704 DR. B. LONNBERG ON THE [June 19, 



but it is hardly as large as in the calf, measuring 42 mm. in length 

 but only 17 in width. In an adult bull the same measurements 

 are (not counting spines) 31 mm. in length and 14 in width. The 

 shape of the bulla cannot therefore be of classificatory value in 

 this animal. 



The pars mastoidea is visible on the occipital surface as a narrow 

 strip between the paroccipital and the squamosal, which latter 

 forms the lateral margin of this surface. At the upper end of the 

 mastoid there is, in the calf, a small separate bone visible, with an 

 outer surface measuring 8 mm. in diameter. It is intercalated 

 between supraoccipital, paroccipital, mastoid, and squamosal. 



It has already been mentioned that the squamosal constitutes 

 the lateral margin of the occipital surface. This bone forms a 

 strongly projecting edge posteriorly, which extends downward 

 and forward in an even curve to the base of the zygomatic 

 process, thus making a posterior termination and a broad floor to 

 the temporal groove, which is roofed over by the horns. There is 

 accordingly only an (in the bull, narrow) opening posteriorly in 

 an oblique upward direction over the parietal zone. Eiitimeyer ' 

 seems to lay some weight on this opening as a difference from the 

 Oxen and a resemblance to the Sheep. But, compared with the 

 condition found in the Italian Buffalo, there is not much difference 

 in this respect, and in nearly all Antelopes " die Schlafengrube 

 tiffnet sich . . . auch nach oben." It is consequently only the most 

 specialized members of Bos in which " die Parietalzone seitlich die 

 Schlafe iiberdacht," as the same author in his first paper rightly 

 puts it. Later Eiitimeyer, like some other authors 2 , seems only 

 to think of two possibilities, L e. " Is Ovibos a Sheep or an Ox " ? 

 and then every aberration in structure from the specialized 

 type is regarded as a similarity to the ovine one, even if it is a 

 feature common to most ruminants. 



The articulating surface for the condyles of the mandible is 

 very broad (see tig. 8, p. 709) and, to judge from my material, more 

 convex in the cow than in the bull, in which it is almost flat. 

 There is a broad and strong processus postglenoideus. 



So far as my material allows a judgment, there are always two 

 foramina temporalia in the Musk-ox, but only one in Sheep or Goats. 

 This is, however, a less important and variable characteristic \ 



The great development of the orbital tube is one of the most 

 conspicuous features of the Musk-ox skull, as has also been men- 

 tioned by previous authors. [It is formed by the frontal to, roughly 

 speaking, an extent of a little more than two-fifths (more exactly 

 S-) of the posterior and upper portion, by the lachrymal to one- 



1 ' Die Riuder der Tertiar-Epoche.' 



2 Boyd Dawkins, for instance. 



3 Nemorhadw. Cepluduphus, Bos tauru.% &c. seein to have two ; Antilopc, 

 Saiga, Gazella, Rupicapra, Bos hnhxlis, &c. only one. 



This is mentioned here only because Riitimeyer says (Rind. Tert. p. 104) : 



" Im iibrigen folgt der Schadelbau (viz. of Ouihos) demjenigen von 



Schafen bis in kleine Details, wie etwa Grestalt von Gefass uud Nervenrinnen." 



