152 CALIKOIINIA ACADEMY OF SCIENCES. 



Slicll larjjc, transversely elliptical, equivalve, inciiiiilatcral, convex, thick; iniibones tiinud, 

 anterior to niidille; anterior end evenly rounded; posterior end much more produced, havinj; a slight 

 tendency towanl bian^ulation; surface scul])tured with strong, elevated concentric lines, which in the 

 adult often have the prominence of concentric lamina; liganiental area external, wide, long, strong; 

 cardinal teeth four, anterior one long and narrow; p:illial sinus long, rather narrow, rounded extremity 

 near midiUe <.)f shell and im])ressed against tiie posterior adductor scar. 



Dimensions. — Long. 89 mm.; alt. 62 mm.; diam. 44 mm.; umbo to anterior extremity 

 30 mm. ; to posterior extremity 59 mm. 



i^pecimciis identilietl by Dr. J);ill. 



Kare in the lower San Pedfo series of Dcailniaii i>l;iinl; (1)1111111111 in liic u|i[ier 

 San Pedro series at. Deadman l.sland, Crawfish George's, Los Cerrilos and San Pedro. 

 Found also in the Pleistocene at Parlow's raiidi, Vcniiira, and at Tweiily-sixth Street, 

 S;iii Diego. 



lAr'uig. — Baiiiine.s Pay to San Diego (Cooper). 



Pkistoccnc. — Santa Barbara to San Diego (Cooper): San I'cdro; Hlakeley, 

 near Seattle, Wa.shington (Arnold): San Diego; Venttira (Arnold). 



Pliocene. — Kirker's Pass, Contra Costa County; Twelve Mile House, San 

 Mateo County; Santa Barbara, San Fernando (Cooper). 



Miocem. — Martinez; Walnut Creek, Contra Costa C'ounty; Santa Cruz; Santa 

 Inez, Santa Barbara County; Santa ^Monica (Cooper). 



Subfamily GEMMIN.E. 

 Genus Psephis Carpenter. 



Siiell thin, rounded or quadrangular, somewhat inflated; pallial sinus small; three elongated, 

 thin, cardinal teeth in each valve. 



Psephis lordi (Baird) is a characteristic si^ecies. 



91. Psephis salmonea Carpenter. 



Psephis salmonea CpR., Brit. Assn. Rept., 1863, p. 641. Cooper, 7th Ann. Rept. Cal. St. Min., 

 1888, p. 261. 



Shell very small, ovate trigonal, inequilateral; posterior end evenly rounded; jjosterior 

 dorsal margin rounded; in other ways resembles P. tantilla. 



Dimensions. — Long. 5 mm.; alt. 4 mm.; diam. 2.5 mm. 



Distinguishable from P. tantilla by smaller size and less trigonal outline. 

 Specimens examined showed no coloration. 



Rare in the lower San Pedro series at Deaihnan l.shind and San Pedro. 

 Found also in the Pliocene at Packard's Hill, ami in the Pleistocene at the bath- 

 house, Santa Barbara. 



Xivi^i^f.^Catalina Island (Cooper; Arnold): 10 fathoms (Arnold, 1901). 

 Pleistocene. — Santa Barbara (Cooper): San Pedro; Santa Barbara (Arnold). 

 Pliocene. — Santa Barbara (Arnold). 



