576 UNGULATA. 



four with never a trace of the hallux. The absence of digit No. 1 

 may be therefore taken as a characteristic of the group. In the 

 Suidae and Hippopotaraidae, there are four digits in each foot, 

 but digits Nos. 2 and 5 are weaker than the others and may not 

 reach the ground. This change is accompanied by an elongation 

 of the metacarpals and metatarsals, metapodia as they are 

 called. In the Buminantia the outer digits are very small and 

 functionless as in the deer (Fig. 308) or entirely absent as in 

 Camelidae and some Bovidae, and the metapodia of the persisting 

 large digits (Nos. 3 and 4) are united into the so-called cannon hone. 

 In the Perissodactyla the modifications are slightly different. 

 Here in the tapir the manus has four complete digits (No. 1 being 

 absent), the pes three (Nos. 1 and 5 being absent) ; the rhinoceros 

 has three in both limbs, while the horse has only one complete 

 digit (No. 3) with traces of the metacarpals of digits 2 and 4. 

 In this sub- order digit No. 3 is larger than the others even in the 

 tetradactyle tapir (Fig. 309). The gradual elongation of the 

 metapodia is also manifest in this series as may be gathered from 

 an inspection of the figures (Fig. 316). The Ungulata are found 

 all over the world except the Australasian region. They are 

 almost all herbivorous and none purely carnivorous. The forms 

 with broad tetradactyle feet frequent places where the ground 

 is soft (rhinoceros, hippopotamus) ; they may be described as 

 almost semiplantigrade, for although they stand on their digits 

 the weight is partly borne by a large pad on the hinder side of 

 the foot. The majority, however, are purely digitigrade, and 

 walk on the tips of their reduced toes which are encased in hoofs. 

 These creatures inhabit hard ground, grassy plains and mountain 

 sides and are swift and active rumiers. 



There are three suborders, the Artiodactyla, the Perissodactyla, 

 and the Lipoterna. 



Sub-order 1. ARTIODACTYLA.* 



Digitigrade forms in which the axis of the limbs passes between 

 digits Nos. 3 and 4, these digits being symmetrical with each 

 other and their metapodia closely applied together or united into 

 a cannon bone. The premolars and molars are not alike and the 

 last lower molar is three-lobed. The first milk molar is not 



* W. Kowalevsky, Palaeontographica, 22, 1873-4. E. D. Cope, The 

 Artiodactyla, A^ner. Naturalist, 22 and 23, 1S8S-9. 



