296 Panama Shells. CORBULID^. 



Habitat. Panama ; C. B. A. ! 



1 specimen was obtained about 2 miles east of Panama. 



500. Potamomya inflata. Nov. sp. 



Shell ovate, ventricose, inequilateral, moderately inequivalve ; 

 posterior margin subtruncated between the extremities of two 

 umbonial angles, of which the upper one is indistinct ; ventral 

 margin moderately excurved ; anterior margin abruptly and 

 regularly rounded: white beneath a pale brown epidermis: 

 with unequal strias of growth : beaks small : urnbones very 

 prominent, somewhat compressed : teeth small ; tooth of the 

 left valve with a medial ridge. 



Length .7 inch ; height .57 inch ; breadth .5 inch. 



A less ventricose variety has the following dimensions : 



Length .6 inch ; height .46 inch ; breadth .33 inch. 



Station. With P. cequalis, q. v. 



Habitat. Panama ; C. B. A. ! 



3 specimens were obtained with P. cequalis. 



501. Potamomya trigonalis. Nov. sp. 



Shell solid, triangular, moderately inequivalve, subequi- 

 lateral ; upper posterior margin moderately excurved, forming 

 an angle with the slightly excurved ventral margin ; anteriorly 

 with the dorsal margin abruptly and regularly rounded into 

 the ventral margin : white beneath a pale brown epidermis : 

 with fine striae of growth ; with a sharp umbonial angle defining 

 a posterior area : beaks large and prominent : umbones promi- 

 nent, somewhat compressed : teeth large and robust ; tooth of 

 the left valve with a medial ridge. 



Length .95 inch ; height .8 inch ; breadth .56 inch. 



Station. With P. cequalis, q. v. 



Habitat. Panama ; C. B. A. ! 



2 specimens were obtained. 



