THE MAMMALIA. 45 



a vacant space, followed by six grinders. The dental formula, 

 then, for a typical ruminant animal is 



. o — o o — o 2 7. 2 2 



t. , c. ,p?n. ^ — ^, in. - — ^ = 32 



3—3 I— i'^ 3—3 3—3 ^ 



The departures from this typical form occur in the camels, the 

 Chevrotains {Tragtilus), and in some of the deer. The Chevro- 

 tains are survivals of the Miocene family of TragulidcB. They 

 are characterised by a total absence of horns, by the possession of 

 canine teeth, and by other peculiarities of structure which make 

 them an intermediate form between the hog and the deer, They 

 are the smallest and least specialised Ruminants existing. The 

 true Ruminants, though animals of a peculiarly modern type, 

 have yet seen their palmiest days. The Post-Pliocene was the 

 age when the true stags attained their largest size and great- 

 est abundance. The Irish Elk (Cervus Megaceros) was remarkable 

 for its great size and the enormous dimensions af its spreading 

 antlers, which attained an expanse of as much as ten feet from tip 

 to tip. It appears and disappears in the Post-Tertiary period. 

 Another remarkable type of stag, with antlers of very complicated 

 form, is found in the Norfolk forest-bed. 



Of the family of the Cavicornia (oxen, sheep, goats, and ante- 

 lopes) the sheep appear to be the most recent. No remains of 

 OvidcB are found in any deposits older than the Post-Miocene. 

 Nor have they diminished in size, though the beautiful Big Horn of 

 the Rocky Mountains seems threatened with extinction by man, 

 and the Musk-Ox (Ovibos Moschatus) has found its last refuge in 

 Arctic America. Formerly, this curious ox-like sheep roamed 

 throughout the Quaternary deposits of Europe and Asia. Doubt- 

 less, though the sheep have not yet diminished, the hand of fate 

 visibly points in the same direction for them as for other species. 



The oxen are much older than the sheep, extinct species of 

 the living genus Bos being found in the Upper Miocene of 

 India, together with the extinct genera, Hemibos and Amphibos. 

 The palmy days of the oxen were the same as those of the stag, 

 in the Post-Pliocene period. And probably it would not be too 

 much to say that if the ox had not been peculiarly useful to man, 

 the genus would now have been extinct in Europe — would have 



