CHAPTER XXXIV. 



RODENTS, concluded. 

 THE HARE-LIKE RODENTS. 

 Families LAGOMYID^E and 



THE whole of the Rodents described in the preceding chapters are characterised 

 by having but a single pair of incisor teeth in the upper (as in the lower) jaw ; 

 and they are hence collectively spoken of as the single-toothed Rodents, or Rodentia 

 Simplicidentata. On the other hand, the hares and rabbits, together with their 

 cousins the picas, have a second smaller pair of incisors placed behind the large 

 front pair in the upper jaw, as shown in the accompanying cut. These Rodents 

 are accordingly regarded as con- 

 stituting a group of equal value 

 with the one containing all the 

 other families, for which the term 

 double-toothed Rodents, or Rodentia 

 Duplicidenta, is adopted. In the 

 young of this group three pairs of 

 incisors are present in the upper 

 jaw, but the hindmost pair soon 

 disappear, and are not succeeded by 

 permanent teeth. In addition to 

 these extra incisor teeth, these 



Rodents are characterised by the enamel extending all round the large incisors, 

 instead of being confined to their front surfaces. In the skull the palate is 

 distinguished by the shortness of its bony portion, in which there are very large 

 vacuities in front ; while its hinder border is situated between, instead of behind, 

 the molar teeth. In all cases the latter teeth have tall crowns without roots, and 

 are divided into parallel transverse plates surrounded by enamel. In the hind- 

 limb the bones of the lower leg (tibia and fibula) are united together. The upper 

 lip is invariably cleft. 



These Rodents, which are divided into two families, are all strictly terrestrial 

 in their habits, and have a wide geographical distribution, although more abundant 

 in the Northern than in the Southern Hemisphere. 



SKELETON AND TEETH OF HARE. 



