MAMMALIA. 455 



the ground. The body is covered with a coat of long, dense hairs. The 

 tail is extremely short. Musk oxen are found in the greatest numbers 

 within the Arctic circle ; considerable herds are occasionally seen near the 

 coast of Hudson's Bay. The horns of the musk ox are employed for 

 various purposes by the Indians and Esquimaux, especially for making cups 

 and spoons. From the long hairs growing on the neck and chest, the 

 Esquimaux make a kind of wig drooping down to the shoulders, to defend 

 their faces from troublesome insects. 



A fossil species {B. jmUo.su), which seems to be related to the musk ox, 

 has been discovered in the States of Kentucky and Missouri, and we are 

 told also, in Siberit. Whether these remains are perfectly identical is still 

 to be ascertained. 



Group 5. Bodentia. 



The group of Rodentia includes those herbivorous mammals whose jaws 

 are provided in front with long, curved, and cylindrical or neai'ly cylin- 

 drical teeth, the exposed ends of which are bevelled off" on the inner surface, 

 so that they terminate in a sharp, cutting edge. These teeth, two in 

 number in each jaw, and sometimes four in the upper, are separated by a 

 wide empty space from the molars, and thus cannot seize a living prey, nor 

 tear any flesh ; they cannot even cut the food, but serve to file, and by 

 continued action they reduce it into separate molecules ; in a word, they 

 gnaw: hence the term Rodentia or gnaiuers. The molars have a flat 

 crown, whose enamelled eminences are always transverse, and studded 

 Y/ith blunt and but little elevated tubercles. When these eminences are 

 simple lines, and the crown is very flat, the genera are more exclusively 

 frugivorous ; when the eminences are divided into blunt tubercles, they 

 are omnivorous. The condyle of the lower jaw is longitudinal or rounded, 

 and inclosed in the glenoid cavity in such a manner as to permit very little 

 lateral motion to the jaw, which, however, moves freely in the longitudinal 

 direction. This group, one of the most clearly defined, has representatives 

 in till parts of the world, the species of which are very numerous, feeding 

 upon vegetable substances,«and generally of small size, a few exceeding the 

 common rabbit in bulk. The form of the body is generally such that the 

 hinder parts of it exceed those of the front, so that they rather leap than 

 walk. In some of them this disproportion is even as excessive as it is in 

 the kangaroo. 



Fam. 1. Leporid.b. The hare family is less numerous in species than 

 other families of rodents, and offers many exceptions to the general or nor- 

 mal characters of the order. The large size of the openings in the skull, 

 combined with the very imperfect condition of the palate ; the perforations 

 in the nasal process of the superior maxillary bone ; large orbits meeting in 

 the mesial line of the cranium ; the small temporal fossae ; and the increased 

 number of incisors and molar teeth, are among the more striking characters 

 presented by the skull. The extra pair of incisors in the upper jaw is 



659 



