Fig. 99.
A, Ungual phalanx, No. 3;
B, Ungual phalanx, No. 5
—½ natural size.
The tibia is also a rather light bone of moderate length, and is strongly curved inward, the inner margin being especially concave. On the wide proximal end, the inner condyle is concave, the outer convex, the two being separated by a prominent bifid spine. The shaft is slender, with a deep groove down the anterior face especially at the upper end, while on the posterior face, there is a large interosseus crest, which starts just below and external to the spine, and extends in a sigmoid curve three-fourths of the length of the shaft, ending on the internal border. Distally the tibia is flattened antero-posteriorly, and the internal margin extends as a wide process down to the level of the navicular face of the astragulus. The articular facet for the astragulus is a rectangular depression, being about half as wide in the antero-posterior direction as in the transverse. This facet is only slightly concave and the inner and outer portions are not separated by an inter-trochlear ridge. The fibula has not been found, but the tibia shows no indication of its having been fused to it.
Ameghino has figured the astragulus as very low, with the trochlea flattened, the internal condyle being wider and flatter, while the external condyle is narrower and somewhat raised. The trochlea is peculiar in that its proximal margin is deeply notched by a depression in which there is a large perforation. The neck is prolonged and carries a large convex head articulating with the navicular only. The measurements given are, length 116 mm., width 75 mm.
Gaudry figures a calcaneum, showing a long narrow tuber, and the facet for the fibula as a wide shelf which projects strongly on the external side. The size as given by Ameghino is 240 mm. long, by 120 mm. wide.
I have two associated ungual phalanges, one of which corresponds to that figured by Ameghino as the third. It is high, laterally compressed, has a very rugose surface on either side, and a deep cleft in the end. This is 68 mm. long. The second ungual is very asymetrical, also laterally compressed, and with the point curved inward. I take it to be the fifth. The tibia, the tarsus, and the phalanges strongly suggest that this animal walked on the side of its foot.
Asmodeus scotti Ameghino
A. scotti Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 643. A. scotti Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 477.
This species is not represented in our collection, but I reproduce Ameghino’s figure of the type, and of the milk dentition. Unfortunately his type figure is from the side and does not give all the desired information.
