1901.] 



riVE-HORNEB GIRAFFE FROM MOUNT ELGON. 



477 



The following are the measurements in millimetres of the four 

 Elgon skulls, which being all perfect, wild-killed specimens, fully 

 adult, may afford a standard for comparison with specimens from 

 other localities : — 



Extreme length (mesially ) , 



Basal length 



Greatest breadth 



Nasal opening, length from gnathion 

 to junction of nasals with pre- 

 maxilla 



Do. breadth 



Muzzle to orbit 



Distance between tips of horns 

 (centres) 



Muzzle to front of anterior premolar. . 



6 

 (old). 



6 

 (adult). 



642 



2- 



688 



681 



622 



593 



598 



577 



564 



321 



273 



279 



277 



157 



174 



174 



161 



72 



70 



69 



65 



386 



386 



375 



359 



157 



176 



83 



135 



247 



247 



240 



243 



Secondly as to the structure, homologies, and evolution of the 

 posterior horns, which, as already said, are present in some degree 

 in all Giraffes, or at least in all male Giraifes. These structures, 

 on the analogy of the masts of a ship, it may be convenient to 

 speak of as " mizen " horns ^ 



Externally, although of no great length, even where most de- 

 veloped, they yet show a certain community of structure with the 

 other horns, as the hairs are similarly whorled around and over 

 them, and in colour, like the other three, they are yellowish below, 

 crowned with black terminally. 



Turning to the skull, the first drawing (text-fig. 43, p. 478) 

 show^s the back part of the oldest male cranium of the Johnston 

 series (that belonging to the head shown in text-fig. 42, p. 476). 

 A section has been made through the posterior projection to 

 show its thickness and the extent to which the cranial vacuities 

 penetrate it. 



Here it will be seen that the mizen horn is placed behind the 

 end of the masseteric fossa of the parietals, in front and quite 

 clear of the supraoccipital one for the attachment of the nuchal 

 tendons and muscles. The horn is always just in this position ; and 

 when examined in a young specimen (text-fig. 44, p. 478) appears 

 to be on the antero-external angle of the combined interparietal 

 and supraoccipital, close behind the parietal suture. But in old 

 animals it no doubt trespasses on the latter bone. 



Some sort of a swelling may be perceived at this point in every 

 male Giraffe's skull, even in such as would be at once said to have 

 no mizen " horns." Taking, for instance, an old male skull from 



^ The word " posterior " would be fruitful of confusion with the main horns, 

 which are the posterior ones in animals without mizen horns ; " occipital " is 

 equally objectionable, on account of the varying position with regard to the 

 cranial bones of all three pairs of horns; " fore," " main," and "mizen" can 

 give rise to no ambiguity. 



Proo. Zool. Soc— 1901, Vol. II. No. XXXII. 32 



