Fig. 136.–Anguis fragilis (the Slow-worm). × ½.
Anguis, with only one species, A. fragilis, the "Slow-worm" or "Blind-worm," is devoid of a lateral fold. Limbs are entirely absent. The whole body is covered with smooth roundish scales, with a substratum of dermal ossifications. The teeth are curved backwards, fang-shaped, and have a very faint longitudinal groove on their anterior surface. The ear-opening is very minute, more or less hidden by surrounding scales. The eyes are perfectly well developed, provided with movable lids, and it does not speak well for the power of observation of most people that this creature should generally be known as the "Blind-worm." The whole skin is shiny, metallic, quite smooth, brown above, blackish below. But the coloration is subject to much individual variation. Old specimens are sometimes adorned with blue specks. The very young are exquisitely beautiful, the upper surface being silvery white, with a median and two more lateral lines of deep black; the under parts are black. The iris is yellowish red. Very large specimens measure more than one foot in length, more than half of which belongs to the tail. One in the British Museum is 425 mm. = 17 inches long.
The Slow-worm is viviparous, i.e. the young are fully developed, and burst the transparent, soft, yellowish eggs immediately after these are laid. This takes place in the months of August or September, about one dozen making a litter. The little creatures are at first about one inch and a half long, and as thin as an ordinary match. They eat the smallest of spiders and delicate insects; later on earth-worms, which they bite into and then suck out before devouring them. When six weeks old and well fed they are about 3 inches long, but it is at least four or five years before they are mature. The little ones carefully avoid the hot sunshine, and the adults are likewise rather partial to the shade, although strictly diurnal. Their chief food consists of earth-worms and slugs. For the night they retire under moss, leaves, stones, or into the ground. In the autumn the Slow-worms dig passages or burrows, which often serve as the winter-quarters of many specimens, as if there were no other place available, or rather as if the spot selected were by far the best with regard to safety, dryness, and warmth.
Fam. 6. Helodermatidae.–Pleurodont, poisonous lizards of North America. The teeth are fang-like, recurved, with slightly swollen bases, rather loosely attached to the inner edge of the jaws. Each tooth has a groove on its anterior and posterior surface, and a series of labial glands which secrete the poison open near the bases of the teeth of the lower jaw. The skull has strong postorbital but no postfronto-squamosal arches. The pre- and post-frontals are in contact, separating the frontal from the orbit; the premaxillaries are fused into one; the nasals and frontals remain separate. The limbs are short, but strong and well developed. The tongue is villose, with an anterior smooth portion, which is bifid and protractile, resembling the tongue of the Anguidae and of Aniella. The skin of the upper surface is granular, with many irregular bony tubercles, which give it an ugly warty look. The under parts are covered with flat scales.[[161]]
Heloderma, the only genus, with H. horridum in Mexico and H. suspectum in New Mexico and Arizona, reaches about 2 feet in length. The animal, stout, depressed, thick-tailed, looks rather repulsive when it squats down in its usual lethargic way. The whole skin is blackish brown and yellow or orange, these two "warning" colours being distributed unevenly, except on the thick, peculiarly-shaped tail, where they are arranged in alternate rings. The specific differences are rather imaginary. The New Mexican form is supposed to be more orange and yellow than black, with a somewhat smoother skin and with shorter toes and tail.
Fig. 137.–Heloderma suspectum (the Gila Monster). × ⅕.
The "Gila Monster" inhabits dry localities, spends most of the daytime in concealment between the roots of trees, and crawls about in the evening in search of worms, centipedes, frogs, and the eggs of large lizards. Frogs are probably paralysed or killed by the bite which, although not so dangerous as that of poisonous snakes, is effective enough to produce severe symptoms even on man, and a few cases of death of people who had been bitten are on record. In captivity they are very partial to eggs, which they break and then lap up. During the dry and hot season they aestivate.
Fam. 7. Lanthanotidae.–Lanthanotus borneensis, of which only two specimens are known, one in the Vienna Museum, the other in the Sarawak Museum, was described by Steindachner as the type of a distinct family, near the Helodermatidae. Boulenger,[[162]] after examination of the Sarawak specimen by means of a sciagraph, has come to the conclusion "that the affinity of Lanthanotus to the Helodermatidae is fully confirmed." The teeth of Lanthanotus show, however, no traces of grooves; poison-glands are probably absent, and there are no osteoderms. The skin is covered with wart-like tubercles, each with a horny, peeled scale. The eyes are very small, the ears are concealed. The general colour is reddish brown above, yellowish, with brownish bands, below. Total length about one foot, a little more than half of which belongs to the roundish tail.