400 



NORTH AMERICAN INDEX FOSSILS. 



I. C. americanus Packard. (Fig. 1697.) Carbonic. 



Nearly circular (about one inch in diameter), low, with ex- 

 tended rim. 



Coal Measures of Illinois. 



Fig. 1697. Cyclus americanus, with side view, X Yz- (After Packard.) 



2. C. limbatus Rogers. (Fig. 1698, a.) Carbonic. 

 Differs from the preceding in its spinose margin, lobed and 



noded surface and small size. 



Upper Coal Measures (lola limestone) of Kansas City, Missouri. 



3. C. minutus Rogers. (Fig. 1698, &.) Carbonic. 

 Distinguished by its small size (18 mm. long), elHptical out- 

 line, median and marginal ridges and nodes. 



Coal Measures (lola limestone) of Kansas City, Missouri. 



Fig. 1698. a, Cyclus limba/us, X 7 5 b, C. minutus, X 7 > <^^ C. communis, dia- 

 grammatic profile showing position of facetted eye, and slight groove separating 

 margin from carapace proper, X 7« (After Rogers.) 



4. C. communis Rogers. (Fig. 1698, c.) Carbonic. 



Subhemispheric, with narrow, nearly vertical margin. 



Upper Coal Measures of Kansas (Lower Garnett limestone) 

 and Missouri (lola limestone). 



II. Belinurus Konig. 

 Cephalothorax horseshoe-shaped, its central portion subquad- 

 rate and surrounded by a broad, flat, marginal area; long, slender. 



