154 •S'/r Everard Home on the milk tusks , 
up the socket, and consequently retained there. This is a 
curious additional fact, and is so far an approach to rumi- 
nating animals, whose incisors are only in the lower jaw. 
These incisors enable the young dugong to crop the tender 
plants, but are no longer wanted when the animal grows up. 
EXPLANATION OF THE PLATES. 
Plate XII. 
This plate consists of three figures. 
Fig. 1. A side view of the first skull of the dugong, sent 
by Sir T. S. Raffles, in which the organ of hearing is in 
its place, and one of the tusks exposed through its whole 
length. 
Fig. 2. The longitudinal section of the tusk. 
These two figures are in the proportion of half an inch to 
one inch. 
Fig. 3. An exact copy taken from Mr. Cuvier's represen- 
tation of the dugong's skull, the proportions of which are not 
mentioned. 
Plate XIII. 
This plate consists of three figures, in the proportion of 
half an inch to one inch. The first represents the basis of 
the skull of the dugong with milk tusks ; the second, the 
appearance of the permanent tusks in situ ; the third, the 
section of the permanent tusk. 
Plate XIV. 
This plate consists of four figures. 
Fig. 1. The lower jaw of the skull represented in PI. xnr. 
