Stretching out its feet, it swims obliquely in the direction of
the so-called head, and by this mode of swimming it can see in
front, for its eyes are at the top, and in this attitude it has its
mouth at the rear. The 'head', while the creature is alive, is hard,
and looks as though it were inflated. It apprehends and retains
objects by means of the under-surface of its arms, and the membrane in
between its feet is kept at full tension; if the animal get on to
the sand it can no longer retain its hold.

There is a difference between the octopus and the other molluscs
above mentioned: the body of the octopus is small, and his feet are
long, whereas in the others the body is large and the feet short; so
short, in fact, that they cannot walk on them. Compared with one
another, the teuthis, or calamary, is long-shaped, and the sepia
flat-shaped; and of the calamaries the so-called teuthus is much
bigger than the teuthis; for teuthi have been found as much as five
ells long. Some sepiae attain a length of two ells, and the feelers of
the octopus are sometimes as long, or even longer. The species teuthus
is not a numerous one; the teuthus differs from the teuthis in
shape; that is, the sharp extremity of the teuthus is broader than
that of the other, and, further, the encircling fin goes all round the
trunk, whereas it is in part lacking in the teuthis; both animals
are pelagic.