AMPHIDESMA. Panama Shelb. 289 



cave, otherwise with all the margins well rounded : purple near 

 the beaks, otherwise dingy white : interior similarly colored, 

 but with the purple region larger: smooth near the beaks, 

 otherwise with fine raised concentric lines, and crowded radiat- 

 ing striae, which are mostly microscopic, and which posteriorly 

 are divergent and wholly microscopic; beaks small, prominent: 

 umbones convex. 



Length ,85 inch ; height ,74 inch ; breadth .42 inch. 



Station, — Unknown. 



Habitat — Panama ; C. B. A. I 

 Only 1 valve was found. 



486. Ainpltidesma ellipticum ? 



iSymmymy. 



Amphidesma ellipticum Sowb. in Proc. Zool. Sdc. Lond. 



p. 200. .... Dec. 1832, 

 Hanley Descr. Catal. p. 46. 1846? 



Station. — Dredged at a depth of 9 fathoms in sandy mud; 

 Cuming I Sowerby. 



Habitat. — ^Monte Christi; Cuming! Sowerby. 

 West Columbia ; Hanley. 

 Panama ; C. B. A. 1 

 We obtained 20 specimens on the reef at low water mark. 

 Most of them are in fine condition, although none were taken 

 alive. 



487. Amphidesma proximum. Not. sp. 



Shell suborbicular, slightly flexuous, a little inequilateral, 

 with the anterior dorsal margin concave, with the posterior 

 dorsal margin a little excurved, subtruncated posteriorly, other- 

 wise with the margins well rounded : snow white, with a thin 

 slate or umber-colored epidermis : centrally and anteriorly with 

 very fine rather distant raised lines; with extremely minute 



JULY, 1852. 73 A.MH. Lto. Nat. Hiai. 



