RHINOCEROS TICHORHINUS. 339 



crescents are still distinct in the anterior tooth, whilst in 

 that which follows, they are blended by a continuous tract 

 of dentine. This difference arises from the circumstance 

 that the first true molar comes into place immediately 

 behind the deciduous series of four teeth, before these are 

 shed and succeeded by the four premolars shown in fig. 

 128 ; it thus assists in performing the essential work of 

 mastication whilst the change of dentition is going on, 

 and is, consequently, worn down to some extent before the 

 fourth premolar has risen into place. 



The first premolar in the Rhinoceros tichorhinus has a 

 compressed conical crown, the anterior half simple and 

 subtrenchant, the posterior half broader, and impressed by 

 a vertical pit : it is supported by two connate fangs, im- 

 planted in a simple alveolus ; the antero-posterior extent 

 of the crown is between seven and eight lines, the height 

 of the enamelled part is half an inch : the socket is on the 

 same transverse line as the posterior border of the symphy- 

 sis. The form and size of the three succeeding molars may 

 be judged of from the figures in cuts 123, 124, and 128. 

 In the last specimen, the longitudinal extent of the series 

 of four premolars is four inches nine lines. The first pre- 

 molar appears to be shed, in the Rhinoceros tichorhinus, 

 before the last true molar rises completely into place. 



Similar evidence of the true number of the molar series 

 in the lower jaw of the Rhinoceros tichorhinus, is given by 

 another British specimen, to which historical interest is 

 attached, both from its early introduction to the notice of 

 Geologists, and on account of the opinion respecting it 

 which Cuvier has left on record. The specimen in ques- 

 tion is that which Douglas has figured in his ' Dissertation 

 on the Antiquity of the Earth, 1 4to, 1785, as the " Fossil 



animal incognitum bone from Thame, 1 ' and which he notices 



z 2 



