280 PROBOSCIDIA. 
pair of mastoid eminences: besides the injury to the crown 
from accidental violence, all the fangs of the tooth have 
been broken away. 
The molar tooth (fig. 98) of the Mastodon angustidens, 
which was obtained by Mr. Robert Fitch, F.G.S. of Nor- 
wich, from the fluvio-marine crag at Thorpe, near that city, 
strikingly demonstrates the generic differential characters 
Fig. 98. 
Penultimate upper Molar, Mastodon angustidens, Fluvio-marine Crag, Thorpe, 
Norfolk. 4 nat. size. 
between the molars of the Mastodon and those of the Mam- 
moth. The coat of enamel (¢), which invests the dentinal 
eminences (@) of the crown, is three times as thick as that 
in the Mammoth’s molar of thrice the size, which is figured 
at p. 231 (fig. 90) ; and it is almost twice as thick as the 
enamel of the molar tooth (fig. 88) of the African Ele- 
phant,—the existing species which makes the nearest ap- 
proach to the Mastodon in the structure of its teeth and 
in its general proportions. The cement of the Masto- 
don’s tooth, on the other hand, forms so thin a layer, 
that it can only be detected by the naked eye at the 
bottom of the clefts between the mastoid eminences. These 
are arranged subalternately in four pairs, and a tuberculate 
eminence terminates the base of the crown. This number 
of the chief divisions of the grinding surface, together with 
