b 



SIVATHERIUM GIGANTEUM. 259 



In most of the horned rnminantia, the incisives run np 

 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 inci- 

 sives. In the Camel, the apophyses 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 ua the homed rumi- 

 nants, nor in the Camel and its congeners, do the bones of 

 the nose rise out of the plane of the brow with any remark- 

 able 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, riinning between the upper 

 borders of the maxillaries, and joined to the ascending pro- 

 cess 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 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 roiinded angle of 

 about 130 degrees, an amount of saliency without example 

 among ruminants, and exceedmg what holds in the Rhino- 

 ceros, Tapir, and Palseotherium, the only herbivorous animals 

 with this sort of structure. Instead of being in nearly 

 parallel slips, they are broad and well arched at their base, 

 and converge rapidly to a sharp tip which is hooked down- 

 wards, over-arching the external nostrils. Along a consider- 

 able portion of their length they are unconnected with the 

 adjoining bones, their lower margins being free and so wide 

 apart from the maxillaries as to leave a gap or sinus of 

 considerable length and depth in the bony parietes of the 

 nostrils. The exact extent to which they are free is un- 

 luckily not shovm in the fossU, as the anterior margin of the 

 maxillaries is mutilated on both sides, and the connection 

 with the incisives destroyed. But as the nasal bones shoot 

 forward beyond the mutilated edge of the maxillaries, this 

 circumstance, together with their well-defined outline and 

 symmetry on both sides of the fossil, and their rapid converg- 

 ence to a point with some convexity, leaves not a doubt that 

 they were free to a great extent, and unconnected with the 

 incisives. 



INow to determine the conditions of the fleshy parts, which 

 the structure in the bony parietes of the nostrils entails. 



The analogies are to be sought for in the Euminantia and 

 Pachydermata. 



s 2 



