IO4 



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 and nar- 

 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- 

 ghino gives the follow- 

 ing measurements in his 

 description. 



Skull, length over all 155 mm. 



Upper dentition, from inc. I to m. 3 80 mm. 



Fig. 66. R. pumulis 1/2 natural size; A, top of skull 

 B, upper dentition, after Ameghino. 



