RHINOCEROS TICHORHINUS. 309 
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 Harth, 4to, 1785, as the “ Fossil 
animal incognitum bone from Thame,” and which he notices 
Uh Pe 
