CONCLUSIONS. 567 
Trichechoidea by GisBen in 1847, Trichechina by Gray in 1850, 
fiosmaridae by Git in 1866, Rosmaroidea by Git in 1872, and 
Odobaenidae by Auten in 1880!!!). The section contains only the 
walruses. 
b. — The early forms of this section must have had hind-flappers 
which were smaller than the fore-flappers, and a tail which was 
as long as the head, neck and trunk together. The animals were 
very slender and elongated in form, the neck being somewhat more 
elongated; external ears, though small, were still present. Further 
characters are: “Anterior portion of the skull not unusually swollen, 
and the canines not highly specialized.” They came very seldom 
aland, and when doing so, they must have only supported them- 
selves on their breast and on their fore-flappers, leaving the long 
tail always in the water. They swam with vertical undulations, 
using also sometimes the flappers. — For this section I choose the 
name of Z'enuia, or Animals which are slender. — Very early the 
section of the Zenuwia divided itself into two smaller divisions which 
are marked below with 1 and 2. — 
1. — The members of this division changed their manner of 
living. They very often crawled on ice, land and rocks; the tail 
was a very inconvenient organ in their new manner of living, con- 
sequently all the individuals with a somewhat shorter tail than 
their congeners’, were better equipped and survived the others, so 
that at last a group of animals arose of which the tail has become 
very short, almost disappearing between the hind-legs which on the 
contrary to make up for this loss of tail, gradually became larger, 
so as to become even larger than the anterior feet. The further 
characters of this group are: “With small external ears. Incisors 
of deciduous dentition ¢, only the outer on either side cutting the 
gum; of permanent dentition ;, the two central pairs of the upper 
with a transverse groove. Postorbital processes strongly developed. 
Surface of the mastoid processes not continuous with the auditory 
bullae.” — This division was called 4uriculata by Piron in 1816, 
(afterwards also called Otariina by Gray in 1825, Otariadae by 
Brookes in 1828, Arctocephalina by Gray in 1837, and O¢aridae 
by Grit in 1866) containing the sea-bears and sea-lions. 
2.— The members of this division did not accustom themselves 
to live in the midst of ice and rocks, consequently they retained 
the long tail, and small hind-legs. As the animals retained also 
their slenderness and extraordinary litheness, a long neck with a 
relatively small head must have been of great use to them, and 
