MAMMALIA. 



The Mammalia constitute the highest and most important class of 

 Vertebrata. They interest us more than the other classes, because 

 they furnish us with those animals which are most useful in 

 supplying us with food, in aiding us in our labours, and in 

 providing us with the raw material required for so many of our 

 manufactures. A land-inhabiting animal of this class is recog- 

 nised at the first glance ; for its external and characteristic marks 

 are numerous. The subordinate marine group of Cetacea, however, 

 supplies rather a marked exception, consequent upon its adapta- 

 tion to exclusively aquatic habits. 



Among the Vertebrata, these animals alone have, as their name 

 imports [manmice), teats, which are situated either on the breast, 

 or on the belly, or on both, and by means of which they suckle 

 their young. The number of teats, in general, corresponds with 

 the number of young of which each litter is composed. 



The majority of the Mammalia are covered with hair. Some, 

 however, have smooth skins : as, for instance, the "Whale and 

 Porpoise ; others, as the Pangolins (Manis), are clad with dermal 

 scales, which are altogether unlike those of Reptiles or Fishes. 



The size of the Mammalia varies extremely : the scale extend- 

 ing from the Whale and the Elephant to the Mouse, and to the 

 most diminutive of Shrews, which are considerably less than half 

 the size of the very smallest of the Mouse genus. 



Although less brilliant than the feathers of Birds and the scales 

 of Fishes, the coats of the Mammalia offer to the eye very agreeable 

 shades of colour. But nothing varies more than the pecidiar 

 nature of this coat. It is enough for us to remember, as a type of 

 these differences, the hair of Fallow Deer, the bristles of the wild 



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