THE CROCODILIANS, LIZARDS, AND SNAKES OF NORTH 



AMERICA. 



By Edward Drinker Cope, A. M,, Ph. D., 



Professor of Zoology and Comparative Anatomy in the University of Pennsylvania, and 

 Member of the U. S. National Academy of Sciences, 



PREFACE. 



The scope of the present work is to give an account of the physical 

 characteristics of the reptiles of the orders of Loricata and Squamata, 

 which inhabit the Nearctic zoological realm, so far as they are known 

 to the writer. That the work is far from complete I am well aware, but 

 that it is much in advance of other works in this respect may be well 

 admitted, as no general work of the kind has appeared since that of 

 Holbrook, half a century ago. With my book on the Batrachia, pub- 

 lished in 1889, and Dr. Baur's on the Testndinata (in preparation), the 

 access to North American herpetology becomes equal to that which 

 the science of ornithology has long enjoyed. 



The principles of classification which have been followed are those 

 wliich the nature of the case requires, so far as the author has been 

 able to discover them. One general statement may be made as an 

 abstract proposition, and that is that the taxonomy of organic beings 

 is a register of structural or anatomical characters from the most com- 

 prehensive to the smallest divisions. This is generally recognized in 

 the case of the former, but there are many naturalists who fail to recog- 

 nize it in the case of the more restricted divisions, and especially as 

 applying to genera. An indefinite idea of the " naturalness" of the 

 collocation of species necessary to constitute genera still lingers in 

 their minds. By this idea of a "natural" association of species, they 

 mean a group which coincides in possessing a certain community of 

 species characters, as color, and color pattern, size, nature of surfaces, 

 geographical range, etc., all of which, while of importance in their place, 

 are quite irrelevant to the question of generic divisions. I long since 

 pointed out that generic characters may, and in fact generally do, arise 

 in the process of evolution quite independently of the specific, so that 

 certain species of different genera resemble each other in the so-called 

 " natural," that is, specific characters, more than they do other species of 

 their own genus. The same phenomenon is well known among higher 



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