38 CREPIDULA FORNICATA, L., OFF THE COAST OF ESSEX.
laid down when about a year old. I have lately (December 14th,
1893) received another shell from Burnham-on-Crouch.
All these shells present considerable variability in shape, size, and
colouring, much as the American specimens do, as they adapt
themselves to the shape of the object on which they adhere.
I have compared the radula of one of these with the drawing by
Troschel, to which it corresponds.
I may add that I received with the last shell a quantity of jelly-
like spawn, which is said to be that of the mollusc in question.
It is certainly curious to find living specimens of a North
American species on our shores. They have, no doubt, been
introduced with oysters, have found conditions favourable for
existence in our layings; and may even have propagated their
species, although we have at present no certain evidence of this.
On reading some notes upon this subject at a meeting of the
Malacological Society of London (vide Proc. Mala. Soc, Vol. i,
p. 19), on the 14th July last, I was informed by Mr. H. Wallis Kew
that some dead shells had been found on the Lincolnshire coast, in
1887-8, by Mr. Arthur Smith of Great Grimsby, who had recorded
them in the [Yorkshire] "Naturalist" for 1888, p. 275. Mr. Smith's
note is as follows :—
" While searching for specimens on Grimsby Beach, I found a
shell which I did not recognise as being British, nor had I found or
seen such a shell before. This was in November, 1887. Some
weeks after I found another. I sent one to the Natural History
Museum at South Kensington. It was kindly returned to me as
Crepidula fornicata, a native of the east coast of North America, and
I was told that it had possibly been thrown out of some ship with
ballast, and then washed ashore ; but as I continued to find speci-
mens I could scarcely think this to be the case. After making
inquiries I have learnt that they are brought from America with the
American oysters, which are deposited at Cleethorpes for the use of
visitors to this seaside resort in the summer season. As yet I have
not found living specimens, although a friend assures me they are
often adhering the shells of the oysters when first brought here."
The occurrence of this species is again mentioned by Mr. Kew
in his "Shells of the Lincolnshire Coast" ("Naturalist," 1889, pp.
358, 359), and I have since had the opportunity, through his kindness,
of seeing the shells which were taken in the Humber.1
1 I may add that Mr. H. Wallis Kew, F.Z.S., is the author of a very interesting book
published recently, on ''The Dispersal of Shells."