor,

descending with a slight forward slope.
Type. — \aculitfi planulata, Cos BAD.

The genus Pfenrop&ontf, as here defined, was introduced during the Lower
Silurian epoch, where it was represented by the smooth species. It also ranges
through the Carboniferous and Permian rocks, as stated above, into the Trias, the
more recent species being the typical forms.

PJcurophortiK occidental!*.

(PLAT! I, Fig. 11, a, i.)

Pleuroplionut oeeidentalti, MEEK & HAYDKX, Trans. Albany Institute, IV, March 2, 185.

Shell small, narrow, somewhat elongate; valvei moderately convex along the nmbonal sloped. Basal and
dorsal margins nearly straight and snbparallel, or converging slightly toward the front ; posterior tide rounded,
and rather compressed ; anterior side rouuding np gradually from the base. Beaks small, depressed, and located
at the anterior extremity ; hinge line long and straight. Surface with a few concentric marks, and traces of finer
lines of growth, which are crossed by some four or fire small faintly defined radiating costae, extending from tbo
beaks obliquely backwards and downwards to the posterior, and postero-basal margins.

Length, 0.37 inch ; height, O.lfi inch ; breadth, or convexity of the two valves, about 0.14 inch.

Not having seen the hinge or interior of this little shell, we are not sure it really
belongs to the typical group J'l< tini/i/Kiru*. It agrees, however, so nearly in its
external characters, with P. costattw, as figured by Prof. King in his work on the
Permian fossils of England, that we are strongly inclined to think it will be found
to possess a similar hinge. Specifically, it differs from P. coxtadw, in being much
smaller, more depressed, and more contracted in the antero-ventral region.

Locality and jxmition. — Nebraska, nearly opposite the northern boundary of
Missouri. Coal Measures. (No. 1017.)

36 PALAEONTOLOGY OF THE UPPER MISSOURI.

FAMILY

Shell thin, often inequivalve, inequilateral, more or less gaping pos-
teriorly, pearly within. Surface, in well preserved specimens, generally
granulose, concentrically or radiately striate or costate. Hinge teeth
usually rudimentary or obsolete ; ligament external, thin ; cartilage occu-
pying an internal pit or cavity under the beak of each valve, and usually
provided with a free ossicle. Beaks sometimes fissured. Muscular im-
pressions faint ; pallial line generally sinuous.

Animal with long, more or less separated siphons, which are fringed
at the extremities ; mantle with united margins, provided with a valve-
like opening under the siphons ; gills single on each side, pinnate — outer
laminae prolonged dorsally beyond the line of attachment.

A number of fossil genera appear to belong to this family, though their affinities
have not been very clearly determined. It is possible some of those mentioned
below may belong to one or more distinct families ; but until their relations can
be made out more satisfactorily, from the study and examination of the hinge and
interior of a larger number of species, we prefer to place them here.

The existing genera, properly included in this group, are Anatina, Peri/ploma,
TJiracia, Lyonsia, Mytilimeria, Poromya, Myodora, Pandorella, Ccelodon, Pandora,
Clidiophora, Tfeora, Necera? Tyleria, and Pholadomya.

The extinct groups, apparently belonging here, are Margaritaria, Cercomya,
Anatimya, Allorisma, Myacites, Homomya, Anthracomya ? Chcenomya, Platymya,
Arcomya, Mactromya, Goniomya, Gresslya, Cardiomorpha, Ceromya, /Sedgwickia,
Sanguinolites, and probably Cleobis and some of the species included in the genus
Orthonota.

Genus ALLOEISMA, KING.

Synon. — Sanyuinolaria (gibbosa), SOWEKBT, Min. Conch. VI, 1814, 92.

Myacites (sp.), SCHLOT. f Petrefact. 1820, 176.

Hiatella (sulcata), FLEMING, Brit. An. 313.

Pholadomya (elongata), MORTON, Am. Jour. Soi. XXIX, 1836.

Sanguinolites (part), McCoy, Carb. Foss. Ireland, 1844, 47.

Allorisma, KIKO, Ann. Mag. Nat. Hist. XIV, 1844, 315 ; Mon. Permian Foss. England, 1850, 196.
Etym. — ixWoc, variable ; t^i^/jut, support.
Examp. — Hiatella sulcata, FLEMING.'

Shell equivalve, inequilateral, elongate, thin ; anterior side short ; posterior side
long and somewhat gaping at the extremity ; beaks depressed, anterior. Surface
minutely granulose, and ornamented with more or less distinct concentric ridges

1 As first defined by Prof. King, this genus was made to also include species belonging to the gonus
Edmondia. We observe that he remarks in a foot-note to page 196 of his Monograph of the Permian
Fossils of England, published in 1850, that he avails himself of that opportunity to name Hialella
sulcata as the type of this genus, instead of Allorisma regularis of Murchison, Verneuile & Keyser-
ling's work on the Fossils of Russia ; because he thinks the latter more probably an Edmondia.

CARBONIFEROUS AGE. 37

or undulation*. Hinge edentulous ; ligament apparently wholly external. Dorsal
margin inflected so a* to form a lanceolate depression or false area along the car-
dinal border behind the beaks. Scar of anterior adductor muscle occupying a
comparatively low position. 1'allial line faintly marked; its sinus sometimes deep,
rounded or angular.
Animal unknown.

are rather at a loss to find well marked and constant external characters by
which the shells of this genus can be al\\a\- readily distinguished from some of the
Triassie and Jurassic forms usually referred to J///»/r//» x, and included by 1'rof.
Agassi/ in the groups for which he proposed the names Plevronn/n and MI/OJHU.
Indeed some of our Devonian and Carboniferous species, if found in Triassie or
Jurassic rocks, would l>e at once referred to Mytn-!t<x, !'/> nromya, or Myopei*, by
most Geologists. As observed by 1'iof. Agassiz, the shells included by him under
the latter two names are very closely allied, and it was mainly in consequence of the
presence of cardinal teeth, and a granulated surface in several of the species of J/'/"y>-
sis (characters not observed in those referred to the group he called Plcuromya), that
the\ were separated. Some subsequent European investigators, however, say they
find these characters common to species included in both groups. If these observers
are not mistaken, these two groups should probably be united under the older name
Afyacitc*, from which the. genus under consideration would be mainly distinguished
by its edentulous hinge. The Allorismas arc, however, also generally longer shells,
with more depressed beaks, and they were probably never so widely gaping behind
as some species of Mi/m-Iti'*.

From the genus P/«i/<i</<»i>//<t, to which this group is related, it can always be
distinguished by the total absence of the radiating costs so characteristic of that
genus. They likewise differ in the granulated character of the surface, though it
is rather rarely the case that we find specimens in a condition to show this latter
peculiarity.

The genus Allorlsma appears to have been first introduced during the Devonian
epoch, and attained its maximum development before the close of the Carboniferous.
It also occurs in the Permian rocks, and, as already stated, some very similar forms
have been described under the name of Myacites from the Triassie and Jurassic rocks.

Allorisma subcuneata.

(FnxB I, Pig. 10, a, 6.)

Allnriina ruticunrala, MRBK & HATDKK, Proceed. Acad. Nat. Sci. Phila. Deo. 1858, 263.
Comp. Sanguinotita rlara, McCoT, Brit. Pal. Fogs. 1852, Fasc. Ill, 604, pi. 3 F, flg. 12.

Shell large, clavato-cnneate, gibbons in the anterior and nmbonal regions ; narrowed and compressed posteriorly.
Beaks depressed, incurred, and located about one-eighth the entire length of the shell from the anterior extremity.
Posterior end narrowly rounded, and apparently moderately gaping ; anterior end obliquely subtruncat* above, and
rather narrowly rounded and somewhat produced below ; basal margin nearly straight along the middle, contracting

This, however, was unnecessary, since he had distinctly stated in first publishing the genus in the
Annals :nul Map. Nat llist. Vol. XIV, 1844, p. 315, that it "is represented by Sanguinolaria
lulcata of Phillips."

38 PALAEONTOLOGY OF THE UPPER MISSOURI.

very gradually behind, and rounding up more abruptly in front ; dorsal margin nearly parallel to the base, or
declining a little posteriorly. Surface of internal casts marked by rather small, moderately distinct concentric
undulations, which are quite regular over the umbones, but become more irregular and obscure towards the
margins of the valves.

The hinge ia long, and nearly straight. In casts there is a rather narrow depression extending along its entire
length, bounded on either side by an obtuse ridge, ranging parallel to the hinge line. Immediately outside of each
of these ridges there is a shallow rounded sulcus, which is widest near the posterior muscular scar, and becomes nar-
rower, and less distinct towards the beaks. The anterior muscular impression is well denned, transversely lunate in
form, and connected with the pedal scar above in such a manner that the two together present much the appearance
of a capital letter G, lying on its back. The posterior muscular scar is large, broad rhombic-subovate in form, and
placed near the hinge, about one-third the entire length of the shell from the posterior extremity. The pallial line
is faintly marked, and apparently provided with a deep acutely angular sinus.

Length, 5.10 inches ; height, 2.25 inches ; greatest thickness or convexity near the anterior end, 1.70 inch.

This species is very closely allied to Sanguinolites dava, of McCoy (cited at the
head of this description), and may possibly prove to be identical, when a direct
comparison of specimens can be made. Those we have yet seen, however, of the
Kansas fossil, differ from Prof. McCoy's figures in being straighter on the dorsal
margin, and more produced, as well as more narrowly rounded in the antero-ventral
region. Their concentric undulations are also more obscure, and the lunule-like
depression in front of the beaks less distinctly defined, in our shell.

Locality and position. — Leavenworth City, Kansas, from a bed holding a posi-
tion a few feet above low-water mark of the Missouri. Coal Measures. (Type
1020.)

Genus SEDGWICKIA, McCor.

Synon. — Sedgicickia, McCoy, Synopsis Carb. Foss. Ireland, 1844, 61.

Leptodomus, McCoy, British Pal. Foss. 1852, 277 (not 1844, Carb. Foss. Ireland, p. 66).

Sanguinolites (part), McCoY, Brit. Pal. Foss. 1852, 276 (not Carb. Foss. Ireland, 1844, p. 47).
Etym. — Dedicated to Rev. Adam Sedgwick, M. A., F. R. S.
Type. — Sedgwickia attenuate, McCoY.

Shell depressed oblong, or suboval, nearly or quite equivalve, inequilateral, very
thin ; anterior side not quite closed, often a little gibbous ; posterior side longer,
more compressed, and more widely gaping. Beaks prominent, rather tumid, in-
curved ; posterior umbonal slopes prominently rounded, or sometimes forming an
oblique ridge, generally separated from the compressed postero-dorsal region by a
shallow, linear sulcus, which is also sometimes marked on internal casts. Flanks
compressed, or somewhat concave in the antero-ventral region, or a little behind it.
Lunular impression distinct. Surface finely granulose, and ornamented with more
or less regular concentric ridges and striae, the ridges being usually obsolete on
the posterior and compressed postero-dorsal portions of the valves. Hinge edentu-
lous ; cardinal margin inflected so as to form a narrow false area behind the beaks.
(Muscular and pallial impressions very obscure and not well known ; animal un-
known.)

This group, as here defined, agrees in all essential characters with Leptodomus,
as characterized in 1852 by Prof. McCoy, in his beautiful work on the British
Palsezoic Fossils. We think, however, that this name cannot be retained, in

CARBON I 1 1 KOI B A 39

accordance with the established rules of nomenclature, for these shells, because
the t\|>e <•!' the genus /.>/>/>*A/j/iu#, as originally founded by Prof. Mi Coy (//. //•«/•//-
/w, Carh. I'oss. Ireland. Is It, till), apparently belongs to an entirely different
group. On turning to Prof. McCoy's figure of this species (Ib. pi. x, fig. 11), it
will lie seen to he a short, high. \eiitricose shell, with gibbous distinctly incurved
beaks, and a nearly smooth, or merely striated surface, and rather well marked
muscular impn -vimis. Indeed \ve are led by Prof. .McCoy's figure and description
to think this shell not geiiericalh distinct from some of the forms included by Prof.
Koninck in his genus CbrvftoMOIpAo, though it may be a ScJiizodus, King.

On the other hand, we think the shells under consideration, are not generi-
eall\ distinct from Setlywickia, McCoy, as originally proposed by him in his Synop.
Carb. Foss. 1M I, j>. (51, and typified by his S. attcnnata (Ib. p. (i'J). It may be,
lm\\e\er, that Prof. McCoy dropped the name ,W'/"'<V /.•/.(, because it had been used
several times in Botany. Still we cannot regard this as a sufficient reason for
setting the name aside, for there are numerous instances where the same name is
retained for genera in Botany and Zoology. In addition to this, the particular
genus for which Botanists now retain the name Xdgtvickia, was published by
(niffith, since the publication of Prof. McCoy's genus. Even if we admit, how-
ex er, the propriety of abandoning the name ,W</ »•/</.-/«, these shells cannot be
properly referred to Leptodomvs, we should think, until it can be demonstrated, or
at least rendered probable, that they are congeneric with the type of that genus —
/.. //•<«////>, McCoy.

It is worthy of remark, also, that these shells resemble the typical Allorismas in
so many points that we have some doubts whether they should be separated more
than as a sub-genus. They are also rather closely allied to Myacites, as affirmed by
Munstcr. From the typical species of the former genus, they differ in being
shorter and usually more gibbous shells, with more prominent beaks and umbonal
slopes. They also differ in having the postero-dorsal region more compressed, and
the cardinal margin more concave in outline behind the beaks. These peculiarities
give these shells a Lyonsta-like aspect apparently never seen in the true Allo-
rismas. In their less elongated form, and more prominent beaks, they approach
nearer some species of Myacitcs, but differ in the other characters mentioned.

From the genus Sanguinolites, as originally defined, and typified by Sanguino-
laria ? angustata of Phillips (McCoy, Carb. Foss. Ireland, 184-1, 47 and 48), our
shells differ in being proportionally much shorter, more gibbous, less depressed,
and not near so straight and parallel on their dorsal and ventral margins. Until
something, however, can be determined in regard to the hinge or muscular and
pallial impressions of Sanguinolites anyustatwi, the type of that genus, we can form
no satisfactory conclusions in regard to its limits. It is true, Prof. McCoy, in
re-describing this genus, in his Brit. Pal. Foss. 1852, describes the muscular and
pallial impressions ; but it is manifest these characters were taken from his S.
indiwndea, and other forms, that may or may not be congeneric with the species
angustatus. Should the S. //vV////o/'-/. .s. however, really be congeneric with that
species, which is not improbable, it would rather confirm the conclusion that the
short gibbous shells under consideration are generically distinct, than the contrary.

40 PALEONTOLOGY OF THE UPPER MISSOURI.

The following species seem to be congeneric with the original type of Sedy-
wickia, viz. : S. costellata (= Sanguinolites (Leptodomus) costellatus, McCoy, Brit
Pal. Foss. pi. 3, F, fig. 5); S. variabilis (= Sanyuinolites variabilis, McCoy, ib. fig.
6); S. truncata (= Leptodomus truncatus, McCoy, ib. pi. 1, K, fig. 21 and 24), and
8. granosa and S. topekaensis (= Leptodomus granosus and L. topekaensis, Shumard,
Trans. St. Louis Acad. I, p. 207-8).

If we are right in referring Leptodomus truncatus, McCoy, to this genus, it would
carry back the origin of the group at least to the Upper Silurian epoch. Some
similar forms also occur in the Devonian rocks, and the genus probably attained
its greatest development during the deposition of the Carboniferous Series.
Several species presenting very similar external appearances have also been de-
scribed under the names Myaciies, Cypricardia, &c., from the Triassic and Jurassic
deposits ; but we have little or no knowledge of the true affinities of many of these
shells, and consequently cannot pretend to define, with precision, the geological
range of the genus Sedgwickia,

Sedgwickia topekaensis?

Leptodomus Topekscnsis, SHCMARD, Trans. St. Louis Acad. Sci. I, 1858, 208.

Shell depressed subovate, about twice as long as high, extremely thin and fragile, gibbous in the region of the
beaks, and along the oblique umbonal slopes. Sides flattened above, and becoming a little concave towards the
base in front of the middle. Dorsal border nearly horizontal, and slightly concave in outline behind the beaks,
where its inflected edge is margined by a rather distinct ridge ; ventral border presenting a broad semi-ovate outline,
excepting a very slight sinuosity just in advance of the middle — rounding up abruptly in front and more gradually
behind ; anterior side prominent, gibbous, and narrowly rounded below, obliquely truncated above ; posterior side
compressed, narrowed, and apparently subtruncate and somewhat gaping at the extremity. Lunular impression in
front of the beaks (in casts) moderately distinct, defined by a faintly impressed line. Beaks prominent, gibbous,
a little flattened, incurved, and placed between the middle and the anterior extremity, but nearer the former.

Entire surface, in well preserved specimens, closely covered with minute granules arranged in radiating rows ;
and ornamented with small concentric ridges, which are most regular and distinct on the nmbones, and end
abruptly along an impressed line extending from the posterior side of each beak obliquely towards the postero-
basal margin, thus leaving the compressed postero-dorsal region comparatively smooth. (Muscular aud pallia!
impressions unknown.)

Length about 2 inches ; height, 1 inch ; convexity, 0.75 inch.

Sedgwickia topekuensis ?
A. Dorsal view, partly restored, one valve being distorted in the specimen. B. Side view of same.

This shell is closely related to S. granosa (Leptodomus granosus, Shumard), but
seems to agree more nearly, when all its characters are taken into consideration,
with the form described by him under the name Leptodomus topekaensis ; particularly
in the possession of a shallow linear sulcus extending from the back part of each
beak, towards the postero-basal margin. It is true, Dr. S. does not mention the
presence of fine granules on the surface of the species Topekaensis, while this is one

C A in: ON i ri: unr s A c, i: 4!

of the characters of his i/i-nmun. The ;i]i]):ircnt ahscncc of granules, however, on
the- former may !><• due to the condition of the specimen, as tliis is a character easily
obliterated by wearing. Of the known foreign species, its nearest represcntathe
is perhaps S>ni<jiiiiii>Hi»> r<tri<t/,i/is, McCoy (Mrit. 1'al. Ko>s. pi. 8, F, fig. 6-7), from
which it differs in bring much narrower posteriorly, and in having a proportionally
longer hinge line, particular!) a> coni|)ared with adult specimens of Mc( '«\ 's -]><-ci< ^.
Its antero-ventral region is ulso more prominent than that of X ntr't.ihilis.

/."•ii/it// mi'/ IH^;I'H,H. — Leavenworth City. Kansas; it occurs both in the hills
hack of the town, t>(K) to 'J")0 feet above the Missouri, and iu beds of impure
limestone near the landing, little above the level of the river. Coal Measures.
(Type No. 1011.)

Sedgwickia '. concnra.

(PLATE I, Fig. 8, a, 6.)

Lyoniia roneara, M(KK & HATDKV, Trans. Albany Inst. IV, March 2d, 1858.

Shell small, rlon?atr-oval ; valves moderately convex in tlie nmbonal and anterior region*. Extremities rounded ;

•r i -n. I . ..ni].r."is«l, apparently a littln gaping ; base nearly straight along tin- middle, and rounding up at

tln> <>\triMiiiti>>« ; dorsal outline concave behind the beaks — declining iu front. Beaks rather depressed, ini-urv.-.l,

nii'l located about half-way between the middle and the anterior extremity. Surface of casU with a few more or

less distinct marks of growth. (Hinge, muscular and pallial Impressions unknown. )

Length, O.C5 inch ; height, from base to top of beaks, 0.30 Inch ; convexity, 0.23 inch.

In first publishing a description of this species, we placed it provisionally in the
genus 1. ;/,, iixin, stating, at the same time, that our specimens were merely costs, and
that we were consequently left in doubt in regard to its generic relations. Subse-
quent examinations of other specimens have satisfied ns, however, that it can
scarcely be a Lyonsia — there being no impressions in well preserved internal casts,
of the projecting cartilage plates so characteristic of that genus. This being the
case, we now place it with doubt, in the genus Sedgwickia, to which it api>ears
to be more nearly related ; but in so doing, we should remark that until specimens
showing the hinge, and other internal characters can be examined, its true affinities
cannot be detennined with any degree of confidence.

Locality ami position. — Nebraska, opposite the northern boundary of Missouri.
Coal Measures. (Type No. 1023.)

Sedgwickia? altiroNtrafa.

(PLATB I, Fig. 9.)
Alloritmat altirottrala, MlXK & HATDKX, Proceed. Acad. Nat. Set. Phila. Deo. 1868, 263.

Shell longitudinally oblong-oval, very gibbons in the nmbonal region ; beaks elevated above the cardinal margin,
incurved, and located almost directly over the anterior edge. Posterior side rather broadly and regularly rounded,
apparently gaping; anterior side snbtruncate, a little gaping, and rounding into the base below; ventral border
nearly straight, or somewhat concave in outline near the middle, and rounding up at the extremities. Cardinal
margin straight, rather short. Surface of cast ornamented by concentric undulations, which are small, regular,
and well defined on the nmbonal slopes, but become leas distinct, and more irregular near the margins of the valves.
Just in front of the most prominent part of the oblique nmbonal ridge of each valve there is a moderately distinct,
narrow, undefined sulcns, extending backwards and downwards to the middle of the base.

Length, about 3.06 Inches; height, from the base to the dorsal margin, 1.57 inch ; do. to the highest part of
the beaks, 1.74 inch ; greatest convexity of the two valves, 1.62 inch.

It is only provisionally we place this species in the genus Sedgwickia, not having
seen any specimens showing the hinge ; while the form of the shell is different

« April. 1864.

42 PALAEONTOLOGY OF THE UPPER MISSOURI.

from that of the typical species, the nearly terminal position and greater elevation
of the beaks giving it much the physiognomy of many species of Pholadomya.
Indeed, it only wants radiating costae to present all the external characters of that
genus. It is more nearly related to Pholadomya Omaliana, Koninck, than to any
other shell with which we are acquainted, from any part of the Carboniferous
system. Yet it differs in having more elevated, and rather more nearly terminal
beaks, as well as in the possession of an oblique sulcus in front of the umbonal
slope of each valve. The concentric undulations are likewise more distinct and
regular on its flanks, and its antero-ventral region is less prominent.

It is probable that this shell will be found to present internal characters warrant-
ing its separation, either as a sub-genus, or as a distinct genus, from" Sedg-
wickia. If so, we would propose for the group the name Exochorhynchus (g^o^og,
prominent ; 'zi"y%o$, beak). It would include E. (Pholadomya) Omaliana, of
Koninck.

Locality and position.. — Juniata, on Big Blue River, Kansas. Coal Measures.
In the paper cited at the head of this description, Grasshopper Creek was, by some
oversight, erroneously given as the locality from which this species was obtained.
(Type 1021.)

Genus CH^NOMYA, MEEK.1

Synon. — Mya (sp.), PHILLIPS, Geol. York. I, 1835, 157 (not LINN.).

Panopsea (sp.), D'ORBIGNY, Prodr. de Palseont. I, 1850, 273. — MEEK & HAYDEN, Trans. Albany Inst. IV,

March, 1858, 11 (not MENARD).

Myacites (sp.), MORRIS & LYCETT, Moll. Great Oolite, 1853, 114 (not SCHLOT. ; MUNSTEH).
Allorisma? (sp.), SWALLOW, Trans. St. Louis Acad. I, 1858, 194. — MEEK & HAYDEN, Proceed. Acad. Nat.

Sci. Phila. Dec. 1858, 263 (not KINO, 1844).
Etym. — x_wx, to open or gap; and Mya.
Type. — Allorisma 1 leavenworthensis, MEEK & HAYDEN.

Shell thin, equivalve, longitudinally oblong, subcylindrical. Anterior side
rounded, closed ; posterior side long, distinctly truncated, and very widely gaping,
or even dilated at the extremity. Beaks depressed and located in advance of
the middle. Surface minutely granulose, and usually provided with obscure con-
centric undulations, and more or less distinct lines of growth. "Cardinal margins
more or less inflected, as in Allorisma ; ligament apparently entirely external ;
hinge edentulous. Posterior muscular impressions placed near the posterior ex-
tremity of the dorsal margin ; scars of the anterior adductor and pedal muscles
connected. Pallial line with a broad shallow sinus.

1 Since this description was placed in the hands of the printer, we have been led to suspect, from some
incidental allusions to the genus Anthracomya, in a lecture by Prof. Salter, published in the London
Geologist, that the group here described may possibly be identical with that genus. As we have not
yet seen the description of Anthracomya, however (the Memoir in which it was published not being
in the Smithsonian Library, nor any of those at Cambridge, New Haven or Philadelphia), .we are left
in doubt, and have concluded we would probably be less liable to err by proposing a new genus, than
by referring our shells to Anthracomya. Should they prove to belong to Mr. Salter's genus, how-
ever, we will cheerfully accept for them, the names Anthracomya leavenworthensis, A. Cooperi, and
A. minnehaha.

CARBONI KKKOU8 AOE. -»;{

This genus seems t<> !»• clo-ely allied ti> -nine of the species included l>y Prof.
Agassi/ in hi- Lreims I'lnti/iiii/ii — particularly to his /'. ////i//'.-. It differs. howe\er,
from /'. t/i/nl, it, i. the t\pe <>t' the genus /'lufi/iiii/ti, in being Miln \ lindrieiil instead
of compressed, and in having the posterior side distinctly truncated and \ery widely
gaping. Again it differs in having the surface covered with minute granules — a
character not observed in any of the species referred to the genus l'l<ih/ini/,i. Prut".
\ UU, to whom WO ihowed our specimens, concurs with us in the opinion that
they are not congeneric with the forms upon which he founded his genus.

From Allontni'i of Kin-;, and l'l> »/•<//////./, Agassiz, as well as the typical species of
Mi/iirlt,*. the species included in this group may be at once distinguished, hy their
truncated and widely gaping posterior end, and less prominent antero-ventral region,
as well as by the more i le\ated position of the scar of the anterior muscular im-
pn-ssion. All the species yet known are also destitute of any traces of a shallow
depression extending from the beaks to the antero-ventral margin, so commonly seen
in Mi/ni-it,M. while they want the cardinal teeth generally present in that genus.
Again, they seem to have differed in their habits from the species generally placed
in A//<>rixiiiii, which were probably, as suggested by Prof. King, surface-creeping
mollusks. At any rate, we observed in numerous instances while in Kansas, where
specimens of Alloi-itiiia were to be seen side by side in the same bed with the
t \pical species of the group under consideration, that the latter were, in nearly
every instance, found imbedded at right angles to the plane of the strata, with the
open posterior extremity upwards, as if in their normal position as burrowing shells;
while the Allorismas were generally found lying in a horizontal position.

From the genus Panoj)(ra, which our Kansas shells closely resemble in form, they
differ in their greater thinness, faintly marked pallial line, granular surface, and
entirely edentulous hinge.

This genus, as here defined, commences in the Coal Measures, and ranges up at
least into the Great Oolite, if not higher. It includes Chtenonii/n. <HI<ii<iln ( M//n
</i/<ttala,of Phillips), and probably several other Jurassic species; also our ]'<IH<>J><I<I
Cooperi, and Chcenomifa Miitm/m/ia (= Allorisma? Minn<l«iltn, of Swallow), from
the Upper Coal Measures of Kansas.

< h.Tiioiiiva Icavenworthensi*.

(PLAT« II, Fig. 1, a, 6, c.) '
Allorisma t leavenwortkenrii, HEKK & HATDKX, Proceed. Acad. Nat. Sci. I'lilU. Dec. 1668, 263.

Shell oblong snbcylindrical ; anterior side rounded, a little compressed and apparently entirely closed ; posterior
side long, truncated, and very widely gaping, the margins being even a little reflexed. Base nearly straight, or
slightly convex in outline, rounding up gradually in front, and very abruptly behind ; dorsal side concave in out-
line from the beaks to its elevated posterior extremity, and nearly parallel to the base. Beaks rather depressed,
powrwhat flattened, incurved, nearly or quite touching, and located about half way between the middle and the
anterior end. Surface marked by fine lines of growth, and a few irregular, nearly obsolete concentric undulations,
which curve up abruptly behind, parallel to the truncated posterior margin ; crossing these, the radiating rows of
minute grannies may be seen, by the aid of a good lens, on well preserved specimens.

Internal casts of this species show quite distinctly the soar of the anterior adductor muscle, which Is oval, and
located near the bnccal margin, with iU longer axis nearly at right angles to that of the shell. At its upper
extremity the small oval pedal scar It also well defined in both valves. The posterior muscular Impression is
broad oval, and rather faintly marked ; from near the middle of its under side the pallial line descends with a
gentle forward curve, so as to form a broad, rounded, very shallow sinus.

Length, 2.85 inches ; height, from the ventral margin to middle of the dorsal side, 1.36 inch ; do., from the bate

44 PALEONTOLOGY OF THE UPPER MISSOURI.

to a lino drawn from the beaks across to the most elevated part of the posterior extremity, 1.50 inch ; greatest
convexity near the middle, 1.11 inch ; breadth of posterior hiatus, 1.07 inch ; height of do., 1.44 inch.

This species is so nearly like Mya dilatata, Phillips (as figured by Morris & Lyatt,
Moll. Gt. Ool. vol. X, fig. 5), from the English Oolite, that if found imbedded
with it in the same rock, they might, on a hasty examination, be mistaken for
varieties of the same shell. On comparison, however, it will be seen that the
Kansas species has its beaks more elevated, and placed nearer the anterior end ; it
is also a little broader shell, in proportion to its length, and rather straighter on the
dorsal and ventral margins.

Locality and position. — Near the level of the Missouri River, at Leavenworth
City, Kansas. Coal Measures. (Type 1019.)

Chaeiiomya Cooperi.

(PLATE II, Fig. 2, a, b.~)

Panopma Cooperi, MEEK & HATDEX, Trans. Albany Inst. IV, March 2d, 1858, 11.
Allorisma ? Cooperi, MEEK & HAYDEX, Proceed. Acad. Nat. Sci. Phila. Dec. 1858, 264.

Shell oblong subcylindrical ; posterior side very abruptly truncated, a little oblique, and widely gaping; anterior
side more compressed, and rather narrowly rounded. Base nearly straight along the middle and behind, rounding
up in front ; dorsal side concave, and not declining behind the beaks, sloping rather abruptly in front. Heaks
depressed, incurved, contiguous, and located about half way between the middle and the anterior end. Inflected
cardinal margins a little thickened within, so as to leave a deep narrow depression along the cardinal border, in
casts of the interior. Surface (of internal casts) marked by small, rather obscure concentric ridges, which are
most distinct and regular on the umbones, and gradually fade away on other parts of the shell. (Muscular and
pallial impressions unknown.)

Length, 2.57 inches ; height, 1.37 inch ; convexity or breadth, 1.12 inch ; breadth of posterior hiatus, 1 inch.

This species will be readily distinguished from the last, by its proportionally
shorter form, and more distinctly truncated and shorter posterior side. Its beaks
are also rather less prominent, and marked by finer and more distinct concentric
ridges. It seems to be more nearly related to a species described from the Coal
Measures of Kansas, by Prof. Swallow, under the name of Allorisma ? minneJiaJia,
though our specimen wants the oblique ridge mentioned in the description of that
species. Should they prove identical, however, the specific name Cooperi will have
to take precedence, as it was published nearly a month in advance of the issue
of Prof. Swallow's description.

Locality and position. — Helena, Kansas Territory. Coal Measures. (Type 1018.)

CLASS GASTEROPODA.

SUB-CLASS PROSOBRANCHIATA.
ORDER Riphidoglossata*

SUB-ORDER PODOPTHALMA.

FAMILY PLEUROTOMARIID^E.

Shell varying in form, thickness and ornamentation, according to the
genera and species ; imperforate or more or less widely umbilicate, pearly
within. Aperture not sinuous, or produced below. Outer lip with a

c A n i;o N i i i: nous A(. i. .«;,

more or less (loop marginal slit or sinus, near the middle, at the termina-
tion of a revolving band usually seen on all the \\lmrK: sinus sometimes
closed, excepting at interval^, so as to leave a series of isolated openings
in tho revolving hand.

Tin- animal of the- Upical genus (I'lmrotomaria) of this extensive, and interest-
ing family, n<i\v so nearly extinct, has not, we believe, been ill x-rilx-d. That of
S-'i^in-ill't, however, an existing genus apparently related to this family (though
its shell is not pearly within), has been studied by Mr. Lucas Barrett, who describes
it as follows: "Tentacles long, serrate, at the base of which arc placed the eyes;
foot furnished with two pointed lappets, and two long, slender, serrated cirrhi on
each side. Opercnlnm \ery thin, ovate, with an obscure, snbspirul nucleus. No
part of the animal was external to the shell. The only living specimen occurred
at llammerfest, in torn -MX fathoms of water."

The family PleurotumnriUlaB was represented during the Palaeozoic and several
later epochs, by a great number of beautiful shells, presenting elegantly sculptured
surfaces. It seems to stand, as it were, between the Trochula: and the Hnltuiiiln ,
though authors are not agreed in regard to its relations to these and some of the
allied groups. It includes the genera Pleurotomaria, Plalyachitma, Sdsfnirella?
Miti-<'/iixi,niti, Trocltotoma, and Polytremaria. The Palaeozoic groups &uoayAaln»
(as typified by such forms as E. jpentangulatiis, Sowcrby), Sralitcs, 7i'rr/;/<tWwiia,
l/i/!i-»ti»na, and some undcscribcd genera from the older rocks, seem also to be
related to this family.

Genus PLEUROTOMAIIIA, DEFRAJJCE.

Sy*m.— Anatomut [V.], MOSTTOBT, Conch. 8ytl. II, 1810, p. 278.

1'leurolomaria, DsrBAXCK, Diet. Sci. Nat. XLI, 1826, 381.— MEBKI, Sjrnon. 1828; and ib. 1830, 55.— D»-

M.AYB8, Kncyc. Meth. Ill, Ub. 1830; and ib. 1832; 780.
Ktym. — vxiufa, side ; TI/UM, to cat.
Examp. — Pteurotomaria Quoyana, FWCUEB.

Shell trochiform, or more or less- conical, pearly within, and variable in thickm -^
according to the species, with or without an umbilicus; volutions angular, flat-
tened or rounded. Surface variously ornamented with stria?, nodes, granulations
or carina?. Aperture subquadrate, semi-oval, suborbicular or subrhombic ; inner
lip usually thin ; fissure of outer lip generally narrow and deep ; revolving baud
corresponding in breadth with the sinus.

The shells included in this genus arc very similar in form, and the possession of
a fissured lip, to those of the recent genus Scismirella, but differ in size and tex-
ture— all the known species of ScissureUa being minute, non-perlaceous shells.
The Pleurotomarias also closely resemble the genus Analomu*, of Montfort, from
which Ilormannsen and some others think they arc not distinct. Other authors
regard SciasnrrUa, D'Orbigny, and Anatomits, of Montfort, as synonymous. Judg-
ing from Montfort's description of the genus Anatomus, however, it seems scarcely
possible that it can be identical with ScitmtreUa, since he distinctly states that
the typical species of his genus is a pearly shell, and that the animal is without

46 PALAEONTOLOGY OF THE UPPER MISSOURI.

eyes. From all the facts, it seems to be much more probable that Anatomus and
Pleurotomaria are identical, than that either belong to the same genus as /Scissn-
rella. If they are synonymous, of course Montfort's name Anatomus must be
adopted, since it has priority of date. Until their identity is more satisfactorily
determined, however, we prefer to retain the name Pleurotomaria.

The founder of this genus divided it into two sections, one including the um-
bilicated species, with a rounded aperture, and the other those without an umbilicus.
These sections have, been regarded by other authors as distinct genera, but there
are so many intermediate gradations connecting the umbilicate and imperforate
species, that it is scarcely possible this can be regarded as a generic character. It
is quite probable, however, that distinct genera have been confounded under the
name Pleurotomaria, amongst the fossil species.1

The genus Pleurotomaria was introduced at an early period, a number of species
having been described from the Lower Silurian Rocks. It is also represented
through the succeeding formations, and is particularly abundant in the Coal
Measures of the Western States. It attained its greatest numerical development
during the Jurassic epoch, and is well represented in the Cretaceous strata ; since
the deposition of which it has rapidly declined. At present but two living species
are known, one of which occurs on the coast of Marie Galante, and the habitat of
the other is unknown. Both of these species are very similar to some of those
found in the Jurassic and Cretaceous rocks. The Palaeozoic species, as might be
expected, retain no traces of their original pearly lustre, though some of those
found in the more modern rocks are still nacreous.

Pleurotomaria humerosa.

(PLATE I, Fig. 14, a, 6.)
Pleurotomaria humerosa, MEEK & HATDEN, Proceed. Acad. Nat. Sci. Pliila. Doc. 1858, 262.

Shell turbinate, or conical subovate ; spire turreted, moderately elevated. Volutions five to five and a half, very
convex, more or less obliquely flattened above, rounded below, and distinctly angular at the outer margin of the
flattened upper side. Suture distinct ; columella with a small shallow umbilical perforation. Surface ornamented
by about ten rather strong revolving lines, only some three or four of which are visible on the upper whorls below
the angle ; on the flattened upper surface of the whorls there are five to seven additional, much smaller revolving
striae, sometimes obsolete on worn specimens. Aperture snborbicular.

Length, 0.62 inch ; breadth, 0.50 inch ; apical angle about 62°.

None of the specimens of this species we have seen have the lip entire, and as
the lines of growth are not preserved, it is impossible to determine the nature and
position of the labial sinus and spiral band. From analogy, however, we would
suppose the band to occupy a position just outside of the angle of the shoulder,
and of course the sinus of the lip, in that case, would be near the point where it is
intersected by this angle.

This shell seems to be rather closely allied to Pleurotomaria Yvanii, Leveille

1 Hcrmannsen places Plychomphalus, Agassiz (Germ. Trans. Sowerby's Min. Gonch. .1837, 23,
222, 310), as a synonym of Pleurotomaria. We are not well enough acquainted, however, with the
type of Prof. Agassiz's genus (Helidna compressa, of Sowerby, from the Lias), which we only
know from an examination of Sowerby's imperfect figures, to express an opinion in regard to its
relations.

CARBO N I I KROTJ8 AQB. 47

(sp.). as figured by Koninck, on pi. 37 of his work on the Carboniferous Fossils of
Belgium. It is considerably smaller, ho\\e\ i r. has one or two whorls less, and
proportionally larger, and less numerous re\ol\in^ lines below the shoulder; while
those above are smaller in proportion to the breadth of the flattened upper side.
It is also related to /'. *///<*/// i/n/u, of Meek & NVortheii (1'roc. Acad. Nat. Sci.
I'liila. ()( t. Is(iO), but has a more elevated .spire, while the upper side of its whorls
are more distinctly flattened, and shouldered.

Lm'otiti/ inn I y/.-.s/V/,,/,. — Grasshopper Creek, Northeastern Kansas. Coal Mea-
sures. (Type 10()-_>.)

Pleurotoiiiaria *iibfiirbinata.

(Pun I, Fig. 13.)
rieurntomaria lublurbinala, MIKK it HAYDEX, Proceed. Acad. Nat. Sci. Phil*. D«o. 18S8, 264.

Shell small, comparatively thick, obliquely conical ; spire moderately elevated, rather pointed at the apex.
Volutions fix to six and a half, convex, and angular in the middle, obliquely concave above, and having around
the mi. lil I.- of the last, just below the angle, a rather narrow, shallow, revolving inlcni. Umbilical region a little
depress.*!, and perforated by a very small pit ; aperture snborbicnlar. Surface ornamented by small revolving
Hues (ouly preserved on the under and outer sides of the body whorl, in cur specimen, which Is somewhat worn
and shows no lines of growth;. Angle on the middle of the whorls apparently double, or composed of two
parallel lines.

Length, 0.36 inch; breadth, 0.29 inch ; spiral angle regular, divergence 69°.

AVe have seen no specimens of this species with the lip in a condition to show
the nature and position of the sinus ; nor are the lines of growth sufficiently well
preserved to indicate the position of the spiral band. It is probable, however,
from the appearance of the specimens, that the band is coincident with the sulcus
below tin angle on the middle of the body whorl.

Locality ami jivtsition same as last. (Type 1003.)

48 PALAEONTOLOGY OF THE UPPER MISSOURI.

CARBONIFEROUS AGE.

(PEBMIAN PEEIOB.)

MOLLUSCA.

CLASS LAMELLIBRANCHIATA.

FAMILY PECTINIDJ3.

Shell suborbicular, inequivalve, nearly or quite equilateral, very slightly
oblique, and more or less distinctly auriculate ; not nacreous, and without
a prismatic structure. Hinge line straight ; ligament marginal. Carti-
lage generally confined to an internal pit or groove under the beaks ;
sometimes occupying linear furrows in a cardinal area. Anterior margin
of one valve more or less deeply notched, or sinuous, for the passage of
the foot or byssus. Scar of the adductor muscle large, and subcentral ;
pallial line simple.

