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. triangulidens 
by about 12%, and is of lighter build. The skull is rela- 
LD tively light and narrow, 
especially in the rear, 
where the swollen hollow 
capsules of the squamo- 
; ; | sum bones come within 
yy ten millimeters of meet- 
Fig. 30. Left upper dentition; left lower dentition— ing medianly, whereas, 
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 duct 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 
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 
Fig. 31. Left upper denti- 
tion No. 3083, showing decid- 
uous premolars. 
