10 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
except for a short distance beyond the edge of the valves; valves very 
inequilateral, posterior end very short, hinge line nearly straight, the 
sulcus for the ligament nearly parallel with the hinge line, and nymph 
inconspicuous so that on a casual glance one might suppose there was 
none; beaks not raised; the hinge line below them thickened and flat, 
radially striated; anterior hinge line straight, thin; valves widest at the 
anterior part of the valve with 6 or 7 strong radial channels, the inter¬ 
spaces wider and often with margins a little raised or with slightly 
elevated border; beyond the channelled area there are a few faint radial 
furrows and a perfectly smooth unfurrowed space in the middle of the 
valve; posterior slope straight, furrow for the ligament long, deep and 
wholly external; there is a wide triangular smooth space, in front of which 
are five or six channels radiating to the margin, much more shallow than 
those at the anterior end and defined chiefly by shallow furrows at each 
side of the obsolete channel and the raised margins of the wide inter¬ 
spaces; interior chalky, the anterior muscular impression feeble, the 
posterior stronger and ovate: Length of the valve, excluding perio- 
stracum, about 95; height, 30; and diameter, 25 mm. The species reaches 
a length of more than 150 mm. (Dali). 
Type in U. S. N. M. No. 106885. Type locality, U. S. S. Albatross 
station 3360, Gulf of Panama, in 1672 fathoms, sand. 
Range. Tillamook, Oregon, to Aguja Point, Peru. 
Subgenus Petrasma Dali, 1908. 
Solemya panamensis Dali, 1908. 
Plate 9, fig. 4. 
Bull, of Comparative Zoology, 43 :365. 
Shell thin, elongate-oval, the posterior end more pointedly, and the 
anterior end more bluntly, rounded; periostracum brown, brilliantly 
polished, recurved on the margins of the valves, not produced into long 
processes, though more or less broken up outside of the margins; anterior 
part of the shell radiately marked with 8 or 9 obscure rays, which are 
more crowded in front and dorsally; the middle of the valve with sparse 
rays, the posterior part having 6 or 7 more closely adjacent, followed by 
a smooth unradiated area behind the beaks and above a line drawn from 
them to the middle of the posterior end of the valve; beaks flat, with a 
lozenge shaped area of ligament visible behind them; interior bluish, 
translucent; the chondrophore strong, projecting obliquely backward in 
front of the posterior adductor scar; muscular impression rather obscure; 
interior of the valves faintly radiately striated. Length of valve exclusive 
of the periostracum, 39; height, 150; diameter, 8; the beaks in front of 
the posterior end 14 mm. (Dali). 
