434 MAMMALIA [CARNIVORA. generally prolonged into a linear fissure. In the most specialized Carnivora, as the Fdidse, (I.), the blade alone is developed, both heel and inner tubercle being absent or rudimentary. In others, as Meles (V.) and Ursus (VI,), the heel is greatly developed, broad, and tuberculated. The blade in these cases is generally placed obliquely, its flat or convex (outer) side looking forwards, so that the two lobes are almost side by side, instead of anterior and posterior. The inner tubercle (3) is generally a conical pointed cusp, placed to the inner side of the hinder lobe of the blade. The special characters of these teeth are more disguised in the Sea Otter (Enliydra) than in any other form, but even in it they can be traced. The toes are nearly always armed with large, strong, curved, and tolerably sharp claws, en sheathing the ungual phalanges, and held more firmly in their places by broad laminae of bone reflected over their attached ends from the bases of the phalanges. In some forms, most notably the Felidx, these claws are "retractile." The ungual phalanx, with the claw attached, folds back in the fore foot into a sheath by the outer or ulnar side of the middle phalanx of the digit, being retained in this position when the animal is at rest by a strong elastic ligament. In the hind foot the ungual phalanx is retracted on to the top, and not the side of the middle phalanx. By the action of the deep flexor muscles, the ungual phalanges are straightened out, the claws protruded from their sheath, and the soft " velvety " paw becomes suddenly converted into a most formidable weapon of offence. The habitual retraction of the claws pre serves their points from wear in ordinary progression. The Fissipedal Carnivora were divided by Cuvier into two groups, according to the position of the feet in walking, the Plantigrada, or those that place the whole of the soles to the ground, and the Digitigrada, or those that walk only on the toes ; and the difference between these groups was considered of equal importance to that which separated from them both the Pinnigrada or Seals. The distinction is, however, quite an artificial one, and every intermediate condition exists between the extreme typical plantigrade gait of the Bears and the truly digitigrade walk of the Cats and Dogs ; in fact, the greater number of the Carnivora belong to neither one form nor the other, but may be called "sub-plantigrade," often when at rest applying the whole of the sole to the ground, but keeping the heel raised to a greater or less extent when walking. A more natural classification is into three distinct sections, of which the Cats, the Dogs, and the Bears may be respectively taken as representatives, and which are hence called jEluroidea, Cynoidea, and Arctoidea. This division is founded mainly on characters exhibited by the base of the skull, but is corroborated by the structure of other parts. 1 The presence or absence of a bridge of bone, covering the external carotid artery in a part of its course by the side of the alisphenoid bone, and enclosing the " alisphenoid canal," a character to which the late Mr H. N. Turner first drew attention, might seem unimportant at first sight, but it is curiously constant in certain groups, which we have other reasons, derived often from a com bination of less easily definable characters, to regard as natural. It is therefore generally mentioned in the follow ing family definitions. Section ^ELUROIDEA. The sEluroidca or Cat-like forms include the Felid.se, Viverridss, Protelidas, and Hy&nidse. 1 See W. H. Flower, "On the Value of the Characters of the Base of the Cranium in the Classification of the order Carnivora," Proc. Zool. Soc., 1869, p. 4 ; St George Mivart, "On the Classification and Distribution of the ^Eluroidea," ibid., 1882, p. 135; and Id., The Cat, an Introduction to the Study of Backboned Animals, especially Mammals, 1881. Family True molars reduced to one above and below, that of the upper jaw very small and transversely extended. Only two inferior prc- molars. Auditory bulla not externally constricted, but internally divided by a septum. No alisphenoid canal. Carotid canal very minute. Digits 5-4. Dorsal vertebra 13. Pel-is. The whole structure of the animals of this genus ex hibits the carnivorous type in its fullest perfection. Dentition :
- > c T> P ib m T~T i total 30. The upper anterior premolar,
