176 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
tions, and by a few, distant, lines of growth. Color of young shells 
translucent and often opalescent white or whitish. The lower portion of 
adult shells, when in good condition, is covered with a thin, pale ashen 
gray epidermis, and the shells themselves are often tinged with a pale 
grayish or brownish hue. Right valve with two minute, widely diverging, 
cardinal teeth; left valve with a single, very small, narrowly triangular 
tooth, which under the lens appears to be grooved down the middle; 
lateral teeth obsolete or nearly so. Pallial sinus profound, rounded at its 
extremity, and reaching beyond the center of the valve. Length of an 
adult, 6 lines; height of same, 4 y 2 lines; thickness, 3 lines. 
Type in Ottawa. Type locality, Virgo Sound, Queen Charlotte Islands, 
British Columbia. 
Range. Arctic Ocean to Puget Sound. 
Macoma liotricha Dali, 1897. 
Plate 22, fig. 8. 
Nat. Hist. Soc. Brit. Coll. Bull., 2:12; pi. 1, fig. 21. 
Shell large, thin, somewhat inflated, with a polished straw-yellow 
periostracum, and rather coarse concentric lines of growth; valves nearly 
equilateral, the ligament strong, external; base rounded evenly into the 
rounded anterior end, posterior end bluntly pointed with two faint radial 
plications hardly indenting the margin; valves gaping a little dorsally, 
in front of the beaks; left valve slightly smaller than the right, beaks 
small and low; internally chalky white, the pallial sinus deep, roughly 
triangular, slightly large in the left valve, cardinal teeth thin, feeble, often 
obsolete or eroded, two in each valve. Length, 45; height, 34; diameter, 
16 mm. (Dali.) 
Type in U. S. N. M. Type locality, British Columbia. 
Range. Aleutian Islands and Shumagin Islands, Alaska, to British 
Columbia. 
Macoma expansa Carpenter, 1865. 
Suppl. Rep. Brit. Assoc., p. 369. Proc. Acad. Nat. Sci. Phila., 1865, p. 56. 
M. t. “M. proximce” simili sed majore, multo tenuiore; antice minus, 
postice plus expansa, regulariter excurvata; t. jun. subdiaphana, subepi- 
dermidem tenuem, stramineam, subnacrea; t. adulta alba, nitida; dentibus 
cardinalibus ii. —i. minimis, haud bifidis; sinu palii valva altera per tres 
quadrantes; altera per quinque inter septem partes interstitii porrecto. 
Long. 1.55; lat. 1.13; alt. .5. (Carpenter.) 
Scars like lata and calcarea in Mus. Cuming, but teeth not bifid, very 
thin, glossy. Scarcely differs from lata Desk. (Carpenter.) 
Type locality, Puget Sound. 
Range. Puget Sound to La Jolla, California. 
