OCR Text |
Show 696 DR. E. LONNBERG ON THE [June 19, The material, consisting of a skull of a young calf and skulls of adult bulls and cows, was derived from the same source that I have already mentioned, namely from Professor A. G. Natborst's Greenland Expedition in 1899. Intermediate stages are wanting for the reason, already mentioned, that no such stages were observed by the Expedition. The most striking features in the skull of an adult Musk-ox are the situation and great development of the born-cores and the protruding orbits. These characteristics indicate specializations from an ancestral type ; and they have also, naturally enough, produced correlative changes of the skull. This must be borne in mind ; and the primary and secondary conditions ought to be estimated at their right value with regard to the systematic position of tbe Musk-ox-that is, the changes of structure which have taken place during the development of the present specialized type Ovibos moschatus, and which separate it from other Cavicornia, ought, if possible, to be distinguished from those characteristics which are more ancient and which already belonged to the forms from which the Musk-ox has been differentiated. If the latter can be traced, they might give some hints as to the affinity and at the same time the systematic position of tbe Musk-ox ; the former, on the other hand, would show in which points the animal has diverged from the common stock. With regard to the arrangement of the frontals and the parietals, three principal types can be discerned among the Cavicornia, as has been pointed out by Biitimeyer l. Firstly, the Antelopes, with a horizontal parietal region, quite, or at least nearly, in the same plane as the frontals. Secondly, the Sheep and Goats, in which the fronto-parietal plane is bent in an angle which forms a transverse ridge on which the horn-cores are situated ; this " Knickung " has taken place on the frontals, and the parietal region slopes more or less steeply towards the occiput: and thirdly, the Oxen, in which the frontals alone form the roof of the brain-case and in which the parietals have been pressed backwards and towards the sides. The position of the horn-cores is also very characteristic for each of these three groups, although exceptions are found. As a rule, the horns of the Antelopes arise above or near the orbits. In the Goats and the Sheep the horns are placed on the transverse frontal ridge, which in them forms the summit of the head.- The Oxen have their horns situated in the posterior corners of the skull at a considerable distance from the orbits. These three groups may thus be regarded as representing three different types of development, although of different value. The first is, of course, the most primitive, from which the others may be derived. The second and third have in different ways reached the same goal, namely of getting the horns on the most effective and suitable place, that is on the summit of the head. If it is asked, now, to which of these types does Ovibos show the greatest likeness, it is evident that the 1 ' Versuch einer natiirl. Geschichte des Rindes,' Zurich, 1867. |