THE BRITISH REPTILES. 115 



female, as in all snakes, being the larger. The tail is a quarter as 

 long as the body. The eggs are laid in July and August, in heaps 

 of manure or decaying vegetable matter : they are usually from fifteen 

 to twenty in number, but may be thirty or more, and are about an 

 inch long, pale yellow in colour, obtuse at each end, and sticking 

 together. They are hatched by the heat of the sun and the ferment- 

 ation of their surroundings. The young feed on worms, tadpoles, 

 and other soft animals, but as they grow up the food seems to con- 

 sist mainly of frogs, newts, and fishes, so that they are seldom found 

 far away from water or marshy ground. They dive after their prey, 

 swim with their head and neck out of water, and take their rest 

 coiled up in the water with their head held just above its surface. 

 They cast their skin several times during the year, bursting it at the 

 neck, and leaving it behind as they crawl out of it through thick 

 herbage. They have no poison fangs and are quite harmless, but 

 when handled they emit a most noisome odour that may be due to 

 fright or a means of defence in the method of the skunk. It should 

 be clearly understood that a snake's " fang " is a tooth, and not the 

 tongue, which in this species is forked to a third of its length. 

 Hibernation begins in October and lasts for some four months, and 

 occasionally parties collect and sleep together coiled up in the same 

 hole. The distribution of this snake extends from Central Europe 

 into Algeria and Central Asia, and it varies a good deal in colour in 

 the outlying regions of its area. 



Vipera. Plate xxix. OPHIDIA . 



81. berus, VIPER. Scales keeled ; labial shields separated from 



the eye by scales ; zigzag line down back. 



The Viper, otherwise the Adder, ranges all over Britain, from 

 Caithness to Cornwall, and all across Europe and Asia, its easterly 

 limit being the island of Saghalien ; in the north it reaches the 

 Arctic Circle, but it does not go further south than Central Spain. 

 Like the Ringed Snake it is absent from Ireland. It is our only 

 venomous serpent, and can be identified by its having a row of teeth 

 only in the lower jaw, those in the upper jaw consisting only of the 

 two poison fangs and their reserves. These fangs are curved, and 

 have a slit near the tip communicating with the tube through the 

 tooth down which the poison is squirted from the gland at the side 

 of the head when the strike is made. When not in use the fangs 

 are kept folded backwards in a groove in the gum, and when broken 

 off they are replaced from the reserves. The body scales are dis- 

 tinctly keeled and in twenty-one rows. The head is covered with small 

 scales and a few shields. The labial shields are separated from the 

 eye by one or two series of scales. The upper, six to ten in number, 

 are whitish or yellowish ; the lower labials, numbering from three 

 to five, are in contact with the chin shields. There is no pit 

 between the nostrils and the eye. The colour varies from 

 ashy grey, through reddish brown to black, the end of the tail 

 being frequently yellow or red. The back has a bread zigzag 

 stripe more or less noticeable ; the head has the " death's head," 

 formed by bars across a sort of broad arrow pointing forwards 



