384 bulletin: museum of comparative zoology. 



aaterior dorsal margin evenly arcuate, posterior straighter, both ends rounded, 

 the posterior more bluntly ; posterior depressed ray obsolete, anterior wanting, 

 though in its place are three or four very faint radial striae ; base evenly arcuate, 

 interior earthy, white, pallial sinus large, rounded behind, below mostly coinci- 

 dent with the pallial line; hinge line short with a wide gap under the beaks, three 

 anterior and twenty-four posterior minute crowded teeth ; beak low, pointed, 

 opisthogyrate ; no lunule or escutcheon. Length of shell, 26 ; of anterior end, 

 15 ; alt. 17; diam. 6 mm. 



U. S. S. " Albatross," station 2772, oif Cape Virgins, in 31 fathoms, sand, and 

 2778, Straits of Magellan, in 61 fathoms, mud, bottom temperature 47°. 9 F. 



The truncation behind, the coalescent pallial sinus, and the compressed form 

 separate it from the other species. 



Malletia peruviana Dall, n. sp. 



Flat« 10, figures 3, 5. 



Shell tliin, oval, polished, of a very dark olivaceous tint, inequilateral, with 

 a marked anterior basal gape; beaks low, eroded, iuconspicuous, anterior, 

 with a wholly external, elongated, chiefly opisthodetic ligament and no resilium ; 

 anterior dorsal slope short, compressed, sliglitly arcuate ; posterior straight, much 

 longer, compressed ; no lunule or escutcheon ; anterior end attenuated, roundly 

 pointed, posterior broader, rounded, with a feebly impressed ray from the beaks end- 

 iug in an inconspicuous insinuation of the posterior lower margin ; surface smooth 

 except for this ray and incremental concentric slight undulations ; interior bluish 

 white, porcellanous ; muscular scars distinct, pallial sinus small and very shallow, 

 deepest near the adductor scar ; a strongly impressed dorsally concave arcuate 

 linear impression extending backward and upward from the anterior adductor scar 

 into the back part of tlie umbonal cavity ; hinge with small and crowded not 

 always clearly differentiated teeth, anterior about ten, posterior about thirty-three ; 

 valve margins entire. Lon. of shell, 28 ; of part anterior to the beaks, 9 ; alt. 

 16.5 ; diam. 9.5 mm. 



U. S. S. "Albatross," station 4654, N. 68° W., twenty-four miles from Agiija 

 Point, Peru, in 1036 fathoms, mud, bottom temperature 37''.3 F. U. S. N. Mus. 

 110,574. 



The species is remarkable for its almost blackish color and extremely shallow 

 pallial sinus, which does not extend in front of the posterior adductor scar; the 

 anterior end is unusually short and almost pointed. 



Malletia truncata Dall, n. sp. 



Plat« 17, figure 1. 



Shell brilliantly polished, smooth, with a pale, olivaceous periostracum, inequi- 

 lateral, subrcctaiigular, with a stroug, external, opisthodetic ligament and traces 



