THE CARBONIFEROUS AGE. 147 



The belly was strengthened by bony plates and closely 

 imbricated scales, to resist, perhaps, the attacks of 

 fishes from beneath, and to enable them without 

 injury to drag their heavy bodies over trunks of trees 

 and brushwood, whether in the water or on the land. 

 Their general aspect and mode of life were therefore 

 by no means unlike those of modern alligators ; and 

 in the vast swamps of the coal measures, full of ponds 

 and sluggish streams swarming with fish, such crea- 

 tures must have found a most suitable habitat, and 

 probably existed in great numbers, basking on the 

 muddy banks, surging through the waters, and filling 

 the air with their bellowings. The most curious point 

 about these creatures is, that while rigid anatomy 

 regards them as allied in structure more to frogs and 

 toads and newts than to true lizards, it is obvious to 

 common sense that they were practically crocodiles; 

 and even anatomy must admit that their great ribs 

 and breastplates, and powerful teeth and limbs, in- 

 dicate a respiration, circulation, and general vitality, 

 quite as high as those of the proper reptiles. Hence, 

 it happens that very different views are stated as to 

 their affinities ; questions into which we need not now 

 enter, satisfied with the knowledge of the general ap- 

 pearance and mode of life of these harbingers of the 

 reptilian life of the succeeding geological periods. 



In the other direction, we find several animals of 

 small size but better developed limbs, leading to a 

 group of graceful little creatures, quite as perplexing 

 with regard to affinities as those first mentioned, but 



