BRITISH MAMMALS 303

molluscs, and may often be seen pursuing a shoal of herrings, of
which they are very fond. At one time they were captured inlarge |
numbers, not only for the sake of their flesh, which was eaten, but
also for the fat stored so abundantly beneath the skin, and for the
skin itself, of which a splendid leather is made.

Being a lung-breathing animal, the porpoise must necessarily
come to the surface of the water at short intervals to renew its supply
of air. The expended air is forcibly expelled through its ‘blow-
holes,’ as the nostrils are termed; and after it has taken a fresh
supply and again dived under, the water is prevented from entering
the air passages through these openings by folds of the skin that
extend over them, acting as valves.

After all, there is not a great deal to be learnt about the porpoise
by simply watching it in the water. If we are to know anything of
its structure we must examine one that has been removed from its
native element. Under these circumstances we can at once point
out many features in which it is different from all the fishes. Its
thick skin is smooth, and not protected by scales. It has no visible
hind limbs, and the fore pair are fin-like, but then they are very
different in appearance and structure from the fins of fishes. It is

- certainly fish-like in form, and, like fishes, has no neck; but its
skeleton always contains the seven vertebre or neck bones which
characterise the Mammals. The tail is horizontal, consisting of
two flat lobes, and is the chief means of locomotion ; but, instead
of rays with intervening membrane, like the tails of fishes, it is
composed ‘of folds of the skin. Its jaws are armed with a great
number of simple teeth, not at all large considering the dimensions
of the owner.

If Seals were common on our coasts we should undoubtedly
regard them with great interest; for not only are their movements
and habits very entertaining when watched in their native element,
but they are capable of becoming gentle and intelligent domestic
pets. But since they are to be observed only on the less accessible
parts of our northern shores, we shall pass on at once to the Carni-
vorous Mammals.

CarNtvorous MAmMALs

It will not be necessary to enter any further into the distinguish-
ing features of the Flesh-eating Mammals, having already pointed
out their chief characteristics on page 299,