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BIOLOGY LIBRARY

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MONOGRAPH

,:,

FLUVIATILE BIVALVE

OF THE RIVER OHIO

Traneiated rroro the French of C. 8. RAnw ESQUC, Prof. Bot &od Nat. Hist, in Traneylvama Unirersity.

SBSON, 108 CHE8NUT STREET. 1832.

MONOGRAPH

OF THE

FLUVIATILE BIVALVE SHELLS

OF THE RIVER OHIO,

Genera & £bf pt£«rf&fit Species.

Translated from the French of C. S. RAFINESQUE, Prof. Bot and Nat. Hist, in Transylvania University.

PHILADELPHIA :

J. DOBSON, 108 CHESNUT STREET. 1832.

LIBRARY

• * • • i * •' *•

Adam Waldie, Printer.

TO

WILLIAM HEMBEL, ESQUIRE,

ONE OF THE VICE PRESIDENTS OF THE ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA, &C.

DEAR SIR,

In publicly addressing to your notice a trans- lation of Prof. RAFINESQUE'S Monograph of the bivalve shells of the river Ohio and its -tributa- ries, it seems proper to remark, that this paper was originally published at Brussels, in Septem- ber, 1820, in " les Annales generales des Sciences physiques." Extra copies were transmitted to the author in this country, who distributed them among individuals, and the libraries belonging to

M94104

IV

scientific institutions in this city and elsewhere. It is therefore a curious circumstance in the his- tory of American Conchology, that this singular evidence of the author's acumen, zeal and indus- try, should thus have existed for more than eleven years, while but four of the numerous species discovered and described by him, are known by his names, either in the works of American authors or in our collections.

You will perceive, that the definitions as to positions of the parts of the animal, in relation to its shelly covering, now understood and adopted by several eminent naturalists, whose knowledge and opinions of their anatomical structure are esteemed authentic, have been em- ployed by Mr. RAFINESQUE ; thus, when the shell is held so as to bring the apices or beaks upper- most, and the ligament between them and the eye, it presents also the dorsal or hinge margin : this is nearly the natural position of the shell ; —

the margin or edge opposite to this, is the basal margin ; that in front, the anterior margin ; and that portion of the shell nearest to the observer, the posterior margin. When the shell is held in this manner, the right and left valves are also determined by their relative position to that of the observer.

At the same time that Mr. RAFINESQUE sub- divides the species into genera and sub-genera, he likewise retains throughout the work, for rea- sons assigned in his preliminary remarks, the genus UNIO as established by BRUGUIERE ; this arrangement will be found satisfactory, because it prevents ambiguity, and will enable the student to adopt his generic terminology at discretion.

I have much pleasure in stating, that most of the Shells described in the following pages, have been placed in my cabinet by Mr. RAFINESQVE, with his labels and references.

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A desire to facilitate the study of this interest- ing branch of American Conchology, was my in- ducement to undertake this translation. It is a fascinating subject, and has afforded me many hours of pleasing and instructive recreation. Be pleased to accept it, as a testimonial of my respect for your zeal and liberality in the pro- motion of the cause of natural science.

C. A. POULSON.

Philadelphia, October, 1831.

EXPLANATION OF THE PLATE.

The accompanying figure of the UNIO VERRUCOSA OF RAF. (described page 37) is intended to illustrate the fol- lowing parts of the Unio: — From A to D the dorsal or hinge margin, which comprises the beaks or apices, as well as the ligament; D to B the anterior margin; A to C the posterior margin ; and C to B the basal margin. The right valve is represented.

MONOGRAPH, &c.

THE numerous fresh- water and terrestrial shells which inhabit the interior of North America, had not been observed nor described when I under- took this task in the years 1818 and 1819. I was surprised and delighted to find, that they were nearly all new species, differing entirely from those found in the vicinity of the Atlantic ; so that it appears the chain of the Allegheny moun- tains which divides the country, forms a distinc- tive line between the fish and shells of the waters of the Ohio and its tributaries, and those of the rivers emptying into the Atlantic ocean. Though very far from having exhausted the study of the shells of this region, I have however observed there, collected and figured, about one hundred and eighty species; of these nearly seventy are fluviatile univalves ; fifty terrestrial univalves and sixty fluviatile bivalves. I now propose to de- scribe the latter, the univalves will be described elsewhere. I have already published many, and particularly the new Genera, in my Prodromus of the new animals of North America.

The greater number of the bivalves of the Ohio are found also in most of its tributary streams, 2

: :it 10

such as the Kentucky, Cumberland, Tennessee, Wabash, Miami, Green, Scioto, Licking, Musk- ingum, Kenhawa, &c. many of which are con- siderable rivers, of from five to eight hundred miles in length. It remains to be ascertained whether they are common to the whole of the valley of the Mississippi, to the Missouri, Ark- ansa, &c. I am certain some have been found there, and think it probable that the shells of this immense basin are analogous, although many particular species may be discovered hereafter in the great western and southern branches of these rivers.

Among the bivalves of the Ohio, the greater portion of the species belong to the genus Unio, as now established. A number of species, so great as to quadruple this genus, presenting in- finite anomalies in form and structure, is a very remarkable fact, and occasioned doubts respect- ing the annunciation of its characters. Struck at first by some differences in the animals inhabiting these shells, 1 thought I could distinguish a new family or a new genus, which I proposed to name Potamila. I was afterwards convinced, that not- withstanding the slight differences in the animals, these shells accorded entirely with the generic character of the Unio, but at the same time exhi- biting well defined secondary characters, such as, transverse or longitudinal shells, with forms either

11

elliptical, triangular, square, oboval, rounded, &c. and with the lamellar tooth, either horizontal, ob- lique, vertical, straight, curved, flexuous, &c. In my Prodromus of seventy new genera, I proposed to divide them into eight sub-genera. Since that, having increased the number of my species, it seemed proper to construct several genera and sub-genera ; I however give the name Unio, in the second place, to all my new species, in con- formity with the views of naturalists, who hesitate in adopting the changes in nomenclature which discoveries render necessary ; remarking, that by admitting all of them into the genus Unio, which will then consist of more than seventy species, it would be requisite to repeat, in the description of their specific characters, that of the characters of my new genera, which would render the defini- tion of the species prolix.

Of the Unios of North America mentioned by authors, one was discovered by the younger MICHAUX in the Ohio, and in the account of his travels it is named U. Ohiensis, but as it is not described, I cannot refer it to any of my species : besides, the name is unsuitable ; it is singular that he found but one in that river, which has produced upwards of fifty species ! The Unio Caroliniana of Bosc is imperfectly described ; however, I presume that it is not identical with any species of the Ohio. Among the new species

12

of Unios described by SAY, in Nicholson's Dic- tionary (American edition) Art. Conchology, there are four from the Ohio, viz : — U. Crassus ; U. Alatus ; U. Ovatus, and U. Cylindricus ; the description of the first one evidently comprises many species, improperly blended.

The other bivalves of the Ohio belong- to the genera, Alasmodon, Cyclas, and Notrema,* which comprise very few species.

The animals contained in these shells are scarcely fit for food, the taste being extremely flat and insipid, and consequently but little used for that purpose. Some of the large species, however, have an enticing appearance, but the only mode by which they are rendered fit for the table, consists, in soaking them for a time in vinegar, they may then be fried or soused. Se- veral kinds of fish feed on them, especially the Ambloclon grunniens. Herons also devour them, when they cannot procure fish ; and hogs are very fond of them, — herds of these animals are often seen searching for them in the rivers, and are devoured by them with avidity, notwithstanding the hard thick shell of many species. The vulgar names do not vary much, they are all confounded under those of mussel, clam, box- shell, snuff-box, &c.

* Vide supplement.— TRANS,

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The interior of many species is adorned with very brilliant colours, such as shades of purple, violet, copper, pearl, gold, and frequently irides- cent, although the colour of the epidermis which always covers the shells, is of a dark or black, brown, chestnut, ferruginous, or olive, &c. Many produce pearls or pearly and coloured excrescen- ces, some of which are very beautiful; — their variegated nacre might be made useful and profitable in the arts. In places out of the lime- stone region, these shells are gathered for the purpose of making lime. The animal is usually white, sometimes yellow or saffron coloured ; and is very long lived.

FAMILY PEDEFERIA.

Shell bivalve, equivalve, inequilateral ; animal having a large compressed foot, tendinous, not byssiferous; two very short syphons, or sometimes instead, two apertures; the anus under the ligament ; hinge dentated or lamellated.

This family includes all the bivalve shells of the Ohio, such as the genera Unio, Anodonta, &LC. of authors ; as well as my new genera separated from the Unio. I have divided it into several sub-families, of which five are found in the Ohio. 2*

14 FIRST SUB-FAMILY — UniodioB.

Shell transverse; cardinal tooth bilobed, an- terior; lamellar tooth, posterior, horizontal, or oblique; apices or beaks slightly oblique ; wrinkles concentric or zonal.