Animal with mantle freely open and provided with double margins, the
inner one of which is fringed with pendent filaments, and the outer
bounded by a row of distinct ocular dots, or rudimentary eyes. Palpi
smooth externally, and pectinated on their inner sides ; mouth surrounded
by foliaceous leaflets. Gills equal, each pair partially folded upon itself.
Foot small, cylindrical, grooved, forming a byssus while the animal is
young. Sexes united.

The Pectinidce are closely related to the Spondylidce, which form a natural
transition to the Ostreidce. They differ, however, in the more regular form of
the shell, and in never being attached by the substance of the valves. They also
generally want the strong interlocking teeth of the typical SpandylidcB, and the
animal differs in having a more developed foot and numerous ocular dots.

In order to include in this family some extinct forms apparently belonging here,
it seems to be necessary to admit at least two distinct sub-families, distinguished as
below-: —

1. Pcctiuinae.

Shell with anterior ear usually a little larger than the other ; cartilage occupying an internal pit or groove

under the beaks.
Includes the genera Pecten, Vola, Camptonectes, Amussium, Syncycloncma, Hemipecten, and many undescribed

living and extinct genera.1

1 We have been informed by Prof. Agassiz that he has recently studied this family with much
care, and that he finds it necessary to establish numerous new genera, which he has not yet published,
making, with those already established, more than fifty distinct genera, living and extinct.

OABBONIFBBOUB AGK !• !•: K M I A N ri:iii<)i>. r.t

'.I. * 1 II ll! «>-|>C( tllllll. I .

Shell with posterior ear generally larger than the other; hinge without a central cartilage pit; cartilage

apparently mvupving a aerie* of linear furrow* in a more or leu broad cardinal area.
Includes Aticuloiiteten, .VrrV.^.rm, and probably several undefined 1'aUeoaoic genera.

The A'-i, a/,, /Hrt, n f^muii seems to form a kind of transition from the l\<-ih,i<l«
tn tin- /%/•//< A r, and may pnsMlily lie distinct frnin them both, though it i- evidently
inure closely allied tn the former than the latter. It seems to bear much the some
relations to the- typical forms of the Pcctinidas that the PteriniinoB do to the typical

Pteriil" .

SUBFAMILY AVICULOPECTININ^E.
Genus AVICULOPECTEN, McCor.

Synon. — Arirula, Pecteii, and Melt<ijrina (ip.), of various authors.

. l. „••/„/„.•/,», Mct'oT, Ann. Mag. Nat. HUt. VII, 1851, 171 ; Brit. Pal. FOM. 1852,392.
Klym. — Arirvla and Pecten.
Eiamp. — Aviculnjiecttn docent, McCor.1

\nimal unknown. Shell inequivalve, more or less inequilateral; straight, or
slightly extended obliquely towards the posterior side; anterior ear flattened,
smaller than the posterior, sharply and deeply defined, with a notch in the right
valve between it and the body of tho shell for the passage of the byssus;2
posterior ear pointed, extending about as far as the margin of the shell, de-
fined or not; ligament confined to a narrow3 facet along the hinge margin; no
medial cartilage pit ; muscular impression and pallia! scar as in Pecten, (McCoy.)

We entirely concur with Prof. McCoy in separating this group of shells both
from Ptcria (= Avicida) and Pecten. From the typical species of the latter of
these genera, they differ materially in having the cartilage extended along the
hinge instead of occupying a mesial pit under the beaks ; they also present the
external difference of having the posterior ear larger than the other. From the
Ptcrias they arc clearly separated by their more equilateral and less oblique form,
edentulous hinge, and the arrangement of the cartilage, as well as by their shell
structure.

Some difference of opinion exists in regard to the family relations of this genus,
several authors placing it in the Aviculidce, and others with the Pectinidce. \\ <•

1 In first proposing this genus in the Annals and Mag. Nat. Hist. (VII, 1851, p. 171), Prof.
McCoy does not say what species he regards as the type, thongh he figures, as an illustration of the
genus, a species (without a name), which seems to be his A. docens ; at any rate it is clearly con-
generic with that form.

1 Judging from Prof. McCoy's figures of Palaeozoic Peclinidx, in hili Synopsis of the Carboniferous
Fossils of Ireland, the byssal sinus would seem to be sometimes as strongly defined under the anterior
ear of the right, aa well as the left valve, in Aviculopecien ; or there is another genus presenting that
character.

1 Some of our American species have a broad cardinal area, marked with distinct cartilage fur-
rows ranging parallel to the hinge line, or sometimes divaricately deflected under the beaks.

7 June, 1864.

50

PALAEONTOLOGY OF THE TAPPER MISSOURI.

are decidedly of the opinion, however, that it is more nearly allied to the latter.
It is true these shells have no internal cartilage pit, but we have ascertained that
they have the shell structure of the Pectinidce, and not that of the Ptenidce.

The annexed cut shows the structure of Aviculopecten amplus, Meek & Worthen,
as seen in a fragment placed in Canada balsam, under a magnifier of 350 diameters.1

It will be seen that there is here no traces of the prismatic cellular structure of
the Pteriidce. The shell, on the contrary, is composed of very thin lamina;, with
striated or corrugated surfaces as in the Pectinidce. These striae are not parallel on
the different lamina?, nor on the opposite sides of the same layer, but arranged so
that on looking through several of these plates they are seen crossing each other
at various angles. From this structure, therefore, taken in connection with the
form and general appearance of these shells, it is manifest they belong to the Pec-
tinidce, or possibly to an intermediate group between that and the Pteriidce.

This genus was probably introduced during the deposition of the Devonian rocks.
It attained its maximum development during the Carboniferous epoch, and is also
represented in the Permian rocks, the deposition of which it seems not to have
survived.

Avicnlopecten

(PLATE II, Fig. 10.)

Comp. Pecten cleavelandicus, SWALLOW, Trans. Acad. St. Louis, I, Feb. 22, 1858, p. 182.

We are in doubt whether or not this shell is identical with Prof. Swallow's
species cited above, and consequently prefer not to describe it as new, though we
suspect it may prove to be distinct. It certainly does not appear to have presented
the same proportions, judging from his measurements, which make the height and
breadth of his species as 1.63 to 0.95; though we think there must be a typo-
graphical error in these figures, since P. cleavelandicus is described as being
" orbicular." It would also seem to differ from our shell in being " oblique."

Locality and position. — Kansas ; near Chapman's Creek, eighteen miles above
Fort Riley. Permian beds.

Aviciilopecten McCoy!.

(PLATE II, Fig. 9.)

Shell under medium size, broad subovate exclusive of the ears ; not oblique, rounded on the ventral margin, and
having a moderately, deep, rounded sinus under each ear. Hinge margin sloping slightly from the beaks, and
equalling about three-fourths the breadth of the widest part of the valves below. Left valve gibbous ; umbo convex,
its sides converging at an angle of about 85° to the apex ; ears nearly equal, the posterior one being a little larger
and more angular than the other. Anterior ear somewhat rounded at the extremity, separated from the swell of

' The lines are too straight and regular in this cut. Wood engraving is not well adapted to the illustration of
such objects.

CARBONIFEROUS A (i I. I' K It M I A JJ PE R 1 OD. 51

the ntubo by an oMi.jne, rather iWp, rounded depression. Surface ornamented by simple, rounded, unequal radi-
ating costs-, which are crossed by exceedingly fine, regular, closely-arranged concentric stria, and a few stronger
marks of growth.

(if tin- sixty ur seventy radiating costs) seen on the left valve, *ome nine or ten occupy each ear — those on tb*
anterior ear being a little coarser and more distinct than on the other. On the body part of the valve, about every
fourth or sixth one of tho cosUe is a little larger than the others, and provided with a few distant, rather regularly
disposed, vaulted, scale-like projections, which may, on well-preserved specimens, sometimes assume the character
of short spines. Only the largest cost* extend quite to the apex of the beak, while another series nearly reaches
it ; a third series dies out from one-half to two-thirds of the way up from the border, and a fourth extends
^.-n.-rally less than half way up.

la, from the ventral margin to the hinge, 0.83 inch; breadth, or greatest transverse diameter, 0.7S inch;
l.r.M.lth of narrowest part just under the ears, 0.46 inch ; length of hinge, 0.49 Inch; convexity (of left valve),
n.±J inch.

This species may be distinguished from any of those resembling it in other
rrspei -K yet known to us from these rocks, by the rugose or subspinous character
of its largest cnsta-, mid its fine concentric stria?. It bears some resemblance to A.
.-, ,/fi/ntitx, McCoy (British Pal. Foss. pi. 3, E, fig. 1), but is a proportionally
narrower shell, has ;i .shorter Imijjr, and more slender costae. It also probably
differs in tho possession of the fine concentric lines mentioned above, though Prof.
McCoy's specimen was apparently not in a condition to have retained these, if it
ever possessed them.

Named in honor of Prof. Frederic McCoy, of Dublin, Ireland, the author of
the genus.

Locality and position. — South Cotton-Wood Creek, Kansas. Permian beds.

FAMILY PTERUD^E. (Sec page 27.)

SUBFAMILY PTERIXIIN^E. (See page 28.)

Genus MYALINA, KONINCK. (See page 30.)

Iflyalina avicnloides.

(PLATS II, Fig. 8, a, b, e, rf.)
ifyalina nviculoiritt, MKKK & HATDEIC, Proceed. Acad. Nat. Sci. Phila. May, 1860, p. 184.

Shell subtrigonal, higher than long, very convex, or snbangular down the nmbonal slopes ; anterior margin dis-
tinctly sinuous above the middle, thence descending with a slightly convex curve, nearly at right angles with the
hinge to the basal extremity, which is narrowly rounded. Posterior side compressed, Its margin curving a little
forward above, or intersecting the hinge at right angles ; slightly convex and nearly perpendicular along the
middle, below which it curves obliquely forward to the abruptly rounded basal extremity. Hinge straight, nearly
equalling the length of the shell ; beaks very convex, snbangular, and curving rather abruptly forward, so as to
become nearly or quite terminal. Surface having moderately distinct concentric marks of growth.

Length, 1.48 inch ; height, 1.66 inch ; convexity of a left valve, 0.32 inch.

This form may be readily distinguished from all the other species of the genus
known to us, resembling it in other respects, by its peculiar sinuous, or arcuate
front, and the extended or somewhat lobed character of its anterior margin under
the beaks. Young or undeveloped individuals are generally longer than high, and
have much more oblique umbonal slopes than adults. As the shell advanced in
size, however, the umbonal ridges curved down so as to stand nearly at right
angles to the hinge, and the valves became elongated in the same direction, so as
to make the height greater than the length. Usually the anterior margins of the

52 PALAEONTOLOGY OF THE UPPER MISSOURI.

valves below the most sinuous part are deflected from the umbonal slopes rather
abruptly inwards, so as to meet at an obtuse angle, or sometimes almost on the
same plane.

Locality and position. — Cotton- Wood Creek, Kansas, south of Kansas Eiver.
Permian beds. (Type 3961.)

inyalina permiana.

(PLATE II, Fig. 7, a, b, C.)

Mytilus (Myalina) pcrmianus, SWALLOW, Trans. St. Louis Acad. Sci. Vol. I, March 8, 1858, 17.
Mytilui (Myalinal) concavus, SWALLOW, ib. 18.

Shell obliquely subovate, or subtrigonal ; convex anteriorly, and cuneate behind ; beaks terminal, rather pointed,
and directed nearly horizontally forward at the points. Umbonal slopes prominent from the beaks down along the
front of the valves. Hinge straight, generally more than equalling half the greatest length of the shell, and ranging
at an angle of 60° to 65O with the oblique anterior margin ; cardinal area of moderate breadth, and distinctly striate.
Posterior margin rounding down with a broad sweep from the posterior extremity of the hinge, to the abruptly
rounded antero-ventral extremity ; anterior margin concave, or more or less arcuate in outline from the beaks to the
base, and very abruptly inflected from the prominent umbonal ridge of each valve. Surface marked by obscure
concentric strise, or nearly smooth.

Length, from the beaks to the antero-basal extremity, 1.75 inch; length of hinge, 1.08 inch; breadth, 0.96
inch ; convexity, about 0.70.

Prof. Swallow's descriptions of the two forms cited above, agree so nearly with
the specimens before us, that we can scarcely entertain a doubt in regard to their
identity, especially when we bear in mind that they came from the same beds, at
near the same locality. Our specimens also show various gradations between the
shorter and more elongate forms, so that we cannot believe a specific distinction
can be based upon these differences.

This species is evidently very closely allied to a shell described by Dr. Isaac Lea,
of Philadelphia, from the Coal Measures of Pennsylvania, under the name of
Modiola wyomingensis (Jour. Acad. Nat. Sci. Phila. vol. II, 2d ser. p. 205, pi. xx,
fig. 1). Dr. Lea's figure seems to represent a slightly more oblique shell, with a
little longer hinge ; but as the species before us is variable in these characters, we
are prepared to believe the Kansas and Pennsylvania shells may possibly prove to
belong to the same species. If so, Dr. Lea's specific name will have to be adopted,
since his paper was published in 1852.

The species under description may be distinguished from our M. perattenuata, by
its more robust appearance, broader form, and less attenuate beaks. It is probably
also a thicker shell than M. peraitemiata, though our specimens being all cast, we
are not sure this is the case.

Locality and position. — Trom Permian beds near the Smoky Hill fork of Kansas
River ; on Cotton-Wood Creek, and at many other localities south of Kansas and
Smoky Hill River, in northeastern Kansas. We think we have also seen it in the
Coal Measures below, in the same region. (Type 1153.)

CARBO N I I KROUS AGE. PE RM I A N PERIOD. 53

PTERIIX^E. (Sec page 28.)

(Jonns ITMICROTIS, MI:I:K.

n. — GrypkiUi (ap.)i SCHLOT. Aca.l. Munch. 1816, 30; ib. Petref. 1820, 292.

I .,,l,i (sp.), •>• "« C. SOWEBBT, Tram. Oeol. Soc. Load. 2d c«r. HI, 1829, 119, and of various other* (not

KI.KIX ; LAHK.).

.)/•..,,.//., Kix.i, Catalogue Perm. Kons. 1849, p. 9 ; Id. Monogr. Perm. FOM. Great Brit. 1850, p. 164 —
MKKK & HATDKH, Trans. Albany Inst. IV, Marcli 2d, 1858.— SWALLOW, Trans. St. Lonii Aoad. Sol. I,
1858. — SIICXAKII, ib. 1859 (not RKOXH, 1830).

Eumicrotit, MEEK, American Jonr. Sci. 2d ser. XXXVII, March, 1864, p. 216.
Ktyat.- '"V'f- small; «T<, ear.

if. — .l/oiio/i'i Uavni, MEEK & HATPKN.

Shell snborbirnlar, plano-convex, the left valve being usually very convex, and
tin- ri^'ht flat, or <\cn a little concave; not distinctly auriculato, the ears being
nearly obsolete. JJeaks SH!M cntral, very slightly oblique, unequal, that of the left
valve often elevated, gibbous and incurved; the other very small, and scarcely
projecting above the hin^e line. Hinge short, narrow, edentulous; cartilage
ca\ ity under the beaks (King). Byssal notch or sinus of right valve narrow, deep,
and separated from the hinge by a very small rudimentary car, which docs not
projeet l>< \ond the margin. Adductor muscular scar large and sub-central, im-
pressions of retractor muscles several, small and placed near the beaks. Surface
generally with radiating, more or less vaulted or scaly costac, much more distinctly
marked on the left than the right valve.

The shells embraced in this genus arc apparently most nearly allied to Aucella
of Keyserling, to which Prof. McCoy refers them. Although Count Keyserling's
genus has not been generally adopted, it seems to be entirely distinct from all the
allied groups, and has been clearly defined by its distinguished author. AH the
species upon which it was founded, however, differ from those of the group under
consideration, in being much more oblique, more oval in form, and entirely desti-
tute of any traces of radiating costac or stria? ; while they are all marked with more
or less distinct and regular concentric costae or undulations, as in Inoceramna.
Again, they have the right or smaller valve proportionally more ventricose than in
I'.itin'n •/•<>/ /x. and also possess a minute, internally concave, sharply defined anterior
ear under the beak of the left valve, never seen in the group we are describing.
Another difference is the entire absence of the lobed appearance of the posterior
side of the valves in Aucella, so often seen in the typical forms of Eumicrotw. In
addition to these differences, Count Keyserling's figures (Peischora Land, tab. 16)
show that in the type of his genus the scar of the adductor muscle is nearly
marginal ; and that there is no distinct cartilage cavity under the beaks ; while
according to Prof. King, there is in E. spcluinur'ni, Schlot. (sp.).

That the group of shells we are describing are not congeneric with Monotis of
Bronn, must be manifest to any one who will take the trouble to compare one of
these forms with Monotin .-<t/iii<in'<t, the type of Bronn's genus. This shell, it will

54 PALAEONTOLOGY OP THE UPPER MISSOURI.

be observed, differs from all of those included in the genus Eumicrotis, in being more
oval in outline, more compressed, more oblique, and very nearly if not quite equi-
valve ; while very little difference can be seen between the prominence of its right
and left beaks. Its most important peculiarity, however, is the total absence of
any traces of a byssal notch or sinus in the anterior margin of either valve.

The typical forms of the genus Eumicrotis are, so far as known, confined to the
Permian rocks in Europe, and to the Permian and upper Carboniferous of America.
In addition to the type — E. Hawni, M. & H. — this genus includes E. speluncaria,
Schlot. (sp.), E. radiatus, Phillips (sp.), E. Garforthensis, King (sp.) ; and E. Halli
and E. variabilis, Swallow (sp.).1

A small section of this group, of which Avicula substrlata of Munster is an ex-
ample, seems to be mainly confined to the Jurassic rocks, though it may also be
represented in the Trias. These shells should probably rank as a distinct subgenus,
though with our present means of comparison we are not fully satisfied that this is
the case.

Some Palaeontologists will insist upon referring to the genus Pteria (Avieula), all
such forms as those included in the groups above characterized. A moment's com-
parison, however, of these shells with the recent typical forms of that genus, can
scarcely fail to convince any skilful Conchologist that such a mingling of types is
totally inadmissible in our present advanced state of Natural History.

Eumicrotis Hawni.

(PLATE II, Fig. 5, a, b, c.)

Monotis Hawni, MEEK & HAYDEU, Trans. Albany lust. IV, March 2d, 1858.
Monotis speluncaria, var. americana, SWALLOW, Trans. St. Louis Acad. Sci. 1, 184.
Monotus speluncaria, Shumard 1 1859, Trans. St. Louis Acad. Sci. I, 396 (non SCHLOT.).
Eumicrotis Hawni, (M. & H.) MEEK, Am. Jour. Sci. XXXVII, March, 1864, 216.

Shell subcircular, or subovate ; hinge straight, equalling about half the length of the valves ; beaks sub-central,
short, not oblique ; ears nearly obsolete ; base rounded, antero-ventral and postero-ventral margins rounded, the

1 Prof. King suggests that the genus including E. speluncaria probably belongs more properly to
the Pectenidse than to the Aviculidee, since Mr. Carpenter had found that Avicula cygnipes of Phillips,
supposed to be congeneric with E. speluncaria, presents the microscopic structure of the Pectenidee,
and not that of the Pteriidx. We think, however, that it is very improbable that these two shells can
be congeneric, for we find our E. Hawni, which is even specifically very closely allied to, and certainly
congeneric with, E. speluncaria, shows very distinctly, under a high magnifying power, the prismatic
structure of the Pteriidae. The annexed cut, No. 1, represents the structure of this species as seen

No. 1. No. 2.

Shell structure of E. Hawni. Shell structure of E. carte.

by transmitted light, when magnified about 300 diameters. We also observed the same Structure in
the Jurassic species Eumicrotis curta, Hall (sp.), as may be seen by the annexed cut, No. 2.

In regard to the relations of Avicula cygnipes, of Phillips, to Monotis salinaria, Bronn, we would
merely state that we differ widely from those who would place two such shells in the same genus.

CARBON I FKKOUS A<i I! C K K M I A N PERIOD. ;,;,

Utter being somewhat more prominent than the other. Left Yalve convex ; anterior margin sometime* alight)/
sinuous near tin* hinge abore ; posterior margin intenectlng the hinge at an obtain angle ; beak convex, extending
bat slightly beyond the hinge line. Uight valve nearly or quite flat ; beak flat, not projecting beyond the hinge ;
byssal sinus narrow, deep, or extending back parallel to tin- liingn to a point nearly under the beak.

Surface of both valve*, particularly the left one, ornamented with more or less distinct radiating cost*, which
are usually separated by spaces three or four times their owu breadth, and armed with regularly disposed vaulted,
•pine-like prominences, formed apparently by the projecting lamina) of growth. Between each two of the principal
cosUe from one to three or four much smaller radiating ribs or lines are usually seen, crossed by obscure con-
centric markings. (Hinge and muscular impressions unknown.)

Length, 1.47 inch ; height, 1.42 inch ; convexity, about 0.40 inch.

In first describing this species, we called attention to its close relations to E,
*•/»/;/„/-,;/•/'</, Schlot. (sp.), and stated that we were aware it would not be easy
always to find characteristic differences by which certain varieties of these two
forms could be diltinguiihed. Every naturalist, however, must have met with
analogous cases, when- the \arieties of two closely allied, but variable species
approximate, and, as it were, mingle together, so as to render it sometimes ex-
tremely difficult to separate them; while the normal forms of each are so clearly
distinct as to leave no doubt on the mind that they belong to different species.
ThN. we think, is the relations the Kansas shells bear to E. ttpehtncaria, although
we are aware some of our friends entertain the opinion that they are not specifically
distinct.

It is true, some specimens agree almost exactly with such varieties of E. epelun-
i-nrin as arc represented by figures 15, 17, 20 and 21, pi. xiii, of King's work
on the Permian Fossils of England ; yet out of hundreds of individuals, collected
and seen by us in Ixan-:i-. \\ehavo never met with one presenting the peculiar
lobed and sulcated posterior, so characteristic of the well developed normal forms
of E. sjtelnncaria, such, for instance, as figures 5, 6, 7, 8, 9, 10 and 11 of plate xiii,
in King's work cited above. Again, none of our Kansas specimens, with a solitary
exception, has the beak of the right valve so gibbous, or near so elevated, as those
represented by the figures last above cited ; and in this single exception, the shell
differs so widely in other respects, that if not a monstrosity, we can but regard it
as belonging to a distinct species from that under consideration, as well as from E.
speluncaria.

Locality and position.— Near the mouth of Smoky Hill fork of Kansas River,
and at several places on the high country between there and Council Grove, as well
as on Cotton-Wood Creek, Kansas. Permian. (Type 3958.)

l.iiiiiirrotiw Hawni, var. ovntn.

(1'LATK II, Fig. 6, a, b.)

This variety differs from the typical forms of M. Hawni, in being more compressed, and more ovate In ontline,
its diameter from the hinge to the ventral margin being proportionally greater; while its hinge margin is much
shorter, or not more than equalling about one-third, instead of one-half, the greatest breadth of the valves. Its
costs: are also usually more distinctly defined, and its beak rather more pointed. In some respects it resembles
M. Garfortlieiutt, King, bnt its costs? are not so uniform, nor so spinons. We are Inclined to think it will prove to
be specifically distinct from K. llaicm ; bnt as we are not clearly satisfied that this is the case, we merely name it
for the present as a variety of that species.

Diameter, from hinge to ventral margin, 1.54 inch ; breadth, 1.43 inch ; convexity of left valve, 0.28 inch.

Locality and position. — Near Cotton- Wood Creek, south of the Santa Fe Road,
Kansas. Permian. (Type 1157.)

56 PALAEONTOLOGY OF THE UPPER MISSOURI.

SUBFAMILY MELINLN"^. (See page 28.)
Genus BAKEVELLIA, KING.

Synon.-Mytilite* (sp.), SCHLOT. Akad. Munch. VI, 1816, 30 ; ib. Petraf. 1820, 293.

Avicula (sp.), J. DB C. SOWEKBY, Trans. Geol. Soo. 2d ser. HI, 1829, 119.— QOLDF. Petref. 2d part, 1826,
126, and of several others (not [KLEIN] LAMK.).

Bakevellia, KING, Catalogue, 1848, 10.

Gervillia, GEINITZ, Versteinerungen, 1848, 10 ; ib. Dyas, 1862 (not DEFKANCE, 1820).
Etym.— Dedicated to Robert Bakewell, of Hampstead, England.
Type. — Avicula antiqua, MUNSTBB.

Shell more or less aviculiform, subequivalve ; valves somewhat sinuous and a little
gaping in front for the passage of the byssus. Umbpnes depressed and oblique.
Surface with concentric strise. Hinge provided with a few linear anterior and
posterior lateral teeth, arranged nearly or quite parallel to the cardinal margin.
Muscular scars much as in Pteria (Avicula), excepting that the anterior one 'is
larger and more distinct. Cardinal area usually well developed in both valves;
cartilage furrows distinct, two to five in each valve.

Animal unknown.

In form, as well as in the possession of a more or less developed anterior and
posterior wing, and the inequality of the valves, the species of this genus are often
very similar to Pteria ; from which, however, they differ in the possession of a
large, deeply grooved cardinal area, and a divided cartilage, as well as in the
nature of the hinge teeth, and the proportionally larger size of the anterior muscu-
lar impression.

In the possession of a broad cardinal area, crossed by a few deep furrows for the
reception of the cartilage, the Bakevellias seem to present affinities to the genus
Gervillia, which some of the species closely resemble in form. The nature of the
hinge, however, and the greater development of the anterior muscular scar, clearly
separate them from that group, at least generically.

Prof. King, the able author of the excellent Monograph of the Permian Fossils
of England, thinks the comparatively large size of the anterior muscular impression
in this genus, sufficiently marked, not only to separate it from Pteria, but to remove
it entirely from the Pleriidce. Still in the rather low, or nearly sub-central position
of the posterior muscular impression, when taken in connection with the general
similarity of these shells to Pteria and Gervillia, they seem to present a combina-
tion of characters bringing them very near, if not within the Pteriidce,

In Europe, the genus Bakevellia is generally regarded as being restricted to the
Permian System. If the following described species, however, really belongs to
this genus, it would seem to have been introduced at a somewhat earlier period
here, since we have seen it in Kansas in beds we regard as probably of the age of
the Coal Measures, though it ranges up, and is most abundant in the Permian beds
above.

CARBONIFEROUS AQB. PE 11 M I A X PERIOD. 57

Bnkevellia parva.

(1>LAT« II, Kig. 12, a, A.)

BaJcnellia parva, MEEK & UATDIX, Tram. Albany Inst. IV, March 2.1, 1858.

Shell very small, obliquely subovate, oblong, or subrhombic in outline ; valves gibbons along the oblique nmbonal
slope*. Antero-ventral margin sloping very obliquely backwards and downwards ; rather distinctly sinuous uinli-r
tin- l.i-.ikM. I'oatero- banal extremity roauded ; anal edge sinuous above; anterior extremity somewhat lobed, sub-
angular or very narrowly rounded. Hinge line straight, nearly or quite equalling the greatest length of the shell, and
ranging at an angle of about :>."i to tlio nmbonal prominences. Beaks rather small, rising a little above the hinge,
incurred, and located about half way between the middle and the anterior extremity. Postero-dorsal region com-
preesed, or more or lens alatv, and terminating at a distinct angle at the extremity of the hinge. Surface with
concentric striae. Anterior teeth of hinge, one or two to each valve, linear and declining a little in front ; posterior
ti-i-tli. one or two, long, linear and ranging parallel to the hinge margin.

Length, 0.20 Inch ; height, (Me in, -h ; thickness or convexity of the valve*, about 0.08 inch.

We can scarcely regard it as a clearly established fact that this little shell
prNMMM ;ill tin- characters of Prof. King's genus Buki nll'ia, since its cardinal area
and muscular and pallia! impressions have not yet been seen. It agrees, however,
MI exactly in form and general appearance, as well as in the nature and arrange-
ment of its hinge teeth with that genus, and differs so materially in the latter
character and the absence of a l>\-vil sinus from Pteria, that we do not feel war-
ranted in removing it from the genus in which we first provisionally placed it.

It agrees very nearly in form with some varieties of Bakevellia antiqua, Munster
(sj>.), but is uniformly much smaller — never being more than one-fourth the average
si/e of that shell; while its cardinal area must be much narrower, judging from
the close proximity of the beaks ; the posterior extremity of its hinge is also much
more angular.

Locality and position. — Near the mouth of Smoky Hill fork of Kansas River;
on Cotton-Wood Creek, and at numerous other localities in northeastern Kansas ;
in beds of yellowish magnesian limestone of Permian Age. (Type 3959.)

FAMILY TRIGOXIID^E.

Shell equivalvo, generally inequilateral, closed, varying greatly in
form and ornamentation, according to the several genera and smaller
groups, nacreous within. Ligament external ; hinge composed of a few
diverging, usually large, interlocking teeth.

Animal with two recumbent gills on each side ; palpi simple ; mantle
open ; foot long, lanceolate, bent, and formed for leaping.

This family includes the following genera: Schizodus, Myophoria, Trigonia, and

V, rti<-< n-il in ? The first two of these genera are entirely extinct, while the Trigonias,

which were most abundant during the Jurassic and Cretaceous epochs, are still

represented by a few living species. Of the genus Verticorrfia, only one or two

Tertiary species, and one living species are known.

In tracing the different groups of this family, from its first appearance in the
Palaeozoic rocks, as plain shells (Schizodus) with smooth weak hinge teeth, it is

8 liar. 1864.

58 PALAEONTOLOGY OP THE UPPER MISSOURI.

exceedingly interesting to see how gradually they shade off through the smooth,
subplicate, and plicate Myophorias of the Trias, with their more developed hinge,
into the highly ornate Jurassic, Cretaceous, and living Trigonias, with their still
more complex dental system.

Genus SCHIZODUS, KING.

Synon.—Telllnites (sp.), SCHLOT. Akad. Munch. VI, 1816, 31.

Axinus (obscurus), SOWEEBT, Min. Con. IV, 1821, 12.

Isocardia (axiniformis), PHILLIPS, Geol. York. 1836, 209.

Cucullsea (Schlotheimi), GEINITZ, Neues Jahrb. 1841, 638.

Donaxf (sulcatus), J. DB C. SOWEEBT, Geol. Tr. V, 1840, 491.

Sedgwickia (gigantea), McCov? Garb. Foss. Ireland, 1844, 62.

Dolabra' (part), McCoy, Carb. Foss. Ireland, 1844, 64.

Myophoria, McCoy, 1855, Palaeozoic Foss. Great Brit. 1855, 494 (not BRONS, 1855).

Schizodus, KINO, Ann. Mag. Nat. Hist. XIV, 1844, 313.
Etym. — fx}&i I split ; oJouc, a tooth.
Type. — Schizodus truncatus, KIHG.

Shell more or less oval or subtrigonal ; anterior side rounded and shorter than
the other; posterior side tapering, more or less truncate at the extremity, and
usually having an umbonal ridge extending from the beaks to the postero-basal
margin. Beaks generally prominent. Surface smooth, or ornamented with con-
centric striae. Hinge with two smooth cardinal teeth in the right valve, and
three in the left ; the middle tooth of the left valve being more or less bifid, and
fitting between the two of the opposite valve. Free margins smooth.

Animal unknown.

As pointed out by Prof. King, this genus is closely related to Myophoria, of
Bronn. Prof. McCoy has also subsequently expressed the opinion that the slight
differences observable between the teeth of the hinge in these two groups are not
of generic value, and ranges the species under Bronn's name Myophoria.2 As we
have had no opportunity to examine specimens showing the hinge, we merely retain
provisionally, the name proposed by Prof. King. We would remark, however, that
so far as we can judge from figures alone, we are inclined to think that the non-
plicated Carboniferous and Permian species, with possibly a few of the similar
forms from the Triassic rocks, should be retained under Prof. King's name, either
as a distinct genus, or as a subgcnus under Myophoria.

Prof. King has also called attention to the close relations between tnese two
groups and the genus Trigonia ; the principal difference between them, so far as
the hinge is concerned, being the greater development, and sulcated character of

1 As proposed by McCoy, the genus Dolabra was made to include species belonging to two distinct
families. The first or typical species, Cucullsea angusta, Sw., and three others included by McCoy,
constitute the genus Dolabra as properly restricted, by the separation of the species upon which Prof.
King founded the genus Schizodus. As thus restricted, the genus Dolabra belongs to the Arcidx,
and seems to be closely allied to Cucullsea, Lamk. Dolabra? alpina, Hall, Iowa Report, I, part 2,
p. 716, pi. xxix, fig. 2, is a true Schizodus, and its name should be Schizodus alpinus.

3 British Pal. Foss. p. 494.

CARBON" I FERGUS AGE. PERMIAN PERIOD. 59

the teeth in the latter <jr<>u]>. Kxternally, the differences between the Trigonias,
and tlic plicated, or costatcd species of Mi/ojifim-in. are about as great as those
between the latter and the smooth txpical species of Schizodus.

The ^eiius ,W/ /';<*/«.», as above detined, was probably introduced during the de-
poMtion of the I'pper Silurian rocks.1 It also occurs in the Devonian,* and is
most common in the Carboniferous and Permian deposits. If any of the species
included in the genus Mi/<,/>/ii»-i<i, by Bronn, belong to this group, it must have been
represented during the Triassic epoch.

SchizodiiN ovalus.

(PLATE II, Pig. 11, 0, 6.)

Axinai (SeAiWiu) ornlut, Mm & HATDis, Proceed. Acad. Nat. Scl. Phtla. Deo. 1858, 262.
Comp. .SVAunr/w Irunentiu, King, Permian Fossils England, p. 193, pi. XT, fig. 25 to 29, inrlaaire.

Shell longitudinally orate, moderately convex, the most gibbons portion of the valve* being slightly In advance
of the middle. Anterior side broader than the other, bnt somewhat narrowly rounded ; posterior tide more con-
tracted— compressed and obliquely truncated above, and snbangalar below ; base forming a regular aemi-orat«
cnrve, the most prominent part of which is in advance of the middle. Cardinal margin short, straight, and inter-
secting the obliquely truncated posterior edge at an angle of about 130°. Beaks rather elevated, incurved at right
angles to the hinge, and placed a little in front of the middle ; posterior umbonal slopes prominently rounded, or
subangnlar from the beaks to the postero-baaal extremity. (Surface, muscular, and pallial impressions unknown.)

Length, 0.65 inch ; height, 0.45 inch ; convexity, 0.32 inch.

This species is very closely related to S. truncatw of King, and may possibly
prove to be identical, when a direct comparison of specimens can be made. It is
more nearly like his fig. 27, pi. xv (Permian Fossils) than any of the other varieties
represented by him, but differs in being more sharply rounded in front, while its
beaks are a little more depressed. Its posterior umbonal slopes appear also to be
less prominent than in any of his figures of S. truncatus.

Locality and position. — South Cotton-Wood Creek, Kansas ; in Permian mag-
nesian limestone. It also occurs there in lower beds containing many Coal Measure
species. (Type 3960.)

FAMILY NUCULANTD^E.

Shell longer than high, subovate, oblong or subelliptical, equivalve,
usually somewhat pearly within; hinge provided with small interlocking
cardinal plates or denticles, as in the Nucvlidw ; ligament internal or
external; margins of valves smooth within; pallial line more or h >s
sinuous.

Animal with mantle margins open, fringed, and usually provided with
ventral lobes ; labial palpi very long, convoluted ; siphons rather long,
slender, partly united and retractile ; gills plumose, attached throughout
their length. Foot deeply grooved, geniculate, and usually with serrated
margins.

• Anodonlopsis securiformi*, of McCoy, is apparently an Upper Silurian example of this genus.

• Murchison, Verneuil, and Eeyserling refer to this genus, a species (S. devonicua) from the Devo-
nian Rocks of Russia.

GO PALAEONTOLOGY OF THE UPPER MISSOURI.

This group has been divided by Conchologists into two subfamilies, as follows : —

1. Niiculaiiinae.

Shell pearly within ; ligament internal.
Including Nuculana and Yoldia.

2. Malletinae.

Shell with ligament external ; valves sometimes slightly pearly within.
Includes Malletia and Ncilo.

SUBFAMILY NUCULANIM.
Genus YOLDIA, MOLLER.

Yoldia, H. P. C. MOLLER, Kroyer's Nat. Tid. 1842, IV, 91 ; Ind. Moll. Green. 18 ; Cf. Zeitschr. f. Mai. 1844, 12.
SynM. — Maldia, GRAY (misprint), 1847. Leda and Nucula (sp.), of various authors.
Etym.— Dedicated to the Countess Yoldi.
Examp. — Nucula limatula, SAY.

Shell ovate or subelliptical, subequilateral, more or less compressed ; posterior
side narrower than the other. Surface smooth, striate or obliquely sculptured, and
covered with a polished epidermis. Margins smooth within ; inner laminae slightly
pearly. Hinge plaits small, and more or less numerous on each side of the beaks ;
cartilage occupying a pit under the beaks. Pallial line distinctly sinuous.

I

The genus Yoldia is closely allied to Nuculana, but may be distinguished by its
deeper pallia! sinus, and usually less prominent beaks. From Nucula, which it
resembles in the crenulated character of the hinge, it will be readily distinguished,
not only by the presence of a sinus in the pallial line, but by its less distinctly
nacreous, and differently formed shell. The animals in these two genera are also
different.

We are not sure this genus dates back to the Palaeozoic epoch, though some of
the Carboniferous and Permian species present exactly 'the form and external
appearance of true Yoldias. Some of the Triassic and Jurassic species usually re-
ferred to the closely allied genus Nuculana (j= Leda), probably also belong to this
genus. Several of the Cretaceous species, figured by D'Orbigny in the Palaeon-
tology of France, under the names Nucula and Leda, seem to be typical Yoldias.

The genus Yoldia was represented by a few species during the Tertiary epoch,
and probably attains its greatest development in the existing seas. The recent
species are chiefly found in northern and antarctic seas, and occur on the coast of
Greenland, Kamtschatka, Massachusetts, &c.

Yoldia? siibscitula.

(PLATE II, Fig. 4, a, b.)
Leda subscitula, MEEK & HAYDEN, Trans. Albany Inst. IV, March 2d, 1858.

Shell of medium size, rather narrow subovate, moderately convex in the central and nmbonal regions. Posterior
half more compressed and subrostrate, very narrowly rounded at the extremity ; anterior extremity less narrowly
rounded. Base forming a broad semi-ovate curve, the most convex part of which is slightly in advance of the
middle ; dorsal outline convex, and declining a little in front of the beaks, somewhat concave and nearly hori-
zontal behind them. Beaks moderately prominent, and nearly central. Hinge straight or sloping slightly from
the beaks, near which a few fine crennlations are visible in the cast.

Length, 0.60 inch ; height, 0.26 inch ; breadth or convexity, about 0.17 inch.

CARBONIFEROUS AGE. PERMIAN PERIOD. 61

The only specimens of this species we have seen, are internal casts, which give
int idea nl' tlie Mirl'ace marking. \Ve have also been unahlo to make out the nature
of the muscular and pallia! impressions, and have therefore only placed it in this
genus from the (lose analogy of its form to typical species in more recent formations.

Lm-iiUti/ ninl fioii/iini. — Near the mouth of Smoky Hill fork of Kansas River,
and on Cotton- Wood Creek, as well as at other localities in the Permian beds of
northeastern Kansas. (T\pe 3957.)

FAMILY CRASSATELLIDJ3. (See page 34.)

Genus PLEUROPHORUS, KINO, 1844. (See page 34.)

PlcurophoriiM ? Mihciincatus.

.<*> LATE II, Fig. 3.)

Pltvrnphnnu tubeuneatui, MBKK k HATDKK, Trans. Albany Inst. IV, March 2d, 1858.
Plrurofihonut tubcuneatut, MKEK & HATDKH, Proceed. Acad. Nat. Sci. Pbila. June, 1859, 29.

Shell small, longitudinally oblong, the basal and cardinal margins being parallel, and the extremities rather nar-
rowly rounded ; valves moderately convex ; beaks depressed, and located near the anterior end. Hinge long,
straight, or slightly arched ; cardinal teeth unknown ; posterior lateral teeth parallel to the hinge margin, and
remote from the cardinal teeth. Impression of the anterior addnctor muscle deep, sabtrigonal, and located close
to the margin — internal ridge on its posterior side well defined, ranging nearly vertically ; impression of the pedal
muscle distinct from, and located directly over, that of the anterior addnctor; posterior muscular impression very
faint. Surface with fine concentric strias.

Length of a medium sized specimen, 0.54 inch ; height, 0.24 inch ; thickness or convexity, 0.19 inch.

