THE PBINGIPAL SPECIES OF POISONOUS SNAKES 27 



capable of finding their own food. Their length at birth amounts 

 to 230 millimetres. 



The two glands of an adult adder contain about 10 centigrammes 

 of poison. This small quantity is sometimes sufficient to cause 

 death ; out of 610 persons bitten, Eolhnger returns 59 deaths, or 

 about 10 per cent. 



In the departments of Vendee and Loire-Inferieure alone, Viaud 

 Grand Marais has noted during a period of six years 321 cases of 

 bites from adders, 62 of which were followed by death. In 

 Auvergne, Dr. Fredet' (of Eoyat) returns 14 cases, which caused 6 

 deaths. 



Yipera aspis (Asp, or Bed Viper). 



(Pig. 21, 2, and fig. 22.) 



Snout slightly turned up, soft and squarely truncate ; vertical 

 diameter of the eyes equal to the space separating them from the 

 mouth ; upper surface of the head usually covered with small, 

 imbricate, smooth or feebly keeled scales, in 4 — 7 series, between 

 the supraocular shields, which are prominent. The frontal and 

 parietal shields are usually wanting ; sometimes they are distinct, 

 but small and irregular ; the former are separated from the supra- 

 oculars by two series of scales ; 8 — 13 scales round the eyes ; two 

 (rarely three) series of scales v between the eyes and the labials; 

 nasal shield single, separated from the rostral by a naso-rostral 

 shield. Body scales in 21 — 23 rows, strongly keeled ; 134 — 158 

 ventrals ; 32 — 49 subcaudals. 



Coloration very variable, grey, yellowish, brown, or red above, 

 with a zigzag band as in V. berus. Usually a black U-shaped 

 mark on the hinder part of the head, with a longitudinal black 

 streak behind the eyes ; upper lip white, or yellowish. Ventral 

 surface yellow, white, grey, or black, with lighter or darker markings. 



Total length, 620—675 millimetres ; tail 75—95. 



Acad, dc medecine, March 19, 1889. 



