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Show A SPECIMEN OF THE OKAPI. 347 III. Characters which the OJcapi has in common with the Giraffe. Those characters mentioned in paragraph I. which are equally shared by all three animals, together with the following 1. Horns covered by the skin; their mode of growth in the main identical. 2. Extensive air sinuses of the cranial bones. 3. Shape of the mandibular angulus of the Okapi approaching the Giraffe, though somewhat intermediate between the form in the latter and that of Palceotragus. 4. Fusion of the five tarsal bones mentioned-this takes place in the two known skeletons of the Okapi; it is not the general rule in the Giraffe. IY. Characters in which the Okapi differs from the Giraffe. 1. Smaller size. 2. The differential characters of the skins. 3. All those features which, apart from the family characters, the Okapi has in common with Palceotragus. 4. Cranial air-sinuses less developed in the Okapi, with the exception of those in the bony palate, which are conversely much more developed in the Okapi than in the Giraffe. 5. Narrow frontal region ; orbits not telescopic (compare text-figs. 63 and 64 with text-fig. 67). 6. More anterior position of the orbits. 7. Tympanic bulla? and ears larger. 8. Apparent later development of the horns, which remain smaller. Y. The Okapi holds an intermediate position between Palceotragus and the Giraffe in the following characters:- 1. Degree of development of the air-sinuses in the cranial roof-bones. 2. Position occupied by the paired horns (compare text-fig. 7 (p. 73) with text-fig. 6 (same page) and text-figs. 11 and 12 (p. 76). 3. Conformation of the mandibular angulus, which is more produced backward than in Palceotragus, but less so than in the Giraffe. See the side views of the crania on pp. 73 and 76. YX A very few features are common to the Giraffe and to Palceotragus, to the exclusion of the Okapi. 1. Large incisors and canine. 2. Backward situation of the orbits in relation to the tooth-series. 3. Broad frontal region ; orbits telescopic. Almost all the characters in which the Okapi differs from the Giraffe are more primitive features. The exceptions are the lar°e air-sinuses in the bony palate of the Okapi, and piesumably also the large size of the ears. As pointed out, the Okapi shares a great part of these primitive features with the fossil Giraffid* |