l8o THE DESEADO FORMATION OF PATAGONIA 



The lower jaws were associated with the above skull, 

 and are complete to behind the third molars on both sides. 

 They are very short and heavy, especially in the anterior 

 portion, the symphysis extending back to opposite the 

 middle of the second molar. The height under molar 3 

 is 150 mm. See frontispiece. 



From the upper dentition, I give the measurements 

 of my two chief specimens, together with those given by 

 Ameghino for his type of P. sorondoi, and the figures 

 given by Gaudry; from which may be seen the amount of 

 variation which individuals may show. 



UPPER DENTITION SPECIMEN SPECIMEN AMBGHINO'S GAUDRY'S 



No. 3207 No. 3250 TYPE SPECIMEN 



Total length, inc. I to m. 3 530 mm. 



Inc. I, length above alveolus 133 mm. 



Inc. i, antero-postcrior diam. 49 mm. 



Inc. I, transverse diam. 37 mm. 42 mm. 



Inc. 2, length above alveolus 174 mm. 



Inc. 2, antero-posterior diam. 59 mm. 77 mm. 65 mm. 



Inc. 2, transverse diam. 40 mm. 52 mm. 41 mm. 



Premolar 2, length 45 mm. 52 mm. 48 mm. 40 mm. 



Premolar 2, width 36 mm. 40 mm. 30 mm. 29 mm. 



Premolar 3, length 46 mm. 49 mm. 48 mm. 40 mm. 



Premolar 3, width 57 mm. 57 mm. 46 mm. 48 mm. 



Premolar 4, length 47 mm. 51 mm. 46 mm. 43 mm. 



Premolar 4, width 63 mm. 64 mm. 58 mm. 57 mm. 



Molar I, length 55 mm. 55 mm. 57 mm. 55 mm. 



Molar I, width 68 mm. 69 mm. 61 mm. 61 mm. 



Molar 2, length 68 mm. 77 mm. 70 mm. 57 mm. 



Molar 2, width 85 mm. 93 mm. 75 mm. 68 mm. 



Molar 3, length 75 mm. 68 mm. 83 mm. 64 mm. 



Molar 3, width 86 mm. 87 mm. 82 mm. 88 mm. 



For the lower dentition, I give the figures which Ame- 

 ghino records for his P. sorondoi, those given by Gaudry 

 for his P. romeri, and the measurements of specimen 

 No. 3207. The tushes in the lower jaw I would designate 

 as incisors 2 ; because when the jaws are closed these diverge 

 and their tips bite against the tips of the upper incisors 2. 

 The first incisor seems to have been gradually lost and 



