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. trous- 
sarti, P. lemoinet, P. ephebicum, P. martiale, P. superabile, 
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- 
UPPER LOWER LOWER| LOWER 
pm.4| m.1 | m.2] m.3 | pm.4| m.1| m.2 | m.3 | inc. 1] pm. 4 
|—m. 3] ~m. 3 
P. hatuaberat te 56-56) aa 
P. troussarti 24- 40- 57- 60- 180 
P. lemoinei 34-34 A 
P. ephebicum arora 42-21 | 
P. martiale 30-42 82-83 | | 550 
Drakes 30-43 | wi 
P.dnsuperabille 37-48 | 100-80) 34-23 he? bedi 
Se ee, ae 
P. (Liarthrus) co- 
pei 29-46 
P. (Traspoathe- 
rium) convexi- 
dens 19-27 
[ie | | 
Amherst specimen | 28-26| 43-28] 58-32 70-36 455 200 
| 
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. PP. troussarti, 
as described, is a tenth smaller than P. holmbergi, the only 
structural character differentiating it being the isolation 
