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.)
Much has been written as to the shape of the pupil of the Cat's eye. Some careful observations upon the matter have been
