CROCODILIANS, LIZARDS, AND SNAKES. 157 



priority. Most of these persous take refuge behind the rules of the 

 American Ornithologists CJnion, and if the code of that body furnishes 

 defense for these violations of the elementary principles of language, 

 it should be corrected. Among misspellings are to be included hybrid 

 words and words which retain the Greek and other uon- Latin spellings. 

 It may be repeated here that the language of scientific nomenclature is 

 Latin, and words derived from Greek and other languages are spelled 

 according to the rules of the Latin language. 



It is stated above that the geographical scope of the present book is 

 the Nearctic realm. The southern continental boundary of this realm 

 is, however, not yet entirely clear. It evidently includes a large i^art of 

 the Mexican state of Sonora and the Mexican Plateau for a considera- 

 ble distance farther south. Owing to lack of collections, it is difficult 

 to state what the limit is in this direction, but I have included the state 

 of Guanajuato, where Dr. Alfredo Duges has traced many of the ISTorth- 

 ern species. On the east coast the fauna of the Tierra Caliente extends 

 northward to and even a little beyond the Eio Grande. In southwest- 

 ern Texas the presence of the genera of snakes, Sibon, Coniophanes, and 

 Drymohius, indicates the northern limit of that fauna. 



The results contained herein are derived chiefly from the collections 

 of the United States National Museum. To these I have added infor- 

 mation based on my own collections and observations in the field. 

 The whole constitutes the first general work on the North American 

 Sauria since that of Holbrook in 1845, and the only one on the 

 Ophidia since the book of Baird and Girard, published in 1853. Pro- 

 fessor Baird had such a work on the Sauria in contemplation during 

 his lifetime, and he placed his manuscript in my hands about the year 

 1864 for completion. Of this manuscript I have made considerable use 

 in the following pages, the greater part of the descriptions of fifty-one 

 of the one hundred and nine known species of that suborder being 

 from his pen. 



In the descrii)tion of the general characters and distribution of the 

 genera of the families of the lizards I have frequently copied the lan- 

 guage of Boulenger in the Catalogue of the Lizards in the British 

 Museum, with omissions and additions. In the systematic arrange- 

 ment of the genera of families of lizards, of which I have been able 

 to examine but a limited number of species preserved in spirits, as 

 the GeckonidiL', Agamida-, and Gerrhosauridu', I have also followed 

 Boulenger. 



Besides the collections of the U. S. National Museum, I have exam- 

 ined, in the preparation of this book, material belonging to the Acad- 

 emy of Natural Sciences of Philadelphia, and to the Philadelphia 

 museums, to whose officers my thanks arc especially due. I wish to 

 acknowledge also my indebtedness to Dr. Alexander Agassiz for the 

 opportunity of examining some Australian species; to Prof. Charles S. 



