188 REPTILIA. 



FAMILY II. 



SERPENTIA. 



The true Serpents, which are by far the most numerous, comprise 

 the genera without a sternum, and in which there is no vestige of a 

 shoulder, but where the ribs still surround a great part of the circum- 

 ference of the trunk, and where the body of each vertebra is still 

 articulated by a convex surface to a cavity in the succeeding one. 

 The third eye-lid and the tympanum are deficient; but the malleus of 

 the ear exists under the skin, and its handle passes behind the 

 tympanum. There is still a vestige of a posterior limb, concealed 

 under the skin, in several of this family, and which in some of them 

 shows its extremity externally in the form of a small hook. 



We subdivide them into two tribes. 



That of the AMPHiSBiEN^E, as in the preceding reptiles, still has 

 the lower jaw supported by a tympanal bone directly articulated with 

 the cranium, the two branches of this jaw soldered together in front, 

 and those of the upper one fixed to the cranium and to the inter- 

 maxillary bone, circumstances which prevent that dilatation of the 

 mouth which obtains in the succeeding tribe, and which occasions 

 a uniformity of the head and body, a form which enables them to 

 move backwards or forwards with equal facility. The bony frame 

 of the orbit is incomplete behind, and the eye very small; the body 

 is covered with scales, the trachea long, and the heart very far back. 

 They are not venomous. 



They form two genera, one of which is allied to Chalcides and 

 Chirotes, and the other to Anguis and Acontias. 



Amphisbjena, L.(1) 

 The whole body surrounded with circular ranges of quadrangular scales, 

 like the Chalcides and the Chirotes among the Saurltns; a few conical teeth 

 in the jaws, but none in the palate. There is but one lung. 



Two species have long been known, Amph. alba, Lacep., and Amph. full- 

 ginosa, Jj., both from South America. They feed on Insects, and are often 

 found in Ant-hills, which has occasioned a belief among the people that the 

 large Ants are their purveyors. They are oviparous. 



(1) From ctfAtpti and QaIvuv, walkmg both ways. The ancienta attributed 

 two heads to it. 



