Morphological Variations in Vipera berus. 7 



The Syncipital Shields. — These in a typical Vipera herm, 

 in addition to the supraocular shield, include three large 

 symmetrical shields on the top of the head, namely, the 

 single frontal shield and the two parietals. In the speci- 

 mens whose body scaling is tabulated above, the most 

 important variations in these syncipital shields were the 

 following : — 



In No. 1 each parietal was broken up into three small 

 shields, which is an approximation to what obtains in Vipera 

 aspis. 



In No. 24 there were two shields articulating with each 

 parietal which are not usually present, which might be 

 described as two accessory parietals. 



In No. 28 the frontal shield is small, and the parietals are 

 represented by a number of small scales, like the arrange- 

 ment in Vipera aspis. 



In No. 29 the scales round the eye are 10 in number. 



In No. 28 the scales round the eye are 8 in number. 



In No. 30 the scales round the eye are 9 in number. 



In No. 34 the two parietals are represented by a number 

 of small shields, these being irregular in shape and size, as 

 in V. aspis. 



In No. 35 a somewhat unusual arrangement, but one 

 which I have seen before, is present. The frontal is entirely 

 surrounded by 12 small shields, except posteriorly, where it 

 is in contact with the parietals. In addition, in front of the 

 frontal are the usual seven small shields, filling up the space 

 between that shield and the canthals. 



In No. 37 the two supraocular shields are in contact with 

 the frontal, the usual small scales which intervene being 

 absent. 



These are the most conspicuous variations in the syncipital 

 shield in the series under notice. 



In no specimen was more than one row of scales present 

 between the eye and the labials. 



Summary of Variations. 



{a) The measurements given above indicate that adult 

 male adders vary in length from 18 to 24 inches. 



