TNSECTIVORA. 49 



Ord. TNSECTIVORA. 



Incisor teeth various in number and almost always different in the 

 two jaws ; no distinct canines in most ; molars with acuminated tuber- 

 cles. Feet usually pentadactylous, plantigrade. 



The insectivorous mammals are mostly of small size, with short limbs, 

 and some of them superficially much resemble the Rodents. Many live 

 under ground, and most are nocturnal. They feed chiefly on insects. 

 Some are torpid in winter in cold countries. They are timid and un- 

 obtrusive in their habits, and rather slow in their motions. The tail is 

 variously developed. In running they place the entire sole of the foot 

 upon the ground. 



The skull is of slight make and elongated form, the bones of the foce 

 and jaws being much produced, and the latter are weak. The distinct 

 division of the teeth into sets is not apparent here, and it is some- 

 times difficult to say to which set particular teeth belong. Thei-e are 

 usually eight teeth in front of each jaw, of which the outermost ai'e re- 

 garded by some as the canines, though often smaller than the others, no 

 placental mammal having more than six incisors in each jaw. The orbit 

 and temporal fossa are confounded in one cavity, except in Tupaia. The 

 molar teeth are studded with sharp cusps or tubercles, for the purpose 

 of breaking down the hard elytra of beetles, on which they chiefly sub- 

 sist. All have clavicles, and the number of ribs is large. The deciduous 

 teeth of the moles and shi-ews are developed and disappear before birth. 

 The stomach is perfectly simple ; and, except Tupaia, they have no 

 Cfecum. The brain and organs of sense closely resemble those of the 

 Rodents. The mammae are ventral and generally numerous. The testes 

 pass periodically from the abdomen into a temporary scrotum. 



Insectivorous mammals are nearly confined to the old continent, none 

 being found in South America, if we except the curious Solenodon para- 

 doxus of St. Domingo ; and only a few moles in North America. They 

 are represented on tliat continent chiefly by small species of Didel2)hys or 

 Opossum, a mai'supial animal. There are likewise none in Australia, 

 bat several marsupials resemble them so closely that, were it not for 

 their special anatomical structure, they would undoubtedly be classed 

 with them. 



Blainville looks on the Insectivora as being intermediate between 

 Bats and the Edentata. Cuvier j>laces them next the Bats, as do most 



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