AMPHIDESMA. Panama /Shells. 291 



St. Elena ; Jay. 

 Panama ; C. B. A. ! 

 We found 4 specimens. 



489. Amphidesma striosum. Nov. sp. 



Shell elliptical, slightly flexuous, inequilateral ; with the 

 posterior dorsal margin slightly excurved, with the anterior 

 dorsal margin concave, otherwise with the margins well 

 rounded : pale yellowish brown : with numerous fine raised con- 

 centric lines, and closely crowded radiating striae, which are 

 mostly microscopic : beaks small, approximate : umbones con- 

 vex: corselet and lunule not well defined. 



Length .78 inch ; height .71 inch ; breadth .33 inch. 



Station. Unknown . 



Habitat. Panama ; C. B. A. ! 

 1 specimen was found. 



490. Amphidesma tortuosum. Nov. sp. 



Shell compressed, subequilateral, triangular above, orbicular 

 below, the slightly excurved posterior dorsal margin and the 

 slightly concave anterior dorsal margin meeting at an angle of 

 about 125, and the rest of the margins being well rounded ; 

 posterior side very flexuous, with a broad deep groove on the 

 left valve and a corresponding ridge on the right valve : dingy 

 white : with numerous concentric ridges, which are crossed by 

 radiating strias that are partly microscopic : beaks very minute, 

 approximate : left umbo flat, right one convex : corselet and 

 lunule long and narrow, deeply concave. 



Length 1.25 inch; height 1.1 inch ; breadth .35 inch. 



Station. Unknown. 



Habitat. Panama ; C. B. A. ! 

 1 specimen was obtained. 



