It is exceedingly difficult to separate the Antelopes from the Sheep, Oxen, and Goats. Their inclusion along with these creatures in one family, Bovidae, shows that no differences of an important character exist. The term Antelope is rather of popular than {308} of zoological significance. As a rule there are horns in both sexes; but this rule is not without exceptions, of which one is the genus _Strepsiceros_, the Koodoo. Many other Bovidae are horned in the males only, e.g. _Saiga_, _Tragelaphus_. The Antelopes further differ from the true Oxen in their more graceful build, and in the fact that the horns, if they curve at all, generally curve backwards towards the neck. In the Oxen, on the other hand, the build is stouter, and the horns usually curve outwards. The same remarks apply to the Sheep. Such an Antelope, however, as the Eland (_Orias_) is very Ox-like in habit. Another feature which may be remarked upon, though not of absolute differential value, is that while the Antelopes are as a rule smooth and sleek in their skins, the Oxen tend to be rough and shaggy. The Zebu, however, in this, in its hump, and in general aspect, is far from being unlike an Eland. But then the Zebu is a domestic race, and we do not know what the wild stock was like. It is perhaps with the Goats that the Antelopes have the nearest affinities, and it is difficult to place such a form as _Nemorrhaedus_, and indeed some others. In the Antelopes as a rule the middle lower incisors are larger than the lateral ones; in the Sheep and Goats they are alike in size. The parietal bones, too, in the Antelopes are moderately large and are much shortened in the remaining Cavicornia, especially in the Oxen. As the Antelopes are the oldest, so far as we know, of all bovine animals, one would expect to find them combining the characters of the rest. But they do this so effectually that a disentanglement is really impossible. They date from the Miocene. Antelopes are now limited to Europe, Asia, and Africa; they have always had the same range, though more abundant in former times in Europe. They preponderate now in tropical Africa, and abound in genera and species. Messrs. Sclater and Thomas[211] allow altogether thirty-five genera, of which twenty-four are exclusively Ethiopian in range. In the following summary of the group Messrs. Sclater and Thomas's work is followed. They commence with a section or sub-family of which the type is the Hartebeest.