PHYLOGENY. 



those of the Cotylosauria and of the Theromora. The 

 important character and role of these types may be 

 inferred from the fact that the Cotylosauria are struc- 

 turally nearer to the Batrachia. and the Theromora to 

 the Mammalia than any other, and the former presents 

 characters which render it probable that all the other 

 reptiles derived their being from them. The phylogeny 

 may be thus expressed : 



MAMMALIA 

 Pterosauria 



Squamata 



Dinosauria 



Crocodilia 



Rhynchocephalia 



Ichthyosauria 



Therid 



'otylosauri 



Sauropterygia 



Anomodonta 



Testudinata 



It is extremely probable that the characters of the 

 posterior parts of the cranium of reptiles, as seen in 

 the osseous bars posterior to the orbit, were derived 

 by a kind of natural trephining of the cranial roof of 

 the primitive order of the Cotylosauria. This order 

 has left remains in the Permian beds of North Amer- 

 ica, South Africa, and Germany. This is the theory 

 of Baur, 3 and I have rendered it probable by researches 

 on the Permian genera of North America. 4 



1 Some unknown type of Pythonomorpha will represent the ancestor of 

 the Ophidia, while it is uncertain whether this order originated from the 

 Theriodonta or the Rhynchocephalia. 



2 The Theromora include the Pelycosauria, Theriodonta, Anomodonta, 

 and other suborders. 



3 American Journal of Morphology, 1889, p. 471. 



4 Trans. Amer. Philos. Society, 1892, p. 13 ; American Naturalist, 1892, p. 

 407. 



