NEOZOIC INVERTEBRATES 119 



basal margin of the aperture arcuate, not advancing as far as the 

 upper margin, which is oblique and anteriorly extended at the suture. 

 Height 13 to 20, diameter of base about 25 mm. 



Localities. Popof Island, 3372, 3563, also in the Crepidula bed 

 at Unga Island. 



This is one of the most abundant species among the shells from 

 Popof Island, and like most limpets quite variable in form. It can be 

 distinguished from its nearest congener, T. simplex Gabb, from the 

 Miocene of California, by the convex whorls, as the slope from the 

 apex of T. simplex to the periphery of the base is nearly a right line. 



Crepidula ungana sp. nov. 



rl. x, figs. 8, 9. 



Shell about the size of C. fornicata Lam., ovate, vertically some- 

 what compressed, having about a whorl and a half ; surface rudely 

 and irregularly concentrically sculptured by the incremental lines, 

 without spines or spiral sculpture ; apex small, narrow and recurved 

 to half the height of the shell above the base, its nuclear part pointing 

 nearly vertically ; aperture rather narrow, wider in front, the colu- 

 mellar margin somewhat reflexed below the spire. Maximum length 

 of shell 38, width 25, height 18 mm. 



Locality. Miocene bed at Coal Bluff, Unga Island, in very great 

 abundance, giving the name of Crepidula bed to this particular stratum. 



This species was long identified with Crepidula prosrupta Conrad, 

 from the Miocene of Astoria, very badly figured in the Geology of the 

 Wilkes Exploring Expedition (pi. 19, figs. 9, 10, 1849), an internal 

 cast of which was later named Crypta rostralis by Conrad. 



A comparison however with Conrad's type shows that the two 

 species are distinct, the narrow recurved apex of the Unga shell being 

 a specially strong character. The Astoria species is also more capa- 

 cious and convex. 



Neverita sp. 



Locality. Popof Island, 3372. 



Very imperfect casts of a species of Neverita are not uncommon in 

 the material obtained. The form may be new but is too imperfectly 

 represented for description. 



ANNULATA 



Annelid tube 

 Locality. Popof Island, 3372. 



