330 PATAGONIAN EXPEDITIONS : PAL/CONTOLOGY. 



The hard palate is nearly plane between the molariform teeth and has 

 a low ridge along the median line of suture ; the backward convergence of 

 the two dental series gives to the palate a characteristically triangular form. 



The mandible (Plate LIX, figs. 2, 2") evidently had a very elongate 

 predental beak, though the anterior portion is so broken that the exact 

 length is not determinable ; this elongation indicates a corresponding 

 length of the rostrum and premaxillaries. From the portion preserved, it 

 appears that this beak had nearly parallel sides, with flared and everted 

 dorsal border, and probably the anterior end was much less pointed than 

 in the Santa Cruz Megalonychida and may well have been as abruptly 

 truncate as in Megatherium ; the symphysis is long and much less steeply 

 inclined than in Hapalops and the chin is much more gradually rounded. 

 The dentary portion of the horizontal ramus is short, of no unusually 

 great depth and with only a moderately convex ventral border; in this 

 respect there is a very striking difference from P. moyani, a difference 

 which may be partly, though not entirely, due to the immature age of the 

 specimen before us. Posteriorly also, the ramus is incomplete, but it is 

 apparent that the coronoid process is relatively short and quite erect and 

 that the angle is decidedly inflected ; the postero-external opening of the 

 dental canal is at the base of the ascending ramus and is very narrow, 

 hardly more than an oval slit. 



In the subjoined table the dimensions of the upper teeth and palate are 

 from the type, those of the lower teeth and the mandible from No. 9,573, 

 a younger and smaller animal. 



MEASUREMENTS. 



Upper dentition, length A-l. 046 Lower dentition, length ^_^ 029 



1, length (*'. e., antero-posterior diame- T , length 008 



ter) 0085 " width 006 



" width (i. e., transverse diameter) 016 2 , length 008 



2-, length 0085 " width 0125 



" width 0165 $, length 0075 



, length 0085 " width on 



" width 013 ? , length 0085 



i, length 006 " width on 



" width 0105 Mandible, depth at ^ 035 



Palate, width at ^- 020 " thickness at ^ 0185 



" " & 013 estimated length of beak. . . .050 



Lower dentition, length 043 



