400 NEW EXOTIC UNIONIDiE, 



Shell smooth, oblong, rather compressed, very inequilateral, obliquely rounded before 

 and truncate behind ; valves rather thick, slightly thicker before ; beaks small, acumi- 

 nate and very minutely undulate at the tips; epidermis yellow, shining, without 

 rays ; cardinal teeth small, erect, a single tuberculated one on each valve ; nacre 

 pearly-white and very iridescent. 



Hah. — Biver Tigris, Assyria, C. M. Wheatley. 



My cabinet and cabinet of Mr. Wheatley. 

 Diam. -7, Length 1*3, Breadth 2-3 inches. 



Shell smooth, oblong, rather compressed, very inequilateral, obliquely rounded be- 

 fore and truncate behind ; substance of the shell rather thick, slightly thicker before ; 

 beaks small, acuminate and very minutely undulate at the tips ; ligament somewhat 

 large and dark-brown ; epidermis yellow, shining, without rays and with two or three 

 distant marks of growth ; umbonial slope very slightly raised and rounded ; posterior 

 slope, raised into a compressed carina ; cardinal teeth small, erect, a single tubercu- 

 lated one in each valve; anterior cicatrices distinct, rather large, well impressed ; 

 posterior cicatrices confluent, large and slightly impressed; dorsal cicatrices in a 

 row across the centre of the cavity of the beaks ; cavity of the shell shallow and 

 wide; cavity of the beaks very shallow and obtusely angular; nacre beautifully 

 pearly-white, with a satin lustre and very iridescent. 



Remarks. — Two specimens of this beautiful species are before me. It is the 

 second species we have seen from Western Asia. The genus was first observed by 

 D'Orbigny in South America, subsequently, several species were described by me 

 from Eastern Asia. The above-described species differs from any I have seen in its 

 outline and in the consistence of the nacre, and in the color of the epidermis. It is 

 nearest, perhaps, to jplanulata (nobis), but differs much in the outline being quadrate, 

 in having a less elevated carina and in having the posterior slope yellowish, and not 

 greenish, and in having much larger teeth. 



