CHIEFLY OF THE UNITED STATES. 53 



epidermis straw-color, shining, without rays ; cardinal teeth rather small, corrugate, 

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

 straight ; nacre white and very iridescent. 



Proc. Acad. Nat. Sci., 1863, p. 190. 



Hab. — River Tigris, at Mosul, C. M. Wheatley. 



My cabinet and cabinet of Mr. Wheatley. 

 Diam. -9, Length 1-2, Breadth 2-5 inches. 



Shell smooth, elliptical, somewhat inflated, very inequilateral ; substance of the 

 shell somewhat thick, thicker before; beaks a little prominent, minutely undulate at 

 the tips ; ligament rather short and brown ; epidermis straw-color, shining, without 

 rays and with two or three distant marks of growth ; umbouial slope rounded ; 

 posterior slope narrow and slightly carinate: cardinal teeth rather small, roughened, 

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

 anterior cicatrices distinct and well impressed ; posterior cicatrices confluent and 

 very slightly impressed ; dorsal cicatrices placed on the upper side of the cavity of 

 the beaks ; cavity of the shell rather deep and wide ; cavity of the beaks obtusely 

 angular and shallow ; nacre white and iridescent. 



Remarks. — Among the shells from the Tigris sent to me by Mr. Wheatley were 

 three of this sjjecies, very slightly differing in outline. In outline it is near to that 

 variety of Batavus called Retzii by Nilsson, but it is more oblique and is yellow, 

 while that is dark brown. It is also near to Jordanicus, Bourg., but is a wider shell. 

 Mosulensis has a pale straw-colored epidermis, with two or three distant marks of 

 growth indicated by distinct dark bands. The undulations of the beaks are numer- 

 ous, small and beautiful. 



Unio Orontesensis. pi. 18, fig. 50. 



Testa Isevi, quadrata, inflata, valde injequilaterali ; valvulis parum crassis, antice crassioribus ; natibus 

 prominulis, ad apices crebre et minute undulatis ; epidermide rufo-fusca, obsolete radiata ; dentibus 

 cardinalibus parviusculis, compressis, acuminatis, crenulatis, in utroque valvulo duplicibusj laterali- 

 bus longis, lamellatis subrectisque ; margarita vol albida vel dilute purpurea et valde irideseente. 



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

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

 epidermis reddish brown, obscurely radiate ; cardinal teeth rather small, compressed, 

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

 nearly straight ; nacre whitish or pale purple and very iridescent. 

 Proc. Acad. Nat. Sci., 1863, p. 190. 



Eab. — River Orontes, Syria, C. M. Wheatley. 



My cabinet and cabinet of Mr. Wheatley. 

 Diam. -8, Length 1, Breadth TS inches. 



14 



