ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 153 



92. Psephis tantilla Gould. 



Plate XIII, Fig. 5. 



Venus tantillus Gld., Bost. Jour. Nat. Hist., Vol. VI, 1853, P- 906, PI. XV, fig. 10. 



TrigoJiJa ianiilla Gld., Carpenter, Proc. Zool. Soc, 1856, p. 201. 



Psephis tantilla Q\.v>., Carpenter, Brit. Assn. Rept., 1S63, p. 640; =Venus rysonia Gabb {Jide 

 Gabb. Pal. Cal., Vol. II, p. 96, i86g). Cooper, 7th Ann. Rept. Cal. St. Min., 1888, 

 p. 261. Keep, West Coast Shells, p. 186, 1892. Williamson, Proc. U.S. Nat. Mus., 

 Vol. XV, 1S92, p. 188. 



Shell small, ovate-trigonal, inequilateral; beaks acute, slightly anterior to center; surface 

 smooth or faintly waved with distant, concentric furrows; the dorsal margins are nearly straight, and 

 meet at the apex in a right angle, but the posterior side is a fourth longer than the anterior; the 

 anterior basal angle is well rounded, while the posterior is acute; basal margin gently curved; hinge 

 area short, wide; three prominent, elongated cardinal teeth in each valve. 



Dimensions. — Long. 10 mm.; alt. 8 mm.; diam. 4.9 mm. 



Somewhat re.sembles a very small Tivela crassaielloides. Some show original 

 purple spot on posterior end. Specimens identified by Dr. Dall. 



Rather common in the lower San Pedro series at Deadraan Island and San 

 Pedro; rarer in the upper San Pedro series at Deadman Island, Los Cerritos, and 

 San Pedro. The specimen fii^ured is from the lower San Pedro series at Deadman 

 Island and is now in the collection of Delos Arnold. 



Living. — Straits of Fuca to Catalina Island (Cooper). 



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



Family XXVIII. COOPERELLID.E. 



Genus Cooperella Carpenter. 



Shell small, thin, smooth, or concentrically striate or undulate, equivalve, nearly equilateral, 

 with entire margins; ligament long; resilium short; hinge plate narrow, carrying two right and three 

 left subumbonal, divaricating, short cardinal teeth; laterals none; pallial line narrow, with an 

 ample sinus. 



Type, CEdalia suhdiaphnna (Carpenter). 



93. Cooperella subdiaphana Carpenter. 



Plate XIII, Fig. ]. 



CEdalia subdiaphana Cpr., Brit. Assn. Rept., 1863, p. 639; Jour, de Conch., Vol. XII, 1865, p. 134. 



QLdali7ia subdiaphana Cpr., Proc. Cal. Acad. Sci., Vol. Ill, 1866, p, 208. 



Cooperella subdiaphana Cpr., Dall, Trans. Wagner Inst. Sci., Vol. Ill, Part 5, 1900, p. 1062. 



Shell small, subquadrangular, subequilateral, convex, very thin and fragile; posterior extremity 

 evenly rounded; anterior extremity rounded near base; surface smooth except for incremental lines; 

 beaks slightly raised, sharp, prominent; two narrow, tall, sharp, bifid teeth in left valve, three in 

 right; pallial sinus very large. 



Dimensions. — Long. 12 mm.; alt. 9 mm.; diam. 6 mm. 



( 20 ) January 8, 1903. 



