CHAPTEK IX 



THE ORDEK UNGULATA 



UNDER this term may be included provisionally a large and rather 

 heterogeneous group of mammals, the existing members of which 

 form the Pecora and Belluse of Linnaeus, 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. 1 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 Wincza (Morpholoq. Jahrb. xvi. 

 p. 647). 



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