148 EVOLUTION IN THE PAST 



Carnivores were thus present in great variety ; and the 

 environment of the gentler animals was alive with dangers. 

 Some part, however, of carnivore ferocity found outlets in 

 its own ranks, for the animals no doubt preyed to a certain 

 extent on one another. Their mode of life, moreover, was 

 conducive to internal dissensions ; and wild beasts do not 

 settle their differences by arbitration. 

 RODENTS Rodents — which may have fallen frequent victims to 

 incipient weasels and otters— had now spread far and wide. 

 Many changes had been wrought in their ranks, and the 

 highly intermixed condition of development, which had 

 characterised their Eocene forerunners, was now a thing of 

 the past. Unlike their predecessors — and hke modern 

 rodents — they were without canine teeth ; and compensa- 

 tion had come by the development of very powerful incisors, 

 thoroughly adapted to gnawing purposes. The animals, 

 moreover, were branching out in various directions. Some of 

 them were practically indistinguishable from living squirrels 

 {Sciurus). Other forms, though closely linked with squirrels, 

 seem to have been developing in the direction of cavies and 

 porcupines (Sciuroides, Ischyromys). In yet other forms a 

 beaver proclivity was decidedly marked ^Steneo fiber). And 

 rats {Eumys, Cricetodon), dormice (Myoxus), hares and rabbits 

 (Palceolagus, Titanomys), all more or less of modem aspect, 

 were by this time in existence. 

 INSECTIVORES Insectivores, i.e. mammals with their teeth specially 

 adapted to an insect diet, were in evidence in Eocene times 

 in certain shrew-like forms, that had been foreshadowed as 

 far back as the Jurassic Period. From insectivorous creatures,, 

 more or less of this humble description, some higher forms of 

 life had no doubt arisen ; but developments continued more 

 or less on the old lines. It is clear from the condition of the 

 Ohgocene insectivores that consequent, it may be supposed, 

 on some enforced changes of habit, important modifications 

 had taken place. Some of the animals had taken to hving 

 underground, and were in fact moles, though their Umbs 

 were not so weU adapted for burrowing as in the case of 

 living forms (Protalpa). Others seem to have been in a 

 hesitating condition between moles and hedgehogs (Tetracus) - 



