GASTROPODA— -LIMN '2EID2E. 8 1 7 



678. L. (Lymnophysa) nitidula (Meek). (Fig. 1203,*.) Cretacic. 

 Of medium size, high-spired; whorls rounded; sutures deep; 



spire as long as or longer than aperture, rather thick-set in aspect. 

 Bear River formation of Wyoming. 



679. L. (Pleurolymnaea) tenuicostata M. and H. (Fig. 1203, /, k.) 



Eocenic. 

 Very slender, anterior end of lip extended, surface with sharp, 

 narrow, flexuous costae. 



Fort Union beds of Upper Missouri country. 



680. L. meeki Evans & Shumard. (Fig. 1203, /.) Oligocenic. 

 Of medium size; spire of about four rapidly tapering, rounded 



whorls; body whorl round, large, sutures moderately impressed. 

 White River group of Upper Missouri region. 



681. L. shumardi Meek & Hay den. (Fig. 1203, m.) Oligocenic. 

 Body whorl somewhat shorter than in preceding; aperture pro- 

 portionally somewhat broader. 



White River group of Upper Missouri region. 



CCXIII. Vorticifex Meek. 

 Heliciform or Planorbiform shells of ventricose aspect, open, but 

 small umbilicus and somewhat angulated whorls, one of the angu- 

 lations bounding the umbilicus ; strong costse of growth, especially 

 in the young. Miocenic. 



682. V. binneyi Meek. (Fig. 1205, f, g.) Miocenic. 

 Umbilicus large ; spire flat ; surface with regular variciform 



growth lines. 



Miocenic of Kawsoh Mountains, Nevada. 



683. V. tryoni Meek. (Fig. 1205, h-j.) Miocenic. 

 Smaller than preceding, surface ornamentation fainter; umbili- 

 cus small. 



Occurs with the preceding. 



CCXIV. Planorbis Guettard. 

 Coiled typically in a discoid manner, the entire spire below the 

 body whorl, but not symmetrically involute ; aperture oval, varying 

 to crescent-shaped and with a sharp outer margin. Lias-Recent. 



