742 NORTH AMERICAN INDEX FOSSILS. 



wards as ribs which die away on lower body whorl ; spirals broad 

 but generally faint ; a faint indication of anterior notch in aperture. 

 Bear River formation of Wyoming and Utah. 



CXXX. Goniobasis Lea. 

 Shell characters like those of Melania from which these shells, 

 are practically indistinguishable. This genus is the American rep- 

 resentative of the Old World genus Melania which is doubtfully 

 represented in the American Eocenic. The chief differences are 

 that Melania is viviparous and Goniobasis is oviparous. Both are 

 fluviatile animals. 



455. G. (Pachymelania) chrysallis Meek. (Fig. 1078, a.) 



Cretacic. 



Whorls flattened to slightly concave, sutures not impressed but 

 margined below by blunt carina which is often crenulated. Sur- 

 face with spirals. 



Bear River formation of Wyoming and Utah. 



456. G. (Pachymelania) chrysalloidea White. (Fig. 1078, b.) 



Cretacic. 

 Short and thick, whorls flat, sutures with faint shelf, surface 

 with rounded ribs and few faint spirals. 



Bear River formation of Wyoming and Utah. 



457. G. (Pachymelania) cleburni White. (Fig. 1078, c.) 



Cretacic. 



Large, gently tapering, sutures faintly impressed, surface with 

 low rounded ribs, gently concave forward, extending from suture- 

 to suture, and generally separated by wider interspaces ; no spirals. 



Bear River formation of Wyoming and Utah. 



458. G. convexa M. and H. (Fig. 1078, d.) Cretacic. 

 Smooth, slender, suture not impressed, surfaces flat, spirals faint. 



Variety impressa has the sutures slightly impressed. 

 Laramie, mouth of Judith River, Montana. 



459. G. endlichi White. (Fig. 1078, e,f.) Cretacic. 

 Short and thick, whorls round and smooth and sutures strongly 



impressed. 



Bear River formations of Wyoming and Utah. 



460. G. gracilenta Meek. (Fig. 1078, g.) Cretacic. 

 Small, smooth, sutures slightly impressed, surfaces gently con- 

 vex ; faint vertical striae. 



