46 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Type in Museum Cuming. Type locality, Gulf of Tehuantepec, Cen¬ 
tral America. 
Range. San Diego, California, to the Gulf of Tehuantepec. 
SECTION BATHYARCA Kobelt, 1891. 
Area nucleator Dali, 1908. 
Bull. Museum Comp. Zool., 18, No. 6:397; pi. 18, fig. 9. 
Shell small, plump, subglobular, inequilateral, white, with a dense 
villous periostracum; beaks full, prominent, adjacent, overhanging a long 
narrow amphidetic area; anterior part of the straight hinge line shorter than 
the posterior, each making an angle with the beginning of the valve 
margin which forms a slightly oblique subcircular arc, the posterior end 
being more rotund; sculpture very and subequally recticulate, the radial 
and concentric raised lines alike bearing long purpuraceous fringes of 
periostracum; hinge line not quite as long as the shell, the anterior part 
carrying six radiating minute teeth, the posterior part eight, which are 
somewhat more nearly horizontal; interior of the valve smooth, whitish, 
margins entire. Length, 6; height, 6; hinge line, 5 ; diameter, 4 mm. (Dali.) 
Type in U. S. N. M., No. 122876. Type locality, Station 3392, Gulf 
of Panama, in 1270 fathoms. 
Range. San Diego, California, to Panama. 
Area pompholyx Dali, 1908. 
Bull. Comp. Zool., 43:398. 
Differs from A. corpulenta in that the beaks are larger, fuller, and 
more conspicuous; the sculpture is composed of narrow, flat, smooth, con¬ 
centric bands much wider than the radiating line, which are only visible 
in the interspaces and do not nodulate the intersections; in comparing an 
umbonal view of the present shell with the figure in the Challenger Report, 
the beaks of the specimen are much nearer the anterior end of the hinge 
line than in the figure. These lead me to think that the two may be distinct, 
or at least distinguishable varieties, as the specimens I have seen show 
variations. Length, 23.5; height, 26; diameter, 22; hinge line, 16.5; with 
the beaks, 4.5 mm. (Dali.) 
Type in U. S. N. M., No. 110704. Type locality, off Santa Barbara, 
California. 
Range. Off Santa Barbara, California, to the Galapagos Islands, 
deep water. 
Family PINNIDJE. 
Genus ATRINA (Gray) Adams, 1857. 
Shell with the apical portions of the valves entire. (Gray.) The 
valves unisulcate or without the median carina, and the internal nacreous 
