VENERIDAE 



411 



1% to 2 inches in length, extremely close to Protothaca sta?mnea and 

 grata Sowerby (the latter's range is from the Gulf of California to Panama), 

 but differing from both in being much more elongate and more compressed. 

 Its lunule and small escutcheon are more distinct and quite smooth as com- 

 pared to those of stavnnea. The hinges are extremely similar. P. grata differs 

 in having tiny, distinct crenulations on the inside of the anterior dorsal 

 margin. T. seviideciissata Reeve appears to be the same as this introduced 

 species. Its colors are variable and commonly variegated. Alias T. bifurcata 

 Quayle 1938. 



Genus Compsomyax R. Stewart 1930 

 Co7npso7nyax subdiaphana Carpenter 

 Alaska to Lower California. 



Milky Pacific Venus 



Plate 3 if; figure 8ia, b 



1/4 to 2/4 inches in length, elongate-ovate, moderately inflated; beaks 

 anterior and pointing forward. Sculpture of fine, irregular, concentric lines 

 of growth, otherwise rather smoothish. Lunule poorly defined. 3 cardinal 

 teeth in each valve, the most posterior one in the right valve deeply split. 

 Color usually chalky-white, but younger specimens are yellowish white 

 and semi-glossy. Interior white. Dredged in soft mud from 5 to 25 fathoms. 

 Abundant in some Californian localities. Formerly placed in the genus 

 CI 677 jentia. 



Figure 82. Psephidia of the Pacific Coast, a-b, P. lordi Baird; c, P. nvctUs Dall. 



Both % inch. 



Genus Psephidia Dall 1902 

 Psephidia lordi Baird Lord's Dwarf Venus 



Figure 82a 



Alaska to San Diego, California. 



% inch in length, ovate, compressed or slightly fattened; beaks small; 

 sculpture of microscopic, concentric growth lines. 3 cardinals in hinge of 

 each valve. No laterals. On the dorsal margin there is a microscopic groove 

 parallel to the edge. Color whitish to greenish white, commonly with darker, 

 concentric color bands. Tiny young shells may be found inside the adult 

 clams in the summer and spring months. Common. 