In form and general appearance, as well as in the character and position of its
anterior adductor muscular scars, and its posterior lateral teeth, internal ridge, &c.,
this species agrees quite well with the typical species of Prof. King's group Pleuro*
I>linru8. It differs, however, in having the scar of its anterior pedal muscle nearly
marginal, instead of farther back, while the casts show scarcely any traces of the
radiating costs; generally well marked on those of that genus.

It also agrees very closely with a small shell figured by J. de C. Sowerby,
under the name of Uhio phaseolus (Trans. Gcol. Soc. Lond. 2d ser. vol. V, p. 491),
and subsequently referred, by Prof. Koninck, to the genus Cardinia. Indeed these
shells are so closely similar, that, judging from the figures and descriptions we have
seen of the European form, we have some doubts whether they may not prove to
be specifically identical. We think it scarcely possible that they can belong to
different genera. Possibly both should be referred to Carbonocola, McCoy ( =
Anthracosia, King).

This species will be known from our P. occidental-it, by its greater height in the
anterior region, and more prominent antero-ventral border. It also seems to differ
in being, as above stated, nearly or quite destitute of the radiating plications seen
on that shell.

Locality and position. — Near the mouth of Smoky Hill fork of Kansas River ;
at the head of Cotton- Wood Creek, and at numerous other localities in north-eastern
Kansas. From layers of yellow Magnesian Limestone of Permian age. (Type 4181.)

62 PALAEONTOLOGY OF THE UPPER MISSOURI.

Pleurophorus ? Calhoiini.

(PLATE II, Fig. 13, a, t.)
Edmondia? Calhotini, MEEK & HAYDEX, Trans. Albany Inst. IV, March 2d, 1858.

Shell longitudinally subovate, gibbous over the oblique umbonal slopes. Extremities rather narrowly rounded ;
base forming a broad semi-elliptic curve, sometimes nearly straight along the middle ; dorsal side declining rather
gradually from the beaks posteriorly, and more abruptly in front. Hinge straight, apparently thickened within, so
as to leave on internal casts a slightly impressed lanceolate area, along the cardinal region behind the beaks.
Umbones moderately prominent, oblique, and placed a little nearer the anterior extremity than the middle.
Anterior adductor muscular impression rather deep, broad ovate, and located near the buccal edge ; scar of the
pedal muscle small, oval, deep, and located near the margin of each valve, a little above the impression of the
anterior adductor. Posterior muscular impression shallow ; pallial line rather distinct (and undoubtedly simple).

Length (of an internal cast), 1.45 inch ; height, 0.75 inch ; convexity, 0.80 inch.

Since first referring this species with doubt to the genus Edmondia, we have
satisfied ourselves that it cannot be retained in that genus ; there being no traces
left in well preserved internal casts, of the cardinal appendages for the attachment
of the cartilage, as in Edmondia. Although we now place it provisionally in the
genus Pleurophorus, we are not clearly satisfied in regard to its relations to that
group ; indeed, so far as we can determine from impressions of the hinge left in
the matrix, it does not appear to have been exactly like that of the typical species
of that genus.

This species may be at once distinguished from the last, by its larger size, pro-
portionally shorter form, and less prominent internal ridge just behind the anterior
adductor scar — as well as by its more prominent umbones, which are also placed
farther back.

Locality and position same as last, (Type 4184.)

CARBONIFEROUS AGE. PERMIAN PERIOD. 63

CEPHALOPODA.

ORDER '1Y< rabr.im lu.i < ;i.

FAMILY NAUTILIDjE.

Shell curved, involute, or rarely spiral ; outer or last chamber capacious,
sometimes deflected from the curve of the inner whorls, and more or less
straightened ; aperture usually sinuous on the dorsal or outer side. Septa
simple, or with a few undivided lateral lobes or flexures ; concave on the
side facing the aperture. Siphon varying in its position between the
inner and outer, or dorsal and ventral margins, according to the genera
and species ; rarely (in older extinct groups) occupied by an internal
organic deposit ; nearly always piercing the septa backwards from the
aperture; envelope usually solid and persistent.

For what is known in regard to the structure of the animal in the recent typical
genus of this family, we are mainly indebted to Prof. Richard Owen, of London.
According to this distinguished comparative anatomist, the powerful parrot-like
mandibles of the recent Nautilus pompilua are surrounded by a fleshy lip, around
which are four groups of labial tentacles, numbering twelve to thirteen each. Out-
side of these, on each side of the head, are thirty-six brachial tentacles or arms,
arranged in a double series ; the dorsal pair being expanded and connected so as
to form a hood, which partly closes the aperture of the shell when the other
appendages are retracted. The tentacles are laminated on their inner sides, and
capable of being drawn within sheaths apparently homologous with the eight arms
of the Cuttle-fish. There are also four ocular tentacles — one behind and one
before each eye. The respiratory funnel is formed by the folding of a thick lobe
which extends laterally on each side of the head, with the free edge directed
backwards into the branchial cavity. The mantle is firm and muscular as far back
as the line of the shell muscles, beyond which it is transparent. Its margin is
entire, and extends to the edge of the shell. The siphon is vascular, and connected
with the pericardium.

Most Palaeontologists include in the family NatUilidce., an extensive group of older
fossil shells presenting a great diversity of forms and other characters : such, for
instance, as Phragmoceras, GompTuxieraa, Endocerae, Orthoceras, Huronia, Aplo-
ceras, &c. — probably belonging to one or more distinct families. As here defined,
the family Nautilida: is intended to include the following groups: Nautilus,

64 PALAEONTOLOGY OF THE UPPER MISSOURI.

Discites, Trematodiscus^ TemnocJieilus,1 Northoceras, Pteronautilus,2 Lituites? Hor-
tolus ? Cryptoceras, Clymenia, Sulclymenia, Aganides (= Aturia), Nautiloceras,
Aploceras, and Trochoceras, with probably some undescribed Jurassic, Triassic and
older genera.

GENUS NAUTILUS, LINN^US.

Synon.— Nautilus, BBEIHIOS, Dissert. Polyth. 1732, 12-14.— LIHN. (part), Syst. Nat. ed. 10, 1758, t. i, 709.— BBUG.
Encyc. Meth. I, 1789, p. xvi.— LAMK. Prodr. 1799, 79 ; and Syst. 1801, 99.

Oceanus, MONTF. Conch. Syst. 1808, p. 58-9.

Ammonites, IB. 74-5, not (BKEYN.— LINN.KOS).

Ellipsolithes (sp.), SOWEBBY, Min. Conch. I, 1814, 56 (not MOXTF. 1808).

Omphalia and Nautilus, DE HANN, Mon. Amm. 1824.

Simplegas (sp.), BLAINVILLE, Diet. Soi. Nat. torn. 32, 185 (not Simplegades, MOJTTF. 1808).
Etym. — MimX*, a sailor or navigator.
Type. — N. pomiiilius, LINN.'^INN.

Shell subglobose or more or less compressed ; umbilicus closed or open ; volu-
tions coiled in the same plane, merely contiguous, or more or less deeply embracing.
Septa simple or somewhat arched or waved on the lateral margins; siphon
generally central or subcentral. Surface smooth or variously striate or costate
and furrowed ; in some of the older extinct species ornamented with nodes. Lip
generally more or less sinuous on the dorsal and ventro-lateral margins.

1 In the June number of the Proceed. Acad. Nat. Sci. Phila. 1862, p. 147, the subgenerie name
Trematodiscus was proposed by the writer and Mr. Worthen, for such fossil species as Nautilus
strigalis, N. Edwardsianus and N. omalianus, Koninck ; and N. sulcatus, N. pinguis, &c., Sowerby.
Since that time we observe Prof. McCoy had proposed, in 1844 (Garb. Foss. Ireland), the name
Temnocheilus for a group including some of the same forms. .As his first species, however (N.
biangulatus, Sowerby), and several of the others ranged by him under that name, differ considerably
in form and surface characters from the types for which the name Trematodiscus was proposed, it
may be convenient to restrict Temnocheilus to such forms as N. biangulalus, Sowerby ; and N.
pinguis, and N. coronatus, McCoy ; and to retain Trematodiscus for those agreeing with its type as
originally proposed. If it should be thought desirable, however, to group all these forms together,
Prof. McCoy's name Temnocheilus would have to take precedence, as it was first published.

It is also worthy of note that Blainville had, in 1824 (Diet. Sci. Nat. torn. 32, p. 185) included
some similar forms under the name Simplegas, adopted from Montfort. It will be remembered,
however, that the type of Montfort's genus Simplegades (not Simplegas), is an Ammonite or Cera-
tite ; while the first, or typical species of Simplegas, Blainville, is a true Nautilus.

In 1842, Mr. G. B. Sowerby adopted, in his Manual (p. 276), Blainville's name Simplegas, and
figures as an illustration of the group N. sulcatus, Sowerby, a typical Trematodiscus. Although he
writes the name Simplegas, he cites Montfort as the author of the group, and yet admits that the
type of Simplegades, Montfort, has sinuous septa like Ammonites.

* The name Pteronautilus is proposed for a remarkable undescribed Permian genus, of which
Nautilus Seebachianus, Genitz, is the type (see Dyas, p. 43, tab. 11). It may be characterized as
follows: —

GENPS Pteronantilus, MEEK.

Shell with the involute body portion comparatively very small and globular in form, scarcely umbilicate. Outer
chamber very large, and deflected from the involute body, its inner or ventral side being widely open, and the
lateral margins greatly dilated, so as to form a very large wing-like expansion on each side.

Conchologists will readily understand that such a shell as this must have been inhabited by an
animal differing widely in its structure from a living typical Nautili.

CARBONIFEROUS AGE. PERMIAN PERIOD. 65

Of the largo number of older fossil species referred to the genus Nautilus, some
undoubtedly belong to distinct genera, while others fall into subgeneric groups,
differing more or less from the recent typical forms. If we admit Discites, Trema-
/i*//.srtw, Cryptoceraa and several other equally marked forms into this genus, we
nia\ regard it as dating back to the Silurian epoch. Species approximating the
typical Xuntili, ho\\e\er, did not exist, so far as known, before the Carboniferous
period, and even the few of modern aspect then introduced, present peculiarities
in their septa, or in the position of the siphon, that readily distinguish them from
the more recent types ; while the great majority of their supposed congeners of
that epoch are still more aberrant. The same may also be said in regard to the
known Permian species.

In the Triassic and Jurassic rocks, along with some of more modern aspect, we
meet with a number of species which, from the lobed or sinuous character of their
septa, and other peculiarities, seem to form sections or sub^enera, and apparently
in some instances, distinct genera. The Cretaceous and Tertiary rocks, as might
be expected, contain a larger proportion of true Nautili, but even, in the Tertiary,
the older type of structure is repeated in the genus Aluria, of Bronn (= Aganides,
Montfort?), which, with a ventral si ph uncle, has deep lateral lobes in the septa,
similar to those of Goniatites.

Some five or six recent species of Nautilus have been described by Conchologists.
They are found in the Chinese and Indian Seas, Persian Gulf, &c. As they have
rarely been seen alive, little is known in regard to their habits.

.Vmiilii- ecccniricuti.

(PLATB II, Fig. 14, a, h.)
Nautilut rrcentricta, Mm & HATDKI, Trans. Albany Ingt. IV, 1868.

Shell small, somewhat compressed ; rotations apparently not more than one and a half, not embracing, rounded
excepting near the aperture, where the non-septate portion presents an oval transverse section. Umbilicus wide,
•hcllow, and showing all of each whorl. Septa moderately concave ; siphon small, placed about half way between
the centre and the outer, or dorsal side. Aperture transversely oval. (Surface unknown.)

Length, 0.70 inch ; height, 0.53 inch ; breadth at the aperture, 0.43 inch; small diameter of aperture, 0.26 inch.

We have some doubts in regard to the propriety of retaining this species in the
genus Nautilus, since it seems to consist of little more than one entire whorl,
apparently surrounding an open central space. In this character (if it is not due
to some accident), as well as in the eccentric position of the siphuncle, it would
seem to present affinities to the genus Gyroceras ; from which, however, it differs
in having the whorls coiled so as to come in contact. Excepting in the rounded
or non-sulcate character of the whorls, it appears to approach the group Tremato-
discus.

Locality and position. — Near the mouth of Smoky Hill fork of Kansas River.
Permian. (Type 4185.)

June, 1864.

66

PALEONTOLOGY OP THE UPPER MISSOURI.

REPTILIAN AGE.

(JUKASSIC PERIOD.)

RAD I AT A.
CLASS ECHINODERMATA.

ORDER Criiioiclea.

FAMILY PENTACRINID^E.
Genus PENTACRINITES, MILLER.

Synon.— Pentacrinites (ScHLOT.), MILLER, Nat. Hist. Crinoid. 1821, 58.— GOLDF. Petref. Germ. 1, 1826, 168.— ROEMER,
Ool. 1836, 29 ; Kreid. 1841, 26.— BKON. Leth. Geog. 1836, 219.

Pentacrinus, AQASSIZ, Prodr. Mong. Ech. Mem. Soc. Sci. Nat. Neuchatel, 1835, 195 ; and various later authors.

Chladocrinus, Aa. ib. 196.
Etym. — writ, five ; xpiW, a Lily.
Examp. — Pentacrinites briareus, MILLER.

Column more or less distinctly pentagonal, with central cavity small and
rounded ; provided with lateral branches or accessory arms arranged in verticils ;
segments ornamented with star-like sculpturing on their upper and lower surfaces.
Body small, composed of five small or rudimentary basal plates, and fifteen larger
radials, in five series of three each, without inter-radial pieces. Visceral cavity
protected by a covering of numerous very small polygonal plates. Arms large,
long, frequently bifurcating, and provided with numerous jointed tentacles.

Prof. Agassiz separates this group into two sections, as follows : —

1. Pentacrinites (proper).

Column with lateral branches simple.

2. Chladocrinus, or Cladocrinus.

Lateral branches of column themselves provided with verticillate branehlets.

Probably the most ancient known species of this genus are from the St. Cassian
beds of the Tyrol, often referred to the Trias, but by some included in the
Jurassic system. The genus attained its greatest development during the deposition
of the Jurassic rocks ; but occurs in the Cretaceous and Tertiary deposits, and is
represented by a few species in our existing seas. It has not been found in this
country east of the Black Hills.1

1 It is an error, we think, to quote Pentagonites, Rafinesque (Jour, de Phys. LXXXVIII, 1819,
429), described by him, with other fossils from some of the Palaeozoic rocks of the Western States, as
a synonym of Pentacrinites. On the contrary, his type was more probably one of the Silurian Crinoids

REPTI I.I A \ AGE. JURASSIC PERIOD. 67

Pcutacrinites nateriscus.

(I'LATK III, Fig. 2, a,b, and annexed cut?)

Penlaerinui (utrritcui, Mine & HATDK.X, Proceed. Acad. Nat. Sot. I'hila. March, 1858, p. 49 ; Men & HATDBX, Ib.

Oct. 1860, 419.
Comp. Penlacrima tcalarii, OOLDF. Petrefact. Oerm. tab. 62, fig. 3 ; also Quenntedt Der. Jura, tab. 13, flg». 49-S7.

Our knowledge of this crinoid is entirely derived from detached segments of its
column, and other parts, us seen imbedded in a sandy matrix, cemented by calcareous
mutter. '1 IK joints of the column may be characterized as rather small, thin, very
symmetrical pentagonal star-shaped bodies, the rays of which are usually a little
longer than wide, and somewhat acutely angular at their extremities. Through
the centre of each of these joints, there is a minute circular perforation, from which
five lance-oval petaloid areas radiate, one to the extremity of each of the angles ;
the areas being bounded on each side by rather narrow, slightly elevated crenulate
margins.

This description applies more particularly to the largest sized specimens, measur-
ing about 0.18 inch across from point to point of the opposite angles (see PI. Ill,
fig. 2, a, b.) Associated with these, there are smaller joints,
varying from 0.05, to 0.10 inch in diameter, having propor-
tionally shorter and broader rays, which are usually less angular
at the points than those of the larger ones. These may possibly
prove to belong to another form, though it is quite as probable
they are only joints of smaller individuals of the same species.
The annexed cut represents some of these smaller less distinctly
angular columns, from a locality on North Platte River.

The specimens are all so very similar to the corresponding parts
of P. scalaris, Goldfuss, that after more careful comparisons we
are inclined to the opinion that they may possibly prove to belong
to that species. Still, as they are all much smaller than those
figured by Goldfuss and Quenstedt, and none of them have the
points of the rays so rounded, we have concluded to retain our
name until their difference or identity can be established by a .

, . Pentacnnitet mttructut

comparison of specimens. North p^ MMr>

Locality iiit<l /loxltinii. — Associated with other Jurassic fossils
at the southwest base of Black Hills ; and opposite Red Buttes, North Platte River.
(Type 220.)

for which Prof. Hall subsequently 'proposed the name Heterocrinus (Pal. N. Y. Vol. I) ; which has
a distinctly pentagonal column, and is common in the Bine Limestone of the age of the Hudson
Hirer Oronp, in Ohio, Kentucky, and Indiana, as w*ell as New York. Rafinesqne's name, however,
cannot be adopted for this Palaeozoic group, since he gave no characters by which either the genus
or the typical species, could be certainly identified.

PALAEONTOLOGY OF THE UPPER MISSOURI.

MOLLUSCA.
CLASS BRACHIOPODA.

FAMILY LINGULID^E. (See page 1.)
Genus LINGULA, BRUGUIERE.

St/non.—Lingula, BBTTO. Encyc. Meth. I, 1792, tab. 250.— CUVIEK, Tab. Elem. 1798, . . . ; Ann. Mus. I, 1802, 69.—

LAMK. Prodr. 1799, 89 ; Syst. Ann. 1801, 140.

Pharetra, BOLTKN, Mus. Bolt. 1798, 2d ed. 1819, 111 (not Hubn. 1816).
Etym. — Linyula, a little tongue.
Type. — Lingula anatina, LAMK.

Shell oblong or more or less oval, depressed, thin, gaping at each end, and
rounded or subtruncate in front, and more or less pointed at the beaks — con-
sisting of alternate corneous and testaceous laminae, the former of which are fibrous
and the latter tubular ; composition largely phosphatic. Valves both moderately
convex, held together by the action of muscles; beak of ventral valve more
pointed and prominent than that of the other. Surface smooth, or marked by
concentric lines, sometimes crossed by radiating striae. Peduncle long, thick,
cylindrical, fleshy, and flexible.

On the inner side of the shell of the typical forms of this genus, the marks of
the visceral sac and the scars of the complex muscular system occupy most of the
posterior half of the valves. In the dorsal or shorter valve, this visceral area has
a somewhat rhombic or suboval form, and in the ventral valve its outline is ovate-
cordate, or more or less flabelliform. The area thus designated is usually thicker
in both valves than other parts of the shell, especially in old examples, so as to
leave a slight impression on internal casts.

Of the muscular impressions, the form and position of which have been noted,
there are twelve in the dorsal, and thirteen in the ventral valve. The scar of the
peduncular muscle is situated immediately within the beak of the ventral valve ;
and just in front of it is the scar left by the divaricator muscles (of Hancock =
posterior adductors of Woodward). At the anterior extremity of the visceral area,
in the middle of the same valve, are the four very unequal scars of the posterior
occlusor, and external and central adjuster muscles (of Hancock), which are so
arranged and impressed as to impart a more or less trilobate outline to the anterior
margin of the slightly more convex visceral area. Behind these, and just within
each lateral lobe of the visceral area, are situated, one on each side, the widely
separated anterior occlusor scars ; and still further back, we see on each side those
of the posterior adjusters, of which there are two on one side, and one larger on
the other.

i; i:r i ILIAN AGE. JURASSIC PERIOD. 69

In tin- dorsal valve, there is no peduncular attachment, but the scar of the
divariciitor muscles is located nearly as in the other valve. The two anterior
occlusor impn -ssions of this valve are placed in contact, centrally, side by side, at
the farthest anterior cxtremiu of the visceral area; and just behind these, and a
little separated from each other, are the two impressions of the posterior occlusor
muscles. About midway between the latter and the posterior extremity of the
\ i-i . ral area are situated, near each lateral margin, the small scars of the posterior,
external, and central adjuster muscles, of which there are four on one side, and
three on the other, one of the latter being considerably larger than the others.

This genus is closely allied to the recently separated Lingulcpis, and until the
muscular impressions of the type of that proposed genus have been more clearly
determined, there is some room for doubt whether or not it is really distinct. The
principal differences jet observed between these two types, consist in the ovate
suh trigonal form, and more attenuate beak in /,///</*//</</>» ; and the much more
distinctly trilobate visceral scar of its ventral valve. The visceral scar of its dorsal
\al\e is also more flabelliform than in the typical Lingulas.

The genus I/nujnla was introduced at a very early period; at any rate, we find
species in no way distinguishable from it, at least by any external characters, in
some of the oldest of the Silurian rocks. Its remains are likewise found ranging
through all subsequent formations, and several species are known to inhabit our
existing seas. It seems to have attained its maximum development during the
Silurian Age. The living species arc found on the coast of California, the Sand-
\\ich and Philippine Islands, and on the shores of South and North Carolina, and
the West Indian Island of St. Thomas. They inhabit shallow water, being gene-
rally found at low tide, with their long peduncle deeply penetrating the sand or mud.

Lingula brevirofttri*.

(PLATS III, Fig. 3, a, i.)

Lingula breriroilrit, HKVK A HATDEV, Proceed. Acad. Nat. Sol. 1'hila. March, 1858, p. 50 ; Id. Ib. Km. & HATDKH,
Oct. 1860, p. 419.

Shell Bubovate, varying to Rpatnlate-ovate, very thin ; lateral margins nearly straight, or somewhat convex,
generally converging a little towards the beaks ; front sabtrnncate or abruptly rounded ; cardinal extremity
narrowly ronnded. Beaks obtuse and apparently not extending beyond the cardinal margin. Valves equally
convex along the middle, and compressed towards the front and sides. Surface polished, and marked by fine,
rather oltfcure lines of growth ; on the surfaces of the inner laminae traces of extremely fine longitudinal stria
are sometimes visible by the aid of a magnifier.

Length, 0.57 to 0.58 inch ; breadth, 0.33 to 0.35 inch ; convexity of the two valves, 0.16 inch.

This shell bears some resemblance to the Oolitic species L. Bcanii, Phillips, but
is generally broader toward the front, and more obtusely rounded at the cardinal
extremity.

Lot-ii/it// and position. — Southwest base of the Black Hills, Idaho Territory —
lower part of the Jurassic rocks of that region. (Type 206.)

70 PALEONTOLOGY OF THE UPPER MISSOURI.

FAMILY RHYNCHOKELLID^E.

Shell oval, oblong, subtrigonal or globose, fibrous and impunctate;
hinge line curved, and without a proper cardinal area ; dental lamiiue
varying with the genera ; supports of oral appendages short and curved,
or rarely developed into spiral calcified coils, which are always arranged
vertically ; muscular impressions much as in Terebratula.

Animal, in the living representatives of the family, attached by a
muscular peduncle passing through an aperture under the beak of the
larger valve ; oral arms fleshy, spiral, flexible, and attached to the small
curved processes of the smaller valve, towards the middle of the con-
cavity of which the apices of the coils are directed ; mantle not adhering,
fringed with a few short setas.

The shells of the Rhynclionellidce have sometimes much the appearance of some
forms of the Terebratulidce, but may be distinguished by the absence of a rounded
perforation at the extremity of the beak, by their impunctate structure, and differ-
ently formed brachial supports. From the Spiriferidce, some types of which they
also resemble in form, they are distinguished by the general absence of calcified
spiral appendages, or where they do exist, by the apices of the spires being directed
vertically, instead of towards the lateral extremities, &c.

This family includes the genera Rhynchonella,Eatonia,Camarophoria, Pentamerus,
Atrypa, Stenocisma,1 Ccelosjyira, and probably Porambonites and Camerella. The type
for which Leiorhynchus has been proposed, and possibly a few other imperfectly
known Palaeozoic genera, may also be found to belong to this family. Only the
typical genus is known to have living representatives in our existing seas — the
other groups being extinct, and, so far as known, confined to the Palaeozoic rocks.

Genus KHYNCHONELLA, FISHER, 1809.

Synon. — Anomia (sp.), LINN^US, and several early authors.

Rhynchonella, FISCHER BE WALDHEIM, Mem. Soo. Imp. Mosc. II, 1809, . . . — BLAINVILLE, Diet. Sci. Nat. t.
XLV, 1827, p. 426.— D'OBBIGNY (part), Compt. Rend. XXV, 1847, 268.— DAVIDSON, Brit. Foss. Brach.
Genl. Int. 1854, 93, and of various other authors.

Trigoriella, FISCHEE DB WALDHEIM, Mem. Soc. Imp. Mosc. II, 1809 (not DA COSTA, 1778).

Terebratulites (sp.), SCHLOT. Petref. 1820, 250.

Hypothyris, PHILLIPS, Palaeozoic Fossils, 1841, 55. — KINO, Ann. Mag. Nat. Hist. XVIII, 1846.

Hemithiris (sp.), D'OBBIOKY, Compt. Rend. XXV, 1847, 268.

Hemithyris, BBONN, Jahrb. F. Min. 246.

Acanthothiris, D'ORBioNY, An. Sci. Nat. XIII, 1850, 223.
Etym. — ;vyx°t, a beak.
Examp. — Terebratula acute, SOWERBY.

Shell oval or trigonal-subglobose ; with or without a mesial fold and sinus;
surface with radiating striae, costae or plications — rarely smooth or spinous. Beak
of larger valve acute, entire, prominent, and more or less curved ; foramen variable

1 See note on page 16.

REPTILIAN AGE. JURASSIC PERIOD. 71

in M/C and form, and placed under the beak, by the incurving of which it is often
doM-d <>r hidden; partly or entirely surrounded (the inner side being sometimes
formed by the nmbo of the smaller valve) by a deltidium, which is composed of two
pieces, and mereh rudimentary, or more or less well developed — sometimes produced
in the form of a short tul>e. Hinge composed of two teeth in the larger valve, and
t \\ 1 1 corresponding sockets in the other ; the teeth being supported by dental plates
which extend to the bottom of the valve. Apophyses of the smaller valve con-
sisting of two short, flattened, moderately curved, and separate laminae, which
curve upwards and are attached to the hinge plate. Impressions of the adductor
muscle in the smaller \al\e. quadruple, well defined, and separated by a short
longitudinal mesial ridge ; scars of the pedicle muscles occupying the cardinal
plates. Shell and pedicle muscles of the larger or perforate valve occupying a
saucer-shaped cavity at the base of the dental plates ; those of the pedicle muscles
narrow, elongate, and placed close to the inner bases of the dental lamina? — the
remaining and larger portion of the cavity being chiefly occupied by the cardinal
muscles, which are separated by a small ridge ; above these is the small oval
adductor scar.

Animal of R. psittacea, according to Mr. Davidson, with visceral mass confined
to a small space near the beaks, and separated from the general cavity of the shell
by a strong membrane, in the middle of which the mouth is situated. Upper lip
plain, and the lower cirrhated. Alimentary canal passing through the deeply notched
hiii^e plates, and terminating behind the point of insertion of the adductor muscle
in the centre of the valve. Pallial veins consisting of four principal branches in
each lobe, opening into larger sinuses. Margins of mantle fringed with a few
short setae.

This genus is of very ancient date, having been represented through the various
geological epochs from the Silurian down to the present time. The species were
quite abundant during some of the Palaeozoic periods, as well as during the deposi-
tion of some of the Jurassic and Cretaceous rocks, particularly in Europe. The
genus seems to be sparingly represented in the Tertiary deposits, and at present
but two or three living species are known. The recent species are never so strongly
costated or plicated, nor so short and subtrigonal in form as many of the older
extinct ones, which, together with some other differences, have led several authors
to think them not strictly congeneric.

Rhynchoiiella

(PLATB III, Fig. 4.)

Our specimens of this shell are too imperfect to enable us to determine satisfac-
torily whether or not it is identical with any known form. In a genus like this,
including so many species, often very closely allied, not much reliance can be placed
upon identifications from a few imperfect specimens. It would be easy to point out

72 PALAEONTOLOGY OP TUP] UPPER MISSOURI.

characters in which it resembles some Jurassic species, but it seems, so far as can
be seen, to be also quite as nearly like others of various ages, even amongst the
Palaeozoic forms.

Those we have examined are small, subrhomboidal, moderately convex, and have
on the dorsal or smaller valve (we have not seen the other) about fifteen simple,
obtusely angular plications, four or five of which are raised near the front, so as to
form a moderately prominent, rather flattened mesial fold. The surface is also
marked by fine, very obscure lines of growth, which are deflected upwards in
crossing the plications, near the front.

Locality and position. — Southwest base of Black Hills (Jurassic), Dakota Territory.
(Type 319.)

CLASS L.AMELLIBRANCHIATA.

FAMILY OSTREIDJ3.

Shell more or less irregular, inequivalve, slightly inequilateral, lying
upon, and generally attached by, the left valve. Beaks straight or
curved ; hinge edentulous ; ligament subinternal ; muscular impression
nearly central, or behind the centre ; pallial line obscure, simple.

Animal with its mantle entirely open, and provided with double,
fringed edges, which are without distinct ocelli ; foot obsolete ; gills
crescent-shaped, and separated from the palpi ; labial appendages tri-
angular, connected around the mouth by a plain membrane.

This family probably only embraces the three closely allied groups — Ostrea,
Gi'yphcea, and Exogyra ; the latter two of which are entirely extinct, excepting a
single species apparently of Gryphcea. The curious extinct genus Eligmus, of
Deslongchamps, is also placed here by some authors, but we are not well enough
acquainted with these peculiar shells to express an opinion in regard to their
affinities.

Genus OSTREA, LINN^US.

Synon. — Ostracites, Ostreites, Limnostracites, Ostreum, &o. (sp.), LLHWYD, KLEIN, and other pre-Linnaean authors.

Ostrea, LINN.BUS, Syst. Nat. ed. 10th, 1758, 696. — 0. F. HOLLER, Prodr. Zool. Dan. xxxi.— BRDO. Enoyo.
Mfith. I, xiii.— LAMK. Syst. 1801, 132, &c.

Peloris, POLI, Test. Utr. Sic. 1791, 33.

Peloriderma, POLI, ib. II, 255.

Lopha, BOLTED, Mas. Col. 1798 (2d ed. 117).

Alectryunia, FISCUEB DE WALDHEIM, Mus. Dem. 1807, and Bull. Mosc. VIII, 1835.— CHENU, Man. Conch. II,
1862,167.

Dendrostrea, SWAINSON, Malacol. 1840, p. 389. — G. B. SOWERBY, Conch. Man. 2d ed. 137.
Etym. — oa-Tfiw, an Oyster.
Type. — Ostrea edulis, LINN.

Shell irregular, subnacreous, laminated, attached by the left or under valve;
surface often ornamented by radiating plications, and more or less imbricating,
or distinct marks of growth. Upper valve flat or concave ; lower valve convex,
and having a prominent beak. Ligament occupying a pit or groove in the cardi-
nal area of each valve. Muscular impression subccntral.

REPTILIAN AGE. JURASSIC PERIOD

Eh veral authors include as suhgenera under this group, f //•///-/«»</. Lamarck, and
/•.'.'••<;////••/, Say; and it cannot In- denied that \\eare sometimes at a loss to determine
to which of these genera a given species should be referred. Indeed, in some
cases, we tind diti'ereiit individuals of the same species presenting various gradations
l)etween the true Ojsters and (inpluras. Whether founded in nature or not, however.
these Croups are convenient, and can generally lie distinguished without diflicnlty.

The genus 0*ir»t appears to date back as fur as the Carboniferous epoch ; at any
rate. Prof. Konim k lias described one species (O. //«//(7/W»w) from rocks of that
age in Belgium. Murchison, Verneuil & Keyserling have also referred to this
genus another species (0. »«<»/»•/>•;//</) from the Permian rocks of Russia. As these,
however, arc, so far as our knowledge extends, the only evidences we have of the
tence of this genus previous to the beginning of the Triassic period, it would
seem to have been \er\ sparingly represented, even during the deposition of the
latest of the Palaeozoic rocks.

Oysters are not uncommon in the Triassic deposits, and the number of species
increases as we ascend through the later formations. The genus is also well repre-
sented, as every one knows, and probably attains its greatest development in the
bays, estuaries, &c. of the present epoch.

Ontrea Engclmanni.

Oitrea Engtlmanni, MKJUC, Proceed. Acad. Nat. Sci. Phila. July, 1860, 311.

This species is only known from imperfect detached valves, all of which are much compressed, thin, and present
a more or less irregular subovate outline. The beak i> truncated, and provided with a broad but short area. The
surface is ornamented by from seven to about fifteen irregular, moderately distinct, rather rounded, radiating plica-
tions, not usually extending more than about half way from the free margins towards the umbo. Lines of growth
regular, rather faint, and not imbricating. Internal margins not crenate near the hinge. Muscular scar rather
large, oval, and well defined.

Length of largest specimen, 3.60 inches ; breadth, 3 inches.

A. Outside under* valve.
10 September. 1S64.

Oitrea Enijrtmanni.

B. Inside of another specimen.

74 PALAEONTOLOGY OP THE UPPER MISSOURI.

This species bears some general resemblance to 0. Marshii, of Sowerby, but is a
thinner and more compressed shell, with less prominent, and much less angular
plications or costse. Its area is also proportionally much shorter.

Locality and position. — Jurassic beds at Red Buttes, on the north branch of
Platte River, Dakota Territory, lat. 42° 50', long. 106° 40' west. Collected by the
Expedition under the command of Capt. J. H. Simpson, of U. S. Top. Engineers.
(No. 1884.)

Genus GRYPH^EA, LAMARCK.

Synon. — Auricularia, Auriculites, &e. (sp.), of LLHWYD and other early writers.

Grypheea, LAMABCK, Syst. An. 1801, 398.— EOISSY, Mol. 1835, 202.— BLAINV. Die. Sci. Nat. t. 19, 1821,
p. 533.— Risso, Hist. IV, 1826, 290.

Griph&a, BLAINV. Malaool. 1825, 522.

Pycnodonta, FISCHER DE WALDIIEIM, Bull. Mosc. VIII, 1835.
Etym.—ytlj., a Griffin.
Examp. — Gryphsca arcuata, LAMK.

Shell generally free, especially in the adult state. • Lower valve deep; beak
prominent and distinctly incurved, and but slightly oblique. Upper valve flat
or concave ; beak usually truncated. Hinge, ligament, and muscular and pallial
impressions as in Ostrea. (Animal unknown.)

The shells of this genus differ from those of the true Oysters in being more
regular, in having the lower valve deeper, and particularly with its beak more
prominent and incurved. They seem also to be scarcely ever plicated as we often
see in the genus Ostrea. From Exogyra they differ mainly in having the beak of the
lower valve curved upwards and inwards, instead of to one side, as well as being
prqbably always without the large plications sometimes observed in Exogyra. Most
of these distinctions, however, particularly the prominence and incurving of the
beak, sometimes become so faintly marked that it is not always easy to separate
the species of these three groups.

This type appears to have been first introduced during the deposition of upper
members of the Triassic series ; at any rate, a few species have been referred to it
from the St. Cassian beds of the Tyrol usually referred to that epoch. It is more
frequently met with in the Liassic and other members of the Jurassic system, and
probably attained its maximum development during the deposition of the Cretaceous
rocks. A few species have been referred to this genus from the Tertiary rocks of
Europe ; though it is doubtful whether or not they are true Gryphseas. No living
examples of the group are known.

Gryphtea calceola, var. nebrascensis.

(PLATE III, Fig. la, b, c, d, e, and annexed cuts.)

Gryphsea calceola, QCENSTEDT, Handb. Petref. tab. 40, fig. 29-31.— QUENSTEDT, Der Jura, 1856, 352, tab. 48, figs.

2, 3, 4, and 5.— MEEK, MSS. Capt. Simpson's Kept. Utah.'
Gryphsea calceula, var. iiebrascensis, MEEK & HAYDBN, Proceed. Acad. Nat. Sci. Phila. Dec. 1861, 437.

Shell, when normally developed, snbovate in small specimens, but becoming more elongate and proportionally
narrower with age. Under valve very thick in the umbonal region ; beak prominent, narrow, produced, and
strongly incurved ; anterior side with a more or less denned sulcus, which never extends quite to the point of the

REPTILIAN AGE. J U K AS8IC PERIO D. 75

beak ; area triangular, arcuate, extending close up under the curve of the beak, and provide.! with a distinct
cartilage drpreuion ; muscular soar small, shallow, oval, and located near the anterior side ; surface ornamented
on the gibbous back of the nmbo by distinct, Irregular, radiating stric, usually extending to near the middle on
mature specimens, while the space between this and tha ventral margin has only moderately distinct concentric
•aria; and marks of growth. Upper valve ovate, nearly flat on the outside, or a little convex near the beaks, and
lu'.r,- or less concave near the middle, usually concave on the inner side towards the cardinal extremity, which Is
U, i. k ami truncated ; surface with rather distinct concentric marks of growth.

Ungth, from the most prominent part of the nmbo to the ventral extremity, 2.70 inches ; breadth near the
ventral extremity, about 1.20 inch ; convexity, 0.73 inch. (Type No. 1881.)

Gryphsca caleeola, Tar. nelirascentit.

A. Side riew lower valve. B. Under side same. C. Inside same. D. Inside view of an upper valve.
E. Upper view of a small specimen with the two valves united.

The normal form of this shell, as may be seen by the above cuts, agrees so very
nearly with Quenstedt's G. caleeola, that we cannot but regard it as most probably
only a variety of that species. It has the same narrow, elongated, arcuate form,
radiately striated umbo, and general appearance of the fully developed specimen
of G. caleeola, represented by Quenstedt's fig. 1, pi. 48, above cited, excepting that
the beak of the under valve seems never to be quite so arched over and produced ;
while the sulcus along its anterior side of the exterior is not continued so nearly
to the point of the beak.

Along with the form above described, we have from the same and other localities
a few specimens with the point of the beak slightly truncated by a small scar of
attachment, much as we see in fig. 4, pi. 48, of Quenstedt, referred by him pro-
visionally to Ostrea caleeola, Goldf.

At some localities nearly all the specimens have the beak truncated, and many
of them seem to have been attached by so large a surface as to have entirely
obliterated the umbo of the under valve, thus giving them all the characters of a
true Oyster. Y\g. \«,l, andJ, PI. Ill, represent some of these specimens, one of wh id i,
fig. \d, will be seen to present very nearly the form and general appearance of fig.
2, pi. 48, Quenstedt, the most extremely abnormal type of the scries. Between
these extremes we find every intermediate gradation, so that it seems to be im-
possible to base specific distinctions upon these differences. We are, therefore,
inclined to regard these shells as all belonging to one variable species, the differ-
ences being probably caused by the more or less favorable conditions of different

70 PALAEONTOLOGY OF THE UPPER MISSOURI.

localities or particular positions. Where the conditions were favorable, the shells
attained a larger size, grew more symmetrically, and present the normal form of a
true Gryphcea ; but where exposed to the action of waves or too strong currents,
they were probably more firmly attached, are smaller, more irregular in form, and
have the umbo sometimes partly, sometimes entirely obliterated by the large scar
of adhesion, which in a few extreme cases occupies the whole lower surface of the
under valve.

From Quenstedt's figures and description of Gryphcea calceola, it is evident he
found it presenting precisely similar variations, or at any rate, that he found a similar
gradation of forms that he refers to the one species, Gryplvoea calceola. Whether
or not our shells really belong to the same species as those figured by Quenstedt,
or to a closely allied representative form, it is not easy to determine, without an
extensive series of specimens for comparison from the American and European
localities. In the absence of such a series we have referred our shells provisionally
to Quenstedt's species.

Locality and position. — The forms represented by the foregoing cuts, A, B, C,D,E,
are from the Jurassic beds of Wind River Mountains, in the southern part of Dakota
Territory. Some smaller, but similar specimens with other less regular forms, were
found in lied Buttes, further east in the same Territory; also at Big Horn Mountains.
The specimens figured on PI. Ill, are from the same position at the southwestern
base of the Black Hills, Dacota Territory.

FAMILY PECTINIDJE. (See page 48.)

SUBFAMILY PECTININjE. (See page 48.)

Genus CAMPTONECTES, AGASSIZ.

Synon.—Pecten (sp.), SOWERDT, Min. Conch. Ill, ISIS, 3.— ROEMEK, Die Vert, des Nord. Kreid. p. 50.— D'ORBIGNY,

Pal. Franc. Ill, p. 592, and of various others (not MDLLER).

Camptonectes, AGASSIZ, MSS. — MEEK, Smitbsouian Catalogue Jurassic Fossils of North America.
Klym. — «af*irTijf, curved ; mxi-n;, a swimmer.
Examp — Pecten lens, SOWEKBY.

