422 bulletin: museum of comparative zoology. 



the slightly arcuate base ; posterior dorsal margin straight, more rapidly descend- 

 ing, the posterior end with a narrow, oblique truncation, slightly angular below ; 

 surface sculptured with close, minute, concentric lines giving it a silky lustre, 

 and with occasional stronger sulci, indicating resting stages ; above the posterior 

 angle the lines are coarser and more elevated, and near the margins are traces of a 

 thin, brownish periostracum ; on the disk are also traces of opaque, fine radiating 

 lines, but these do not seem to be reflected in the sculpture ; hinge line narrow, 

 within the left valve three small cardinals, the anterior pair closely adjacent, the 

 other more distant; inner surface polished, pallial sinus large, ovate, horizontal, 

 extending in front of the middle of the shellj only slightly coincident with the 

 palUal line below. Lon. of shell, 34; of posterior end, 13; alt. 22; diam. of left 

 valve, 5 mm. 



U. S. S. "Albatross," station 2355, Gulf of Panama, in 182 fathoms, mud, 

 bottom temperature 54°.l F. U. S. N. Mus. 122,936. 



Only a single left valve was obtained. The most nearly related species is 

 M. {Psammotreta) aurora Hanley, which has a different hinge, and is a broader 

 sheU. 



Semelidae. 



CIJini^GIA SOWERBT. 



Cvimingia mutica Sowekbt. 



At Tome, Chile, from the mud upon the anchor, were obtained some fragments 

 and small specimens of a Curningia which are probably the young of C mutica. 



(Astheicodonta) 



Myacea. 



Myacidae. 



SPHENI4 TuRTON. 



The distinction between this genus and Mya is extremely slight. It has pro- 

 portionately shorter siphons, and the species recognized are all of small size, but 

 it seems impracticable to discover other differences and I am strongly tempted to 

 relegate it to Mya as a subgenus. 



Sphenia subequalis Dall, n. ep. 



Shell small, inequilateral, compressed, bluntly rounded at both ends, covered 

 by a yellowish periostracum ; beaks low, nearly median, being 3.25 mm. from the 



