GASTROPODA— LIMN JEID2E. 



819 



Fort Union beds of upper Missouri River region. 



688. P. utahensis Meek. (Fig. 1206, m-o.) Eocenic. 

 Large and much compressed vertically; aperture transverse; 



outer margin subangular; variety spectabilis (Fig. 1206, p) has 

 the outer margin more rounded. 



Bridger group of southern Wyoming. 



689. P. cirratus White. (Fig. 1206, q-s.) Eocenic. 



Fig. 1206. a-f, Planorbis velernus ; small (a-c) and larger form ; g-i, P. convo- 

 lutus ; j, k, P. (Bathyomphalus) atnplexus ; I, P. {B.) planiconvexus ; m-o, P. 

 utahensis, P. var. spectabilis; q-s, P. cirratus; t-v, P. vetustus ; w, x, P. leidyi ; 

 y, z, P. lunata. (All after White, U. S. G. S., III.) 



Small, of numerous, very slightly increasing whorls coiling 

 nearly in a plane ; upper and lower aspect much the same. 

 Green River of southern Wyoming. 



690. P. vetustus Meek & Hay den. (Fig. 1206, t-v.) Oligocenic. 



Smaller than T. utahensis and the outer side of last whorls more 

 sharply angulated ; spire less depressed. 



White River beds of Dakota. 



