402 
Fig. 160. 
Structure of ivory of Hippopo- 
tamus tusk in transverse sec- 
tion. 
HIPPOPOTAMUS. 
inferior tusk of the Mastodon by 
its partial investment of enamel, 
—or when this is lost, as in the 
decayed specimen from the till at 
Walton, by the fine concentric 
lines on the fractured surface of 
the ivory (fig. 160), the corre- 
sponding surface in the tusk of 
Mastodon presenting the decussating curvilinear strie as 
End of lower tusk of Fossil Hippopota- 
mus, $ nat. size. Walton, 
shown in fig. l0l¢. The se- 
cond specimen from Walton 
is thus described by Mr. 
Parkinson :—“ The point of 
an inferior canine tooth or 
tusk, measuring full nine 
inches in circumference, and 
having seven inches in length 
of triturating surface (fig. 
ko): 
of this tooth, it is very likely 
From the great size 
to have belonged to the same 
animal to which the preced- 
Be- 
sides the longitudinal stric 
ing tooth belonged. 
and grooves observable in 
the enamel of its sides and 
inferior part, it is charac- 
terised by strong transverse 
rugous markings, which are placed at nearly regular dis- 
tances of about two inches, and are observed to exist in 
the same manner on the fragment which joins to it.” * 
* © Organic Remains,’ vol. iii., p. 375. 
In pl. xxi., fig. 1., there is a good 
figure of the penultimate molar of the lower jaw of the fossil Hippopotamus from 
Walton. 
