GASTROPODA— -V1VIPARID7E. 



725 



Family Viviparid^e Gill. 



CXIX. Viviparus Montford. {Paludina Lam.) 



Conical or turbinate shells with acute spire of rounded or flat- 

 tened whorls ; suture depressed, and often accentuated by thick- 

 ening of shell below its aperture, with continuous peristome ; um- 

 bilicus minute or absent. Angulated forms are generally referred 

 to Tulotoma ; the smooth, thick shelled species with thick inner 

 lip are referred to Campeloma Rafinesque. Habitat fresh water. 

 Jurassic-Recent. 



402. V. gilli M. and H. (Fig. 1055, a, b.) Jurassic. 

 Small, of about four rounded volutions, increasing rather rapidly; 



suture simply impressed ; aperture oval ; growth lines faint. 

 Upper Jurassic (Morrison) of Black Hills. 



403. V. couesii White. (Fig. 1056, a.) Cretacic. 



FlG. 1055. a, 6, Viviparus gilli; c, V. reynoldsianus ; d, e, V. trochiformis ; f, g, 

 V. formosa ; A, i, V. conradi. (U. S. Geol. Surv. ) 



Large, high-spired, whorls round, sutures deep, body whorl 

 somewhat flattened and slightly shouldered without angulation. 



Bear River formation of Wyoming. 

 404. V. conradi M. and H. (Fig. 1055, k, i.) Cretacic. 



Apical angle from 45-60 degrees ; sutures scarcely impressed, 

 whorls nearly flat, angulated below. 



