302
THE ESSEX NATURALIST.
Feb. 5 3.45 p.m. Tingle resettled on original boring
and working.
„ 6 9.30 a.m. Ditto.
„ 7 10.30 a.m. Oyster bored through and eaten in four
days ; the tingle resettled after removal
twice.
Sometimes two or three individuals will attack one and the
same oyster, and an oyster is liable to attack on almost any
part of the shell and on either valve.
It is probable that any part of the shell of an oyster—or indeed
any other mollusc—may be attacked by a drill, if the contour
permits of the latter obtaining purchase for its shell and foot
for the efficient action of its drill, i.e., its radula.
Urosalpinx has also been observed to bore through and eat
the American slipper-limpet Crepidula fornicata, but this limpet
is attacked in the River Blackwater in very much smaller numbers
than are young oysters. It is probable that the American oyster-
drill may eat barnacles also in the absence of other prey, and
further observations on this matter are desirable.
It is an interesting fact that Urosalpinx has been shown by
Federighi (7) to have the curious habit of creeping against a cur-
rent if the rate of flow of water is not more than about 7.6 centi-
metres per second. An obvious advantage of this habit (rheotrop-
ism) is that the animal will usually be travelling towards the
source of such scents as it may be able to appreciate. There is,
therefore, scope for interesting experimental observations on the
re-actions of Urosalpinx to scents, with the possibility of economic
application of the results.
HABITS OF OCINEBRA.
The rough whelk-tingle, Ocinebra erinacea, is known to occur
around the coasts of the greater part of the British Isles (Jeffreys,
8) in places where oysters do, and do not, occur. The food of
this animal must, therefore, vary in different habitats, and experi-
ments have shown (6) that Ocinebra erinacea from Plymouth
Sound, when kept in tanks with young oysters, only rarely eat
the oysters, while under the same conditions Ocinebra erinacea
from West Mersea devoured oysters almost as rapidly as Urosal-
pinx. At the same time Ocinebra erinacea from the Falmouth
oyster beds ate a smaller quantity of oysters and, in another set