G PLEISTOCENE MAMMALIA. 



occipito-parietal suture between them remaining unobliterated, 1 which two characters are 

 never seen in the adult Bos, Bubalus, or Bison. The share which the mastoids take ia 

 the formation of the occiput is much smaller than in any of those three animals, and hence 

 its greater height in proportion to its width. In Bubalus Caffer the width reaches a maxi- 

 mum. The occipital crest is much more strongly marked in Ovibos, Caprn, and Ovis, than 

 in any of the three animals so frequently quoted. 



Coronal Surface. — We have now to discuss the most important portion of the skull, 

 the coronal surface, which in the old male (PI. Ill) is almost concealed by the large spongy 

 bases of the horncores. In the young animal, 2 in common with all the cavicorn ruminants, 

 the Gnu and Giraffe excepted, they are supported by the frontals, while in the old male 

 they extend far back over the parietals, and project over the occipital surface. In the 

 Giraffe the paired horncores are situated on the parieto-frontal suture ; in the old male 

 Gnu they extend over the suture, as in Ovibos. Each horncore in the last animal is separated 

 from its fellow by a diastema in the median line, varying in width according to sex and 

 age, the diastema being smallest in the old male (PI. Ill), and largest ( ih the young 

 female (PI. IV, fig. 1). Each {g) is raised above the coronal surface, in the adult 

 (PI. Ill) male at least 0*8 inch; thence it passes horizontally outwards, decreasing in size 

 as far as a line passing in front of the orbit, where it turns suddenly downwards at a right 

 angle, and ends in a stout obtuse point that extends further down than the tips of the 

 paramastoid process. The fossil skull figured is an admirable example of this (PI. III). 

 In the female (PI. Ill) the horncores are much smaller and more cylindrical than in the 

 adult males, and they are supported by the frontal bone, as in the female Gnu. 



The structure of the horncores affords a character of very great importance in the deter- 

 mination of the affinities of the animal. The section made of the horncore in the College 

 of Surgeons (3817) proves that it consists of a compact spongy mass, solid for at least an 

 eighth of its length, and with a simple vacuity merely at its base. That this character is 

 constant is proved by the section of the fossil horncore from Crayford, as well as by the 

 observations of M. Lartet. 3 In Bos, Bison, and Bubalus, the frontal sinuses are prolonged 

 as far as the end of the horncores, 4 while in Ovis and Capra they are never pro- 

 longed further than the middle, and very frequently they do not enter the horncores at all, 

 as in some of the Antelopes. In the compactness, then, of its horncores, as M. Lartet has 

 observed, Ovibos moschatus is allied to Ovis, while in their position on the parietal in the 

 old male it stands apart from all these genera. Among the points of difference between 



1 See 'Manuscript Cat. of Osteological Series in the University Museum, Oxford.' I have to thank 

 Professor Rolleston, F.R.S., for calling my attention to this character. 



2 ' See • Zoology of Herald, ' pi. iv. 



3 Op. cit. 



4 I have, however, seen two horncores of Bison jiriscus which are solid for a distance of at least six 

 inches from their tips. They are altogether exceptional in character, and may have heen diseased. 



