210 TERTIARY PERIOD. 



Planorbis (!). 



From strata, probably of Eocene Tertiary age, at the head of Soldier's 

 Fork, Utah, some specimens of dark carbonaceous shale were obtained, con- 

 taining Unio vetustus Meek, and which are also crowded with shells of a 

 small Planorhis. The shells are of nearly uniform size, averaging about 

 three millimeters in diameter; slightly convex above, narrowly umbilicate 

 below; volutions about three, broader than high, not angulated, marked 

 by ordinary lines and small wrinkfes of growth. They ajDjoear to be mature 

 shells, l^ut they present too few prominent specific characters to satisfy me 

 of the present propriety of giving them a specific name. 



Family PHYSIDiE. 



Genus PIIYSA Drapnrnaud, 1801. 



Physa Bridgerensis Bleek. ? 



riate XXr, lig. 2 a. 



Physa Bridgerensis Meek, 1872, Geol. Siirv. Montaua, Idabo, Wyoming, aud Utab, 516. 



The collections contain a number of imperfect examples of a species of 

 Physa, which seem to belong to P. Bridgerensis Meek, the type-specimens of 

 Avhich he obtained from Tertiary strata at Church Buttes, fourteen miles 

 from Fort Bridger, Wyoming Territory. They, however, present some 

 differences which may prove to be of specific importance. The following 

 is the substance of Mr. Meek's description, which I use because none of our 

 specimens shows all the details mentioned by him with clearness, although 

 they are sufficient for the identification of the species. The specimen 

 figured, while it presents the surface-markings and the character of the spire 

 with more clearness than any of the others, is not so large nor quite so ro- 

 bust as most of the other examples are. "Shell large, subovate; spire promi- 

 nent, conical; volutions from four and a half to five, moderately convex; last 

 one large, but not ventricose ; suture well defined ; aperture narrow-sub- 

 ovate, arcuate, acutely angular above, and about twice as long as the spu-e ; 

 columella twisted into a rather prominent fold; surface with fine sharp 

 lines of growth." 



Position and locality/. — Sti-ata of the" Tertiary period ; San Pete Valley, 

 Utah. 



