284 CALIKOUNIA ACADKMV OF SCIENCES. 



[S. D.] Odostomia (Chrysallida) diegensis IK .( IL, sji. iiov. 



I'l.ATK I, Fid. 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 I'ourth, and twenty-two the 

 penultimate whorl; these ribs pass faintly over the well-rounded ,j)eriphery of the last whorl to the 

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

 shows an additional one; these ridges are not quite as broad as the axial ribs, but extend ])r<jminently 

 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; ajjerlure 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 columcllir 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 deposits at San Diego. The type has seven post-nuclear whorls. 



Section Oscilla A. Adams. 



Oscilla A. Adams, Froc. Zool. Soc, 1867, p. 310. Type, Odostomia {Evalca) 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. 



l'i..*TF. I, Figs. ."! anh 3a. 



Odostomia ( Evalea) csquisculpta 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. 



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



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

 collected at Cape St. Lucas, Lower California. 



This species occurs quite abundantly a.s 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 type is an immature specimen. One specimen comprising seven post- 

 nuclear whorls measures: long. 5 mm.; diam. 1.8 mm. 



