CHIEFLY OF THE UNITED STATES. 55 



before and biangular behind ; substance of the shell very thick, thicker before ; beaks 

 prominent, swollen ; ligament rather short and thick ; epidermis straw yellow ; with- 

 out rays, with distant marks of growth; umbonial slope raised and obtusely angular; 

 posterior slope broad, flattened, with two obscure impressed lines in each valve from 

 the beaks to the posterior margin ; cardinal teeth large, erect, rather compressed, 

 corrugate, crenulate and double in both valves ; lateral teeth very long, thick, corru- 

 gate and somewhat curved ; anterior cicatrices distinct, large and deeply impressed ; 

 posterior cicatrices distinct, large and well impressed ; dorsal cicatrices placed on the 

 upper side of the cavity of the beaks and on the cardinal tooth ; cavity of the shell 

 deep and wide ; cavity of beaks rather deep and obtusely angular ; nacre white, 

 satin-like and very iridescent. 



Remarlcs. — Two specimens only of this fine species are before me, but they are 

 very perfect. It is allied to dignatus on one side and vasus, both herein described, 

 on the other, but need not be confounded with either. It is not so oblique as the 

 former nor so transverse as the latter. It is biangular behind which neither of the 

 others are. It does not seem to have any undulations on the tips. Although the 

 epidermis is removed from the tips they appear to be otherwise perfect, and I cannot 

 find a trace of undulation. The marks of growth are very dark and are very distant. 

 This specimen has four. I have great pleasure in naming this species after M. J. R. 

 Bourguignat, who has described so m.any new species of Unionidce from Asia Minor, 

 in the " Voyage autour de la mer morte par De Saulcy," and in the " Revue et Maga- 

 zin de Zoologie." 



Unio Damascensis. pi. 18, fig. 52. 



Testa Isevi, quadrata, compressa, valde inaequilaterali ; valvulis crassiusculis, antice crassioribus ; natibus 

 prominulis, ad apices crebre et oblique uudulatis ; epidermide luteo-viridi et obsolete radiata ; denti- 

 bus cardinalibus parviusculis, compressis, crenulatis, in utroque valvulo duplicibus; lateralibus 

 longis, lamellatis rectisque ; margarita argentea et iridescente. 



Shell smooth, quadrate, compressed, very inequilateral ; valves somewhat thick, 

 thicker before ; beaks a little prominent, closely and obliquely undulate at the tips ; 

 epidermis yellowish green and obscurely rayed ; cardinal teeth rather small, com- 

 pressed, crenulate and double in both valves ; lateral teeth long, lamellar and 

 straight; nacre silver white and very iridescent. 

 Proc. Acad. Nat. Sci., 1863, p. 100. 



Hab.— River Barada, Damascus, Asia Minor, C. M. Wheatley. 



Cabinet of Mr. Wheatley. 

 Diara. -6, Length -9, Breadth IG inches. 



Shell smooth, quadrate, compressed, very inequilateral ; substance of the shell 

 somewhat thick, rather thicker before ; beaks slightly prominent, closely and obliquely 



