178 PALJSONIOLOGY. 



resembled the typical forms of the foreign genus Melania {= Tiara) that I was 

 led to refer it to that group. At last, however, a fine, large, nearly perfect 

 specimen was brought from the original locality, and this at once showed 

 that the outline of the lower part of its aperture is more angular, and its 

 inner lip more thickened below than in the Tiara group ; the whole com- 

 bination of characters being more nearly as in Lithasia, but still evidently 

 different from that genus. Consequently, in Dr. Hayden's Second Annual 

 Report, I proposed to found a new genus Pyrgulifera, for its reception ; 

 which name I now retain for it. 



Among the Old World fossil species, this shell seems to be most nearly 

 represented by Melania armata of Matheron, from the Lower Eocene lignite 

 beds at the mouth of the Rhone, in the southeast of France (see Cat. Meth. 

 Corps Org. Foss. du Depart, des Bouches-du- Rhone, pi. 37, figs. 11, 12, 

 and 13). It difi^ers, however, in the form of its aperture, as well as in hav- 

 ing the vertical folds, or cost*, on all of the volutions of the spire and the 

 upper flattened part of its whorls nearly or entirely without revolving lines; 

 while those below the angle of M. armata are finer and more numerous than 

 on our shell, which also has its inner lip generally thicker below. 



Localitij and position. — Sulphur Creek, near Bear River, Wyoming, 

 directly on the Union Pacific Railroad, where it occurs in the upheaved 

 beds in great numbers, along Avith numerous fresh-Avater and perhaps some 

 brackish- water shells, belonging to the horizon of the latest Cretaceous or 

 oldest Tertiary. 



VIVIPARID^E. 



Genus VIVIPARUS, Montfort. 



ViviPARUS CoNRADi, Meek aud Hajdeii. 



Plate 17, figs. 18 aud 18 a. 



Paludina Conradi, Meek aud Hitydeu(185fi), Proceed. Acad. Nat. Sci. Philad., VIII, 112. 



Viviparus Conradi, Meek (ISGO), iti Conrad's Smithsonian Check List, 12. 



Shell subtrochiform ; spire ccmical, moderately prominent, abrujitly 

 pointed at the apex; volutions five or six, flattened nearly to the slope of 

 the spire ; last one rather distinctly angular ai'ound the middle in young 

 shells, but more obtuse in the adult ; suture generally merely linear. Sur- 



