206 THE ESSEX NATURALIST.
fig. 4). The shell is described by Defrance as "very thin, rounded,
dilated, upper valve flat, much smaller than the lower ; lamellae
membranaceous, imbricated and very distinct." The scales are
a yellowish brown colour, large and loose, and allow the upper
valve to sink in when removed. A fine example of this shell is
in the British Museum collection, and a shell very similar to
this comes into the lower English Channel, from whence the
trawlers occasionally bring them in. These grow to a large size,
one of mine being, length 130 mm., breadth 135 mm. The top
valve is thin, the horny lamellae projecting nearly half-an-inch
beyond the margin of the shell. The lower valve is very broad
and shallow, with numerous costae foliated below, and at times
purple in colour.
The McAndrew Coll. (Cambridge) has a cluster of these shells
from Gibraltar, very delicate in texture, almost transparent.
It is the Atlantic equivalent of the O. edulis of the Eastern British
coasts, and has probably furnished the name to Mediterranean
conchologists.
I obtained, through a fisherman, a number of oysters from
Caldy Island, collected at low water, in which the upper
valve is deeply recessed into the lower one. The shells are
fairly large, roundly subtrigonal, white or porcellaneous
within, muscle mark not stained. Lower valve deep, not very
thick, ribbed and fluted on the widely distended margin. Upper
valve flat with rather broad horny scales. The lower valves
are in nearly all my specimens coated with cemented sand or
calcrete—at present I am disposed to refer them to O. Atlantica
and to the Welsh oyster of McAndrew.
Some shells received from Carlingford Lough are very tender
and delicately lamellated on the upper valve, the margins and
the valves being confluent. They belong to the group a figured
in Miss Massy's plate1, but appear to be larger examples if they
are of the same variety, measuring 31/2 by 3in. in length.
(Plate xvii., fig. 22.)
I have also some oysters from Cullanamore, Co. Sligo, which
I cannot place. They have a pointed ovate outline, and a
swollen or curved upper valve.
OSTREA CANTII sp. nov.
I have received from Mr. A. S. Kennard, F.G.S., a number
1 Irish Fisheries Scientific Investigation No. 11, 1913, pl. 11, fig. 6—7.