VI INTRODUCTION 



plete lists. In the case of the difficult genus Thamnophis 

 references are given to Ruthven's excellent review. Com- 

 mon names for reptiles and amphibians are in great con- 

 fusion, and are often of generic rather than of specific 

 application. No attempt is made to recognize any except 

 those which are in well-established usage. The host which 

 have been recently coined by various writers are frequently 

 inapt and almost surely unlikely to survive. It is entirely 

 possible that some vernacular names really often used have 

 escaped our notice, since many are in restricted local use. 

 The type localities are as nearly exact as it is possible to 

 determine. This cannot be said regarding the ranges. 

 Many are obviously faulty, but a sincere attempt has been 

 made to collect records of authentic captures; however, 

 with a literature so extensive and so scattered, records have 

 almost surely been overlooked. In many cases, our knowl- 

 edge does not warrant drawing hard and fast lines delimit- 

 ing a form's occurrence, and we often state ranges in pur- 

 posely general terms. There still is opportunity for valuable 

 field work to determine the precise distribution of many of 

 our most common species. An example is the recent dis- 

 covery that Virginia valeriae is far from rare in parts of New 

 Jersey. 



Our hearty thanks are due to many for information and 

 advice, especially to Samuel Henshaw, John Van Denburgh, 

 and Alexander G. Ruthven. 



G. K. Noble has assisted considerably in verifying refer- 

 ences and searching literature, and for this assistance he has 

 our grateful remembrance. 



T. B. 



