644 



NORTH AMERICAN INDEX FOSSILS. 



Guelph of Canada and New York; Upper Monroe of Michigan. 



XXXVIII. Clathrospira Ulrich and Scofield. 



Distinguished from Eotomaria by a delicate cancellated surface 

 sculpture, and concave vertical band on the periphery. Ordovicic— 

 Devonic (?). 

 131. C. subconica(Hall). (Fig. 878, a-c.) Ordovicic. 



Volutions flattened above and embracing nearly to the periph- 

 ery of the preceding, under side rounded ; band sharply defined, 

 covered by succeeding whorls ; surface marked by spiral and simi- 

 lar cancellating growth lines. 



Stones River and Black River groups of Minnesota, Wisconsin, 



A 



Fig. 878. a-c, Clathrospira subconica ; d-f, C. conica. {c,f enlargement of sur- 

 faces.) (After Ulrich and Scofield Pal. Minn.) 



Illinois, Kentucky, and Tennessee ; Black River and Trenton of 

 Canada and New York. Also doubtfully in the Cincinnati group 

 of Ohio, Indiana, and Kentucky. 

 132. C. conica U. and S. (Fig. 878, d-f.) Ordovicic. 



Smaller ; shoulder concave or flat, body concave below pe- 

 riphery, the concavity bounded below by an angulation or faint 

 carina. 



Black River and Trenton of Minnesota ; Trenton of Kentucky 

 and Lorraine of the Cincinnati region. 



XXXIX. Euryzone Koken. 

 Round-whorled Pleurotomarias, sometimes with slightly flat- 

 tened shoulder and with a slit band near the middle of the whorl 

 often covered by the margin of the succeeding whorls. Band 

 concave, flat or rarely convex ; surface with fine revolving striae 



