278 REPTILIA. 



A second subdivision is formed of the Hemidactyles, which have an oval disk at the base of their toes, formed 

 by a double range of chevron scales underneath ; the middle of this disk elevates the second phalanx, which is 

 slender, and bears the third, with its claw, at the extremity. The known species have all five claws, and the range 

 of pores on either side of the anus ; the scales underneath the tail form broad bands, as in the true Serpents. 



A third subdivision, which I style Thecadactyles, have toes widened throughout their length, and furnished 

 with transverse scales underneath, but which latter are divided by a deep longitudinal groove, into which the 

 claw retracts completely. Those known to me have the thumb alone clawiess, no femoral pores, and the tail 

 covered with little scales both above and below. 



The fourth subdivision of Geckos, I term Ptyodactyles. These have only the ends of their toes dilated into 

 plates, with a fan-like structure beneath ; the middle of the plate being split, and the claw placed in its fissure. 

 They have very crooked claws on all their toes. 



Some have a round tail, and five toes ; while others have the tail bordered with a membrane on each side, and 

 the toes palmated. It is probable that the latter are aquatic, and they are the Uroplates of Dumeril. 



A fifth subdivision is composed of the Xp/tcriodactyles, — which are certain small Geckos, the ends of the toes of 

 which are terminated by a little palette without folds, but the claws of which are always retractile^ Those in which 

 the palette is double, or emarginated in front, approximate the round-tailed Ptyodactyles. More frequently, how- 

 ever, the palette is round and simple. All the known species are from India and the Cape. 



Finally, there are certain of these Saurians w hich, with all the other characters of the Geckos, have the toes not 

 widened. Their claws, five in number, are nevertheless retractile. Some of these, with a round tail, and the toes 

 striated beneath, having dentelated edges, constitute the Stenodacfyles ; — and there are others with slender and 

 naked toes, and also a round tail, which are the Gymnodactylcs of Spix. 



Some, again, have the tail horizontally flattened, in the form of a leaf, which 1 denominate Phillurus. 



One species only is as yet known, from New Holland. 



THE FIFTH FAMILY OF THE SAURIANS,— 



The Chameleons (Chamceleo, Lin.), — 



Are so very distinct from the other Saurians that it is not easy to intercalate them in the series. 



All have the skin roughened with little scaly granules ; the body compressed, and the dorsal line 

 sharp ; tail round and prehensile ; five toes on each foot, hut divided into two opposite sets, one con- 

 sisting of two toes, and the other of the remainder, — the toes of each of these sets being connected by 

 skin as far as the nails ; the tongue is fleshy, cylindrical, and extremely protrusile ; the teeth trilo- 

 bate; the eyes large, hut almost covered by the skin, which leaves only a little aperture opposite the 

 pupil, and they are moveable independently one of the other ; the ear not visible externally, and the 

 occiput pyramidically raised. Their first ribs are joined to the sternum, and the remainder are each 

 continued to join the corresponding rib of the other side, encircling the abdomen by complete hoops. 

 The lung is so vast that, when inflated, the body appears transparent, and induced the ancients to 

 believe that these animals fed upon air. They subsist on insects, which they take with the glutinous 

 extremity of the tongue, which organ is the only part of them that moves quickly. The motion of the 

 limbs is excessively slow. The magnitude of the lung is probably the indirect cause of their changing 

 colour, which does not take place, as is currently supposed, for the purpose of assimilating them to the 

 proximate surfaces, but according to their wants and passions. Their lung, in fact, renders them more 

 or less transparent, by forcing the blood more or less into the vessels of the skin, the colour even of 

 this fluid being mere or less vivid according as the lung is distended with air. They are constantly 

 found upon trees. 



[These most singular animals are particularly remarkable for the diminished sympathy of the two sides of their 

 whole frame, one of which may be asleep and the other awake, one of one colour and the other of another, &c, — 

 the separate movement of their eyes being merely another phase of the same phenomenon : hence it is remarkable, 

 that, unlike most other animals, the Chameleon is totally unable to swim, from the incapability of its limbs 

 of acting in due concert.] 



THE SIXTH FAMILY OF THE SAURIANS,— 

 The Scindoidiens, — 



Are recognized by the shortness of their feet, the non-extensibility of the tongue, and the equality of 

 the tile-like scales which cover the whole body and tail. 



The Scinques (Scijicus, Daud.) — 

 Have four very short feet, a body of nearly the same calibre with the tail, no occipital hulge, no crest 

 or throat appendage, and the scales uniform and shining, and disposed tile-fashion like those of a Carp. 



