according to the development of the portion
of the crown they respectively support.]

The toes are nearly always armed with large, strong, curved and sharp
claws, ensheathing the terminal phalanges and held firmly in place by
broad plates of bone reflected over their attached ends from the bases
of the phalanges. In the _Felidae_ these claws are "retractile"; the
terminal phalange with the claw attached, folding back in the fore-foot
into a sheath by the outer or ulnar side of the middle phalange of the
digit, and retained in this position when at rest by a strong elastic
ligament. In the hind-foot the terminal joint or phalange is retracted
on to the top, and not the side of the middle phalange. By the action of
the deep flexor muscles the terminal phalanges are straightened, the
claws protruded from their sheath, and the soft "velvety" paw becomes
suddenly converted into a formidable weapon of offence. The habitual
retraction of the claws preserves their points from wear.

The land Carnivora are best divided into two subgroups or sections--(A)
the Aeluroidea, or Herpestoidea, and (B) the Arctoidea; the recognition
of a third section, Cynoidea, being rendered untenable by the evidence
of extinct forms.

(A) _Aeluroidea_.--In this section, which comprises the cats
(_Felidae_), civets (_Viverridae_), and hyenas (_Hyaenidae_), the
tympanic bone is more or less ring-like, and forms only a part of the
outer wall of the tympanic cavity; an inflated alisphenoid bulla is
developed; and the external auditory meatus is short. In the nasal
chamber the maxillo-turbinal is small and doubly folded, and does not
cut off the naso-turbinal and adjacent bones from the nasal aperture.
The carotid canal in the skull is short or absent. Cowper's glands are
present, as is a prostate gland and a caecum, as well as a
duodenal-jejunal flexure in the intestine, but an os penis is either
wanting or small.

Cat tribe.

The members of the cat tribe, or _Felidae_, are collectively
characterized by the following features. An alisphenoid is lacking on
the lower aspect of the skull. In existing forms the usual dental
formula is i. 3/3, c. 1/1, p. 3/2, m. 1/1; the upper molar being
rudimentary and placed on the inner side of the carnassial, but the
first premolar may be absent, while, as an abnormality, there may be a
small second lower molar, which is constantly present in some of the
extinct forms. The auditory bulla and