IS36.J a new Fossil Genus of the Sivdltk' range* 227 : 



again into two swellings, at the lateral angles of the vertex, which 

 run into the bases of the osseous cores of the horns. This conforma- 

 tion does not exist in such of the Ruminantia as want horns, or as 

 have them approximated on the brow. It is present in the Sivathe* 

 num. 



On either supposition, the intra-orbitary horns are a remarkable 

 feature in the fossil : and if they were a solitary pair on the head, the 

 structure, from their position, would perhaps be more singular 

 than if there had been two additional horns behind. 



Now to estimate the length of the deficient portion of the muzzle^ 

 and the entire length of the head :• — 



■ In most- of the Ruminantia, where the molars are in a contiguous un? 

 interrupted series, the interval from the first molar to the anterior bor- 

 der of the incisive bones is nearly equal to the space occupied by the 

 molars ; in some greater, in some a little less, and generally the latter. 

 In other Ruminantia, such as the Camelidae, where the anterior molars 

 are insymmetrical with the others, and separated from them by being 

 placed in the middle of the diasteme, this ratio does not hold; the 

 space from the first molar to the margin of the incisives being less than 

 the line of molars. In the Sivatherium, the molars are in a contiguous 

 series, and if on this analogy we deduce the length of the muzzle, we get 

 nearly 10 inches for the space from the first molar to the point of the 

 incisives ; and 28.85 inches for the whole length of the head, from the 

 border of the occipital foramen to the margin of the incisives ; these 

 dimensions may be a little excessive, but we believe them not to be far 

 out as the muzzle would still be short for the width of the face, in a 

 ruminant.. 



The orbits next come to be considered. The- size and position of the 

 eye form a distinguishing feature between- the Ruminantia and the 

 Pachydermata. In the former, it is large and full, in the latter, small- 

 er and sunken ; and the expression of the face is more heavy in con- 

 sequence. In the Sivatherium the horbit is considerably smaller in 

 proportion to the size of the head than in existing ruminants. It is 

 also placed more forward in the face, and lower under the level of the 

 brow. The rim is not raised and prominent, as in the Ruminantia, and 

 the plane of it is oblique ; the interval between the orbits at their up- 

 per margin being 12.2 inches, and at the lower, 16.2 inches. The lon- 

 gitudinal diameter exceeds the vertical in the ratio of 5 to 4 nearly, 

 the long axis being nearly in a line from the naso mixillary sinus 

 across the hind limb of the zygomatic circle. From the above we in- 

 | fer that the eye was smaller and less prominent than in existing rumi- 

 nants : and that the impression of the face was heavier and more igno- 

 ble, although less so than in the Pachydermata, excepting the horse-j 

 also that the direction of vision was considerably forwards, as well as 

 lateral, and that it was cut olf towards the rear. 



