CLASS REPTILIA. 



Orders. 



1. Anomodontia. 



\\ 2. Sauropterygia. 



, 3. Chelonia. 



3 4. Ichthyopterygia. 



"* 5. Khynchocephalia. 



6. Squarnata. 



7. Dmosauria. 



8. Crocodilia. 



9. Ornithosauria. 



Sub- Order s. 



II. Pariasauria. 



2. Theriodontia. 



3. Dicynodontia. 



1. Cryptodira. 



2. Pleurodira. / 



3. Trionychia. 



1. Proterosauria. 



2. Rhynchocephalia Vera. 



1. Dolichosauria. 



2. Pythonomorpha. 



3. Lacertilia. 



4. Ophidia. 



1. Theropoda. 



2. Sauropoda. 



3. Ornithopoda. 



1. Parasuchia. n 



2. Mesosuchia. 



3. Eusuchia. 



On the evidence of skeletons alone it is impossible in 

 many cases to determine whether the early lung-breathers 

 were Amuiota or Anamniota. It is therefore difficult to 

 state precisely to what period must be assigned the dawn of 

 the class of reptiles, which exhibit an advance upon the 

 Batrachia or Amphibia not only in being provided with the 

 foatal envelope known as the amnion, but also in breathing by 

 lungs throughout life and never possessing branchiae at any 

 stage. In the existing fauna, however, the degeneration of the 

 parasphenoid bone and its functional replacement in the basi- 



