178 SUBKIKGDOM VERTEBEATA. 



pents known. They are frequently found over twenty feet 

 in length. Their bite is harmless, but, suspending themselyes 

 from the branches of trees, they dart upon their victims as 

 they pass beneath, entwine them in massive folds, crush 

 their bones, and then swallow them entire.* 



Hydrophidae. — The 

 ■^'^- *"*• ^-^ Sea-snakes inhabit the 



fresh and salt waters of 

 warm regions. They are 

 distinguished by their 

 vertically-flattened tail 

 and uniform arrange- 

 ment of teeth, showing 

 no distinct fangs, though 

 proved to be highly ven- 



SeorsnaJce. ^ rr,-, •■, 



omous. The nostrils, on 

 the upper part of the snout, are provided with valves, which 

 proves them to be air-breathing. At least forty-eight species 

 have been discovered, all but six belonging to the Eastern 

 Hemisphere. 



* To aid in grasping the limb, they have on each side, at the base of the tail, a 

 horny spur. These are internally connected with a series of bones, rudimentally 

 representing the hind legs of quadrupeds. 



Fig. SOS. 



Bascanwn constrictor^ Black-snake. 



