Colour reddish or sandy-grey, with 2 series of brown spots with light centres, and frequently a vertebral series of narrow spots; belly dull yellow, uniform, or with small black spots on the sides. Total length, 360 millimetres; tail 25. _Habitat_: South-west Africa, from Angola to Namaqualand. (7) _B. gabonica_ (Gaboon Viper, or River Jack Viper).--Nostrils directed upwards and outwards. Head covered with small, moderately keeled scales, smallest on the vertex, 13-16 from eye to eye; 15-19 scales round the eye; a pair of erectile, triangular, nasal “horns,” consisting of sometimes tricuspid shields, between the supranasals; 13-16 supralabials; 4-5 infralabials. Scales on the body in 33-41 rows, strongly keeled; lateral scales slightly oblique; 125-140 ventrals; 17-33 subcaudals. This viper, which often attains a length of 1,200 millimetres, is brown, with a vertebral series of quadrangular, yellowish, or light brown spots connected by black markings; the belly is dull yellow, with small brown or blackish spots. _Habitat_: Tropical Africa (West Africa, from Liberia to Damaraland; Zanzibar, Mozambique). This species, which is nocturnal, is often met with on the Gaboon, and in the forests near the banks of the Ogowai. Its head is enormous, triangular in shape, and wider above; it has a bulky body, and a very short tail, terminating abruptly in a point. The Gaboon Viper is a savage snake, with very active venom, and its poison-glands are of the size of large almonds. It lives in virgin forests, among dead wood and rocks. I have several times met with it in manioc plantations on the edge of the woods. In broad daylight it is sluggish, moves somewhat slowly, and never attacks man. It bites only when surprised. [Illustration: FIG. 39.--_Bitis nasicornis._ (After Duméril and Bibron.)] (8) _B. nasicornis_ (fig. 39).--Nostrils opening upwards and outwards. Head covered with small strongly keeled scales, smaller on the vertex, 14-16 from one eye to the other; 2 or 3 pairs of compressed, erectile, horn-like shields between the supranasals, usually separated in the middle by 1 or 2 series of small scales; 15-18 supralabials; 4-6 infralabials. Scales on the body in 35-41 rows, strongly keeled; 124-140 ventrals; 16-32 subcaudals. Colour purple or reddish-brown above, with pale olive or dark brown spots; a vertebral series of brown, black-edged spots, which assume a rhomboidal form; sides of head dark brown, with a triangular light mark in front of the eye, and an oblique light streak from behind the eye to the mouth; belly pale olive, spotted with black or yellow. Total length, 1,250 millimetres; tail 125. _Habitat_: West Africa, from Liberia to the Gaboon. (d) =Cerastes.=