BE. E. EAY LANKESTER ON OKAPIA. 



291 



Giraffa, and its margin is not formed by a thin upstanding rim of bony matter 

 as it is in Giraffa and nearly all Pecora, but is heavy, rounded, and thick. This 

 seems to me to be an archaic character — the sharp thin edge of the orbit being a 

 modern and truly Pecorine development. It is, nevertheless, found that the double 

 notch, or pair of notches, on the lacrymal border of the orbit have precisely the same 

 position and character in (what I am constrained to regard as) the archaic orbit of 

 Okapia as in tlie modernized orbit of Giraffa. 



Text-fig. 11. 



View from above of tlie fronto-parietal region of the skull of a very young Giraffe. The parietal epiphyses 

 were already ossified, but separable, and are here removed. 



oec.h., exostosis of the occipital crest, which in some adult Giraffes forms a second pair of " horns " (iive-horned 

 Giraffe) ; gtl., the Girafiine lateral tumescence, seen here to originate in the parietal bone, which carries 

 the conical epiphysis and forms the Giraffe's paired "horns"; ot.l., the position of the Okapi's lateral 

 tumescence of the frontal bone, absent in Giraffe ; zy., z5'gomatic arch ; po., posterior angle of the orbit ; 

 ao., anterior angle of the orbit ; yl.v., prselaorymal vacuity ; sof., supraorbital fossa ; sfp., fronto- 

 parietal suture. 



IV. — The Akeas of Tumescence op the Giraffine Skull and the Nature and 



Origin of the Horns of Pecora. 



In order to make an intelligent comparison of the skull of Okaina and Giraffa in 

 regard to the presence and absence of what are called " horns," it is necessary to 

 discriminate between the varieties of horns presented by various groups of Pecora and 

 to accept one theory or another as to their origin and relationships. 



The word " horn " is a comprehensive term of various and uncertain meaning. It 