First Genus — UNIO.

Shell elliptical ; ligament straight ; cardinal tooth bilobed, commonly furrowed or sulcated ; lamellar tooth horizontal, often straight, never flexuous ; axis variable ; marginal contour usu- ally thickened ; three cicatrices or muscular impressions. Animal with a large bilobed mantle, not fringed ; syphons scarcely protruding ; with a flat bilamellar appendage at the side of each syphon ; branchiae striated in the form of a second interior and bilobed mantle.

It is thus I define the group, to which I retain the name of Unio, because it appears to be the most numerous, and resembles that known by this name in Europe ; nevertheless it seems, that if these shells are identically congeneric, the lamel- lar appendages of the syphons, and the striated mantle-like branchice, would have been noticed. Besides the three muscular impressions, many species have a muscular fossule or pit at the extremity of the lamellar tooth, which, though

15

sometimes confluent with the solitary impression on this side of the shell, is often distinct from it. If this genus differs in the animal, from the Unios of Europe, it must be called Elliptic, a name which I have given to one of its sub-genera. I divide it into four sub-genera.

First Sub-genus — ELLIPTIC.

Shell elliptical ; axis extramedial ; cardinal tooth • furrowed ; contour thickened ; ligament corneous ; lamellar tooth straight.

SPECIES I. Unio Nigra — (Elliptio Nigra.)

Shell oval-elliptical, slightly ventricose, (bom- bee /) with a slight angular truncation posteriorly ; thick ; epidermis blackish ; nacre roseate ; lam- ellar tooth thick, obtuse, slightly crenulated. Length T9j — diam. T6j — axis % of the breadth.

This is one of the large species produced in the Ohio, sometimes measuring six inches in breadth ; nacre fine, frequently iridescent, as are always the muscular impressions ; fossule distinct.

The following description of the form of the hinge, applies to all the species. Cardinal tooth bilobate, anterior, thick, trihedral, furrowed, lobes of unequal size, the anterior smallest in the right valve, the opposite one in the left ; lamellar tooth

16

simple in the right, which fits in the double lamel- lar tooth of the left valve ; ligament hard, almost calcareous, corneous exteriorly and convex ; two unequal muscular impressions beneath the cardinal tooth, the second or inferior smaller than the other ; ihefossule forms a kind of fourth muscular impression between the end of the lamellar tooth and its muscular impression, which is separated from it. Apices or summits of the valves decor- ticated, and frequently the shell also ; this has been erroneously employed by conchologists as a specific character, as it exists in all the species, except the U.Jlava, U. viridis, and young shells. This effect is accidental and secondary, and the consequence of their mode of living. In opening and closing the valves, the animal rubs them against the sand or gravel in which it resides, and thus gradually wears away the apex; if it resides in mud, the parts are very slowly denuded, whilst among gravel the whole surface of the valves becomes worn and carious. The contour of the marginal edge, is, on the contrary, quite entire, and hermetically closed by a prolongation of the membranous and flexible epidermis, which the animal forms by an exudation from its foot. No part of the shell is gaping,* except in old specimens. In order to complete the general

* In the original work, the word " brilliant" is a mis- print for " baillant. — TRANS.

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knowledge of these animals, I subjoin a de- scription of that inhabiting the U. nigra.

All the animals belonging to this family pre- sent but slight differences in colour, dimensions, and proportions.

Body white or slightly flesh coloured ; mantle smooth, thin, covering the valves, bilobed and posteriorly notched, rough, without fringes ; se- cond mantle interior, branchial, striated obliquely, thin, bilobed posteriorly, much smaller than the exterior one, and enveloping the foot ; foot com- pressed, muscular, coriaceous, oblong, dilatable ; mouth anterior ; anus posterior, at the extremity of the ligament. The anterior lateral syphons equal, one on each side, behind the mouth, in the form of a perforated tubercle ; and still further back, equally on each side, an obtuse bilamellar appendage with unequal plates, flat, oval, or ob- long, the interior one largest ; these are appa- rently the organs of generation. From this description, the result of an accurate examination of twenty species and three hundred individuals, it will be perceived, that there is a very remark- able difference between these animals and those of the European Unios, as described by authors, and particularly by FERRUSA.C, (vide Essai d'une methode conchyliogique) who prides himself on the scrupulous exactness with which he has de- scribed the fluviatile mollusca.

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These animals live on the surface of the beds of rivers ; free ; and resting in various positions, on the side or vertically, with the aperture below or oblique. They can when necessary bury them- selves in the sand or earth, particularly in winter, and even in summer in the smaller rivers subject to be dried up. They resist drought very well. Their progressive motion is very slow, effected by means of their foot, which as slowly furrows the ground. They are hermaphrodite and very prolific, the eggs are very small and enveloped in a glairy substance, frequently of a yellow co- lour. Many young shells are hatched in the shell of the parent.

This species has two varieties, viz : — Var. 1. Fusca — deep brown epidermis, pale nacre.

Var. 2. Maculata — brown spots, nacre almost white.

SPECIES II. Unio crassa — (Elliptic crassa.)

Syn. Unio crassus. SAY.

Shell elliptical, slightly ventricose, very thick ; epidermis brown ; nacre white ; lamellar tooth thick, obtuse ; wrinkles distinct. Length f— - diam. £ — axis £ of the breadth.

This species is figured by Mr. SAY under this

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name, but his description (in which from his own admission he blends several species) is worth no- thing. The shell is thicker in this, than in the preceding species ; otherwise it resembles it very much; the principal difference consists in the axis being more lateral, and the want of posterior inclination. Breadth from four to five inches.

SPECIES III. Unio viridis — (Elliptic viridis.}

Shell elliptical, obliquely truncated posterior- ly ; slightly ventricose ; scarcely thick ; apices with flexuous wrinkles ; epidermis smooth, olive green ; nacre bluish ; cardinal tooth compressed, crenulated, divergent. Length | — Diam. -^ — axis i of the breadth.

Var. 1. radiata — radiated with pale yellow.

Var. Z.fuscata — epidermis brownish olive.

A small species, at most an inch and an half in breadth, rare in the Ohio, common in the Kentucky and the small rivers adjacent. Apices seldom eroded, for they are thickened by flexuous folds or wrinkles, remarkable because the rest of the exterior is smooth. The cardinal tooth is slender, and, in consequence, becomes crenulated instead of being furrowed ; truncation oblique, convex ; muscular impressions slight ; no fossule ; lamellar tooth slender.

20 SPECIES IV. Unio Fasciata — (Elliptio Fasciata.)

Shell elliptical, ventricose, slightly thick ; epidermis slightly rugose, olive coloured, orna- mented with brown rays ; nacre bluish ; cardinal tooth rugose, divaricated ; lamellar tooth carinated. Length f — diam. ^ — axis £ of the breadth. Var. 1. nisro-fasciata — dark rays. Var. 2. alternata — greenish with blackish rays ;

alternately broader and narrower. Var. 3. cuprea — copper coloured, with olive

rays ; nacre light copper colour. A handsome species, approaching the U. ochra- ceus of SAY ; commonly small ; I have seen some specimens, however, more than three inches broad. In the rivers Ohio, Allegheny, Musk- ingum, Kentucky, Salt, Green, &c. Muscular impressions slight ; fossule deep.

Note. — We should probably refer to this sub-genus the following species of authors, and perhaps some others :

Unio Caroliniana of Bosc.

plicata 1 from Lake Erie — LESUEUR.

Var. of U. crassa.* SAY. purptirea.* SAY. Pennsylvania. . aurata, a new species from the Hud- son : it is elliptical, with the poste-

* U. crassus — 17. purpureus. SAY. — TRANS.

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rior part obliquely truncated; shell rather thick; epidermis brown, blackish, olive and gold coloured ; tooth small, rugose. Length 4 — diam. f — axis £ of the breadth. Unio pictorum, &c.

Second Sub-genus — LEPTODEA.

Cardinal tooth entire and smooth, that of the right valve simple ; contour not thickened ; liga- ment membranaceous ; lamellar tooth slightly curved.

SPECIES V. Unio leptodon — (Elliptio leptodon.)

Shell elliptical, much compressed, attenuated posteriorly, thin and fragile, somewhat rugose ; epidermis brownish ; nacre violaceous ; cardinal tooth small, obtuse^ smooth, tubercular; lamellar tooth thin and long. Length ^ — diam. J- — axis i of the breadth.

Common in the lower part of the Ohio, mostly small, for its shell is so fragile, that it easily be- comes the prey of its enemies ; notwithstanding this, it sometimes attains to three inches in breadth. The muscular impressions are slight ; fossule apparent, confluent ; animal whitish. Var. 1. olivacea — olive epidermis. 3

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Var. 2. semi-radiata, olive with rays, brown.

SPECIES VI. Uniofragilis — (Elliptic fragilis.)

