SAND LIZARD. 



21 



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 prse-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 

 the upper part of the head of the 

 species about to be described are 

 exhibited, and they are thus designated: #, rostral; 

 5, nasal ; c, internasal ; d, fronto-nasal ; 0, frontal ; /*, an- 

 terior palpebral ; g, posterior palpebral ; A, fronto-parietal ; 

 , inter-parietal; #, parietal; , occipital. 



