162 STORY OF THE REPTILES 



ing the following may better represent Dr. Giintliers 

 scientific views of snakes, and help us a little into 

 seeing their real structural peculiarities : 



A. Teeth in one jaw only. Small burrowers ; eyes rudimentary. 



(1) Hopoterodonts. 

 AA. Teeth in both jaws. 



B. None of the teeth toward the front grooved or perforated 



into a poison-fang. (2) jVon-poiso?ious Coluhriforms. 



BB. Some forward teeth so converted into poison-fangs. 



C. Fang always erect, not capable of lying back in a groove 



of the upper jaw. (3) Poisonous Coluhriforms. 



CC. Fang lying back when the mouth is closed, erected 



when it is opened. (4) The Vijier-forms. 



The second group contains many very different 

 families. In it are the rough-tailed burrowers, the 

 fresh-water haunters, the egg-eaters, the tree-climb- 

 ers, the whip-snakes, and the sand-snakes. These 

 last begin by having rudiments of hind limbs to show 

 their probable close relationship to the great boa 

 family — the pythons, the boas, and the anaconda. 

 All have stumps of hind legs and differ in structure 

 mostly by the arrangement of the teeth. 



The third group holds the Elapidm (the beautiful 

 poisonous tree-snakes of South America) and the sea- 

 snakes just noted ; also all the terrible serpents of 

 India, includinij the col)ra. All these have fans^s 

 which are always erect. 



In the fourth group are all the vipers, rattle- 

 snakes, copperheads, and " water moccasins " or " cot- 

 tonmouths." Manv are Old World or Australian, 

 but America only has the last three ; and in the 

 Northeast United States these three are all the poi- 



