CONCLUSIONS. 35 



traversing a short distance above ground, once more 

 descends. As it seldom tunnels at a depth of more than 

 two or three inches below the surface, its course may often 

 be detected by a slight cracking or movement of the 

 surface as the tunnel proceeds. Both in this respect, and 

 in the nature of its food, the ur-quamata therefore exhibits 

 a further analogy with the golden mole. In burrowing, 

 the leathery shield of the head is said to be brought into 

 play as a borer in the soft sand. 



As regards the advantages obtained by those mammals 

 which have taken to a burrowing subterranean existence, 

 it will be manifest that these are twofold. In the first 

 place, the creatures are secure from all foes, except those 

 which, like the weasel and the snake, are able to follow 

 them into their underground labyrinths ; while, secondly, 

 they tap a food- supply (whether animal or vegetable) 

 inaccessible to most other animals. In the case of the 

 mole at least, whose habitations are generally made in 

 comparatively hard ground, the life must be an incessant 

 round of labour ; and to our thinking, at any rate, the 

 existence of all these burrowing creatures must be so dull 

 and monotonous as to leave no question as to whether it 

 is worth living. 



