104 THE, DESEADO FORMATION OF PATAGONIA 
into claws, indicating a foot more like that of a dog, in 
which the weight is not carried on the ungual phalanges, but 
rather on the ball of the foot, or bases of the metapodials. 
I should not feel that this group was the ancestral one to 
later groups of toxodonts, but it seems rather to represent 
a line which terminates in the Deseado or very little later, 
not having run up into the Santa Cruz. The line of an- 
cestry for the toxodonts is rather through Leontinidae. 
Rhynchippus pumulis Ameghino 
R. pumulis Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 464. 
We found no speci- 
mens of this species, but 
Ameghino has described 
a complete skull, a fig- 
ure of which is repro- 
duced here. It indicates 
a smaller lighter built 
animal, differing from R. 
equinus not only in small 
size, but also in having a 
relatively longer andnar- 
rower head. ‘The indi- 
vidual is a rather old 
one, so that the pits in 
inc. I and 2 have disap- 
peared, as is also the 
case with the cingulum 
on the ant. int. corners 
of the premolars. Ame- 
os ghino gives the follow- 
Fig. 66. R. pumulis—1/2 natural size; A,topofskull; - . ° 
B, upper dentition, after Ameghino. Ing measurements 1n his 
description. 
Skull, length over all 155 mm. 
Upper dentition, from inc. I to m. 3 80 mm. 