always small, may sometimes be absent without any other modifi cation in the dental or other structures. Such a variation should not therefore be considered as of generic importance. Incisors very small. Canines large, strong, slightly recurved, with trenchant edges and sharp points, and placed wide apart. Premolars com pressed and sharp-pointed. The most posterior in the upper jaw (the sectorial) a very large tooth, consisting of a subcompressed blade, divided into three unequal cusps supported by two roots, with a very small inner lobe placed near the front end of the tooth and supported by a distinct root. The upper true molar a very small tubercular tooth placed more or less transversely at the inner side of the hinder end of the last. In the lower jaw the true molnr (sectorial) reduced to the blade alone, which is very large, trenchant, and much compressed, divided into two subequal lobes. Occasion ally it has a rudimentary heel, but never an inner tubercle. The skull generally is short and rounded, though proportionally more elon gated in the larger forms. The facial portion is especially short and broad, and the zygomatic arches very wide and strong. The auditory bullaa are large, rounded, and smooth. Vertebrae : C 7, D 13, L 7, S 3, C 13-29. Clavicles better developed than in other Carnivora, but not articulating with either the shoulder bones or sternum. Limbs digitigrade. Anterior feet with five toes, the third and fourth nearly equal and longest, the second slightly and the fifth considerably shorter ; the pollex still shorter, not reaching as far as the metacavpo-phalangeal articulation of the second. Hind feet with only four toes. The third and fourth the longest, the second and fifth somewhat shorter and nearly equal ; the hallux represented only by the rudimentary metatarsal bone. The claws all very large, strongly curved, compressed, very sharp, and exhibiting the retractile condition in the highest degree. The tail varies greatly in length, being in some a mere stump, in others nearly as long as the body. Ears of moderate size, more or less triangular and pointed. Eyes rather large. Iris very mobile, and with a pupillary aperture which contracts under the influence of light in some spe.:ics to a narrow vertical slit, in others to an oval, and in some to a circular aperture. Tongue thickly covered with sharp- pointed, recurved horny papillae. Caecum small and simple. As in structure so in habits, the Cats may be considered the most specialized of all the Carnivora. All the known members of the genus feed, in the natural state, almost exclusively on warm-blooded animals which they have themselves killed. One Indian species (F. vivcrrina) is said to prey on fish and even freshwater molluscs. Unlike the Dogs, they never associate in packs, and rarely hunt their prey in open ground, but from some place of concealment wait until the unsuspecting victim comes within reach, or with noiseless and stealthy tread, crouching close to the ground for concealment, approach near enough to make the fatal spring. In this manner they frequently attack and kill animals considerably exceeding their own size. They are mostly nocturnal, and the greater number, especially the smaller species, more or less arboreal. None are aquatic, and all take to the water with reluctance, though some may habitually haunt the banks of rivers or pools, because they more easily obtain their "prey in such situations. The numerous species of the genus are very widely diffused over the greater part of the habitable world, though most abundant in the warm latitudes of both hemispheres. No species are, however, found in the Australian region, or in Madagascar. Although the Old -World and New- World Cats (except perhaps the Northern Lynx) are all specifically distinct, no common structural character has been pointed out by which the former can be separated from the latter. On the con trary, most of the minor groups into which the genus has been divided have representatives in both hemispheres. Notwithstanding the considerable diversity in external appearance and size between different members of this extensive genus, the structural differences are but slight, and so variously combined in different species that the numerous attempts hitherto made to subdivide it are all unsatisfactory and artificial. The principal differences are to be found in the form of the cranium, especially of the nasal and adjoining bones, the completeness of the bony orbit posteriorly, the development of the first upper premolar and of the inner lobe of the upper sectorial, the length of the tail, the form of the pupil, and the condition and coloration of the fur, especially the presence or absence of tufts or pencils of hair on the external ears. There is one decidedly aberrant form, which enables us to divide the genus into two sections, to which the rank of genera is sometimes accorded. 1. Felis proper. A distinctly cusped inner lobe to the upper
sectorial tooth. Claws completely retractile. There arc about