Shell thin, subequivalve, lenticular, closed ; hinge generally short, straight,
edentulous ; ears compressed, anterior one of the right valve separated from the
margin below by a well defined, often deep, byssal sinus. Surface ornamented
with radiating, impressed striae, which curve strongly outwards in approaching
the lateral margins, and often present a punctate appearance produced by the
crossing of regular concentric striae. Muscular impressions faint, apparently as in
Pecten. (Animal unknown.)

Prof. Agassiz proposes this genus for the reception of such species as Pecten lens,
and P. obscuntfi, Sowerby ; P. striatoyunctatus, Roemer, P. virgatm, Neilson, &c.
It will probably be also found to include several nearly smooth or concentrically
striated Jurassic and Cretaceous forms, since wo find faint traces of curved, radiating

KKl'TILIAN AGE. JURASSIC PERIOD.

77

nr divaricating stria' mi /'. fW/<f/<////)/x. of Sowerby, which to the unassisted eye

seems ti) l>c oiil\ marked with concentric lines. It is likewise even possible, we
tliink, that tliis genus may he found to include some ( 'retaceoiis species with straight,
rijjid, radiating costa', such as /'. «/.i///. /,/,./ and /'. r<il<>iii<ii/rn9i*, D'Orbigny, for on
both of these shells, which are ornamented with straight, radiating costa'. \\e observe
an entirely distinct s\stem of curved, radiating, or divaricating stria;, which on the
lateral margins cross the costs: ol>li(|iiely ; \\liile tliese shells have the form and deep
h\-^al sinus of the typical ( 'niii/>/<>,,,</, *. Still, they may present some differences
in the nature of the hinge or interior that, along with their surface markings,
would place them in ii distinct genus.

The topical species of this genus will be at once known from all the other groups

of I'n-i'u, i,/,i. by their peculiar ornamentation alone. That these and various other

fossil and recent types usually referred to the genus .fteten, should be placed in

different genera from that group, as t\ pitied by the recent P. Jacobins, P. maximum,

is maintained by Prof. Agassi/, cannot be reasonably doubted.

This genus was introduced during the Jurassic epoch, and ranges through several
members of the Cretaceous system, the deposition of which it seems not to have
survived.

t'amptoncctes belliatriatiis.

Peelen bellittriatut, MKKK, Proceed. Acad. Nat. Sci. 1'hila. July, 1860, 311.
Cami>ionrcta bellutriatui, MEEK, Smithsonian Cat. N. Am. Jurassic Fossils, 1864.

Shell very thin, compressed-lenticular, snborbicnlar ; valves nearly equally convex ; binge line equalling two-fifths
to one-half the transverse diameter of the valves ; posterior ear very short or nearly obsolete, flat, and obliquely
truncated ; anterior ear larger, flattened, and marked by rather distinct lines of growth — in the right valve separated
from the adjacent margin by a more or less angular sinus one-third to one-half as deep as the length of the ear,
measuring from the beak. Surface strin very fine, regular, sharply impressed, and increasing In number by the
intercalation of others between as they diverge in extending from the umboual region — so strongly arched as to run
out on the hinge lino near the beaks ; concentric stria* fine, regular, closely arranged, and often nearly orquite obsolete
on the flattened spawn between the impressed radiating strisj, to which latter they impart a sub-punctate appearance.

Length of a large shell, 2.65 inches ; breadth from hinge to ventral margin, 2.26 inches ; convexity, 0.64 inch.

A DC

Camptoneete* bellistriatu*.

A. OuUide view of a small lefl valve. D. Enlargement of surface stri» of MUM. B. Inside view of a Urge right
valve [the appearance of radiating markings within is an error in the engraving]. C. Outline of right and left
valves united.

78 PALAEONTOLOGY OF THE UPPER MISSOURI.

This species seems to be nearly related to Pecten lens, of Sowerby ; but as no good
figures or descriptions of the right valve of that species, from the original locality,
have yet been published, and several distinct species have probably been confounded
under that name, we are somewhat at a loss how to point out the distinctive charac-
ters of our shell. Sowerby's figures and description, especially, give us no very
satisfactory characters for identification or comparison, and that given by Morris &
Lycett (Monogr. Grt. Oolite, tab. ii, fig. 1) is also apparently of a left valve only,
though from a better specimen than those figured by Sowerby. Compared with
this, our shell is proportionally broader, and has a shorter hinge line, as well as
shorter ears. From the species figured by Goldfuss, under Sowerby's name (Petref.
Germ, ii, tab. xci, fig. 3), ii will be readily distinguished, by its smaller posterior
ear, and much deeper byssal sinus ; this latter character will also distinguish it from
the forms figured as Pecten lens, by Bronn (Leth. tab. xix, fig. 7).

The species figured by D'Orbigny (Geol. Russ. II, tab. xlii, 1) as P. lens, re-
sembles that before us very nearly in form, the depth of its byssal sinus, and most
of its other characters, but our species may be at once distinguished by its shorter
obliquely truncated posterior ear. As near as can be determined from D'Orbigny's
figures, the form described by him seems to be more coarsely striated.

Locality and position. — Red Buttes, and below there on the north branch of
Platte River, Dakota Territory. Jurassic. (Type No. 680, Smithsonian Museum.)

Camptoiiectes ? extenuatus.

(PLATE iii, Fig. 6.)
Pecten extenuatus, MEEK & HAYDES, Proceed. Acad. Nat. Sci. Phila. May, 1860, p. 184.

Shell small, broad-ovate, or snbcircular, compressed, lenticular ; ventral margin regularly rounded ; hinge line
short (ears unknown). Surface of casts apparently only marked with concentric strise.

Antero-posterior diameter, 0.90 inch ; breadth from hinge to ventral margin, 0.98 inch ; convexity, about 0.28 inch.

This species is rather abundant, but all the specimens we have seen are casts,
which do not show the form of the ears very clearly. In one specimen, however,
in removing some of the matrix from the hinge, we thought we saw traces of a
deep sinus under the anterior ear of the right valve. If so, the form and general
appearance of the shell would be that of Camptonectes, unless there may be differ-
ences in the surface markings. As stated above, the casts we have seen only show
faint traces of concentric stria? ; but as they are in sandstone, it is possible there
may have also been fine curved radiating stria?, if not as in the typical species, at
least faintly indicated as in Pecten cottaldinus, D'Orbigny.

The uniformly smaller size of this shell will alone distinguish it from the last,
even if it should be found to agree in its surface sculpturing.

Locality and position. — North Platte below Red Buttes, Dakota; and southwest
base of Black Hills, Dakota Territory. Jurassic. (No. 680, Museum Smithsonian
Institution.)

KKPTILIAN AOE. J UR A SSIC PE R I O D. 79

FAMILY PTERIHLE. (Sec page 27.)

SUBFAM 1 1. v I 'TKI ! 1 1 \jf}. (Sec page 28.)

(IKS-US FIERI A, ScoroLi.

*.— /Vn,., S<-oroi.i, Introd. Hist. Nat. 1777 — GRAY, Zool. Proceed. 1847, 199.— Htm, Am. Jour. Scl. and ArU [2],

XXXVII, l->;4, -J17.
Avicul.t (Ki.ni.t), BBPO (part), Hncyc. M6th. 1792, pi. 177. — CCTIIB (part), Tab. Elem. 1798; Anat. Comp.

1800 ; Regne An. 1817 — LAMK. I'rodr. 1799 ; Syst. An. 1X01, 134 ; Phil. Zool. 1809, 318, &c.
Uaryaritiftra (sp.), Hmni. Has. Col. 1797, 44.
Pi*rt:,<i,,, I.ISCK, Beschr. Rost. 1807 (not BOLTBH, 1798).
U*innium, LtHK, ib.

Anonica, OKKX, Handb. d. Zool. 1815 ; Natgsch. f. Schulen. 1815, 652.
Ptrlamaler (sp.), BCIIDM. En. 1817, 107.
Klym. — irri(«t, a wing.
/.'j-'ini/i. — Mytilut Airuni/o, LIXH.

Shell obliquely subovatc, or sub trigonal, fragile ; surface smooth, striated, costated
or subspinous — often with imbricating marks of growth ; inequality of valves gene-
rally distinctly marked ; byssal sinus in the anterior margin of the right valve well
defined. Cardinal margin long, straight, and produced into more or less distinct
winjjs at the extremities — the posterior wing being larger than the other. Hinge
\\itb usually one or two small cardinal teeth under the beak of each valve.
The (simple) pallial line represented by a row of minute irregular scars, extending
from the subcentral impression of the adductor muscle obliquely forward to the
small anterior muscular scar beneath the beaks.

Amongst the numerous fossil species referred by various authors to this genus,
there are, in addition to the several types we believe to belong to clearly distinct
genera, others which differ sufficiently from the living typical species to constitute
at least well marked sections. It is not our purpose, nor have we the necessary
material at band, to attempt to define here all of these various subordinate groups,
though it becdmes necessary to notice one of those including a species with which we
have to deal. The section to which we allude may be designated as follows : —

Oxytomii, MERK.

Shell differing from the typical forms of Ptrrin (= Avicula), In being less oblique, proportionally shorter, more
distinctly inequivalve, and usually more strongly costate — particularly on the left valve, around the pallial
margins of which the cosUe are sometimes produced in tbe form of free spines. The byssal sinus of the
right valve is also much deeper aud more sharply defined than in the typical species of Pttria.

Type Ai-icula Jfuntteri, GOLDF. Petref. Germ. II, pi. czzviii, 2 a, to A.1 Also Includes A. cottata, MOBKIS &
LTCKTT, A. tliyilalu, and apparently Manoiit interUmigata, QPIXSTEDT, and A. cygnipa, PHILLIPS.

This section forms a transition from the typical Avicula to the genus Eumicrotii, and seems to be mainly, If not
entirely, confined to the Jurassic rooks.

The genus Pferia, or Avwula^ is so nearly related to the older extinct genus
Pterinia, that the two groups are generally confounded, where the hinge and in-

1 Several species appear to have been confounded under the name A. Munsteri, by other authors.
We regard the particular form figured by Goldfuss as the type of the section Oxytoma.

80

PALAEONTOLOGY OF THE UPPER MISSOURI.

terior cannot be seen. They can be readily distinguished, however, when we have
an opportunity to examine the hinge, which in Pterinia differs from that of Pteria,
in the possession of a more or less broad cardinal facet, marked with linear cartilage
furrows, but without a cartilage pit ; as well as in having oblique posterior and
anterior teeth not found in the true Pterias. From Meleagrina and Mallceus, which
some authors include in this genus, the Pterias can be readily distinguished by
obvious differences of form.

It will be very difficult to determine at what particular period this genus, as
properly restricted, was first introduced, until the nature of the hinge of many
extinct species can be determined. Palaeontologists, who are often too much in-
clined to lose sight entirely of the existing types upon which so many genera of
Mollusks were originally founded, refer to it many species from the Palaeozoic
rocks ; but many of these older species are known to be true Pterinias ; and it is
more than probable, as already stated in the remarks on this family, that the
Silurian, Devonian, and many, if not all, of the Carboniferous and Permian species
referred to Avicula, will be found to belong to Pterinia, Bakevellia, &c., or to
undescribed genera. Our present impression is, that typical species of Pteria did
not exist previous to the Cretaceous epoch, and that probably none of the forms from
rocks older than the Jurassic, or possibly from the Trias, can be properly included,
even as distinct subgenera. The genus is represented in the Cretaceous and Tertiary
deposits, but seems not to have been more extensively developed at any past time
than at present in our existing seas. The living species are found on the coast of
South America, of the British Islands, and in the Mediterranean and Red Seas,
the Indian Ocean, &c.

Subgenus OXYTOMA.
Pteria Munsteri.

Avicula Munsteri, BRONN, Leoh. Zeitsoh. 1829, 76.

Avicula Munsteri, GOLDF. Petref. Germ. II, 131, cxviii, a, b, c, d, e,f, g, h.

Monotis Munsteri, QUEXSTEDT, Wurtt. 341 ; IB. Der Jura, II, 1856, 440, Ix, 6.

Shell obliquely oval ; hinge line less than the greatest parallel diameter of the valves, and ranging at an angle
D A of 55° to 60° above the oblique longer axis of the shell ; anterior margin slop-

ing with a graceful backward curve into the rather narrowly rounded postero-
basal extremity ; posterior margin ascending forward nearly parallel with the
anterior outline to the wing, where it curves rather abruptly backward so as to
form a distinct rounded sinus. Left valve rather gibbous ; beak convex, and
projecting slightly beyond the hinge margin ; posterior ear flattened, snbtrigonal,
and terminating behind in a mucronate angle, but not extending so far back
as the postero-basal margin ; anterior ear small, rather convex — form unknown.
Surface (left valve) ornamented by about ten to fifteen moderately distinct
. . slender radiating costae, separated by spaces four to six times their own breadth.

At the middle of each of these spaces there is usually a smaller rib, which
A. Out le vie dieg Qut before reaohing the nmbo . and between each of thege and the prin.

cipal ribs, still smaller radiating strise are seen — the whole being crossed by
a few small marks of growth, and (probably on well preserved specimens) concentric strise.

Diameter at right angles to the hinge, about 0.93 inch ; do. parallel to the same, about 1 inch ; convexity of left
valve, near 0.24 inch.

We have referred this shell (provisionally) to Avicula Munsteri, of Bronn, rather
because the imperfect specimens we have yet seen do not exhibit any reliable

i: KPTILIAN AGE. .ir I: A SSIC PERIOD. 81

character^ by which it can he distinguished, than from being satisfied that it is
really identical. The tew specimens in the collection consist of imperfect left valves,
none of which gi\e any idea of the form of the anterior wing ; while their liner
surtace markings are nearly obliterated by exfoliation and weathering. It is more
than probable that perfect specimens showing the nature of the surface markings
of both \alves will be found to present characters by which this shell may be dis-
tingnished from .\<-;<-nl« Mmixf,,-i ; if so, it may take the name Pteria mucroiiata,
or Aririi/u linn i-i'iKilii, if the latter generic name is retained.

I.<»-nIir>/ n/nl jH^iridii. — Wind Itivcr Valley, Dakota Territory. Jurassic. (Type

Genus EUMICROTIS, MKKK. (Page o:j.)

I IIIIIM roli- Clirtn.

(PLATE iil, Fig. 10, a, I:, C, rf.)

Avieula curia, HAIL, 1852, Capt. Sunsbnry's Kept. Grt. Salt Lake Ezp. 412, pi. 2, fig. 1, a, b.
.InVu/fi (JJomalit) tmuicottata, MEEK & HAYDHX, Proceed. Aead. Nat. Bel. Pliila. March, 1868, 60.
.M-<mtit curia, MKKK & HATDES, Proceed. Aoad. Nat. Sci. Phila. Oct. 1860, 418.
Kumicrotis curia, MEEK, Smithsonian Check LUt N. Am. Jurassic Invert. Fossils, 1864.

Bhvll saborbicular, very slightly oblique, usually a little higher than long, moderately convex, and nearly eqnl-
valve ; anterior side more or lr*s rounded ; ventral and postero-vi-ntr.il margins rounded. Posterior border ascend-
ing obliquely forward, and sometimes slightly concave in outline above. Hinge margin straight, and considerably
shorter than the length of the shell, compressed behind, so as to form a very short, more or less angular wing,
which is sometimes nearly obsolete ; rounding or very obtusely angular In front of the beaks, but not terminating in
a wing. Beak of left valve small, and rising a little above the hinge ; that of the other valve more compressed,
and scarcely distinct from the cardinal margin — both located slightly in advance of the middle. Bysnal sinus
small, rather deep, angular, and connected with a narrow external groove extending nearly parallel with the hinge
margin to the beak. Surface of left valve ornamented by radiating lines ; that of the right valve generally only
marked with concentric strin.

Length, 0.60 Inch ; height, 0.64 Inch ; breadth or convexity, 0.26 inch.

The radiating lines of the left valve are regular, and usually rather smaller than
the depression between ; they seem to be always simple, though many of them die
out before reaching the beaks. On the right, or smaller valve, they are always
very obscure, and often obsolete, while the concentric stria*, in most cases, are
moderately distinct. In adult shells, the hinge line is often proportionally shorter
than in smaller individuals.

This species varies in form, some of the specimens being longer, and some shorter
than wide. Those figured by Prof. Hall are in a bad state of preservation, and
give an imperfect idea of the characters of the species; though we are satisfied,
from direct comparison with other specimens obtained at the same locality, as well
as with those collected by Capt. Stansbury, that our shell belongs to this species.

In form, surface markings, and indeed in almost all its characters, this shell
agrees so very closely with Moiiotis sulmtriata, Munstcr, that we are strongly in-
clined to the opinion that it will, on comparison, prove to be identical. It is gene-
rally a little less oblique than the figures of that shell given by Goldfuss, Quenstcdt,
and others, but varies in this respect. Were it not that some authors describe M.
Kiilistrinta as being plano-convex, while the two valves of our shell are nearly
equally convex ; and that none of the descriptions we have read mention any differ-
ence in the distinctness of the radiating stria? on the two valves, we would scarcely
hesitate to refer the specimens now before us to M. mlbttriafa.

Locality und ponltion. — Southwest base Black Hills. Jurassic. (Type No. 205.)

11 September, 18O4.

82 PALAEONTOLOGY OF THE UPPER MISSOURI.

FAMILY TRIGONIID^E. (See page 57.)
Genus TEIGONIA, BRUGUIERE.

Synon.— Trigonia, BEDO. Encyc. Meth. I, 1789, xiv, pi. 237.— LAMK. Prodr. 1799, 86; ID. Syst. An. 1801, 116, and
An. du Mus. IV, 1804, p. 351.— ROISSY, Mol. VI, 1805, 392, &o.

Lyrodon, G. B. SOWEBBY, Genera Shells, 1833, fasc. 41.

Lirodon, BBONN, Leth. 1837 (sec. ed.) 367 and 700.

Lyriodon (part), GOLDF. Petref. Germ. II, 1837, 196.— BBONN, Jahrb. 1838, p. 108.
Etym. — TjiV>»»(, three cornered.
Type. — Trigonia scabra, LAMK.

Shell subtrigonal, longitudinally ovate, elongate, or subcircular ; postero-dorsal
region often provided with a more or less distinctly denned escutcheon or corselet.
Surface ornamented with radiating, oblique, or concentric costae or rows of nodes;
rarely smooth. Beaks usually elevated. Ligament short and prominent. Hinge
thick, composed of two large diverging, elongate, transversely furrowed teeth, in
the right valve, and three or four in the left, furrowed only on one side. Im-
pressions of adductor muscles usually well defined, the anterior being located near
the beaks. Scar of posterior pedal muscle located a little above, and in front
of, the impression of the posterior adductor; antero-pedal scar generally placed
within the cavity of the beaks, sometimes wanting in the right valve.

Many of the extinct species generally referred to this genus differ so widely in
form and surface ornamentation from each other, as well as from the living Trigonias,
as to leave room for doubts whether or not they really all belong to one and the same
genus. These differences attracted the attention of Prof. Agassiz, who separated
the several types into distinct sections, which he accurately describes in his excellent
monograph of the genus. These sections may be briefly characterized as follows : —

1. -•!.«•> Scaphoides," AGASSIZ.

Shell subtrigonal, longer than high ; anterior side short and truncated ; posterior side long and very abruptly
rounded or snbangular at the extremity. Dorsal corselet large and nearly smooth, excepting the lines of
growth ; not defined by a ridge or sulcus on either side. Surface ornamented with varices in front, and
more or less nodose, transverse or oblique costse on the flanks.

Type. — Trigonia navis, LAMK. (Jurassic and Cretaceous.)

3. "Les Clavellees," AGASSIZ.

Shell more rounded in front than in the last group ; corselet well developed and often bounded by a ridge on
either side, sometimes with strong marks of growth. Surface ornamented with more or less nodose costas,
which pass from the margins of the corselet obliquely downwards and forwards, often becoming broken up
into a series of isolated tubercles on the sides and front of the valves.
Example. — T. clavellala, SOWEKBY. (Mainly Jurassic.)

3. "I. cs Carrees," AGASSIZ.

Shell shorter and more truncated at each extremity than the last ; also with less regular costae on the flanks,

and a larger and more compressed corselet. Marks of growth often distinct on the corselet.
Example. — T. quadrata, A.O. (Upper Jurassic and Cretaceous.)

4. "L.es Scabrcs," AOASSIZ.

Shell rounded and gibbous in front, elongate, narrowed and subrostrate behind. Corselet separated from the
flanks by a more or less distinct groove ; ornamented with transverse costs. Flanks and front with tuber-
culose, or subspinous costae, which pass from the margins of the corselet to the base and front, those on
the anterior part of the valves curving forward.

Example. — T. aliformis, SOWKKBY. (Mainly Cretaceous.)

UKI'TILIAN AGK J U II A SSIC PER IO D. ;

.V " I.OH OiiduleoH," AGASSIS.

Shell liitermedinto in tU ornamentation between the last and the next following group* ; conelet much as In
" Scuphoidet ;" sides and front with longitudinal, generally smooth ooeUe, abruptly curved upwards
behind.
/.'rum/./.. — /'. uHtlulala, Putin >i. (Juraaic and Crttactout.)

«;. " !.€••. < l»»tlTs," AOAMII.

Shell ornamented on the flanks and front with prominent, generally smooth longitudinal cosUe, with scarcely
If marks of growth between. Corselet very distinct, and separated from the flanks by a well defined

ridge, formed usually of flattened imbricating prominences; ornamented with numerous small tubercles,

or tnbercnlate costs, and two radiating crennlated ridges.
Type. — T. eoilala, LAHK. (Jurauic and Crttaceoiu.)

T. " l.€-s Liageea," AOASSIZ.

Shell depressed, elongate, and rounded at both extremities, smooth, or rarely with obscure traces of concentric

costn In front ; lines of growth not strongly marked.
Example. — T. longa, Ao. (Jurauic and Cretaceous.)

H. u I-es Pectinacees," AOASSIX.

Shell short, oval snbtrigonal ; without a distinct conelet ; surface ornamented with concentric radiating cost*.
Type. — T. peelinala, LAHK. (Existing teat.)

Those groups, it will be observed, arc founded upon differences of form and orna-
mental i<m analogous to those presented in the Unionida>, whore they appear to be
coincident with differences of structure in the animal, considered by Prof. Agassiz
of generic value. It does not, however, necessarily follow from this, even if we
admit all the proposed genera of l'ni>niiil(v, that the sections of Trigonia under
consideration must be viewed as distinct genera ; since the differences of form and
structure obsen rd in tin • various groups, and subordinate divisions of the animal king-
dom, an- M> infinite and varied, that we cannot always apply precisely the same rules
for the distinction of genera in one family, that serve to distinguish those of another.

The genus Trigonia is closely related to Myoplioria, of Bronn, by which it seems
to have been represented, during the Triassic epoch, as the latter was represented
during the deposition of the Permian and older rocks, by the genus Sr/t!z<xlu*, of
King. For remarks on the relations of these three groups, see pages 57 and 58.

If we exclude Myoplioria from the genus Trigonia, it will probably be found to
range back no farther than about the commencement of the Jurassic epoch, towards
the middle of which it seems to have nearly or quite attained its maximum de-
velopment.1 It was also well represented during the deposition of the Cretaceous
rocks, but appears to have become almost extinct at the close of that epoch, since
only a few doubtful instances of its occurrence in Tertiary deposits have been re-
corded. Some five or six species, however, are known to be still living in the
Australian seas.

Triffonia Conradi.

(PLATE ill, Fig. 11.)

Trigonia Conradi, MRKK & HATDKK, Proceed. Acad. Nat. Sci. Phila. Hay, 1860, 183.
Triyonia Conradi, MEEK & HATDKX, " " " « " Oct. 1860, 418.

Shell rather small, short, snbtrigonal, moderately compressed ; anterior side truncate ; base ronnded ; posterior
side sloping obliquely from the beaks above, and apparently vertically truncate at the immediate extremity. Beak*
elevated, narrow, Incurved, and located in advance of the middle; posterior umbonal slopes rather distinctly

1 A few of the Saint Cassian (Triassic ?) species may possibly belong to some section of the genus
Trigonia.

84 PALAEONTOLOGY OF THE U P P E II MISSOURI.

angular. Surface ornamented by small, simple, obscure concentric eostre, which on the posterior side of the valves
descend at first perpendicularly, after which they are deflected forward parallel to the basal and anterior borders.
Length and height, each about 0.97 inch ; convexity, 0.58 inch.

The specimens of this species we have seen, are not in a condition to have re-
tained fine surface markings if there were any ; nor do they show very satisfactorily
the character of the corselet, though it seems to have been marked by obscure
radiating costse, and is bounded on each side by the distinctly angular umbonal
slopes. The specific name was given in honor of Mr. T. A. Conrad, the well-known
Palaeontologist of Philadelphia.

Locality and position. — Southwest base of the Black Hills ; in the lower Jurassic
beds of that region. (Type No. 212.)

FAMILY MYTILID^E.

Shell inequivalve, inequilateral, closed, elongate, oval or oblong;
covered with a thick dark epidermis ; interior more or less pearly ; liga-
ment internal or submarginal, very long; hinge nearly or quite edentu-
lous, or sometimes crenate. Posterior muscular impression large, and
faintly marked ; anterior generally small. Pallial line simple.

Animal with mantle margins free, or united behind so as to form a
more or less complete anal tube ; labial palpi elongated, pointed, and
free ; gills two on each side, elongated, nearly equal, united to each other
behind, and to the mantle. Foot cylindrical, grooved, and byssiferous.

This group includes the following genera, viz.: Mytilus, Volsella, Pachymya,
'Litliopliagus, Myrina, Adula, Crenella, Hippagus,1 and Stalaffmium?

Messrs. H. and A. Adams divide it into the following subfamilies, viz. : —

1. Mytilinse. Hinder part of mantle but slightly produced ; anterior muscular scar generally small.

Including Mytilus, and Myrina.

2. Crenellinse. Hinder part of mantle produced so as to form false siphons.

Includes Crenella, Volsella, and Adula.

3. Lithophaginse, Hinder part of mantle more or less produced ; anterior adductor muscle moderate.

Includes Lithophayus.

The fossil genera Pacliymya, Modiolopsis, and a part of species referred to Ortlto-
nola, seem to belong to this family ; but as we know them only as extinct species,
it is scarcely possible to determine to what particular section of the group they
most properly belong.

' Chenu (in Man. de Conch. II, p. 169) places Hippagus, Lea, in the family Trirjoniidee, and
figures Wood's sp. verticodius, as a cretaceous example of that genus. This, however, is far from
correct, that species being the type of the genus Veriicordia and a Miocene shell ; while Hippagus
isocardoides, Lea, a widely distinct form, from the Eocene, is the type of Hippagus, and belongs, as
we think, to the Mylilidse, very near the genus Crenella, if it is indeed even generically distinct.

9 If Nucunella, and Nuculocardia, D'Orbigny, are distinct from Stalagmium, they should appa-
rently be placed at least near that group in the Mytilidse. Chenu, in the work above cited (p. 181),
places Nucunella in the Arcidse, and figures its type, N. Nystii, both there and on p. 153, under
Crenella, in the Mytilidse.

i: KI'TILIAN AGE. J U R A 8SIC PE RIOD. 85

Genus VO I. si. 1. 1. A, Srorou.1

Sy*o».— \roltrlla, Scorou, Intr. Hist. Nat. 1777, 397.— MODED, K. Vet. Ao. Uaiidl. 1793, 392.— GRAJ, Proceed. Zool.

800. 1.1.11,1. 1-47. r.'T.

Tamariiulifi-rmii, MlDMB. (part), Mas. OIRVKS, 1787, 412.
Callitlricht and Call-in, -h.-lmna (gp.), POLI, Utr. Slo. I, 1791, 194.

JUodiolu*, LAMK. Prodr. 17!)i), h7.— CI-VIEB, An»t. Comp. 1800; Begne An. II, 1817, 471 ; »nd ib. Ill, 1830,
r.\'\.— I.I.VK, Rest. Samml. Ill, 1807, 146.— OOLDF. Zool. 1820, 611.— RIMO, Hist. IV, 1820, 323.— FORBM,
Mai. Mou. 1838, 43, &o.

V.,/,i, LAMK. Syst. An. 1801, 113; ID. An. dn Una. VI, 1805, 119; «nd Ilist. VI, 1819, 109 Fuou.

Tab. Sjrat. 1821, p. xlli.— BLAIBV. ("ModioU"), Diet. Bci. Nat. XXXII, 1824, 318.— BBOVK, Leth. 1837,
355, &c. Ac.

Amyydatum, MriiLF. Entw. 1811, 69.

Mytiltu (ep.), SOIICM. Ensai, 1817, 106, and various others.
llrachyalontt*, 8w AltiKOK, Malacol. 1840, 384.
Klym. — Vnliella, a kind of forceps or tweezers.
Type. — Mytilus modiolia, Lix.i.

Shell transversely oblong; surface smooth, concentrically striate, or with radiat-
ing or divaricating stria; or costse ; epidermis often produced into long filaments.
Beaks depressed, and placed near the anterior extremity. Hinge sometimes a
little callous and crenated, but without proper teeth; ligament linear, occupying a
marginal groove. Muscular impressions very unequal ; pallial line faintly marked.

Animal with mantle margins open, plain, protruding in the branchial region ;
anal tubes short, more or less complete ; palpi triangular ; byssus fine and strong.

This genus, as here defined, embraces two sections or subgenera: 1. The typical
species, with a smooth or striate surface, and a non-crenatcd hinge ; 2. Species with
radiating or divaricating costce or stria*, and a crenated hinge-margin (Brac/iydotites,
Swains.). Adula, of H. & A. Adams, is also sometimes included as a third section,
but it seems to be sufficiently distinct to rank as a separate genus.

The genus Voleelia, or Modiolus, is nearly related to Mytilus, but differs in having
the beaks obtuse and placed more or less back from the anterior end, instead of
being pointed and quite terminal. The antero-basal region of these shells is also
always more prominent than in the Mytili. There are likewise some differences in
tin' habits of these two genera.

Species have been referred to this genus from the Silurian rocks, but they doubt-
less all belong to Modiolopsis, OrtJionota, and other extinct genera.

Several species presenting the external appearance? of VolseUa have also been
described from the Devonian and Carboniferous rocks, but we yet want a more
accurate knowledge of their hinge and interior, before we can be quite sure they
are true Volscllas. The genus seems to be represented in the Triassic rocks, and its
existence during the deposition of the Jurassic system of strata is well known. It

* Scopoli's first species of Volsella was Mytilus modiolus, Lin., the type of the subsequently
proposed genus Modiolus, or Modiola, of Lamk. ; while the others belong to the older genus Mytihi*
proper, of Lin. As Scopoli was a strictly binomial anthor, however, the law of priority compels us
to adopt his name for the previously unnamed group, of which Mytilus modiolutt, Lin., is the type.
For a TV;/"/'""'.'/ proposed name cannot be wholly ignored, because the author happened to include
some species belonging to an older genus.

86 PALAEONTOLOGY OF THE UPPER MISSOURI.

also occurs in the Cretaceous and Tertiary deposits, and is abundantly represented
in our existing seas, where it probably attains its maximum development. The
recent species are chiefly found in southern latitudes, though a few occur on the
coast of Great Britain, and in the Mediterranean and Arctic seas ; also on the east-
ern coast of the United States, &c.

Volsella pertenuis.

(PLATE III, Fig. 5, 5a.)
Mytilus pertenuis, MEEK & HATDKN, Proceed. Acad. Nat. Sci. Phila. March, 1858, 51.

Conip. Modiola minuta, QOENSTEDT, Der Jura, tab. i, fig. 36..
Volsella pertenuis, MEEK, Smithsonian Check List N. Am. Jurass. Foss. 1864, 28.

Shell small, very thin and fragile, narrow oblong-oval, slightly arcuate ; valves convex along the middle, from
near the beaks obliquely backward, in the direction of the lower part of the posterior end. Extremities narrowly
rounded, the anal end being a little broader than the other ; base slightly arched behind the middle. Hinge nearly
straight, and apparently rather less than half the length of the shell ; dorsal margin forming a broad descending
curve from the back extremity of the hinge posteriorly. Beaks small, subangular, and located at the anterior end,
scarcely projecting beyond the margin. Surface marked by flue, rather obscure, lines of growth.

Length, 0.73 inch ; breadth, 0.26 inch ; height, 0.30 inch.

This shell is so very similar to a Jurassic species figured by Quenstedt (Der Jura,
tab. i, fig. 36), under the name of Modiola minuta, that, after further comparisons,
we are at a loss to point out any characters by which it can be distinguished. As
there seems, however, to be some reason to doubt the identity of the shell figured
by Quenstedt with M. minuta of other authors, we have concluded to retain our
name, pertenuis, until authentic specimens of these shells can be compared.

The species now under consideration is also similar in form to young specimens
of Mytilus Meekii, Evans & Shumard (Trans. St. Louis Acad. Sci. vol. i, p. 40), but
is shorter in proportion to its height. The fact, too, that M. Meekii is an upper
Cretaceous species, while that now before us occurs in rocks holding a rather low
position in the Jurassic system, is conclusive evidence, we think, that they must
differ specifically.

If Adanson's ante-Linnaean genera are to be adopted, with his first species of each
as its type, the name of our shell would have to be written Perna pertenuis, as it
belongs to the same group as the type of Perna, of that author (not of Brug., Oken,
or Cuv.). If, on the contrary, neither Perna, Adanson, nor Volsella, Scopoli, should
be retained, we must adopt Modiohis, Lamarck, and call it Modiolus pertenuis.

Locality and position. — Southwest base of the Black Hills, in the lower Jurassic
of that region. (Type 215.)

Volsella fbrmosa.

Modiola (Perna) formosa, MEEK & HAYDEX, Proceed. Acad. Nat. Sci. Phila. Dec. 1861, 439.
Volsella formosa, MEEK, Smithsonian Check List N. Am. Jurass. Fossils, 1864, 28.

Shell elongate-subelliptical, a little arcuate, gibbous along the oblique umbonal slopes, from the beaks to the
postero-basal extremity ; greatest convexity near the middle of the valves. Ventral margin somewhat sinuous
near the middle, or a little behind it, and rounding up rather abruptly at the extremities; dorsal outline broadly
arcuate, declining from the middle posteriorly ; both extremities rather narrowly rounded. Beaks small, some-
what compressed, obtuse, and located directly over the anterior margin, beyond the outline of which they scarcely
project. Surface ornamented with small concentric striae, and a few stronger marks of growth, which are crossed
on the dorsal and postero-dorsal regions, by regular, closely arranged, and generally simple radiating lines. Faint
traces of another system of extremely fine striae may be also sometimes seen by the aid of a magnifier, crossing
the somewhat compressed ventral region of the valves, from the oblique umbonal ridge, nearly at right angles to
basal margin.

K I- I'TILIAN AGE. J UR A8SIC PE RIOD. 87

li, 2.05 inches ; diameter from the dorsal margins, at right angle* to the length, near the middle of the
shell, 0.34 inch ; greatest convexity at the same point, 0.80 Inch.

VoUtlla format*.
A. Dorsal view. B. Side view.

This species belongs to the irregularly proposed genus Perna, Adanson, = Modio-
/».-. Lamarck, and will fall into Swainson's section Brachyoftontes. It seems to be
\cr\ do.xeK related to the European Volsclta cancellata (= Mytilus cancellatits, Gold-
I'n*-. 1'etret". (ierm. tome ii, pi. 131, fig. 2), and may possibly prove to be identical,
when we can have an opportunity to compare a good series of each. The five or six
specimens, however, of the form here described, that we have seen, all present the
following differences from Goldfuss' figure : In the first place they are narrower from
the dorsal to the ventral margins, more narrowly rounded at the posterior extremity,
and have slightly more prominent beaks ; while their antero-ventral region is a little
more convex, and their basal outline more arcuate. The surface markings of the
species under consideration are very similar to those of Goldfuss' species, though
his enlarged figure represents the concentric strite crossing the radiating lines as
being more distinct and regular than on our shell. Again, he neither figures, nor
mentions in his description, the fine obscure transverse striae seen on the ventral
half of our species, though these are so indistinct that they might be easily over-
looked ; indeed they seem to be rather dependent, in some way, upon the structure
of the shell, than properly surface markings.

"We observe D'Orbigny cites Modiola camrllufn, of Roemcr, and his own M.
AV /•<//•>/./•///<», from the Jura of Russia, as synonymous with Mi/tilns cancellatw,
Goldfuss. Without knowing to what extent Goldfuss' species may vary, we cannot
leel prepared to express a positive opinion in regard to its relations to the forms
named by Rocmer and D'Orbigny; though judging by their figures, we would be
inclined to doubt the identity of these shells. At any rate, Roemer's and D'Orbigny's
figures are very unlike the form now. before us, which is remarkably uniform in its
characters.

Locality and jxwition. — From the Jurassic beds of Big Horn Mountains, Dakota
Territory. (Type 1882.)

FAMILY AKCID^E.

Shell eqni valve- or -eubequi valve, not pearly within, closed or gaping
below, usually gibbous; surface frequently ornamented with radiating
costee or strite. Hinge straight or arched ; provided with a more or less
elongated posterior and anterior lateral tooth, which are divided trans-
M-rsely, obliquely, or longitudinally, into small interlocking, short, or

88 PALAEONTOLOGY OF THE UPPER MISSOURI.

linear plates. Ligament external, attached to a more or less developed
cardinal area ; cartilage occupying a series of small marginal pits (usu-
ally leaving linear grooves in the area as the shell advances in its growth),
or very rarely collected within a single larger central cavity. Muscular
impressions two ; pallial line simple.

Animal without siphons or true palpi ; mantle margins open, simple
or fringed, often provided with ocelli ; labia formed of the extremities
of the branchiae ; gills oblique or pendent, separated behind, or united
to a membranaceous septum ; foot large, bent, generally grooved, and
with plain or crimped margins.

As was first observed by Dr. Gray, the hinge in this and some allied families,
although in most cases apparently provided with a numerous series of small
teeth, has really but a posterior and an anterior tooth, which are divided verti-
cally, obliquely, or horizontally into small, more or less numerous interlocking
plates. These divisions, Dr. Gray thinks, are analogous to the transverse ridges
produced by the striae or furrows in the teeth of Trigonia. In the typical Arks
(that is, viewing A. Noce as the type), and some of the other genera, the divisions
of the teeth cut the hinge margin nearly or quite at right angles, but they are
found to become more and more oblique, as we pass from group to group, until in
Cucullcea, Macrodon, &c., they range, particularly behind the beaks, parallel to the
cardinal margin.

The family Arcidce, including the various fossil and recent genera, seems to
embrace three, and possibly four, more or less marked subfamilies, distinguished
mainly by the arrangement of the cardinal plates, and partly by the general form
and obliquity of the shell, &c. These subfamilies may be arranged and character-
ized as follows : —

t. Arcinae.

Shell more or less oblong, or subrhombic ; nmbonal axis oblique, hinge margin straight or more or less

arched ; cardinal plates crossing the hinge margin at various angles, or rarely dividing it horizontally

near each extremity.
Includes Area, Barbatia, Striarca, Anadara, Senilia, Lunarca, Argina, Noetia, Litharca, ParaUelepipedttm,

Scaphula, Cucullxa, and probably Isoarca f and several undefined fossil genera. (Paleozoic 1 to modern seas. )
3. Macrodontinae.

Form, hinge line, and umbonal axis, generally much as in the Arcinse. Anterior hinge plates crossing the

cardinal margin obliquely forward and upward ; posterior plates ranging parallel to the hinge line, often

long and linear ; mesial plates obsolete.
Includes Macrodon, Grammatodon, Cypricarditis, and probably Vanuxemia,' Megalomus, Megambonia, Dolabra,

and some undefined genera. (Palaeozoic to Jurassic.)

3. Axininae.

(a.) Shell orbicular, or suborbicular ; cartilage as in Arcinx; umbonal axis nearly vertical ; hinge line regu-
larly arched ; cardinal plates short, and arranged as if radiating from an imaginary point below the hinge.
Includes Axinsea.

(6.) Form and hinge as in subsection (a.). Cartilage occupying a single pit at the middle of the hinge.
Includes Limopsis.

1 If Megalomus, Hall, 1852, Vanuxemia, Billings, 1858, and Megambonia, Hall, 1859, are, as is
thought to be the case, all synonymous, then the rules of priority would compel us to adopt the name
Megalomus for the group. Until the relations of these proposed groups have been more clearly de-
termined, it is probably better to retain them all, provisionally, as distinct genera.

