232 BULLETIN OF THE 
Cryptodon sp. 
A broken left valve, Station 326, off Cape Fear, N. C., in 464 fathoms. 
Although only a fragment, this differs so decidedly in form and sculpture from 
any of the species known to me, that it seems worthy of description, Its out- 
line is much more angular than that of C. ovoideus Dall from the same locality. 
The ventral margin is too badly broken to judge of its outline, but the upper 
part of the valve is entire and shows an exceedingly high, narrow, angular, in- 
flated form, with a small though prominent umbo and very sloping dorsal 
margins. Beak small, curved well forward over an exceedingly small, slightly 
sunken lunule, bordered by an inconspicuous ridge. The postero-dorsal mar- 
gin is very long, straight (though strongly concave in an end view), and slop- 
ing, and is four and a half times the length of the lunular area. A single very 
deep narrow groove extends across the valve from the beak to the posterior 
ventral margin. In front and back of this there is a scarcely discernible un- 
dulation of the surface, and another equally slight one just back of the lunular 
ridge. Umbo nearly smooth and lustrous; the rest of the surface is roughened 
by the conspicuous, strongly curved lines of growth. Color, yellowish white. 
Interior bluish white, with a slightly lustrous frosted surface, which, under 
the microscope, appears covered with minute shallow pits. The exterior groove 
forms a conspicuous interior ridge. The ligamental groove is rather narrow, 
straight, sunken, running nearly the entire length of the postero-dorsal mar- 
gin. At the end of the ligament, just beneath the beak, there is a prominent 
angular tooth-like process. 
Length of lunular area, 2 mm.; of posterior dorsal margin, 9 mm. 
Diplodonta turgida Verrity and SmitH. 
Verriz, Trans. Conn. Acad., V. p. 569, pl. 58, fig. 42, 1882; VI. pl. 30, figs. 10, 
11, 1884. 
Fragments, Station 345, south of Martha’s Vineyard, in 71 fathoms. 
A rare species, only disunited valves of which have been found by the U.S. 
F. GC. from south of Martha’s Vineyard to off Cape eee N. C., in 27 to 
167 fathoms. 
A single valve, off Grenada, in 170 fathoms (Dall). 
Yoldia thraciformis (Srorer) Srrmp. 
Five dead specimens and one valve, Station 332, off Cape Hatteras, N. C., in 
263 fathoms. Twenty living and four dead, Station 336, off Delaware Ps in 
197 fathoms. 
A common species recorded by the U. S. F. C. from the Bay of Fundy 
and west of St. Peter’s Bank to off Cape Hatteras, N. C., in 16 to 906 fath- 
oms ; and by Mr. Whiteaves from the Gulf of St. Lawrence. 
1 Cryptodon ovoideus Dall, Proc. U.S. Nat. Mus., XII. p. 263 (no description), pl. 
14, fig. 3, 1889. 
