592 THE LIVING ANIMALS OF THE WORLD 



includes the greater number of species, the majority of the most venomous as well as harmless 

 varieties being comprised within its limits. The characters that are made the basis for 

 separating these snakes from the Boas are associated with the structure of the skull, and are 

 not therefore readily recognised without having recourse to dissection. It will suffice to mention 

 that, in this and the remaining groups, there is an entire absence from the lower jaw of the 

 slender supplementary bone known as the " coronoid," which is present in the Boas and 

 Pythons. From succeeding groups, such as the Viperine series, they are distinguished by the 

 circumstance that the upper jaw is firmly fixed in a horizontal position, and is not capable of 

 erection in a- vertical plane, or like the lid of a box, as obtains with the Vipers. 



These snakes are separated into secondary groups with relation to the structure of their 

 teeth. In one series these teeth are solid throughout, neither grooved nor tubular ; and all 



Bj ft' 



PINE-SNAKE 



A tree-Haunting American sptctes ivtth very hold markings 



the snakes thus characterised are harmless. In the second series one or more pairs of the 

 hinder upper teeth are longitudinally grooved, and act as poison-fangs ; they are consequently 

 distinguished as the " back-fanged " group. In the third series the front teeth of the upper 

 jaw-bone are grooved, and constitute the poison-fangs, and they are known as the " front- 

 fanged " group. 



To the first-mentioned solid-toothed and harmless division of the family belongs the 

 BRITISH RINGED SNAKE and some forty other allied species which are collectively known as 

 WATER-SNAKES, with reference to their more or less pronounced aquatic habits. The ringed 

 snake has a stoutish cylindrical body, keeled scales, flat head covered with regular shields, 

 wide mouth-cleft, and numerous teeth, the strongest of which are at the hinder end of 

 the jaw-bone. The colour varies somewhat, being usually grey, brown, or olive above, with 

 darker spots or narrow transverse bands; the under-surface is mottled black and white or 

 grey. The lip-shields are white or yellowish, with black dividing-lines. The neck in the 

 ordinary variety is usually ornamented with a yellow, white, or orange collar-like patch, 



