310 CALIFOBNIA ACADEMY OF SCIENCES. 



it is his opinion, also, that this species is distinct from C. grandis. Two specimens in 

 the upper San Pedro series of Deadman Island. Found also in the Pliocene at 

 Pacific Beach, San Diego. 



Living. — Kamtschatka; Hakodate, Japan; Okhotsk (Carjienter). 



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



Pliocene. — Santa Rosa; Kirker's Pass; Santa Barbara; San Fernando; San 

 Diego well (Cooper): Alpine Creek, San Mateo County; Stanford University; San 

 Diego (Arnold). 



Miocene — Toraales, Marin County; Walnut Creek, Contra Costa County; 

 Foxin's and Santa Rosa Island, Santa Barbara County (Cooper). 



347. Crepidula navicelloides Nuttall. 



Crepidula navicelloides NuTT., Jay's Cat., No. 3035, 1835. Cpr., Brit. Assn. Rept., 1863, p. 654. 



Gabb, Pal. CaL, Vol. II, p. 82, 1869. Tryon, Man. Conch., Vol. VIII, p. 126, 1886. 



Cooper, 7th Ann. Rept., Cal. St. Min., 1S88, p. 237. Keep, West Coast Shells, p. 76. 



fig. 61, 1S92. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 203. 

 Crepiditla nimnnaiia Gld., Proc. Bost. Soc. Nat. Hist., Vol. II, 1846, p. 60; Wilkes' Expl. Exped., 



Vol. XII, p. 377, fig. 480, 1852. 

 Crepidula explanata Gld., Mex. and Cal. Shells, p. 4, PI. XIV, fig. 7, 1853; Proc. Zool. Soc, 1856, 



p. 205. 



This shell varies greatly in shape, due to the surface on which it grows. 

 Specimens showing an easy gradation from the circular, flat variety, C. nummarla, 

 through the tyj^ical, oblong, Hat, C. navicelloides, to the elongated, curved variety, 

 C. explanata, have been found in the upper San Pedro series of San Pedro. This 

 sjiecies may be distinguished from the other members of this genus by its flat or 

 dor,¥ally concave appearance, and by the way in which the deck is raised in the 

 center to allow body space between it and the inner surface of the shell. Repre- 

 sentatives of the above forms were identifled by Dr. Dall as this species. 



Rare in the lower San Pedro series of Deadman Island; and in the upper San 

 Pedro series of Crawfish George's, Los Cerritos, San Pedro, and Deadman Island. 

 Found al.so in the Pleistocene at the bath-house, Santa Barbara. 



Living. — Alaska to San Diego (Cooper). 



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



Pliocene. — San Diego well (Dall). 



348. Crepidula onyx Sowerby. 



Crepidula onyx .Sby., Genera of Shells, No. 23, fig. 2, 1824. Cpr., Proc. Zool. Soc, 1856, p. 225; 

 Brit. Assn. Rept., 1856, p. 323. Tryon, Man. Conch., Vol. VIII, PI. XXXVII, fig. 37; 

 PI. XXXVIII, figs. 43-50; PI. XXXIX, fig. 59, 1886. 



Shell ovate, generally irregular, low arched, strong; apex small, marginal, sharp and turned 

 to one side; surface marked by concentric lamellar lines of growth; aperture irregularly ovate; rim 



