V * >^ - 



I* 



2OO 



* 



r' 

 Jt 



the likenesses which Titanotherium shows to the Artiodactyla 

 must be either purely superficial and secondary, or a cropping 

 out of ancient characters which had been dormant for many 

 generations. 



Horns. The Ungulata are the only order of mammals which 

 possess horns ; as they are on the whole a more defenceless group 

 than the Carnivora, it may be that the horns are a counterpoise 

 to the teeth and claws of the latter ; need for defence and for 

 armature in the combats with their own kind for the favours 

 of the does has led to a different kind of protective and 

 aggressive mechanism. Horns as weapons are, however, parti- 

 cularly effective in this group wherever they exist. A Ruminant 

 is most frequently a large and heavy animal without the agility 

 and litheness of the Carnivore. It is precisely to this sort of 

 animal, where weight is an important consideration, that horns are 

 the most suitable weapons. This is further shown by the fact 

 that although the general term horn is used to describe the 

 weapons of the Ungulate mammals, there is more than one kind 

 of structure included under this general term ; it is indeed prob- 

 able that the extreme terms in the series of horns have been 

 independently acquired by their possessors. There is but little 

 in common between the horns of a Giraffe and of a Rhinoceros. 

 In the Rhinoceros we have one or two horns, in the latter 

 case one placed behind the other, which are purely epidermic 

 growths ; they may indeed be regarded as matted masses of hair, 

 borne, it is true, upon a boss of bone, which however is not 

 a separate structure. The Giraffe supplies us with the simplest 

 term in that series of horns which are partly epidermal and partly 

 bony. The paired horns of this animal have often been contrasted 

 with those of the Deer, for example ; but there is no fundamental 

 difference between them. In the Giraffe a pair of bony out- 

 growths, originally separate from the skull which bears them, but 

 ultimately ankylosed to it, are covered by a layer of entirely un- 

 modified skin. A distinction of undoubtedly practical importance 

 is usually drawn between the Hollow-horned Ruminants, i.e. Oxen, 

 Goats and Antelopes, and the Deer tribe. There is nevertheless 

 no fundamental distinction. In the Antelopes there is a core of 

 bone, the " os cornu " as it has been termed, which is covered 

 by a horny layer, the horn proper, variously modified in shape and 

 size according to the genus or species. In the Deer there is the 



