SAND LIZARD. DF 
ment of minute characters in the structure and proportions 
of the different parts of the body, the relative dimensions 
of the limbs, and the form and size of certain important 
scales, has, however, of late produced a greater degree of 
certainty, and more accurate definition, not only in the 
relation of the groups, but also in the characters of the 
species. One of the most useful attempts to reduce the 
characters of the Lizards to a tangible and certain rule, 
dependent upon differences which, though apparently tri- 
fling in themselves, are of great value as being constant 
and easily detected, was made by my friend Dr. Milne 
Edwards, in a valuable paper in the sixteenth volume of 
the “ Annales des Sciences Naturelles;” and Wagler has 
since that carried the principles of generic subdivision to 
an extent perhaps scarcely warranted by nature. Upon 
this point, however, it would be out of place here to dwell. 
The external parts from which the artificial characters 
of the present group of reptiles are founded, are principally 
the plates covering the head, the 
scales of the collar, the pra-anal 
scale, those in which the femoral 
pores are placed, the abdominal 
plates, and the scales of the back 
and tail. In order to comprehend 
these characters, I here introduce 
an outline of most of these parts. 
In the first figure, the plates of i oy (i 
the upper part of the head of the PSs we 
species about to be described are 7 
exhibited, and they are thus designated: —a, rostral; 
6, nasal; c, internasal; d, fronto-nasal; ¢, frontal; /, an- 
terior palpebral; g, posterior palpebral; /, fronto-parietal ; 
2, inter-parietal; 4, parietal; 7, occipital. 