Shell elliptical, a little dilated posteriorly, very thin and fragile, almost smooth ; epidermis olive ; nacre bluish ; cardinal tooth smooth, compress- ed ; lamellar tooth short. Length | — diam. | — axis i of the breadth.

Var. l.fuscata — epidermis reddish brown.

This species resembles the preceding very much ; differing from it however in shape, which is dilated instead of being attenuated, slightly compressed ; ventricose, surface almost smooth, &c. The apices not apparent ; animal yellowish; breadth about two inches. These two species nearly resemble the U. viridis, U.fasciata, U. aurata, U. nasuta, &c. which are also fragile, but may readily be distinguished by their teeth, which are very different, being smooth ; lamellar tooth somewhat curved, &c.

SPECIES VII. Unio nervosa — (Elliptio nervosa.}

Shell elliptical, widest posteriorly, thin, with flexuous nerve-like lines, concentric, vermicular ;

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border undulated ; epidermis brown ; nacre bluish. Length | — diam. f — axis £ of the breadth.

This species is rare and very distinct ; I have found it at the rapids of the Ohio; breadth one inch and an half. The cardinal tooth small and tuber- cular ; lamellar tooth narrow and curved ; mus- cular impressions slightly apparent; marginal contour somewhat thickened, undulated, and eroded.

Third Sub-genus — AXIMEDIA.

Lamellar tooth slightly curved; axis nearly medial ; valves almost equilateral.

SPECIES VIII. Unio elliptica — (Elliptio elliptica. )

Shell elliptical, angular posteriorly, thick, al- most smooth ; epidermis chestnut brown ; nacre pale violaceous ; cardinal tooth wrinkled, ob- tuse ; lamellar tooth obtuse, thick. Length £ — diam. f — axis T7F of the breadth.

This shell is also rare, found near Louisville and Maysville, K. Breadth about two inches >' muscular impressions deep ; valves slightly ven- tricose ; apices prominent, very obtuse.

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SPECIES IX. Unio lavigata — (Elliptio lavigata.}

Shell elliptical, rounded, ventricose, thick, smooth ; epidermis olive ; nacre bluish white ; cardinal tooth slightly wrinkled ; lamellar tooth short. Length %— diam. f — axis T7F of the breadth.

A small species, at most an inch in breadth; it approaches the genera Rotundaria and Cyclas. Found in the Kentucky river. .Apices rounded, prominent, and eroded ; lamellar tooth somewhat oblique. This species ought perhaps to belong to the sub-genus Plagiola, of the genus Obli- quaria.

SPECIES X. Unio zonalis — (Elliptio zonalis.}

Shell elliptical, thick, wrinkled; epidermis red- dish with brown zones ; apices prominent, ven- tricose. Length f — diam. f — axis f of the breadth.

This species is rare, found but one specimen at the falls of the Ohio ; breadth upwards of two inches.

Fourth Sub-genus — EURINEA.

Valves very transversal or broad ; axis almost lateral ; ligament very long.

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SPECIES XL Unio dilatata — (Elliptic dilatata.}

Shell elliptical, oblong, slightly attenuated posteriorly, thick, almost smooth ; epidermis red- dish brown ; nacre violet ; cardinal tooth obtuse, thick ; lamellar tooth very slightly inclined. Length i — diam. f — axis ± of the breadth.

A handsome species, very common ; nacre beautiful, often changeable purple or bluish, more or less deep or pale ; breadth three to four inches; epidermis varies red or brown ; muscular impressions striated ; fossule apparent ; cardinal tooth thick, rugose ; lamellar tooth obtuse ; ani- mal vellowish.

SPECIES XII. Unio latissima-(Elliptio latissima.)

Shell elliptical-oblong, slightly attenuated pos- teriorly, thick, smooth ; epidermis blackish ; nacre flesh coloured, with a white margin ; cardinal tooth obtuse, wrinkled ; lamellar tooth carinated, very straight and long. Length f — diam. 1 — axis I of the breadth.

A large species, attaining eight inches in breadth ; not so common as the preceding ; car- dinal tooth somewhat trihedral ; muscular im- •pressions smooth ; fossule slightly marked ; lamel- lar tooth carinated, sharp, thick, horizontal ; 3*

animal white. A similar species is found in the river Susquehanna.

SPECIES XIII. Unio solenoides — (Elliptic solenoides.}

Shell elliptical, cylindrical, attenuated, round- ed anteriorly ; retuse posteriorly ; thick, very ventricose, with flexuous posterior wrinkles ; epidermis olive brown; nacre bluish white; cardi- nal tooth rugose, obtuse; lamellar tooth very long, horizontal. Length f — diam. T4T — axis T3r of the breadth.

A very remarkable species, found in the upper part of the Ohio. Breadth about three inches ; apices prominent ;fossule visible.

Var. 1. interrupta, with some blackish lines interrupted or broken anteriorly. Var. 2. nodosa — with knots or nodosities

posteriorly.

Var. 3. cylindricus, SAY. Very thick, nacre white, apices very large.

Second Genus — LAMPSILIS.

Shell oval ; ligament curved, cardinal tooth furrowed ; lamellar tooth curved, flexuous ; axis extramedial ; marginal contour thickened ; three

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muscular impressions ; animal similar to that of the Unio, but with syphons apparent, short.

This name is modified from Lasmacampsilis, which signifies flexuolated lamellar tooth, the essential character of this genus.

SPECIES XIV. Lampsilis cardium — (Unio cardium.)

Shell oval, broad, inclined posteriorly, very ventricose, thick ; apices prominent, heart shaped ; epidermis reddish brown, rugose, black- ish posteriorly ; nacre white, roseate posteriorly. Length f — diam. f — axis ^ of the breadth.

A beautiful species, very ventricose ; breadth sometimes six inches ; cardinal tooth striated, crenulated ; lamellar tooth compressed ; animal white, bi-lamdlar appendages broad, exterior la- mellar tooth largest.

SPECIES XV. Lampsilis ovata — (Unio Ovata.) Unio ovatus, SAY.

Shell oval, regular, attenuated posteriorly, ventricose; apices prominent; epidermis corneous, brown on the posterior depression ; nacre white ; somewhat thick. Length f — diam. T3^ — axis ^ of the breadth.

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May not this be a variety of the preceding species ? It seems to differ principally in shape, being less ventricose, and less dilated posterior-

SPECIES XVI. Lampsilis fasciola — (Unio fasciola.)

Shell oval, dilated posteriorly, ventricose, somewhat thick; epidermis olivaceous with bands, radiated, flexuous, unequal, greenish. Length | — diam. f — axis ^ of the breadth ; nacre bluish white.

Rare ; found in the Kentucky ; breadth two to three inches ; cardinal tooth small, superior part furrowed, smooth and inclining inferiorly ; lamel- lar tooth slender, plaited.*

* The two following species, which I discovered in the Hudson river, ought to belong to this genus.

Lampsilis rosea. Oval, dilated and truncated obliquely, posteriorly ; shell thick, wrinkled ; epidermis olivaceous ; black posteriorly ; nacre roseate ; very ventricose ; apices prominent. Length 5-8 — diam. 1-2 — axis 4-5 of the breadth.

Lampsilis pallida. Oval, dilated and rounded posterior- ly; shell thick, wrinkles separated ; epidermis reddish olive with brown rayr, ; oblique posteriorly ; nacre white. Length 3-4 — diarr.. 1-2 — axis 4-5 of the breadth.

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Third Genus — METAPTERA.

Shell oval, triangular, dilated into a wing pos- teriorly; ligament inclined over the wing; cardi- nal tooth bilobed, crenulated ; lamellar tooth curved, detached from the edge of the wing; axis extramedial ; contour slightly thickened; three muscular impressions; animal resembles that of the Unio.

The name signifies posterior wing ; I at first adopted that of Proptera, erroneously, because it signifies anterior wing.

SPECIES XVII. Metaptera megaptera — (Unio megaptera.)

Shell thin, compressed ; epidermis brown, flexu- ously rugose ; nacre purple ; wing very large, smooth inside ; lamellar tooth double in the right valve, and with an oblong protuberance at the extremity. Length f — diam. f — axis £ of the breadth.

A fine species, common in the Ohio ; beautiful nacre, purple, iridescent ; frequently with pearli- form tubercles ; cardinal tooth, lobes nearly equal in size, smooth exteriorly; crenulated, compressed, furrowed interiorly ; anterior muscu- lar impressions strongly marked, striated; the

30

posterior one almost effaced. Breadth sometimes six inches.

The U. alatus of SAY, which is found in Lake Erie, appears to resemble this species, and to differ from it only in its wing, which is rugose inside ; contour marked, flexuous ; lamellar tooth simple in the right valve ; length four fifths of the breadth, &c. It appears that the two follow- ing species of SAY, should also be referred to this genus, but he does not point out the lamel- lar tooth as being flexuous.

U. ochraceus.

U. cariosus.

Fourth Genus — TRUNCILLA.

