480 



ME. OLDEIBLD THOMAS ON THE 



[Nov. 19, 



no certain evidence), there is in the smaller one (text-fig. 46) an 

 unusual thickening of the posterior ci'est which may possibly be 

 an indication of the mizen horns. 



Text-fig. 46. 



Young Okapi. Postero-extenial view of the occipital crest. 



In reference to the position of the mizen horns close to or 

 near the junction of two bones, it is to be noted that all Giraffes' 

 horns are so situated, the fore one on the naso-frontal \ and the 

 main pair on the fronto-parietal suture. Now it has been very 

 definitely said both by Owen " and Nitsche^ that the main horns 

 are primarily on or at least over the frontal, and only secondarily 

 trespass on the parietal ; but the youngest horned skull that I have 

 seen (that given in text-fig. 44, p. 478), shows clearly the horns 

 situated as much on the parietals as on the frontals, so that there 

 would appear to be some variation in this respect. 



On the analogy of other horned Ungulates, it has naturally been 

 thought that the relationship that the liorns bear to particular 

 bones was of much essential importance when estimating their 

 homologies. But I would submit that in the Griratfidse this 

 importance may readily be overrated, for in them the horn is a 

 separate dermal ossification, developed in the skin over the skull, 

 and at early stages movable on it ^. Thus it may surely with 

 equal ease settle on and anchylose with any bone of the skull it 

 may form over, or on the junction of two of them. On the other 

 hand, with the Bovidse, where the horns, though equally separate 

 and dermal in the beginning, have been long associated with the 

 frontal only, and with the Cervidse, where they are actually out- 

 growths of that bone, the matter is difierent, and in estimating 



^ In young Giraffes the swelling for the horn is more frontal than nasal, 

 but the corresponding convexity in the Okapi is more nasal than frontal, 

 2 Trans. Zool. Soo. iii. p. 26 (1842). 

 ^ Studien liber Hirsche, p. 68, 

 ■" Fi^e Owen, L o. 



