ANOPLOTHEUE.

523

CHAPTER XII.

TEETH OF UNGULATA.

The most complex and varied systems of dentition are to befound in the different Orders, Families and Genera of the greatnatural group of hoofed Quadrupeds. From this group it willsuffice for the objects of the present Work to select certainexamples to elucidate the leading modifications of the systems ofcomplex teeth, and these examples will be taken from the typicalspecies of the Isodactyle(l), the Anisodactyle(2), and the Probosci­ dian divisions of the Ungulata.

Although the structure of the molar teeth presents verydifferent degrees of complication and is much modified in theIsodactyle Ungulata, it generally produces a more symmetricalform or pattern of the grinding surface than in the Anisodactyledivision. I shall commence with the dentition of an extinctgenus of the Isodactyle group.

191. Anoplotherium. —The Anoplothere was one of the earliestforms of hoofed quadrupeds introduced upon the surface of thisearth, and it is characterized by the most complete system of den-tition : it not only possessed incisors and canines in both jaws,but these were so equably developed that they formed one un-broken series with the premolars and molars, which character isnow found only in the Human species.

The dental formula of the genus Anoplotherium is :—

in. —; c. —; p. —; m. —: = 44. (PI. 135. fig. 1—3.)Those teeth which are transitorily manifested in the embryo-state

(1) Hoofed Quadrupeds with toes in even number, as two or four, and which have a moreor less complicated stomach, with a moderate sized simple coecum. Ex. Ox, Hog, Peccari ,Hippopotamus.

(2) Hoofed Quadrupeds with toes, (on the hind-foot at least,) in uneven number, as onethree, or five, the latter number being manifested by the Proboscidians . All these have asimple stomach and an enormous coecum. Ex. Horse, Tapir, Rhinoceros , Elephant: but thelast Pachyderm combines, with its proboscis, so many other peculiarities of structure, as to havebeen recognised as the type of a distinct group of Ungulata, most of the members of which groupare now extinct.