306 CALIFORNIA ACADEMY OF SCIENCES. 



evenly ventricose; aperture oval; peritreme continuous; outer lip acute; inner lip not thickened; 

 umbilicus nearly obsolete. 



Dimejisions. — Long. 4.8 mm.; lat. 2 mm.; body-whorl 2.5 mm.; aperture i mm.; defl. 

 22 degrees. 



This little fresh-water gastropod is distinguishable by its small size, thin shell, 

 very convex whorls and continuous peritreme. Specimens pronounced a new species 

 by Dr. Dall. Named in honor of Mr. Frank Stokes of Pasadena, California. 



Rare in upper and lower San Pedro series of San Pedro. The specimen 

 figured is the type, which is from the lower San Pedro series at San Pedro, and is 

 now in the United States National Museum. 



Pleistocene. — San Pedro (Arnold). 



Family LXXVI. CALYPTRiEID.E. 

 Genus Crucibulum Schumacher. 



Shell conical, more or less regular, with subcentral, subposterior, sharp apex; aperture basal, 

 with a central, internal, cup-shaped lamina, which is entire, and attached along a hue on one side to 

 the inner wall of the shell 



Section Crucibulum, s. s. 



Distinguished from Dispotcea by having in the adult the whole margin of the internal cup 

 free from|the shell, and the cup as a whole merely attached by a narrow strip of adhesion. 



Crucibulum rudis Brod. is a characteristic species. 



341. Crucibulum spinosum Sowerby. 



CalyptrcEa spinosa Sby., Gen. of Shells, PI. XXIII, figs. 4, 7, 1824. 



Criicibulum spinosmn Shy., Reeve, Icon. Conch., Sp. 10. Conrad, Pac. R. R. Rept., Vol. V, 

 p. 327, PI. V, fig. 46, 1856. Cpr., Brit. Assn. Rept., 1856, p. 323, PI. IX, figs. 3a, 3/; 

 id., 1863, p. 654. Gabb, Pal. Cal., Vol. II, p. 81, 1869; Geol. San Domingo, p. 241, 

 1873. Trvon, Man. Conch., Vol. VIII, p. 118, PI. XXXII, fig. 38, 1886. Cooper, 

 yth Ann. Rept. Cal. St. Min., 1888, p. 237. Keep, West Coast Shells, p. 77, fig. 62, 

 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 203. 



Crucibulum, auricula var. spinosum Shy., ^Dispotaa dumosa Con. (young shell), =Crucibi<lum 

 dumosum Tuomey & Holmes (young shell), {fide Dall, Trans. Wagner Inst. Sci., 

 Vol. Ill, Part 3, 1892, p. 350.) 



Shell conical, elevated; apex rather acute, slightly curved, smooth, subcentral; surface 

 ornamented with numerous rounded, radiating ridges, and sometimes with concentric rows of spires; 

 concentric lines of growth visible; a cup-shaped lamina is attached along a line on one side of the 

 interior of the shell; inner surface smooth; rim thin; aperture nearly circular. 



Dimensions. — Diam. 21 mm.; alt. 13.5 mm. 



The only member of this genus found in the San Pedro series of this locality. 

 Dr. Dall says that the recent specimens from California agree in the minutest par- 

 ticular with the Caloosahatchie fossils. This is probably a case of a survival of an 

 old form. 



