228 



NORTH AMERICAN INDEX FOSSILS. 





401. P. hyatti Stanton. (Fig. 1509, ^-^.) Cretacic. 



Small, the whorls more rapidly increasing in width, greatest 



transverse diameter near venter, ribs straight, simple, and ending 



in strong tubercle ; suture with saddles much broader than lobes. 



Fig. 1509. a, d, Prionotropis zvoolgari, small specimen, X % 5 ^> ventral view of 

 large fragment of same, y^%\ d, suture ; <f, /, P. hyatti, an average specimen, X % > 

 g, septum enlarged. (After Stanton.) 



Coloradoan (Pugnellus sandstone) of Colorado, and of Coal- 

 ville, Utah. 



CLXXIIL Prionocyclus Meek. 



Similar to Schloenbachia, but whorls remaining narrowly com- 

 pressed, the costas bending forward and ending before the keel is 

 reached; tubercles wanting or faint, and keel continuous; suture 

 is similar to Prionotropis. 



402. S. wyomingensis Meek. (Fig. 1510, a-c?.) Cretacic; 

 Whorls increasing slightly in width, sides flat, venter flat, ribs 



sharp, with intercalated shorter ones. 



Coloradoan of Wyoming, South Dakota, Utah and Colorado 

 (below Niobrara). 



403. P. macombi Meek. (Fig. 1510,^-^.) Cretacic. 

 Whorls scarcely increasing in width, ribs nearly obsolete, occur- 

 ring as low, rounded folds with shorter ones between, each ending 

 in a low, elongate node at ventral margin; venter smooth, gently 

 sloping from sharp keel on either side. 



Coloradoan of Colorado, and of New Mexico. 



