384 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
anterior 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, off 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 Dat, n. sp. 
Plate 10, figures 3, 5. 
Shell thin, oval, polished, of a very dark olivaceóus tint, inequilateral, with 
a marked anterior basal gape; beaks low, eroded, inconspicuous, anterior, 
with a wholly external, elongated, chiefly opisthodetic ligament and no resilium ; 
anterior dorsal slope short, compressed, slightly 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- 
ing 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 the 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 Aguja 
Point, Peru, in 1036 fathoms, mud, bottom temperature 379.3 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 Darr, n. ep. 
Plate 17, figure 1. 
Shell brilliantly polished, smooth, with a pale, olivaceous periostraeum, inequi- 
lateral, subrectangular, with a strong, external, opisthodetic ligament and traces 
