CLASS PELECYPODA 
95 
Subgenus Dermatomya Dali, 1908. 
Poromya tenuiconcha Dali, 1913. 
Plate 54, figs. 24 to 26. 
Proc. U. S. N. M., 45:596. 
Shell small, thin, olivaceous, the pearly luster showing through the 
periostracum; equivalve, inequilateral, anterior end shorter, rounded in 
front; posterior end longer, roundly truncate; beaks prominent, proso- 
coelous, with a marked but uncircumscribed depression in the lunar 
region in front of them; interior pearly, brilliant; margins simple, sharp; 
hinge in the left valve with a small internal resilium seated on an incon¬ 
spicuous oblique chondrophore, with a notch immediately in front of it, 
into which fits a projecting denticle on the corresponding part of the 
opposite valve. Length of shell, 16; anterior portion, 6; height, 13; 
diameter, 10 mm. (Dali.) 
Type in U. S. N. M. Type locality, off Monterey Bay, in deep water. 
Range. Alaska Peninsula to the Coronado Islands, Lower California, 
in deep water. 
Poromya buttoni Dali, 1916. 
Proc. U. S. N. M., 52:406. 
Shell small, rounded-quadrate, plump, thin, yellowish olive, hardly 
polished, smooth, with iridescent reflections from under the periostracum 
when fresh; beaks nearly central, not prominent, hinge teeth normal, 
strong; interior bluish white, margins entire, pallial sinus shallow. Length, 
9.8; breadth, 8; diameter, 6 mm. (Dali.) 
Type in U. S. N. M., No. 194309. Type locality, Station 3670, Mon¬ 
terey Bay, in 581 fathoms. 
Range. Known only from type locality. 
Poromya beringiana Dali, 1916. 
Proc. U. S. N. M., 52:406. 
Shell large, thin, plump, inequilateral, anterior end shorter, base 
arcuate, anterior end rounded, posterior dorsal slope first convexly slightly 
arcuate, then rounded obliquely subtruncate to meet the basal curve; 
beaks prominent, 7 mm. behind the anterior end; surface smooth, except 
for faint incremental irregularities, iridescent under a pale olive, polished 
periostracum; beaks slightly prosocoelous, hinge weak, the teeth minute, 
the ossiculum well developed; interior whitish, the pallial sinus very 
shallow. Length, 20; height, 14; diameter, 12 nun. (Dali.) 
Type in U. S. N. M., No. 205899. Type locality, Bowers Bank, Bering 
Sea, in 557 fathoms. 
Range. Aleutian Islands to Tillamook, Oregon. 
