6 4 



NORTH AMERICAN INDEX FOSSILS. 



27. C. varians Hall. (Fig. 95.) Devonic. 



Shorter and stouter than preceding, with stronger septal ridges 

 and coarser cysts arranged cup in cup. 



Hamilton group of New York, etc. 



Fig. 96. Cystiphyllwn aggregatum (after Billings). 



28. C. sulcatum Billings. Devonic. 

 Short conical and curved form (zaphrentoid) with a deep cardinal 



fossula, and septa represented 

 by coarse plications of the 

 calyx floor. Cystoid structure 

 not visible in calyx. 



In the Onondaga beds of 

 New York, Canada, Michigan 

 and the Falls of the Ohio. 



29. C. aggregatum Billings. 

 (Figs. 96-97.) Devonic. 

 Compound, of cylindrical 



stems more or less closely 

 crowded. 



In the Onondaga limestone 

 of Canada and the Hamilton 

 of Michigan. 



Fig. 97. 



Cystiphyllum aggregatum var. 

 (after Lambe). 



XI. PaljEOcyclus E. & H. 

 Corallum simple, disk 

 shaped with flat base, or depressed topshaped, the base covered 



