ARNOLD — THE PALEONTOLOGY AND STRATKiRAPHY OF SAN PEDRO. 309 



Deadraan Island. Found in the Pleistocene at the bath-house, Santa Barbara; at 

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



Living. — Straits of Fuca to Santa Barbara; Mexico (Cooper). 



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

 Ventura; San Diego (Arnold). 



345. Crepidula dorsata Broderip. 



Crepidula dorsata Brod., Proc. Zool. Soc, 1834, p. 38. Cpr., Brit. Assn. Rept., 1863, p. 654. 



Gabb, Pal. Cal., Vol. II, p. 82, 1869. Trvon, Man. Conch., Vol. VIII, p. 127, 



PI. XXXVII, figs. 26-30; PI. XXXVIII, fig. 41, 18S6. Cooper, ytli Ann. Rept. Cal. 



St. Min., 1888, p. 236. Keep, West Coast Shells, p. 76, 1892. Dall, Trans. V/agner 



Inst. Sci., Vol. Ill, Part IV, 1892, p. 358. 

 Crypta dorsata Brod., H. & A. Adams, Gen. Rec. Moll., Vol. I, p. 369, 1853. 



Shell small, much depressed; apex curved to one side and upward, smooth on lip; surlace 

 sculptured with rough, rounded, radiating ridges, expanding and also increasing in number by inter- 

 callation toward the margin; aperture round; margin crenulated and thickened; deck partly detached, 

 thin, oblique, with pit at apex. 



Dimensions. — Diam. 10 mm.; alt. 3 mm. 



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

 series of Crawfish George's and Los Cerritos. 



Living. — Straits of Fuca to Mazatlan; Peru, South America (Coop^ir). 



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



Pliocene. — San Fernando (Cooper). 



346. Crepidula grandis Middendorff. 



Crepidula grandis Midd., Mai. Ross., Part II, p. loi, PI. XI, figs. 8, 9, 10, 1849. Cpr., Brit. 



Assn. Rept., 1863, p. 584. Gabb, Pal. Cal., Vol. II, p. 81, 1869. Tryon, Man. 



Conch., Vol. VIII, p. 127, PI. XXXVII, fig. 33, 1886. Cooper, 7th Ann. Rept. Cal. 



St. Min., 1888, p. 237. Dall, Trans. Wagner Inst. Sci., Vol. Ill, Part II, 1892, 



P- 358- 



Shell heavy, elevated obliquely fi-om an oval base; sides flattened; apex narrowed, curving 



nearly to side margin; surface sculptured by numerous fine lamellar lines of growth; deck long, 



thick (much thicker on side opposite from apex) and showing lines of growth on inner side, occupies 



over half of aperture, joins shell near margin. 



Dimensions. — Long. 80 mm.; lat. 50 mm.; alt. 45 mm.; aperture 60 mm. 



The rim, especially near the posterior end, shows the lamellar structure of the 

 shells. These shells have a very pronounced habit of growing one upon another 

 until the group sometimes numbers six or eight individuals. This species is easily 

 recognized by its size and thickness. 



Dr. Dall unites C. prrerupta Con. and C. princeps Con., but separates this 

 species from C. grandis Midd. It has been the writer's privilege to examine quite a 

 series of C. prcerupta Con. from the Astoria Miocene of Blakeley, Washington, and 



