8 DESCRIPTION OF FIFTY-TWO SPECIES OF UNIONID.E. 



♦ 



Unio Lawii. pi. 2, fig. 4. 



Testa Isevi, obliqua, clavseformi, antice tumida, valde insequilaterali, postice obtuse angulata; valvulis 

 crassis, antice aliquanto crassioribus ; natibus prominentibus, fere terminalibus ; epidermide 

 plavida, radiis internptis indutis; dentibus cardinalibus paviusculis, acuminatis crenulatisque ; 

 lateralibus sublongis, subcurvis lamellatisque ; margarita argentea et iridescente. 



Shell smooth, oblique, clubshaped, swollen before, very inequilateral, obtusely 

 angular behind ; valves thick, rather thicker before ; beaks prominent, nearly ter- 

 minal ; epidermis yellowish, covered with interrupted rays ; cardinal teeth rather 

 small, acuminate and crenulate ; lateral teeth rather long, somewhat curved and 

 lamellar ; nacre silver white and iridescent. 

 Proc. Acad. Nat. Sci., 1871, p. 189. 

 Haft.— Tennessee River, Tuscumbia, Ala., Mr. B. Pybas ; Tennessee River, Dr. 

 Edgar ; Holston River, Miss Annie E. Law and Prof. Cope. 



My cabinet and cabinet of Dr. Lewis. 

 Diam. 1-1, Length 1-4, Breadth 1-9 inch. 



Shell smooth, oblique, clubshaped, swollen before, very inequilateral, obtusely 

 angular behind ; substance of the shell thick, somewhat thicker before ; beaks 

 prominent and almost terminal, undulate at the tips ; ligament short and dark 

 brown; epidermis yellowish with numerous interrupted rays nearly over. the whole 

 disk, vvith rather close lines of growth; umbonial slope rounded; posterior slope 

 cordate, very slightly raised ; cardinal teeth small, acuminate, crenulate, double in 

 the left and disposed to be treble in the right valve ; lateral teeth rather long, 

 somewhat curved and lamellar; anterior cicatrices distinct, small and deeply im- 

 pressed; posterior cicatrices distinct and well impressed ; dorsal cicatrices placed 

 above the centre of the cavity of the beaks ; cavity of the shell rather shallow ; 

 cavity of the beaks shallow and rounded ; nacre white and iridescent. 



BemarJcs.—A single young specimen of this species was sent to me at least 

 twenty years since by the late Dr. Edgar. Subsequently, ten or twelve years ago, 

 Mr. Pybas sent me two or three half-grown specimens. Recently I have received 

 from Dr. Lewis, of Mohawk, N. Y., five specimens, two of which are mature. 

 Until the receipt of these I could not satisfy myself entirely that the specimens so 

 long held in doubt were specifically distinct from closely allied species. These at 

 once satisfied all my doubts. More recently I owe to Prof. Cope a single half- 

 srown specimen from the head waters of the Holston River. This species belongs 

 to the group of which clavus. Lam., may be considered the type. It differs from 

 that species in not having the beaks so prominent and terminal. It is very closely 

 allied to Lesleyi (nobis), but it is not so compressed as that, nor so flat on the sides. 