Shell semi-triangular, axis nearly medial : ligament oblique ; the truncation plane, oblique, posterior; cardinal tooth smooth, denticulated, compressed ; lamellar tooth compressed, oblique ; animal similar to that of the Unio.

This name is derived from the remarkably oblique truncation, which is more distinctly marked than in all the other species of this family.

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SPECIES XVIII. Truncilla triqueter — (Unio triqueter.}

Shell slightly thick, very ventricose ; apices prominent ; shape almost trihedral ; posterior part very flat, a little tessellated, ventricose ; epidermis of a deep olive colour striped with brown ante- riorly ; borders and wrinkles flexuous in the mid- dle ; nacre bluish white. Length f — diam. ^ — » axis f of the breadth.

A species very remarkable and rare, which I have observed only at the falls of the Ohio ; its form is so singular, that it has received the vul- gar name of snuff box ; I have not seen the ani- mal, which I suspect differs somewhat from that of the Unio ; breadth one and an half inches, la- mellar tooth short, broad, and obtuse ; muscular impressions slightly marked, the posterior one very large, occupying nearly all that portion of the face of the valves ; fossule very slight ; edge or border slightly flexuous.

SPECIES XIX. Truncilla truncata — (Unio truncata.)

Shell slightly thick, somewhat ventricose,

slightly square ; apices prominent ; the posterior

face truncated ; epidermis olive ; edge and

irrinkles flexuous posteriorly ; nacre bluish white.

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Length -f — diam. -^ — axis T5^ of the breadth. This species is more common than the preceding, and smaller, usually one inch in breadth ; teeth broad ; edge sharp.

Var. 1. fusca, almost entirely brown.

Var. 2. vermiculata, with flexuous brown transverse lines.

Fifth Genus — OBLIQUARIA.

Form variable, often somewhat transverse, and more or less oblique posteriorly ; ligament oblique ; cardinal tooth bilobed, commonly fur- rowed ; lamellar tooth oblique, often straight ; axis variable ; marginal contour thickened ; three muscular impressions ; animal similar to that of the Unio.

This group is numerous in species ; it differs principally from the Unio or Elliptio in its form, by the ligament and by the oblique lamellar tooth, &c. It presents many anomalies, and secon- dary characters, which oblige me to divide it into six sub-genera.

First Sub-genus — PLAGIOLA.

Axis extramedial ; lamellar tooth curved ; liga- ment curved; form of the shell variable, but not oblique.

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SPECIES XX. Obliquaria decorticata — (Unio decorticata.}

Shell rounded-elliptical, thick and very ven- tricose ; apices prominent ; epidermis blackish, nearly detached ; wrinkles separated ; nacre white. Length f — diam. 1 — axis about i of the breadth.

I have observed this species in the museum of Mr. J. D. Clifford, at Lexington, Ky. ; it inhabits the Mississippi, and apparently the lower part of the Ohio. In form it resembles the Lampsilis ; but its lamellar tooth, instead of being flexuous, is curved into an oblique and short arch. Although the animal was living, almost all the epidermiswas destroyed, even to the white nacre; and there was perceptible at the apices, intermediary, smooth, shining and olivaceous nacre. The wrinkles deep and separated; a slight oblique slope posteriorly ; cardinal tooth very much fur- rowed ; muscular impressions very deep ; fossule confluent ; breadth upwards of four inches.

SPECIES XXI. Obliquaria interrupta — (Unio interrupta.)

Shell oval-elliptical, somewhat thick, and slight- ly ventricose ; epidermis reddish brown, slightly 4

34

wrinkled, with some transversal blackish, inter- rupted bands ; nacre bluish white. Length £ — diam. £ — axis £ of the breadth.

Found in the Kentucky and Ohio; breadth about two inches -,/ossule visible ; lamellar tooth slightly rugose, thick, carinated ; apices not pro- minent.

SPECIES XXII. Obliquaria depressa — (Unio depressa.)

Shell oval-triangular, thick and much depress- ed; epidermis wrinkled, olive-brown, with oblique linear scattered black points ; nacre bluish ; somewhat truncated posteriorly. Length f — diam. f — axis ^ of the breadth.

This species is very rare. I have seen only one at Evamville, (Ind.) and deposited the only spe- cimen I possessed in the museum of Mr. J. D. Clifford of Lexington, (Ky.) with my other spe- cies. This shell is almost flat ; breadth one and an half inch ^fossule visible ; teeth striated; the lamellar tooth carinated and sharp ; it resembles the sub-genus Scalenaria.

35

SPECIES XXIII. Obliquaria lineolata — (Unio lineolata.)

Shell nearly round, thick, slightly ventricose, somewhat truncated posteriorly ; epidermis red- dish, slightly wrinkled, with brown lines ; nacre white. Length £ — diam. ^ — axis ^ of the breadth. Apices somewhat prominent.

Found at the falls of the Ohio ; breadth about two inches ; posterior portion truncated, plane, narrow; muscular impressions deep rugose; la- mellar tooth short, thick, carinated, rugose, almost straight.

Second Sub-genus^- ELLIPSARIA.

Axis extramedial ; lamellar tooth straight ; ligament straight ; shell elliptical.

SPECIES XXIV. Obliquaria ellipsaria — (Unio ellipsaria.]

Shell elliptical, with a posterior diagonal angle; epidermis somewhat wrinkled, reddish olive; nacre white ; axis almost lateral. Length £ — diam. | — axis j of the breadth.

Var. l.—fusca entirely brown ; breadth about five inches ; no fossule ; found in

36

the Kentucky ; resembles the genus Amblema ; ligament horizontal.

SPECIES XXV. Obliquariafasciolaris (Unio fasciolaris.)

Shell thick, convex, oval-elliptical, posterior- ly attenuated ; epidermis reddish, almost smooth, with oblique brown bands ; nacre white. Length | — axis i of the breadth.

Var. 1. interrupta — bands interrupted.

Var. 2. fuscata — almost entirely brown . bands black.

Var. 3. obliterata — bands almost effaced ; shell very thick.

Var. 4. longa — length f of the breadth. This species is common in the Ohio, Ken- tucky, Wabash, &c. and appears intermediate between the U. interrupta (species 21) and the Unio nasutus of SAY. The animal white, similar to that of the Elliptic . A remarkable character of this species consists in the cavity of the valves, which has some oblique wrinkles. Ligament somewhat oblique ; apices thick, but not promi~ nent ; cardinal tooth wrinkled, thick ; lamellar tooth thick, short ; fossule visible ; muscular im- pressions deep. Breadth sometimes five inches,

37

SPECIES XXVI. Obliquaria verrucosa — (Unio verrucosa.)

Shell somewhat thick, elliptical; obliquely sloped posteriorly, with verrucose wrinkles ; epidermis reddish brown ; nacre white. Length | — axis i of the breadth.

This species is remarkable for several concen- tric ranges of unequal warts, flattened, often white by rubbing ; found in the Ohio ; breadth three inches ; cardinal tooth one lobe very large, wrinkled, the other small and smooth ; muscular impressions deep and smooth ; lamellar tooth ob- tuse •; ligament horizontal.

SPECIES XXVII. Obliquaria cuprea — (Unio cuprea.)

Shell thick, elliptical, obliquely sloped poste- riorly ; epidermis black, almost smooth ; nacre copper coloured. Length | — diam. f — axis ^ of its breadth.

A very handsome species ; two inches in breadth ; nacre singular, brownish flesh inclining to copper colour, changeable to purple. I found this species in the Monongahela and Potomac ;

4*

38

lamellar tooth short ; no fossule ; cardinal tooth somewhat wrinkled ; ligament horizontal.*

Third Sub-genus — QUADRULA.

Form square, but anteriorly rounded, slightly transversal .

SPECIES XXVIII. Obliquaria flava— ( Unio flava.)

Shell somewhat thick, convex, and sloping posteriorly ; apices slightly prominent, entire, ru- gose ; epidermis nearly smooth, yellowish brown ; nacre flesh coloured. Length ^ — diam. f — axis f of the breadth.

A fine species, found only in the small rivers falling into the Kentucky, Salt, or Green rivers.

* The Unio nasutus of SAY, ought to belong to this sub-genus; and the following species, which I observed in the river Hudson, resembles it much : may not this be a variety ?

Obliquaria attenuata, — elliptical, dilated, attenuated^ with a posterior slope; ligament horizontal; epidermis rugose, dark brown ; nacre pale rose colour. Length 1-2 —diam. 1-4— axis 1-4 of the breadth. Breadtli four inches.

39

Breadth from two to four inches. Animal of a deep or orange yellow colour, with a large cir- cular foot ; in other respects it resembles Ellipta. Shell almost yellow when young ; the lamellar tooth carinated, thin ; cardinal tooth striated over the whole surface; ligament oblique, re- sembles the unio lineolata, which perhaps ought to be placed here.

SPECIES XXIX. Obliquaria Cyphia — (Unio Cyphia.)

