240 GECKOTIANS. IGUANIANS. 



external ones for canines : behind these there is a series of molar teeth 

 with compressed triangular and tricuspid crowns, the median cusp 

 being much the largest of the three : these teeth increase in size 

 towards the back part of the jaws. 



GECKOTIANS. 



101 . In this family of nocturnal insectivorous Lizards the teeth are 

 more pointed, more slender, more equable and more numerous than 

 in the preceding group. The summit of the tooth is always simple : 

 the base is obliquely soldered to the internal surface of an outer 

 alveolar parapet. 



In the smooth Gecko {Thecadnctylus lavis, PL 66, fig. 4), there 

 are about thirty-five such teeth, forming a close-set series on each 

 side of both jaws ; the first five or six above being supported on the 

 intermaxillary bones, and being rather longer than the rest. In most 

 of the posterior teeth the crown is slightly expanded, with a trenchant 

 margin, as shown in fig. 44' ; its transverse section is given below. In 

 the flat-headed Gecko (Ptyadactylus fimhriatus, Cuv.) there are 

 from seventy to seventy-four teeth on each side. In the House- 

 Gecko {Ptyadactylus Hasselquistii) the teeth are slightly recurved. In 

 the common Indian Gecko {Ptyadactylus guttatus, Cuv.) the teeth, 

 with the exception of a few anterior ones, are rather cylindrical than 

 conical, and are terminated by obtuse summits. None of the Geckos 

 have teeth on the roof of the mouth. 



IGUANIANS. 



102. The lizards of this family are characterized like the preceding 

 groups by a short contractile tongue, slightly notched at its extremity ; 

 but are distinguished for the most part by having teeth on the pterygoid 

 bone, and also by the complicated form of the crown of the max- 

 illary teeth in the typical genera, the species of which subsist 

 chiefly on vegetable substances. 



In most of the Iguanians the teeth are lodged in a common 

 shallow oblique alveolar groove, and are soldered to excavations on 

 the inner surface of the outer wall of the groove. MM. Dumeril and 

 Bibron enumerate the following genera as exhibiting the pleurodont 

 type of dentition, and as possessing likewise pterygoid teeth : viz. 



