l6 WATER REPTILES OF THE PAST AXD PRESENT 



and orders than to unite those already proposed. To raise every 

 proposed suborder of reptiles to an order, as has been proposed 

 by various writers, and the orders to subclasses, only leaves classi- 

 fication where it was; nothing has been added to taxonomy save 

 a lot of new names to perjilex and annoy the student. 



In the following scheme of classification three groups provision- 

 ally called orders are prefixed by an asterisk. 



CLASS REPTILIA 



Order COTYLOSAURIA 



Primilivc reptiles with notochordal vertebrae, imperforate temporal region, 

 persistent intercentra; two coracoids; plate-like pelvis, with all or most 

 of the amphibian skull elements; short legs and short neck; phalangeal 

 formula primarily 2, 3, 4, 5, 3(4). 

 Suborder Diadectosauria Permocarboniferous, North America. 



Pantylosauria Permocarboniferous, North America. 



Labidosauria Lower Permian, North America. 



Pareiasauria Upper Permian, Europe, Africa. 



Procolophonia Triassic, Europe, Africa. 



Order CHELONIA 



Temporal region imperforate. Head and limbs more or less retractile 

 within a box formed chiefly by the exoskeleton. 

 Suborder Pleurodira Triassic to recent. 



Cryptodira Jurassic to recent. 



Trionychoidea Cretaceous to recent. 



Order THEROMORPHA 



Primitive reptiles with notochordal vertebrae, perforate temporal region, 

 persistent intercentra; two coracoids; plate-like pelvis with median vacu- 

 ity; no free dermosupraoccipitals in skull; longer legs and neck; phalangeal 

 formula 2. 3, 4, 5, 3(4). 



Suborder Pelycosauria (sens, lat.) Permocarboniferous, North America, 



Europe. 

 Dromasauria Upper Permian, Africa. 



Dinocephalia Middle and Upper Permian, Africa. 



Order THERAPSIDA 



Reptiles with a single temporal perforation on each side; vertebrae not 

 notochordal; intercentra not persistent; pelvis with vacuity; skull bones 

 reduced; teeth heterodont; phalangeal formula, 2, 3, 3, 3, 3. 

 Suborder Anomodontia Permo-Trias, Africa, North America. 



Therocephalia Upper Permian, .\frica. 



Theriodontia Trias, Africa. 



