INTRODUCTION. 



species of Rattlesnake, usually known as the Crotalus durissus. Of this I have 

 had living specimens from Lake George, and from various localities in the Alle- 

 ghanies of Pennsylvania and Virginia. In Mr. Cope's Summary at the end of this 

 Essay, the reader will find all the necessary details as to the zoological characters 

 of this serpent. 



