. The American diceratheres. Rhinoceroses, Fossil; Paleontology. 444 MEMOIRS OF THE CARNEGIE MUSEUM. the large entepicondyle and prominent supinator ridge. The anconeal fossa is very deep and of considerable height (See Fig. 31.) The proportionate length of the radius and ulna is approximately like that of Rhinoceros bicornis. In the fossil form the shafts of both radius and ulna are, how-. FiG. 31. Diceratherium cooki Peterson. No. 2473, Coll. Carnegie Museum. Posterior and anterior views of humerus. X h ever, flatter than in the African species. In fully adult and old individuals this is chi
. The American diceratheres. Rhinoceroses, Fossil; Paleontology. 444 MEMOIRS OF THE CARNEGIE MUSEUM. the large entepicondyle and prominent supinator ridge. The anconeal fossa is very deep and of considerable height (See Fig. 31.) The proportionate length of the radius and ulna is approximately like that of Rhinoceros bicornis. In the fossil form the shafts of both radius and ulna are, how-. FiG. 31. Diceratherium cooki Peterson. No. 2473, Coll. Carnegie Museum. Posterior and anterior views of humerus. X h ever, flatter than in the African species. In fully adult and old individuals this is chiefly due to the rugose and prominent ridges, which actually come in contact with each other throughout the whole length of the bones, while in the recent form the median region of the shafts is rounded and the two bones are separated by a consider- able space. The shaft of the radius is quite straight, while the ulna as a whole is much bent backward, especially the upper half, a characteristic seen in the recent form. The carpal articulations differ from those in the African form to a marked degree. Thus the lunar articulates exclusively with the radius in Diceratherium, while in R. bicornis it encroaches to a considerable extent on the distal face of the ulna. On the other hand it is observed in a number of cases in Diceratherium that the cuneiform extends over upon the radius, forming a minute facet on the extreme ulnar border as well as on the palmar face. There is a considerable variation, especially in length and robustness, of the fore-arm of D. cooki, which is undoubtedly due to sexual and individual variation as well as age. Manus. Pis. LXIII; LXIV. The height and breadth of the carpus are. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Peterson, O. A. (Olof August), 1865-; Carnegie Museum. Pittsbur
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