678 



NORTH AMERICAN INDEX FOSSILS. 



Of medium size, whorls gradually enlarging ; body whorl en- 

 larging rather rapidly ; strong vertical and rather fainter revolving 

 striae. 



Niagaran of Indiana ; Monroan of Michigan. 

 227. S. expansus Hall. (Fig. 948.) Devonic. 



Fig. 948. Strophostylus expansus. (After Hall. 



Large, with a few small apical whorls and a very large and! 

 rapidly-expanding body whorl. 

 Oriskany of New York. 



228. S. carleyanus (Hall). (Fig. 949.) Mississippic. 

 Small, subglobose, final whorl expanded most vertically ; aper- 

 ture ovate ; sutures deep. 



St. Louis (Spergen) of Illinois and Indiana. 



229. S. nanus (M. and W.). (Fig. 950, a, b.) Carbonic. 

 Small ; differs from preceding in greater horizontal and less ver- 

 tical diameter, and in shallow sutures. 



Coal measures of Illinois, Indiana, Ohio, Iowa, Missouri, 

 Arkansas, and Nevada. 



230. S. remex (White). (Fig. 950, c.) Carbonic. 



