2364 REPTILES 



6. LIZARDS and SNAKES Squamata. 

 *y. FISH LIZARDS Ichthyosauria. 



8. TUATERAS or BEAKED LIZARDS Rhynchocephalia. 

 *g. MAMMAL-LIKE REPTILES Anomodontia. 



Of these groups, by far the most numerously represented at the present day is 

 the one containing the lizards and snakes, all of which are highly specialized forms, 

 occupying a position in the class analogous to that held by the perching birds in 

 the preceding class, the majority being comparatively-small or medium-sized forms. 

 Next in point of numbers come the tortoises and turtles, all of which are protected 

 by the presence of a bony carapace, and some of which attain very large dimen- 

 sions The third numerical position in the fauna of the present day is held by the 

 crocodiles, of which there are some twenty- four species, all of relatively- large size, 

 and all more or less aquatic in their habits. The fourth existing order is now rep- 

 resented only by the lizard-like New Zealand tuateras, of which there is probably 

 but a single species, although in past times there were a host of allied forms. Of 

 the five extinct orders the whole or nearly the whole, of their representatives ceased 

 to exist with the close of the Secondary period, that is to say, soon after the depo- 

 sition of the chalk, and previous to that of the overlying London clay. During 

 that long period, or " world of reptiles," the class attained a development which it 

 never equaled before or since. The Dinosaurs, which were by far the largest of all 

 land animals, then filled the place now occupied by Mammals; the flying dragons 

 played the r61e of the bats and birds of the present day; while the marine Plesio- 

 saurs and fish lizards did duty for whales and porpoises. Of the mammal-like Rep- 

 tiles, it will suffice to speak in the sequel. With regard to the past distribution of 

 the four existing orders, it may be mentioned that the lizards and snakes, with the 

 exception of two extinct suborders, are practically unknown before the commence- 

 ment of the Tertiary period that is to say, until after the deposition of the Chalk; 

 hence they may be regarded as essentially the Reptiles of the present day, when 

 they attain their maximum development. The tortoises and turtles, although a 

 much more ancient group, having existed throughout the Secondary period, are, 

 however, still at or about their zenith. The case is, however, very different with 

 the crocodiles, which were represented during the Secondary period by a host of 

 forms quite unlike those of the present day, and probably more numerous in species 

 than their existing representatives. Many of the extinct crocodiles also exceeded 

 any of the living forms in point of size. Still more markedly is this diminution 

 noticeable in the case of the tuateras, in which a solitary survivor represents a once 

 abundant group. 



Owing to the exigencies of space, our remarks on the present distribution of 

 the class must necessarily be brief. In the first place, it may be observed that 

 while no exisiting Reptiles are denizens of the air, only the turtles and sea snakes 

 are habitual inhabitants of the ocean. Of the terrestrial and fresh-water forms, it 

 has been found that the distribution does not coincide very closely withat that of 

 Mammals and Birds, so that the zoological regions into which the globe has been 

 mapped out from the geographical distribution of the latter scarcely hold good for 



