110 



PROF. E. RAY LANKESTER ON THE 



[Feb. 5, 



(though not senile) Giraffe, and the relation of the sinus of the 

 parietal and frontal to the lateral horn, is shown in the figures (text- 

 figs. 33 &, 34) which were prepared from photographs of sections 

 of a skull made under my direction. It will be observed that it 

 is not possible in such sections to distinguish the line of ankylosis 

 of the separate bones ; we can only guess somewhat vaguely as to 

 what belongs to each of the three elements fused together, viz., 

 ossicone, parietal, and frontal. 



Text-fig. 33. 



Skull of Giraffe, left side ; kej^-figure, a little larger than one-sixth (linear) of the 

 natural size, showing the directions in which the skull was cut. 



(From the Proc. Zool. Soc. London, 1904, vol. i. p. 151.') 



Thus we see that the "ossicone " of the adult Giraflfe is essen- 

 tially but a cap of bony substance fitting over the great upgrowth 

 or conical tumescence of the cranial wall — at the first most marked 

 in the paiietal area, — and that it makes its first appearance as a 

 solid gi-owth of fibrous tissue resting on the flat cranial roof. 

 The same conclusion may legitimately be drawn from what we 

 can see of the early and later conditions of the ossicone in 

 Okapi*. 



* The tumescence of the frontal bone of each side in Okapi, which ankyloses with 

 the ossicone overlj'ing it, is of considerable volume, like those to which the parietal 

 gives rise in the Giraffe. I shall have an opportunity of describinsr this structure 

 more fully hereafter. At the present moment I desire to draw attention to a curious 

 fact with regard to the rudiment of a median horn in Okapi. The base of the nasal 

 bone gives rise to a small but well-marked median tumescence in the Okapi. I 

 described this in Sir Harry Johnston's specimen (Trans. Zool. Soc. vol. xvi.). In horn- 

 bearing skulls of Okapi this is more pronounced than in the hornless speeimeus ; it 



