The dentition of the Carnivora varies according to the exclusiveness of their fleshy diet, and the nature of that diet.
In taking two typical forms I give below sketches from skulls in my possession of the tiger, and the common Indian black bear; the one has trenchant cutting teeth which work up and down, the edges sliding past each other just like a pair of scissors; the other has flat crowned molars adapted for triturating the roots and herbage on which it feeds. A skull of an old bear which I have has molars of which the crowns are worn almost smooth from attrition. In the most carnivorous forms the tubercular molars are almost rudimentary.
The skull exhibits peculiar features for the attachment of the necessary powerful muscles. The bones of the face are short in comparison with the cranial portion of the skull (the reverse of the Herbivores); the strongly built zygomatic arch, the roughened ridges and the broad ascending ramus of the lower jaw, all afford place for the attachment of the immense muscular development. Then the hinge of the jaw is peculiar; it allows of no lateral motion, as in the ruminants; the condyle, or hinge-bolt of a tiger's jaw (taken from the largest in my collection), measures two inches, and as this fits accurately into its corresponding (glenoid) cavity, there can be no side motion, but a vertical chopping one only. The skeleton of a typical carnivore is the perfection of strength and suppleness. The tissue of the bones is dense and white; the head small and beautifully articulated; the spine flexible yet strong. In those which show the greatest activity, such as the cats, civets and dogs, the spinous processes, especially in the lumbar region, are greatly developed—more so than in the bears. These serve for the attachment of the powerful muscles of the neck and back. The clavicle or collar-bone is wanting, or but rudimentary. The stomach is simple; the intestinal canal short; liver lobed; organs of sight, hearing, and smell much developed.
Now we come to the divisions into which this group has been separated by naturalists. I shall not attempt to describe the various systems, but take the one which appears to me the simplest and best to fit in with Cuvier's general arrangement, which I have followed. Modern zoologists have divided the family into two great groups—the Fissipedia (split-feet) or land Carnivora, and the Pinnipedia (fin-feet) or water Carnivora. Of the land Carnivora some naturalists have made the following three groups on the characteristics of the feet, viz., Plantigrada, Sub-plantigrada and Digitigrada. The dogs and cats, it is well known, walk on their toes—they are the Digitigrada; the bears and allied forms on the palms of their hands and soles of their feet, more or less, and thus form the other two divisions, but there is another classification which recommends itself by its simplicity and accuracy. Broadly speaking, there are three types of land carnivores—the cat, the dog, and the bear, which have been scientifically named Æluroidea (from the Greek ailouros, a cat); Cynoidea (from kuon, a dog); and Arctoidea (from arctos, a bear). The distinction is greater between the families of Digitigrades, the cat and dog, than between the Plantigrades and Sub-plantigrades, and therefore I propose to adopt the following arrangement:—
| I. ARCTOIDEA |
Plantigrades. Sub-plantigrades. |
|
II. ÆLUROIDEA III. CYNOIDEA | Digitigrades. |
I may here remark that the Insectivora are in most cases plantigrade, therefore the term is not an apposite one as applied to the bear and bear-like animals only, but in treating of them under the term Arctoidea we may divide them again into Plantigrades and Sub-plantigrades.