306 CALIFORNIA ACADEMY OF SCIENCES. 



evenly vt-ntricose; aperture oval; peritreme continuous; outer lip acute; inner lip not thickened; 

 umbilicus nearly obsolete. 



Dimensions. — Lonjj. 4.8 mm.; l.it. 2 mm.; body-whorl 2.5 mm.; aperture I mm.; dill. 

 22 degrees. 



This littU> frosli-vvator gastropod is (listingiiislial)U' hy it.s small size, tliin slid!, 

 very convox whorls ami coiitiiuioiis periLreine. >Spuciinens pronoun cod 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. 



J'leiatocene. — San Pedro (Arnold). 



Family LXXVI. CALYPTR.EIDiE. 



Genus Crucibulura Schumacher. 



Shell conical, more or less regular, with subcentral, subposterior, sharp ape.x; aperture basal, 

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

 the inner wall of the shell. 



Section Crucibulum, s. s. 



Distinguished from Dispotaa by having in the adult tin- whole margin of the internal cup 

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



Crucibulum rudis Brod. is a characteristic species. 



341. Crucibulum spinosum Sov:erbi/. 



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



Crucibulum spinosum S?i\., 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. Tryon, Man. Conch., Vol. VIII, p. 118, PI. XXXII, fig. 38, 1886. Cooper, 

 7th 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 Sby., =DispolcEa dumosa CoN. (young shell), ^=Crucibulum 

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

 Vol. III. 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 nn 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 au 

 old form. 



