32 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
lunule long, narrow, just evident; escutcheon long, narrow, indented, well 
defined. Ventral margin arcuated, widest about the middle of the shell; a 
slight obsolete groove or channel anteriorly bordered by two obscure 
ridges, terminates in a slight waved indentation in the anterior ventral 
margin, about the middle of the anterior fourth. Posterior end rising 
obliquely, rounded truncate posteriorly, forming an angle of 90° with 
the hinge margin, and slightly upturned. Posterior dorsal slope slightly 
concave, anterior slightly convex, evenly rounded to the anterior end. 
Ligament pit large, roundly triangular. Teeth (anterior) 37, (posterior) 
17. Pallial sinus reaching before the umbones, which are x %5 of the 
whole length from the posterior end. Interior bluish white, with fine 
radiating lines. Exterior marked by lines of growth and obsolete radiat¬ 
ing lines; sculptured by sharp grooves, which, beginning near the middle 
of the shell with a slight wave toward the umbones, pass backward and 
downward across the lines of growth, rising a little and ceasing abruptly 
at a distance of about of the whole length from the posterior end. 
Long., 1.74; alt., .82; diameter, 7.2 in. (Dali.) 
Type in U. S. N. M. Type locality, St. Pauls Harbor, Kodiak Island, 
in 17 fathoms. 
Range. Okhotsk and Bering seas to Sitka, Alaska. 
Yoldia ensifera Dali, 1897. 
Plate 5, fig. 3, and plate 37, fig. 6. 
Nat. Hist. Soc . Brit. Col. Bull. No. 2:9; pi. 2, fig. 4. 
Shell large, thin compressed, with a brilliant olivaceous periostracum, 
usually showing darker and lighter zones; valves nearly equilateral, mod¬ 
erately convex, rostrate, subarcuate; sculpture of fine lines of growth more 
or less evident, and on the anterior two-thirds of the shell numerous 
irregularly fluctuating, distant, incised grooves (like those of Y. scis- 
surata) which are absent on the posterior third; base, arcuate, anterior 
dorsal profile rounded evenly from the beaks; a slight inward wave of 
the margin is visible anteriorly near the pedal gape; lunule absent; the 
escutcheon impressed, and the posterior dorsal margins of the valves, pro¬ 
jecting vertically, blade-like and slightly pouting; rostrum pointed, slightly 
recurved, beaks low, inconspicuous; valves internally whitish; pallial sinus 
deep, rounded; chondrophore wide, hardly projecting; teeth narrow, 
A-shaped, slender, about 30 in front of and 24 behind the chondrophore. 
Length, 35 ; height, 16; diameter, 6 mm. (Dali.) 
Type in U. S. N. M. Type locality, Vancouver Island, British 
Columbia. 
Range. Southeastern Alaska to San Diego, California. 
