66 THE DESEADO FORMATION OF PATAGONIA 



Visser, fifteen times; and in one case the major part of a 

 skeleton was found, consisting of the skull and jaws, verte- 

 brae of each type, ribs, most of the fore limb, the pelvis 

 and a hind limb. 



The animal as a whole is smaller than P. triangulidcus 

 by about 12%, and is of lighter build. The skull is rela- 



ffl tively light and narrow, 

 especially in the rear, 

 where the swollen hollow 

 capsules of the squamo- 

 sum bones come within 

 ten millimeters of meet- 



Fig. 30. Left upper dentition; left lower dentition ing medianly, whereas, 

 natural size. 



in other species, they are 



twice as far apart. These hollow capsules are in this species 

 the most marked, and in this genus even more developed 

 than in Pachyrukhos. The lachrymal bone is larger ex- 

 ternally than usual, the lachrymal cluct opening about 

 four millimeters in front of the margin of the orbit, and 

 continuing to the margin by an open groove. In P. 

 triangulidens, the duct is inside the orbit. The heavy 

 maxilla makes a strong process for the zygomatic arch, 

 extending fully half way back along this arch. The short, 

 but fairly stout jugale has but a short contact with the 

 maxilla. 



In the dentition, the premolar and 'molar teeth are 

 covered with a thin film of cement, which is thicker on the 

 outside of the upper teeth and on the inner side of the 

 lower teeth. On the opposite sides of these teeth this 

 film is so thin that it is often in part 

 worn off. 



Specimen 3083 preserves three of 

 the deciduous premolars. Pm. 2 is v 

 simple and could readily be taken for the corresponding 

 permanent premolar, except that it is, as are all the decidu- 

 ous premolars, rooted. Deciduous premolars 3 and 4, on 



