ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 311 



thin; interior reddish brown (shows in all Pleistocene specimens examined), except for border equal 

 in width to the space between the deck and the rim, which is light colored; deck thin, with nearly- 

 straight edge; slight depression where deck joins shell on right side; deck curves upward at margin 

 where it joins shell, making the line of contact indistinct in most specimens, the deck merging 

 into the shell. 



Diniensions. — Long. 32 mm.; lat. 25 mm.; alt. 10 mm. 



This shell may be distinguished from C. rugoaa by its larger size, depressed 

 form, interior coloration, and by the indistinctness of the line of contact between the 

 deck and the shell. The deck of C. onyx is also joined to the shell nearer the rim 

 than is the deck of either C. rugosa or C. adunca. 



This specimen was identified by Dr. Dall. 



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

 in upper San Pedro series of Deadman Island, Los Cerritos, and San Pedro. Found 

 also in the Pleistocene at Spanish Bight and Pacific Beach, San Diego. 



Living. — Panama, Central America (Carpenter). 



Pleistocene. — San Pedro; San Diego (Arnold). 



349. Crepidula rugosa Nidtall. 



Crepidula rugosa Nutt., mss., Proc. Zool. Soc. , 1856, p. 224. Cpr., Brit. Assn. Rept., 1863, p. 654. 



Tryon, Man. Conch., Vol. VIII, p. 128, PL XXXVII, fig. 37, 1886. Keep, West 



Coast Shells, p. 76, 1892. 

 Crepidula onyx Sby. var. rugosa Nutt., Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 203. 



Shape of shell similar to C. onyx, but more arched; apex prominent, submarginal, sharp, 

 hooked, smooth, turned only slightly to one side; lines of growth irregular; surface rugose, and 

 quite glossy in some specimens; aperture oval; margin thin; deck deeply sunken in shell, and line 

 of contact with shell very distinct; edge of deck straight. 



Dimensions. — Long. 20 mm.; lat. 12 mm.; alt. 10 mrn.; aperture 15.5 mm. x 12 mm. 



Distinguishable from G. onyx by more prominent apex, which is further from 

 the margin than in the latter; by the deeper set deck and by the less prominent 

 lines of growth. Smaller than C. onyx. This specimen was identified by Dr. Dall. 



Found in lower San Pedro series of Deadman Island and San Pedro; and in 

 the upper San Pedro series of Crawfish George's, Deadman Island, San Pedro, Los 

 Cerritos, and Long Beach. 



Living. — Santa Barbara to San Diego (Cooper): Mexico to Peru ? (Cooper). 



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



Family LXXVII. AMALTHEID^. 

 Genus Hipponyx De France. 



Shell thick, obliquely conical, non-spiral; apex somewhat posterior and curved backwards; 

 muscular impression horseshoe-shaped; base of attachment shelly, secreted by the foot of the animal. 



Hipponyx cornucopice Lam. is a characteristic species. 



