70 



NORTH AMERICAN INDEX FOSSILS. 



The western representative of this species (var. occidentalis Hall) 

 has broad whorls with flattened dorsum and simple concave septa. 



^^■^-^^^-^^^^^^ 



Fig. 1279. Ewystomites tauuuiis, 



(^AlLer Hall, Pal. N. Y., I.) 



Black River of New York; Stories River of Minnesota and 

 Illinois. 



XXI. ScHROEDEROCERAs Hyatt. 



Differs from Tarphyccras in the dorsally placed siphuncle, and 

 the frequent tetragonal section of the whorls. Ordovicic. 



68. S. eatoni (Whitfield). (Figs. 1280, 1281.) Ordovicic. 



Fig. 1280. Schroederoceras eatoni, X Vs- Y\G. 1 28 1. Schroederoceras eatoni, long- 



( After Ruedemann, Bull. 90, N. Y. State itudinal and transverse sections. (After 

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



Externally much like Tarphyceras seelyi, but smaller and with 

 shallower septa, deeper impressed zone and siphuncle near the 

 inside of the whorls. 



