144 THE STORY OP THE EARTH AND MAN. 



Friday. Within the thirty years since the discovery 

 of the first slab of footprints, the knowledge of coal 

 formation reptiles has grown apace. I can scarcely at 

 present sum up exactly the number of species, but 

 may estimate it at thirty-five at least. I must, how- 

 ever, here crave pardon of some of my friends for the 

 use of the word reptile. In my younger days frogs 

 and toads and newts used to be reptiles ; now we are 

 told that they are more like fishes, and ought to be 

 called Batrachians or Amphibians, whereas reptiles are 

 a higher type, more akin to birds than to these lower 

 and more grovelling creatures. The truth is, that the 

 old class Keptilia bridges over the space between the 

 fishes and the birds, and it is in some degree a matter 

 of taste whether we make a strong line at the two 

 ends of it alone, or add another line in the middle. I 

 object to the latter course, however, in the period of 

 the world's history of which I am now writing, since I 

 am sure that ther.e were animals in those days which 

 were batrachians in some points and true reptiles in 

 others ; while there are some of them in regard to 

 which it is quite uncertain whether they are nearer to 

 the one group or the other. Although, therefore, 

 naturalists, with the added light and penetration 

 which they obtain by striding on to the Mesozoic 

 and Modern periods, may despise my old-fashioned 

 grovellers among the mire of the coal-swamps, I 

 shall, for convenience, persist in calling them reptiles 

 in a general way, and shall bring out whatever claims 

 I can to justify this title for some of them at least. 



