INTRODUCTION. ix 



Synopsis op Families and Genera, and list op Species of 

 North American Serpents. 



Family I. — Crotalidae. Erectible poison fangs, in front. 

 Few teeth in upper jaw. A deep pit between the eye and nostril. 



Family II. — Colubridae. Both jaws fully provided with teeth. 

 No anal appendages. 



A. Loral and anteorhital both present 



B. Either loral or anteorhital absent. 



Family III. — Boidae. Both jaws with teeth. Rudiments of 

 hinder limbs or spiar-like anal appendages. 



Family IV. — Typhlopidae. Teeth only in one jaw, either 

 the upper or lower. Upper jaw strongly projecting. Scales on the 

 belly instead of scutellae, disposed in several series like those on the 

 upper surface. 



Family I. — CROTALID-SI. 



Pac,'e 



_ ., .^, ^^, f with small scale-like plates Crotalus 1 



Tail with a rattle. J ^uh large plates arranged as in 



Top of head covered (^ Colubfr Icrotalophorus 11 



Tail without a rattle, /present Agkistrodon 17 



Loral plate \ absent Toxicophis 19 



