to hoofed beasts, but outlasting them into the succeeding age. These two
groups of generalized mammals approached each other so nearly in
structure, that it is even doubtful to which of them certain outlying
fossils should be referred, and the assumption is quite justified that
they had a common ancestor in the preceding period, of which no record
is yet known.

The most evident points in which _Carnivora_ differ from
_Ungulata_ are their possession of at least four and frequently
five digits, which always bear claws and never hoofs; all but the sea
otter have six small incisor teeth in each jaw; the canines are large;
the molars never show flattened, curved crests after the ruminant
pattern, but are more or less tubercular, and one tooth in the hinder
part of each jaw becomes blade-like, for shearing off lumps of
flesh. This tooth is called the sectorial, or carnassial.

Existing carnivores are conveniently divided into three sections:
_Arctoidea_--bears, raccoons, otters, skunks, weasels, etc.;
_Canoidea_--dogs, wolves and foxes; _Aeluroidea_--cats,
civets, ichneumons and hyaenas.

It is highly probable that these three chief types have descended in as
many distinct lines from the _Creodonta_, and that they were
differentiated as early as the middle Eocene, but their exact degree of
affinity is uncertain; bears and dogs are certainly closer together than
either of them are to cats, and it is questionable if otters and
weasels--the _Mustelidae_, as they are termed--and raccoons are
really near of kin to bears.

Seals are often regarded as belonging to this order, but their relation