cts under the influence of light in some species to a
narrow vertical slit, in others to an oval, and in some to a circular
aperture. The tongue is thickly covered with sharp, pointed, recurved
horny papillae; and the caecum is small and simple.

As in structure so in habits, the cat may be considered the most
specialized of all Carnivora, although they exhibit many features
connecting them with extinct types. All the members of the group feed
almost exclusively on warm-blooded animals which they have themselves
killed, but one Indian species, _Felis viverrina_, is said to prey on
fish, and even fresh-water molluscs. Unlike dogs, they never associate
in packs, and rarely hunt their prey on 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 are
widely diffused over the greater part of the habitable world, though
most abundant in the warm latitudes of both hemispheres. None 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 contrary, most of the groups into which the family may be divided
have representatives in both hemispheres.

Notwithstanding the considerable diversity in external appearance and
size between different members of this extensive family, the
structural differences are but slight. 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, especia