108 LIZARDS. 



as the shoulder-girdle persist. In form the tongue is flattened, and, as already- 

 said, cannot be withdrawn into a basal sheath, although such a sheath may be 

 present. In most of the members of the suborder the upper surface of the body is 

 clothed with the overlapping scales characteristic of the order in general, these 

 scales being in some cases underlain by bony plates ; but in most geckos the upper 

 scales are granular, although sometimes juxtaposed. 

 Numbers and Numerically, lizards are by far the most abundant of all reptiles 



Distribution. a fc i^q present day, the total number of species not falling far, if at 

 all, short of one thousand seven hundred, which are arranged under twenty distinct 

 families. In this abundance at the present day, coupled with the specialised 

 features of the greater part of their organisation, lizards may be regarded 

 as occupying a very similar position in the reptilian class to that held by the 

 perching birds in the preceding class. With the exception of the polar and sub- 

 polar zones, lizards are distributed over the whole globe, ranging in some districts 

 from the level of the sea to the limits of eternal snow, and found alike in fruitful 



SKELETON OF LIZARD. 



and barren districts, in the neighbourhood of water, and in the most arid deserts. 

 Whereas, however, in the colder regions they are poor in species and small in size, 

 it is in the tropics and subtropical regions that they attain their maximum 

 development, as regards numbers, bodily size, richness of coloration, and peculiarity 

 of form. 



As regards their distribution over the surface of the globe, lizards present a 

 most remarkable difference from what obtains among Amphibians (frogs, newts, 

 etc.), and, to a less degree, among tortoises. For instance, whereas Amphibians, 

 and to some extent tortoises, have their distributional areas defined equatorially, 

 such lines of division, in the case of the present group, must be drawn meridionally. 

 Thus, in the case of Amphibians, one great distributional province includes Europe, 

 Asia, and North America, and the second embraces the regions lying south of the 

 Equator ; whereas in the case of lizards one area marked by peculiar forms will 

 include the Old World and Australia, and the other will comprise the whole of 

 America. As has already been noticed, the distribution of tortoises approximates 

 to the former type, all the side-necked group being confined to the Southern 

 Hemisphere. Again, we find that whereas Tropical Africa is closely related to 



