696 DB. E. L0NNBEBG ON THE [Juae 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. Or. 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 the Musk-ox — that is, the changes of structure which have taken 

 place during the development of the present specialized type 

 Ovibos moschatns, 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 the 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 Eiitimeyer 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 con- 

 siderable 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 Rir.de*,' Zurich, 1867. 



