Head very distinct from the neck, covered with small juxtaposed or slightly imbricate scales; eyes small, with vertical pupils, separated from the lips by small scales; nostrils opening upwards and outwards. Body cylindrical; scales keeled, with apical pits, in 23-35 rows. Tail short; subcaudals in 2 rows. (1) _C. cornutus_ (fig. 40).--Snout very short and broad; two erectile horns above the eyes, which are separated by 15-21 scales and surrounded by 14-18; 4-5 series of scales between the eyes and the lips; 12-15 supralabials; 3 infralabials; scales on the body in 27-35 rows; 130-165 ventrals; 25-42 subcaudals. [Illustration: FIG. 40.--_Cerastes cornutus._ (After Duméril and Bibron.)] Colour yellowish-brown or grey, with or without brown spots, forming 4-6 regular series, the two middle ones sometimes forming cross-bars; an oblique dark streak behind the eye; belly white; end of tail sometimes black. Total length, 720 millimetres; tail 90. _Habitat_: Northern border of the Sahara, Egypt, Nubia, Arabia, and Southern Palestine. (2) _C. vipera._--Snout very short and broad; head covered with small, tubercularly keeled scales, to the number of 9-13 from eye to eye; no “horns”; 9-14 scales round the eye; nostril between two small shields, separated from their neighbours by 5-6 series of scales; 10-12 supralabials; 3 infralabials. Scales on the body in 23-27 rows; 102-122 ventrals, rather strongly keeled at the sides; 18-26 subcaudals. Colour dull yellow, pale brown or reddish, with or without black spots; end of tail often black above; ventral surface white. Total length, 340 millimetres; tail 30. _Habitat_: Northern border of the Sahara, from Algeria to Egypt. The snakes belonging to this genus live constantly hidden in the sand, lying in wait for small birds, which alight beside them without suspicion, mistaking their horns for insects or larvæ; they also feed upon mice. Their poison-fangs are of relatively large size. These small and exceedingly active vipers, whose colour harmonises marvellously with their surroundings, are very dangerous to the Arabs and blacks, who walk barefooted; they frequently cause fatal accidents. They are able to exist for a very long time without drinking. They are attracted by the fires which are lighted at night round caravan encampments. (e) =Echis.= (See Asia, p. 48.) (1) _E. carinatus_ (Efa, Viper of the Pyramids).--The same as met with in Persia, Arabia, and India. Very common in the environs of Cairo, and throughout Egypt and Abyssinia. It often makes its way into towns and villages. Brehm records that he more than once found an _Efa_ in his house at Khartoum, and that on one occasion he discovered one of these vipers coiled up beneath the covering of his bed. At another time, getting up in the night, he put his foot on one of these animals and was not bitten, the reptile being very fortunately just at that moment in the act of devouring a tame bird which it had seized.