1836.] 



a new Fossil Genus of the Sivdlik range. 



223 



Notwithstanding the singularly perfect condition of the head, for an 

 organic remain of such enormous size, we cannot but regret the muti- 

 lation at the muzzle and vertex, as it throws a doubt upon some very 

 interesting points of structure in the Sivatherium : 1st, the presence or 

 absence of incisive and canine teeth in the upper jaw, and their num- 

 ber and character if present ; 2nd, the number and extent of the bones 

 which enter into the basis of the external nostrils ; and 3rd, the pre- 

 sence or absence of two horns on the vertex, besides the two intra- 

 orbital ones. 



Regarding the first point, we have nothing sufficient to guide us with 

 certainty to a conclusion, as there are ruminants both with and without 

 incisives and canines in the upper jaw ; and the Sivatherium differs 

 most materially in structure from both sections. But there are two 

 conditions of analogy which render it probable that there were no in- 

 cisives. 1. In all ruminants which have the molars in a contiguous 

 and normal series, and which have horns on the brow, there are no in- 

 cisive teeth. In the camel and its congeners, where the anterior 

 molars is unsymmetrical and separated from the rest of the series by 

 an interval, incisives are present in the upper jaw. The Sivatherium 

 had horns, and its molars were in a contiguous series : it is therefore 

 probable that it had no incisives. Regarding the canines there is no 

 clue to a conjecture, as there are species in the same genus of rumi- 

 nants both with and without them. 2. The extent and connections of 

 the incisive bones are points of great interest, from the kind of deve- 

 lopement which they imply in the soft parts appended to them. 



In most of the horned ruminantia, the incisives run up by a narrow 

 apophysis along the anterior margins of the maxillary bones, and join 

 on to a portion of the sides of the nasals ; so that the bony basis of the 

 external nostrils is formed of but two pairs of bones, the nasals and the 

 incisives. In the camel, the apophysis of the incisives terminate upon 

 the maxillaries without reaching the nasals, and there are three pairs 

 of bones to the external nostrils, the nasals, maxillaries and incisives. 

 But neither in the horned ruminants, nor in the camel and its conge- 

 ners, do the bones of the nose rise out of the plane of the brow with 

 any remarkable degree of saliency, nor are their lower margins free 

 to any great extent towards the apex. They are long slips of bone, 

 with nearly parallel edges, running between the upper borders of the 

 maxillaries, and joined to the ascending process of the incisive bone, 

 near their extremity, or connected only with the maxillaries ; but in 

 neither case projecting so as to form any considerable re-entering 1 

 angle, or sinus, with these bones. 



In our fossil, the form and connections of the nasal bones, are very 

 different. Instead of running forward in the same plane with the brow, 

 they rise from it at a rounded angle of about 130°, an amount of sali- 



