56 



BRITISH MAMMALS 



was probably the case) to the Insectlvores. In fact, if the hedge- 

 hog could have been traced back to a period as remote as the 

 end of the Secondary Epoch it might not have seemed unreason- 

 able to consider it as the first departure from the generalised 

 Eutheria in the direction of the Rodents. The second and 



third incisor teeth in 

 the upper jaw of the 

 hedgehog are becoming 

 a negligible quantity, 

 and in some of the 

 Asiatic species the 

 second incisor almost 

 disappears. The upper 

 and lower canine teeth 

 are not markedly 

 prominent. In some 

 of the Asiatic species 

 the upper canines and 

 the third incisors are 

 inserted by a double 

 instead of a single root. 

 But in the British 

 hedgehog {Erinaceus 

 europaus) these teeth 

 have only a single 

 root, though in the 

 canines there is a 

 groove that suggests 

 that the root was 

 originally double- 

 fanged. The third upper premolar in the series (it should 

 properly be styled the fourth, an intermediate one having 

 dropped out) is also a notable tooth, with a trenchant blade, 

 resembling the great carnassial fourth premolar so characteristic 

 of the true Carnivora. 



The hedgehog has five pairs of teats, and the number of 



4th incisor. 



4th lower premolar. 



3rd premolar. 



ist incisor. 



Skulls of Insectivores, to show Teeth. 



A. Hedgehog and B. Mole (nat. size) ; C. Lesser Shrew 



(2I times nat. size). 



