REPTILIA. 275 



have indications of a posterior pair of extremities, in tlie form of scalj^, un- 

 divided appendages, one on each side of the anus. The single species is 

 known in Russia as the sheltopusik. The genus Chalcides, whose species are 

 mainly South American, has both pairs of extremities, but in a rudimentary 

 state. The anterior pair terminates in three or four scaly tubercles, while the 

 posterior is represented by two slender spines. By the absence of an external 

 auditory cavity, it is distinguished from Chamccsmirits, in which none of the 

 rudimentary extremities exhibit any subdivision. The genus iSaurophis in- 

 troduces us to the species having more highly developed extremities. Here 

 each foot has four toes. The single species known, S. tetradactyla {pi. 74, 

 Jiff. 67), inhabits the southern portions of Africa. The remaining genera 

 have five toes on each foot ; the most interesting of these is the genus 

 Gerrhoiioius, which, represented by eight species, inhabits Mexico and 

 California. 



The second sub-family, that of the Gli/ptodermes, corresponds very nearly 

 to the family AmphisbienidjB of some authors. Here the body is entirely 

 creprived of scales, in place of which the skin is divided by circular and longi- 

 tudinal furrows into small quadrilateral compartments, sometimes variously 

 colored, and then resembling mosaic work. These subdivisions are generally 

 slightl}^ tubercular and projecting. There are faint indications of the lateral 

 furrow of the more typical Chalcididcc. Most of the species bear a strikino* 

 resemblance to the Ophidia, with which they have usually been classed ; 

 they may, however, be distinguished by the entirely saurian skull, with the 

 symphisis of the two halves of the lower jaw ; by the saurian tongue ; 

 and by the fact that the vertebrae are united by fibro-cartilage. In one 

 of the ophioid genera, Ti'ogonophis, the teeth are acrodont, or attached 

 on the cutting edge of the jaws, while in all theirest they are pleurodont, 

 or applied along the inner edge. The gQimW Ainphishama, or double 

 walkers, are so called from the close resemblance between the anterior 

 and posterior extremities of the membranous body. They appear as if 

 possessing a head at each end, and are hence supposed to be capable of pro- 

 gression in either direction. They are often found in the nest of the termites, 

 where they feed upon the young ants. The genus Chirotes presents the 

 remarkable anomaly among saurians of having two fore feet, each with five 

 fingers. In the absence of hind feet, the anterior being present, we see 

 a strong resemblance to the batrachian genus Siren. The presence of a 

 sternum further distinguishes Chirotes from Arnphishama. The single 

 species, Chirotes caiialiadatiis, is found in various parts of Mexico, 

 extending northwards along the eastern base of the Rocky Moun- 

 tains. 



Fam. 3. Lacertida. Species of this family have a cylindrical elongated 

 body, with the tail sometimes of very great length, and always well developed. 

 The feet are four in number, with four or five distinct toes of unequal 

 length, all provided with curved claws. The head is in the shape of a 

 truncated four-sided pyramid, depressed, and covered with polygonal sym- 

 metrical plates. The typanum is distinct, sometimes externally apparent. 

 Eyes usually with three movable eyelids. The mouth is deeply cleft, and 



4V9 



