30 EINAU LÖNNBERG, STUDIES ON KUMINANTS. 



The only representutivc of tlie Ovibovirue hiis, as is wellkriowii, vevy strong liorns, 

 the development of wliich tlie |)i'esent author has described in another i)apei'. ') When 

 the horn is fully devcloped, it presents tlie following characteristics. The horns ;ire 

 attached to the sknll with very broad and expa.nded bases which in the hull almost 

 nieet each other in the median line. From the ])lace of insertion tliey eurve downward 

 and somewhat forward for about half their length. The distal ])art is then again curved 

 upward in the same vertieal plane as the downward eurve. They represent thus very 

 powerful hooks. Most of the strength of these organs lies in the horny sheath which is 

 here comparatively more strong!}' developed than in any other meinber of Cavicornia. 

 The whole distal part of the horn of the muskox, from the end of the downward eurve 

 cousists of solid horn. The core is thus cjuite short and directed nearly straight down- 

 wards at the side of the head.") The horny sheath can thus be said to have an outer 

 and an iinier or proximal side which is the more |)ronounced as this part of the hoi-n is 

 eonsiderably tiattened. The thickness of the pi"oximal side of the horny sheath measures 

 7 — 9 mm. in section and should thus in another animal l)e regardcd as rather thick. It 

 is however much thinner than the wall of the outer side which is 18 — 30 mm. in seetion. 

 — These measurenients may of conrse vary in difterent specimens, but are recorded for 

 the sake of comparison. — The part of the horny slieath which ca] is the skull is still 

 thicker, measnring 60 — 70 mm. or more in thickness. This part is exceedingiy strongly 

 tixed to the skull, which is iieeded on account of the downward direction of the horn- 

 core. — As it is now, every weight on the hooked tip of the horn tends to puU the 

 horny sheath of the core, but this cannot hapjjen for the clinching of tlie l)a-sal horny 

 mäss to the skull. This is effected and strengthened by means of strong warty pro- 

 minences, which extend from the interiör surface of the base of the sheath and tit into 

 pits and holes in the bony mäss of the skull. The bony core, too, shows on its surface 

 grooves ;ind holes to which ridges axid prominences of the sheath correspond. Into the 

 base of the core air sinuses extend. There is, not only one sinus, as in the hitherto 

 described forms, but several small ones separated from each othei' by walls of eompact 

 bony tissue as thick as the width of the siruises themselves. The base is thus very 

 strongly built. The compacta of this basal region extends distally, incasing the central 

 spongiosa, but it is much stronger and more absolutely eompact on the side nearest to 

 the skull. The cause of this difference in thickness on different sides of the core may 

 pai'tly be due to the mode of development of this organ, partly to the fact that the horny 

 sheath is thiinier on the proximal side as is already stated. Thus a thick compacta of 

 the core corresponds to a thin horny layer and the contrary. This is an analogy to what 

 already has been stated alxive with regard to the horns of othei" species. The central 

 spongiosa of the core of <_>viho.^ presents the aspect of ^vell develo])ed systems of Culmann's 

 trajectories (conf. tig. 9 Pl. I). They are arr;inged so as to ^vithstand a forcc working 

 vertically against the main axis of the core (conf. the hg. 9). Basally they are not 

 visible and the spongiosa is there more dense. Especially towards the tip, however, the 



1) Ou the structure iiiul auatomy of the Muskox (OvibcDs inoschaius), t'roc. Zool. Soc. ]jOiidoii lOOo, 

 ^) About its direction in earlier stages see the paper (juotcd. 



