8o NORTH AMERICAN INDEX FOSSILS. 



88. R. eugenium Hall. (Fig. 1296.) Devonic. 



Slender cyrtoceracones, with adult portion straight, and with sub- 

 circular section. Septa regular, the sutures with ventral lobe ; regu- 

 lar, sharp expansions, fine lamellose growth lines and irregular 



Fig. 1296. Ryticeras eugenium, Y^%. (After Hall.) 



longitudinal lines characterize the surface. Siphuncle as in pre- 

 ceding. 



Schoharie and Onondaga of New York. 



89. R. aemulum Hall. Devonic. 

 Like the preceding, but regularly curved, of smaller apical angle, 



and with less regular, prominent, transverse expansions. 



Schoharie of New York, and Pendleton sandstone of Indiana. 



90. R. citum (Hall). Devonic. 

 Like R. eugenium, but more regularly curved, with the expan- 



