enclosed in semi-transparent horny cases, known on the British
coasts as "mermaids' purses," and these have tendril-like prolongations
from each of the four corners, by means of which they are moored to
sea-weed or some other fixed object near the shore, until the young
dog-fish is ready to make its exit. The larger of these species attains
a length of 4 to 5 ft., the smaller rarely more than 30 in. The picked
dog-fish (_Acanthias vulgaris_, formerly known as _Squalus acanthias_)
is pre-eminently _the_ dog-fish. It is the most abundant of the British
sharks, and occurs in the temperate seas of both northern, and southern
hemispheres. It attains a length of 4 ft., but the usual length is 2 to
3 ft., the female, as in most sharks, being larger than the male. The
body is round and tapering, the snout projects, and the mouth is placed
ventrally some distance from the end of the snout. There are two dorsal
fins, each of which is armed on its anterior edge with a sharp and
slightly curved spine, hence its name "picked." This species is
viviparous, the female producing five to nine young at a birth; the
young when born are 9 to 10 in. long and quite similar to the parents in
all respects except size. It is gregarious, and is abundant at all
seasons everywhere on the British coasts. In 1858 an enormous shoal of
dog-fish, many square miles in extent, appeared in the north of
Scotland, when, says J. Couch, "they were to be found floating in
myriads on the surface of every harbour." They are the special enemies
of the fisherman, injuring his nets, removing the hooks from his lines,
and spoiling his fish for the market by biting pieces out of them as
they hang on his lines. They are however eaten, both fresh and salted,
by fishermen, especially on the west coast of England, and they are sold
regularly in the French markets.

DOGGER BANK, an extensive shoal in the North Sea, about 60 m. E. of the
coast of Northumberland, England. Over its most elevated parts there is
a depth of only about six fathoms, but the depth is generally from ten
to twenty fathoms. It is well known as a fishing ground. The origin of
the name is obscure; but the middle Dutch _dogger_ signifies a trawling
vessel, and was formerly applied generally to the two-masted type of
vessel employed in the North Sea fisheries, and also to their crews
(doggermen) and the fish taken (dogger-fish). Off the south end of the
bank an engagement took place between English a