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The Viperidæ belonging to this genus have the head very distinct from the neck, covered with small imbricate scales; the eyes rather small, with vertical pupils, separated from the lips by small scales; the nostrils directed upwards and outwards, usually pierced in a single nasal shield, with a rather deep pit above, closed by a valvular supranasal. The postfrontal bones are very large, in contact with the ectopterygoids. Scales keeled, with apical pits, in 22–41 rows; ventrals rounded. Tail very short; subcaudal scales in 2 rows.

(1) B. arietans (the Puff Adder; fig. 37).—This viper has the nostrils on the upper surface of the snout, and two series of scales between the supranasal shields; 12–16 supralabials; 3–5 lower labials. The scales on the body are in 29–41 rows, and strongly keeled; ventrals 131–145; subcaudals 16–34.

The body is thick, the head large and triangular, and the tail very short. The colour is dirty yellow or orange, with large, transverse or oblique, chevron-shaped black bands; an oblique black band extends behind the eye. The belly is dirty yellow, uniform, or marked with small black spots.

Total length, 1,350 millimetres, sometimes more; tail 160.

Fig. 36.—Skull of Bitis arietans (the Puff Adder). (After G. A. Boulenger, op. cit.)

Habitat: This snake is met with throughout Africa, from Southern Morocco, Kordofan, and Somaliland, to the Cape of Good Hope, and also in Southern Arabia. It is especially common near the Niger and on the Congo.

When irritated, it puffs itself out to such an extent that its body becomes twice the ordinary size. It then doubles back its head and neck in the shape of an S, and emits a loud and prolonged hiss. Before biting, it first strikes a blow with its head as with a battering-ram, thus justifying its French name, vipère heurtante (Striking Viper).

Fig. 37.—Bitis arietans (the Puff Adder). (After Duméril and Bibron.)

The natives of South Africa assert that this Viper is able to spring high enough to strike a rider on horseback. It feeds upon rats and mice, in search of which it often approaches habitations.

The Hottentots hunt it in order to obtain its venom; they pound its head between stones, and mix the pulp with the juice of certain plants for the purpose of poisoning their arrows.

It lives for a fairly long time in captivity. At the Pasteur Institute at Lille I have succeeded in keeping one of these snakes for two years, feeding it by forcing milk and eggs down its throat.

(2) B. peringueyi.—Nostrils opening upwards and outwards. Head covered with small, strongly keeled scales, which are smallest on the vertex; 11 scales round the eye; 3 series of scales between the eye and the lip; 11–14 supralabials. Scales on the body in 25–27 rows, strongly keeled; 130–132 ventrals; 19–28 subcaudals.

Colour greyish-olive, with 3 longitudinal series of grey or blackish spots; head sometimes with a trident-shaped dark mark, followed by a cross; under surface whitish, with small dark spots.

Total length, 325 millimetres; tail 26.

Habitat: Angola and Damaraland.

(3) B. atropos.—Nostrils opening upwards and outwards, 13–16 scales round the eye; 2–5 series of scales between the supranasals; 10–12 supralabials; 3–4 infralabials. Scales on the body in 29–31 rows, all strongly keeled; 124–145 ventrals; 18–29 subcaudals.

Colour brown or grey-brown, with 4 longitudinal series of dark spots, edged with black and white; two large black marks on the head; belly grey or brown, with darker spots.

Total length, 350 millimetres; tail 25.

Habitat: Cape of Good Hope.

(4) B. inornata.—Eyes smaller than in B. atropos, and separated from the lips by 4 series of scales; supraorbital region raised, but without erect horn-like scales; 15–17 scales across the head; 13–14 supralabials; 3 lower labials. Scales on the body in 27–29 rows, all keeled; 126–140 ventrals; 19–26 subcaudals.

Total length, 350 millimetres; tail 30.

Habitat: Cape of Good Hope.

(5) B. cornuta (fig. 38).—Nostrils opening upwards and outwards. Head covered with small, imbricate, strongly keeled scales; 2–5 raised scales, like horns, above each eye; 12–14 scales round the eye; 12–15 supralabials; 2–3 infralabials. Scales on the body keeled, in 25–29 rows; 120–152 ventrals; 18–36 subcaudals.

Colour grey or reddish-brown, with black spots, edged with white and arranged in 3 or 4 longitudinal series; a dark, oblique streak from the eye to the mouth; belly yellow or brown, uniform or spotted.

Total length, 510 millimetres; tail 35.

Fig. 38.—Bitis cornuta. (After Duméril and Bibron.)

Habitat: Cape Colony, Namaqualand, Damaraland.

(6) B. caudalis.—Nostrils opening upwards and outwards. 12–16 scales from one eye to the other across the head; above each eye a single, erect, horn-like scale; 10–16 scales round the eye; 10–13 supralabials; 2–3 infralabials. Scales on the body in 22–29 rows, strongly keeled; 112–153 ventrals; 18–33 subcaudals.

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.