234 VIPERID.E 



streak (as in some specimens of the var. seoanei, from 

 North-Western Spain). The markings may be absent 

 altogether (var. concolor, Jan), or reduced to a narrow 

 straight vertebral band (Pelias dorsalis, Gray). In 

 the var. seoanei the zigzag band is often replaced by 

 a dark brown vertebral band, three to five scales 

 wide, bordered on each side by a series of subtriangu- 

 lar or crescentic black spots opposite to each other, 

 as in the Pyrenean specimens of V. aspis. A pair of 

 elongate dark markings are usually present on the 

 back of the head, affecting the following shapes : 

 J\,X#)Vi )(i By uniting together, this pair of mark- 

 ings may form a A or an X. An oblique dark streak 

 extends on each side from the eye to the last labial 

 shields, being sometimes prolonged a short way down 

 the neck. The snout and vertex may be uniform or 

 bear some symmetrical dark spots, or in some males 

 be entirely black, the black involving the apex of the 

 A-shaped marking. The labial shields are whitish or 

 yellowish, those at least which are anterior to the 

 eye being more or less broadly edged with brown or 

 black. 



The belly and the lower surface of the tail vary 

 from grey or brown to bluish, blackish-grey, or black, 

 the sides usually dotted or spotted with whitish ; 

 sometimes, especially in females, the belly is dark 

 grey, each shield with a white posterior border which 

 is broken up by a series of small roundish black spots. 

 The end of the tail is often yellowish, bright yellow, 



