488 PROFESSOR OWEN ON THE DENTITION OF PHACOCHGERUS, 
also being central, and the islands smaller and more regularly disposed. This tooth 
extends to within one or two lines of the thin compact inferior bony wall of the deep 
ramus of the jaw, where the constituent columns terminate in the basal openings of as 
many pulp-cavities, with the exception of the first four, which are blended together, 
and from wliich no root has begun to be developed. It is therefore plain that this 
large and singularly complex grinder will continue to serve the purposes of mastica- 
tion long after the shedding of the molar in advance, and the substance of which is 
already wasting away by the pressure of the larger tooth. We shall see, in the next 
specimen, that that molar is actually worn away and shed, whilst the smaller grinder 
in advance of it remains. 
In the lower jaw of the specimen (No. 775 A.), the gum has grown over the sockets 
of the second true molar between the persistent remnant of the fourth premolar and 
the third true molar. In the upper jaw the last remnant of the second true molar 
remains on the right side, the crown having been worn to its base and the fangs 
absorbed. 
Thus, in ih^ Phac. Pallasil, as in the Phac. JPHiani, the last of the premolar series, 
like the last of the true molar series, is distinguished by its longevity, although infe- 
rior in this respect to the large true grinder which continues to do the work of mas- 
tication to the end of the animal’s existence. 
The analogy of the Phacocheres to the Elephants in the superior size, complexity, 
and duration of the last grinders is close and interesting ; but it does not extend to 
the horizontal mode of succession, in other words to the absence of premolars or 
vertical successors of deciduous teeth, as Home led Cuvier to believe. In the deve- 
lopment and succession of these premolars, and in the shape, proportions and posi- 
tion of the true deciduous teeth, the Wart-Hogs much more closely and essentially 
agree with the rest of the Suidce. They differ, however, as we have seen, in the infe- 
rior number of both milk-molars and premolars which are developed, and in the 
speedier loss of all the true molars in advance of the last large one ; but, in the order 
of shedding of those teeth, more especially in the very early displacement of the first 
true molar, and the total obliteration of its place in the series by the approximation 
of the last premolar to the second true molar, and in the subsequent displacement of 
this tooth with the approximation of the last premolar to the last true molar, the 
genus Phacochosrus is quite peculiar and different from all other Mammalia. 
The author, who first called the attention of naturalists to the peculiarities of the 
dentition of the Phacochoein, has indicated another difference between the Wart-Hog 
and the common Hog, by affirming that the latter has a molar tooth developed 
behind the third true molar, at least in the lower jaw ; which, if it were so, would 
have shown the common Hog to differ, also, from almost every other placental 
mammal with two sets of teeth In the description of Plate XX. of the Philoso- 
* The Megalotis Lalandii is the only example, as far as I have observed, of the constant occurrence of four 
true molars on each side the lower jaw : the typical number three being retained above. 
