6 REPTILES 



our conception of the relative importance of the class Reptilia in 

 the animal kingdom ; showing, as it does, that in place of com- 

 paratively few, the class really contains a very large number of 

 widely different structural types. A mere inspection of the lists 

 does not, however, by any means reveal all that is implied as 

 regards the differences between recent and extinct reptiles. For 

 example, with the exception of crocodiles and their kin, giant 

 land-tortoises and turtles, and pythons and anacondas, no modern 

 reptiles can be regarded as really large animals, while the great 

 majority of the class are comparatively small creatures. Even 

 in the case of crocodiles and alligators a length of twenty-five 

 feet is but very rarely, if ever, attained ; while thirty feet is an 

 unusually large size for a python or an anaconda, although it is 

 possible that individuals considerably exceeding these dimensions 

 may now and then be met with. Again, as already stated, 

 practically all the recent members of the class are characterised 

 by the relative shortness of their limbs (when these appendages 

 are present at all), and the consequent approximation of the 

 lower surface of the body to the ground. 



Contrast the comparatively small dimensions and creeping 

 gait of the majority of living types of reptiles with the huge bulk 

 and the elevated or even upright position of the body in many of 

 their extinct relatives of the Jurassic and Cretaceous epochs. 

 The American dinosaur Diplodocus, for instance, had an ap- 

 proximate length of between sixty and seventy feet, and pro- 

 bably stood not far short of twelve or thirteen feet in height ; 

 while its relative the iguanodon, when in its habitual upright 

 position, towered to something like twenty feet. The body, 

 too, of Diplodocus and its four-footed relatives was raised so 

 much above the ground that a man somewhat below the 

 ordinary stature could have probably walked under its belly 

 without much stooping. 1 During the same epochs the seas 

 were inhabited by gigantic ichthyosaurs and plesiosaurs, which 

 filled the place in nature now occupied by whales, and some 

 of the larger and more typical representatives of which attained 

 dimensions of between thirty and forty feet, or possibly even 

 more. Larger still were those big-headed members of the 

 plesiosaurian group known as pliosaurs, in which the length of 



1 Some naturalists are of opinion that Diplodocus had a pose like that of a 

 crocodile, with the belly close to the ground. 



