144 



NORTH AMERICAN INDEX FOSSILS. 



Middle Coal Measures of Arkansas, and England, Belgium and 

 Germany. 



221. G. noliense Cox. (Fig. 1395,1*.) Carbonic. 



f f|lf 



-^ 



^ ff^ 



Fig. 1395. a, b, Gasiriocei-as entogonum, X K> ^"^^ surface enlarged ; c-e, G. 

 g/obtilosum, suture and shell X Yi '■> f-^-> ^- ^isien, suture enlarged and shell X % 

 i, G. noliense, suture enlarged. (After J. P. Smith.) 



Like G. carbonarhim but shell smooth, and siphonal saddle 

 mucronate instead of notched. 



Des Moines formation of Iowa; Middle Coal Measures of Ken- 

 tucky. 



222. G. subcavum Miller and Gurley. (Fig. 1393, o-c.) Carbonic. 



Small and broad like G. globulosum, but with sharp umbilical 

 angle and deep umbilicus, and no umbilical ribs. 



Upper Coal Measures of Illinois and Texas. 



LXXXVII. ScHiSTOCERAS Hyatt. 



Similar in general form to species of Gastrioceras, but generally 

 less transverse, with moderate umbilicus ; the suture has a large 

 bottle-shaped saddle, the only distinction between it and that of 

 Prolecanites (see beyond). The two arms of the ventral lobe are 

 widely separated, and three pairs of lateral lobes and a small um- 

 bilical lobe with two pairs of dorsal lot^es occur. The lobes are 

 hastate, saddles club-shaped, the annular lobe deep and acute. 

 Carbonic. 



