636 PROF. FLOWER ON A TWO-HORNED RHINOCEROS. [Julie 4, 



other skulls, the difference between the narrowest and widest being 

 almost as great as that between the latter and the present skull, yet 

 there are intermediate gradations in the former case, whereas the 

 Tipperah skull is completely isolated from the others. It is curious 

 that the skull which comes next to it in width is that of the small 

 dark-coloured animal from Malacca, which died in the Society's me- 

 nagerie in 1872, and of which the external characters were certainly 

 quite unlike those of R. lasiotis. 



A second peculiarity by which this skull is distinguished from all 

 the others, and one to which I am inclined to attach still more im- 

 portance, is the greater size of the teeth, especially the premolars, both 

 absolutely and relatively. This is also seen in the Table, in which is 

 given the absolute length of the series of molars and premolars, ex- 

 cluding the first and last, which are either absent or not developed 

 in many of the specimens under consideration, and including, there- 

 fore, the three posterior premolars and the two anterior molars. In 

 the case of the younger skulls, milk-molars occupy the place of pre- 

 molars ; but this probably does not materially affect the length of 

 the series. It will be seen that in the present skull this length ab- 

 solutely exceeds that of any of the others, and, relatively to the 

 length of the skull (taken as 100), it is 400, whereas, of the other 

 seven, five range between 314 and 33 - 3, and the other two, which 

 give a higher figure, are both young animals, in which the skull 

 had not attained its full dimensions, and the teeth therefore appear 

 relatively larger than they otherwise would have been. It is pro- 

 bable that sex may affect the size of the teeth, as in the two known 

 females (Nos. 2 and 3 of the list) they are smaller than in any of 

 the others. Not only in antero-posterior diameter are the premolars 

 larger in the present specimen, but still more notably in breadth. 

 Thus the last premolar in the Pegu adult skull (No. 4) is 1" # 8 in 

 greatest breadth, in the Sumatran female (No. 3) 1"85, in the Ma- 

 laccan skull (No. 2) 1""9, in the Sumatran male (No. 5) 2"*05, in the 

 present skull 2""2. The lower molars exhibit the same superiority 

 of size ; but in other respects the dentition does not differ appreci- 

 ably from that of the various specimens of R. sumatrensis. 



As an individual peculiarity may be noted the single lachrymal 

 foramen on each side, whereas many of the others have two ; but in 

 both the Malacca and one of the other British-Museum skulls, the 

 foramen is also single on both sides, and in the Pegu and one of the 

 Sumatran specimens it is single on one and double on the other side. 

 Again, the great amount of ossification in the base of the pterygoid 

 fossa, at the posterior end of the vomer, forming a sort of " para- 

 sphenoid " mass, is worthy of note ; but it is repeated in the Pegu 

 skull, and partially in the old Sumatran specimen (No. 2), though 

 not in the equally aged Malacca female. 



I have pointed out the peculiarities of this skull, which are in- 

 teresting in connexion with the fact that it was obtained from a 

 locality quite beyond the hitherto known range of the Sumatran 

 Rhinoceros ; but, in the absence of other evidence, will not attempt 

 to decide whether they should be considered of specific value. 



