708 dr. e. loxnberg ok the [June 19, 



masseterica in an adult bull passes about a centimetre from 

 the lower margin of the lachrymal boue and parallel with the 

 same, but then it descends rather steeply to a tuber maxillare 

 situated above the second true molar. This is constant in my 

 material except in one bull, in which the tuber maxillare is situated 

 on a vertical line drawn between the first and second true molars 

 (fig. 3, p. 691). But there seems to be still more variation in this 

 respect, because Eiitimeyer (I. c. p. 11) as well as Dawkins (I. c. 

 p. 7) assert that the tuber maxillare is to be found above " the 

 first true molar." It is apparent from these f:icts that the 

 situation of the tuber maxillare does not offer any valuable 

 characteristic for classification. 



The foramen infraorbitale opens rather far back, as Eiitimeyer 

 also remarks, above the third premolar or even first true molar. 

 This seems to be a singular feature among Cavicornia. In Sheep, 

 Goats, and Gazelles this foramen is situated above the second pre- 

 molar, and in other forms it is still more advanced. Budorcas 

 (including Nemorhatdus &c.) agrees with Ovibos in this respect, as 

 will be seen later. 



The mandible of Ovibos offers several points of interest. The 

 processus c^ronoideus is strongly curved backwards and more 

 pointed than is usual in other forms. It is also strikingly small, 

 which can be expressed by comparing its length with the length 

 of the mandible itself. The former measurement is in Ovibos about 

 16-17 per cent, of the latter, but in Sheep, Goats, and Gazelles about 

 24 per cent., in Rupicapra about 23 per cent,, &c. The small 

 Cavicornia seem as a rule to have their processus coronoideus more 

 straight, thin, and squarish at the end. In Bos the condition re- 

 sembles more that in Ovibos, with the length of processus coro- 

 noideus about 18-5-20 per cent, of the mandibular length. This 

 may, therefore, be regarded as a parallel development, the more 

 striking as the most specialized Bos taurus has a shorter and more 

 pointed coronoid than Bos bubalis. 



The articular surface of the mandible of the Musk-ox is 

 remarkable for its shape, because the longitudinal diameter is about 

 six tenths or more of the transverse one. In other ruminants the 

 transverse diameter is at least twice (sometimes nearly thrice) as 

 long as the longitudinal one. 



The symphijsismandibulce (fig. 8, p. 709) is about as long in Ovibos 

 as in Bos (16 per cent, of the mandibular length in the former and 

 14-17 per cent, in the latter) ; but it is, as Eichardson rightly 

 remarks (I. c. p. 70), " more vertical, and it forms an angle or chin." 

 The formation of such an angle or chin at the symphysis mandibulce 

 may be caused by the need to strengthen the symphysis in a 

 vertical direction, because the opening of the canalis inframaxillaris 

 is very wide and deeply excavated in the bone and thus weakens 

 the bone. The great width of this canal may be due to the con- 

 ditions under which the Musk-ox lives in the Arctic regions. It is 

 not only this foramen which is comparatively large in Ovibos, but 

 the foramina for blood-vessels are as a rule large. Eiitimeyer has. 



