to the rest of the carnivores is very doubtful. Many of their characters
are suggestive of _Arctoidea_, but it is an open question if their
ancestors were bear or otter-like animals which took to an aquatic life,
or whether they may not have had a long and independent descent. At all
events, doubt is cast upon the proposition that they are descended from
anything nearly like present land forms by the fact that seals of
already high development are known as early as the later Miocene.

The difficulty so constantly met with in attempting to state concisely
the details of classification, is well shown in this order, for its
subdivisions rest less upon a few well defined characters than upon
complex associations of a number of lesser and more obscure ones, a
recapitulation of which would be tedious beyond the endurance of all but
practiced anatomists. For the present purposes it must be enough to say
that bears and dogs have forty-two teeth in the complete set, of which
four on each side above and below are premolars, and two above, with
three below, are molars, but these teeth in bears have flatter crowns
and more rounded tubercles than those of dogs, and the sectorial teeth
are much less blade-like, this style of tooth being better adapted to
their omnivorous food habits. Bears, furthermore, have five digits on
each foot and are plantigrade, while dogs have but four toes behind and
are digitigrade. These differences are less marked in some of the
smaller arctoids, which may have as few as thirty-two teeth, and come
very near to dogs in the extent of the digital surface which rests upon
the ground in walking.

In distinction from these, _Aeluroidea_ never have more than two
true molars below, and the cusps of their teeth are much more sharply
edged, reaching in the sectorials the extreme of scissor-like
specialization. In all of them the claws are more or less retractile,