20 



LACERTID.E. 



ent parts of the body, tlie relative dimensions of the limbs, 

 and the form and size of certain important scales, has, how- 

 ever, 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 trifling 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 six- 

 teenth 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 abdo- 

 minal 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 : — a, rostral ; b, na- 

 sal ; c, internasal ; d, fronto-na- 

 sal ; e, frontal ; f, anterior pal- 

 pebral ; g, posterior palpebral ; 

 h, fron to-parietal ; i, inter-pari- 

 etal ; k, parietal ; 1, occipital. 



In the next figure, the under 

 parts of a variety of the same 

 species are exhibited in outline, to show the collar, the 



