| OCR Text |
Show 1900.] STRUCTURE OF THE MUSK-OX. 715 animal aud the Bovina. But, on the other hand, Ovibos must have sprung from a form which was capable of developing accessory (basal) tubercles; and that such tubercles are to be regarded as the origin of the accessary columns also in Ovibos is proved by the fact that sometimes these elements remain in a more primitive stage as free independent pillars of cylindrical shape occupying the place of the accessory columns. This is the case in both upper molars of the hindmost pair in au old bull. But as the ancestors of Ovibos must be sought for among ruminants with accessory elements on the molars, these progenitors of the Musk-ox could not have been Sheep, because the latter have specialized their teeth without retaining; any of the accessory columns of the Musk-ox elements. Neither could it be assumed that tbe accessory columns of the Musk-ox have originated independently in this animal. The result of the above discussion may be stated thus : the dentition of the Musk-ox as well as tbe other characteristics of the skull do not indicate any Ovine affinities, but point to a comparatively primitive origin from which Ovibos has been specialized in its own peculiar manner. It deserves consequently to maintain its position in a separate subfamily. Sect. 4.-COMPARISON BETWEEN THE SKULL OF THE MUSK-OX AND THAT OF BuDORCAS. Through the kindness of Geheimrath Dr. Mobius I received permission to borrow a skull of Budorcas from the Zoological Museum of Berlin. I regret to say that the specimen sent to me had been so badly damaged, that a comparison cannot be made except with the facial portion of the skull. The nasals oiBud)rcas are much more curved, transversally as well as longitudinally, than those of Ovibos, and their outline is also quite different. Their greatest breadth, not quite a third of the length, is at a point a little behind the middle. They are expanded laterally in an obtuse angle so that each bone becomes triangular in outline. In Ovibos the greatest width of the nasals is at their posterior end, and their lateral border is a straight line. The greatest width of the nasals is about a fourth of the length, more or less, in the Musk-bull, in the Musk-cow not even that. The nasals of Budorcas are pointed anteriorly without any lateral notch, \vhich is more or less conspicuous in the more blunt nasals of an adult Ovibos, although it is small in a cow. The great distance between tbe end of the nasals and intermaxillaries in Budorcas, which is greater than tbe length of the nasals, indicates a much greater development of the soft parts of the nose than in the Musk-ox. The shape of the nasals of Budorcas can therefore be derived from that of a more general form like Nemorhcedus on the assumption that they have been shortened, as is always the case when the nose attains a more or less trunk-like development. As a result of such a development, the intermaxillaries are very |
