Plate IX. 



Aspenites acutus Hyatt and Smith, Lower Triassic, Idaho. 



Figs. 1-4, adult stage, showing resemblance to the Devonian Tim- 

 anites. 



Eutomoceras Laubei Meek, Middle Triassic, Nevada. 



Figs. 5-7, showing convergence of Hungaritidae with Tropitidae. 

 Inyoites Oweni Hyatt and Smith, Lower Triassic, California. 



Figs. 8-13, showing convergence of Hungaritidae and Tropitidae. 



Longobardites nevadanus Hyatt and Smith, Middle Triassic, Nevada. 



Figs. 14-16, showing convergence of Pinacoceratoidea with Hungar- 

 itidae, through partial reversion towards the same ancestral 

 Timanites. 



All figures from Hyatt and Smith, Triassic Cephalopod Genera of 

 America. 



