THE TEETH OF INSECTIVORA. 401 



hands with the fingers slightly separated. What the pur- 

 pose served by these comb-like teeth may be remains 

 uncertain : no other animal has similar teeth. Ualeopithe- 

 cus has a well developed milk dentition, the milk teeth 

 being very similar to their successors. 



The teeth of Insectivora are remarkable for the thickness 

 of their enamel, which in the Shrews is to some extent 

 penetrated by the dentinal tubes. The enamel is deeply 

 coloured in some Shrews, the pigment being actually in the 

 substance of the enamel, and not in any distinct layer. 



THE TEETH OP CHIROPTERA. 



The Bats, sharply distinguished from all other mammals 

 Toy the possession of wings, are divided into two groups, 

 respectively insectivorous and frugivorous. 



The insectivorous Bats, by far the most numerous section, 

 are for the most part possessed of small incisors, rather 

 large canines, and premolar and molar teeth which bristle 

 with sharp cusps, and generally present the W-pattern. In 

 fact, in general character, their teeth resemble those of the 

 Insectivora. 



The incisors are sometimes reduced in number, and 

 spaces left between them ; and some, as for example, the 

 Vampire (Desuiodus) have teeth specially modified to accord 

 with their blood-sucking habits. 



This Bat has only one permanent incisor on each side, and 

 this is a large but thin and sharp-edged tooth, with which the 

 wound is made ; the lower incisors are small teeth with feebly 

 notched edges. The canines are large, and the molar 

 series, which is not required in an animal existing upon 

 blood, is stunted. The molar teeth are, however, sharp, 

 though small, and there is no marked distinction into 

 molars and premolars. 



The frugivorous bats (of which the Pteropus, or flying 



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