MAMMALIA. 445 



The genus Hipparion closely resembles tlie horses, but was of a much 

 smaller stature. Its remains were found in the south of France. 



We have thus' sketched out at some extent the histor}^ of the great group 

 of pachyderms. The reasons for enumerating so many genera whose 

 existence is confined to a past order of things, will appear when recapitu- 

 lating the succession of the mammalia upon the surface of the earth. AVe 

 have done this also with regard to Edentata, Marsupialia, and Cetacea. 

 These groups are generally less known, and nevertheless of much greater 

 importance, because they are the lowest of the class, and give us the key 

 for its full understandinar. 



Group 4. Ruminarttta. 



We now proceed to the group Buminant/a, through which we may pass 

 more rapidly, as the families of which it is composed are generally better 

 known, most of them having representatives in the fauna of the present 

 day. Several genera are found in North America, some of them of quite 

 imposing stature, and inhabiting the sparsely populated portions of the 

 country. Some belong to the prairies, some to the forests, and others tc 

 the mountains. The characters of the group consist essentially in the 

 singular foculty of masticating their food a second time by bringing it back 

 to the mouth after a first deglutition. This power depends upon the struc- 

 ture of their stomachs, of which they alwaj's have four, the three first being 

 so disposed that the food may enter into either of them, the oesophagus 

 terminating at the point of communication. The first, which is also the 

 largest, is called the paunchy into which vegetable matters, coarsely bruised 

 by a first mastication, are introduced. From the paunch they pass into 

 the second, called the honeycomb or bonnet^ from its peculiar structure, the 

 walls being laminated like a honeycomb. This second stomach is com- 

 paratively very small, globular in form, and seizes the food, moistens, and 

 compresses it into little pellets, which afterwards successively ascend to the 

 mouth to be re-chewed. The animal remains at rest during this opera- 

 tion, which lasts until all the food first taken into the paunch has been 

 submitted to it. The aliment thus re-masticated descends directly into the 

 third stomach called the leaflet, on account of its walls being longitudinally 

 laminated, or resembling the leaves of a book ; and thence to the fourth or 

 the caillette^ the sides of which are wrinkled, and which is the true organ 

 of digestion, analogous to the simple stomach of other animals. In the 

 young, as long as they subsist on the milk of the mother, the caillette is 

 the largest of the four stomachs. The paunch is only developed by the 

 reception of larger and larger quantities of grass, Avhich finally give it an 

 enormous expansion. 



The feet in ruminants are terminated by two toes, each cased in a hoof, 

 which face each other by a flat surface, presenting the appearance of a 

 single hoof which has been cleft ; hence the name of cloven-footed, bifur- 

 cated, &c., applied to these animals. Behind the hoof are sometimes found 



649 



