408 REPTILIA— ORDER III.-SQUAMATA. 



all external traces of the hinder pair of limbs, and as such species possess 

 burrowing habits, they may be regarded as forming a con- 

 Family necting link between the Teiidce and the degraded Amphis- 

 Amphisbctnidce. bcenidce. The latter, which take their name from the fact 

 that most of them are able to advance with equal ease in 

 either a forward or a backward direction, may, indeed, in all probability, be 

 considered as derivatives from the ancestral stock of the former, which have 

 little by little accustomed themselves to a subterranean mode of lite, till the 

 majority have acquired an ahnost completely worm-like form and habit. One 

 American species, alone representing the genus Chirotes, still, however, retains 

 minute though well-developed fore-limbs, which are placed close up to the head, 

 and followed by the long worm-like body. And to the zoologist this form is of 

 the hijjhest importance, as indicating that all the other members of the family 

 trace their origin to fully -limbed ancestors. With the exception of this soli- 

 tary species, the amphisbsenas are all limbless, worm-like creatures, in which 

 even the bones of the pelvis and shoulder-girdle are reduced to the condition 

 of rudiments. In all, the ears are wanting, the functionless eyes are buried 

 deep down in the skin, and the minute mouth is often situated on the lower 

 aspect of the head. The tail is always short; and the few and large teeth, as 

 in the preceding family, may be either acrodont or pleurodont. Indeed, it is 

 chiefly by certain degraded features of the skull that the Ampliisbcenidce are 

 distinguished from the Teiidcn; and as such differences are obviously produced 

 by adaptation to their environment, the amphisbsenas are but little removed 

 from their nearest allies. Not the least interesting feature in connection with 

 these strange creatures is their peculiar geographical distribution — a distribu- 

 tion wliich can only be understood by taking extinct forms into consideration. 

 Of the existing types, the true home is Tropical America, although two 

 species — one representing Chirotes — are found above the northern tropic ; 

 but a considerable number of species are inhabitants of Africa, and a few 

 occur in the Mediterranean countries. Most remarkable is the circumstance 

 that the extensive and typical genus Amphisbceiia has representatives both 

 in Tropical America and Africa south of the Sahara. This, however, is but 

 one out of many instances showing a community between the famias of 

 South Africa and South America. The family is divided into two groups, 

 according to the mode of attachment of the teeth. In the first group, or 

 Prosphyodontes, which includes Chirotes, Amphisbcena, and six other genera, 

 the teeth are welded to the inner edges of the jaws ; whereas in the second 

 group, or Emphyodontes, which is represented by TrotjonopMs, Pachycalmus, 

 and Agamodon, they are affixed to the edges of the same. Regarding the 

 mode of life of the amphisbrenas, Mr. G. A. Boulenger writes as follows :— 

 " All the members of this family are burrowers, and many li^e in ants' nests. 

 They bore narrow galleries in the earth, in which they are able to progress 

 backwards as well as forwards. On the ground they progress in a straight 

 line, by slight vertical undulations, not by lateral movements, as in other 

 limbless reptiles. The tail of many species appears to be more or less pre- 

 hensile. The food of these lizards consists of small insects and worms. Little 

 has been published on their habits, and all that is known about their mode of 

 proi)agation is that Anops kincji is oviparous, and deposits its eggs in the 

 nests of ants." It may be added that the Amphisbcenidai are peculiar- among 

 vertebrates in having the right lung rudimental or absent, whereas the left is 

 elongated. In other snake-like lizards, and in snakes, it is the right lung 

 that is functional. 



