PEDIGREE OF REPTILES. 26I 



The class presents a very comprehensive picture, 

 although 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 certainty by comparative anatomy and the history of 

 development. In the various families of lizards we see 

 the absence of feet occurring in conjunction with the 

 elongation 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 syste- 

 matic 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 be- 

 ginnings, 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 foMows : — 



" 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 weal- 

 den and of the Cretaceous formations are more highly 

 organized than those of the Trias ; and even where a 



