NOTES—ORIGINAL AND SELECTED.
99
the work of Sesia crabroniformis, which is said to be also a poplar
feeder in the N. of England, though I have only found it affect-
ing different species of Salix hereabouts. The cause of the
mischief is now clear, and I am glad to find the Saperda well
established at home after looking for it in vain in another
county.—W. H. Harwood, Colchester, August 18th, 1907.
MOLLUSCA.
Notes on the occurrence of Crepidula fornicata (the
"Slipper Limpet") in the River Crouch.—This mollusc,
which is a native of the West Indies and South America, seems
to have settled permanently here about the commencement of
the present century. In volume v. of the Essex Naturalist, page
260, mention is made of a dead shell, exhibited by Mr. Walter
Crouch, which he found adhering to an introduced oyster-
This was in 1891. In 1893, Mr. Woodward writes me, live
specimens from the Crouch and Roach rivers were exhibited
before the Malacological Society, and last year it has again been
reported alive from the Crouch river1. Judging from the large
quantities I have just seen at Bridge Marsh, it would now seem
to be fully established in the Crouch, and as I was enabled to
find young as well as mature specimens, there can be no doubt
that it is now breeding freely there..
It is regarded by the dredgermen as the "oyster's enemy,"
and that is the name they have attached to it.
This curious shell, which has, I believe, no near relation in
Great Britain, is about the size of a three-quarter grown mussel
valve. Its apex being lateral makes the shell, when looked at
from above, somewhat to resemble the Haliotis, but at this point
all likeness ceases. Underneath, and beneath the aperture,
the shell is provided with a thin porcellaneous membrane which
stretches across the posterior half of the shell. The animal
appears to occupy both sides of this membrane, the muscular
adductor part being at the top, whilst the softer parts and
viscera may be tucked underneath for safety. This shelly
membrane is said to present the rudiments of a columella, and
to those who have observed the univalve molluscs of a higher
1 A considerable amount of information respecting the occurrence and habits of Crepidula
will be found in the Essex Naturalist. Mr. Crouch's original paper "On the occurrence
of Crepidula formicata off the Coast of Essex" was published in E.N., vol. viii., pp. 36-38,
and "Further Notes" in vol. x., 353-5. See also a note by Mr. J, E. Cooper on the shell at
Burnham-on-Crouch. E.N., vol. xiv., p. 73.—Ed.