OCR Text |
Show 706 DR. E. LONNBERG ON THE [June 19, share in the formation of the orbital tube, makes this pit look deeper than it really is. If the bone were straight this pit would be rather shallow. The shape of the lachrymal bone is different from that of the Sheep. It is broader and decidedly widened in front, where its breadth is about a ninth of the cranial length ; whereas the lachrymal bones of the Sheep usually are narrowed in front or at most linear. The suture between the lachrymal and the nasal bones is quite variable in length in the different specimens of Musk-ox. In my material this variation is from 25 to 5 m m . Bichardson (I. c.) has treated of this as well as of the shape of the nasals. He has also observed that tbe nasals of the Musk-ox differ from those of the Sheep as well as from those of the Oxen. But it is evident that no characteristics of systematic value can be obtained from such variable bones as these. It may, however, be mentioned that a flat and broad nasal region, about \ of the basal length of the skull, is a feature common not only to Ovibos and the Caprina but also to a great number of Antelopes, when compared with the Bovina, in which the nasal region is more or less compressed to a ridge and thus narrow-ed to about \ of the cranial length. The great thickness of the nasals is in concordance with other bones of the Musk-ox skull, as may be seen from fig. 5 (p. 697). The intermaxillaries do not reach the nasals. Their proximal portion is curved outwards a little, but the distal parts are rather strongly convergent, and through this the distal portion of tbe upper jaw becomes comparatively more narrow even than in the Sheep. In consequence of this, and because the intermaxillaries are thickened in the middle, the anterior part of the skull gets a characteristic aspect not seen in other Cavicornia. In Sheep as well as in Oxen the posterior extension of the intermaxillaries is subjected to variation. It is, however, perhaps worth mentioning for comparison, that in none of the genera Budorcas, Nemorhcedus. Haploceros, and Rupicapra do the intermaxillaries reach the nasals. It might be that the shortness of the intermaxillaries stands in relation to the Musk-ox's way of browsing with its thick lip instead of biting. The Beindeer, which has thick lips, has a short intermaxillary not reaching the nasal; but Cervus dama, for instance, with thin lips has a long suture between the intermaxillary and the nasal. There seems accordingly to be a certain correspondence or parallelism between the Beindeer and the Musk-ox, which is also visible in the shape of the thick and anteriorly pointed intermaxillaries. The foramina incisiva of the Musk-ox are very large and posteriorly narrowed. Ovibos resembles in this respect the Sheep, but also Nemorhcedus. These foramina do not offer any important characteristics. The palatal surface is concave and rather strongly constricted behind the foramina incisiva (fig. 7, p. 707), much more than in Bos taurus, but much less than in B. bubalis. The palatines are larger comparatively than in the Sheep. The suture between palatines |