xii PREFACE. 



Part II. will embrace the anatomy and physiology of each genus, illustrated 

 with drawings of the difierent ors^ans. 



It would have been better, perhaps, to have given the special anatomy of the 

 animal at the same time with the description of its external characters; but as 

 the work is published by subscription, the plan adopted was thought most 

 advisable, as either part may be had separately. 



For the arrangement of the order Chelonia, I have followed that of Dumeril 

 and BiBRON, and have adopted the genera that they have either received or 

 established in their Avork, as far as our reptiles are concerned, with one or two 

 exceptions, whicli will be found in the body of the work. 



For the order Sauria I have also chosen the classification of Dumeril and 

 BiBRON, in prefei-ence to that of any other naturalists, and have consequently 

 adopted it as far as it applies to the Saurian animals of the United States, with a 

 few exceptions, and the addition of one new genus, Crotophytus, for a western 

 Lizard, which could not be referred to any of theirs. 



For the order Ophidia, I have preferred the classification of Cuvier, though I 

 have been obliged to deviate from it in some particulars, either adding such 

 genera as seemed to me necessary, from other naturalists, as Wagler, Boie, 

 KuHL, &c., or establishing new ones. 



For the order Batrachia, and class Ecaudata, I have followed generally the 

 classification of Dumeril and Bibron, and have received most of their genera as 

 far as they embrace our Reptiles. 



