1902.] OF HORNS AND ANTLERS. 215 



are not primitive, they are the expression of degeneration, of the 

 breaking up of a once powerfully developed bony growth. 



Fossil Giraffe-skulls are unfortunately still unknown, but 

 Samotherium with frontal and posterior protuberances, Sivatherium 

 with posterior growths hollow at the base and with frontal 

 growths, lastly Bralinnatheriwrn with posterior and frontal arma- 

 ments, are undoubtedly allied to the Giraffoid stock. We leave out 

 the unarmed Hydaspithermin and Relladotheriwm, which are 

 suspected by experts to be female Sivatheria. It has been ques- 

 tioned whether these armaments, huge, and sometimes branched, 

 were covered with skin and hair, or with horny sheaths. The 

 antlers of the original specimen of the male Sivatheriwrn clearly 

 show deep and strong impressions of the blood-vessels, extending 

 almost to the tips exactly as in Cervine antlers. They were 

 undoubtedly covered with skin, and it would be hardly fair to 

 assume that this and similar specimens happened to have died in 

 the velvet stage. The same applies to Samotherium. boissieri. 

 But it does not follow that these armaments were true antlers in 

 the sense that they were shed. Dr. Forsyth Major is inclined to 

 think that there are sutures between them and then- base. If 

 there are any, they simply indicate the line of transition or 

 demarcation which is usually seen between the pedicle and the 

 rest. The hindmost pair of armaments of Sivatherium are hollow 

 at the base, a fact which speaks decidedly against periodical 

 shedding ; and the broadness of the base supports this view, since 

 a good and permanent vascular supply from below was thereby 

 ensured. The much shortened shape of the skulls of Sivatherium 

 and Brahmatherium are unmistakable signs of specialization, 

 excluding the possibility that these huge creatures of the latest 

 Miocene or lowest Pliocene were the dii'ect ancestors of Giraffes ; 

 but they were near relations and contemporaries. 



We are now able to conclude that the evolution of Horns and 

 Antlers and similar cranial armaments has passed through the 

 following stages :— 



I. Exostosis. Subpei'iosteal ostotic outgrowths of the ci'anial 



bones, covered presumably with thickened skin-pads. 

 These armaments were multiple, occurring on various 

 parts of the skull. This type is rather old among the 

 XJngulata, witness the Eocene Amblypoda, e. g. Dinoceras. 

 It reoccurs amongst the Artiodactyla, which here alone 

 concern us. Protoceras of the Lower Miocene of Montana 

 is an almost ideal type in this respect, with its three or 

 four pairs of facial, orbital, and posterior bony excrescences 

 in the shape of uncouth i-idges and neat cones. (Text- 

 fig. 25, I, p. 216) 



II. Exostosis of the frontal bone producing a /^ecZzcZe, with 



epichondrosis of apical growth, which by subsequent basal 

 ossification becomes the antler. Skin originally unaltered, 

 haiiy ; this and the chondrosteoma are shed periodically. — 

 Cervine type. (Text-fig. 25, II, p. 216) 



