BRITISH OYSTERS : OLD AND NEW. 203
with the fossil O. lamellosa, or the northern O. hippopus. I
do not know Brocchi's shell as a recent species, and Jeffreys,
when revising Brocchi's collection, passed it over as O. edulis,
as might be expected (Q.J.G.S., 1884).
VAR. ESTUARII var. novo.
Hyndman (Rep. Brit. Assoc, 1857, p. 225), remarks that
oysters were abundant in Belfast Bay from low water to 25
fathoms, and were taken by line at 45 fathoms off the Copeland
Islands at the mouth of the bay, the oysters known as "Carrick-
fergus Oysters" attaining a great age. