CHAPTER XX 

 THE UNGULATES, OR HOOFED MAMMALS ORDER UNGULATA 



THE HOLLOW-HORNED RUMINANTS 

 Family BOVID^ 



IF WE accept the bats, in which the outermost fingers of the wings are clawless, 

 and some of the seals and their allies, the whole of the Mammals described in the 

 preceding chapters are characterized by having the digits of both the fore and hind- 

 limbs provided either with claws or with thin nails. Moreover, in the greater 

 number of instances, the fore-limbs themselves are endowed to a larger or smaller 

 degree with the power of free movement in several directions; these movements be- 

 ing displayed to the fullest degree among the Primates, where the hand can be ro- 

 tated upon the fore-arm, although they are also well developed in the Cat family. 

 Then, again, the number of digits in the great majority of these animals is five on 

 either one or both pairs of limbs, and in no instance is it less than four. Further, the 

 crowns of their cheek-teeth are never complicated by vertical and lateral infoldings 

 of the enamel, so as to produce when worn down an elaborate pattern. 



The Ungulate, or Hoofed Mammals, such as cattle, deer, camels, swine, horses, 

 tapirs, rhinoceroses, and elephants, of which we have now to treat, differ in many 

 important respects from the above. Thus, while no existing member of the order 

 has the feet provided with claws, in the great majority of cases the toes are inclosed 

 in solid hoofs, although in a few instances they are furnished with broad and flat 

 nails. Then, again, the movements of the fore-limbs are mainly or entirely re- 

 stricted to a backward and forward motion, and in no case can the fore-foot be rotated 

 on the fore-leg. Many extinct forms had four or five functional and well-developed 

 digits to the limbs, but in all living members of the order, except the elephants, 

 there are never more than four functional digits; and in a large number of instances 

 these functional digits are reduced to two, or more rarely three in number. 'Some 

 species, like the giraffe, have, indeed, but two digits to each foot, while in the horse 

 and its living allies only a single digit remains. 



It must not, however, be assumed from the last sentence that the 

 Un ulates toes are gradually reduced from three to two, and from two to one; 

 the fact really being that the reduction takes place along two different 

 lines, in one of which the number is diminished from four to two, and in the other 

 from three to one. As it is of primary importance, in order to understand the re- 

 lationship of existing Ungulates to one another, to have a clear idea of the manner 

 in which this reduction of the digits takes place, the subject may be dealt with in 

 some detail. In all the Ungulates the limbs have entirely ceased to be used as or- 

 gans of prehension, and there would seem to be no necessity why there should be 



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