232 VIPERID.E 



thals, the second of which is usually in contact with 

 the supraocular; canthals very rarely united into one 

 shield ; the space between these shields covered by 

 four to twenty flat or convex, juxtaposed scales, 

 which very exceptionally are fused into a single 

 large shield. Supraocular usually extending pos- 

 teriorly beyond the vertical of the eye. Six to thir- 

 teen scales round the eye, usually eight to ten ; two 

 or three superposed scales, rarely two vertical series 

 of scales, separate the preoculars from the nasal, 

 which is single. As a rule a single series of scales 

 intervenes between the eye and the labials ; specimens 

 with two series are of very exceptional occurrence 

 (single specimens from Isle of Arran, Normandy, 

 Southern Norway, and Carniola, in the British 

 Museum), but there are occasionally two series 

 except just below the centre of the eye. Upper labials 

 six to ten, usually eight or nine ; fourth or fourth 

 and fifth (rarely third and fourth) below the eye. 

 Temporal scales smooth, rarely feebly keeled. Three 

 or four (rarely five) lower labials in contact with 

 the single pair of chin-shields. 



Scales in twenty-one (rarely nineteen or twenty- 

 three) rows, with two apical pits, strongly keeled, 

 those of the outer row smooth or feebly keeled. 

 Ventral shields 132 to 150 (usually 137 to 147) in 

 males, 132 to 158 (usually 140 to 150) in females; 

 anal entire ; subcaudals 32 to 46 (usually 35 to 40) 

 in males, 24 to 38 (usually 28 to 33) in females. 



