22 2 THE HISTORY OF CEEATIOX. 



quently the most ancient Amniota, then the origin of this 

 main class must necessarily have taken place in the 

 preceding period, towards the end of the primary, namely, 

 in the Permian period. However, all other remains of 

 Reptiles, which were formerly believed to have been found 

 in the Permian and the Coal system, or even in the Devonian 

 system, have been proved to be either not remains of 

 Reptiles at all, or to belong to a more recent date (for the 

 most part to the Trias). (Compare Plate XIV.) 



The common hypothetical primary form of all Amniotic 

 animals, which we may call Prota'mnion, and which was 

 possibly nearly related to the Proterosaurus, very probably 

 stood upon the whole mid -way between salamanders and 

 lizards, in regard to its bodily formation. Its descendants 

 divided at an early period into two different lines, one of 

 which became the common primary form of Reptiles and 

 Birds, the other the primary form of Mammals. 



Of all the three classes of Amniota, Reptiles (Reptilia, or 

 Pholidota, also called Sauria in the widest sense), remain at 

 the lowest stage of development, and differ least from their 

 ancestors, the Amphibia. Hence they were formerly uni- 

 versally included among them, although their whole 

 organization is much more like that of Birds than Amphibia. 

 There now exist only four orders of Reptiles, namely, — 

 Lizards, Serpents, Crocodiles, and Tortoises. They, however, 

 form but a poor remnant of the exceedingly various and 

 highly developed host of Reptiles which lived during the 

 Mesolithic, or Secondary epoch, and predominated over ail 

 other Vertebrata. The immense development of Reptiles 

 during the Secondary epoch is so characteristic that we 

 could as well name it after those animals as after the 



