540 LACERTAE chap. 



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 de- 

 veloped, and burst the transparent, soft, yellowish eggs immedi- 

 ately 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 snails. 

 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.^ 



HelocUrma, the only genus, with H. horridum in Mexico and 

 H. suspectum in New Mexico and Arizona, reaches about 2 feet 



' For further anatomical details see Shufeldt, P.Z.8. 1890, i). 148 ; Boulenger, 

 P.Z.S. 1891, p. 109 ; and Stewart, P.Z.S. 1891, p. 119. 



