FOSSIL INSECTIVORA 



29 



concealing themselves. The other Insectivora are inhabitants of 

 the larger tropical islands — Cuba, Madagascar and some East 

 Indian islands — or of South Africa, but have disappeared from 

 the great northern continents, Europe, Asia and North America, 

 where the struggle for existence has been most severe and where 

 all the higher types of mammals have been evolved. 



The Insectivora are a very ancient order of mammals, and in 

 past geological periods they were of more importance than now ; 

 in fact they have been considered by many scientists as represent- 

 ing more nearly than any other living order the primitive central 

 group from which all other mammals have descended. Through 

 the "Age of Mammals" they progressed less than most other 

 orders and several families of them became extinct during that 

 time, while the Moles and Shrews diverged from nearly similar 

 habits to their present peculiarities, and the Hedgehogs, prob- 

 ably, acquired their coat of spines. 



FIG. 22. ICTOPS ACUTIDENS 

 Upper and lower teeth, showing the " tritubercular " molars. Oligocene Epoch, Montana. 



I'wice natural size 



Leptictid^, or Primitive Hedgehogs. Extinct. 



Tritubercular molar teeth. Two incisors in upper dentition. Pre- 

 molars unreduced, the last one molariform. Tibia and fibula fused, 

 ulna and radius separate. Size and proportions like the modem 



