et.

DESCRIPTION.--Reddish-brown, white under the chin, and then again
a patch on the chest.

_LUTRIDAE--THE OTTERS_.

We now come to the third group of the musteline animals, the most
aquatic of all the Fissipedia--the _Lutridae_ or Otters--of which
there are two great divisions, the common Otters (_Lutra_) and the
Sea-Otters, (_Enhydra_). With the latter, a most interesting animal
in all its ways, as well as most valuable on account of its fur, we
have nothing to do. I am not aware that it is found in the tropics,
but is a denizen of the North Pacific. Of _Lutra_ we have several
species in two genera. Dr. Gray has divided the Otters into no less
than nine genera on three characteristics, the tail, feet, and muzzle,
but these have been held open to objection. The classification most
to be depended upon is the division of the tribe into long-clawed
Otters (_Lutra_), and short or rudimentary-clawed Otters (_Aonyx_).
The characteristics of the skulls confirm this arrangement, as the
short-clawed Otters are distinguishable from the others by a shorter
and more globose cranium and larger molars, and, as Dr. Anderson says,
"the inner portion of the last molar being the largest part of the
tooth, while in _Lutra_ the outer exceeds the inner half; the almost
general absence of the first upper premolar; and the rudimentary
claws, which are associated with much more feebly-developed finger
and toe bones, which are much tapered to a point, while in _Lutra_
these bones are strong and well developed." Gray has separated a
genus, which he called _Pteronura_, on account of a flattened tail
arising from a longitudinal ridge on each side, but this flattening
of the tail is common to all the genera more or less.

All the Otters, though active on land, are still only thoroughly at
home in the water, and they are therefore specially constituted for
such a mode of life. They have an elongated flattened form; webbed
feet with short claws; compressed and tapering tail; dense fur of
two kinds, one of long brown shining hairs; the under fur short and
fine, impervious to wet, and well adapted for keeping an equality
of temperature; the skull is peculiar, the brain case being very long,
and compressed from above downwards; the facial portion forms only
about one-fourth of the extreme length; the teeth are strong and
sharp; the upper flesh tooth very large.

[Illustration: Otter's skull (side and under view).]

Dental formula: Inc., 3--