309 



THE UNGULATA. 



The Ungulata, or hoofed mammals, constitute one of 

 the largest and most important orders of the animal king- 

 dom. They are all herbivorous ruminants with a few 

 notable exceptions that are omnivorous ; and none of them 

 have the digits of the fore or hind limbs provided with 

 either claws or nails, as is the case with other animals. 



In the great majority of cases the toes of Ungulates are 

 encased in solid hoofs, although a few species are fur- 

 nished with broad flat nails. Many extinct forms have 

 four or five well developed digits to the limbs, but in all 

 living members of the order except the elephant which 

 has five, there are never more than four functional digits ; 

 and in a large number of instances these functional digits 

 are reduced to two, and in some cases to three, while 

 in the horse and its living allies only a single digit re- 

 mains. 



Richard Lydecker, in his "Royal Natural History," 

 says : "As it is of primary importance in order to have a 

 clear idea of the manner in which this reduction of digits 

 takes place, to understand the relationship of existing 

 Ungulates one to another, the subject may be dealt with 

 in some detail. 



"In all the Ungulates the limbs have entirely ceased 

 to be used as organs of prehension, and there would seem 

 to be no necessity as development advances why there 

 should be any adherence to the primitive five-toed type. 

 The majority of the members of the order being, however, 

 unable to protect themselves against foes, and being also, 

 in proportion to their height, heavy-bodied animals, the 

 attainment of a high degree of speed was essential to 

 their well-being and development, if not for their actual 

 existence. For such a kind of life it will be obvious 

 that the. greater the length and slenderness of limb, the 

 greater will be the speed. Now, in order to produce a 

 long and slender, and at the same time a strong limb, from 

 a stout and short-toed one, greater strength will clearly 

 be attained by reducing the number of the toes, and 

 lengthening and strengthening those which remain, rather 

 than by lengthening the whole of the five toes, the slender 

 bones of which would be liable to fracture by the concu»- 



