214 THE ESSEX NATURALIST.
inclining to the left ; ligamental area curved, deep and narrow.
It varies in contour from ovate or subtrigonal to a nearly diamond
shape. The costae vary from close set bifurcations to wide and
almost imperceptible swellings. Height of full-grown shell
70 mm., breath 65 mm., but no two are alike in their proportions.
Some of the shells are much produced on one side, and the
lamellae are at times considerably expanded and all seem to
have been attached at one time.
The Holmes collection in the Norwich Castle Museum con-
tains three species (four examples) of Corsican oysters, reported
as from Caldy Island and Tenby, but possibly wrongly localized,
i.e., O. cyrnusi, O. cochlear, and O. Diana (O. boblayi, B.D. & D.).
When this fine collection was being built up some fifty years ago,
a Corsican, M. Jean Susini, mentioned by Jeffreys, was con-
stantly receiving small parcels of shells from the Island to dispose
of, and I think it probable that the above shells may have
been admitted into the collection in error, as being rare or beautiful
specimens. O. cochlear has been dredged in no fathoms 40 miles
off Valentia in West Ireland (Proc. Zool. Soc, 1879, p. 555).
OSTREA CYRNUSI, Payraudeau.
Payraudeau gives two figures of his species, one with a deep
under valve, the other with it nearly flat, as is my own Corsican
shell. Requieu has made two varieties of Payraudeau's species,
calling his fig. 1 O. obtusa, fig. 2 O. rostrata. The Holmes shells,
the longest measuring 120 by 70 mm., belongs to the latter group
of large, thick, ovate or oblong forms, with a moderately long
beak.
Messrs. Bucquoy, Dautzenberg and Dollfus regard it as a
simple sub-variety of Ostrea lamellosa, only differing in its straight
form and prolonged beak. Carus and Fontannes make it the
same. H. and A. Adams and Monterosato deal with it as a
separate species. Cerulli-Irelli figures a shell under this name
(Palaeont. Ital., vol. xiii., plate iii., fig. 4), as a var. of O. edulis,
but the whole group of which the shell figured by the latter may
be taken as a type is one in which any rhomboidal, plain-margined,
non-costate oyster may find a resting place. The species is a
very unsatisfactory one in itself. O. cyrnusi may perhaps be
better considered as representing a group of allied forms
rather than as a distinct species.