20 THE OX AND ITS KINDRED 
divergence of their lower extremities, which lack 
pulley-like ridges for articulation with the upper- 
most toe-bones. The toe-bones themselves are like- 
wise decidedly different from those of the typical 
ruminants, as may also be seen in the same figure, 
and do not show the markedly paired character so 
distinctive of the latter. As this book is not a 
natural history of the ungulates, or even of the 
artiodactyles, these few features will suffice to dis- 
tinguish the Tylopoda from other ruminants. 
Having now eliminated two somewhat aberrant 
groups of ruminants, it remains to indicate some of 
the leading features of the typical section of that 
assemblage of artiodactyle ungulates technically 
known as the Pecora, or cattle-like ruminants, among 
which is included the ox. 
These Pecora are collectively characterised by the 
presence of four separate chambers in the stomach 
(see figure on page 17), by the absence of incisor 
teeth in the front of the upper jaw, and by the pair 
of lower canines and the three pairs of lower incisors 
forming a closely approximated series of eight very 
similar teeth arranged somewhat in the shape of a 
bow, and having when unworn more or less chisel- 
shaped or spatulate crowns, these biting against a 
callous pad on the toothless front of the upper jaw. 
The cheek-teeth of both the permanent and the 
milk, or deciduous, series have also a peculiar and 
characteristic type of structure, although this is shared, 
with some modifications, by the chevrotains and 
camels, and likewise, in a less specialised degree, by 
certain extinct groups of artiodactyles not generally 
termed ruminants, although some or all of them 
probably chewed the cud in ruminant-fashion. 
