ii6 



NORTH AMERICAN INDEX FOSSILS. 



153. A. inops Dawson. Carbonic. 



Small, rapidly tapering; septa rather close, gently concave; si- 

 phuncle large, nearly one half diameter of tube. 



Carbonic limestone, Pictou and Brookfield of Nova Scotia. 



Fig. 1350. Actinoceras bigsbyi, long- 

 itudinal section. ( After Clarke, Pal. 

 Minn.) 





Fig. 135 1. Actinoceras {Ortnoceras) 

 tenuifilui?i, X %• (After Hall, Pal. N. 

 Y., I.) 



LX. Cyrtactinoceras Hyatt. 



Cyrtoceracones with depressed section, rather closely arranged 

 septa, and a moderately nummulitic siphuncle, filled in the middle 

 stages with rosettes of organic deposits, and located near the con- 

 vex side of the conch, but shrinking and approaching the center in 

 old asre. 



