ARNOLD — THE PALEONTOLOGY AND STEATIGKAPHY OF SAN PEDRO. 151 



Pliocene. — Santa Rosa; Twelve Mile House, San Mateo County; Kirker's 

 Pass, Contra Costa County; Monterey; San Fernando (Cooper) ; San Diego (Arnold). 

 Miocene. — West of San Jose; Foxin's, Santa Barbara County (Cooper). 



89. Tapes tenerrima Carpenter. 



Plate XIV, Fi<;. 6. 



Tapes lenerrima Cpr., Proc. Zool. Soc, 1856, p. 200; (jun.) ^=Vcnus rigida Gld., pars, {fide 

 Carpenter, Brit. Assn. Rept., 1863, p. 641.) Gabb, Pal. Cal, Vol. II, p. 97, 1869. 

 Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 267. Keep, West Coast Shells, 

 P- 157. fig, 136, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 188. 



Shell large and thin, oval, convex; surface sculptured by numerous low, sharp, concentric 

 frills, and numerous tine, rounded, crowded, radiating lines, these latter lines being almost obsolete 

 in some specimens; margin smooth, hinge long and narrow; three teeth in each valve, the anterior 

 two in the right valve and the middle one in the left valve prominently bifid; pallial sinus very deep 

 and rounded; no lunule. 



Dimensions. — Long. 86 mm.; alt. 63.5 mm.; diam. 34 mm. 



This is the largest and finest Tapnn found in these deposits, and is easily 

 distinguishable by its largo, thin, shallow shell and regular, oval outline. Specimens 

 identified by Dr. Dall. 



Rather rare in the upper San Pedro series of San Pedro, Los Cerritos, Crawfish 

 George's and Deadman Island. The specimen figured is from the upper San Pedro 

 series at San Pedro, and is now in the collection of Delos Arnold. Found also in the 

 Pleistocene at Barlow's ranch, Ventura, and at Spanish Bight, San Diego. 



Living. — Straits of Fuca to San Diego (Cooper). 



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

 (Arnold). 



Pliocene. — Santa Barbara (Cooper). 



Genus Saxidomus Conrad. 



Shell transversely oval, inequilateral, solid, ventricose; without lunule; umbones tumid; 

 teeth three or four, inequal, narrow, the central bifid; ligament very thick, elongated; muscular 

 impressions oval or rouuded, nearly equal; pallial sinus large, elongated, horizontal. 



Type, Saxidomus nuttallii (Con.). 



90. Saxidomus aratus Gould. 



Saxidomus araius Gld., Otia Conch., p. 168, 1862. Carpenter, Brit. Assn. Rept., 1863, p. 641. 



Keep, West Coast Shells, p. 183, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. 



XV, 1892, p. 188. 

 Tapes gracilis Gld., Pac. R. R. Rept, Vol. V., p. 333, PI. XIX, fig. 20, 1853. 

 Saxidomus gracilis, Gld., = Venus maxima Phil, (fide Gabb, Pal. Cal., Vol. II, 1869, p. 98). 



Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 263. 



