2488 SCALED REPTILES 



lids, and the drum of the ear is frequently exposed. Both groups, again, have two 

 pairs of limbs, which may be relatively longer or shorter in the different genera, 

 but are each provided with five toes. The length of the tail is subject to a large 

 amount of variation, although it generally exceeds that of the head and body. 

 Moreover, the two families resemble one another in the form and structure of the 

 tongue, which is thick, short, scarcely notched, and generally fixed to the floor of 

 the mouth throughout its length. When, however, we come to contrast the teeth 

 of iguanoids with those of agamoids, we find a striking difference which at once 

 serves to draw a sharp line of distinction between the two families. As we have 

 already seen, in the latter group the teeth are attached to the very summits of the 

 bones of the jaws (acrodout), and are commonly differentiated into front teeth, 

 tusks, and cheek teeth. In the iguanoids, on the other hand, the tall and cylin- 

 drical teeth are attached by their sides to the outer wall of the jaws in the so-called 

 pleurodont manner; the whole series being generally more or less uniform in char- 

 acter, and without any large projecting tusks. In the typical iguanas the teeth 

 have somewhat diamond -shaped compressed crowns with serrated edges; and it was 

 from a superficial resemblance to this type of tooth that the teeth of the great di- 

 nosaurian reptile from the English Wealden received the name of Iguanodon. A 

 few genera, again, have the teeth divided into three lobes, thus resembling a fleur- 

 de-lis. Many species of the family are further characterized by having teeth on 

 the pterygoid bones of the palate, while a single genus is one of the few lizards in 

 which there are teeth on the palatine bones. 



The iguanoids, which comprise about three hundred species, arranged in fifty 

 genera, may be regarded as especially characteristic of South and Central America, 

 although they extend into the warmer parts of the northern half of that continent, 

 ranging in the west as far as British Columbia, and in the east to Arkansas and 

 the Southern United States, while they are also represented in many of the Amer- 

 ican islands. Their occurrence in Madagascar (where, as in America, agamoids 

 are wanting) has been already mentioned, and it is probable that this remarkable 

 instance of discontinuous distribution may be explained by the occurrence of fossil 

 remains of species of the family in the upper Eocene rocks of France, where aga- 

 moids seem likewise to have been wanting. 



Very variable in external appearance, iguanoids present equal diversity in their 

 modes of life, and it is not a little curious that, with the exception of the flying 

 lizard, almost every group of the agamoids finds a parallel, both as regards struc- 

 ture and habits, in the present family; the two families being thus representative 

 groups. There are, however, certain iguanoids, such as the anolis lizards and the 

 sea lizard which have no representatives in the preceding family. The majority of 

 the iguanoids feed on insects, although some, like the true iguanas and the sea 

 lizards, subsist on a vegetable diet, while one genus is stated to be omnivorous. 

 Only two genera are known to prodtice living young. 



In the forests, groves, and gardens of all the warmer regions of 



America live a number of beautiful lizards commonly known by the 

 Lizards 



name of anolis, which is applied in the Antilles to some members of 



the group. The distinctive features of these lizards are the pyramidal form of the 



