Fig. 144. Right mandible—½ natural size,
after Ameghino.
| Measurements | ||
|---|---|---|
| Lower dentition, | canine, antero-posterior diameter | 30 mm. |
| Lower dentition, | canine, transverse diameter | 20 mm. |
| Lower dentition, | premolar 1 to molar 3 | 145 mm. |
| Lower dentition, | height of mandible under pm. 4 | 60 mm. |
Proborhyaena antiqua Ameghino
- ? Borhyaena antiqua Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 655.
- Proborhyaena antiqua Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 502.
This species is known only by a single canine 100 mm. long, of which but 15 mm. belongs to the crown. Its antero-posterior diameter is 14 mm., the transverse 12 mm. It seems to me very doubtful whether this is a valid species.
Caenolestidae
This family, based on the living genus Caenolestes, is represented in Tertiary times in Patagonia by three subdivisions, Palaeothentinae, Garzoninae, and Abderitinae. While diprotodonts, as far as known, the family is in strong contrast to the Australian diprotodonts in that there is no sign of syndactylism in the pes. The American forms are characterized by four subequal upper incisors, a normal canine, the first three premolars vestigal, while the fourth is either normal or enlarged into a sectorial tooth. The three molars are progressively smaller from the front back. The first lower incisor is greatly enlarged and procumbrent, the remaining incisors, the canine, and the anterior premolars being vestigal though usually present. Premolar 4 is enlarged and sectorial in most genera, and the molars as in the upper jaw progressively smaller.
For the practical purposes of this paper the subfamilies are distinguished as follows: