HOLLOW-HORNED RUMINANTS. 159 
generally small or absent. In the lower jaw, on the other hand, al! the incisor 
teeth are present, while the canine tooth on each side is in immediate contact with 
the outermost incisor; and since all the three pairs of incisors and the single pair 
of canines have nearly similar spatulate crowns, they appear to form a single series 
of four pairs of teeth. This may be easily verified by examining the lower jaw of 
a sheep or an ox. The six cheek-teeth on either side of both jaws are placed close 
together; those of the lower jaw being separated by a long space from the four 
pairs of spatulate teeth. In the fore-feet the third and fourth metacarpal bones, 
and in the hind-feet 
the metatarsal bones, 
are respectively fused 
into single “cannon- 
bones,” as shown in 
the two figures given 
on p. 154; while the 
two lateral pairs of 
toes are always small 
and rudimentary, and 
may be completely 
absent ; the toes them- 
selves being encased 
in complete hoofs. 
Another peculiarity of 
this group is that the 

stomach is divided into 
four complete cavities, 
into the first of which 
the food is temporarily 
received, until it is 
regurgitated into the 
mouth, when it is 
completely masticated, 

and afterwards con- SKULL OF SWAYNE’S HARTEBEEST, TO SHOW HORNS. 
veyed to the true (From Sclater, Proc. Zool. Soc., 1892.) 
digesting stomach. 
This process is known as the function of “ chewing-the-eud,” or ruminating: and 
the Ungulates in which it occurs are consequently termed Ruminants. The rumin- 
ating function is, however, developed in the camels and chevrotains, as well as in 
the assemblage of four families constituting the present group; but as the camels 
and chevrotains differ in several important respects, it is convenient to designate 
the group under consideration as the true Ruminants, or technically, the Pecora. 
It has yet to be mentioned that all the ruminating even-toed Ungulates are 
characterised by the peculiar structure of their cheek-teeth. It will be observed 
from the figure of the upper molar tooth of the nilgai given on p. 155, and also 
from that of the four-horned antelope on p. 158, that these teeth consist of four 
distinct columns, of which the innermost pair are crescent-shaped, with the horns 
