PEDIGREE OF REPTILES. 261 
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 
toa 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 
vertebra; 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 follows :— 
“Tf 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 