Shell thick, ventricose, hunched ; edge flexuous, sloping posteriorly ; epidermis chestnut brown ; tubercles with flexuous wrinkles; nacre white. Length f— diam. f — axis f- of the breadth. Breadth two to three inches.

Shell thickest anteriorly, with large wrinkles, and some oblong tubercles; a large oblique longi- tudinal hunch, or boss ; cardinal tooth thick, striated ; found at the falls of the Ohio.

SPECIES XXX. Oliquaria metanevra — (Unio metanevra.)

Shell thick, ventricose, hunched, with two marginal sinuses ; one posterior and the other

40

terminal ; sloped and nerved posteriorly ; epider- mis wrinkled, brownish with dark spots ; nacre flesh coloured. Length J- — diam. T\ — axis T\ of the breadth.

A small and rare species ; scarcely more than an inch in breadth ; found in the Kentucky ; shell thin posteriorly ; nerves obliquely curved on the dilated posterior edge ; one or two hunches on the oblique elevation ; lamellar tooth short, and broad ; cardinal tooth striated ; no fossule.

SPECIES XXXI. Obliquaria reflexa — (Unio reflexa.)

Shell thick, convex, hunched, almost rounded, truncated posteriorly ; inferior edge reflected, having a posterior sinus; epidermis reddish, al- most smooth, rugose posteriorly ; nacre white, iridescent. Length £ — diam. f — axis ^ of the breadth. Breadth one and an half inches.

Attenuated posteriorly ; two hunches on the medial elevation ; its end reflected ; wrinkles se- parated, flexuous in the form of sutures ; lamellar tooth prolonged, carinated, very slightly curved ; cardinal tcoth very much striated ; fossule visible. Found in the Kentucky and at Letart's rapids : may not this species belong to the sub-genus Rotundaria ?

41

SPECIES XXXII. Obliquaria retusa — (Unio retusa.)

Shell thick, convex, without elevations, with a slight terminal sinus; epidermis olivaceous, with slight wrinkles, distant; nacre whitish. Length £ — diam. f — axis £ of the breadth.

A small species, one or two inches broad ; rare ; found in the Ohio and Kentucky ; lamellar tooth short, carinated,-jfassttfe not visible.

SPECIES XXXIII. Obliquariajlexuosa — (Unio fiexuosa.

Shell thick, with two slight elevations and a broad flat depression between them ; sloped pos- teriorly ; epidermis yellowish brown, lined with brown at the base, with flexuous wrinkles, some- what striated ; edge flexuous ; nacre bluish. Length f — diam. f — axis f of the breadth.

Found in the Kentucky, Salt and Green rivers — breadth about two inches ; lamellar tooth short, almost doubled in the right valve ; fossule visi- ble ; cardinal tooth small, striated ; muscular im- pressions deep.

Var. 1. bullata, with some broad tuber- cles, flat and transversal on the eleva- tions.

42

SPECIES XXXIV. Obliquaria nodulata — (Unia nodulata.)

Shell thick, ventricose, nodulated, sloped pos- teriorly, and truncated vertically ; linear longitu- dinal tubercles upon the posterior dilatation ; epidermis almost smooth, reddish brown ; nacre iridescent. Length |£ — diam. f — axis ± of the breadth. Breadth one inch and an half.

Found in the Kentucky, four separate nodo- sities distant ; cardinal tooth thick, striated; mus- cular impressions deep ; lamellar tooth carinated. It resembles the obliquaria retusa; both have the lamellar tooth very slightly curved.

SPECIES XXXV. Obliquaria quadrula—(Unio quadrula*}

Shell very thick, somewhat ventricose, with an oblique longitudinal elevation ; oblique furrow and sinus posteriorly; epidermis brown, wrinkled; wrinkle? striated and tuberculated anteriorly ; nacre white, roseate on the borders. Length f — diam. 4 — axis | of the breadth. Breadth two to three inches.

Common in the Ohio ; with some oblong trans- versal tubercles on the elevation ; shell somewhat sinuous on the disk ; lamellar tooth short, thick*

43

carinated, striated ; fossule confluent ; cardinal tooth large, striated ; apices truncated.

SPECIES XXXVI. Obliquaria bullata — (Unio bullata.)

Shell thick, convex, slightly ventricose, with an oblique furrow and sinus posteriorly ; strewed with irregular confluent tubercles ; epidermis reddish brown with flexuous wrinkles distant ; nacre white, flesh coloured. Length f| — diam. f — axis i of the breadth.

Found at the falls of Ohio ; rare ; breadth al- most two inches ; cardinal and lamellar teeth like preceding species ; apices rounded, decorti- cated, but not truncated ; tubercles often bleached and worn, flattened, pustulated, of various forms.

Fourth Sub-Genus — ROTUNDARIA.

Shell rounded, scarcely transversal, almost equilateral ; axis almost medial; ligament curved, short, corneous/ lamellar tooth slightly curved ; cardinal tooth somewhat anterior.

44

SPECIES XXXVII. Obliquaria tuberculata— (Unio tuberculata.']

Shell very thick, ventricose, slightly truncated posteriorly ; strewed with unequal tubercles, ex- cept anteriorly ; epidermis wrinkled, chestnut brown ; nacre violaceous. Length |£ — diam. T6T — axis T5T of the breadth.

A species common in the Ohio and adjacent rivers ; breadth three inches at most ; animal yellowish ; cardinal tooth thick ; very rugose ; lamellar tooth short, carinated ifossule confluent ; muscular impressions deep; nacre varies from bluish to deep purple.

SPECIES XXX VII I. Obliquaria Subrotunda— (Unio subrotunda.)

Shell thick, ventricose, convex, perfectly

rounded ; epidermis almost smooth, yellowish

brown ; nacre bluish white. Length almost equal

to the breadth; — diam. f — axis T7F of the breadth.

Var. 1. maculata, strewed with dark spots.

This species is common in the Ohio and its tributaries ; remarkable by its almost equilateral and not transversal form; apices prominent, rounded ; cardinal tooth thick furrowed ; lamel- lar tooth carinated, short, and somewhat punc-

45

tured j fossule confluent ; anterior muscular im- pression punctured.

SPECIES XXXIX. Obliquaria pusilla — ( Unio pusilla.)

Shell thick, convex, perfectly rounded ; epi- dermis smooth, blackish ; nacre white. Length « — diam. %• — axis ^ of the breadth.

This species is very rare ; found in the lower part of the Ohio ; breadth scarcely more than half an inch ; resembles in shape and appearance the Cyclas ; cardinal tooth almost smooth ; lamellar tooth linear. May this not be a young individual ?

Fifth Sub-Genus— SCALENAKIA.

Form obliquely triangular, scarcely transversal, but very inequilateral ; axis almost lateral ; car- dinal tooth scarcely anterior; lamellar tooth straight ; ligament oblique.

46

SPECIES XL. Obliquaria obliquata — (Unio obliquata.)

Shell very thick, ventricose ; triangularly oval ; the three sides arcuated ; a slight oblique longi- tudinal depression; epidermis almost smooth, black ; nacre purple rose colour. Length -^ — diam. T67 — axis ^ of the breadth.

A pretty species ; having a fine purple nacre with iridescent changes ; found in the Kentucky river ; breadth two to three inches ; lamellar tooth long, carinated ; fossule large, distinct ; cardinal tooth wrinkled ; muscular impressions deep ; apices prominent, truncated.

SPECIES XLI. Obliquaria triangularis (Unio triangularis.}

Shell very thick, ventricose, triangular ; poste- rior face straight ; apices prominent ; no longi- tudinal depression ; epidermis brown, almost smooth ; nacre roseate white. Length £ — diam. £ — axis | of the breadth.

Var. 1 . nigrescens — epidermis blackish : nacre white.

Common in the Ohio ; breadth sometimes four inches ; cardinal tooth [very large, furrowed ;

47

lamellar tooth thick carinated ; muscular, impres- sions andfossule deep.

SPECIES XLII. Obliquaria scalenia ( Unio scalenia.)

Shell thick, ventricose, triangular; sides almost straight, especially the posterior, which is trun- cated ; angles rounded ; no depression ; epidermis smooth, reddish brown, with some oblique longi- tudinal brown lines ; nacre white. Length £ — diam. £ — axis -^ of the breadth.

Found in the Kentucky, &c. ; breadth about two inches ; cardinal and lamellar teeth furrow- ed, confluent ; lines narrow, radiated, distant.

Sixth Sub-genus — SINTOXIA.

Shell oblique-oval; lamellar tooth and ligament curved.

SPECIES XLIII. Obliquaria lateralis — (Unio later alis.)

Shell thick, ventricose, oblique-oval ; with a slight depression, oblique longitudinal, curved,

48

narrow ;. epidermis wrinkled, brown ; nacre white. Length % — diam. f — axis £ of the breadth.

Breadth two to three inches. Cardinal tooth large, striated ; fossules visible ; lamellar tooth thick, carinated, somewhat doubled in both valves.

