1902.] A SPECIMEN OF THE OKAPI. 347 



III. Characters which the OTcapi has in common toith the Girajffe. 

 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. 



IV. Characters in lohich the Ohapi differs fro')n 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 bullfe and ears larger. 



8. Apparent later development of the horns, which remain 

 smaller. 



V. The Okapi holds an intermediate position between Palceo- 

 tragus and the Giraffe in the following characters : — 



1. Degree of development of the air-sinuses in the ci-anial 

 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 Palceotrccgus, but less so than in the 

 Giraffe. See the side views of the crania on pp. 73 and 76. 



VI. A very few features are coimnon to the Giraffe a,nd to 

 Palceotragus, to the exclusion of the Okapi. 



1. Large incisors and canine. 



2. Backward situation of the oi-bits 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 

 large air-sinuses in the bony palate of the Okapi, and presumably 

 also the large size of the ears. As pointed out, the Okapi shares 

 a great part of these primitive featvires with the fossil Giraffidae 



