306 Zoological Society :— 
In the younger specimen the edge of the palate has a slight pro- 
minence in the middle of each side ; but this is evidently an acci- 
dental deformity, as the prominences are not of the same size in the 
two sides. In the adult skull the two sides of the palate are evenly 
arched out. 
The lower jaw most resembles that of the restricted genus Phoca 
(of which P. barbata is the type) in being solid and strong, and in 
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Fig. 1. Skull of Halicyon Richardii. 
2. End of lower jaw of Phoca barbata, to show the dilatations and inflexions 
of the lobe over the angle. 
3. End of the lower jaw of Pagomys fetidus. The end of the jaw of Callo- 
cephalus vitulinus is somewhat similar. ; 
4. Lower edge of the lower jaw of Halicyon Richardii. 
3d. Lower edge of the lower jaw of Phoca barbata. 
6. Lower edge of the lower jaw of Pagophilus grenlandicus. The jaw of 
Pagomys fetidus is somewhat similar, but much smaller. 
