386 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
The pallial sinus is notable in that the greater part of its basal scar is identical 
with the pallial line itself, whereas in most of the Malletinae the sinus tends to 
slope obliquely upward. 
Malletia (Minormalletia) benthima Dax, n. sp. 
Plate 15, figures 1, 2. 
Shell small, thin, earthy, covered with a polished, thin, grayish periostracum ; 
very inequilateral, bluntly rounded in front and behind; beaks pointed, recurved, 
prominent; situated at the anterior third; surface smooth, except for lines of 
growth aiid very sparse, faint, radial striations which appear confined to the peri- 
ostracum ; posterior hinge line and base nearly parallel; ligament very delicate, 
amphidetic but mostly behind the beaks; resilium minute, obscure, not inter- 
rupting the line of teeth; anterior teeth 12-13, posterior 17-18, small and closely 
crowded}; interior earthy, polished, the muscular scars pronounced, small; pallial 
sinus large, deep, rounded behind, reaching nearly to the middle of the shell, 
rising obliquely from the entrance; no lunule or escutcheon. Beaks in front of 
the posterior end, 6.5; anterior end of sinus, 4.5; total length, 9.5; alt. 5.3; 
diam. 4.0 mm. 
U.S. S. “ Albatross,” station 3417, off Acapulco, Mexico, in 493 fathoms, 
mud, bottom temperature 40°.6 F. U.S. N. Mus. 122,927. 
A very plain and simple but rather peculiar looking species. 
NEILO A. Apams. 
Malletia ‘Nelro) goniura Dat. 
Plate 18, figure 6. 
Malletia goniura Dall, Proc. U. S. Nat. Mus., 1889, 12, p. 251, pl. 10, fig. 10. 
Shell extremely thin and fragile, translucent whitish, covered with a rather 
dark olive periostracum, smooth and polished; beaks low, adjacent, nearest the 
anterior end of the shell, with a linear lunule and escutcheon, a long and strong 
external ligament but no internal resilium; anterior dorsal slope arcuate, short, 
passing insensibly into the curve of the evenly rounded anterior end; posterior 
longer, straight, ending in an obtuse angle at the posterior truncation; a single 
elevated small thread or keel extends from each beak to the lower posterior 
margin of the valve, above which the valve is somewhat excavated; the upper 
border of this trough or excavation is slightly prominent, though not indicated 
by a keel, and the margin between the radial thread and this prominence is 
somewhat concave, produced at the end of the prominence and thence obliquely 
truncate to the dorsal margin, which is compressed; the posterior end of the 
shell, except for the undulation mentioned, is abruptly truncate and meets the 
