CROCODILIANS, LIZARDS, AND HNAKES. 453 



The teguments are nearly always soft and consist generally of granules or tuber- 

 cules on the dorsal surface, of small imbricated cycloid or hexagonal scales on the 

 ventral surface. Some Geckos are entirely covered with scales of the latter descrip- 

 tion, which attain their highest development in Teratoscincua, Teratolepis, and 

 Gevkolepifi. 



The habits of the Geckos are highly interesting and deserve special atteution, as 

 butfew observations have been made on them. Some inhabit arid regions, sometimes 

 burrowing in the sand; others are arboreal, living on shrubs or in woods, concealing 

 themselves under stones or under the bark of trees during the daytime; others live 

 on rocks; others have become the commensals of man, and they again may be divided 

 into two groups — those living inside, those living outside houses. Most are noc- 

 turnal, but some are diurnal. Colonel Tytler, in a very interesting paper on the 

 habits of Geckos, observes that, "although several species of Geckos may inhaltit 

 the same locality, yet, as a general rule, they keep sejiarate and aloof from each 

 other; for instance, in a house the dark cellars may be the resort of one species, the 

 roof of another, and crevices in a wall may be exclusively occupied by a third 

 species. However, at night they issue forth in quest of insects, and may be found 

 mixed up together in the same spot; but on the slightest disturbance, or when they 

 have done f(;ediug, they return hurriedly to their particular hiding places."' 



Many Geckos utter sounds, probably produced chiefly by a movement of the 

 tongue against the palate, and in which yecko, chuvko, fockee. or something similar is 

 distinctly audible. A. Smith says that a South-African sand Gecko (Ptenoptis 

 garruhis) utters during the day a sharp sound somewhat like chick, chick; and he 

 adds that the number thus occupied is at times so great, and the noise so disagree- 

 able, as to cause the traveler to change his quarters. 



The eggs are round and with a hard shell. Ovoviviparism has not been observed 

 in this family. Males are generally distinguished from females by a larger si/e, the 

 swelling of the base of the tail, and the presence of femoral or pra-anal pores, which 

 are constantly absent in the latter. 



The Geckonidie are represented in the hotter parts of all the regions of the world. 

 They are most numerous in the Indian and Australian regions. 



The following syiioi)sis of the geuera is chietly derived from Bouleiiiivr : 



I. Digits short, cylindrical, the skin swollen on the i)aluiar surface and under the 



articulations. 

 Digits clawed; tail extremely short, terminating in a globular knob. 



Xcjyhrurus Giinther. 

 Xo claws t'hondrodactjihiH Peters. 



II, Digits straight, not dilated, clawed, without pa<ls. 



Digits granular inferiorly, not fringed laterally; rostral and mental plates pro- 

 jecting, nail-like h'hyxchaditfa (Jiinther. 



Digits granular mferiorly, strongly fringed laterally; dorsal scales large, 

 imbricate Teratoscinciis Strauch. 



Digits covered inferiorly with suiall iui])rirate pointed scales; dorsal scales 

 small Ceramodactylus Blanford. 



Digits inferiorly with a series of narrow transverse plates; toes strongly fringed 

 laterally ; fingers not fringed Ptenopus (iray. 



Digits inferiorly with a series of narrow transverse plates, fringed or denticu- 

 lated laterally Stetioductijlus Fitzinger. 



Digits inferiorly with a scries of narrow transverse plates, not fringed nor 

 denticulated laterally ; dorsal scales juxtaposed; male with a series of 

 pneanal ])ores J/soj>/i(/?(/.c Fitzinger. 



Digits interiorly with a series of narrow transverse plates, not fringed nor den- 

 ticulated laterally; dorsal scales imbricate; no praanal i)ores. 



Homonota Gray. 



