HOLLOW-HORNED RUMINANTS. 



'59 



generally small or absent. In the lower jaw, on the other hand, all 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- 

 veyed to the true 

 digesting stomach. 



This process is known as the function of " chewing-the-cud," 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 



SKULL OF SWAYNE'S HARTEBEEST, TO SHOW HORNS. 

 (From Sclater, Proc. Zool Soc., 1892.) 



