88 



THE TWO-TOED ARTIODACTYLA. 



Diverse as the Cavicornia are in external 

 form, they yet agree so closely in their 

 general structure that the dividing up of this 

 numerous group into families becomes very 

 difficult, if not impossible. There are many 

 forms in which the horns belong only to the 

 males, but frequently there are closely-allied 

 species in which both sexes are horned. 

 The dentition is remarkably uniform; the 

 upper incisors and upper canines are alto- 

 gether wanting, the lower incisors, to the 

 number of eight in all, have very similar 

 forms; the cheek-teeth, always six in number 

 in each half of each jaw, exhibit on the 

 surface of the crown typical half-moon-shaped 

 folds; the three premolars gradually assume 

 the form of the true molars. The forms 

 presented by the teeth may indeed serve to 

 distinguish genera and species, especially 

 through the absence of side-columns in the 

 molars of the large species, but these forms 

 vary within very narrow limits. 



The Cavicornia almost always have pretty 

 well developed accessory hoofs; some have 

 tear-pits, others not; but here also there are 

 transitions which render it impossible to fix 

 definite boundaries. Pretty much the same 

 holds good with respect to all the other 

 characters; from the plump forms of the ox 

 genus we pass by gentle gradations to forms 

 the most elegant and graceful, such as 

 those of the gazelles. Though most of the 

 species live in very numerous flocks, there 

 are others which are to be met with only in 

 pairs; some are stationary in their abode, 

 others on the contrary undertake great mi- 

 grations ; some prefer moist places, morasses, 

 and the banks of running and standing waters, 

 others the dry and withered plains, others 

 again the steep slopes of the mountains ; the 

 Tropics are not too hot for them nor the 

 Arctic regions too cold. 



The Cavicornia are usually broken up into 

 sub-families or groups, which are designated 

 by the names antelopes, goats, sheep, and 

 oxen. But in order to avoid mistake, we 



must repeatedly insist on the fact, that these 

 subdivisions have no sharp lines of demarca- 

 tion, that on all sides we meet with transitional 

 forms, with respect to which doubts might be 

 raised as to the group to which they ought 

 to be referred, so that we must consider these 

 groups only as aids which help us to connect 

 the less clearly defined forms with well- 

 characterized types. 



The Antelopes. 



The antelopes (Antilopida) are a collector's 

 group, if I may so express myself. They 

 cannot be characterized zoologically. They 

 exhibit the most various forms. Certain 

 antelopes can scarcely be distinguished from 

 oxen, others resemble goats or sheep. There 

 is not a single character common to all the 

 animals so called. We accordingly renounce 

 the idea of characterizing them in any other 

 way than in the words of Pallas, who said, 

 naturalists have given the name of antelopes 

 to those ruminants with hollow horns which 

 cannot, without violence, be grouped with the 

 oxen, the goats, or the sheep. 



We have already pointed out in the opening 

 remarks on the ruminants that a connecting 

 link between the deer and the hollow-horned 

 ruminants exists in the Pronghorn Antelope 

 {Antilocapra americana), fig. 164, which 

 inhabits the broad plains on both sides of 

 the Rocky Mountains from Mexico as far as 

 the 53d degree of northern latitude. The 

 horns are without doubt constructed on the 

 type of those of the Cavicornia ; they have a 

 solid bony core and a horny case of little 

 thickness. In the young animals these horns 

 are simple prongs. These first horns are 

 often changed, and the change takes place 

 not by the shedding of the bony core as in 

 the deer, but by the growth of a new horny 

 case, which gradually raises and finally thrusts 

 off the old one. When the horns have 

 acquired their permanent form they are no 

 longer shed, and then they are forked pretty 

 much in the same manner as those of the 



