128 FAUNA AMERICANA. 



of fluid, and communicating with the mouth bj 

 large oblong openings, immediately anterior to 

 the molar teeth ; the cavity projecting posteriorly 

 into the orbit, with which it has no communica- 

 tion; anterior to the orbit, above the cavity, is a 

 bony canal, capable of admitting the little finger, 

 somewhat analogous to the infraorbitar foramen 

 observed in the skull of the genus Cavia. 



The structure of the inferior jaw is equally re- 

 markable, and adapted in every respect to the 

 peculiarities of the upper jaw ; the whole of the 

 lower jaw is more slender and narrower than that 

 of the beaver. In order to admit a free passage 

 from the bonv cavities into the mouth, the molar 

 teeth and alveolar processes of the lower jaw are 

 elevated, and the latter are separated from each 

 other anteriorly, so as to leave a capacious open- 

 ing, of an oval form, from the sack into the mouth ; 

 the coronoid process very small, and not project- 

 ing so high as the condyloid ; the latter also small, 

 rounded above and compressed; angles of the 

 lower jaw rounded ; the inferior incisors slender 

 in proportion to those of the beaver, arched on 

 the anterior surface, not approximate, slightly di- 

 vergent at their extremity, somewhat analogous 

 to the incisors of the squirrel ; the crowns of the 

 molars are plain, though they do not appear to 

 have been much worn, and are traversed by three, 

 sometimes four folds of enamel, which, in several 

 of the teeth, have no connexion with the enamel 



