| Measurements | |||
|---|---|---|---|
| Upper dentition, | length inc. 1 to m. 3 (@ Ameghino) | 71 mm. | |
| premolar 1, | length 7 mm., | width 4 mm. | |
| premolar 3, | length 7 mm., | width 6 mm. | |
| premolar 4, | length 8 mm., | width 6 mm. | |
| molar 1, | length 8 mm., | width 6½ mm. | |
Argyrohyrax proavunculus Ameghino
A. proavunculus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 436.
The species is simply said to be much smaller than the preceding, which, by the measurements, would figure out about 27%. The measurements given are pm. 1 to m. 3, 33 mm.
Argyrohyrax acuticostatus Ameghino
A. acuticostatus Amegh. 1901, Bol. Acad. Nac. Cienc. Cordoba, t. 16, p. 361.
This species is described as differing from A. proavus in being somewhat smaller, but I find it about the same size. The specific character is in the teeth being more compressed, and in the anterior vertical margin of the upper molars being developed in the form of a very salient crest.
Isoproedrium Ameghino
Proedrium Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 623.
Proedrium Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 431.
Isoproedrium, Amegh., 1903, Anal. Soc. Cient. Argen., t. 56, p. 18.
This genus is based on a toothless mandibular symphysis of large size, on which the second incisor is indicated as larger than the first. We found one lower jaw, which, though imperfect, confirms the above as a genus and adds the following for generic characters; premolars with a shallow inflexion on the inner and outer sides, the molars with a shallow inner, and a narrow deep outer inflexion, heavy layer of cement on the premolars and molars, enamel reduced on the anterior internal, and the posterior internal corners of at least the premolars.