33 



In another specimen the descending branch of the nerve forming the pre- 

 ceding groove, undermines the ridge, which was continued uninterruptedly 

 across the foramen by which the groove terminates below. 



The great dental canal is continued forwards for about an inch, and then 

 divides : the smaller branch perforates obUquely the anterior part of the base 

 of the coronoid process, and terminates by an elliptical foramen* on the outer 

 side of the jaw, about an inch below the anterior root of that process. The 

 larger division, forming the continuation of the canal, descends obliquely to 

 the under and inner side of the alveolar series, where it bifurcates into a wider 

 and a narrower groove, the latter being at the outer part of the canal. The 

 canal ascends near the anterior part of the alveolar series, and divides into 

 three branch canals, which open upon the outer side of the jaw, where the 

 ramus bends inwards to form the symphysis : the largest of the foramina is the 

 highest and hindmost, and is situated just anterior to the first socket, and about 

 half an inch below the upper margin of the ramus : on one side there were two, 

 on the other three small foramina. 



The size and number of these foramina, which transmitted the vessels and 

 nerves to the lower lip, indicate its great development ; and the corresponding 

 evidences of the strength of the muscles inserted into it combine to prove its 

 importance in the economy of the Mylodon. The power of the retractors must 

 have had an equivalent in that of the elongators, consisting of the fibres of the 

 orbicularis oris ; and the lower lip, thus organized, doubtless aided the tongue 

 in stripping off the fohage and smaller branches of the trees which the general 

 organization of the skeleton of the Mylodon will be shown to be so well calcu- 

 lated to enable it to uproot and prostrate. 



Comparison of the Skull. 



A brief inspection of the skulls of existing quadrupeds suffices to determine 

 those to which the Mylodon makes the closest approach in its cranial organi- 

 zation. 



[n no other genus, save Bradypus, is the cheek-bone so nearly developed to 



* Plate VI. fig. 2. g. 

 E 