SPECIES XLIV. Obliquaria sintoxia (Unio sintoxia.)

Shell thick, ventricose, oblique-oval, without depression ; epidermis black, almost smooth ; nacre roseate. Length T9^— diam. ^ — axis f of the breadth.

Found in the Ohio, rare ; — breadth two to three inches ; nearly approaching the Obovaria pachostea, Obliquaria obliquata, and Obliquaria triangularis ; teeth like the latter species ; by its form, makes the transition to the genus Obovaria, which follows.

SECOND SUB-FAMILY — Amblemidia.

Shell longitudinal ; cardinal tooth under the apex ; lamellar tooth inferior vertical ; axis ter- minal ; wrinkles zonal.

49

Sixth Genus — OBOVARIA.

Shell oboval, almost equilateral ; axis nearly medial ; ligament curved ; cardinal tooth striated; lamellar tooth almost vertical, slightly curved ; marginal contour thickened ; three muscular im- pressions ; animal similar to that of the Unio, but having the anus below.

SPECIES XLV. Obovaria obovalis — (Unio obovalis.)

Shell thick, ventricose, rounded inferiorly ; apices prominent ; epidermis yellowish brown, wrinkled ; nacre white. Inferior breadth | — diam. f of the length — axis medial.

Common in the Ohio and adjacent rivers. Length from two to three inches ; cardinal tooth broad, thick, rugose ; lamellar tooth carinated, somewhat oblique : muscular impressions deep.

SPECIES XLVI. Obovaria torsa — (Unio torsa.}

Shell very thick, ventricose, rounded inferior- ly ; epidermis brownish ; nacre purple ; medial breadth f — diam. f of the length — axis medial.

5*

50

Var. marginata — nacre bordered, white.

Species rarely found in the Ohio, but more abundantly in the small rivers. Length from one to two inches ; remarkable by its apices, which are turned in front, and large wrinkles, which are often divided in two by a. furrow ; cardinal tooth wrinkled; fossule visible; lamellar tooth wrinkled, somewhat oblique, almost double even in the right valve.

SPECIES XLVII. Obovaria striata — (Unio striata.)

Shell thick, ventricose, rounded inferiorly; with striated wrinkles; apices scarcely promi- nent ; epidermis brown ; nacre white ; medial breadth |°— diam. /T of the length — axis f of the breadth.

Var. 1. tuber culata — some striated tu- bercles on the wrinkles. Var. 2. rosea — epidermis reddish brown,

brown anteriorly, nacre roseate. Length about three inches ; found in the upper part of the Ohio. Animal yellow ; lamel- lar tooth almost vertical, thick ; cardinal tooth furrowed ; fossule visible.

51

SPECIES XLVIII. Obovaria pachostea — ( Unio pachostea.)

Shell extremely thick, ventricose, rounded and attenuated or flexuous inferiorly; apices somewhat prominent ; epidermis brown, slightly wrinkled ; nacre pale violet colour ; border flexu- ous. Medial breadth T95 — diam. f^ of the length ; oblique axis f of the breadth.

A remarkable species, with an interior cavity, very small and wrinkled ; broad cavity under the tooth ; this species approaches the sub-genus Sintoxia, genus Obliquaria, its axis being somewhat oblique, or having a slight posterior dilatation. Found in the Kentucky. Length three to four inches ; lamellar tooth short, vertical, obtuse ; cardinal tooth very large and broad, fur- rowed ; fossule visible.

SPECIES XLIX. Obovaria stegaria — (Unio stegaria.)

Shell thick, ventricose, rounded inferiorly, slightly imbricated, by the large separated wrin- kles ; apices slightly prominent; epidermis brown ; nacre white ; inferior breadth i-| of the length, diam. f of the breadth ; axis medial.

52

Var. 1. tuberculata — with some scattered

tubercles.

Var. 2. fasciolata — fasciolated with green- ish brown ; nacre roseate. A pretty species, rarely longer than one inch ; lamellar tooth somewhat oblique, straight, obtuse ; cardinal tooth striated ; fossule visible ; rare in the Ohio.

SPECIES L. Obovaria cordata — (Unio cordata.)

Shell thick, ventricose, cordated inferiorly by a sinus and a slight depression ; epidermis smooth, brown ; nacre white ; apices somewhat promi- nent ; inferior breadth j-i — diam. § of the length. Axis medial.

Var. rosea — epidermis blackish, nacre roseate.

A small handsome species, about an inch long ; found in the Ohio, &c. ; rare ; lamellar tooth sharp, doubled, slightly oblique, straight ; cardi- nal tooth furrowed ; resembles the Obliquaria retusa.

Seventh Genus — PLEUROBEMA. Shell oblong, very inequilateral; ligament

53

straight, or rather unilateral ; axis quite lateral or posterior ; lamellar tooth vertical ; cardinal tooth slightly wrinkled, under the apex which is supe- rior, terminal ; four muscular impressions ,• animal similar to that of the Unio, except anus and sy- phons, which are inferior.

SPECIES LI. Pleurobema mytiloides — (Unio mytiloides.)

Shell thick, and ventricose superiorly, attenu- ated at both ends ; apices prominent, entire ; epi- dermis almost smooth, reddish brown, with some oblique black longitudinal bands ; nacre bluish ; lamellar tooth narrow; breadth f — diam. £ of the length — axis £ of the breadth.

This species rare; found in the Wabash; length two inches; apices somewhat angular, very prominent, entire, heart-shaped ; lamellar tooth very straight; muscular impressions and fossule deep.

SPECIES LIT. Pleurobema cuneata — (Unio cuneata.)

Shell thick, ventricose superiorly, oblong-oval, attenuated, wedge-shape inferiorly, rounded su-

54

periorly ; epidermis almost smooth, brown ; api- ces prominent, truncated ; nacre white, irides- cent ; lamellar tooth scarcely straight ; breadth 4 — diam. £ of the length — axis % of the breadth.

Var. 1. maculata — with some square black spots, scattered.

Var. 2. sulcata — with a slight longitu- dinal depression.

Common in the Ohio, near Steubenville, Ma- rietta, &c. ; length one to three inches ; it chiefly differs from the preceding species in its form, its lamellar tooth somewhat curved, &c. ; animal pale yellow; muscular impressions profound; the fossule forms a fourth impression, which is strongly marked.

Eighth Genus — AMBLEMA,

Shell oval, elliptical or square, very inequila- teral; axis lateral, posterior; apex lateral, ob- lique, almost superior ; ligament straight ; lamel- lar tooth vertical ; cardinal tooth wrinkled, late- ral at the apex ; three muscular impressions, Animal similar to the Pleurobema,

55

SPECIES LIII. Amblema olivaria~-(Unio olivaria.)

Shell thick, somewhat ventricose, oval, ellipti- cal ; apices scarcely prominent, almost superior ; epidermis wrinkled, olive-coloured ; nacre white, iridescent ; lamellar tooth straight ; breadth f — diam. £ — axis ^ of the length.

Var. 1. dilatata — with base dilated su- periorly. Var. 2. fasciolaris — with radiated bands,

brown.

Found in the Kentucky ; length from two to three inches ; this species is intermediate be- tween this genus and the preceding genus. Fossule visible ; cardinal tooth slightly wrinkled ; lamellar tooth thick ; ligament of a gold colour.

SPECIES LIV. Amblema rubra — (Unio rubra.)

Shell thick, ventricose, somewhat elliptical ; apices scarcely prominent, with a slight oblique or broad sinus ; furrow posterior ; axis almost lateral ; epidermis wrinkled, blackish ; nacre purple-red. Length -f — diam. -| — axis | of the breadth.

Var. 1. — lineata — reddish brown, streaked with brown lines.

56

Var. 2. — pallida — brownish, nacre pale. Found in the Kentucky ; about two inches in length ; it bears some resemblance to the Ellip- tio and Obliquaria ellipsaria ; lamellar tooth somewhat obtuse, very slightly oblique ; cardinal tooth thick, rugose ; nacre fine, iridescent, change- able with blue ; nofossule ; animal yellowish.

SPECIES LV. — Amblema torulosa — (Unio torulosa.)

Shell thick, somewhat ventricose, square-ellip- tical, with a slight oblique depression, and some nodules ; borders flexuous ; epidermis olive co- loured, with flexuous wrinkles ; nacre bluish white. Breadth f — diam. \ — axis \ of the length.

Var. angulata — depression slight, con- tour nearly angular.

Found in the Ohio and Kentucky ; length two inches ; two or three nodules on the oblique ele- vation ; lamellar tooth very straight ; no fossule ; cardinal tooth wrinkled.

SPECIES LVI. Amblema gibbosa — (Unio gibbosa.) Shell thick, ventricose, oval-elliptical, with

57

with two large knotty ribs, oblique, with inter- mediary depression ; edges flexuous / epidermis reddish brown, almost smooth ; nacre white. Breadth f — diam. 4 — axis f of the length.

