R. pumulis Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 464.

Fig. 66. R. pumulis—½ natural size;
A, top of skull; B, upper dentition,
after Ameghino.

We found no specimens of this species, but Ameghino has described a complete skull, a figure of which is reproduced 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 narrower head. The individual is a rather old one, so that the pits in inc. 1 and 2 have disappeared, as is also the case with the cingulum on the ant. int. corners of the premolars. Ameghino gives the following measurements in his description.

Skull, length over all155 mm.
Upper dentition, from inc. 1 to m. 3  80 mm.

Rhynchippus medianus Ameghino

R. medianus Amegh., 1901, Bol. Acad. Nac. Cienc. Cordoba, t. 16, p. 375.

This third species is intermediate in size between the two foregoing. No figure is given, but the following measurements give the size:

Upper molar 2, length, 17 mm., width11 mm.
Length of lower molars 1 to 340 mm.
Height of mandible under m. 224 mm.