200 HORNS CHAP. 
the likenesses which 7Z%tanotherium 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 
ageressive 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, 7.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 
