AND A DENTAL NOTATION. 
483 
The grinder, which is the subject of figs. 2 and 3, tab. xix,, is the last molar from 
the right side, lower jaw, of the Phac. yp^liani, of the natural size. 
To determine whether any successional teeth were developed above or beneath the 
fangs of pre-existing teeth destined to be displaced by such development, in other 
words, whether a true deciduous series and a premolar series of teeth existed in the 
Wart-Hogs, required an examination of the jaws of an individual younger than the 
youngest specimen examined and figured by Home. 
The subject of Plate XXXHI. fig. 1 of the present communication is of the required 
immaturity, and, with the other specimens to be described, supplies those links in 
the series which were wanting for the explanation of the entire course of the truly 
remarkable dentition of the genus Phacochoerus. 
Fig. 1 shows a side view of the teeth in the young Phac, jplliani ; the grinding 
surface of the molar teeth in use is given, from the upper jaw in fig. 2, and from the 
under jaw in fig. 3. These teeth include all the milk-molars which are developed, 
together with the first permanent true molar. The milk-molars are 3 — 3 in number 
in the upper jaw, and 2—2 in the lower jaw. The first true molar, m 1, is also fully 
developed and in use in both jaws. The summit of the second true molar {ni 2) is 
just appearing above the socket. 
The length of the skull exhibiting this instructive phase of dentition is 10 inches. 
The milk -molars answer to the teeth of the typical dentition symbolized by f/2, c?3, 
and c? 4 in the upper jaw, and to c?3 and c?4 in the lower jaw. 
The first is implanted by two fangs, the second by three, the third by four fangs ; 
the shape of these teeth is sufficiently illustrated by the figures. 
Their rate of increase in size from the first to the last is considerable, yet not equal 
to that manifested in the true molars. Upon examining the substance of the jaws 
above the deciduous molars of the upper jaw and beneath those of the lower jaw, two 
formative alveoli and the trace of a third were detected in the upper jaw, one above 
d 4, containing the crown of a premolar ; the other above d 3, and the rudimental 
cell above d 2. The matrix, which the latter might have contained, had not begun 
to be calcified. A small formative socket was found beneath the last milk-molar of 
the lower jaw containing the crown of a premolar. The gubernacular canal from 
this socket opened between the fangs on the inner side of the milk-tooth. A second 
still smaller socket of an anterior premolar was beneath the interspace between the 
two milk-molars. 
The true nature of the molar behind the milk-teeth in both jaws was plainly shown 
by its long fangs extending beyond the parallel of the formative sockets of the suc- 
cessors of the milk-teeth, and widely open at their ends : this tooth has no vertical 
successor and is the first true molar, m 1. Only the crown of the second true molar 
{m 2) is formed at the stage here described ; and a few detached columns of the still 
larger and more complex third molar (m 3) were all that were calcified in its com- 
mencing formative alveolus. 
3 Q 2 