K KI'TILIAN AOE. J U R A S S I C P E R I O D. s;>

"We arc aware these divi.sions arc not equally distinct, the ,l/ifc/-«*/o////Ho; and
in beiiig mure nearly related through Ci/>n//<i,t, S<-<ij,/iii/<i, &c., than either
of these prongs is to the As'in'm-i; Still, we find the Jurassic group Macrodon
shading off so gradually through GrumtiKilixlim, Dolabra, Cypricardites, &c., to
V'tnnst ut'nt, and other 1'ahro/oic groups — some of which depart so widely from tho
recent Arks as to he scarcely recognized as belonging to the same family — that
these forms >, c m to stand together as a distinct subfamily. At a first glance it
might he thought the genus Cm-it//, m should IM- included in the Mw,-<»ln,,tince ;
hut on a closer inspection, it will be observed that in that genus the hinge always
differs from these older groups, in never having the anterior hinge plates ranging
obliquely forward and upwards, and at the same time the posterior ranging parallel
to the hinge line. Again, the posterior hinge plates are never so disproportionally
elongated in Cin-nllira as in the older groups, while it also differs in having small
vertical, mesial plates or denticles between the posterior and anterior divisions. At
the same time that these differences exist between the genus Ciu-nll<m, and all the
allied genera included in the subfamily Macrodon I ind\ Cut-nil, m is found to be con-
nected by such an unbroken scries, through various fossil and recent forms, with
the typical An •!//", that it seems unnatural to separate it and the most nearly allied
genera into a distinct subfamily.

SUBFAMILY MACRODONTIN^E.
Genus GRAMMATODON, MEEK & HAYDEN.

Synon. — Cucullira (sp.), QDKJCOTEDT, Der Jnra, 1856.

Area (Cucullira) gp. MBBK & UAVDBK, Proceed. Acad. Nat. Sol. 1'hila. March, 1658, 51.

Grammatodon, HBRK & HATDBX, ib. Oct. 1858, 419.
F.tyn. — xrw>6, a line ; itin, a tooth, In allusion to the linear teeth.
Type. — Area (Cticullxa) inornate, MEKK & HAYDKX.

Animal unknown. Shell longitudinally oblong, or rhombic oval, nearly or quite
eqni valve, inequilateral; valves rather gibbous, and without crenulated margins;
umbones somewhat depressed, incurved, and not very widely separated. Liga-
ment area rather narrow; hinge straight, provided in each valve with a few
elongated, linear posterior cardinal plates, arranged parallel to the hinge margin ;
and a greater number of shorter, oblique anterior plates in front of the beaks.
Pallia! line obscure; muscular impressions faintly marked, and without a projecting
lamina or ridge. Surface nearly smooth, or with obscure radiating costs or striae.

The species upon which we propose to found this genus agrees almost exactly, in
the character of its hinge, with Macrodon of Lycett ; but is proportionally much
shorter, and differs in having its pallial margin smooth, and closed, instead of crenu-
lated and gaping. Its beaks are also located farther back, while its muscular im-
piv^inns differ in being destitute of any ridge or prominence, such as we see in
Macrodon and Cucullaxt. Possibly it may be only a subgcnus under Mnt-nxldu.

It is but necessary, we think, to compare the hinge of such forms as these with

12 September, 18O4.

90 PALAEONTOLOGY OF THE UPPER MISSOURI.

that of the recent Area Noce, usually regarded as the type of the genus Area, to be
satisfied that they cannot be included in the same group, in accordance with correct
rules of classification.

The group under consideration will probably include several other Jurassic, and
possibly a few Cretaceous species, though we cannot, with any degree of confi-
dence, attempt to define its exact geological range.

•
Grammatodon inornatus.

(PLATE III, Fig. 9, 9o, 96.)

Area (CuctiWara) inornate, MEEK & HAYDEN, Proceed. Acad. Nat. Sci. Phila. March, 1858, 51.

Grammatodon inornatus, MEEK & HAYDEN, Ib. Oct. 1862, 419.

Comp. Cucullxa Munsteri (ZEITEH), QDENSTEDT, Der Jura, tab. 13, fig. 38 ; tab. 18, fig. 34 ; tab. 23, fig. 8.

Shell subrhomboidal, or oblong-oval in outline, rather gibbous in the nmbonal region. Anterior end rounding
up from below, and forming an angle of about ninety degrees with the hinge line above ; posterior side a little
broader than the other, obliquely truncate above, and somewhat narrowly rounded below ; base nearly straight
along the middle, but not exactly parallel to the hinge line, rounding up more gradually in front than behind.
Beaks rising somewhat above the hinge, incurved, and very slightly oblique, located a little in advance of the
middle ; posterior umbonal slopes prominently rounded. Hinge comparatively long, but not quite equalling the
greatest length of the shell ; posterior hinge-plates three or four in each valve ; anterior much shorter, and usually
numbering about six or seven. Ligament area not very broad. Surface apparently smooth.

Length, C.75 inch ; height, 0.45 inch ; breadth, 0.46 inch.

Quenstedt figures several forms similar to this under the name of Cucullfea
Munsteri, in his " Der Jura," though none of them appear to agree exactly with
our shell. The true C. Munsteri, as figured by Goldfuss (Petrefact. Germ. tab.
122, fig. 10), diifers, at least from our species, in having a rather distinct ridge
along the cardinal margin. All of our specimens also appear to be entirely desti-
tute of radiating striae ; though there may be very fine radiating lines, where the
surface is well preserved.

Locality and position. — Southwest base of Black Hills, associated with other
Jurassic fossils. (Type 201.)

FAMILY UOTONIDJE.

Shejl equivalve, inequilateral, regular, smooth, plicate or tuberculate,
nacreous within ; epidermis thick, covering a prismatic cellular layer ;
margins closed and smooth within ; ligament external. Hinge varying
with the genera and subordinate groups. Muscular impressions deep ;
pedal scars three in each valve, two behind the anterior adductor, and
one before the posterior ; pallial line simple.

Animal with mantle margins disconnected, excepting between the anal
and branchial regions ; not produced into siphonal tubes, but fringed in
the branchial, and usually plain in the anal regions. Foot very thick,
tongue-shaped, often byssiferous in the young, but rarely so in the adult.
Gills elongate, subequal, free or connected with the mantle or abdominal
sack behind. Labial palpi usually united behind,

Conchologists differ very widely in regard to the number of generic and sub-
generic heads under which the numerous species included in this family should be

11 KI'TI I.IAN AGE JURASSIC PERIOD. 91

arranged. The following arc tin- names of the genera most usually admitted by
late writers. \i/.. : /'///«.. Ainxlutitn. lii/xmnitHloiitn, Miii-i/Ki-itumi, Mmtm-ninlylltnt, and
llmli'iln. I'm!'. Ai^a»i/.. ho\\e\er. who lias disserted, with much care, many of our
Aim-rii -an >pi-cies. timls that they present marked differences in the arrangement
of the .yills, and the position of the e<j«,rs in the same, as well as in other anatomical
details, from winch lie is led to the conclusion that there are at least twenty-two
distinct genera amongst our species usually referred to Unlo, Atiodonta, Alasmo-
i/onfd, and Mnr</m-!/<nt<t. For these groups he has adopted the following names,
vi/.. : Dymomia, Ag. ; Scalenaria (Raf.), Ag. ; Truncilla (Raf.), Ag. ; Lamprilu,
Rat'.; Ciiiitln/rin. Swainson ; l-'.u ri/uin, Raf. ; Mdaptera, Raf. ; Alasmodonla, Say;
Obornriii. Kaf. ; Mi< •nuiii/ii, Ag. ; C'.'//"'".'/' "'"• Ag. ; Plagicla, Raf.; Orthonymus,
Ag. ; Tri't'M/nitiit, Ag. ; Qumlniln, Raf. ; Rotundaria, Raf. ; Complanaria, Swainson ;
Pleurobemn, Kaf.; I'n iopsis, Swainson ; Margaritana, Schumacher ; Hemilasterna,
Raf., and L'nin. Ketz.1

Mr. T. A. Conrad, of Philadelphia, who admits many of these groups as
suli^enera under l'ni<>, also proposes to adopt the following additional subgenera,
mainly tor the reception of foreign species, viz. : NoduJaria, Con. ; Iridea, Swainson;
Mi/tt'-a, Tnrton ; I.<i/i<;<,l<tr!<i,Con.; Coflatura, Con. ; Cunicula (Sw.), Con. ; Glebula,
Con.; UnioiiK i -us, Con., and Theliderma, Swainson. The following he proposes as
full genera: Citcumaria, Con. ; I/yriopsis, Con., and Monodontina, Con.

As an example of the widely different views entertained by authors in regard to>
the classification of these mollusks, we should remark that Dr. Isaac Lea, who has
jjivcn more attention to the study of the Unionidce than perhaps any other person,
includes the whole, along with some others not generally admitted in this family,
under two generic heads, for which he adopts the names Margaron and Platiri*.
Under the first of these he ranges as subgenera, Triqwtra, Prisodon, Uhio, Margari-
tana, ManocondylcEa, Anodonta, and Dipsas, ; and under the second Iridina, SpatJm,
and Mycetopus?

Mr. Niclin went still farther in this direction, and included Unio, Anodonta, Alas-
modonla, Iridina, Dipsas, Syria, and Costal ia as members of a single genus !s

The family Unionidte has a wide geographical distribution, but is most numer-
ously represented in the streams of North America. Although apparently repre-
sented as far back as the Jurassic period, it is pre-eminently characteristic of the
present epoch, since the species and genera are far more numerous now than they
were during any of the past geological periods. The existing species also present
much greater diversities of form and ornamentation, and sometimes attain larger
sizes than are known to occur amongst those now extinct.

1 Wcigmann's Arch. 1852, p. 41. * Synopsis Naldes, 3d ed. Phila. 1852.

• Trans. Phil. Soc. VIII, p. 398.

92 PALAEONTOLOGY OF THE UPPER MISSOURI.

Genus UNIO, RETZIUS.

Synon.'—Unlo, RF.TZ. Diss. Phys. 1788, 16.— BRITG. Jour. d'Hist. Nat. 1792, and Encyo. Meth. I, tab. 247.— Cuv.
Tab. Elem. 427.— LAMK. Prod. 1799, »7, and Syst. 1801, 114.

Mya, HUMPHREY, Mus. Coll. 1797, 59 (not Lixx.).

Limnium, OKES, Lehrb. d. Naturg. Ill, 1815, and 1821, Naturg. f. Schnl. 651, 8.

Klliplo, RAP. Jour. Phys. torn. 88, 1819, 426, and 1820 Monogr. Bivalves of the Ohio. . . .

Margarita (part), LEA, Trans. Am. Phila. Soo. VI (u. s.), 1 (not LEACH, 1819).

Cunicula, SWAINSON, Malae. 1840, 267, and 378.

Margaron (part), LEA, Synop. Naid. (3d ed.), 1852, p. xvii.
Elym. — Unio, a pearl.
Type. — Afya pectorum, LINN.

Shell variable in form, usually oval, elongate or oblong ; surface covered with a
brownish or olivaceous epidermis, sometimes striped with greenish and olive bands.
Beaks often eroded. Nacre white, yellowish, flesh-colored, or purple. Hinge
variable, generally with two anterior teeth in one valve, and one in the other, or
two in each ; posterior teeth elongate and laminar, usually two in one valve and one
in the other.

Animal, in the typical species, with gills free from the abdominal sac, their
posterior extremity attached to the mantle ; eggs in the female filling the whole
extent of the outer gill ; mantle fringed at both syphonal openings. (Agassiz.)

As above restricted, it will be rather difficult to determine the geological range
of the genus Uhio, since some of its more important distinctive characters are such
as belong to the softer parts of the animal only. The oldest known species appa-
rently belonging to this genus have been described from the Jurassic rocks, though
it is somewhat doubtful whether these are true Uniones. It was formerly supposed
that some Carboniferous and Devonian shells belonged to this genus, but they are
now all known to belong to Cardinia, Carbonocola, and other extinct groups.
Several species apparently presenting the characters of this group have been de-
scribed from the Wealden beds, but this type of life seems not to have been very
generally distributed over the world until the Tertiary epoch; and it undoubtedly
attains its greatest development at the present time, and in the streams of this
country. (Type 192.)

Unio nucalis.

(PLATE III, Fig. 13, a, b, c.)
Unio nucalis, MEEK & HAYDEN, Proceed. Aead. Nat. Sci. Phila. March, 1858, p. 52.

Shell longitudinally oval, gibbous in the central and nmbonal regions. Anterior extremity rather narrowly
rounded ; base semi-oval, sometimes rather prominent near the middle ; posterior end subtruncate, or forming a
regular curve from above, and rather narrowly rounded below. Beaks moderately depressed, located about half
way between the middle and the anterior end, not eroded ; posterior umbonal slopes prominently rounded.
Surface marked by fine obscure concentric lines, and more or less distinct marks of growth ; tbe latter becoming
small, and very regular wrinkles on the beaks.

Length, about 1.63 inch ; height, 1.05 inch; breadth, 0.82 inch.

1 A number of the names mentioned in connection with the family Unionidee are doubtless only
synonyms of Unio; but until the limits of this genus have been more satisfactorily determined, it, is
probably better to include only those more exactly synonymous with the genus as restricted to the
typical forms.

UKI'TI MAN AGE. J U R ASSIC PERIO D. 93

Although apparently associated with an Ammonite (A. Ifenryi), and a small
Ottiri'tt, tliis «.hell seems to present, as far as we ha\e been able to see, the characters
of a true I'/ito. We arc the more inclined to regard it as belonging to that genus,
hi consequence of the fact that we also find in the same matrix a small Planorbig,
and apparently a \'<ilr,tlit, and a Vin'jHiriu. None of our specimens show the hinge
very satisfactorily, though in one left valve (PL III, Fig. 13,c.) it is seen to be rather
thick, a little arched, and provided with a long, posterior lateral tooth, extended
parallel to the cardinal margin, from which it is separated by a deep groove, for
the reception of a similar tooth in the other valve. The anterior tooth is com-
pressed, irregular, somewhat corrugated, and located nearly under the beaks; while
the ligament is in all respects apparently similar, in form and position, to that of
our recent Uniones.

Specimens having the surface well preserved sometimes show very small, radiat-
ing wrinkles on the posterior side of the umbones, near the hinge; in most cases,
however, these are obsolete. A small, obscure, linear ridge is also generally seen
extending from the back part of each beak obliquely backward and. downward, just
within the prominent umbonal slopes. The minute concentric wrinkles are very
regular on the beaks.

The specimens of this species we have seen were not broken directly from the
rock in place, but from the composition, color, &c. of the matrix, and the circum-
stances under which they were found, we are led to think they occur in a Jurassic
bed seen at the locality where they were found, though we are not positively satis-
fied they may not be Cretaceous or Tertiary species. They differ, however, speci-
fically from any of the forms yet known in these rocks in the northwest.

Locality and position. — Southwest base Black Hills. Jurassic. (Typo 196.)

FAMILY CRASSATELLLD^. (See page 34.)
Genus ASTARTE, SOWERBY.

SJHO*. — Astarte, 3. SOWBRBT, Min. Conch. II, 1816, tab. 137. — LAJOXK AIRF,, Monogr. (D Mem. Soc. de Hist. Nat. de Par.
I, 1823, 129. — FLEXING, Brit. An. 1828, 409.— RAKO. Man. 1829, 314. — DBBBATES, Encyc. Heth. II,
1830, 76; III, 653.— SCACCBI, Osserva*. Zoolog. 1833, No. 2.— BBORX, Leth, 1837, 374.
Tridonta, Scam. Ensai, 1817, 146.— MOLLEB, Iris, 1832, 135.
Cramua, Li«K. Hist. Nat. V, 1818, 554.— FMUBBAC, tab. Syst. 1821, p. zlii.— SCHWBIOO, Natgsch. 1820,

710.— BLAIJCV. Malaool. 1825, 557.
ATcamVi, LBACB, Jour. PhjB. I, 1819, 88, 465.— BLAIKY. Halaool. 1825, 558.

t Goodallia, TCRTOH, Brit. Bivalves, 1822, 77 FLEMIIO, Brit. An. 1828, 409 and 429.— FORBES, Malac. 1838,

48.

Martrina, BROWS, Brit. Conch. 1827, tab. xvi ; and Conch. Text-Book, 1833 (VI ed. 159).
Elym. — Aiiartr, the Syrian Venus.
Examp. — V'enta Dmrnoitieiuit, Hour.

Shell oval, Bubtrigonal, or suborbicular, thick, usually compressed,
closed. Surface smooth, or marked with concentric strisc or undulations ;
ligament external ; lunule generally well defined. Hinge with two strong
diverging primary teeth in one valve, and one or two in the other. Im-
pressions of the adductor and pedal muscles deep and well defined;
pallial line simple.

A few species have been referred to this genus from Devonian and Carboniferous

94

PALAEONTOLOGY OF THE UPPER MISSOURI.

rocks, but too little is known in regard to the hinge and interior of these shells to
warrant the conclusion that they are beyond doubt true Astartes. Two species,
described by Prof. King, from the Permian rocks of England, possess the external
characters of this genus, and one of them, at least (A. Vallisneriana), as since
figured by Prof. Geinitz (Dyas. PL 12, figs. 24 and 25), seems also to present the
dentition of the Astartes.

From the Trias, Prof. F. M. Eoemer has described three species of Astarte, and
several are known from the Liassic rocks. In the later members of the Jurassic
sjstem, particularly in the Oolites, the species are quite numerous. The genus
also ranges through the succeeding formations, and probably reached its greatest
development during deposition of the Tertiary rocks. It is, however, well repre-
sented in the seas of the existing epoch. The recent species are usually found in
northern latitudes. They occur on the shores of North America, Northern Europe,
Norway, Greenland, &c.

Astarte fragilis.

(PLATE iv. Fig. 7.)

Astarte fragilis, MEEK & HATDEK, Proceed. Acad. Nat. Sci. Phila. May, I860, 183.

Shell small, rather broad oval, thin, moderately compressed. Anterior end rounded ; base nearly straight along
the middle, rounding up regularly in front, and more abruptly behind ; posterior extremity obscurely subtruncate ;
dorsum straight and slightly declining behind the beaks, which are small, obtuse, rather depressed, and located a
little in advance of the middle. Posterior umbonal slopes prominent. Surface ornamented by distinct, irregular
concentric wrinkles, and fine parallel strise. (Hinge and interior unknown.) Pallial margins crenulate.
Length, 0.45 inch; height, 0.32 inch; breadth, about 0.18 inch.

The rather unusual thinness and oval form of this little shell lead us to doubt
whether it can be a true Astarte, though even in this respect, as well as in its other
characters, it is evidently quite similar to some Jurassic forms generally placed in
that genus.

In several respects it resembles quite closely the small thin variety of A. excavata,
Sowerby sp., figured by Morris and Lycett in their monograph of the English Oolitic
fossils, pi. 9, fig. 19 (Palaeont. Soc.), but its beaks are located further back, and its
posterior margin is narrower and more oblique ; while its lunule does not seem to
be excavated as in that species.

Locality and position. — Southwest base of the Black Hills, in the lower Jurassic
beds of that region. (No. 194.)

Astarte inornata.

(PLATE III, Fig. 12, a, b.)
Astarte inornata, MEEK & HAYDEN, Proceed. Acad. Nat. Sci. Phila. May, 1860, 183.

Shell subelliptical, compressed; extremities rounded, the posterior margin forming a broader curve than the
other. Base semi-elliptical in outline ; dorsum declining from the beaks, the anterior slope being a little concave,
and the other nearly straight, or slightly convex. Beaks moderately elevated, compressed, located just in
advance of the middle. Lunule rather deep, lance-oval, bounded on each side by a more or less distinct angle.
Surface marked by concentric strise, with a tendency to develop small, very obscure concentric wrinkles.

Length, 1.15 inch; height, 0.79 inch; breadth, about 0.44 inch.

We only place this shell in the genus Astarte from its similarity to several
Jurassic species of that group, not having seen its hinge or interior.
Locality and1 position. — Same as last. (No. 202.)

REPTILIAN AGE. JURASSIC PERIOD. 95

FAMILY TAXCREDITDjE.

Shell oval-subtrigonal, longer than high, never very gibbous, equi valve,
sul>e<iiiilateral, nearly smooth; valves gaping or closed; hinge with car-
dinal, and usually posterior lateral teeth; muscular impressions moderate,
smooth; pallial line simple; ligament external, or probably sometimes
partly internal.

Animal unknown.

The genus Tancredin presents a combination of characters that seem to forbid its
admission into any of the established families of Lamellibrarchiata. Until the affini-
ties of this and some little known fossil shells, apparently not more than generically
si |>;iratcd from it, can be better determined, it has been thought preferable to pro-
jMisr a distinct family for their reception. It is perhaps most nearly related to the
Cardiidce (in which some authors place it) than to any other family, though the
more elongate, compressed, Donaciform outline and smooth surface of these shells
i:i\i' them a pe'culiar physiognomy, very unlike any of the genera known to belong
to that family; while some of the closely related fossil forms belonging apparently
to one or more undescribed genera are known to be distinctly gaping in front, as
well as behind, a feature unknown in the Car<lii<l« .

Their simple pallial line, and external ligament, would exclude these shells from
the Mactrida-, which they resemble in form ; while the former of these characters
shows that they cannot be placed in the TeUinidte. Their general physiognomy,
not less than their comparatively small, smooth muscular scars, show that they
cannot be properly included in the Lucinidce, to which they are often referred.

This family, in addition to the typical genus, includes the recently proposed genus
jr>i/.-ia, of the Cretaceous rocks of California.

Genus TANCREDIA, LTCETT.

Spurn. — Dtmax, Marira, &c. (sp.) of DUNKEB, DBSHAYKR, D'OBBioicy, and others.

Tancrtdia, LTCITT, Ann. Hag. Nat. Hist, vi, 1850, 407.— MORRIS and LTCBTT, Moll. Great Oolite, 1853, 90.

Hettanyia, TKRQCEM. — BDVIOHIKB, Statist. Qeol. Mineral, et Palaont. dn Dept. de la Mas. 1852, Atlas,

14.— TKBQCKM, Bnl. Soo. Qeol. FT. torn. 10 (2e tit.), 1853, 364.
Etym. — Dedicated to Sir Thomas Tancred.
Typr. — Tancredia donaciformit, LTCETT.

Shell depressed subtrigonal, or longitudinally subovate, rather compressed, without
a defined lunule ; basal margin semi-ovate or semi-elliptical in outline, not crenate
within ; posterior side wider and more convex than the other, sometimes gaping ;
anterior side more or less attenuate or pointed, and closed; beaks subcentral,
usually small, contiguous ; ligament short, external, occupying a small depression.
Hinge with one obtuse cardinal tooth in each valve, fitting into a corresponding
cavity in the other ; sometimes a small accessory cardinal tooth at the anterior side
of the cavity in the right valve, and on the posterior side in the left. Lateral teeth
large, obtuse posterior, that of the left valve prominent, and fitting into a depression
in the tooth or callosity of the other valve. Muscular impressions oval ; the simple

96

PALAEONTOLOGY OF THE UPPER MISSOURI.

pallial line obscure, and" remote from the margins. Margin of the right valve in
front of the beaks, somewhat thickened, slightly projecting, and received into the
margin of the other valve, though there are no proper anterior lateral teeth.

This genus dates back to the Liassic period ; some ten or twelve species having
been identified by M. Buvignier. and M. Terquem, in rocks of that age, in France.
So far as we are acquainted, it has not yet been recognized above this horizon on
the continent, while in England it is only known in the lower Oolite. In America
it ranges still higher, a single well-marked species having been described by us from
Cretaceous beds, at tjie mouth of Judith Eiver, on the Upper Missouri. In this
country it also made its first appearance in Jurassic rocks.

This genus is closely allied to the Cretaceous genus Meekia, Gabb (Palaeont. Cali-
fornia, I, 1864, 191), but differs in always having the anterior side closed instead of
gaping, as well as less angular. There are also some differences in the hinge plate;
while the ligament in Meekia is said to be only "subexternal."

Tancredia Warrenaiia.

(PLATE III, Fig. 7.)
Tancredia Wamnana, MEEK & HAYDEH, Proceed. Acad. Nat. Sci. Phila. May, 1860, 183 ; ib. Oct. 1860, 418.

Shell small, trigonal ovate, moderately convex ; anterior half a little narrower and more compressed than the
other, narrowly rounded at the extremity ; base forming a broad gentle curve ; posterior side snbtruncate, angular,
or very abruptly rounded below. Dorsum sloping from the beak ; the anterior slope being slightly concave in
outline, and the other nearly straight, or a little convex. Beaks rather elevated, but not extending much above
the cardinal edge ; posterior nmbonal slopes prominent or subangular. (Surface and hinge unknown.)

Length, 0.50 inch ; height, 0.33 inch ; breadth, about 0.14 inch.

We have not yet had an opportunity to see the hinge or the pallial line of this
shell, and consequently only place it provisionally in the genus Tancredia. Its
form, however, is such as to leave little room for doubt in regard to its relations to
that group. As our specimens are casts, they do not give a very clear idea of the
surface, though it seems to have been only marked by lines of growth. It is only
the immediate extremity of the posterior margin that appears to be a little truncated
vertically. Our specimens do not show whether the valves were gaping behind or
not, but they have the appearance of being closed.

This species resembles more or less closely several of those figured by Morris and
Lycett in their monograph of the fossils of the Great Oolite, but seems to differ
specifically from them all, as well as from those figured by Terquem and other
continental authors. It agrees most nearly in size and general appearance with
T. brevis, Morris and Lycett (Mol. Gt. Oolite, part 3, fig. 8, pi. xiii, Palaeont. Soc.),
but is higher in proportion to its length, and more rounded at the extremities.

Locality and position. — Jurassic beds at southwest base of the Black Hills. (No.
204.)

Tancredia? aequilateralis.

(PLATE III, Fig. 8.)

Tancredia f seguilateralis, MEEK & HAYDEN, Proceed. Acad. Nat. Sci. Phila. May, 1860, 183 ; ib. Oct. 1860, 418.

Shell very nearly elliptical, moderately convex ; anterior end rather narrowly rounded ; base forming a broad
regular, semi-elliptic curve ; posterior end slightly truncate on the upper oblique slope, narrowly rounded below,
and apparently not gaping. Beaks depressed, located a little in advance of the middle. Surface of cast retaining
traces of concentric strise. (Hinge and interior unknown.)

Length, 1 inch; height, 0.64 inch; breadth, about 0.16 inch.

REPTILIAN AGE. JURASSIC PERIOD. 97

The specimens of this species in the collection are casts, in a rather soft yellowish
sandstone, showing neither the hinge nor the muscular and pallial impressions
Consequently \ve have no means of determining with much confidence to wlrit

genus it properly belongs. In form and general appearance it resemhles some
species of the above group, and the ca-t shows an impression behind the beaks,
such as would be left by a posterior tooth or callus similar to that seen in many

>peeies (if TiilX-i-iiliit.

I.<xii/iti/ ami jM*t(l<m. — Jurassic heds at southwest base of the Black 1 1 ills. (No.
298.)

FAMILY CARDIIDJ3.

Shell free, regular, equivalvc, usually cordiform and gibbous; margins
cli.srd or raping posteriorly, crenate or dentate within ; surface generally
with radiating- rost.-i1, or variously sculptured, sometimes smooth. Hinge
UK ire or less variable, usually with cardinal and lateral teeth; ligament
exU-riiul. short and prominent. Pallial line simple, or slightly sinuous.

Animal with mantle margins open in front; siphons very short, dis-
tinct, and furnished along the sides and bases with tentacular filaments,
palpi sk'iidiT and pointed. Gills two on each side, connected together
behind. Foot very long, bent or geniculate.

The recent genera usually included in the family are Cardium, Lcevicardium (or
I.iiK-iii-i/ini/i), Coivnlum, and Papyridea, The species constituting the recent genus
Adacna (including Monodacna and Didacna), sometimes placed in this family, seem
to belong to a distinct group, on account of their elongated, plain, and united
siphons, and their shorter compressed foot and deeply sinuous pallial line.

The Jurassic and Cretaceous group Protocardia, the Cretaceous Liopistha, the
curious Eocene Lithocardium, and several unnamed extinct genera, also belong
here. The remarkable palaeozoic genus Conocardium is likewise often referred to
this family, but its distinct coarsely prismatic cellular shell-structures has led some
naturalists to think it may even belong to the very widely removed, anomalous
order? Rudisicu. Although not prepared to adopt this conclusion, we are by no
means clearly satisfied that it belongs properly to the Cardiidae.

Genus PROTOCARDIA, BERYCH.

SynoH.— Cardium (sp.), SOWEBBT, D'OBBioirT, and others.

Protocardia, BKTRICH, Zeitschr. f. Halak. 1845, 17.— GBIKITX, Grnndr. d. Vergt. 1846, 421.— COHBAD, Report

Hex. Bound. Survey, 1858, 150.— MEEK, Smithsonian Check List North American Cret Fossils, 1864.
Elym. — ir^rrot, first ; Cardium.
Type. — Cardium THIlnnum, SowERBT.

Shell globose-cordate, closed all around ; subequilateral and but slightly obliquo.
Hinge with one or two cardinal teeth, and usually one anterior and one posterior
lateral tooth, in each valve. Surface ornamented with very regular concentric
costse or strioe on the sides and front of the valves, and radiating rostu- behind (the

13 December, 1804.

98 PALAEONTOLOGY OF THE UPPER MISSOURI.

concentric markings sometimes very fine or obsolescent). Muscular impressions
distinct ; pallial line somewhat sinuous.

This group is nearly related to some of the sections of Cardium, but may be
generally readily distinguished by its peculiar surface-sculpturing and slightly sinuous
pallial line. Still, as its principal difference from forms referred by many to the
genus Cardium consists in its surface-markings, most palaeontologists regard it as
forming only a subgenus under that group. Although we have no very serious
objections to this conclusion, we think it more properly constitutes a distinct genus
from Cardium as typified by C. costatum, Lin. Although it can nearly always be
identified by its sculpturing alone, there are a few Cretaceous species in which these
markings are very faintly defined, or probably in some case entirely obliterated.
The radiating costae or striae on the posterior side of the valves, however, are nearly
always present, even when the concentric sculpturing on the sides and front are
obsolete. Very rarely, however, the radiating markings are obsolete ; even in these
cases, however, some traces of their existence can be seen in the crenulated margins
of the posterior side of the valves.

This genus seems to be entirely confined to the Jurassic and Cretaceous rocks,
unless a few recent shells, such as Cardium pectenalum, Lin. (not Lamk.), and C.
lyratum, Sowerby, from the Philippines, may belong to the same group. These two
species agree in form, and have very nearly the surface-markings of Protocardia, and
unless they present some differences in the hinge or interior (we are not acquainted
with the interior of these shells), they must be nearly related to the group under
consideration. Still, they differ in having the sculpturing on the sides and front of
the valves, somewhat oblique, and intersecting the anterior margins, instead of
concentric and curving upwards in front. They were referred, by Swainson, Morch,
Chenu, Adams, and others, to Liocardium, but they differ materially from C. Icevi-
gatum, usually regarded as the type of the la^er group.

Protocardia Shumardi.

Cardium Shumardi, MEEK & HAYDEN, Proceed. Acad. Nat. Sci. Phila. May, I860, 182.
Cardium (Protocardium?) Shumardi, MEEK & HAYDEN, ib. 418.
A B

CD

Protocardia Shumardi.

A. Side view of internal oaat. B. Outline front view of same.

Shell small, oval snbcordate, rather gibbous ; anterior side rounded ; base more broadly rounded ; posterior side
obliquely subtruncate above, and intersecting with an abrupt curve, the base below. Hinge margin rather short,
and sloping slightly from the beaks, which are moderately elevated, gibbous, and nearly central ; posterior umbonal
slopes snbangular. Surface of oasts retaining only traces of small radiating costas, or lines, on the prominent
posterior umbonal slopes and the flattened postero-dorsal region. (Hinge and interior unknown.)
Length, 0.44 inch ; height, 0.37 inch ; thickness, 0.32 inch.

Our specimens of this species being casts, it is impossible to determine whether
or not the surface was marked by regular concentric stria? on the middle and
anterior portions, though it probably was. In its general appearance it bears some

i: TPTILIAN AGE. JURA SSIC PE RIO D.

mblanre to C. m-i/nfinn, Meek (Trans. Albany Inst. 1856), a Cretaceous species
from Vancouver's Island, l>ut. its truncated posterior margin is more oblique, and
its posterior uiiihonal slopes more angular.

It seems to be more nearly related to the Oolitic species C. aemicostatum, Lycetl
(An. Nat. Hist. ls.~>0), hut is longer in proportion to its height, and has less dis-.
tiiictly angular nmbonal slopes. The specific name was given in honor of Dr.
(Jenrge (i. Shuinard, formerly of the Geological Survey of Texas.

/..»<,///// ,,,,,! jMwi'fltm. — Southwest base of the Black Hills, in Jurassic beds, asso-
ciated with I:'n in ir,-<>t i* nirtn, Belemites densus, Grammatodon inomatw, &c. (No.
191.)

FAMILY ANATTNIDJE. (See page 3G.)
Genus MYACITES (Senior.), MUNSTER.

Synon.— M-jaeita (part.), SCBLOT. Petref. 1820, 176 — BHOXS, Leth. 1837, 174.— Maitnu, in QOLDF. Petref. Germ.

II, 1840, 259 — WOODWAED, Man. Moll. 1850, 322.— Mourn and LTCITT, Moll. Ort. Oolite, 1853, 111.
Panopma. (sp.), D'OaiuoxY, Palsont. Fr. Ill, 1844, 329, and of various other* (not Menard de la Groye,

1809).
flruromya, AoAisiz, Etud. Crit. IV, 1845, 231.— LEOHH. and BBOKX, Jahrb. 1846, p. 122.— CHKVC, llan.

Conch. II, 1862, 28.

ifyopiii, AOAIWIZ, Etud. Crit. IV, 1845, 251. — Crump, Man. Conch. II, 1862, 28.
Kti/m. — ftv'f, a mussel.
Ezamp. — Myarites mviculoitltt, Sen LOT.

Shell longitiulinally ovate, oblong, or more or less elongate, very thin, nearly or
quite equivalve. without a defined lunule ; more or less gibbous in the central and
umbonal regions. Extremities gaping, the posterior side more than the anterior,
which is often nearly closed. Beaks moderately gibbous, placed between the
middle and the anterior extremity. Hinge probably always with one more or less
developed cardinal tooth in each valve; cardinal margin sometimes inflected, but
more generally erect, excepting near the beaks ; ligament external, short. Valves
often with a broad, undefined depression extending from the beaks to the basal or
antero-basal margin, usually deepening and widening as it descends. Surface Avith
concentric stria?, and often more or less regular concentric ridges or costae, the whole
being, when well preserved, usually beset with minute granules. Muscular and
pallia! impressions very faintly marked ; sinus of the latter broad and rounded.

Animal unknown

There is some confusion in regard to the limits of this genus, some authors
including in it a wide range of forms evidently belonging to several genera, while-
others restrict it to a few of these, or reject the name entirely, placing the species
in one or more of the allied groups. The name Myadtes has perhaps met with less
general acceptance because it was not proposed by Schlotheim, who first used it, as
the name of a distinct genus, but to designate certain fossil shells supposed by him
to belong to the existing genus Mi/a. He merely added the termination ties in this
as in other instances, because the species he was figuring and describing were fossils,
and not because he supposed them to belong to a new genus. By examining his
work, it will be seen he wrote all the names of the genera to which he referred his

100 PALAEONTOLOGY OF THE UPPER MISSOURI.

fossil species in the same way; thus he ranged the fossil shells he supposed to
belong to the genera Pecten, Donax, Unio, Buctinum, &c., under the names Pec-
tenites, Donacites, Unionites, Succinites, &c. Hence we cannot accept any of these
as generic names established by him, when he may have by mistake included types
of undescribed genera.

The first author, after Schlotheim, so far as our knowledge extends, who used the
name Myacites, was Bronn (Leth. 1837); but as he used it in much the same sense
that Schlotheim did — that is, as a provisional receptacle for fossil shells supposed
to belong to the genus Mya, as he did Turbinites, &c. — we can scarcely regard him
as having established it as a genus. In 1840, however, Munster adopted it regu-
larly as the name of a distinct genus, and described under it Myacites musculoides,
M. ventricosus, M. elongatus, M. radiatus, M. mactroides, Schlot. ; M. radiatus, M.
grandis, M. obtusus, Munster ; and M. Albertii, Voltz ; all of which appear to be
congeneric with the first or typical species, with possibly one or two exceptions.
We regard it as an established genus from that date, with M. musculoides as its type.

As already stated in the remarks respecting the affinities of the genus Allorisma
(page 37), this group, as we understand it, seems to be very closely related to the
Permian and Carboniferous shells upon which that genus was founded. For a
statement of the principal points of difference between these two groups we would
refer the reader to the remarks on page 37, in connection with the description of
Allorisma.

These shells are also related to the genus Pholadomya, from which they differ in
never having radiating costse, as well as in their granulated surface. They also
seem to be entirely destitute of pearly internal layer seen in the shells of that
genus. From Panopcea, to which they are often referred, they differ in being much
thinner shells, as well as in their granulated surface and much more faintly marked
muscular and pallial impressions. Indeed, they appear, from all analogy, to belong
even to the very distinct family Anatinidce, instead of the Saxicavidce.

The genus Myacites probably first appeared during the Triassic epoch, though we
are not sure that some of the species usually referred to Allorisma from the older
rocks are reaUy generically distinct. It seems to have reached its maximum de-
velopment during the deposition of the Jurassic rocks, and continued to exist until
after the commencement of the Cretaceous epoch, during the earlier part of which
it probably became extinct.

JUyacites nebrascensis.

(PLATE IV, Fig. 5.)
Myacites Nebrascensis, MEEK & HAYDEN, Proceed. Aoad. Nat. Sci. Phila. May, 1860, 182 ; ib. Oct. 1860, 418.

Shell elongate-snbelliptieal, rather convex ; extremities narrowly rounded, the posterior end being sometimes
apparently obliquely subtruncate, and more or less gaping above. Base nearly straight, or very slightly sinuous,
along the middle ; rounding up gradually toward the ends. Dorsum behind the beaks, concave in outline ; poste-
rior umbonal slopes gibbous, or prominently rounded ; antero-ventral region a little compressed, or contracted, from
near the middle of the base, obliquely forward and upward. Beaks moderately elevated, gibbous, incurved, and
located near the anterior end. Surface ornamented by concentric striae, and small, very obscure, irregular parallel
wrinkles.

Length, about 1.43 inch ; height, 0.69 inch ; breadth, 0.59.

Our specimen being a cast, has probably lost some of its finer surface characters,

REPTILIAN AGE. J UR A S8IC PERIOD. 101

though it evidently never had radiating costa*, like we see on well-marked species
nt' /'/ii>/<n l» ini/'i, ;is detined by most authors. Its true generic relations, however,
must remain doubtful until better specimens can be obtained.

l.<xiiliii/ ami /'<>.* iii<, n. — Southwest base of the Black Hills, near the lower part
of the Jurassic series of that region.

ITIyacite* Nnbellipticnft.

(FLAW IV, Pig. 8, a, 6, »)

Panoprn (Myacita) tubelliptica, If MX & HATI>KS, Proceed. Aoad. Nat. SoL Phlla. March, 1858, 62;
ib. Oct. I860, 418.

Shell narrow, elliptical, or nnbovate, moderately convex ; extremities rather narrowly roonded, the posterior end
being more conipreitsed than the other ; base forming a very broad semi-elliptic curve ; beaks located in adrano*
of Uie middle, ratlu-r depressed, the right one sometimes a little more elevated than the other ; surface of oast
marked by small irregular wrinkles of growth ; binge and muscular and pallial impressions unknown.

Length, 2.0* inches ; height, 1.09 inch ; breadth, 0.70 Inch.

In its general appearance this species resembles Pttnopoea peregrina, D'Orbigny,
as figured 1>\ Murchison, de Verneuil and Kcyserling, in their Geol. Russ. II, part 3,
pi. \1, fig. 10, but it is proportionally a little shorter, narrower posteriorly, and more
com ex in the antero-ventral region, while its extremities appear to be less gaping.

It is e\en more nearly similar in form to P. Neocomiensis, Lehm. sp., from the
Lower Green Sand of the Old World, but differs from most of the figures we have
seen of that species, in being more narrowly rounded at the extremities, and in
having less prominent beaks.

Loi-tiliti/ n ml position. — Southwest base of the Black Hills, near the lower part
of the Jurassic series of that region. (Type No. 200.)

Genus THRACIA, LEACH.

