148 



THE DESEADO FORMATION OF PATAGONIA 



trochlea, and with the navicular facet directed obliquely 

 forward, making an angle of 127 with the plane of the 

 trochlea, which, as he says, would indicate a semidigiti- 

 grade position of the pes. 



The following species are distinguished by Ameghino 

 as coming from the Deseado beds: P. holmbergi, P. Irons- 

 sarti, P. lemoinei, P. ephebicum, P. martiale, P. super abile, 

 P. insuperabile. The various species are known from 

 the same parts in but a few cases. Their relative sizes 

 are indicated from the following compilation of the measure- 

 ments given by Ameghino: 



P. holmbergi is the type species, and of considerable size, 

 and to it I have assigned my material. In such a large 

 animal, variations in size are to be expected. P. troussarti, 

 as described, is a tenth smaller than P. holmbergi, the only 

 structural character differentiating it being the isolation 



