The distribution of the Carnivora is world-wide, excluding only the Australian region, if, as seems probable, the Dingo of that region is an introduced species. The most striking features in their distribution are perhaps the following:—There are no Bears in the Ethiopian region or in Madagascar, and but a single species in the Neotropical. The only Carnivora in Madagascar are the Viverridae, and of the seven genera there found six are peculiar. The Procyonidae are nearly entirely New World in range; out of sixteen genera of Mustelidae only five are New World, and only two of those are peculiar to the American continent. The Hyaenidae are limited to the Old World.
The classification of the Carnivora is a matter which is difficult, and which has therefore been very variously effected. It is unfortunate that the classification of Flower (based upon the researches of H. N. Turner as well as his own, and accepted by Mivart) should fail when applied to fossil forms. For it separates with great clearness the existing genera into three great divisions, the Cynoidea, Aeluroidea, and Arctoidea, definable by visceral as well as by osteological characters. The apparent anomaly, too, of a single supposed Viverrine genus, to wit Bassariscus, existing in America, while all the rest of its kin are Old-World forms, was shown by his characters to be neither an anomaly nor a fact. It will be better, therefore, to divide the Carnivora into the families, Felidae, Machaerodontidae, Viverridae, Hyaenidae, Canidae, Ursidae, Procyonidae, and Mustelidae, indicating at the same time the reasons for and against retaining the three divisions of Sir W. Flower.
Fam. 1. Felidae.[[258]]—This family includes only the Cats (i.e. Lions, Tigers, "Cats," Hunting Leopard, etc.), and is to be distinguished by the following characters:—In the skull the auditory bulla is much inflated, and there is an internal septum; the paroccipital processes are flattened against the bullae. There is no alisphenoidal canal. The dental formula is I 3, C 1, Pm 3 to 2, M 1. The carnassial tooth of the upper jaw has three lobes to the blade; that of the lower jaw is without an inner cusp.
The digits are five on the fore-feet, four on the hind. The caecum is present and small. This family contains but two genera, Felis and Cynaelurus.
Fig. 193.—Section of auditory bulla of Tiger. am, Auditory meatus; BO, basioccipital; e, Eustachian canal; ic, oc, two chambers of bulla divided by s, septum; *, their aperture of communication; Pt, periotic; Sq, squamosal; t, tympanic ring. (From Flower's Osteology.)
The genus Felis is very wide in its distribution, being common to both the Old and the New Worlds. Its distinctive characters, as opposed to Cynaelurus, are mainly the following:—The claws are retractile, and the retractility is more markedly developed than in the Cheetah. The molar is not so nearly in a line with the other teeth; the upper carnassial, moreover, has an inner tubercle. The legs are relatively shorter.
The complete retractility of the claws is a very distinctive feature of the true Cats. It is brought about in this way: the terminal joint of the toe, which is clad with the claw, folds back into a sheath by the outer side of or above the middle phalanx. It is held in this position by a strong ligament. The flexor muscles straighten the phalanx which bears the claw, so that the natural position for the animal is to be in a state of retracted claws, which of course preserves them from friction; when wanted for aggressive purposes, they are pulled into sight by the action of the muscles already mentioned.
Fig. 194.—The phalanges of the middle digit of the manus of the Lion (Felis leo). × ½. a, The central portion forming the internal support to the horny claw; b, the bony lamina reflected around the base of the claw; ph1, proximal phalanx; ph2, middle phalanx; ph3, ungual phalanx. (From Flower's Osteology.)