Synon — Thracia, LKACJI, MSB. 1819 ; BLAIKVILLK, Diet. Sol. Nat. XXXII, 1824, 347; and Malao. 1826, 564.— RAHO,
Han. 1829, 324.— DKBHATEH, Kncyc. Meth. Ill, 1830, tab. 1832; ib. p. 1038; and in LAME. 24 ed. VI,
1835, 82 — MBIKB, Syn. 2d ed. 1830, 119, Ac. Not Thracia, Westwood, 1840 (gen. Insects).
Odoncitutut, DA COSTA, Cat. Syst. 1829, 32.
Odontocineta (Corr.), AoAggix, Index Univerealis, 1846, 255.
Eiym. — Sfi*M<, Thracian f
Type. — J/jro pub tt cent, POH.

Shell longitudinally oblong or ovate, inequivalve, rather thin; posterior side more
or less contracted, compressed, and gaping; surface concentrically striate, sometimes
minutely scabrous. Hinge consisting of a thick, slightly prominent cartilage pro-
cess in each valve, with a free crescentic ossicle in front. Ligament partly internal.
Pallial sinus rather shallow ; muscular impressions small. Outer shell layer con-
sisting of distinct nucleated cells.

The genus Thracia was probably introduced during the deposition of the Liassic
or oldest Jurassic rocks. It also ranges through the later formations, and appears
to attain its greatest development in our existing seas. The species, however, were
quite numerous at several intermediate periods, particularly during the deposition
of the Neocomian rocks.

We observe several authors place RupuxHa, of Bellevue, 1802, as a subgenus

102

PALAEONTOLOGY OF THE UPPER MISSOURI.

under Thracia, while others adopt it as a distinct genus. Whether we regard the
type upon which it was founded as generically or subgenerically distinct, however,
Bellevue's name should probably not be retained, since it was used by Brisson, in
1760, for a genus of birds, now adopted by ornithologists.

Thracia? sufolaevis.

(PLATE IV, Fig. 4, and 4a.)

Thracia? sublxvis, MEEK & HAYDEN, Proceed. Acad. Nat. Sei. Phila. May, 1860, 182; ib. Oct. I860, 418.
Shell elongate, or narrow oblong-oral, rather compressed. Anterior end narrowly rounded ; base nearly straight
along the middle, rounding up toward the ends ; posterior side longer than the other, rounded, or slightly truncate,
and apparently gaping a little at the extremity ; dorsal border straight or concave in outline, and nearly horizontal
behind the beaks, declining more abruptly in front. Beaks moderately elevated, the right one being usually a
little higher than the other ; located in advance of the middle ; posterior umbonal slopes prominently rounded.
Surface concentrically striate.

Length, 1.19 inch ; height, 0.63 inch ; breadth, about 0.32 inch.

Not having seen the hinge or the interior of this shell, we are left in doubt
respecting its true relations, and merely place it provisionally in the above genus.
Our specimens are all casts, but some of them retain traces of concentric lines,
which appear to be the only kind of surface markings it had. Behind the beaks
there is a narrow area or escutcheon, apparently formed by the thickening or in-
flection of the cardinal margin ; this, however, may exist only on the internal cast.

Locality and position. — Near middle of the Jurassic beds, at the southwest base
of the Black Hills. (Type No. 197.)

Thracia? arcuata.

(PLATE IV, Fig. 8.)
Thracia? arcuata, MEEK & HATDEN, Proceed. Acad. Nat. Sci. Phila. May, 1860, 182 ; ib. Oct. I860, 418.

Shell small, longitudinally snbovate, more or less arcuate, moderately convex. Extremities rather narrowly
rounded, and gaping a little. Cardinal margin sloping from the beaks ; anterior slope more abrupt than the other.
Beaks rather elevated, and unequal, that of the right valve being higher than the other, located in advance of the
middle ; posterior and anterior umbonal slopes prominent. Sides of the valves compressed or slightly concave in
the central region, near the base. Surface of cast retaining small concentric marks of growth. (Hinge and
interior unknown.)

Length, 0.62 inch ; height, 0.34 inch ; thickness, 0.23 inch.

This shell is more nearly related to the last than to any of the other species yet
known from the rocks of the upper Missouri country, but differs in being more gib-
bous, and in having the valves more compressed or concave near the middle of the
base, which imparts an arcuate outline to the ventral border. Its dorsal margin is
also much less nearly horizontal, in consequence of the greater elevation of its beaks.
Like the last, it has along the cardinal border of the internal cast, behind the beaks,
a narrow circumscribed area or escutcheon, bounded by an obscure angle along each
side. Knowing nothing of the nature of its hinge, or pallia! line, we cannot deter-
mine its generic relations with much confidence.

Locality and position. — Same as last. (No. 211.)

Genus PHOLADOMYA, SOWERBY.

Synon. — Pholadomya, G. B. SOWEBBY, Genera Shells, 1823, fasc. 19.— LATH. Fam. Nat. 1825. — DEFRANCE, Diet. Soi.
Nat. t. XXXIX, 1826, 535.— J. SOWERBY, Min. Conch. 1827, tab. 545.— DESHAYES, Encyc. Meth. Ill, 1830,

i: i: PTILIAN AGE. J UR ASSI C PE RI OD. 103

tab. 1832 ; ib. 756 ; again in LAM. 2d ed. VI, 63.— F. A. ROBXEB, Vent. Ool. 1636, 126.— BBO>». Leth.
7, Sh4.— \.iAssii;, Ktu.I. frit. Mol. Fogs. 2d liv. 1842, 37.— ttuttiT, 111. Cat. 1844, 1, 18, 4o. 4o.
iJumytra, KLEJII.V., Ili.-t. I'.rit. An. 1 828, 408 and 424.
t Cymella, MKEK, Siuitluoniau Clik. List Cret. FOM. 1S04, 34.
/.Vyw.— /'A../.1S,- Mya.
Ty/it. — P. Candida, SOWKBBT.

Slicll (liin, equivalve, ]>carly within; longitudinally oblong, oval, or subtrigonal;
inequilateral and vrntricose; extremities usually both gaping, but the posterior
more widely than the other. Surface ornamented with radiating costa?, crossed by
< 'OIK -entrie striir, or uiorc or less distinct, sometimes nodular, ribs. Hinge with an
oli-< lire lamellar tooth, and a small triangular pit in each valve. Ligament short,
M;I!. 1'allial line and muscular impressions generally faintly marked; the
latter broadly sinuate.

The animal of Pholailomya Candida, according to Owen, has its mantle provided
with four openings — a pedal, a siphonal, and an anal aperture, with a fourth small
circular orifice at the under part of the siphons. The gills are thick and finely
plaited, the outer lamina being extended dorsally. The foot is provided with a
small accessor)' bifurcating appendage behind.

Prof. Agassi/, who has produced the most important work on this genus, sepa-
rates the species into two principal sections, and again divides each of these into
several subordinate groups, as follows : —

SKTIOH I.— Specie* Without a Circumscribed Cardinal Area,

1. "IKuIticostata?," AGASSIS.

Shell more or leas elongated ; radiating costn numerous, well defined.
Examples. — /'. itmicoslnta and /'. nulticottata, Ao. (Jurassic and Cretaceout.)

a. " TrigonataV AOASSII.

Shell subtrigonal or more or legs oblong ; anterior side gibbons, often closed ; posterior more compressed and
distinctly gaping ; beaks generally elevated, sometimes perforate. Surface with distinct concentric ridges,
often extending npon the extremities of the valves, and crossed upon the flanks by well-defined tubercular
radiating cost*: cardinal area distinct, bnt not sharply defined.

Examples. — P. arcuata and P. nudn, Ao. (Cretaceous, Tertiary, and Recent.)

3. "Bucardinac," AOASSIZ.

Shell snbtrigonal, or more or less ovoid, gibbous, and comparatively thick ; truncated, somewhat gaping,
and usually flattened anteriorly; posterior side distinctly gaping; beaks gibbons and closely contiguous.
Surface with strong, often tubercular radiating cosUe on the flanks ; muscular and pallial impressions
distinct.

Ezampltt. — P. cincta and P. decuuata, AOASSIZ. (Liat to Tertiary.)

SECTION II. — Specie* With a Circumscribed Cardinal Area.

4. "Flabellatap," AOAMB.

Shell usually much elongated ; radiating costs prominent and often distant, generally confined to the flanks.

General aspect similar to the " Alulticostata," bnt differing in the possession of a defined cardinal area.
Examples. — P. pelagica and P. timilit, AOASSIZ. (Jurassic.)

5. "Ovales," AOASSII.

Shell ovoid, more or less compressed ; one or the other of the extremities gaping : cardinal area sometimes

not very distinct behind ; cost* linear, often orenate.
Example*. — P. tenuicostata and P. pectinata, AGASSI*. (Jurassic.)

6. "Cardissoldes," AOASBII.

Shell snbtrigonal, similar to the " Bucardina" of the first principal division, bnt differing in the possession

of a defined cardinal area, and in having the cosUe lee* numerous and more faintly marked.
Examples. — P. cancel lata and P. cardiaoidet, AGASSIS. (Jurauic.)

,

104 PALAEONTOLOGY OF THE UPPER MISSOURI.

If we disregard the distinctions based upon the presence or absence of a circum-
scribed cardinal area (and there appear to be various intermediate gradations in
this character), the foregoing six groups may probably be reduced to four, by
uniting the "Flabellatce" with the " Multicostatae," and the " Cardissaides" with the
" Bucardince." As thus arranged, these groups would apparently correspond nearly
with what are usually regarded as subgenera, in conchology.

There is, however, another little group, differing, it is believed, from all of those
denned by Prof. Agassiz, though probably nearest the " Ovales." It is only known
in the Cretaceous rocks, and was called Cymella by the writer, in the Smithsonian
Check List of North American Cretaceous Fossils, 1864, p. 34. The type is Pho-
ladomya undata, Meek and Hayden, a small oval, subequilateral, rather compressed
shell, with very regular concentric undulations (like those of Inoceramus), crossed
by impressed radiating lines, only visible near the middle of the valves ; cardinal
area distinct.

Mr. Conrad has also proposed two subgenera under Pholadomya, viz., Anatimya
and Margaritaria. The type of the first is his Pholadomya anteradiata, a Creta-
ceous species ; and the other Avas found upon his P. abrupta, from the Miocene.
We are not acquainted with these shells, but from the -figures and descriptions,
incline to the opinion that they should be regarded as the types of distinct genera,
particularly the latter.

The genus Pholadomya was probably first introduced during the Liassic period,
and attained its greatest development during the deposition of the later members
of the Jurassic system. It was also well represented in the Cretaceous, and some
two or three species have been described from the Tertiary rocks. A single species
only (the type of the genus) is known to inhabit our existing seas. It is found on
the shores of the island of Tortola, West Indies.

Some apparently closely allied forms are found in the Triassic, Permian, and
Carboniferous rocks, but they all want the radiating costa? of the true Pholadomyas,
and are referred to Allorisma, Myacites, Platymya, Chcenomya, &c.

Pholadomya hiimilis.

(PLATE IV, Fig. 3, a, 6.)

Pholadomya humilis, MEEK & HAYDEN, Proceed. Acad. Nat. Soi. Phila. May, 1860, 182; ib. Oct. 1860, 418.
Shell longitudinally oblong, ventrieose. Posterior end rounded, and more or leas gaping ; base nearly straight
along the middle ; anterior end very short, narrowly rounded below the beaks. Dorsum nearly parallel with the
base, slightly concave in outline ; escutcheon lanceolate, and bounded by an obscure angle on each side. Beaks
depressed, gibbous, incurved, and located in advance of the middle. Surface ornamented by small, regular, con-
centric wrinkles, crossed by a few raised lines, or small, distant costae, which radiate from the back part of the
beaks to the posterior and postero-basal margins.

Length, about l.OG inch ; height, 0.47 inch ; breadth, 0.52 inch.

As far as can be determined from our imperfect specimens, this species seems to
be new. It bears some resemblance in form to P. subelongata, Meek (Trans. Albany
Institute, vol. IV, p. 42), from rocks of Cretaceous age on Vancouver's Island, but
its beaks are more depressed, and its radiating costre more distant, as well as more
obscure.

Locality and position.. — Lower part of the Jurassic beds at southwest base of
Black Hills. (Type No. 217.)

REPTI I.I AN AGE. JUR A S S I C PERIO D. 105

CLASS GASTEROPODA.

SUBCLASS PfI..M()NIFi:i: \

ORDER Inopcrculatn.

SUBORDER LIMXOP1UI. A

FAMILY LIMN^EIDJS.

Shell dextral or sinistral, thin, and born-colored, varying from elongate-
subeylindrieal to ovate or diseoidal; capable of receiving the entire ani-
mal when ivtrartnl : aperture simple; columclla with or without a fold;
lip sharp.

Animal with a short dilated muzzle; tentacles short and compressed,
or elongate and slender, bearing the sessile eyes at their inner bases.
Mantle with its margin simple or very rarely digitate. Mouth armed with a
corneous upper mandible; lingual teeth numerous, arranged in transverse
rows, the central minute and the lateral uncinate. Respiratory orifice
ou the right side, and the vent at the left of the neck. Foot ovate or
lanceolate.

The above diagnosis is framed so as to include three subordinate groups, present-
ing in their various species a wide range of forms, and more or less important
differences in the characters of the animal. These sections or subfamilies may be
characterized as follows: —

Shell spiral, dextral. Animal with tentacles short and flattened, or triangular.
Includes Limaaa, and probably CAi/ina aud Amphipeplea.

2. Phyainae.

Shell sinistral, otherwise mnch as in the Limnainte. Animal with tentacles elongate and slender.
Includes 1'hysa, Phytoptu, Aplexa, Afacropkyta,1 and Camptocertu.

3. Planorbiuac.

Shell involute, discoidal, dextral, or sinistral' f aperture more or less crescentio. Animal with tentacle*

as in the PHyiinee.
Includes Plaaorbu Tapkiut, Bathyompkaltu, Gyraulut, and Stymentina.

Notwithstanding the striking differences of form observed in the shells here
ranged under the sections of this family, the animals of these several types agree
in so many respects, that conchologists generally place them together in one family;
while some also include Aneylus, Acroloxus, Latia, and GrundlacJiia.

1 Macrophysa, Meek. The type for which this name is proposed is the curious Eocene species
described by Deshayes (Coq. FOBS. II, 90; X, 11 and 12) under the name Phyxa columnaris. It
is a remarkably elongated, subcylindrical shell, with a deep suture, and a comparatively very email
body whorl. Its aperture is oval and small, or less than one-third the entire length of the shell,
angular behind, and subangular or abruptly rounded in front ; columella smooth, flattened, and some*
what twisted. It seems to be intermediate between Camptoceras and Aplexa, and may possibly be
ranged as a subgenus under the latter.

• See note, p. 106.

14 December, 1864-

106 PALAEONTOLOGY OF THE UPPER MISSOURI.

In their habits, those moUusks all agree in being inhabitants of fresh water.
They are true air-breathers, being compelled to come to the surface occasionally for
that purpose. They are widely distributed in almost all parts of the world where
ponds, streams, and other bodies of fresh water exist, and feed upon conferva? and
other aquatic vegetation.

SUBFAMILY PLANORBIN^E (p. 104).
Genus PLANOKBIS, MULLER.

Synon.-Planorbis (part), MOLLBB, Verm. Terest. et Fluv. 1774, 152; Zool. Dan. 1776, 238.— Bnuo. Encyo. 1789, I,
xvi.— CCVIER, Tab. Elem. 1798 (not Planorbis, LAMARCK, Prodr. 1799, 76 ; nor 1801, Syst. An. 93).

Orbis, SCHROT. Jour. F. d. L. d. Ill, 1776, 10 (not LEA, 1833).

Vortex, HUMPHREY, Mua. Col. 1797 (58, sec. ed.).

Anisiu, FITZ. Verz. 1833, 111.

? Bathyomphalus, AGASSIZ, Cat'al. 1837, 20.

Hd'uoma, SWAINSON, Malac. 1840, 337.

Spirorbis, SWAINSON, ib. (not LAMARCK, 1815).

Planorbina, UALDEMAN, Fresh-water Univ. U. S. 1842, 14.

Planorbella, HALDEMAN, ib. 1842.

? Gi/raulus, AGASSIZ, Nouv. MSm. Soc. Helv. I, 1837.

Planodlscus, STEIN, * * * 1843.

t Taphius, H. & A. ADAMS, Genera Recent Mol. II, 1856, 264.

Menetus, H. & A. ADAMS, ib.
Ktym. — Planus, flat ; orbis, an orb.
Type. — Helix cornea, LINN.SDS.

Shell dextral, or sinistrall1 discoidal or subdiscoidal, the whorls being nearly or
quite on the same plane; right side generally flat, or sometimes either a little
elevated or concave ; left side more or less excavated ; volutions rounded, com-
pressed, or angular; aperture crescentic or suboval, sometimes dilated; peristome
thin, incomplete, right margin projecting.

The typical forms of this genus have the shell much depressed, and the volutions
numerous, rounded or without angles, and visible on both sides ; while the mouth
is not dilated. As above denned, however, it is made also to include several subor-
dinate groups which depart more or less from the typical species, though generally
placed here by conchologists. Some of these types should probably stand as distinct
genera, but as it is scarcely practicable, in Palaeontology at least, always to distin-
guish between them, we have preferred to define the genus in its widest sense.
The subordinate groups, however, not agreeing exactly with the typical forms, may
be characterized as follows: —

1. Planorbella, HALDEMAN.

Shell with few wliorls, which are usually angular on the left side ; aperture distinctly expanded, or bell-
shaped.
Type. — Planorbis campanulatus, SAT.

1 Conchologists generally regard these depressed shells as being dextral ; but 0. A. L. Morch
offers some apparently good reasons for viewing them as properly sinistral forms (Conch. Jour, xi.,
2d Ser. 235). This conclusion seems to be sustained by the form of the young of some American
species, one of which was described by DeKay as a truncated Physa. On the other hand, however,
monstrosities of some foreign species with an elevated spire, are generally dextral.

RE PTI LI AX AGE. J UR A SSI C PERIOD. 107

•2. llfli-om:t.

Shell vcntricoHe, concave on both sides ; volutions few, generally angular on one or both Bides, broadly

roiiM.i.-.l on the pfriplirry.
Ty/it. — I', bicarinalut, SAT.

3. Tupliius, II. & A. AnAM.t.

Shell ventrioose, somewhat irregular ; whorls rounded on the outer side, prominent or snbangular around
the rather small, deeply excavated umbilical cavity of the left aide. Aperture large, obovate, straight
will, in.

Tyfit.—l'. andecolut, D'Oanio.xT.

4. MrnrtiiH, II. & A. ADAMS.

Shell depressed, volutions increasing rapidly in size ; aperture snboval ; periphery more or less angular.
Example — /'. amjulatua, PUIL.

5. Antstis, FiTZiitaiB.

Shell strongly depressed ; volutions very numerous ; periphery angular.

/ c,im}'le. — /'. carinatut, MrLLER.

«. llatliyniupliiilus AOAS.XIZ. (= Spirorbit, SWAIKBOK, not LAHK.)

H i.-ll discoid, rounded on the periphery ; whorls numerous, closely nmbraoing on the left side, exposed on

the right ; aperture narrow, cresoentio ; umbilical cavity on the left side narrow and profound.
Type — Helix contorta, LlRKACS.

1. Gyraultis, AOABRIX. (= Nautilina, STBIH.)

Shell discoid, slightly convex on the right side, flat or broadly concave on the left ; volutions few, rapidly

increasing in size, obliquely depressed, bat not angular.
Example. — P. albui, MCLLEB.

So far as at present known, the genus Planorbis seems to have been first intro-
duced during the Liassic epoch ; it is also known to have been represented during
the deposition of the Wealden formation. Many species have likewise been found
in the fresh-water Tertiary deposits of various countries, though the genus seems
to attain its greatest development at the present time, and is widely distributed,
particularly in northern temperate regions.

Planorbis veternus.

(Put* IV, Fig. 1 and la, b.)
Ptanorbi* veternus, MEEK & HATDKX, Proceed. Aoad. Nat. Sol. Phila. Oct. I860, 418.

Shell small, planorbioular ; right side distinctly concave. Volutions three and a half to fonr, more or less
rounded, increasing rather rapidly in size ; slightly concave on the inner side for the reception of each succeeding
whorl, and prominent or snbangnlar a little within the middle on the npper side ; most convex outside of the
middle below. Concavity of left side rather large, basin-shaped, and, like that on the right, showing all the
whorls. Aperture oblique, a little oval. Surface nearly or quite smooth.

Greatest diameter, 0.15 inch ; do. of outer whorl, 0.05 inch.

Locality and position. — Southwest base of the Black Hills, associated with Unio
nucalix, Vir!ji<irn# Gi/ti, and Valvata? sedbrida; also, apparently, with AmmonHts
Henryi. As these fresh-water shells were found in loose fragments, we are not
sure they hold the same position as the Ammonite, though they were picked up at
the base of an outcrop of hard bluish-gray limestone, in masses agreeing in their
lithological characters with the bed containing the Ammonite. They may possibly
be Tertiary species, but differ from all those we have seen from rocks of that age in
the Northwest. It is only provisionally we place them along with the Jurassic
forms. (Type No. 317.)

108 PALAEONTOLOGY OF THE TJPPEE MISSOURI.

SUBCLASS PROSOBRANCHIATA.

ORDER Riphidoglossata.

SUBOKDER PODOPTHALMA.

FAMILY NERITWM.

Shell generally thick, varying from subovate or ovate-subglobose, to
depressed hemispherical, not umbilicate ; spire very small or sometimes
nearly obsolete, often lateral, simple within, from the absorption of the
inner whorls ; body volution very large ; aperture semilunar, not pearly
within.

Operculum wholly, or in part shelly, subspiral, articulated with the
inner lip by one or two processes.

Animal without lobes or neck lapets ; muzzle broad, short, and more
or less emarginate ; tentacles long, subulate, and having the eyes on pe-
duncles at their outer posterior bases. Foot oblong-subtrigonal ; margins
simple, not provided with filaments or membrane. Dentition much as in
the Trochidce (x.3, 1, 3.x), the rachidian tooth being very small, laterals
unequal, and the uncini numerous, with the first one large, and the
others very small, slender, and hooked.

This family embraces a large number of species, which have been variously
grouped into genera and subgenera by different authors. The groups most usually
adopted for the reception of the recent species are Nerita, Neritella, Clithon, Alina,
Neripterov, and Catillus. The extinct genera known at this time are Neridomus,
Velates, Deshayesia, Neritoma, and Pileolus. There are, however, probably several
undescribed genera amongst the fossil species referred to Nerita; and some of the
Carboniferous shells referred to McCoy's genus Naticopsis (though not the typical
species) seem to belong to some genus of this family rather than to the Naticidce.

Genus NERITELLA, HUMPHREY.

Synon. — Neritella, HUMPHREY, Mus. Col. 1797, 57.— GRAY, Zool. Proc. 1847, 148.— H. & A. ADAMS, Genera Recent
Mol. I, 18C-4, 380.

NerMna, LAMK. Phil. Zool. 1809; Hist. VI, 1822, 182.— BRONN, Leth. 1837,390 — PDSCH, Pol. Palaeont.
1837, 97.— SWAINSON, Malacol. 1840, 347.— RECLUZ, Revue Zool. 1841, 273, &c.

Theodoxus, MONTFORT, Coneh. Syst. II, 1810, 351.

Lamprostoma, RAFINESQDE, Anal. Nat. 1815 (not SWAINSON, 1840)

Nereina, DE CRIST, and JAN. Cat. 1832.

Clypeolum, RECLCZ, Revue Zool. 1842, 234.

Puperita, GRAY, Guide to the Syst. Dist. Mol. 1857, 137.
Elym. — Nerita dimin.
Type. — Nerita viridis, LIN.

Shell ovate, or rhombic subglobose, rather thin, covered with a corneous epider-
mis ; surface smooth or striate, and often ornamented with beautiful and vivid colors.
Spire short, more or less conoid. Aperture semilunar; inner lip and columella
straight and flattened or septiform, with a smooth or crenulated margin.

P. I'PTILIAN AGE. J UR A SSIC PE R I OD. 109

Operciilum thin, testaceous, with a corneous margin; outer surface smooth; pro-
vided with two apophyses ; the upper shorter, sometimes dilated and crested, the
lateral arcuate.

The Neritellas mainly inhabit fresh water, but they are often found in brackish,
and sometimes even in salt-water. Others arc amphibious, and crawl out upon the
roots and trunks of trees along the margins of streams, ponds, and other bodies of
\\ater. The genus embraces a considerable number of species which are widely
distributed, almost exclusively in tropical and torrid regions.

Conchologists differ in regard to the limits of this group, some including in it, as
sections or subgenera, Doslia, Alina, Ncripteron, and Clithon ; while others regard
not only these, but some of the others we have here included in the list of syno-
mms, as so many distinct genera.

The typical Neritellas differ from the closely allied groups Dosiia, Alina, and
yrrijitfi-oii, in being more symmetrical, less depressed shells, with a more developed
and less eccentric spire, as well as a greatly less expanded aperture, and a less
developed lip.

From ('lit/ion, with which they agree more nearly in form, they differ in never
being spinous, and always without a tooth near the upper part of the columella.
From the genus Nerita these shells may be distinguished by their much thinner
and smoother shells, and smooth or less strongly dentate columella, as well as by
the exclusively marine habits of the former.

It is difficult to arrive at a satisfactory conclusion in regard to the geological
range of this genus until the affinities of a number of fossil species have been more
accurately determined. It seems, however, to be an older type than Xrritn ; indeed,
as already intimated, even some Carboniferous forms usually placed in the genus
Xiiticopsis, are very closely similar to Neritella, though doubtless generically distinct.
Some of the so-called Neritas from European Jurassic beds probably belong to this
genus, though most of them present differences that place them either in the genus
NeridamuSi or apparently in allied, but undefined genera. If we are right in refer-
ring the bed from which the following described species was obtained, to the horizon
of the Jura, it would establish the existence of the genus during that epoch beyond
doubt, since it is a typical Neritella.

A few of the Cretaceous Neritas, so-called, seem also to belong here, and the
genus was well represented during the tertiary epoch. It attains its maximum
development, however, at the present time.

Neritella IVefora«*ccnsis.

Neritella Ncbratctntit, Mm & UATDEX, Proceed. Acad. Nat. Sci. Phila. Dec. 1861, 444.

Neritella ffebrateentii, Nttitella Xthraacentit.

Enlargement of bands of color.

Shell small, obliquely rhombic-oval ; volutions three to three and a half, convex, increasing rapidly in rise, the
last one composing more than nine-tenths of the entire shell ; suture well defined. Aperture broad ovate. Colu-

HO PALAEONTOLOGY OF THE UPPER MISSOURI.

mella moderately thickened and flattened, its margin a little arched and smooth ; usually having a slight
umbilical groove along the anterior outer margin of the inner lip. Surface smooth, or only having obscure
lines of growth ; ornamented with alternate dark and light-colored zigzag banda crossing the whorls at right

angles to the suture.

Height, 0.40 inch ; greatest transverse diameter, measuring from the outer side of the aperture obliquely upwards
to the most prominent part of the body whorl on the opposite side, 0.44 inch ; height of the aperture, 0.35 inch ;
breadth of do., 0.25 inch.

This must have been a very pretty little shell before its bands of color were partly
obliterated by the fossilizing process. A few of the specimens, however, still retain
these colored markings so as to be quite distinctly seen when moistened. We know
of no fossil species with which it is liable to be confounded. Amongst recent
species, it is perhaps most nearly represented by the European N. rivalis, Parrcyss,
which is of about the same size, and has much the same form and style of coloring,
though its aperture is rather less expanded, and its inner lip a little wider ; while
its bands of color are narrower, and not so abruptly nor so frequently deflected.

This species belongs to the subordinate group Neritina, as defined by H. & A.
Adams, and Chenu.

Locality and position. — Head of Wind River, Dakota Territory, where it occurs
associated with Lioplacodes veternus, M. & H., in beds supposed to be of Jurassic
age. (Type No. 1979.)

ORDER Cyclobraiichiatn.

? FAMILY DENTALIID^E.

Shell tubular, slightly arched, truncated and open at both ends ; aper-
ture at the smaller end sometimes with a slit or fissure on the dorsal side.

Operculum wanting.

Animal with lingual membrane comparatively broad ; teeth in three
series, the middle denticulate, and the laterals broad and simple. Head
rudimentary, being without eyes or tentacles ; mouth with cirrhated lips.
Mantle circular, thick and fleshy in front, and covering the forepart of
the body. Gills two, symmetrical, and placed behind the heart. Foot
conical, small, or rudimentary, with two symmetrical side-lobes, and an
attenuated hollow base connecting with the stomach, which is provided
with a strong internal "gizzard."

Although these curious mollusks are known to possess red blood like the earth-
worms, the rudimentary condition of their eyeless head, without traces of tentacles,
the position of their symmetrical gills, and the union of the sexes in each' individual,
are characters showing their low rank amongst the Gasteropoda. They are gene-
rally placed with the ProsobrancJiiata, though, as has been suggested by several
conchologists, they might with almost equal propriety be ranged with the Opistho-
branchiata.

This family includes only the genera Dentalium, Entails, and Helonyx.

K K I'TI LI A N AGE. J U R A SSI C P EHIO D.

Genus DKN I \ 1.1 I'M, LIN.

Synon. — Tultului, Drnlale, Dcxtalitet, Syringita, &o., of »ute-Linn«an authors.

Dentalium, LIXXMO*, 8yst. Nat. 1740, MO. ed. 64 ; ib. sixth ed. 1748, 75 ; ib. tenth ed. 1768, 786 ; ib. twelfth
r,l. 17i;s, l:ii;:j.— UJIK. 1'rodr. 1799,78; Syst. An. 1801,326; Hist. Nat. V, 1818. S41.— SOBOM. EM.
1-17. -liH.— BLAIKV. and Dw«. Diet. Sol. Nat. XIII, 1819, 69, 4o.
y-.'/V"'- — /'•'<«, a tooth.
t'.iamp. — I>rnt<tlium elr/ikantinum, Ll«.

Shell elongate, terete or angular, smooth, costate or striate; aperture circular;
lip simple, entire ; margin of the posterior opening without a fissure.

The shells of this genus are very similar to those of the allied group Entalis, but
the latter differ in having a slit or fissure in the dorsal side at the smaller extremity.
The genus fti/rtipa, one of the marine worms, also secretes a shelly tube, some-
times resembling that of /)> it/n/inm, though it can generally be distinguished
from the latter by having its sides more or less ventricose near the aperture, while
the >hell of Dentalium is gradually and regularly tapering from the larger to the
smaller extremity.

The genus I )i ,itii/!n>ti seems to have made its first appearance during the Devonian
epoch. It is also known to occur in the Carboniferous rocks, and ranges through
all the succeeding formations. It is well represented in the existing seas, and
probably attains its maximum development at the present time. The recent species
;m- usually found in deep seas, where they are said to feed upon Foraminifera
and small bivalves.

Dentnliiim Miibqundratiim.

Dentalium t lulniuadraium, MEEK, Proceed. Acad. Nat. Sol. July, 1860, 311.

Shell small, thin, regularly and slightly arcuate, very gradually tapering, flattened on four sides
so as to present a snbqnadrangnlar section, the angles being a little rounded; section of internal
cavity circular; surface apparently without longitudinal or transverse striae.

Length, about 1 inch ; diameter of larger end, O.OS inch ; do. of smaller end, 0.02 inch.

This species is remarkable for its quadrangular form, which give,s rise
to some doubts whether or not it is a true Dentalinm ; though we know
of no other genus to which it can be referred.

Locality and position. — North Platte River, at the Red Buttes, Lat.
42° 50' north, Long. 106° 40' west. (Type, No. 677.)

ORDER CteilobmiU'llhlta (= Pectinibranchiata).
SUBORDER ROSTRIFERA.

FAMILY VALVATID^E.

Shell small, turbinate or discoidal, provided with an epidermis; aper-
ture with an entire peritreme ; last volution sometimes free at the aperture.
Operculum corneous, circular, multispiral, the whorls being provided with
a thin elevated margin.

Animal with muzzle produced; tentacles cylindrical; eyes at their outer

112

PALAEONTOLOGY OF THE UPPER MISSOURI.

bases. Mantle simple in front; branchial plume pectinated, partially
exposed on the right side when the animal walks ; the laminae pinnate,
spirally twisted, protected by a respiratory lobe. Foot bifid anteriorly.
Lingual teeth (3. 1. 3) hooked and denticulate, the central series broad,
lateral lanceolate.

This family embraces but the typical genus Valvata, and Lyogyrm. The species
are rather widely distributed in temperate regions, and inhabit lakes, ponds, ditches,
and sluggish streams. They are the only known Prosobranchiate Gasteropods
having exposed gills.

Genus VALVATA, MTJLLER.

Synon.— Valvata, MCLLEB, Hist. Verm. II, 1774, 198 ; and Zool. Dan. Prodr. 1776, 239 ; STBDER, COXE Trav. Ill, 391 ;
ABILDGAABD, Skrivt. af Naturh.— SELSK. 1794, III, 61 ; DBAPABN. Tabl. 1801, 30 ; and Hist. 1805, 26,
28, 41 ; LAMK. Extr. d'un Cours. 1812, and Hist. VI, 1822, II, 171.

Valvearius, DDM. Zool. Anal. 1806, 164.

Gyrorbis, FITZINGEB, Verz. 1833, 117.

Planella, SCHLUT, Vz. 1838, 13.

Valvata, BEBOE, Conch. Bnch, 1847, 17, 20, 26.

Tropidina, H. & A. ADAMS, Genera Recent Mol. 1856, 344.
Etym. — Valvatus, having folds or valves.
Type. — Valvata cristata, MCLLEB.

SheU umbilicate; spire usually much depressed, sometimes moderately prominent;
whorls rounded or carinate; epidermis corneous; aperture circular; lip thin and
sharp.

The shells of this genus are distinguished from those of the allied type Lyogyrus
by never having the last turn free at the aperture. The group embraces two rather
marked sections, as follows: —

1. Valvata (proper) = Gyrorbis, FITZINOER, = Planella, SCHLUT.

Shell greatly depressed or planorbicular ; with a very wide umbilicus and rounded whorls.
Example. — V. cristata, MULLEK.

3. Tropidina, H. & A. ADAMS.

Shell turbinate, or having the spire more or less prominent, and the volutions either carinate oj rounded.
Examples. — V. tricarinata, SAY, and V. piscinalis, MULLEK.

As there are some slight differences in the details of the lingual teeth in these
two groups, as well as in the form of the shell, it is possible they may more pro-
perly constitute distinct genera.

The Messrs. H. & A. Adams admit three subgenera under this genus, in their
valuable work on the genera of Recent Mollusca. Regarding such forms as V.
piscinalis as typical, they adopt Fitzinger's name Gyrorbis, for such types as V.
cristata, Miiller, and propose the name Tropidina for forms like V. tricarinata, Say.
As the genus Valvata, however, was originaUy founded by Miiller, upon V. cristata,
that species must be regarded as the type, and as Gyrorbis was also founded upon
the same shell it must be viewed as exactly synonymous with Valvata proper, and
cannot be used for another group. Although Tropidina was proposed for the recep-
tion of carinated forms only, there is no reason why it should not also include the
other turbinate species, with rounded whorls, and a more or less prominent spire,
since the carinated character is not constant even in the species tricarinata.

REPTILIAN AGE. JURASSIC PERIOD. H3

If the following des( ribcd species really belongs to this genus, it would seem to
establish tlie existence ol' tlie group during the deposit ion of tlie middle or older
members of the June-ir M-inn. This conclusion, IK. \ve\er, should not be adopted
until all doubts are removed in regard to its generic characters, and exact strati-
graphical position. Tlie existence of this genus during the "Wealdcn period is,
however, well established. It is also well represented in the fresh-water Tertiary
deposits of Europe and occurs in the Tertiary beds of the central districts of North
America, and probably attains its greatest development at the present time.

Subgenus TROPIDINA, H. & A. ADAMS (p. 112).
Yalvata? scabrida.

(Pun IV, Fig. 2, a, &.)
Valvatat icabrida, MEEK & HAYDEX, Proceed. Acid. Nat. Sol. Phila. Oct. .860, 418.

Shell small, subglobose, thin ; spire rather depressed. Volutions three to three and a half, increasing rapidly in
pi/-, very convex ; subangular around the upper outer aide, and horizontally flattened between the angle and the
snturn; vmtrifoe on the outer and under sides. Suture well defined; aperture round, oval? Surface ornamented
by strong, regular marks of growth.

Length and breadth, each about 0.16 inch.

Not having seen specimens of this little shell sufficiently detached from the very
hard, brittle, argillo-calcarcous matrix, to show very satisfactorily the form of its
aperture, we are left in some doubt respecting its generic relations. From its
general appearance, however, taken hi connection with the fact that a few other
fresh-water shells occur in the same bed, we are led to regard it as most probably a
r< it rota, though it may possibly be a Viviparus, or belong to some marine genus.
Its principal distinguishing characters are the small number and ventricose form of
its whorls, and strongly defined marks of growth.

Lo<-n Hi ;i and position. — Near southwest base Black Hills, where it was found hi
loose fragments of a hard bluish-gray argillo-calcareous rock, associated with Plan-
orbis retermi* and Unio nucalis. These masses were found at the base of an outcrop
of very similar rock, containing Ammonites Henryi, and seem to belong to the same
formation. The fresh-water species may be Tertiary, though we think they and the
Ammonite, with which they appear to be associated, arc probably of Jurassic ages.
(Type, 316.)

FAMILY VIVIPARID^E.

Shell varying from subglobose to turbinate, or conical subovate ; rather
thin, or more or leas thickened, covered with an epidermis; surface
smooth, spirally striate, or with revolving, rarely nodose, carina» ; aper-
ture oval or subcircular, simple, and rounded anteriorly ; peritreme con-
tinuous, simple.

Operculum annular, or rarely with a subspiral nucleus.

Animal retractile within the shell ; foot moderate, and adapted for
crawling only; rostrum moderate, nearly or quite entire at the extremity;
tentacles tapering, retractile, and having the eyes on short tubercular

16 January, 1865.

114 PALAEONTOLOGY OF THE UPPER MISSOURI.

prominences at their outer bases. Gills internal, comb-like, single.
Tongue short; lingual teeth in seven longitudinal rows (3. 1. 3), lateral,
more or less curved, truncated and serrate, or pointed and claw-shaped
at the extremity. Generative organs unisexual ; in the male, included
in the right tentacle ; in the female, under the margin of the mantle on
the same side. Female ovo-viviparous.

The following groups are included in this family, viz. : Viviparus, Tulotoma,
Campeloma (or Melantlio of authors; not Bowdich), Lioplax, and Lioplacodes. The
groups Larina, Paludomus, Bithynia, Bithynella, Ganga, Tanalia, PJiilopotamis,
and Rivulina have also been placed here by some authors, but the labors of Prof.
Gill and Dr. Stimpson have shown that all these should be eliminated, thus leaving
the Viviparidce probably a strictly ovo-viviparous group.

GENUS VIVIPARUS, MONTFORT.

Synon. — Vivipare, LAMARCK, Phil. Zool. 1809, ii. 320 (without example, diagnosis, or figure); and again, in the

same way, Extr. d'un Cours. 1812.
Viviparus, MONTFORT, Syst. 1810, ii. 247. — GRAY (in part), Proceed. Zool. Soc. 1847, part xv. 155; and

again, Guide to Syst. Distr. Moll. Brit. Mus. 1857, i. 112; GILL, Proo. Aoad. Nat. Sci. Phila. 1863, 37.
Henterum, HDBN. Epist. I. 1810.

Paludina, LAMARCK, Extr. d'un cours. 1812 * * * ; and Hist. 1822, vi. 172. — SCHWEIGQ. (part) Natnrg.
1820, 736.— BLAINVILLR (part), Diet. Sci. Nat. 1824, xxxii. 320; and 1825, xxxvii. 300.— DESHAYES
(part), Encyc. Meth. 1832, iii. 689, and of various later authors.
Vivipara, SOWERBY, Mineral Conchology, 1813, tab. 31. — H. & A. ADAMS (part), Genera Recent Moll. 1854

i. 38.

Etym. — Vivus, alive ; pario, to bear or bring forth young.
Type. — Htlix vivipara, LINN.

Shell ovate or conic-subovate, thin, usually with a small umbilical perforation ;
volutions rounded or more or less flattened; surface smooth or with revolving lines
or carinae; epidermis olivaceous, often with revolving bands of color; aperture
more or less regularly ovate; outer lip thin, straight in outline, and continuous on
a plane with the inner.

Operculum corneous, entirely annular.

Animal with lateral teeth of the lingual ribbon oblong, arched, somewhat pointed
below, truncated and serrate above; median tooth shorter, curved, more or less
rounded, and serrate above; the middle denticle being larger than the others.

