398 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 
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. Alt. 6; lat. of shell, 6 ; of hinge line, 5; max. 
diam. 4 mm. 
U. 8. S. “Albatross,” station, 3399, Gulf of Panama, in 1270 fathoms, hard 
bottom, temperature 369.4 F. U.S, N. Mus. 122,876. 
Quite similar to the variety orbiculata of the Arca pectunculoides, but less ex- 
tended laterally, less oblique, and with a finer and more delicate sculpture. 
Arca (Bathyarca corpulenta var.?) pompholyx Darr. 
Cf. Arca (Barbatia) corpulenta Smith, Challenger Rep., 1885, 13 (bivalves), 
p. 263, pl 17, figs. 5-bb. 
Smith's Arca corpulenta ranged from North Australia to Juan Fernandez 
Island, and on the west, northward to Celebes, in 200 to 2425 fathoms, thus cov- 
ering part of the range of the present shell, which differs from Smith's very full 
and careful description of 4. corpulentain the following particulars : The beaks are 
larger, fuller, and more conspicuous ; the sculpture is composed of narrow, flats 
smooth, concentric bands much wider than the radiating lirae, which are only vis- 
ible in the interspaces and do not nodulate the intersections; in comparing al 
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 dis- 
tinguishable varieties, as the specimens I have seen show variations. The present 
shell measures 23.5 mm. long; 26 high; diameter 29; hinge line 16.5, with 
the beaks 4.5 mm. from the anterior end of the hingeline, "The hinge in this 
specimen has seven anterior and five posterior teeth with an edentulous gaP 
10 mm. long between them, but, another specimen of the same species has the 
entire hinge line denticulate. "The stations are as follows : 
Station. Region. Fathoms. Bottom temp. Character of bottom. 
*4390 off California 2182 359.0 mud 
4396 E y 2228 359.0 dj 
47090 Mid Pacific 2035 359.8 ooze 
4721 5 de 2084 859,0 " 
4740 E n 2422 849.2 2 
*U, S. N. Mus. 110,704. 
Barbatia Gray. 
CUCULLARIA Conran. 
Cucullaria Conrad, Amer. Journ. Conch., 1869, 5 p. 97; type, Arca heterodonta Des- 
hayes, Eocene. 
I pointed out in 1898 that the forms included by Conrad in his genus Cucul- 
laria were probably not closely related to Macrodon Lycett, to which their hinges 
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