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.[268]--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. {391} 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_. [Illustration] 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.