18 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
anterior end rounded; the posterior angularly rostrate, the extreme end 
slightly recurved; anterior and posterior slopes nearly equal, the former 
a little convex, the latter slightly concave, the base convexly arcuate; 
lunule not defined, represented by a lanceolate narrow space, longitudinally 
striated; escutcheon similarly impressed, broadly lanceolate, bounded in 
each valve externally by a stout keel, the opposite margins hardly pouting 
in the median line; beaks low, and adjacent; sculpture of the disk com¬ 
posed of numerous concentric ridges, less arcuate than the incremental 
lines and separated by wider interspaces; more adjacent near the anterior 
end of the shells. An obscure radial ridge extends from the beaks toward 
the anterior end of the base. Interior polished, bluish, with entire margin. 
Ligament small, wholly internal. Hinge-teeth small, V-shaped, number¬ 
ing 16 anterior (of which 6 are small and crowded), and 14 posterior 
(of which 6 are very small), separated by the ligamentary pit, which is 
small and not projecting. Length, 9.2; of beaks behind the anterior 
margin, 4.2; maximum height, 6; maximum diameter, 5 mm. (Dali.) 
Type in U. S. N. M. Type locality Barkley Sound, Vancouver 
Island, British Columbia. 
Range. Queen Charlotte Islands, British Columbia, to Santa Barbara, 
California. 
Leda oxia Dali, 1916. 
Proc. U. S. N. M., 52:395. 
Shell minute, rounded in front, very acute behind, the valve ending 
in a sharp point; base arcuate, beaks low, subcentral, dorsal slopes nearly 
straight; sculpture of regular, equal concentric ridges with subequal 
interspaces, a depressed ray from the beak to the base anteriorly, a deeply 
impressed, concentrically striated escutcheon bordered by a rounded keel; 
lunule linear; about eight teeth on either side of a minute resilifer. Length, 
45; height, 3; diameter, 1 mm. (Dali.) 
Type in U. S. N. M., No. 214848. Type locality, Station 2901, off 
Santa Rosa Island, California, in 48 fathoms, muddy bottom. 
Range. Santa Rosa Island to the Gulf of California. 
Leda liogona Dali, 1916. 
Proc. U. S. N. M., 52:396. 
Shell small, light yellowish, concentrically sculptured with prominent 
elevated ridges with wider interspaces, except on the beaks where the 
prodissoconch is relatively large and perfectly smooth, the concentric 
sculpture commencing abruptly; beaks low, and about 3 mm. from the 
anterior end; base slightly arcuate, dorsal slopes direct, rostrum abruptly 
truncate; posterior dorsal area with two obscurely elevated rays over 
which the concentric sculpture is higher, but it becomes reduced to 