These mollusks inhabit rivers, lakes, and other bodies of fresh water, and are
widely distributed in the Northern hemisphere. This genus is related to Campeloma,
Lioplax, and Tulotoma, which have, indeed, until recently, been included in it, either
as subgenera or otherwise, by most authors. It may be distinguished from the
former two groups, however, by its thinner shell, and by its outer lip being straight
in outline and continuous on a plane with the inner, instead of being inversely
sigmoid. A more important difference, however, is in the lingual teeth, which, in
Campeloma and Lioplax, have the upper margins smooth, or only very minutely
serrated, while the outer two on each side are pointed and claw-shaped, instead of
truncated above. Lioplax is also distinguished by a subspiral opercular nucleus.

i: I I'll I.I A N A(iK. JURASSIC PERIOD. H5

From Tiili'ii'iiKt these sin 11s arc distinguished by being thinner and not nodular;
while the animal of the latter genus is said to ha\e more the habits of Anculosa,
being found clinging to stones in running water instead of crawling upon the muddy
bottoms of slui^i-h streams and lakes.

This ijeiiiis is believed to date hack as far as the Jurassic epoch. It also occurs
in the \\ ealdni deposits, and was well represented during the deposition of all the
members of the Tertiary system, at which time the species seem to have been quite
as numerous as at present, if not even more so. We already know some six or
seven species from the Lignite Tertiary beds of the Upper Missouri and Rocky
Mountain regions.

Viviparns l.illi.

(Pt*T» V, Fig. 3, a, 4.)

Shell small, ovate-snbglobose ; volutions about four and a half, increasing rather rapidly In ilie, ventrioote,
rounded, last one larger than all the others ; suture deep and well defined, tn consequence of the convexity of the
whorls ; umbilical chink very small or closed ; aperture oval, slightly oblique, and nearly equally rounded above
and li.-l.iw, there being but a very slight angularity at the Inner side above ; perltreme distinctly continuous in
adult sh.-lls; surface only marked by small, rather obscnre lines of growth.

Length of the largest specimen seen, 0.47 Inch ; breadth, 0.42 inch.

'I'h is seems to be a rather rare species, only three specimens having been found,
and none of these are entire. It is most nearly allied to the common recent
American species ]V*-/y«i/v;.s lineatus, Valenc., but is much smaller, and differs
in having its aperture more nearly equally rounded above and below. There can
be no question about its being a typical Vivqxirus.

We take pleasure in dedicating this oldest known American species to our friend
Prof. Theo. Gill, of Washington City, who first pointed out the true distinguishing
characters between this and the allied group Campeloma, Ilaf. (= Melant/io of
authors).

Locality and position. — Same as last, where it occurs associated with Neritella
Nebrascensis and Lioplacodcs veternus. (Type No. 4035.)

Genus LIOPLACODES, MEEK.

Synon.— 3fela*ia (sp.), MEEK & HAYDEX, Proceed. Acad. Nat. Soi. Phila. Deo. 1861, p. 444.

Lioplacoda, HBKK, Smithsonian Check List, Jurassic fossils, 1864, 29 and 40.
Klym. — Lioplax.
Typt. — Mclania (Potadoma) velerna, MEEK & HATDES.

Shell conoid-subovate, rather thick, scarcely perforate; spire prominent; aper-
ture obliquely subovate, rather obtusely angular behind, and somewhat narrowly
rounded and faintly sinuous in front; peritreme continuous; outer lip inversely
sigmoid ; surface with revolving lines.

Animal and operculum unknown.

The shell for the reception of which this genus has been proposed is one of those
forms presenting an intermediate appearance between the Melaniidce and I'/V/'/.r//-/././ ,
so perplexing where we can know nothing in regard to the nature of the animal or
operculum. Its comparatively slender subconical form, and the slight flattening

116 PALAEONTOLOGY OF THE UPPER MISSOURI.

of the upper oblique slope of the whorls, together with its revolving lines, give it
much the appearance of some types of the Melaniidce ; while its small but unmis-
takable umbilical pit, and continuous peritreme, together with the expression of
the aperture, indicate nearer affinities to the Viviparidm. It is perhaps most nearly
allied to the genus Liaplax of Troschel, but differs from the type of that genus
(Paludina sulcarinata, Say) in having a much less ventricose and proportionally
smaller body whorl, more attenuate spire, and numerous thread-like revolving lines,
instead of a single carina ; while the posterior extremity of its aperture is suban-
gular instead of rounded, in consequence of the oblique flattening of the upper part
of the body volution.

Lioplacodes Yeternus.

Melania (Potadoma) veterna, MEEK & HAYDEN, Proceed. Acad. Nat. Sci. Phila. Deo. 1861, p. 444.
Lioplacodes veternus, MEEK, Smithsonian Check List, Jurassic fossils, 1864, 29.

Shell with spire elevated ; volutions about six, very convex, rounded at the middle, and often obliquely a little
flattened above ; suture deep ; aperture obliquely oval, subangular behind, and rather narrowly rounded and faintly
sinuous in front, much more prominent or convex on the outer than the inner side ;
inner lip disconnected from the coluinella, so as to leave a small umbilical chink ;
outer lip broadly sinuous in outline near the middle of the aperture or slightly above,
and most prominent below. Surface marked by strong flexuous striae of growth, which
are crossed by more or less distinct thread-like revolving lines, some four or five of
which, near the middle of the body whorl, are larger aud more widely separated than
those below.
Lioplacodes veternus. Length, 0.77 inch ; breadth, 0.50 inch ; apical angle convex, divergence about 47°.

This interesting species was at first placed by us, with considerable doubt, in the
genus Melania, as that group was then understood by most conchologists. The
necessity for restricting that name, however, to such forms as M. amarula, has
become more apparent from late investigations, while the various recent American
species resembling our shell have been distributed into several genera, In endea-
voring to determine to which of these our species is most nearly allied, by clearing
away the matrix with care from about the aperture, it has been found, quite unex-
pectedly, to present characters, as already stated, showing affinities to the Vivipa-
ridre, rather than to the Melaniidce. And yet it differs from the known genera of
that family to such an extent that it has been thought desirable to regard it as the
type of a new genus.

Locality and position. — Head of Wind River, Dakota Territory, from beds referred
provisionally to the Jurassic system. Associated with Neritella Nebrascensis. (No.
1978.)

CLASS CEPHALOPODA.
ORDER Tetrabrauchiata.

FAMILY AMMONITE) J3.

Shell involute, spiral, variously curved, or straight; outer or last cham-
ber large. Aperture varying in form with the genera and species ; lip
often more or less produced on the outer or dorsal side, sometimes hooded,

KHPTILIA.N AGE. JURASSIC PERIOD. H7

or provided with later*] appendages. Septa moretir less deeply lobed

on tin1 nianrins: present inir a convex outline (in their mesial section) on
the side facing the aperture; lobes variously plicated or sinuous and
dentate or merely seriated <m the margins. Siphon dorsal, with relation
to the shell, cylindrical, slender, never occupied by an internal organic
deposit, piercinir the septa from within outwards, or towards the aper-
ture; envelop solid and persistent.

Animal unknown, all the genera of the entire group being extinct.

This family is nearly related to the Goniatitulcn, through the intermediate Ceratites.
Indeed, previous to the researches of the distinguished palaeontologist Barrande, the
Goniatitcs were by most authors, along with the Ceratites, included in the family
AhiiiKni'it'nlir ; and some even included these three genera under the single generic
name Aunimniti-x. M. Barrande, however, has shown (Bui. Geol. Soc. Fr. 2,
ser. t. xiii, p. 375, 1856) that the G<mi<itite. group differs from the true Atumo-
iii / ill a. not only in the greater simplicity of their septa, but also in having the
neck or gullet of the siphon always projecting backwards, as in the JSW//Y/V/"-,
instead of forwards, or towards the aperture, as in the Ammonitidce. Again, he
linds that a mesial section of their septa shows a concave, instead of a convex,
outline on the side facing the aperture; while their si phonal envelop is not solid
and persistent, as is usually the case with Ammonitidce.

From these facts some authors have gone to the opposite extreme, and included
the (iniiiiitUfi group in the Nautilidce. M. Barrande, however, has shown, in the
paper above cited, that at the same time that they agree with the latter family in
these several characters, they still differ in some important elements of structure.
In the first place, they always differ in having the septa provided with a dorsal lobe,
and generally in having their septa more lobed or sinuous on the sides. Another
important difference is the entire absence of the peculiar organic deposit within the
siphon, such as we sometimes see in extinct forms of the Nautilidce. Again, they
differ in having the siphon invariably on the outer side, instead of varying in its
position between the dorsal and ventral margins. Hence we arc inclined to agree
with M. Barrande in separating these cephalopods into the three distinct families,
Nautilidce, Goniatitidce, and Ammonitidce.

It is an interesting fact that, even after excluding the Goniatite group from the
family Ammonitidce, we still have a very extensive and varied group of shells,
amongst which we observe a representative, so far as form is concerned, of nearly
every genus, not only of the NaittUidte, but also of the apparently distinct Ortho-
ceras group. This fact would seem to argue, either that the Nautilus and Ortho-
ceras groups should not be separated, or that there may be genera belonging to
more than one family included in the Ammonitidce, even as here defined. Still,
notwithstanding the great differences of form observed amongst these fossils, they
agree so very nearly in their internal structure, that it seems difficult, in the present
state of our knowledge, to point out constant characters by which they can be
divided into distinct families, or even well-defined subfamilies.

When we take into consideration the infinite diversity of beautiful forms pre-

118 PALAEONTOLOGY OF THE UPPER MISSOURI.

sented by the shells of these mollusks, their great numbers, and often elaborately
ornamented surface, and remember the large sizes to which they sometimes attained,
it is easy to understand that they must have constituted a marked and peculiar
feature of the molluscan fauna of the Jurassic and Cretaceous seas.

It not unfrequently happens, where the substance of the shell is well preserved,
that in breaking specimens from the rocky matrix in which they are enveloped,
the outer porcellaneous layer exfoliates, leaving the elegantly sculptured surface of
the fossil covered with the brilliantly iridescent inner pearly layer, in which condi-
tion they form exceedingly beautiful cabinet specimens. It is necessary, however,
to remove this inner layer also, when we wish to study the complex internal struc-
ture of the shell, which furnishes important characters for the distinction of species
and sometimes of genera.

The following are the genera we would at present include in this family, viz :
Baculina, Bctculites, Ptychoceras, Hamulina, Samites, Toxoceras, Crioceras, Ancylo-
ceras,1 Scaphites, Ceratites, Ammonites, Anisoceras, Helicoceras, Heteroceras, and
Turrilites. It seems to be impossible, however, by a linear arrangement, to place
these groups so as always to bring together those most nearly allied.

REMARKS ON THE SO-CALLED GENUS TRIGONELLITES, OF PARKINSON, 1811.

Aptychus, METER, 1831. — Jchthyosyayon, BOURDET, 1822. — Munsteria, DESLOSOCHAMPS, 1835.

A consideration of the family Ammonitidce would scarcely be complete without
some allusion to those curious bodies generally known by the names TrigoneUites,
Aptychiis, &c., so often found within, or associated with, the shells of the typical genus.
Few objects amongst all the relics of extinct life have been more puzzling to the
palaeontologist, or given rise to a greater diversity of opinions than these. Most of
the early palaeontologists regarded them as the shells of bivalve mollusks, as did
Parkinson, Deslongchamps, and some later investigators ; while others supposed
them to be the palatal bones of fishes. Others, again, maintained that they are the
internal osselets of some extinct cephalopod allied to Teudopsis ; and still others,
that they are an internal organ of Ammonites, analogous to that connected with
the digestive apparatus of Bulla and some other Gasteropoda. Burmeister sup-
posed them to be external supplementary shell pieces of Ammonites, designed for
the protection of the branchial sack when the animal was partly protruded from
the shell. More recently, D'Orbigny, Pictet, and some others have advocated, with
much ingenuity, an opinion first suggested by Scheuchzer, that they are the valves
of pedunculated Cirripedes allied to Anatifa.

The impression, however, has for some time been gaining ground amongst pala>
ontologists that these bodies really are organs or appendages of* the Cephalopods,
with the shells of which they are so frequently found associated. And since Darwin

1 It is possible the genus Ancyloceras may be synonymous with Crioceras, since the species for which
the latter genus was proposed have never, we believe, been found entire ; and it yet remains to be
clearly demonstrated that Ancyloceras was not founded upon perfect specimens of the same type. If
so, the name Crioceras will take precedence, because it was published in 1836, and Ancyloceras in 1842.

i: I- I'll I.I AN AGE. JURASSIC PERIOD. H9

has «.hown that it is against all analog)- to regard them as the valves of Cirripedea,1

tin- st yeuerally received opinion is that they are the opercula of Ammonites,

Sea|ihit( 's. ( ioniatit. •-. \< . This opinion would a bo seem to receive considerable
weight t'roiii the di-coxery. in tew rare instances, of an Ammonite with a Trigo-
nellite closing :ind apparently exactly h'tting its aperture.8

lie ton- bringing forward soiui- re:i>ons. ho\ve\er. for doubting the correctness of
this conclusion. Miggested liy a reinarkahle Trigonellitc found in a Scaphite from the
Cretaceous rocks of the t'pper Missouri country, the following description of this
provisional genus is neces-.-iry for a clear understanding of the subject: —

\- usually found, these bodies consist of one or two (most frequently two) ovoid or
sulttriijnnul plates or valves, with one extremity truncated and generally wider than
the other, and one side nearly or quite straight; while the outer or lower surface is a
little convex, and the inner concave. Unless displaced or separated by some accidental
cause, the two pieces always occur with the straight edges joined
together in such a manner as to indicate that they were originally r(e' L

held together in some way. The normal position of the two
pieces seems to be like that of the valves of a bivalve shell partly
open ; but when they are opened out and flattened by pressure,
as is often the case, they frequently present the bilobate appear-
ance seen in the annexed cut, Fig. 1. In structure, composition,
and thickness they present differences, in consequence of which
the group has been divided into the three following sections : —

1. The CKLLCLOSI, which are thicker than those of either of the other sections, and consist first of a thin, concentri-

cally striated inner layer, over which there is a thick calcareous portion, composed of numerous polygonal
tubes arranged with their longer axes at right angles to the outer and inner surfaces of the valves. OnUide
of this there is a thin calcareous layer, the smooth surface of which is usually perforated by small pore*.

2. The IMBRICATI, with an inner layer like the preceding, and a middle porous stratum, the tubes of which am

smaller and less distinctly defined. Its onter layer also diners In being a true calcareous shell, with
distinct plications, and a smooth punctate surface, the pnnctte of which are arranged in regular lines.

3. The COBNRI, which are said to consist of a single very thin corneous lamina, destitute of any porous or tubular

layer.

Our Upper Missouri specimen, already alluded to, is very thin, and seems to be
composed of a single lamina showing no cellular structure, and may consist only of
the inner layer. It occurs in the outer chamber of a Scaphite* C/icyentieiisie, and is
the only organic body found in it, the surrounding space being filled with the fine
indurated sedimentary matter, similar to that in which the Scaphite was originally
enveloped. It occupies a position apparently about one-fourth of the distance back
from the aperture to the first septum, and lies with the two valves partly open, and
apparently in their natural position with relation to each other, their straight edges
being joined together, and deflected upwards so as to form a distinct carina, which

' The reason offered by Mr. Darwin for rejecting the conclusion that these bodies are the valves
of a Cirripede is, that they are nearly always found with the straight edges of the two valves or
pieces in contact, so as to show that they mast have been anchylosed or held together by a membrane
or kind of ligament along these margins, which would have been impossible if they were the valves
of a Cirripede, since that is the very side where the feet would have to pass ont

• They have been found associated with (Joniatites in Devonian rocks.

1 See an example published by Mr. Woodward in the Geologist, vol. Ill, 1860, p. 338.

120

PALAEONTOLOGY OF THE UPPER MISSOURI.

comes in contact with the so-called dorsal (properly ventral) side of the Scaphite;
while the truncated ends of the valves (Fig. 1, a, a, which represents the valves of
this specimen as it would appear if opened and flattened out) are directed forward
towards the aperture.

The fact, however, to which we would call especial attention, is the occurrence of
a third piece or appendage, differing entirely in form from either of the two valves
already noticed, and, so far as we know, from anything hitherto found in connection
with any of these fossils. This third piece occupies a position between the two
valves as they lie together, partly opened; being nearer the extremity directed
towards the aperture of the shell, and exactly fitting between the valves, as if in its
normal position with relation to them. It is thin, and agrees so exactly, in color,
texture, and surface markings, with the two valves enveloping it, that it is impos-
sible to examine the specimen for a moment and entertain a doubt in regard to all
three of these pieces being parts of the same fossil.

The appendage to which we allude differs entirely from the usual form of a Tri-
gonellite or Aptychus, as generally understood, and presents a very peculiar jaw-like
appearance. It consists of a single piece, with two thin rami or lateral expansions
extending backwards so as to present, when viewed on either side, the outline and

Fig. 2.

Fig. 3.

Fig. 4.

appearance of the annexed cut, Fig. 4 ; while Fig. 3 represents its upper side. Its
two lateral expansions, however (a, a of Fig. 3, and c of Fig. 4), have their upper
margins inflected so as to appear, as seen from above, to be thicker than they really
are. The position of this third piece between the two valves will be understood by
reference to Fig. 2, the right end of the figure being that directed towards the aper-
ture of the shell, and the lower or straight side being in contact with the so-called
dorsal side of the same.

The presence of this third part or appendage would seem to furnish another
strong argument, if any were necessary, against the conclusion that these fossils are
the valves of Cirripedes, since its form is such that it can scarcely be regarded as
homologous with any of the external plates of those animals. Its form, if not
indeed its very existence, seems, we think, even more irreconcilable with the rather
generally accepted opinion that they are opercula. We can readily understand
how the two valves might be opened out and attached to a fleshy lobe, or some of
the softer parts of the animal, so as to perform the offices of an operculum ; but it
seems impossible to conceive how this third jaw-like piece, which is manifestly a
part of the same fossil, could be in any way connected with such an organ. In
addition to this, it may be added that many Ammonites are known to have the
aperture at maturity so remarkably contracted or modified by the development of
lateral appendages of the lip, that it appears almost impossible that they could have
been provided with an operculum.

P, K I'll I.I A \ AGE. JURASSIC PERIOD.

In examining the curious third appendage described nlxive, one can scarcely fail
t<> !><• impressed with it- resemblance to a jaw or beak. Indeed, so striking is this
analog, that we are strongly inclined to udopt that conclusion, notwithstanding the
fact that we nm>t then \ iew the tuo' en\eloping valves as forming together one of
the opposing inandililes. The opinion that these bodies may be jaws instead of
opercnia— first suggested by Van Breda, if we mistake not — receives additional
support from the entire absence, so far as known, of anything else representing jaws
or beaks, within the thousands of Ammonites that have been broken open in various
parts of the world; while all the existing Cephalopoda are known to be provided
with such oral organs. Again it will be remembered, that in the living Naitfiliix
(the beaks of which are partly calcareous, and partly corneous), the upper mandible
i- received within, and enveloped by, the lower, much a8 the appendage we have
described lies between the valves in our specimen.

Genus AMMONITES, BRUGUIERE.

Synon.— Ammonite*, BBCOCIF.BB, Encyo. Meth. I, 1789, zvl and 28.— LAMABCK, Prodr. 1799, 80; Syst. Ann. 1801,
100; Phil. Zool. IsO'.l, 323.— FBBCM. Tab. Sygt. 1819.— ROIBST, Mol. V, 1805, 16, Ac.

Ptanulite*, Ifontfort, Conch. Sygt. I, 1808, 78 ; (not LAME. 1801 ? ; nor MCJCSTBB, 1832.)

ElliptolHku, Montf. ib. 86.

Aryonaula, KKIMO KB, Mar. proto. Naut. 1818, * * * (not I.ix.)-

Ammouiin, ORAY, Lou.l. Med. Rep. 1821.— FLEMIXO, Brit. Ann. 1828, 240.
Elym. — Amman, a name of Jupiter.
Kxamp. — Ammonite* bitulcatut, BucociEBB.

Shell discoidal or more or less convex, sometimes subglobose. Volutions contigu-
ous or embracing at all stages of growth, and coiled in the same plane ; umbilicus
varying greatly in breadth and depth with the species. Surface costate, nodose,
subspinous, striate, or smooth. Lip simple, inflected, or with various lateral ap-
pendages. Lobes and saddles of the septa more or less branched and deeply
divided ; the margins of the subdivisions sinuous and dentate.

In form, the dorsal position of the siphon, and often in ornamentation, the Am-
monites present scarcely any difference from the Ceratites and Goniatitcs. Tiny
ditt'er from the latter, however, in having the lobes and saddles of the septa divided
and variously branched or dentate, instead of simple. From the former they often
present but slight and scarcely perceptible differences, even in the septa, the lobes
of which only differ in being more or less deeply divided and branching, instead of
merely serrated on their margins. There arc, however, some intermediate species
connecting these groups, so that even palaeontologists do not always agree in regard
to their position.

The Ammonites are also related to the genus &-<ijihit>«, from which they only
differ in not having the last or body whorl of the adult shell deflected from the

1 It is worthy of note in this connection, that M. Coqnand has maintained that an Aptychus (as
hitherto understood) properly consists of a single piece — that the apparent existence of two distinct
valves, is produced by the fracture of a single flexed plate, along a mesial line of least resistance,
from accidental pressure.

1U January, 1865.

PALAEONTOLOGY OP THE UPPER MISSOURI.

regular curve of the inner turns, and the aperture again turned back towards the
body of the shell. In the position of the siphon, the structure of the septa, and in
ornamentation, there is no difference between these groups ; and it was probably
only at maturity that the shell of a Scaphite differed from that of an Ammonite,
while in some species this difference is very slightly marked.

The genus Ammonites, as here defined, was introduced at near the close of the
Triassic epoch, though several authors improperly refer to it some of older Goniatites.1
It is very numerously represented through the Jurassic and Cretaceous series, some
eight hundred or more species having been already described from these rocks. As
might be expected, the species of so large a group present great diversities of form
and ornamentation, and various attempts have been made to group them into sec-
tions or subgenera, without any great degree of success. When we observe the
remarkable differences, however, presented by the form of* the aperture, and the
labial appendages gf some of the species when found entire, we are led to suspect
that we may some time be able to separate them into several natural groups, either
having the rank of genera or subgenera. We have no authentic evidence of the
existence of this genus after the close of the Cretaceous epoch.

/

Ammonites cordiformis.

(PLATE V, Fig. 2, a, b, c, d, e.)

Ammonites cordlformis, MEEK & HATDEN, Proceed. Acad. Nat. Sci. Phila. March, 1858, 57 ; ib. Oct. 1860, 418.
Comp. A, cordatus, SOWERBY, Min. Cou. vol. I, 1812, 51, 17, figs. 2-4; also D'OBBIGSY, Pal. France I, pi. 193 ; Geol.
Russia, pi. 34, figs. 1-5.

Shell lenticular, adult specimens being much more convex than the young ; umbilicus rather small, or from
one-third to one-halt the breadth of the outer whorl; dorsum carinate; volutions increasing so as to more than
double their diameter every turn, each of the inner ones from one-half to three-fourths hidden within the ventral
groove of the succeeding whorl. Surface ornamented by numerous small flexuous costsfi, which, in crossing the
sides, increase by division and intercalation so as to number two or three times as many at the periphery as
around the umbilicus. In approaching the dorsum, they curve forward, and all cross the dorsal carina, to which,
in young specimens, they impart a distinctly crenate outline.

Greatest diameter of a specimen divested of its outer whorls, 3.30 inches ; diameter of its last turn, from
umbilicus to dorsum, 1.63 inch ; breadth of same, 1.46 inch.

The septa are not very closely crowded, and have each five lobes on either side,
none of which are deeply divided, or very complex in their details. The dorsal lobe
is a little wider than long, and has two principal branches on either side, the two
terminal of which are slightly larger than the others, and each provided with seven
or eight unequal digitations. The dorsal saddle is about the size of the superior
lateral lobe, contracted in the middle, and divided at the extremity into some four
or five short, unequal, sinuous, and digitate branches. The superior lateral lobe is
as long as the dorsal lobe, but narrower, conical in form, and ornamented with three
or four lateral branches on the dorsal side, and two or three smaller ones on the
ventral side ; while its terminal branch is bipartite, and its margins, as well as those
of all the other principal divisions, are more or less sinuous and digitate. The
lateral saddle is smaller than the superior lateral lobe, and has on each side three
or four very short, obtuse subdivisions, with sinuous margins. The inferior lateral

1 The species in the Upper Trias have more simple septa, and often closely approach the genus
Ceraliles in this respect.

K I! PTILI AN AOE. JURASSIC Pi: III OD 123

lobe is smaller than the lateral saddle, and divided at the extremity into two nearly
equal, rather >hort hraiu lie->, each of which is Millions, and shows a disposition to
give oil' short subdivisions on the outer side. Tin- remaining lobes are very small,
and obtusely digitate, the inner one showing a tendency to bifurcate.

This Npecies varies considerably in form, as well as in its surface markings, at
different ages; young specimens bring much more compressed, more sharply cari-
nate on the dorsum, and having a proportionally wider and more shallow umbilicus
than the adult. Their coM;e arc also more flexuous and more sharply elevated than
those of mature shells. On medium-sized specimens the costae that pass entirely
across the sides sometimes swell a little near the umbilicus, so as to form \ei\
obscure, tran-«\ er-ely elongated, subnodose prominences; while on large specimens
all the coNta- are nearly or quite obsolete.

If Aiiiiii<>iiiti-f< mi-ifntii*, of iSowerby, varies as much as it would seem to do from
the ti^mes of it given by D'Orhigny in the Palaeontology of Fjance, and in Mur-
chison, De Vernenil, and Keyserling's work on the Geology of Russia, our shell
m:i\ prove to belong to that species. In form and external ornaments it is almost
exactly like some varieties of A. cordutus, yet it presents rather marked differences
in its septa from any of the figures of that species we have seen; not greater,
however, than we see between the septa of supposed individuals of that extremely
variable form, represented by D'Orbigny in the Pal. France, and in the Geol. Russia.
Although later comparisons have nearly satisfied us that our shell is not distinct
from Sowerby's species, we have concluded to retain our name, cordiformis, until
its identity or difference can be determined by the comparison of a better series of
specimens.

Lot-ill if i i < i a, I /Haitian. — Southwest base of the Black Hills, associated with Belcm-
///'/•« densus, Eumicrolia curta, and other Jurassic fossils. (Type No. 203.)

Ammonites Dciiryi.

(PLATB IV, Fig. 9, a, b, c,)

Ammonite* ffrnryi, MEBK & HATDEX, Proceed. Acad. Nat. Sci. Pbila. March, 1858, 67 ; ib. Oct. 1860, 418.
Shell convex-lenticniar ; dorsnra narrowly rounded or snbangnlar ; umbilicus very (mail or nearly cloced. Vo-
lutions about doubling their diameter every turn ; inner ones entirely hidden within the profound ventral groove
of each succeeding whorl. Surface apparently without nodes or costs.

The septa are rather closely crowded, but their lobes and saddles are not very
deeply sinuous, or complex in their subdivisions, and differ somewhat in their
details on opposite sides of the shell. None of our specimens are in a condition to
show very clearly the whole of the dorsal lobe, though it appears to be as long as
the superior lateral lobe, and has at the extremity two small approximate terminal
divisions, each of which is provided at the end with three or four small digitations;
above these there is on each side one broad, but short, bifurcating, and more or less
digitate lateral branch, and, above that, one or two subordinate lateral sinuosities.
The dorsal saddle is about as large as the superior lateral lobe, a little oblique, and
has at the extremity two short, nearly equal, digitate divisions, each of which shows
a tendency to bifurcate. Below these there is on each side one lateral branch.
The superior lateral lobe is as large as the dorsal, somewhat obliquely conical, and
tripartite at the extremity, the divisions being small, subequal, divergent, and

PALAEONTOLOGY OP THE UPPER MISSOURI.

merely digitate; above these there is on the dorsal side one digitate lateral branch,
and on the ventral side one or two lateral digitations. The lateral saddle is much
smaller than the dorsal saddle, more or less oblique, and ornamented at the extremity
by some five or six very short, palmately spreading, obtuse divisions. The inferior
lateral lobe is as wide, but scarcely half as long, as the superior, and on one side of
the shell divided to its very base into two small, nearly equal, digitate parts; while
on the other side of the shell it is narrower, and tripartite. Between this and the
umbilicus there are about three very small, rather distant, digitate ventral lobes.

This species is quite distinct, in the structure of its septa, from all the other
Ammonites yet known in any of the Nebraska rocks, and we are not acquainted
with any nearly allied forms amongst foreign species. The only specimens of it we
have seen are somewhat distorted, and consist of the inner septate whorls. One
of these measures 3.10 inches in its greatest diameter, and 1.33 inch in breadth.

The specific name was given in honor of Prof. Joseph Henry, Secretary of the
Smithsonian Institution.

Locality and position. — Southwest base of the Black Hills, in the upper Jurassic
rocks of that region. (No. 314.)

ORDER Dihraiicliiata.

SUBORDER DEC APOD A.

FAMILY BELEMNITIDJS.

Shell (internal) consisting of a somewhat nacreous pen, expanded in
front, and terminating posteriorly in a thin chambered cone, with simple
septa, called the phragmocone, which is sometimes enveloped in a strong
subcorneous or calcareous guard, having a radiated semi-fibrous struc-
ture. Chambers of the phragmocone connected by a ventral siphon.

Although this family is entirely extinct, specimens of one of the genera (Belem-
noteuthis} have been found in such a state of preservation as to give a tolerably
correct idea of the softer parts of the animal. From these it has been ascertained
that it was provided with arms and "tentacles of nearly equal length, armed with
corneous hooks. The mantle was free all around, and the fins medio-dorsal.

This family embraces the genera Belemnites, Xiphoteuihis, Belemnitella, Acantlio-
teuthis, Belemnoteuthis, Conoteuthis, and Helicerus.

Genus BELEMNITES, AUCT.

Kynon.—Belemnites, LISTER, 1678, and (in whole or part) of various other pre-Linntean authors.— SCHEOTEB (part ?),
Lith. Lext. 1779, i. 151 ; Vollst. Einl. 1784, IV, 149.— ROISSY (part), Moll. V, 1805, 43.— CCVIEE (part),
Regn. An. 1817, 371.— D'ORBIONY, Palaeont. Fr. Ter. Cret. 1, 1840, 37 ; An. Sci. Nat. XVII, 1842, 241 ;
Moll. Viv. Et. Fo?s. I, 18 ** ?, 459 aud of many later writers. (Not Belemnites, LAMARCK, Prodr. 1799,
81 ; nor Syst. An. 1801, 104; nor An. Sans Vert. 1822, VII, 590, which is Belemnitella, D'ORBIONY.)

Paclites, MONTFORT, Conch. Syst. I, 1808, 318.

f Thalamus, MONTP. 1808, ib. 322.

Achelois, MONTF. 1808, ib. 358.

Callirhce, MONTF. 1808, ib. 362.

Cetosis, MONTF. 1808, ib. 370.

Acamas, MOXTF. 1808, ib. 374.

? Chri/saor, MONTF. 1808, ib. 378.

Hibolithes, MONTF. 1808, ib. 386.

i: KI'TILIAN AGE. J U RAS8IC PERIOD. 125

iu, MOJCTF. 1808, ib. 390.
.nit,,, PLKHI.XO, Brit. Aniiu. 1828, 240.
Nutotifihiirs, lifVAL-Jucm, Beleniu. 1841, 64.
(ititlruti/ihiln, lU'v AL JOCVK, ib.
Ktym. — Rixtion, a dart.
£r»M/<. — HrlrlHiiitn J'uidlidHUt, D'OBBIOKY.

IVn ci)iisi>tin^ of two parallel, nacreous, sword-snapcd processes, extending for-
ward 1'roin the anterior dorso-lateral margins of the phragmoconc. Guard elongated,
cylindrical, more or less clavate, or somewhat compressed; becoming very thin
ant< TiorK. when- it i-^ pierced by a'decp conical cavity with entire margins, for the
reception of the phragtnocone ; solid and more or less pointed at the posterior
e\tn mit\. 1'hragmoconc often terminating in a minute bulb at the apex ; septa
nearly hori/ontal, concave ; siphon contracted where it passes through the septa,
and somewhat expanded between them.

Animal unknown.

The guards of Belemnitcs, popularly called "thunderbolts," are the part most
frequently met with. They generally have a semi-translucent, somewhat horny
appearance, and a fibrous structure, the fibres radiating from a longitudinal, sub-
central lino. It varies greatly in form and size in the different species and varieties,
as well as, apparently, in the two sexes. Sometimes it only extends about half an
inch beyond the phragmocone, while in other instances it attains a length of one
or two feet. It is readily distinguished from the guard of the allied genus Bdem-
n it'll, i liy the absence of a slit down the anterior wall of the pierced end, and by
having no distinct vascular markings on the ventral side. It also wants the flattened
ridge always seen on the dorsal side of well preserved specimens of J.'clentnifil(<i.

The genus has been divided into the following sections and subsections :' —

BKTIOH 1. Acoeli, BRUSH. Without dorsal or ventral grooves.

a. Aeunrii, without lateral farrows, bat often channelled at the extremity. (Lias and Neocomian).
Type. — B. aeuariai.

b. Clarati, with lateral furrows.
Type. — B. clnnilus (Lias).

SECTION 2. Ciaatrocoeli, D'OBBIOKT. = \otOHiphites, DCVAL. Ventral groove distinct.

a. Canaliculati, no lateral farrows. (Oolites.)
Type. — Ii. ranaliculntui.

b. llastali, lateral farrows distinct. (Upper Lias and Gault.)
Type.—B. kaitatut.

Snmoif 3. .\otocoeli, D'ORBIOXT. = Gastroaiphites, DI-VAL. With a dorsal groove and farrow on each

side.
Type.—B. dilatatut (Neocomian).

The great numbers of the guards of Bclcmnites often found imbedded together in
the same stratum indicate that these mollusks were gregarious in their habits, and
they are supposed to have preferred muddy bottoms. The genus made its appear-
ance near the beginning of the Liassic epoch, during which it seems to have attained
its greatest development. It continued, however, to exist until about the middle
of the Cretaceous period.

1 Woodward's Man. Mol. p. 74

126 PALEONTOLOGY OF THE UPPER MISSOURI.

The synonymy of this genus is involved in some obscurity. We have not been
able to consult all the works in which the name was used, between the establish-
ment of the binomial system by Linnaeus, in his 10th ed. Syst. Nat. 1758,1 and the
publication of Lamarck's Prodrome, in 1799. Consequently we have no means of
determining, beyond doubt, whether or not any of these authors used it in accord-
ance with the established usages of the Linnaean nomenclature before Lamarck.
It is highly probable, however, that they did not ; and if any of them did, it is
more than probable they included both groups — that is, Belemnites^ as usually
understood, and Belemnitella, D'Orbigny. In the first case, Lamarck would be the
first binomial author that used it, and hence the author of the genus ; and in the
second case, he would be the first to select the type of the genus. In first using
the name in 1799, he gave a diagnosis, but mentions no type or example. In 1801,
however, he uses exactly the same diagnosis, and mentions B. paxillosus (referring
to Breynius's figures) as his only typical example. As this example, beyond doubt,
belongs to the typo long afterwards named Belemnitella, it follows that if we regard
Lamarck as the author -of the genus, or as the first to select its type, that the name
Belemnites will have to be retained for the Belemnitella group. If so, then Mont-
fort's name, Paclites, 1808, would have to be used for the group here described, and
the name of the following species would have to be written Paclites densus. Not
having the necessary works at hand to clear up all these doubtful questions respect-
ing the synonymy of this genus, we have concluded to use for the present at least,
the generally accepted name Belemnites for this group.

Belemnites densns.

(PLATE IV, Fig. 10, a, 6, c and PI. V, 1, la, ft, c. d, e,f, c,, h.)

Belemnites densus, MEEK & HAYDEN, Proceed. Acad. Nat. Sci. Phila. March, 1858, 58; ib. Oct. I860, 418.
Shell or guard large and thick, subcylindrical, more or less compressed laterally, the cross section having a
slightly oval outline. Lower portion tapering to a point ; sometimes a little oblique, usually more compressed than
any part above; rarely having, at the immediate point, a narrow, obscure groove on the ventral side, and a very
slight carina on the dorsal side. Surface smooth. Alveolar cavity apparently extending about half way down
from the summit, and terminating nearly midway between the centre and the ventral side ; from this point the
axial line passes down, gradually approaching the ventral margin, but curving slightly, so as not to intersect it
before reaching the extremity. Phragmocone very slightly curved ; apical angle 20O. Septa rather closely
arranged, about twenty of them occurring in a section one inch in length, measuring 0.72 inch in diameter at the
larger end, and 0.35 inch at the smaller extremity ; siphon unknown.

The most nearly complete specimen of the guard we have seen measures 5 inches
in length, and 0.90 inch in diameter at its larger end. The alveolar cavity of this
specimen is 2.39 inches in length, and 0.75 inch across at the aperture, which is
slightly oval. Some fragments in the collection, however, appear to have belonged
to individuals at least one-third larger than that from which these measurements
were taken.

This Belemnite is very closely related, in most of its characters, to B. Panderianm,
D'Orbigny, as figured in Murchison, De Verneuil, and Keyserling's work on the
geology of Russia, vol. 2, pi. 30. The only differences we have observed are that

1 Linnaeus never adopted Belemnites as a generic name, but merely used it as a kind of specific
name, under Helmintholithus, in which he included nearly all kinds of fossils. See Syst. Nat. xii.
ed., 1768, iii. 162. Gmelin used it in the same way in xiii. ed. Syst. Nat. iii. 413.

i: I!!1 1 ILIAN AGE. JURASSIC PERIOD. 127

tli. section of all our larger specimens is more nearly circular, and they appear
never to IM»SM-NS the broucl, shallow groove represented by D'Orbiguy's figures, on
tin- ventral side, near the apex Some individuals have on that part of the shell a
linear groove, but it seems never to widen upwards as represented in B. Panderir
<i mix. There is also on some of our larger specimens a slight carina near the apex
of the dorsal side (Fig. !</, PI. V), not represented by D'Orbigny's figures, nor
mentioned in his description.

Along with these large specimens we find several smaller ones, paving a propor-
tionally more slender form, and a more nearly central axial line. Some of these
also have a quite distinct, though narrow, ventral groove (Figs, d, e, /, PL V), while
their transverse section varies from subcircular to oblong-oval. These, we suspect,
belong to a distinct species, but, without better and more extensive collections for
comparison, we have not been quite able to satisfy ourselves they may not be
younger individuals of the more robust form. These two varieties appear to bear
exactly the same relations that the large and small specimens of Ji. /v//«/,/-/<i/n«
figured by D'Orbigny do to each other.

Locality and position. — Southwest base of the Black Hills, associated with Eumir
crotit curia, and other Jurassic fossils. (Type, No. 195.)

SPBKINODOM ARTICULATA.
CLASS ANNULATA.

ORDER Tllbicolo*
FAMILY SERPULID^E.

Enveloping tube more or less calcareous, or membranaceous.

Animal vermiform, rounded or somewhat compressed ; segments short.
Head lobe soldered to the oral segment, and not distinct in the adult.
Oral segment with a pencil of setae on each side, and generally provided
with a collar. Mouth directed forward, without a proboscis, situated
between the bases of the branchial plumes. Branchiae two, one on each
side, either semicircular, circular, or spirally coiled ; consisting of a basal
membrane, from the anterior margin of which the threads arise, either in
a single or double row. Setae simple and of two kinds, capillary or hooked.

The recent genera included in this family are Anisomdus, Sabella, Eriographia,
Protitla, Serpula, Spirorbw, Filograna^ and Fabricia.

The fossil forms described under the names HamultM, Spirvlcea (or Rotularia),
Cydogyra, Serpulites, Trachyderma, &c., probably also belong to this family.

Genus SERPULA, LINN^US.

Synon.— Serjmla, LIXHADI, 8y»t. Nat. 10th ed. 1758, 786 ; Ib. 12th ed. 1767.— BROO. Bncyo. Math. 1, 1793, xlr.—

LAHABCK, Syrt. An. 1801, 325.— BLAIUV. Diet. Sci. Nat. XLVIII, 1827, 549, 4o.
Etym. — Serjto, to creep.
Ezamp. — SerptUa vermic.ularit, LI.I.

128 PALAEONTOLOGY OF THE UPPER MISSOURI.

Tube calcareous, procumbent, variously curved or spirally coiled, growing singly
or in groups, attached to marine bodies; capable of receiving the entire animal.
Aperture at the larger extremity simple and rounded.

Animal without feet; mouth not provided with tentacles. Branchiae large, pec-
tinated, flabellate, with bearded lacinaB, and a cylindrical filament at the base of
each, differing in length in each of the branchiae, the longer sustaining an orbicular
disk, or funnel-shaped operculum.

