194 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 
Bv permission of the New Tori Zoological Society 
PINE-SNAKE 
tree-haunttng American species with njery bold 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 Sn.vKE 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 iaw-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. 