Var. 1. olivacea — epidermis olive co- loured, with flexuous wrinkles. Var. 2. radiata — with radiated pale

lines.

Var. 3. difformis — with irregularly form- ed hunches (bosselures) and depres- sions.

Very common in the Ohio and adjacent rivers ; length from one to three inches ; lamellar tooth short, oblique, obtuse ; fossule visible ; cardinal tooth wrinkled ; apices prominent, heart-shaped. This species strongly resembles the genus Obli- quaria, but the cardinal tooth is under the opear, and almost inferior.

SPECIES LVII. Amblema costata — (Unio costata.)

Shell somewhat thick, flattened, slightly square, with large longitudinal ribs a little oblique, flexuous, dilated into a wing under the ligament, with curved oblique ribs; borders undulated; epidermis yellowish, almost smooth ; nacre white, iridescent. Breadth f — diam. ^ — axis -fa of the length. 6

58

This is one of the handsomest shells produced in the Ohio ; rare in that river, but less so in the tributaries of the Kentucky, &c. it attains al- most six inches in length ; nacre tinted with flesh colour, with changes of violet ; produces pearls ; I have seen one of these which was of an oblong form, measuring a quarter of an inch in length.* Apices oblique, wrinkled, entire ; lamellar tooth long, broad, sharp, compressed, slightly oblique ; no fossule ; cardinal tooth striated inferiorly. Interior borders undulated ; animal yellow.

THIRD SUB-FAMILY — Anodontidea.

Shell transverse, neither cardinal nor lamellar teeth.

Ninth Genus — ANODONTA.

Shell elliptical or oval ; ligament straight, or curved ; axis extramedial ; three muscular im- pressions, slightly apparent ; contour somewhat

* A highly respectable friend, and zealous conchologist, (JAMES S. CRAFT, Esq. of Pittsburg, Pa.) possesses a pearl, that is very little inferior in lustre and beauty to the ori- ental product ; he obtained it from one of the Ohio Unios. —TRANS.

59

thickened ; animal resembles that of the Unio. This genus may be divided into three very dis- tinct sub-genera.

First Sub-Genus — ANODONTA.

No lamellar wrinkles on the hinge. This sub- genus comprehends the greater part of the spe- cies, viz : — A. Anatina, A. cygnea, A. radiata, A. marginata, SAY — A. cataracta, SAY, — besides the two following species which I observed in the Hudson river.

ANODONTA ATBA.

Shell ventricose, thin, smooth, elliptical, black- ish; nacre white anteriorly, reddish brown, iridescent posteriorly. Length £ — diam. T52 — axis i of the breadth. Breadth does not exceed six inches.

ANODONTA CUNEATA.

Shell slightly ventricose, thin, elliptical, at- tenuated posteriorly ; epidermis wrinkled, olive brown ; nacre bluish white. Length £— - diam. £ — axis j of the breadth. Breadth four to five inches.

60

Second Sub-Genus — STROPHITUS.

Hinge with a marginal projection under the apex.

The Anodonta undulata of SAY forms this sub-genus, which, with the following, might be considered a genus.

Third Sub-Genus — LASTENA.

Hinge with two transverse wrinkles, obtuse, almost lamelliform, divergent on each side of the apex; ligament straight, membranous, double, either anterior or posterior.

SPECIES LVIII. Anodonta Ohiensis — (Lastena Ohiensis.}

Shell very thin, fragile, translucent, ventricose, elliptical, somewhat winged, and obliquely trun- cated posteriorly ; apices entire, wrinkled ; epi- dermis smooth, olive coloured or brown ; nacre bluish. Length f — diameter and axis £ of the breadth.

Var. 1. radiata — olivaceous copper colour- ed, with radiated bands, greenish,

61

Var. 2. mridis — epidermis of a fine olive

green colour.

Var. 3. violacina — nacre violaceous. Var. 4. nigrescens — blackish olive.

Very common in the Ohio, and all the adjacent rivers. Breadth from two to four inches ; the lamellar wrinkles are wholly separated from the edges of the shell ; the posterior wing is com- pressed, angular, sloping and brownish. It might perhaps have been proper to name this species A. mutabilis.

SPECIES LIX. Anodonta lata — (Lastena lata.)

Shell very thin, fragile, translucent, convex, oblong-elliptical ; apices decorticated, almost in- visible ; epidermis brown, blackish anteriorly ; nacre bluish, violet under the apices. Length f — diam. f — axis £ of the breadth.

Found in the Kentucky, &c. rare ; breadth from two to three inches ; lamellar wrinkles at the anterior edge, scarcely apparent. This spe- cies ought perhaps to form another sub-genus Hemistena, or be united to the first sub-genus, but that the ligament is double or extended from the two sides of the apices. The Lastence ap- proach the genus Dipsas, [of LEACH.] 6*

62

FOURTH SUB-FAMILY — Alasmidia.

Shell transverse ; one primary anterior tooth ; no lamellar tooth.

Tenth Genus — ALASMIDONTA.

Shell oval or elliptical, axis extramedial ; three cicatrices or muscular impressions ; ligament straight, imbricated, &c.

SPECIES LX. Alasmidonta marginata.

Shell oval-elliptical ; sloped posteriorly, with oblique, obtuse wrinkles ; epidermis olive brown, radiated with green, and wrinkled zonally ; nacre bluish white, with white edges; tooth simple, compressed, oblique. Length J of the breadth.

This genus and species were established by SAY ; (vide Journal of the Academy of Natural Sciences of Philadelphia, vol. i. p. 459,) who also refers to this genus the Unio undulatus (vide American edition of Nicholson's Dictionary, ar- ticle Conchology and Tab. III. fig. 3.) ; to these must be added also the following species.

The above described species is found in the Scioto river ; length two and an half inches. J

have not seen the animal, but the shell I have, in the cabinet of the Academy.

SPECIES LXI. Alasmidonta costata.

Shell thin, elliptical, slightly ventricose ; some- what sinuous anteriorly ; undulated with broad curved ribs posteriorly ; epidermis almost smooth, olive coloured anteriorly, blackish posteriorly ; nacre white, tinged with flesh colour ; tooth bi- lobed, compressed, oblique, crenulated. Length i — diam. £ — axis f of the breadth.

I observed this fine shell in the museum of Mr. Clifford of Lexington, Ky. from the Ken- tucky river, where it appears to be rare ; breadth nearly five inches ; decorticated anteriorly and su- periorly, but very entire posteriorly ; ribs very large inferiorly ; ligament horny and shelly, im- bricated ; tooth decurrent ; in the place of the la- mellar tooth a small, short, oblique angle ; small tubercles in the interior.

FIFTH SUB-FAMILY — Cycladia.

Shell almost equilateral, two lamellar teeth ; one anterior, the other posterior ; often one or more cardinal teeth intermediary, under the apex.

64

Eleventh Genus — CYCLAS.

Two muscular impressions; lamellar teeth oblique ; wrinkles zonal ; contour not thickened.

This genus should be reformed, notwithstand- ing the labours of MEGERLE and FERUSSAC. I propose to divide it into four sub-genera, which may perhaps form as many genera.

1st. Polymesoda. Many intermediary teeth on both valves ; shell rounded or somewhat trans- versal. Type Cyclas caroliniana, Bosc, &c.

2d. Phymesoda. One intermediary tooth in one valve ; shell somewhat transversal. Type Cyclas lacustris — C. dubia, SAY, &c.

3d. Amesoda. No intermediary tooth in one valve, at least; shell slightly transversal. Type Cyclas similis, SAY. C. lasmampsis, <$fc.

4th. Corbicula (MEGERLE.) Many interme- diary teeth in both valves ; shell triangular, somewhat lengthened. Type Cyclas hammalis, C. fluviatilis, &c.

SPECIES LXII. Cyclas lasmampsis — (Amesoda lasmampsis.}

Shell translucent, ventricose, slightly rounded ; wrinkles close together, unequal, more distant and broad superiorly ; lamellar teeth flexuous, the

65

anterior twisted, extended; length f — diam. ^ — axis T5¥ of the breadth ; nacre bluish ; breadth one third, or half an inch ; epidermis variable, black, blackish, brown, brownish, olive ; reddish brown, horn colour, &c.; apices rounded, not pro- minent. Found in the Ohio, and adjacent rivers ; no intermediary teeth.

SPECIES LXIII. Cyclas aqualis — (Phymesoda cequalis.)

Shell translucent, ventricose, rounded; wrinkles close together, almost equal, obtuse ; lamellar teeth somewhat flexuous, short, distant, equal ; intermediary tooth oblique, single in each valve ; epidermis corneous ; nacre bluish. Length •§•— diam. f of the breadth ; axis medial.

A small species ; length one quarter of an inch, rare ; found in the Ohio ; internal tooth scarcely apparent, obliquely inclined posteriorly ; right valve with two oblong lamellar and almost equal fossules ; the left valve with a corresponding la- mellar tooth ; apices rounded, not prominent.

