436 ON THE FOSSIL BOXES OF PACHYDERMATOUS QUADRUPEDS. 



in the one-horned, is quadrangular, and is a little more broad than high 

 in the two-horned. 



The occipital foramen is also more broad than high, whilst in the 

 one-horned it has the contrary proportions. 



The principal differences of the lower jaws are, besides the length 

 of the part preceding the molars, which is much less in the two-horned 

 than in the one-horned — 1 st. that the rows of molars is longer in the 

 two-horned ; 2nd. that the ascending rami are much less high ; 3rd. 

 that the coronoid processes are much less long, less acute, and less di- 

 rected forwards; 4th. that the dental branches are much more protu- 

 berant externally. 



The upper molars of the adult two-horned rhinoceros (plate 56, 

 fig. 1), taken separately, are greater than those of the two one- horned, 

 and may be distinguished from them, because their posterior edge being 

 less raised, the fissure of this edge is not changed into a fossette, as 

 in the two one-horned species, but remains a real fissure, at least till 

 the tooth is worn to the height of the neck. Besides, the hook of the 

 posterior eminence remains distinct from the anterior eminence later 

 than in the one-horned, so that there is not observed, at least in the 

 animals which I have seen, any of those hollows which are preserved 

 at a eertain age in the upper molars of the one-horned. 



However, this remark does not apply to the milk teeth of the two- 

 horned, which I observed in our young head of the Cape, and which 

 are seen, plate 40, fig. 1, B, C, D, and E. We there distinctly see 

 the fossette detached from the anterior hollow, and at the second, D, 

 we perceive that the posterior fissure commences to become hollowed. 



These four teeth have also this character — of being all of them more 

 long than broad. They afford us the indication that in the other rhi- 

 noceroses, whose milk teeth we have not seen, the proportions will ' 

 probably be the same, as well as the greatest complication, which, as 

 •we have already said, is a sufficiently general rule for herbivorous 

 animals, and perhaps for all animals. 



We give, plate 56, fig. 3, a germ of a fifth molar tooth, that is, of a 

 first back tooth, extracted from this young head of a two-horned, and 

 the same as that marked A, plate 40, fig. 1, to the end, that we may 

 be able to see the eminences and their hooks in their perfect state. 

 It is precisely this germ which becomes the tooth C of fig. 1, plate 56. 



The Scapula of the tAvo-horned is broader above, because its superior 

 angle is more forward, and the posterior is not truncated obliquely. 

 The salient angle of the spine is placed in it a little lower than in the 

 one-horned, and this angle is more obtuse. 



The Humerus has not the deltoid ridge so long nor so prominent 

 below, nor the posterior angle of the great tuberosity so raised, nor 

 the anterior angle curved before the canal of the biceps, nor the lower 

 head, and particularly its pulley, so broad transversely, nor so oblique. 

 On the whole, however, this bone is not thinner than in the one- 

 horned. Its most obvious difference is the want of a pulley on the 

 part of the external tuberosity before the canal of the biceps. 



I find the olecranon perceptibly shorter in proportion in the two- 

 horned ; the ulna thinner, and the radius a little less broad above as 

 well as below. The proportion of this part is also a little different 