This genus is closely related to Spirorbis, which some authors include as only a
section of the same group. As these two types, however, differ in their branchiae,
as well as in the regularly coiled, Planorbis-Ekc form of the tube of Spirorbis, they
are doubtless distinct genera.

The shells of these Annelids were formerly supposed to be those of true mollusks,
but as soon as naturalists examined the animal inhabiting them, it was found to
belong to the Articulata. Where we only know the shelly tubes, however, as is of
course always the case with the extinct species, it is very difficult to distinguish
species of this genus, not merely from the allied genera, but even from Vermehis, a
true mollusk. Consequently much confusion exists in the classification of the fossil
species, and for the same reason the geological range of the genus is not well deter-
mined. Some authors refer to it Devonian, and even Upper Silurian species ; but
it is quite probable that if we had any means of ascertaining the nature of the
animals once inhabiting these shells from the older rocks, they would be found to
all differ generically from the more modern and existing Serpulas. The number
of supposed Serpulas is found to increase as we ascend through the Carboniferous
and later deposits, and the genus appears to attain its maximum development at the
present time. The recent species are numerous, and attach themselves to stones,
shells, pieces of wood, the bottoms of ships, &c., and are widely distributed.

Serpula (UNDT.)

(PLATE V, Fig. 4.)

Tubes growing in small gronps, irregularly curved, slender, increasing gradually in size ; having a distinct
carina along the middle above, and a more obscure angle along each upper outer side, so as to give a subquadrate
external form to the transverse section. Under side flattened, and inclined to spread out a little on the surface
to which it is attached. Aperture and transverse section of interior circular. Surface apparently smooth, or only
having very obscure marks of growth.

Length, apparently, never more than about 2 inches ; greatest diameter, about 0.15 inch.

This species resembles rather closely some of the Jurassic forms figured by Gold-
fuss and others ; but all our specimens being worn or weathered so as to obliterate,
to a great extent, the more delicate surface characters, we do not feel warranted
in identifying it with any foreign species, nor are we clearly satisfied that it is new.

Locality and position. — Southwest base of the Black Hills. Lower part of the
Turassic rocks of that region. (Type, No. 219.)

INDEX.

Acaraas, 1:21.
Acambouia, 1C.
Acanthotcuthis, 124.
Acanthotbiris, 70.
Achclois, 124.
Acieli, 125.
Actinodusma, 23.
Acuarii, 125.
Adacna, 97.
Adula, 84.
Aganides, 64.
Agraulis, 7.
Ayraulos, 7.

ceticephalas, 10.

Oweni, 9.
Alasmodonta, 91.
Alectryonia, 72.
Alina, 108.
Allorisma, 36.

Tallin istrata, 41.

? Cooperi, 44.

? Leavenworthensis, 42, 43.

minnehaba, 43.

subcuneata, 37.
Alveolina, 13.
Ambocoelia, 17.

pcmraula, 20.
Ambonychia, 28.
Ammonita, 121.
Ammonites, 118.
Ammonites, 121.

bisulcatus, 121.

cordatus, 122, 123.

cordiformis, 122.

Henryi, 123.
Ammonitidee, 116.
Ammonitidae, 117.
Amphipcplea, 105.
Amusmura, 48.

17 March, 1805.

Amygdalnm, 85.
Anadara, 88.
A n a ti fa, US.
Anatimya, 36, 104.
Anatinidse, 36.
Anatinidae (Jurassic), 99.
Anatomue, 45.
Aneulosa, 115.
Ancyloceras, 118.
Anisoceras, 118.
Anisomelus, 127.
Anisus, 106.
Anisus, 107.

Annulata (Jurassic), 127.
Anodonta, 91.
Anodontopsis, 34, 59.
Anomia striata, 18.
Anomites, 17.
Anonica, 79.
Anthracomya, 36, 42.
Anthracoptera, 33.
Aplexa, 105.
Aploceras, 63, G4.
Aptychus, 118.
Area, 88.

costata, 34.

inornata, 89.

Nose, 90.
Arcidte, 87.
Arcince, 88.
Arcomya, 36.
Argina, 88.
Argonaata, 121.
Arionellus, 7, 8.

ceticephalas, 7.

Oweni, 9.

Articulata (Jurassic), 127.
Astarte, 34.
Aslarte, 93.

fragilis, 94.

inornata, 94.
Asturtella, 34.

Astartila, 34.
A try pa, 16, 70.
Atrypa uuisulcata, 16.
Aturia, 64.
Aocella, 28, 53.
Aulosteges, 22.
Auricularia, 74.
Aurieulitcs, 74.
Avicula cignipes, 54.

costata, 79.

curta, 81.

digitata, 79.

demissa, 28.

flabella, 29.

hirundo, 28.

(Monotis) tenuicostata, 81.

Mu listen, 79.

pleuroptera, 28.

securiformis, 29.

subfalcata, 28.

substriata, 54.

Aviculida: (Carboniferous), 27.
ATiculopccten, 29.
Aviculopeeten, 49.

amplus, 50.

doeens, 49.

McCoyi, 50.

Aviculopeeten (Permian), 49.
Aviculopectininse, 49.
Axinroa, 88.
Axininec, 88.
Axinns, 58.

ovatus, 59.

B.

, 118.
Baculina, 118.
Balantium, 5.
Bakevellia, 56.

( 129 )

130

INDEX.

Bakevellia, 28.

antiqua, 57.

parva, 57.
Barbala, 91.
Barbatia, 88.
Bathyomphalus, 105, 106
Bathyomphalus, 107.
Belemnita, 125.
Belemnitella, 124, 126
Belemnites, 125.

acuarius, 125.

densus, 126.

canaliculatus, 125.

clavatus, 125.

dilatatus, 125.

hastatus, 125.

Panderianus, 127.

Puzosianus, 124.
Belemnoteuthis, 124.
Belemnitidse, 124.
Bithynella, 114.
Bithynia, 114.
Brachiopoda (Jurassic), 68.
Brachiopoda (Potsdam Pe-
riod), 1.

Brachydontes, 85, 87.
Brachythyris, 17.
Bucardinse, 103.
Succinites, 100.
Byssanodonta, 91.

C.

Callirhoe, 124.
Callistriche, 85.
Callistrichoderma, 85
Camarophoria, 70.
Camerina, 11, 12.

Isevigata, 12.

nummularia, 12.

striata, 12.

tuberculata, 12.
Camerinidse, 11.
Camerella, 70.
Campeloma, 114.
Camptoceras, 105.
Camptonectes, 48.
Camptonectes, 76.

bellistriatus, 77.

? extenuatus, 78.
Canaliculati, 125.
Canthyria, 91.
Carboniferous Age, 48.

Carbonocola, 34, 92.
Cardiidse, 97.
Cardinia, 34, 92.
Cardiomorpha, 36.
Cardissoides, 103.
Cardita, 34.
Carditamera, 34.
Cardium, 97.

costatum, 98.

Hillanum, 97.

laevigatum, 98.

lyratum, 98.

pectinatum, 98.

scitulum, 99.
" Carrees Les," 82.
Castalia, 91.
Catillus, 108.
Cavolina, 5.

Cavolinidse(Potsd&in Period), 4.
Cellulosi, 119.
Cephalopoda (Permian), 63.
Cephalopoda (Jurassic), 116.
Ceratites, 118.
Ceromya, 36.
Cetosis, 124.
Chaenomya, 36.
Chsenomya, 42.

Cooperi, 44.

dilatata, 43.

Leavenworthensis, 43.

Minnehaha, 43.
Chladocrinus, 66.
Chilina, 105.
Chonetes, 22.

Dalmaniana, 22.

mucronata, 22.

Smithii, 22, 23.
Choristites, 17.
Chrysaor, 124.
" Clavellees, Les," 82.
Clavati, 125.
Clidiophora, 36.
Cleidophorus, 34.
Clio, 5.
Clithon, 108.
Clymenia, 64.
Clypeolum, 108.
Coelatura, 91.
Ccelospira, 16, 70.
Coleoprion, 5.
Complanaria, 91.
Conocardium, 97.
Conocephalites, 6, 8.
Conocephalus, 6, 8.

Conocoryphe, 6, 8.
Conoteuthis, 124.
Conularia, 5.

trentonensis, 5.
Coralliophaga, 34.
Corculurn, 97.
Cornei, 119.
" Costees, Les," 83.
Crassatillidx, 34.
Crassatella, 34.
Crassatellidse (Jurassic), 93.
Crassatellidaj (Permian), 61.
Crassina, 93.
Crenatula, 28.
Crenella, 84.
Crenellinae, 84.
Crinoidea (Jurassic), 66.
Crioceras, 118.
Cryptoceras, 64.
Ctenobranchiata (Jurassic), 111.
Ctenocephalus, 6, 8
Cucultea, 88.

angusta, 58.

Munsteri, 90.

Schlotheimi, 58.
Cucumaria, 91.
Cunicula, 91.
Curtonotus, 34.
Cuvieria, 5.

Cyclobranchiata (Jurassic), 110.
Cycloclypeus, 11
Cymella, 104.
Cypricardella, 34.
Cypricardites, 88.
Cypricardina, 34.
Cyprogenia, 91.
Cyrtina, 16.
Cyrtia, 17, 18, 19.
Cyrtodonta, 29.

D.

Decapoda (Jurassic), 124
Delthyris, 17.
Dendrostrea, 72.
Dentale, 111.
Dentaliidse, 110.
Dentalites, 111.
Dentalium, 111.

elephantinum, 110.

subqitadratum, 111.
Deshayesia, 108.
Dibranchiata (Jurassic), 124

INDEX

131

Pidaona, 97.

BH, 91.

s, 64.
Ililrnpit, 111.
Dolabra, 29, 88.

? alpina, 58.
I)oimcitcs, 100.
Dostia, 109.
l>n issena, 30.
Dreisseuidte, 30.
I )y MI i mi in, 91.

Krliinodcrmata (Jnrassic), 66.
Kcliiioiiiliii '! ('iilliiniiii, G2.
Kllipsolithcfl, 64, 121.
Ellipto, 92.
Klpliitliiiin, 11.
Kntloccraa, 63.
Kntulis, 110.
Kriographis, 127.
Eryeinella, 34.
Kt.mia, 70.
Eumicrotis, 28.
l-'.iniiii-rnlix, 53.

curta, 81.

garforthensis, 54.

Ualli, 54.

llilirni, 54.

llnwni, Tar. ovaia, 55.

radiatns, 54.

spelnncaria, 53.

rariabilis, 54.
Eurydesma, 28.
Eurynia, 91.
Exochorynchus, 42.

P.

Fabricia, 127.
Filograna, 127.
FlabellatK, 103.
Forarainifera (Carboniferous),

11.
Fusulina, 13.

tylindrica, 14.
hyperboiea, 14.

G.

Ganga, 114.

Gasteropoda (Carboniferous),

44.

Gasteropoda (Jurassic), 1 05.
Gasteropoda (Potsdam Pe-
riod), 4.

Qastrocirh, 135.
Gastrosiphites, 125.
Gervillia, 56.
Glebula, 91.
Gomphoceras, 63.
Gonambonites, 24.
Goniatitidee, 117.
Gonioniya, 36.
Goodallia, 93.
Grammatodon, 88.
Grammatodon, 89.

inurnatug, 90.
Gresslya, 36.
(Jryplwa, 72.
Qrypheea, 74.

arcuata, 74.

calceola, 74.

calceola, var. Nebrascemis,

74.

Gryphites, 53.
Gryphorhynchua, 28.
Gyraulus, 105, 106.
Oyraulus, 107.
Gyroccras, 65.
Gyrorbis, 112.

Haliotidffi, 45.
Halobia, 28.
Hamites, 118.
Hamulina, 118.
Hamulus, 127.
Hastati, 125.
Helicerus, 124.
Helicoccras, 118.
Helicotoma, 45.
Helisoma, 107.
Helonyx, 110.
Helix corn»a, 106.
Ilelix contorta, 107.
Helix vivipnra, 114.
Helmintholitbns, 126.
Ilemilastcrna, 91.

Hcmipecten, 48.
Ilemipronites, 25, 26.
Hemiproniiea, 24.

alternatns, 26.

arctistriatus, 26.

crog»u«, 26.

deforniis, 26.

proximus, 26.

tnmida, 24, 25.

Woolworthauus, 26.
Ilemithyris, 70.
Henternm, 114.
Heree, 6, 8.
Heteroceras, 118.
IIcterocrinQs, 67.
Hcterostcgina, 11.
Hettangia, 95.
Uiatella, 36.

sulcata, 36.
Hibolithcs, 124.
Hippagns, 84.

isocardoides, 84.
Hipparionyx proximus, 26.
Hippopodium, 34.
Honiomya, 36-
Hortolus, 64.
Hiironm, 63.
Hypothyris, 70.
Hyriopsis, 91.
Hysterolites, 17, 22.

I.

Ichthyosyagon, 118.
Imbricati, 119.
Inoceramus, 28.
Inopercnlata (Jurassic), 105.
Iridea, 91.
Iridina, 91.
Isoarca, 88.

J.

Jurassic Period, in;.

K.

Klitambonitcs, 23, 24.

132

INDEX.

Laevicardium, 97.
Lamellibranchiata (Carbonif.)

27.
Lamellibranchiata (Permian

Period), 48.
Lamellibranchiata (Jurassic),

72

Lamprostoma, 108.
Lampsilis, 91.
Lanceolaria, 91.
Larina, 114.

Carditamera, 34.
Leiorhynchus, 70.
Leptasna, 23.
Leptodomus.
fragilis, 39.
topekaensis, 40.
truncatus, 40.
granosus, 40.
Limnsridse, 105.
Limnseinse, 105.
Limninm, 92.

Limnophila (Jurassic), 105.
Limnostracitis, 72.
Limopsis, 88.
Lingula, 68.

anatina, 2, 68.
brevirostris, 69.
Beanii, 69.
cuneata, 2.
prima, 3.
Lingulepis, 69.
Lingulepis, 1.
dakotensis, 3.
pinniformis, 2.
prima, 3.

Lingulidse (Jurassic), 68.
Lingulidse, 1.
Liocardium, 97.
Liopistha, 97.
Lioplacodes, 115.
veternus, 116.
Lioplax, 114, 115.
Lirodon, 87.
Lissees, Les, €3.
Litharca, 88.
Lithocardium, 97.
Lithophaginee, 84.
Lithophagus, 84.
Lituitis, 64.
Lopha, 72.
Lunarca, 88.

I Lutetia, 34.
Lyogyrus, 112.
Lyonsia, 36.

concava, 41.
Lyrodon, 82.

M.

Macrodon, 88.
Macrodontinse, 88.
Macrodontinse (Jurassic), 89.
Macrophysa, 105.
Mactrina, 93.
Mactromya, 36.
Maldia, 60.
Malletia, 60.
Malletinse, 60.
Margarita, 92.
Margaritana, 91.
Margaritaria, 36, 104.
Margaritifera, 28, 79.
Margaron, 91.
Martinia, 16, 17.
Martinia, 19.
Matheria, 34.
Megalodon, 34.
Megalomus, 88.
Megambonia, 28, 88.
Melania, 115, 116.
amarula, 116.
veterna, 115.
Melaniidse, 118.
Melantho, 113.
Melininse, 28.
Meekia, 96.
Menetus, 107.
Menetus, 106.
Merista, 16.
Meristella (Goniocoelia) unisul-

cata, 16.
Metaptera, 91.
Micromya, 91.
Modiola, 85.

cancellata, 87.
formosa, 86.
Meekii, 86.
minuta, 86.
Wyomingensis, 52.
Modiolopsis, 85.
Modiolus, 85.
Mollusca (Carboniferous Age),

16.
Mollusca (Jurassic), 68.

Mollusca (Permian Period), 48.
Mollusca (Potsdam Period), 1.
Monocoudyllsea, 91.
Monodacna, 97.
Monodontina, 91.
Monotis, 53.
Hawni, 54,
interlsevigata, 79.
salinaria, 53, 54.
substriata, 81.
Multicostatae, 103.
Munsteria, 118.
Murchisonia, 45.
Mya, 42.

dilatata, 43, 44.
pectorum, 92.
pubescens, 101.
Myacites, 99.
Myacites, 36.

Albertii, 100.
elongatus, 100.
mactroides, 100.
musculoides, 100.
nebrascensis, 100.
obtusus, 100.
radiatus, 100.
subellipticus, 101.
ventricosus, 100.
Myalina, 30.

angulata, 30, 31.
aviculoides, 51.
lamellosa, 30.
perattenuata, 30.
perattenuata, 32.
permiana, 52.
subquadrata, 32.
Mycetopus, 91.
Mycinodon, 34.
Myoconcha, 34.
Myodora, 36.
Myophoria, 57.
Myopsis, 99.
Myrina, 84.
Mytilidae, 84.
Mytilimeria, 36.
Mytilus, 84, 85.
cancellatus, 87.
(Myalina) concavus, 52.
hirundo, 79.
modiolus, 85.
partcnus, 86.

I \ DKX

133

N.

\nntiliilir, 63.
Naiitiloccraa, 64.

biangulatus, 64.

coronntii>. ii I

ecccntrii-iia, r,.Y

I-Mwardsiauii~. i'. (

omulinntis, 64.

pinguis, 64.

pompilus, 63, 64.
•larliianus, 64.

strigalis, 64.

sulcatus, 64.
Neaera, 36.
Ni-ilo, 60.
Ncreina, 108.
NiTid'Hiius, 108.
Ni riptcron, 108.
Ncrita viridis, 108.
Nerilella, 108.

nebratcensis, 108.
Nerilidse, 108.
Nrritina, 108.
Nfritoma, 108.
Nicania, 93.
Nodularia, 91.
Northoccras, 64.
Notosiphitcs, 124, 125.
Notocceli, 125.
Nncleoapira, 16.
Nuculana, 60.
Nucula limatula, 60.
Nuculanidte, 59.
Nuculaninse, 60.
Nuculites, 34.
Naculocardia, 84.
Nacunclla, 84.

N \ Mil, 84.
Nnmmalina, 12.
Nuimmilinidie, 12.

O.

Obolella, 1.
Obolella, 3.

chromatica, 3, 4.

nana, 4.
O bolus, 1.
Obovaria, 91.
Oceanus, 64.
Odoutociueta, 101.

OdonrinctiiB, 101

Omphalia, 64.

" Ondulees, Let," 83.

Opcn'tilina, 1 1.

Opig, 34.

Orl.is, 106.

Orthis, 23.

deformis, 26.
Ortbisina, 24.

alternaU, 26.

arctistriata, 26.

crassa, 26.

raissouriana, 25.

Shiunardiana, 25.
Orthoceras, 63.
Orthonota, 36, 85.
Orthonymns, 91.
Ostracites, 72.
Oslrea, 72.

calceola, 74.

edulis, 72.

Engelmanni, 73.

Marshii, 74.

matcrcula, 73.

nobilissima, 73.
Ostreidae, 48.
Ostreidse, 72.
Ostreites, 72.
Ostreum, 72.
Ovales, 103.
Oxytoma, 79.

P.

Paclitcs, 124.
Pachycardia, 34.
Pachjrisma, 34.
Pachymya, 84.
Paludina, 114.

sabcarinata, 115.
Paludomus, 114.
Pandora, 36.
Pandorella, 36.
Panopaea Cooperi, 43, 44.

(Mjacitcs) sobelliptica,

101.

Papyridea, 97.
Paradoxidee, 6.
Paradoxidcs, 8.
Parallelcpipedum, 88.
Pcctcn bellistriatns, 77.

cottaldinus, 77.

ex ten u at us, 78.

gallicnnci, 77.

Pectcn Jacobins, 77.

lens, 76, 78.

maximns, 77.

rotomagcnsis, 77.

striato-panctatus, 76.

virgatus, 76.
Pectinites, 22, 100.
" Pectinacce*, Let," 83.
Pectinibranchiata, 111.

I'.'imi.l:,. -IS.

PiTtinidtc (Jurassic), 76.
Pectininx, 48.
Pectininw (Jurassic), 76.
Pectunculitcs, 22.
Peloria, 72.
Peloriderma, 72.
Pentacrinidtc, 66.
Pentacrinites, 66.

asteriscus, 67.
Pentacrinus, 66.
Pentagonia, 16.

Pereii, 16.
Pentagonites, 66.
Pentaraerus, 19, 70.
Permian Period, 48.
Perna, 28, 87.
Pbilopotamis, 114.
Pholadomya;a, 103.
Pholadomya, 102.

abrupta, 104.

anteradiata, 104.

arcnata, 103.

cancellata, 103.

Candida, 103.

cardissoides, 103.

cincta, 103.

decussata, 103.

humilis, 104.

multicostata, 103.

nuda. 103.

omaliana, 42.

pectinata, 103.

pelagica, 103.

semicostata, 103.

similis, 103.

tcnuicostata, 103.
Phragmoccras, 63.
Physa, 105.
Phyninx, 105.
Physopsis, 105.
P-'leolus, 108.
Pinctada, 79.
Plagio!a, 91.
Plannella, 112.

134

INDEX.

Planodiscus, 106.
Planorbella, 106.
Planorbinae (Jurassic), 106.
Planorbinx, 105.
Planorbis, 105.
PlanorUs, 106.

albus, 107.

andecolus, 107.

angulatus, 107.

bicarinatus, 106.

campanulatus, 106.

carinatus, 107.

veternus, 113.

vetemus, 107.
Planulites, 121.
Platiris, 91.
Platymya, 36, 43.

dilatata, 43.
Platyschisma, 45.
Pleuroberaa, 91.
Pleurophorus, 34.

Galhouni, 62.

costatus, 35, 61.

occidentalis, 35, 61.

?subcuneatus, 61.
Pleurophorus (Permian), 61.
Pleurotomaria, 45.

humerosa, 46.

quoyana, 45.

subturbinata, 47.

Yvanii, 46.
Pleurotomariidse, 44.
Podopthalma (Carboniferous),

44.

Podopthalraa (Jurassic), 107.
Polystomella, 11.
Polytremaria, 45.
Porambonitis, 23, 70.
Porodragus, 124.
Poromya, 36.
Possidonomia, 28.
Potsdam Period, 1.
Prisodon, 91.
Producta modesta, 16.
Productidse, 21.
Productns, 22.
Productus aximius, 25.
Pronites, 25.

adscendens, 25.
Prosobranchiata. (Carbonife-
rous), 4*.

Prosobranchiata (Jurassic), 107.
Protocardia, 97.

Shumardi, 98.

Protozoa (Carboniferous), 11.
Protula, 127.
Pteriidx, 27.
Pleria, 79.

(oxyloma) Munsteri, 80.
Pteriidse (Jurassic), 79.
Pteriinas (Jurassic), 79.
Pteriinse (Permian), 53.
Pteriminx, 28.

Pteriniinffi (Carboniferous), 30.
Pteronautilus, 64.
Pteronites, 28.
Pteroperna, 28

Pteropoda (Potsdam Period), 4.
Pterotheca, 5.
Ptychoceras, 118.
Ptychomphalus, 46.
Ptychoparia, 6, 8.
Pugiunculus, 5.
Pulmonifera (Jurassic), 105.
Pulviuitis, 28.
Puperita, 108.
Pycnodonta, 74.

Q-

Quadrula, 91.

R.

Reticularia, 17.
Retzia, 16.
Rhizopoda, 11.
Ehynchonella, 70.
psittacea, 71.
Rhynchonellidae, 16.
Rhynchonellidse, 70.
Rhynchospira, 16.
Riphidoglossata (Carbonif.), 44.
Rirulina, 114.
Rostrifera (Jurassic Period),

111.

Rotundaria, 91.
Rotularia, 127.
Rupicola, 101.

S.

Sabella, 127
Sanguinolaria, 36.
Sanguinolites, 36.

Sanguine! ites angustatus, 39.

costellatus, 40.

granosus, 40.

iridinoides, 39.

variabilis, 40.
" Scabres, Les," 82.
Scalenaria, 91.
Scaphites, 118.
" Scaphoides, Les," 82.
Scaphula, 88, 89.
Schizodus, 57.
Schizodus, 58.

alpinus, 58.

devonicus, 59.

ovatus, 59.

truncatus, 58.
Scissurella, 45.

Scutibranchiata (Jurassic), 107.
Scdgwickia, 36.
Sedgwickia, 38.

attenuata, 39.

allirostrata, 41.

concava, 41.

granosa, 40.

sulcata, 40.

topekaensis, 40.
Senilia, 88.
Serpula, 127.

(undt.), 128.

vermicularis, 127.
Serpulidse, 127.
Serpulites, 127.
Simplegades, 64.
Simplegas, 64.
Spirifer, 17, 19.
Spirifer, 16.

Clanyanus, 20.

crenistria, 26.

cuspidatus, 17.

glaber, 19.

( Marlinia)plano-convexus,
20.

(Martinia) umbonatus, 21.

urei, 20.
Spirifera, 17.

pulchra, 19.
Spiriferidse, 16.
Spiriferidse, 19.
Spiriferina, 16.

pulchra, 19.
Spirigera, 16.
Spirorbis, 107, 128.
Spirulaea, 127.
Spondylidae, 48.

I N !>i:.\

135

i, •* I

a. Ill, 7ll
Stri-ptiirliynrliiis J 1
'l.'iitulis, 25.
pi-i-tiiiifurmis, 25
p\ ramiilalis, 25.
Striurru, 88.
Struphalosio, 22.
Sin.phomriia, 22, 23.
Wnnhvortlmiia, 26.

,SV/-o///|.,)/i,vl('(/.i

Suhrlymenia, 64.
Suessia, 16.
Synryelonema, 48.
Syriugites, 110.

T.

Taraarindiformis, 85.
Tanalia, 114.
Tancredia, 95.

t tequilate ralis, 96.

Warrenana, 96.
Tancrcdiid.ee, 95
Taphius, 107.
Temnochcilus, 64.
Tcrcbratula. 17.

acuta, 70.

IVrcbratulitoB, 17, 70.
lYtrubranchiata (Jurassic), 116.
Tetrabranchiata (Permian), 63.
Teudopsis, 118.
Thalamus, 124.
Theca, 5.

aculenta, 5.

gregaria, 5.

lanccolata, 5.
Tbccalia, 34.
Thccosuiata (Potsdam Period),

4.

Theodoxus, 108.
Theora, 36.
Thracia, 36.
Thracia, 101.

f arcuate, 102.

pubescens, 101.

tsubleevis, 102.

.

TnicliyiliTiiiiu, 127.
Tr:i|M-/.ium, 34.
TrematodiBcus, 64.
Trrinatospira, 16.
Trid. .iila.

nrllites, 118.
Trigonia, 82.

alifonuis, 82.

clavcllata, 82.

Conradi, 83.

costata, 83.

longa, 83.

navis, 82.
aata, 83.

quadratu, 82.

uiitltilata, 83.
Trigonalx, 103.
Trigonella, 70.
Trigoniidx, 57.
Trigoniidte (Jurassic), 82.
Trigonocephalus, 6, 8.
Trigonotreta, 16, 17.
Triijonotreta, 19.
Triquetra, 91.
Tritogonia, 91.
Trochidae, 45.
Trochoceraa, 64.
Trochotoma, 45.
Tropidina, 112.
Tropidolcptus, 23.
Truncilla, 91.
Tubicola (Jurassic), 126.
Turbinites, 100.
Tubulus, 110.
Tulotoma, 114, 115.
Tyleria, 36.

U.

Uncites^ It!.
Unio, 92.

II ur ;il is. 1 13.

nucalis, 92.

phaseolus, 61.
Unioniilx, 90.
Uninnitfs, 100.
Unionium, 79.
Uniopsis, 91.

V.

Voginclla, 5.
Vali-nlii, 11-.'.

cristntn, 11 J

piscinalis, 112.

tscabrida, 113.

triciiriimta, 112.
I'alcatidv, 111.
Valvcarius, 112.
Vanuxcinia, 29, 88.
Velates, 108.
Veiu-ricarUia, 34.
N'rinis daumoiiiensig, 93.
Verticordia, 57, 84.
Verticordius, 84.
Viviparc, 114.
Vivipara, 114.
Viviparidee, 113.
Viviparus, 113.
Viviparus, 114.

Oilli, 115.

lincatas, 115.
Vola, 48.
Volsella, 84.
Volsella, 85.

cancellata, S7

formosa, 86.

jM-rtriiiii*, 86.
Vortex, 106.

W.

Woodia, 34.

X.

Xipliotcuthis, 124.

J

in, 60.
?gub»-ilula, r,

Zygospira, 16.

PUBLISHED BY THE SMITHSONIAN INSTITUTION,

WASHINGTON, D. 0.

APBIL, 1865.

( 136 )

EXPLANATIONS OF PLATE I.

Fig.
Fig.
Fig.

Fig.
Fig.

Fig.

Fig.

Fig.

Fig.
Fig.

Fig.

Fig.

Fig.
Fig.

lab.. • • LlNOULEPIS PINNIFORMIS.

1 a. Ventral valve of a broad specimen — worn and exfoliated.

1 4. A narrower specimen, in same condition.

2. a, b. • • • LlNGULEPIS PRIMA. .

2 a. Ventral valve, natural size, somewhat worn.

2 4. Same enlarged.

3. a, b, c,d OBOLELLA NANA.

3 a. Ventral? valve, natural size (exterior).
3 4. Same enlarged.

3 c. Interior of another specimen of same, natural size.
3 d. Same enlarged.

4. ...... AGRAULOS ? .

5. o, b, c, d, e CHONETES MUCRONATA.

6 a. Exterior of ventral valve, natural size.

5 4. Interior of same.

5 c. Outline profile view of the two valves united.

5 rf. Inside view of dorsal valve.

5 e. Enlargement of surface striae.

6. a, b, c, d, e, f, g, h, i. . . FUSULINA CYLINDRICA.

6 a. Outline, natural size.

6 4. Magnified section of same across the middle.
6 c. A portion of same very highly magnified, showing the foramina.
6 d. An outline of var. ventricosa, natural size. f
6 e. (c. by mistake on the plate.) Same enlarged.
6/. A profile or end view of same enlarged.

6 q. An outline of same enlarged, with a portion of the outer shell removed to show the waved septa
within.

6 A, t. Outline view of another variety, natural size.

7. a, b, c, d. . . . HEMIPRONITES CRASSUS.

7 a. Outside view of ventral valve.

7 4. Internal view of same, with its cardinal area, and closed foramen.
7 c. Outline of the two valves united, as seen in a side view.

7 d. Part of the hinge and interior of a dorsal valve, showing the cardinal process.

8. a, 6 SEDGWICKIA? CONCAVA.

8 a. A side view of a cast.

8 4. Outline dorsal view of same.

9 SEDGWICKIA? ALTIROSTRATA

10. a, 6 ALLORISMA SUBCUNEATA

10 a. A dorsal view of an internal cast.

10 4. Side view of same, showing muscular and pallia! impressions. (The latter too sharply defined

in the lithograph.)

11. o, b. . . . . PLEUROPHORUS OCCIDENTALS. ....

11 a. Side view of a cast of left valve. The drawing of this figure is not accurately copied in the

lithograph, it represents the beak too prominent, and too attenuate, in consequence of the
anterc-ventral margin not being made sufficiently prominent.

11 4. Dorsal outline profile of same.

12. a, b. . . . MYALINA PERATTENUATA. . .

12 a. Side view of an adult specimen retaining most of the shell.
12 4. An internal cast of a young specimen.

13. . PLEUROTOMARIA SUBTURBINATA. ....

TAOF.
2

10

22

14

14. a, b. .
14 a. Front view.
14 4. Opposite view of same.

PLEUROTOMARIA IIUMEROSA.

26

41

41
37

35

32

47
46

FL.1.

tr

4 *> »

** • < .) I'TX Mf U

EXPLANATIONS OF PLATE II.

PAGE

Fig. 1. a, b, c. . . CH^NOMTA LEAVENWORTHENSIS. . . .43

1 a. Side view, with portions of the shell removed, so as to show the muscular scars, and faintly
sinuous pallia! impression.

1 6. Dorsal view of an internal cast, showing the wide posterior gap.

Fig. 2. a, b. . . . . CH^ENOMYA COOPERI. . . 44

2 a. Side view of a cast, with a little of the posterior margin broken away.

2 b. Dorsal view of same, showing a distinct depression along the hinge left by an internal thicken-
ing of the cardinal margin.

Fig. 3. ... PLEUROPHORUS? SUBCUNEATA. .* . . fil

Fig. 4. a, 6 YOLDIA SUBSCITULA. . .... CO

4 a. Side view of a cast, left valve.

4 b. Dorsal view of same.

Fig. 5. a, b, c. . . ' . . EUMICROTIS HAWNI. ... 54

0 a. Internal cast of a left valve (ribs obscure).

5 6. Profile anterior view of a left valve.

5 c. Internal impression of a right valve showing the deep byssal sinus at (s).

Fig. 6. a, b. . . . EUMICROTIS HAWNI, var. ovata. . . . 55

6 a. Cast of the exterior surface of a left valve, showing the very short hinge line, and. distinct

costse of this variety.

6 6. Anterior profile view of same.

Fig. 7. a, b, c. . . . . MYALINA PERMIANA. . . . . 52

7 a. Internal cast of a left valve, usual form. The impression of the hinge area shown in outline

in this figure, is added from another specimen.
7 6. Anterior view of same.

7 c. Cast of a broader variety of same species not showing the cardinal area.

Fig. 8. a, b, c, d. . . . MYALINA AVICULOIDES. . . . . . .51

8 a. Cast of the exterior of a left valve, adult size.
8 b. Anterior view of same.

8 c. Cast of exterior of a young specimen.
8 d. Anterior view of same.

Fig. 9. ... AVICULOPECTEN McCoTi, (ext. cast left valve) 50

Fig. 10. ... AVICULOPECTEN ? (cast left valve). ... 50

Fig. 1 1 a, b. . . • . . SCHIZODUS OVATUS 59

11 a. Cast, left valve, side view.

11 b. Dorsal view of same.

Fig. 1 2. a, b ^BAKEVELLIA PARVA. . . . . . .57

12 a. Cast of left valve, side view, natural size.

12 6. Cast of another specimen enlarged.

Fig. 13. a, b PLEUROPHORUS CALHOUNI G2

13 a. Internal cast, side view, showing a cast of the anterior muscular impression, with a furrow

behind it, left by an internal ridge.

13 4. Dorsal view of the same, being a cast of the interior of the two valves as seen partly opened.

Fig. 14. a, b. . . . . NAUTILUS ECCENTRICUS. ... . C5

14 a. Side view of an internal cast, showing the septate and non-septate portions
14 b. Dorsal view of same.

I \llln. "It-KKOt t \CV: I'AHUd-'ll'

I'l. II

EXPLANATIONS OF PLATE III.

PACK

Fig. 1. a, b, c, d, e,f. . GRYPH^EA CALCEOLA, war. NEBRASCENSIS. . . 74

1 a. Side view of a young or dwarfed specimen (under valve), showing the incurved beak.

1 4. Side view of another individual of the same size, with the beak truncated.

1 c. Under view of the same, showing the longitudinal strize.

1 d. Longitudinal stria* enlarged.

1 e,. A larger specimen, with the whole under side of the lower valve occupied by the scar of adhesion.
\f. Upper side of an upper valve.

Fig.. 2. a, b. . . . . • PENTACRINITES ASTERISCUS. . . .07

2 a. One of the segments of the column, natural size.

2 6. The same enlarged.

Fig. 3. & 3 b LINQULA BREVIROSTRIS. . . 09

3. The usual subovate form of the species.

3 a. A narrower variety.

Fig. 4 RHYNCIIONELLA ? Dorsal valve. ... .71

Fig. 5. a, b. . . . . . VOLSELLA PERTENUIS. .... .86

5 a. Side view.

6 b. Dorsal view.

Fig. 6 CAMPTONECTES ? PERTENUIS .78

The figure represents a cast without the ears, and apparently with only concentric markings.

Fig. 7. TANCREDIA WARRENANA. .... .90

Fig. 8 TANCREDIA? ^QUILATERALIS. . . .96

Fig. 9. a, b, c. . . GRAMMATODON INORNATUS. . . . . . . 90

9 a. Side view of a somewhat worn or macerated shell.

9 6. An internal oast showing the impressions of the posterior hinge plates. Those of the anterior
side are not represented in the lithograph.

9 c. An anterior view of one valve, showing its convexity, and the curve of the beak.

Fig. 10. a, b, c, d, e. . . EUMICROTIS CUKTA . .81

10 a. Side view of left valve.

10 6. Radiating striae of same enlarged.

10 c. Right side of another specimen a little enlarged, showing the deep byssal notch or sinus;
also its concentric markings. The latter, however, are too distinct in the lithograph, and
curve in such a manner as to indicate that the outline of this valve was subsemicircular
when small, while it seems to have been of nearly the same form at all stages of growth.

10 d. Inner view of a left valve of another specimen ; the hinge margin, however, is broken away.

10 e. Anterior view of a specimen with the two valves united, though not quite closed below, and a
little compressed above.

Fig. 11. TRIOONIA CONRADI. . . . . . . .83

Fig. 12. a, b. . . . . ASTARTE ? INORNATA. . ... 94

12 a. A left valve.

12 6. Dorsal view of same.

Fig. 13. a, b, c UNIO'NUCALIS 92

13 a. Dorsal view.

13 6. Side view, with anterior margin somewhat broken.

13 c. Hinge view of an imperfect specimen. The lithograph is not a successful representation of
this hinge. It has a small compressed cardinal tooth under the beak, and a long sublaminar
posterior lateral tooth, with a furrow above it. for the reception of a similar tooth in the
other valve.

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EXPLANATIONS OF PLATE IV.

PAGE

Fig. 1. a, b, c PLANORBIS VETERNUS. 107

1 a. Side view natural size.
1 6. Same enlarged.

1 c. Section (enlarged) through the middle, showing the two sides to be nearly equally concave, and

the greater transverse diameter of the whorls, than in the direction of the plane of the shell.

Fig. 2. a, 6 VALVATA? SCABEIDA. . .113

2 a. View of the shell (enlarged) partly imbedded in the matrix.

2 /). Natural size same.

Fig. 3. a, b PHOLADOMYA HUMILIS. . 104

3 a. Side view of an imperfect cast.
3 6. Dorsal view of same.

Fig. 4. a, b. . . . . THRACIA ? SCBLSVIS (casts). . . . 102

Fig. 5. ... MYACITES NEBRASCENSIS (an imperfect cast). . . . .100

Fig. 6. a, b, c. . .• . . MYACITES SCBELLIPTICUS. ' . . . . .101

6 a. Side view of a cast.

6 6. Dorsal view of same.

6 c. View of the interior, and cardinal margin of another specimen ; hinge plate broken a little behind.

Fig. 7 ASTARTE FRAGILIS .94

Fig. 8. . .... THRACIA ARCUATA . 102

Fig. 9. a, b, c AMMONITES HENRYI. . 123

9 a. Side view of a cast.
9 4. Profile view of same.

9 c. An enlargement of one of the septa.

Fig. 10. a, b, c. . . . BELEMNITES DENSUS . 126

10 a. Specimen consisting of the lower part of the guard broken off near the extremity of the

alveolar cavity.
10 b. The broken end of same.
10 c. Part of the lower extremity of another specimen, fractured longitudinally so as to show the

lateral position of the axial liue.

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EXPLANATIONS OF PLATE V.

PAGE

Fig. 1. a, b, c, d, e, f, g, h, i. . BELEMNITES DENSUS. ... , 126

1 a. A slender specimen split longitudinally, so as to show the conical alveolar cavity, filled with

stony matrix, showing on its surface marks of the position of the septa.
1 6. Another specimen showing the exterior, and a portion of the cavity.
1 c. Part of another slender specimen below the cavity, split longitudinally, so as to show the nearly

central position of the axial line in these smaller individuals.
1 d. Part of a larger specimen (below the cavity) showing a faint farrow near the lower extremity

on the ventral side.

1 e . A similar fragment, showing near the apex a small ridge or obscure carina, on the dorsal side.
If. Fragment of upper part of a large specimen, showing a cast of the phragmocone filling the

cavity.
1 g. Transverse section of a large specimen below the middle of the cavity.

1 h. An extremity of a small specimen with a distinct ventral furrow, and a very eccentric axial

line. (May be another species.)
1 1. Transverse section of same.

Fig. 2. a, b, c, d, e. . . . AMMONITES CORDIFOEMIS. . .... 122

2 a. Side view of a cast consisting of about half a whorl.
2 6. Profile view of same.

2 c. An enlarged septum of the same.

2 d. Side view of a young individual, showing its more sharply defined costse.

2 e. Profile of same, showing its crenate dorsal keel.

Fig. 3. a, b VIVIPARUS GILLI. . .... 115

3 a. View of aperture ; specimen somewhat worn.
3 6. Opposite side same.

Fig. 4 SuiPULA ? 128

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