PEDIGREE OF REPTILES. 261 



The class presents a very comprehensive picture, al- 

 though only four orders now exist, of which two, the 

 lizards and the snakes, are scarcely to be separated. That 

 the snakes, which first appear in the Tertiary period, are 

 a direct offshoot from the lizards, is reduced to a cer- 

 tainty by comparative anatomy and the history of devel- 

 opment. In the various families of lizards we see the 

 absence of feet occurring in conjunction with the elonga- 

 tion of the body and the multiplication of the vertebrae; 

 and the modifications peculiar to the skull of the " true " 

 snakes are likewise represented in the systematic series 

 in every gradation, beginning with the skull of the true 

 lizard. We cannot specify the fossil genera in which 

 the transformation was initiated; but in this case a doubt 

 would be only a capricious denial. It is otherwise with 

 the remaining orders, which in the beginnings, hitherto 

 accessible to us, exhibit diversities so decidedly marked, 

 that in none has it been possible to trace a direct descent 

 from any known member of another. Prof. Huxley, a 

 great authority on the anatomy of these animals, says on 

 this subject as follows: — 



" If we ask, in what manner the earliest representatives 

 of these orders are distinguished from their living or 

 latest known representatives, we shall find, in all cases, 

 that the amount of difference in itself is remarkably 

 small in comparison with the length of time during which 

 the order has existed. So far as I know, there is no 

 fact to show that the later Plesiosauria, or Ichthyosauria, 

 exhibit an advance upon the earlier members of the 

 group. It is not clear that the Dinosauria of the wealden 

 and of the Cretaceous formations are more highly or- 

 ganized than those of the Trias; and even where a dif- 



