i66 



NORTH AMERICAN INDEX FOSSILS. 



2y2. P. ramosum Meek. Cretacic. 



Smaller and slightly more compressed than P. knoxvillense; 

 umbilicus proportionally somewhat larger; constrictions absent; 

 surface striae more flexuous, curving strongly forward, near um- 

 bilicus; septa more complex and more finely divided than in P. 

 knoxvillense. 



Chico (Nanaimo group) of Vancouver and probably also in the 

 United States. 



Haploceratida. 



CXX. Tetragonites Hyatt. 



Smooth, discoidal ammonites, slightly involute ; whorls of trape- 

 zoidal section; umbilicus large, sides abrupt; surface smooth with 

 numerous constrictions or varices which arch backwards on the 

 venter ; suture much as in Phylloceras. Comanchic-Cretacic. 



273. T. timotheanus Mayor. (Fig. 1413.) Comanchic-Cretacic. 



Fig. 141 3. Tetragonites timotheanus (After Whiteaves, Mes. Foss., 1.) 



Whorls nearly quadrangular in section, in younger portion be- 

 coming more rounded with age ; umbilicus about one third diameter 

 of shell; surface smooth but with periodic constrictions. 



Queen Charlotte formation (Div. C.) of Queen Charlotte 

 Islands; Nanaimo formation of Vancouver Island, also Europe 

 (Gault and Albien), Trichinopoli and Ootatoor series, India. 



CXXI. Gaudryceras Grossouvre. 



Differs from Tetragonites in its more rounded section and more 

 rapidly increasing whorls; constrictions (varices of shell) bending 

 forward on venter; surface with very fine thread-like striations, 

 parallel to the varices. Comanchic-Cretacic. 



