36
ON THE OCCURRENCE OF CREPIDULA.
FORNICATA, L., OFF THE COAST OF
ESSEX.
By WALTER CROUCH, F.Z.S. (Vice-President).
[Read, 24th February, 1894.]
OF the family Calyptraeidae, so far as I am aware, only one genus
and species has hitherto been recorded as occurring in Great
Britain ; i.e., Calyptraea sinensis, of Linnaeus. This marine mollusc
is, I believe, mainly confined to the Southern coast and Channel
Islands. I have taken live specimens off the coast of South Devon,
and also near Weymouth, Dorset, where it is fairly common, and
generally found attached to stones.
On the 6th of September, 1891, when staying at Brightlingsea,
in Essex, I ferried over one morning to Stone Point, St. Osyth, there
awaiting some friends who were staying at East Mersea, and had
agreed to bring the boat over to the "hard" to fetch me ; but the
sea was very rough, rolling in from the German Ocean with a S.W.
wind, making the estuary of the Rivers Colne and Blackwater
choppy and dangerous. They dared not venture, nor would any
boatman take me across, so I turned my attention to the shore and
surroundings. The previous day I had found Paludestrina ventrosa
by the thousand in the brackish water of the ditch of the Martello
Tower on the Point.
In getting marine species I was not very successful, but I took a
quantity of Truncatella truncatula, Lacuna crassior, and a few
Anomia ephippium. The former were all on the underside of large
stones, and had never before been recorded in Essex.
My surprise was great when on turning over a broken bit of
oyster-shell (not a native), on the Zostera which abounds here and
is rolled in like ropes by the sea, to find attached a dead shell of
Crepidula fornicata, a shell common on the east coast of North
America. I remained searching for a long time, picking up and
examining every bit of oyster-shell I could see, but could not find
another.
From later inquiries I ascertained that at some time young
American oysters had been laid down here to fatten, but whether
from the east or west coast I could not discover. That fact, how-
ever, sufficiently accounted for a non-European shell being found
there, and I concluded that it had been brought over attached to the
oyster. I was aware that French and Portuguese oysters had often