Preface. Y 



absence of keels, the number of rows of scales, the suppres- 

 sion of some of the normal plates of the head, &c. &c., how 

 can we consistently ignore these characters in the case of 

 some genus which we want to make the receptacle for forlorn 

 unappropriated species ? Some of the genera of Colubridas 

 are established on very shadowy characters, Herpetoreas for in- 

 stance ; yet in Ablabes, Gunther includes species, affording ex- 

 cellent characters for separation, and which in fact demand sepa- 

 ration. Species are included in it with two, three or four 

 f rentals, smooth scales or keeled scales, and from 13 to 17 rows 

 of scales. I by no means think, that it would not be a gain, where 

 practicable, to enlarge the generic definition, so as judiciously 

 to include closely allied forms merely excluded by some trivial 

 character ; such a process is, I think, wanted, but it requires 

 caution to carry it out : but, taking the genera of serpents as 

 they stand, and bearing in view the admitted weight of certain 

 characters, why, I ask, and on what grounds, are we entitled to 

 relax our principles of classification, and make a particular 

 genus a receptacle wherein to impound aberrant species, like 

 Ablabes, as it stands in Gunther's catalogue, or the still more mis- 

 cellaneous throng constituting Eumeces ? 



This is, however, a mere difference of opinion, and I fully 

 acknowledge, whilst adopting a slight modification of his ar- 

 rangement, the temerity of dissenting from the verdict of so pro- 

 found a savant as Dr. Gunther, on a matter of classification. 



1 have also separated the terrestrial herbivorous lizards as a dis- 

 tinct Family, (Uromasticidge,) from the Agamida^. Their habits, 

 food, and aspect warrant this arrangement, and I cannot help 

 thinking that Dr. Gunther has been misled as regards the 

 arboreal habits of Leiolepis, which is, I believe, eminently and 

 solely a terrestrial and bmi'owing lizard. Cantor appears to be 

 the authority on which their re2)uted arboreal habits rest, but his 

 words do not seem to convey necessarily that he was an eye-wit- 

 ness of their powers of flight, beyond evolutions performed under 

 unnatural conditions and under confinement in a cage. Doubtless 

 the mechansim of the expansile ribs suggested the idea of their 



