OF THE CLASS MAMMALIA. 275 



species frequents the shores of the Polar seas. The former 

 live in caverns or burrows dug by themselves, their strong 

 claws enabling them to do this. In extremely cold weather 

 they pass the time in a profound lethargy. 



415. The order called amphibia is formed of two genera, 

 the seal and walrus. In these animals, also carnivorous, the 

 feet are not adapted for walking, but for swimming: they pass 

 the greater part of their lives in the water. 



[If my memory serve, my esteemed friend, De Blainville, 

 placed in a distinct class certain animals truly amphibious, as the 

 siren, proteus, axolotl, &c. Seals, otters, &c., are not strictly 

 amphibious. R. K.I 



Fig. 237. The Seal. 



416. The order of cheiroptera is closely united to the 

 quadrumana, but have the pectoral extremities organized for 

 flight by means of a large fold of integument, extending from 

 the flank and tail to the extremity of the fingers (Fig. 238, 239). 

 The brain also is much less developed than in the preceding 

 groups. The dental system is still composed of incisives, 

 canine and molar teeth. Of the class some are frugivorous, 

 with molars resembling the quadrumana ; others insectivorous, 

 and in these the teeth are formed as in the following class. 

 The bats are the principal representatives of the group. 



417. The insectivora do not differ from the other ungui- 

 culated mammals, expecting in this, that the molar teeth are 

 evidently constructed for the crushing of insects, on which 

 they live. They are in fact rough, with conical points (Fig. 

 22), which adapts them for this purpose. Their brain rather 

 resembles that of the cheiroptera in having no convolutions, 

 than what we find in the bimana, quadrumana, carnivora, and 

 amphibia. The greater number make use of burrows, and 

 hybernate. We cite, as examples of the group, the mole 

 T 2 



