Colour yellowish or pale brown above, grey or dark brown on the sides, sometimes uniform brown; spots more or less regular on the vertebral column, oval, elliptic or rhomboidal, dark brown or flecked with white, sometimes forming an undulous or zigzag band; two or three longitudinal series of dark brown or black spots on the sides; small dark dots running obliquely from the eye to the angle of the mouth; nose and lips white, and one or two dark angular streaks on the head; chin and throat yellowish; belly black, with transverse series of white or grey dots. No sexual differences in coloration. Total length from 420-500 millimetres; tail 50-55. _Habitat_: South-east France (Basses-Alpes); Italy (Abruzzi); Istria; Mountains of Bosnia; Plains of Lower Austria; Hungary (environs of Buda-Pesth). Vipera berus (_Common Viper_, or _Adder_). Snout rounded, short and truncate; pupil vertically elongate; vertical diameter of the eyes equal to or greater than the distance separating them from the mouth; frontal and parietal shields distinct, the former as long as broad, usually shorter than the space separating it from the rostral shield; 6-13 scales round the eyes; one or rarely two series of scales between the eyes and the lips; nasal shield single, separated from the rostral by a naso-rostral shield; temporal scales smooth. Body scales in 21 rows (exceptionally 19 or 23), strongly keeled; 132-150 ventral shields; 38-36 subcaudals. [Illustration: FIG. 21.--(_1_) _Vipera berus_; (_2_) _Vipera aspis_; (_3_, _4_) _Vipera ammodytes_. (Natural size.)] Colour very variable, grey, yellowish, olive, brown, or red above, generally with an undulating or zigzag band along the vertebral column, and a series of lateral spots. A black spot shaped like a =V=, an =X=, or a circumflex accent, on the head. The tip of the tail is yellow or reddish. Some specimens are entirely black. Total length from 350 to 700 millimetres; tail 75 to 90. _Habitat_: Northern Europe, and especially the mountains of Central Europe; irregularly distributed in Southern Europe; Northern Spain and Portugal, Northern Italy, Bosnia, Caucasus. * * * * * This viper, which is very common in France, ranges as far as the Scandinavian Peninsula to about the 65th parallel of North Latitude. It is sometimes met with among the mountains at an altitude of about 6,500 feet (2,000 metres). It is found on heaths, in grass-lands, vineyards, and forests. Certain parts of the sandy moors of North Germany are literally infested with it. It abounds in the Jura, Isère, Ardèche, Auvergne, Brittany, Vendée, and the Forest of Fontainebleau. It seeks its prey by night, and feeds on voles, small birds, frogs, lizards, and small fish. During the summer it shows a preference for moist places, often even remaining in the water, in which it swims with ease.