ANCESTRAL MAMMALS 



137 



Tertiaries, and before the chalk. But the recent horse, the 

 recent elephant, the giraffe, the lions, bears, and others, are 

 bigger — some much bigger — than the ancestral forms, to 

 which we can trace them by the wonderfully preserved and 

 wonderfully collected and worked-out fossilised bones dis- 

 covered in the successive layers of the Pliocene, Miocene, 



Fig. 14.— Skeleton of the Indian elepkant. Only four toes are visible, 

 the fifth concealed owing to the view from the side. 



and Eocene strata, leading us as we descend to more 

 primitive, simplified, and smaller ancestors. 



It is easy to understand the initial character of the foot 

 of the early ancestral mammals. It had five toes. By 

 the suppression or atrophy of first the innermost toe, then 

 of the outermost, you find that mammals may first acquire 

 four toes only, and then only three, c^d by repeating the 



