IV INTRODUCTION 



widespread use, and constitute the most recent attempts 

 toward complete lists. In the case of the difficult genus 

 Thamnophis references are given to Ruthven's excellent 

 review. Common names for reptiles and amphibians are 

 in great confusion, 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 fre- 

 quently 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 ; how- 

 ever, with a literature so extensive and so scattered, records 

 have almost surely been overlooked. In many cases, our 

 knowledge does not warrant drawing hard and fast lines de- 

 limiting a form's occurrence, and we often state ranges in 

 purposely 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 

 discovery 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 Alex. 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. 



