78 



RUMINANTS AND THEIR DISTRIBUTION. 



26. A left 

 Upper Cheek-Tooth of 

 an Antelope. 



of ruminants being of a complex structure, unknown 

 elsewhere ; the last thres of these teeth in the upper jaw 

 (Fig. 26) being composed of four columns, of varying 

 height, of which the two inner ones 

 are crescent- shaped ; such a type of 

 tooth being termed selenodont. The 

 lower grinding-teeth having their 

 crescents directed the opposite way to 

 those of the upper jaw, and both 

 upper and lower teeth consisting of 

 layers of different hardness, we can 

 scarcely imagine a better masticating 

 machine than is presented by the 

 opposition of the two series of 

 grinding - teeth of these animals. 

 Bearing in mind this structure, the 

 definition of cud-chewing, selenodont 

 mammals will suffice to distinguish 

 the ruminants from all other animals. 

 When, however, we say that these characteristics dis- 

 tinguish them from all other mammals it must be added 

 that this refers only to those of the present day, for a 

 transition can be traced through extinct forms to the more 

 simply constructed grinding-teeth of the swine. We have 

 already seen how the Mosaic law recognized the similarity 

 in the structure of the hoofs of the ruminants and the 

 swine, and it is curious that while under the Cuvierian 

 system of zoology these two groups were widely sundered, 

 modern palseontological researches have shown that they 

 are really closely related, the want of the power of chewing 

 the cud, with the correlated absence of the selenodont 

 structure of the teeth, being the chief essential features 

 in which the latter differ from the former. 



Here a curious problem is presented to those who put 

 their faith in a mode of evolution dependent only upon 

 so-called natural causes, in that it is impossible to give 

 any adequate explanation of what advantage would be the 

 development of an incipient selenodont structure in the 

 teeth of the early swine-like ungulates, or at what precise 

 stage the function of chewing the cud, with the con- 



