96 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Poromya leonina Dali, 1916. 
Plate 11, fig. 3. 
Proc. U. S. N. M., 52 : 406 . 
Shell large for the genus, mactriform, solid, inflated, transverse, with 
a dull olivaceous periostracum, darker, and concentrically wrinkled on the 
posterior dorsal area; surface smooth except for fine incremental lines 
and microscopic radial striube often obsolete; beaks high, slightly proso- 
ccelous, nearly central; base moderately arcuate, anterior end rounded, 
dorsal slopes nearly straight, a shallow radial depression on the posterior 
dorsal area, posterior end subtruncate; hinge weak, ligament deeply inset; 
hinge almost obsolete; margins entire, pallial sinus shallow, interior 
feebly iridescent white. Length, 27; height, 18.5; diameter, 14.6 mm. 
(Dali.) 
Type in U. S. N. M., No. 122564. Type locality, Station 3074, off 
Sea Lion Rock, coast of Washington, in 877 fathoms. 
Range. Known only from the type locality. 
Genus CETOCONCHA Dali, 1889. 
Shell differing from Poromya proper by the cartilage being almost 
external and the fossettes diminished in size and upturned, the external 
ligament consequently nearly obsolete; the dentition obsolete except the 
cardinal tooth of the right valve, which itself is sometimes absent in the 
adult, though observable in the young; other shell characters much as in 
Poromya. (Dali.) 
Type. Lyonsia bulla Dali. 
Distribution. West Indies, and southwest of Sitka, Alaska. 
Cetoconcha malespinae Dali, 1916. 
Proc. U. S. N. M., 52 : 407 . 
Shell small, very thin, with prominent prosocoelous beaks, a very pale 
yellowish olive periostracum, darker on the posterior dorsal area; in the 
right valve is a strong radial ridge near the posterior hinge line; surface 
otherwise smooth and almost polished except for extremely fine radial 
lines of minute granules only visible under a glass; shell very similar to 
Isocardia cor in form and outline on a very small scale; interior white, 
the hinge normal but weak. Length, 12.5; height, 10; diameter, 3.5 mm. 
(Dali.) 
Type in U. S. N. M., No. 212564. Type locality, Station 2859, south¬ 
west of Sitka Bay, Alaska, in 1569 fathoms. 
Range. Known only from the type locality. 
