284 CALIFORNIA ACADEMY OF SCIENCES. 



[S. D.] Odostomia (Chrysallida) diegensis D. I- B., sp. nov. 



Pl.ATK I, Fifi. 8. 



Shell elongate-conic, dingy white; nuclear whorls decollated; post-nuclear whorls flattened, 

 contracted at base and strongly shouldered at the summit; suture undulate, profoundly channeled; 

 about seventeen very strong, rounded, axial ribs cross the third and fourth, and twenty-two the 

 penultimate whorl; these ribs pass faintly over the well-rounded periphery of the last whorl to the 

 umbilical region; the first five whorls are encircled by four strong, spiral ridges, while the penultimate 

 shows an additional one; these ridges are not quite as broad as the axial ribs, but extend prominently 

 over them and the intercostal spaces; base ornamented by about ten spiral ridges of weaker char- 

 acter than those of the spire, and by the faint extensions of the axial ribs; aperture suboval, decidedly 

 produced and flaring at the junction of the outer lip with the columella (outer lip fractured in all 

 our specimens); columella somewhat twisted and reflexed, a bit being broken away at the umbilical 

 region in the type, disclosing a small umbilical chink which is opposite to the strong columellar fold; 

 a heavy callus connects the posterior angle of the aperture with the columella. 



Dimensions. — Long. 4 mm.; diam. 1.6 mm. 



The seven specimens of this species in our collection all come from the post- 

 Pliocene dejjo.sits at San Diego. The type has seven post-nuclear whorls. 



Section Oscilla A. Adams. 



Oscilla A. Adams, Proc. Zool. Soc, 1867, p. 310. Type, Odostomia {Evalea) lirata A. Ad. 



Odostomias having strong spiral ribs, the spaces between which are ornamented by numer- 

 ous fine, raised, axial threads. 



[S. D.j Odostomia (Oscilla) aequisculpta Carpenter. 



Plate I, Figs. .S and 3«. 



Odostomia (Evalea) eequisculpta Cpr., Ann. Mag. Nat. Hist., 3d Ser., Vol. XIV, 1864, pp. 46, 47. 



Shell small, quite solid, elongate-ovate, subdiaphanous to white; nuclear whorls three, 

 obliquely one-third immersed; post-nuclear whorls rounded, separated by a prominent suture and 

 ornamented by about five fairly strong and rounded, subequally spaced spiral ridges on the second, 

 and six above the periphery on the penultimate whorl; the base of the last whorl is similarly sculp- 

 tured, the striations becoming fainter near the columella; the depressed spaces between the revolving 

 ridges are beautifully, closely crossed by fine axial riblets; periphery of the last whorl well rounded; 

 aperture large and effuse at base, posterior angle acute, outer lip thin, somewhat arcuate; columella 

 stout, provided with a small fold near the umbilical chink; a faint callus unites the posterior angle of 

 the aperture with the upper end of the columella; the external sculpture is apparent within the aper- 

 ture by transmitted light. 



Dimensioyis. — Long. 2 mm.; diam. 1.2 mm. 



The specimen here described and figured is Dr. Carpenter's type. It was 

 collected at Cape St. Lucas, Lower California. 



This species occurs quite abundantly as a recent form, ranging from San 

 Pedro, California, to Cape St. Lucas. It is also found in the post-Pliocene deposits 

 of San Diego. 



The tyjie is an immature specimen. One specimen comprising seven post- 

 nuclear whorls measures: long. 5 mm.; diam. 1.<S mm. 



