PACHYDERMATA. 
In the Hippopotamus, the Rhinoceros, and 
the Tapir, the separation of the toes is more 
apparent externally, but still the phalanges, 
which are three in number to each of the four 
toes, are excessively strong and bulky when 
compared with their length. A kind of grada- 
tion is likewise to be traced through these 
genera, whereby the foot of the Elephant be- 
comes gradually transformed into the cloven 
hoof of the hog tribe, owing to the progressive 
diminution in size of the inner and outer toes, 
and the gradual conversion of the terminal 
pares of the central toes into that prismatic 
form which adapts them to fit the horny enve- 
lopes that encase them like shoes. 
Throughout all the hog genera the weight of 
the hody is entirely supported on the two cen- 
tral digits, the bones whereof are propor- 
tionally strong and well developed, while the 
phalanges of the inner and of the outer toe, 
which do not touch the ground, remain per- 
manently of very rudimentary size. 
Teeth—In no order of Mammiferous ani- 
mals do the teeth present so much diversity of 
Structure and irregularity of disposition as 
among the Pachydermatous races ; it will be 
therefore necessary, in adverting to this part of 
their economy, to describe the principal modifi- 
cations which the dental organs assume in 
different genera, before we proceed to investi- 
gate the manner of their formation ; and this we 
do more willingly, because from the character 
and arrangement of the teeth we can alone sa- 
tisfactorily determine what have been the habits 
of extinct genera, the list of which is already 
considerably more extensive than that of living 
forms. Professor Owen, to whose labours in 
this department science is already so deeply in- 
debted, has in his recent work on the Com- 
parative Anatomy of the Teeth* examined this 
part of our subject with all the minuteness re- 
quired for ‘geological researches, and from his 
tindness we are enabled to lay the following 
abstract before our readers. 
In the genus Sus, the wild progenitor of our 
domestic breeds of Hogs, Sus scrofa, the com- 
ete set consists of forty-four teeth, viz— 
Incisor. Canine. Premolar. Molar. 
é i i: | 4.4 333 
43:4 4.4 31:3 
In the wild Boar both the upper and lower 
nines curve forwards, outwards, and up- 
wards ; their sockets inclining in the same di- 
ection, and being strengthened above by a 
idge of bone which is sometimes extraordina- 
ily developed, these teeth become converted 
nto most formidable weapons. These teeth, 
hich have the character of true tusks, are 
ree-sided ; the broadest convex side being 
irected obliquely inwards and forwards, while 
ne outer and posterior sides are nearly flat; and 
ne hinder surface being destitute of any cover- 
ig of enamel; whilst the two other sides are 
cased with that material, the tusk wears ob- 
quely from behind upwards and forwards to 
point, while its posterior margins present 
* Odontography, Bailliere, 8vo. 1845. 
VOL. III. 
865 
enamel edges that\ are always sharp and tren- 
chant. Each of these tusks in the lower jaw 
* Fig. 477. 
of the German wild Boar will measure eight 
inches in length along its curve, and in the 
wild Boars of Assam they have been noticed 
measuring one foot, so that when wielded by 
such strong and brawny muscles as those of a 
Hog’s neck, it is easy to conceive that terrific 
wounds may be inflicted by such instruments. 
In the Baberoussa or “ Horned Hog” the 
developement of the canines is still more ex- 
traordinary. Those of the upper jaw seem as 
if their sockets had been pulled out or pro- 
duced from the alveolar border of the upper 
maxillary bone, and then abruptly bent up- 
wards, giving the tooth a direction upwards. 
and backwards. The tooth pierces the integu- 
ments of the upper lip like a horn, and its 
growth being unchecked by any opposing tooth, 
sometimes forces the lip again through the in- 
tegument and into the substance of the skull. 
The lower tusks have the ordinary direction, 
but rise rather more vertically and much higher 
than in the wild Boar. These strangely situated 
teeth are well adapted by their position to de- 
fend the eyes and assist in the act of forcing 
the head through the dense entangled under- 
wood of a tropical forest, as suggested in 
Home’s Comparative Anatomy, vol. i, p. 221, 
but their use has not been determined by actual 
observation. 
In the next group of Pachydermata ( Chero- 
potamide ) the dental formula of the existing 
type of the family Dicotyles, the Peccari, is 
as follows. 
Incis. Canine. Premolar. Molar. 
2:32 4:.1 $a:3 323 
BS SR S'ct a | 323 
The upper canines are moderately long, narrow, 
and compressed, with an entire covering of 
enamel ; while the lower are long, slightly 
curved, and have no enamel posteriorly. To 
this type of dentition belonged the Hyracothe- 
rium and the Cheropotamus, both extinct genera, 
the former having been about half the size of 
the existing Peccari, while the latter was about 
one-third larger. The Hippophyus, likewise 
an extinct genus, found in the Himmalayan 
3K 