66

In this place I shall describe two species that have a slight relation to the subject ; viz. a tri- valve shell and a mytilus from Louisiana. I have added also some species that have been omitted in their proper places, or discovered during the progress of the work.

Twelfth Genus — TREMESIA.

Shell tri-valve, inequivalve, principal valve patelloid, perforated in the centre ; the small valve closing this aperture, as an operculum f third valve inferior, lateral; the animal cepha- lous, the head extensible by the medial opening, with two lateral eyes ; no tentacula.

This singular genus appears to be the type of a new family intermediate between the Bra- chiopes, Teredaria, and Patellaria; like the teredaria it has three valves, but a head like the patellaria, and this oculated and not tentacu- lated head is central instead of being terminal.

67

SPECIES LXIV. Tremesia patelloides.

Principal valve rounded, somewhat conical, striated concentrically, and tessellated by curved oblique transversal striaB ; aperture round ; small valves smooth ; inferior valve oblique, oboval ; animal striated flexuously beneath, acute oppo- site the inferior valve ; head truncated.

Animal very singular ; which I announced in the American Monthly Magazine, last year, under the defective name of Notrema. It is found in the lower part of the river Ohio, attach- ed to the stones by the base, like the Patella ; shell brownish fawn coloured ; opercular valve brown, glossy, movable ; diam. about one inch, height half an inch.

SPECIES LXV. Mytilus recurvus.

Shell oboval, cuneiform, recurved, with longitu- dinal striae of three lengths ; epidermis blackish ; nacre violet ; the beaks oblique, with a decurrent angle on each side ; the inferior and interior bor- der, striated, crenulated. Breadth T72- — diam. fa of the length.

Found in the Mississippi near New Orleans —

68

length from one to two inches ; the stria are often bifid ; the gaping part oblong, lateral.

SPECIES LXVI. Ifnio teres — (Elliptic teres.)

Shell slightly thick, ventricose, elliptical, widened, truncated, inferiorly, posteriorly, and obliquely ; epidermis almost smooth, corneous ; nacre white, iridescent. Length about J- — diam. | — axis ^ of the breadth ; this species belongs to the sub-genus Eurynia — vide page 24.

Found in the river Wabash ; breadth about three inches ; slightly sinuous inferiorly ; apices eroded ; lamellar tooth long, thin ; cardinal tooth crenulated, decurrent.

SPECIES LXVII. Obliquaria sinuata — (Unio sinuata.)

Shell thick, ventricose, elliptical, sinuous in- feriorly ; epidermis reddish brown, wrinkled : nacre white, with deep oblique interior furrows. Length •£ — diam. i — axis j of the breadth. This species belongs to the sub-genus Ellipsaria. Vide page 35, found in the Kentucky — breadth four inches ; lamellar tooth thick, oblique,

69

straight, wrinkled \fossule visible ; cardinal tooth striated.

SPECIES LXVIII. Obliquaria atroviolacea — (Unio atroviolacea.)

Shell somewhat thick, convex, elliptical, oval, and posteriorly attenuated ; epidermis blackish, almost smooth ; nacre very deep violet colour ; border dull brown. Length ^ — diam. £ — axis ^ of the breadth. This species belongs to the sub-genus Ellipsaria, Vide page 35.

A handsome species with a fine nacre; breadth three inches — found in the Kentucky, &c. la- mellar tooth carinated straight jfossule confluent; muscular impressions deep ; teeth wrinkled.

SPECIES LXIX. Obliquaria Cliffordiana — (Unio Cliffordiana.)

Shell thick, ventricose, oval, rounded ; very long posteriorly ; sloped posteriorly ; nacre nearly smooth, blackish, pale purple. Length £ — diam. f- -axis i of the breadth. This species belongs to the sub-genus Plagiola. Vide page 32.

In the museum of Mr. Clifford ; found in the Kentucky. Breadth three inches ; lamellar tooth 7

70

curved, thick, wrinkled ',fossule visible ; cardinal tooth striated ; apices slightly prominent, decorti- cated ; nacre smooth, saffron colour.

REMARKS.

When the ligament is mentioned in the prece- ding pages, the great posterior one is alluded to ; there is also an anterior membranous and folia- ceous ligament in all these shells, which is very small and short, in the elongated or rounded, and larger or oblong, in the elliptical or dilated shells.

Having more carefully examined the species, No. 48. Obovaria pachostea, vide page 51, I have discovered that it belongs to the genus Amblema, to which it must be united, its charac- ters are as follow : —

Amblema antrosa, very thick, somewhat ven- tricose, rounded, flexuous with a small lateral sinus inferiorly ; epidermis brown, lamellar ; nacre violaceous, pale, undulated, and a large cavity under the bilobed (cardinal) tooth. Breadth f — diam. |- of the length ; — axis almost terminal.

Page.	Page.
ALASM1D1A, sub-family	62 Scalenaria, sub-genus	- 45
ALASMIDONTA, genus	02 Sintoxia, sub-genus	47
costata	03 Strophitus, sub-genus	60
marginata (Say) 6-2 TREMESIA, genus AMBLEMIDIA, sub-family 48 patelloides	66 - 67
AMBLEMA, genus Amesoda, sub-genus	54 TRUNCILLA, genus - 64 UNIODLE, sub-family	30 14
ANODONTIDIA, sub-family	58 Umo, genus	14
ANODOXTA, genus	58 alatus (Soy)	30
atra	59 antrosa	- 70
cataracta (Soy)	59 atroviolacea
cuneata	53 attenu.ita, note	38
cygnea	59 aurata, note	20
lata	61 bullata	43
ohiensis	60 cardium	27
var. 1.	60 cariosus, (Soy)	30
var. 2.	61 caroliniana, (Base)	11.20
var. 3.	61 cliffordiana	69
var. 4.	61 cordata	52
radiata	53 var.	52
undulata (Say)	60 costata	57
rfiimedia, sub-genus	23 crassa	18
CYCLADIA, sub-family	63 crassus, (Say) ;	18.20
CYCLAS. genus	64 cuneata	53
squalls	65 var. 1.	54
fluviatilis	04 var. 2.	54
hammalis	64 cuprea	37
lasmampsis	C4 cylindricus, (Soy)	16
Corbicula, sub-genus	64 cyphia	39
Elliptic, sub-genus Ellipsaria, sub-genus	15 decorticata 35 depressa	- 33 34
Eurynia, sub-genus	24 dilatata	25
LAMPSILIS, genus	26 ellipsaria	- 35
Lastcna, sub-genus	60 var. 1.	35
Leptodea. sub-genus	21 elliptica	23
METAPTERA, genus	29 fasciata	20
Mytilus recurvus	67 var. 1.	20
NOTREMA, genus 1	2. 67 var. 2.	20
OBLIQUARIA, genus	32 var. 3.	20
OBOVARIA, genus	49 fasciola	28
PEDEFERIJJ, family -	13 fasciolaris	36
Ptiymcsoda, sub-genus	64 var. 1.	36
Plagiola, sub-genus	32 var. 2.	36
PLEUROBEMA, genus	52 var. 3.	36
Polymesoda, sub-genus	64 var. 4.	36
Quadrula, sub-genus	38 flava	38
Rotundaria, sub-genus	43 flexuosa	4J

72

Page. Page. Uuio rlexuosa, var. 1. - 41 Unio quadrula - - 42
fragilis	22	reflexa	40
var. 1.	22	retasa	41
gibbosa	56	rosea, note	28
var. 1.	57	rubra	55
var. 2.	57	var. 1.	55
var. 3.	57	var. 2. - -	56
interrupta	33	scalenia	47
lateralis	47	stegaria	51
latissima	25	var. 1.	52
leptodon	21	var. 2.	52
var. 1.	21	sintoxia	48
var. 2.	22	sinuata	68
laevigata	24	solenoides	26
lineolata	35	var. 1.	26
megaptera	29	var. 2.	26
metanevra	39	var. 3.	26
mytiloides	53	striata	50
nasutus (Say) note	38	var. 1.	50
nervosa	22	var. 2.	50
nigra	15	subrotunda	44
var. 1.	18	var 1.	44
var. 2.	18	teres -	68
nodulata	42	torsa	49
obliquata	46	var.	50
obovalis	49	torulosa	56
ochraceus, (SayJ	30	var. 1.	56
ohiensis, (Michaux)	11	triangularis	46
olivaria	55	var. 1.	46
var. 1.	55	triqueter	31
var. 2.	55	truncata	31
ovata	27	var. 1	32
ovatus (Say)	27	var. 2.	32
pachostea	51	tuberculata	44
pallida, note.	28	verrucosa	37
pictorum plicata, (Lesueur) purpureus (Say) pusilla	21 20 20 44	viridis var. 1. var 2. zonal is	19 19 19 24

95= Page 24, 3d line from bottom, for Eurinea read Eurynia.

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