TERTIARY PERIOD. 215 



Last Bluff, Utah, are some that differ considerably from them. They, how- 

 ever, possess the general characteristics of the species, and are, therefore, 

 regarded as only varietal examples. One of these is figured as indicated 

 above. It is more elongate, sutures more distinct, and the revolving lines 

 more obscure than they usually are in typical examples. 



Length, twenty-two millimeters ; breadth of body-whorl, fourteen 



millimeters. 



Viviparus ionicus White. 



Plate XXI, fig. 6 a aud b. 



Shell of medium size, broadly trochiform ; spire moderately elevated ; 

 volutions five or six, prominent ; inner ones convex ; outer one more or 

 less flatlened upon the upper side, forming thus a more or less distinct angle 

 with the rounded outer side ; under side broadly rounded ; suture distinct. 



Surface marked by the usual lines of growth and apparently also by 

 small raised revolving lines. Upon the outer volution below its middle 

 there is a prominence made more or less conspicuous by the presence upon 

 it of a revolving raised line. In some examples this prominence amounts 

 almost to an angulation of the lower portion of the body-whorl. 



Length, about nineteen millimeters ; breadth of body -whorl, seventeen 

 millimeters. 



The examples contained in the collections are all preserved in a fine- 

 grained sandstone and the surface-markings are not distinctly. shown; but 

 its broadly turbinate form and the more or less distinctly tabulated character 

 of the upper part of the body-whorl sufficiently distinguish the species. 



Position and locality. — Strata probably of Tertiary age ; east side of 

 Joe's Valley, Utah. 



Viviparus ? ? 



Plate XXI, fig. 7 a and 6. 



f 



Associated with the other species just described, at Wales, Utah, 

 numerous examples of a small shell were obtained which are probably the 

 young of a species of Viviparus or some nearly allied shell. They are 

 possibly adult, but the features by which they might be specifically char- 

 acterized are too indefinite to justify a specific description and name before 

 the associated forms have all been carefully studied. 



