112 THE AMERICAN NATURALIST. [Vol. XXXV I II. 



7. Order Rhynchocephalia Giinther. 



These are the " Rhynchocephalia Vera " of Boulenger. They 

 represent by far the most conservative of all the Diaptosauria 

 because even the recent Sphenodon is in certain respects more 

 primitive than most of its Permian relatives. 



The order includes the Jurassic radiation of terrestrial, semi- 

 aquatic, and fully aquatic types, with modifications paralleling 



those m the Choristodera and Proganosauria, also the existing 

 terrestrial genus Sphenodon. The Jurassic forms are in many 

 respects less primitive than the existing genus. 



11. Order Parasuchia Huxley. 



Phis amphibious fresh water group, typified by Phytosaurus and 

 Aetosaurus, placed in the suborders Aetosauria and Phytosauria 

 respectively, has long been treated in connection with the Croc- 

 o ilia owmg to Huxley's influence and authority ; McGregor 

 has shown that it has practically no affinity to the Crocodilia, 

 Its relationships being closer to the Ichthyosauria, although it 

 constitutes an independent order, probably of freshwater, littoral, 

 carnivorous, short snouted (Aetosaurus) or long snouted (Phyto- 



