138 CHAPTEES ON THE NATURAL HISTORY 



Besides the long list of harmless and useful snakes in this 

 country, belonging to ninny genera, we have three kinds of ven- 

 omous ones. These are the Rattlesnakes (Crotalus, caudisonu), 

 the true Moccasins (Ancistrodon) , and the Harlequin snakes 

 (Flaps). 



Taken as a whole, the order Opliidia of the ("lass Reptilia has 

 been created In contain all the snakes, closely allied as they arc 

 lo Lizards (Lacei'tilia), (here being no1 a few forms that connect 

 the two groups. Giinther tersely characterizes the Opliidia in 

 the following terms: Snakes are vertebrates with "an exceed- 

 ingly elongate body, cylindrical or subcylindrical, and termi- 

 nating in a tapering tail. The integuments are folded into flat 

 imbricate scales, which are rarely tubercular or granular. The 

 spinal column consists of a very great number of vertebra?, with 

 which I lie numerous ribs are movably articulated. Limbs are 

 entirely absent, or only rudiments of the posterior occur more or 

 less hidden below (he skin: there is no sternum. The bones of 

 the palate and jaws are movable; (he mandibles are united in 

 front by an elastic ligament, and are very distensible. Gener- 

 ally both jaws and the palate are toothed, the teeth being thin 

 and needle-like. There are no eyelids, no ear-opening. The vent 

 is a transverse slit." There are probably about 2,000 snakes 

 known, and many more yet remain to be described, the tropics 

 being the region in which their occurrence is most abundant. 

 There, too. do we find the most venomous as well as the largest 

 forms of t hem. 



There are species of snakes that live in burrows, rarely coming 

 out, and there are snakes that habitually live upon the 

 ground, while others are typical tree-snakes. Besides these 

 there are fresh-water and sea snakes; the latter (with the excep- 

 tion of one genus) never quitting that element. 



The majority of the opliidia lay eggs; some, on the other hand. 

 are viviparous. In the matter of f 1 they vary greatly: the non- 

 venomous burrowing-snakes subsist principally upon insects and 

 other invertebrates; the ground-snakes, which may be poisonous 

 or the reverse, live largely upon various vertebrata; some of 

 the tree-snakes are also venomous, and they prey upon arboreal 

 animals and the eggs of birds; finally, nearly all the fresh-water 

 snakes are innocuous, and they live upon aquatic animals, which 

 is likewise the case of the sea-snakes, but these latter are all 

 highly poisonous. In habit, we meet with both diurnal and noc- 



