CHAPTER XII 



THE ORDER IXSECTIVORA 



The Insectivora comprise a number of comparatively small mam- 

 mals, generally of terrestrial, although rarely of arboreal or aquatic 

 habits, and presenting the following common features. They are 

 unguiculate, and have plantigrade or subplantigrade, and generally 

 pentadactylate feet, in which the pollex and hallux are not oppos- 

 able to the other digits. They are diphyodont and heterodont, and 

 the teeth are rooted. The molars are studded with sharp cusps, 

 the crowns of the upper molars being either quadrangular or trian- 

 gular ; there are never less than two incisors in either side of the 

 mandible ; and in many cases the incisors, canines, and anterior 

 premolars are not clearly differentiated from one another (Fig. 280) ; 



the canines being 

 usually weak. 

 Clavicles are pre- 

 sent, except in 

 Potamogalc The 

 body is clothed 

 "with fur or pro- 

 tected by an 

 armature of 

 spines; the 

 testes are in- 

 guinal or placed 

 near the kidneys, 

 and are not received into a scrotum ; the penis is pendent or sus- 

 pended from the wall of the abdomen ; the uterus is two-horned 

 and with or without a distinct corpus uteri ; the placenta is dis- 

 coidal and deciduate ; and the smooth cerebral hemispheres do not 

 extend backwards over the cerebellum (Fig. 281). The projec- 

 tion of the muzzle far beyond the extremity of the lower jaw is a 

 very general feature. The humerus generally has an entepicondylar 



Fig. 2S0.— Right lateral aspect of the anterior portion of the 

 cranium of Erinaceus collaris. Enlarged. (From Dobson, Proc. Zool. 

 Soc. 1SS1, p. 403.)' 



