NORTH AMERICAN INDEX FOSSILS. 



Pierre of Upper Missouri ; Bad Lands of South Dakota ; Eagle 

 Ford shales of Texas. 



\ 



Fig. 1496. 

 XVz' (After 



Flacenticeras siantoni, Fig. 1497. P/aanticeras {Slanfonoceras ?) 



Stantou.) pseudoplacenta: a, <^, young "placenta" stage, 



X % ; c-> section of adult, X % 5 ^-^ earliest 



whorls much enlarged. (After Hyatt and 



Smith.) 



386. P. spillmani Hyatt. (Fig. 1498.) Cretacic. 



Broader and stouter than the other species of P lac entic eras, with 

 rounded venter bearing low tubercles on either side ; suture similar 

 to P. syrtale. 



Ripleyan of New Jersey and Mississippi. 



#^##^ 



Fig. 1498. Flacenticeras [Stantonoceras ?) spillmani, a fragment, X Vzi ^"^^ 

 suture. ( After Hyatt. ) 



