INTRODUCTION. 



specimens of PhrynosomaB, &c., brought from the neighbourhood of the sources 

 of the Red river, together with some curious observations on their habits. 



Mr. NuTTALL, too, has placed in my hands many animals collected by him in his 

 journey along the banks of the Oregon river. Some of these are yet undescribed; 

 they vi^ill appear in a succeeding volume. 



I regret to state that death has deprived me of the invaluable services of Mr. 

 Sera, who had been for ten years my draughtsman. Enough, however, of his 

 correct and spirited drawings remain for a third volume. 



As the object of this work is truth, or a wish to determine, with as much 

 certainty as possible, the different species of the reptiles of this country, and to 

 extricate them from the multitude of synonymes in which some of them are 

 entangled, I will avail myself of every opportunity of correcting such errors as I 

 may fall into; these will always be stated in an appendix to each volume. 



A word or two with respect to the use of specific names. I have endeavoured 

 invariably to retain, with the name of the naturalist describing it, that by 

 which the animal was first made known. These should always be retained, even 

 if bad, though the generic names may, indeed must often, be changed, according 

 to the light thrown by anatomical investigation upon the affinities that animals 

 bear to each other in their structure or organization. Thus, in assigning the 



