68 NORTH AMERICAN INDEX FOSSILS. 



YlG. 1276. Tarphyceras clarkei, X ^^' (After Ruedemann.) 



Fig. 1277. Tarphyceras niulticameratum, xi2X\xx2\?,^z'(\oxi, y^y-i^. (After Ruede- 

 mann, Bull. 90, N. Y. State Mus.) 



XX. EuRYSTOMiTES Schrocder. 



Differs from Tarphyceras in its less discoidal form, more rapidly 

 enlarging and less numerous whorls which embrace more strongly 



