102 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
valve slightly smaller than the other, the body of the shell short-oval, 
the rostrum short, straight, abruptly truncate; sculpture of about fifteen 
radial threads which extend over the whole valve except the rostrum; 
incremental lines feeble. Length of anterior end, 5.5 ; of posterior end, 5; 
height, 7; diameter, 5 mm. (Dali.) 
It is smaller when adult and more coarsely sculptured than young 
C. planetica or balboa of the same size, much larger and more inflated than 
C. pectinata, calif'ornica or beringensis, all of which belong to the same 
group, and superficially are very similar except in size. (Dali.) 
Type in U. S. N. M., No. 333459. Type locality, Puget Sound. 
Range. Vancouver Island, British Columbia, to Puget Sound. 
Genus MYONERA Dali and Smith, 1886. 
Shell without cardinal or lateral teeth in either valve; with or without 
a buttress; fossette vertical or posteriorly directed, attached to the hinge 
by either edge; sculpture radiating or concentric. 
Type. Necera paucistriata Dali. 
Distribution. Coast of Oregon, the east coast of North America, and 
the West Indies. 
Myonera tillamookensis Dali, 1916. 
Proc. U. S. N. M., 52:407. 
Shell extremely thin, fragile, inflated, beaks nearly central (neglecting 
the rostrum), whitish, the anterior part of the shell with about twenty 
strong, rounded, concentric ripples which -cease posteriorly at the anterior 
border of the radial sculpture which includes four strong and about 
fifteen thread-like radial riblets extending from the beaks to the base, 
behind which is a short, blunt, concentrically feeble striate, truncate 
rostrum; base arcuate, hinge-line nearly straight, the right margin slightly 
overlapping the other. Length, 18; height, 12; diameter, 10 mm. (Dali.) 
Type in U. S. N. M., No. 107819. Type locality, Station 3346, off 
Tillamook Bay, Oregon, in 786 fathoms. 
Range. Known only from type locality. 
Genus LEIOMYA A. Adams, 1864. 
An anterior prominence or cardinal tooth in each valve, anterior and 
posterior laterals in the right valve, left valve without laterals. Cartilage 
in a posteriorly directed groove or fossette; surface smooth or concentri¬ 
cally sculptured. 
Type. Neara adunca Gould. 
Distribution. West Indies, California. 
