EDENTATA. 525 



The Jerboas (Jerboa). This tribe consists of a small number of 

 Eodents that considerably resemble rats. The tail is long and tufted 

 at the end ; but they are most remarkable from the structure of the 

 posterior extremities, which, in comparison with the anterior, are 

 of immoderate lengtli They are met with from Barbary to the 

 coasts of the Caspian Sea. 



Ordee v. — Toothless Quadrupeds. 

 Edentata.* 



The teeth of quadrupeds are simply mechanical 

 instruments, adapted to obtain and to prepare the 

 food for digestion, and are, consequently, modified in 

 their construction, in accordance with the aliment. 

 To animals which live exclusively upon the foliage 

 of trees, the possession of incisor teeth would be 

 useless, and to others that feed upon such materials 

 as do not require mastication, teeth of any kind 

 would be superfluous. To quadrupeds thus circum- 

 stanced. Cuvier has therefore s^iven the ii'eneral name 

 of Edentata, apparently implying that animals so 

 designated are entirely deprived of teeth, as, indeed, 

 is literally the case with some species, but in others 

 teeth do exist, though of a very peculiar structure. 

 They all, hoicever, agree in having no front or incisor 

 teeth. 



The Order Edentata, therefore, includes all quad- 

 rupeds provided with separated toes, that are without 

 incisor teeth in either the upper or lower jaw. 



Although associated by a character purely negative, 

 the animals thus designated present many points of 

 relationship. Their toes are enveloped in very large 

 and strong nails, upon which they walk with difficulty, 

 and all of them exhibit a slowness, and want of agility, 

 obviously caused by the structure and position of their 

 feet. There are, however, certain intervals in these 

 relations by which the Order may be divided into 

 the following tribes : — 



* Edentata, toothless. 



