THE HOLLOW-HORNED RUMINANTS 



749 



characteristics. In all the members of this assemblage of four families there are no 

 front (or incisor) teeth in the upper jaw; and the upper tusks or canines are generally 

 small or absent. In the lower jaw, on the other hand, all the incisor teeth are pres- 

 ent, 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 metatar- 

 sal bones, are respec- 

 tively fused into single 

 ' ' canon bones, ' ' as 

 shown in the two fig- 

 ures given on p. 744; 

 while the two lateral 

 pairs of toes are 

 always small and rudi- 

 mentary, and may be 

 completely absent; the 

 toes themselves being 

 incased in complete 

 hoofs. Another pe- 

 culiarity of this group 

 is that the stomach is 

 divided into four com- 

 plete cavities, into the 

 first of which the food 

 is temporarily re- 

 ceived, until it is re- 

 gurgitated into the 

 mouth, when it is 

 completely masticated 

 and afterward 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 ruminating function is, how- 

 ever, 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 

 characterized by the peculiar structure of their cheek-teeth. It will be observed 



SKULI, OF SWAYNE'S HARTEBEEST, TO SHOW HORNS. 

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



