28 ACCELERATION OP DEVELOPMENT IN FOSSIL CEPHALOPODA 



Lituites, PI. XIV, fig. 6, a reversionary Nautiloid, striking back towards 

 Orthoceras. 



Timanites, PL III, figs. 12-14, the Paleozoic goniatite ancestral stock of 

 the Hungaritidae, transitional from Gephyroceras. 



Goniatites, PI. I, figs. 1-9, a group transitional from the Goniatites to 

 the Ammonites; the distant ancestral stock of Tropitidae and 

 Arcestidae. 



Gastrioceras, Pi. I, figs. 10-14, a progressive development from the 

 Goniatites ; the family radicle of Tropitidae and Arcestidae ; a form 

 with the septation of a Goniatite, but with the sculpture and inner 

 structure already advanced to the stage of Ammonites. 



Paralegoceras, PI. II, figs. 1-5, a more advanced member of the gastrio- 

 ceran stock, showing the advance towards becoming an Ammonite. 



Schistoceras, PL II, figs. 6-13, a direct transition from the Glyphio- 

 ceratidae towards the Tropitidae. 



Waagenoceras, PL X, fig. 12, a late Paleozoic member of the Arcestidae, 

 showing an advance to Mesozoic characters. 



Ussuria, PL XI, figs. 1-14, transitional Ammonite, showing distinct re- 

 capitulation of race history in ontogeny. 



Cordillerites, PL XII, figs. 1-8, transitional from Goniatite to Ammonite, 

 showing simple and direct recapitulation in ontogeny. 



Pronorites, PL XII, figs. 9-12, ancestral stock of Cordillerites. 



Aspenites, PL IX, figs. 1-4, transitional from Gephyroceratidae to Pinaco- 

 ceratidae, showing strong reminiscences of the Devonian radicle, 

 Timanites. 



Meekoceras, PL VII, figs. 1-12, the primitive stock of Ceratitidae, con- 

 necting this group with Lecanites, the family radicle. 



Inyoites, PL IX, figs. 8-13, an accelerated member of the Hungaritidae, 

 showing convergence with the stock of Tropitidae. 



Paranannites, PL XI, figs. 15-20, a primitive progressive link between 

 Nannites and the Ptychitidae. 



Columbites, PL IV, figs. 1-10, a primitive Ammonite, transitional from 

 Gastrioceras to Tropitidse, showing simple recapitulation; this is the 

 probable radicle of Tropites and its near kindred, and connects them 

 with the Glyphioceratidse. 



