GASTROPODA— VIVIPARIDJE. 727 



407. V. plicapressus White. (Fig. 1056, e.) Cretacic. 

 High-spired, whorls embracing to ambitus, slightly shelved at 



the suture ; aperture nearer axial line than in most species. 

 Laramie of Colorado and Wyoming. 



408. V. prudentia White. (Fig. 1056, /, g.) Cretacic. 

 Broad and low-spired, apical angle approaching 90 degrees ; 



whorls few, round, suture moderately impressed. 

 Laramie of Colorado and the Canadian region. 



409. V. raynoldsiannus M. and H. (Fig. 1055, c.) Eocenic. 

 Smooth, round-whorled with apical angle 60-65 degrees, nearly 



circular aperture and small umbilicus. 

 Fort Union beds of Montana, etc. 



410. V. trochiformis M. and H. (Fig. 1055, d, e.) Eocenic. 

 With three revolving spirals, or angulations between which the 



shell is flattened. 



Fort Union beds of Montana. A biangulate mutation occurs in 

 Wasatch of Utah. 



411. V. formosa Meek. (Fig. 1055,/, £\) Eocenic. 

 Broad with shallow sutures and three to four spirals. 



Fort Union beds of Montana. 



412. V. (Tulotoma) thompsoni White. (Fig. 1056, h-k.) 



Like V. trochiformis but with more accentuated spirals which in 

 some of the specialized mutations become more or less strongly 

 nodose. 



CXX. Campeloma Rafinesque. 



Like Viviparus but thick-shelled and with thickened inner lip. 

 Smooth, rarely with exceedingly fine spirals. Cretacic-Recent. 



413. C. macrospira Meek. (Fig. 1057, a, b.) Cretacic. 

 Large, rather long-spired, volutions round, smooth and with 



moderately impressed sutures ; aperture ovate ; inner lip thickened. 

 Bear River (Coloradoan), Wyoming, Idaho, etc. 



414. C. vetulum M. and H. (Fig. 1057, c, d.) Cretacic. 

 Like preceding but smaller and slightly more acute, inner lip 



scarcely thickened, umbilical region indented ; surface obscurely 

 spiraled. 



Judith River beds, Montana, and Canada. 



415. C. multilineatum M. and H. (Fig. 1057, e S-) Cretacic. 



