KECENT AND FOSSIL REPTILES. , 223 



Gymnosperms (p. 111). Twelve of the twenty-seven sub- 

 orders, given on the accompanying table, and four of the 

 eight orders, belong exclusively to the secondary period. 

 These mesolithic groups are marked by an asterisk. All 

 the orders, with the exception of Serpents, are found fossil 

 even in the Jura and Trias periods. 



In the first order, that of PriTnary Reptiles, or Primarij 

 Creepers (Tocosauria), we class the extinct TJiecodontia of 

 the Trias, together with those ReptUes which we may look 

 upon as the common primary form of the whole class. 

 To the latter, which we may call Primoeval Reptiles 

 (Proreptilia), the Proterosaurus of the Permian system 

 very probably belongs. The seven remaining orders 

 must be considered as diverging branches, which have 

 developed in different directions out of that common 

 primary form. The Thecodontia of the Trias, the only 

 positively known fossil forms of Tocosauria, were Lizards 

 which seem to have been like the still living monitor 

 lizards (Monitor, Varanus). 



Of the four orders of reptiles now existing, and which, 

 moreover, have alone represented the class since the 

 beginning of the tertiary epoch, that of Lizards (Lacertilia) 

 is probably most closely allied to the extinct Primary 

 Reptiles, and especially through the monitors already 

 named. The class of Serpents (Ophidia) developed out of a 

 branch of the order of lizards, and this probably not until 

 the beginning of the tertiary epoch. At least we at 

 present only know of fossil remains of serpents from the 

 tertiary strata. Crocodiles (Crocodilia) existed much earlier ; 

 the Teleosauria and Steneosauria belonging to the class are 

 found fossil in large quantities even in the Jura ; but the 



