CHAPTER IX 
THE ORDER UNGULATA 
UnpeEr this term may be included provisionally a large and rather 
heterogeneous group of mammals, the existing members of which 
form the Pecora and Bellue of Linnzus, the Ruminantia and 
Pachydermata of Cuvier. A few years ago it was found convenient 
to restrict the order to a well-marked and distinctly circumscribed 
group, comprising the two sections known as Perissodactyla and 
Artiodactyla, and to leave out such isolated forms as the Elephant 
and Hyrax ; but the discovery of a vast number of extinct species, 
which could not be brought under the definition of either perisso- 
dactyle or artiodactyle Ungulates, and yet are evidently allied to 
both, and to a certain extent bridge over the interval between 
these and the isolated groups just mentioned, makes it necessary 
either to introduce a number of new and ill-defined ordinal 
divisions, or to widen the scope of the original order so as to 
embrace them all. 
The existing forms are all animals eminently adapted for a 
terrestrial life, and in the main for a vegetable diet. Though a 
few are more or less omnivorous, and may under some circumstances 
kill living creatures smaller and weaker than themselves for food, 
none are distinctly and habitually predaceous. Their teeth are 
markedly heterodont and diphyodont,—the milk set being well 
developed and not completely changed until the animal attains its 
full stature. The molars have broad crowns with tuberculated or 
ridged surfaces. There are no clavicles.t Their toes are provided 
with blunt, broad nails, or in the majority of cases with hoofs, more 
or less enclosing the ungual phalanges. The scaphoid and lunar 
bones of the carpus are always distinct. The humerus has no 
entepicondylar foramen. The number of digits varies from five to 
one; and the radius and ulna may be united together. 
1 Since this was in type the discovery of transient rudimentary clavicles in 
the embryo of the Sheep has been announced by Wineza (Morpholog. Jahrh. xvi. 
p. 647). 
1 
[os 
