298
ON THE OYSTER-DRILLS IN THE ESSEX
ESTUARIES.
BY J. H. ORTON, D.Sc., F.L.S.
(With 1 Plate and 2 text figures.)
CONTENTS.
PAGE
Introduction .. .. .. .. .. .. .. .. 298
Occurrence of Urosalpinx cinerea in England .. .. .. 299
Habits of Urosalpinx .. .. .. .. .. .. .. 300
Habits of Ocinebra .. .. .. .. .. .. .. 302
Habits of Purpura .. .. .. .. .. .. .. 303
The egg-capsules of oyster-drills .. .. .. .. .. 305
Summary . . .. .. .. .. .. .. .. .. 306
References . . .. .. .. .. .. .. .. .. 306
INTRODUCTION.
IT is well known that marine animals have been intro-
duced into the Essex Estuaries on oysters which have been
imported from America and relaid in the neighbouring creeks.
In the year 1908 I myself saw living crow-oysters (Anomia sp.)
and slipper-limpets (Crepidula fornicata) on American oysters on
board the vessel which had brought them from America to the
Thames Estuary, having been courteously invited to inspect
the shipment by the importing oyster-merchants.
This definite observation proves that a percentage of certain
animals attached to oysters can survive (as do the oysters)
transportation from America to England in the hold of a ship.
Under the conditions of transport mentioned above it was esti-
mated that the animals would be out of water for about fourteen
days.
Animals introduced into English waters in this way often
find the general conditions of life more suitable than in their
original home, and may thrive and spread rapidly in the new
environment, as has the American slipper-limpet, to the con-
fusion of oyster-cultivators (1). Whereas, however, the slipper-
limpet is only a competitor of the oyster for food and space, the
whelk-tingles or oyster-drills or borers—as they are variously
named—actually kill oysters by boring a hole in the shell with