|e DESCRIPTION OF THE SIVATIIERIUM, 



two at once suggests the question, " had the Sivatherium also two additional 

 horns on the vertex ?" Tiie cranium in the fossil is mutilated across at the 

 vertex, so as to deprive us of direct evidence on the point, but the following 

 reasons render the supposition at least probable : 



1st. — As above stated, in the bi-cavicorned Ruminantia the osseous cores 

 are placed more or less to the rear of the orbits. 



2d. — In such known species as have four horns, the supplementary 

 pair is between the orbits, and the normal pair well back upon the frontal. 



3d. — In the Bovine section of Ruminantia, the frontal is contracted 

 behind the orbits, and upwards from the contraction it is expanded again 

 into two swellings at the lateral angles of the vertex which run into the 

 bases of the osseous cores of the horns. This conformation does not exist 

 in such of the Ruminantia as want horns or as have them approximated on 

 the brow. It is present in the Sivatherium. 



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

 ture in the fossil : and if they were a solitary pair on the head, the struc- 

 ture, from their position, would perhaps be more singular, than if there 

 had been two additional horns behind. 



ca„ 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 unin- 

 terrupted series, the interval from the first molar to the anterior border 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 Rumi- 

 nantia such as the Camelidte, Avhere 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 mar- 

 gin 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 



