448 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 52 



the condyle nearly so, while only a small portion of the angle is lack- 

 ing. The jaw contains five alveoli, in two of which — the penultimate 

 one and the next but one anterior to it — the teeth are still in posi- 

 tion. The fragment of the left ramus is very imperfect, only a small 

 portion of the inferior border being complete and no alveoli present. 

 Of the separate teeth, one appears to be a right lower molar, and 

 probably belongs between the two which are in place in the mandi- 

 ble ; three others are single-rooted teeth from the anterior end of the 

 mandible on the right side, and the remaining four appear to belong 

 to the upper jaw. Of the latter, two are single-rooted, one has indi- 

 cations of three roots, and is probably a premolar, and the last is a 

 short tooth with two fused roots — possibly a last molar. 



Mandible 



The dimensions of the jaw, compared with those of the same part 

 in the type specimen, as indicated by Doctor Lydekker's figures, are 

 as follows : 



Dimensions ofhvo mandihles of Prosqualodon ausiralis 



15441- 

 San Julian, 

 Patagonia. 



Type of 

 P. a ust rail's. 



Total length of the fragment containing 5 posterior 

 alveoli 



Distance from condyle to posterior alveolus 



Height of jaw at coronoid process 



Distance from highest part of coronoid process to 

 inferior margin of condyle 



Depth of javp at posterior alveolus , 



Length of last four alveoli taken together , 



Length of penultimate tooth at alveolus 



Breadth of penultimate tooth at alveolus 



Least distance externally betvv^een crown and alve- 

 olus of penultimate tooth 



Length of crown at base 



Thickness of crown at base 



mm. 



445 

 290 

 217^ 



204 



95 

 124 



30 

 18 



17 

 21 



14 



420 (?) 

 297 



225 (?) 

 78^ 

 120 



9 

 21 



1 Angle defective. 



'■ Border defective below (?). 



The correspondence in size and proportions between the two speci- 

 mens is evidently very close, the chief difference, apparently, being 

 that the teeth protrude more from the alveoli in the San Julian jaw. 



In the latter specimen the apex of the coronoid process is obtuse 

 and is directed backward. The superior margin of the jaw near the 

 apex of this process is 15 mm. broad and is inclined outward. An- 

 teriorly it becomes more everted, narrower, and more rounded, but 

 broadens out again as it approaches the posterior alveolus, and is 



