244 



SNAKES. 



Siberian Halys. 



Somewhat superior in size to the common viper, this species (A 

 halys) may be recognised by the small portion of the head that is 

 covered with shields, and also in that each shield, <>r pair of shields, overlaps with 

 its hinder edge the shield immediately behind it, thus producing a more or less 

 marked imbrication of the whole of the head-shields. Another characteristic is to be 

 found in the small size of the anterior frontal shields, which together have a crescentic 

 shape and a somewhat saddle-shaped upper surface. The head is very distinctly 

 defined from the compressed neck, the body being rather long, of a rounded trian- 

 gular form in the middle, and covered with twenty-three rows of triangular scales; 

 the very short tail, which is much thinner than the hinder-part of the body, is 

 conical, and armed at the extremity with a forked horny appendage. The ground- 



SIBBEIAN HALYS VIPER (J nat. size 



colour of the middle of the back is a dark brownish yellow grey, while that of the 

 under-parts is a yellowish white, with more or less well-defined black spots on the 

 hinder shields. The yellow ground of the labial shields of the head has chestnut- 

 brown markings; and the crown of the head bears a large quadrangular blotch, 

 forming an interrupted transverse band on the frontal shields, and a temporal band 

 running from the hinder border of the eye to the angle of the mouth and the side 

 of the neck. Somewhat similar markings ornament the back, and ace more or less 

 clearly margined with yellow. Along the whole length of the back and the ridge 

 of the tail are a. number of yellowish or yellowish white black-edged irregular 

 blotches or crossbands ; and on the sides are two rows of blackish brown spots 

 with white edges, which frequently run one into another, the tirst dark spot on 

 the neck differing from tic rest by its horse-shoe form. The distributional area of 

 this snake extends eastwards from the Volga to the Yeiiesei. In Europe the halys 



