[Illustration: Fig. 94. Humerus, anterior side—⅕ natural size.] [Illustration: Fig. 95. Ulna anterior side—⅕ natural size, after Gaudry.] The lower half of the humerus is present, and characterized by very wide epicondyles, a shallow supratrochlear fossa, a moderately deep anconeal fossa, no foramen, and a wide shallow trochlea. The ulna, according to Gaudry, is a long, heavy, nearly straight bone, with a shallow sigmoid notch, and with a large olecranon process which is not bent backward to any marked degree. The proximal end of the radius has a broad doubly curved articular surface to fit the full width of the humeral trochlea. Its ulna facet is a short broad area just below the margin of the bone, and would indicate little or no rotary motion of the fore arm. Most of the shaft is lacking but what is present indicates a very slender bone. [Illustration: Fig. 96. Upper end of radius, ulnar side—⅕ natural size.] [Illustration: Fig. 97. Left tibia, posterior side—⅕ natural size.] [Illustration: Fig. 98. Astragulus, dorsal aspect—½ natural size, after Ameghino.] [Illustration: 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.