32 THE DESEADO FORMATION OF PATAGONIA 
the astragulus developed in two planes so that it appears 
as a deep notch. In the case of the new genus the toes 
are almost equal in size, giving us a stage in the develop- 
ment of this three-toed form which is much more primitive 
than the well-known Santa Cruz genus. 
Notodiaphorus crassus sp. nov. 
The specimen selected as type is number 3287 of the 
Amherst Collection, consisting of a complete pes, tarsus, 
lower end of the tibia, and the femur, 
from the Deseado on the Chico del 
Chubut River, west of Puerto Visser. 
Beside this, there are seven other speci- 
mens, mostly parts of hind limbs, but 
others having also the lower end of the 
humerus, the radius and ulna, metacar- 
pals, and some phalanges. The species 
is distinguished by its large size, being 
larger than the species of the Santa 
y 2 Cruz, and, at the same time, the three 
Fig. 6. Distal end of right toes of both the pes and the manus are 
a Billa subequal in size. 
The distal end of the humerus associated indirectly 
with this species is moderately heavy, with fair-sized epi- 
condyles, and no entepicondylar foramen. The supratro- 
chlear fossa is moderately deep, the anconeal very deep, 
the two being connected by a small foramen, as is typical 
for this family. The trochlearis, slightly oblique to the. 
long axis of the shaft, has a simple pulley-like articular 
end without ridges of division, the internal border being 
narrower and higher than the external. 
MEASUREMENTS, SPECIMEN 3201 
Humerus, greatest diameter of the distal end 58 mm. 
width of trochlea on the anterior side 37 mm. 
width of trochlea on the posterior side 28 mm. 
