302 
from that of the typical Sus in the entire absence of the fourth pree- 
molar from each jaw. The great contraction of the lower jaw at the 
symphysis between the canines and the premolars is likewise re- 
markable. The whole skull of Potamocherus is shorter in propor- 
tion to its length than that of Sus, and more Hippopotamoid. The 
premaxillary bones are more expanded. The basis cranii is altogether 
shorter, so that the pterygoids (which are stronger) nearly reach the 
tympanics, whereas in Sus indicus they are more than half an inch 
apart. The most noticeable character, however, in the skull of Po- 
tamocherus is the great width and strength of the zygomatic arch 
which (as may be seen by the accompanying woodcuts), turns out 
suddenly at its anterior part at right angles from the line of the 
face, and attains its greatest breadth at once, anteriorly to orbits. 
In Sus, on the other hand, it slopes gradually outwards, and reaches 
its greatest width at the junction of the squamose with the malar. 
The orbits are proportionately smaller in Potamocherus ; and the 
malar bones are of remarkable size and strength. Looking at the 
occiputs, the supra-occipital is wider than in Sus, and more strongly 
ridged. 
At the middle of the nasal bones in Potamocherus, a rough out- 
standing ridge projects widely on each side to support the large 
warty protuberances which adorn the face of the living animal. 
This ridge is about 2 inches in length, gradually lessening towards 
the snout, and projects so far as nearly to meet the rough termina- 
tion of the posterior development of the tusk-process of maxillary, 
and forms with it a channel for the passage of the orbital nerves and 
vessels. 
Such are some of the leading peculiarities in the skull of this 
animal which seem fully to justify its separation as a generic or 
subgeneric form from Sus. It is probable that the Southern River- 
Hog (Potamocherus africanus) possesses the same differential 
characters, and that the isolation of these two species in structural 
characters will thus be found to correspond with their geographical 
position as inhabitants of a distinct zoological region from that 
tenanted by Sus. 
June 12th, 1860. 
Dr. J. E. Gray, V.P., in the Chair. 
Dr. A. Giinther exhibited a dried specimen of a fish of the genus 
Centrolophus, obtained by Mr. J. Couch at Polperro, Cornwall. It 
had been named by Mr. Couch Centrolophus morio, but Dr. Gin- 
ther regarded it as of a new and distinct species, and proposed to 
call it C. britannicus. 
