Plate V. 



Discotropites sandlingensis Hauer, Upper Triassic, California. 



Figs. 1-4, adult stage, showing ornamentation and septa. 



Figs. 5-7, larval stage, diam. 5.5 mm., showing beginning of keel. 



Figs. 8-10, larval stage, diam. 4.25 mm., showing beginning of serra- 

 tion of lobes, and transition from Goniatite to Ammonite stage. 



Figs. 11-13, early larval stage, diam. 2.68 mm., Goniatite stage, cor- 

 responding to Gastrioceras. 



Paratropites Sellai Mojsisovics, Upper Triassic, California. 

 Figs. 14-16, adult stage. 



Figs. 17-19, larval stage, diam. 5 mm., showing transition from Gon- 

 iatite to Ammonite stage. 



Ceratites humboldtensis Hyatt and Smith, Middle Triassic, Nevada. 



Figs. 20-21, adult stage. 



Figs. 22-24, adolescent stage. 



Figs. 25-26, larval stage, diam. 8 mm. 



The three genera figured on this plate show convergence in different 

 stocks. 



All figures on this plate are from Hyatt and Smith, Triassic Cephalo- 

 pod Genera of America. 



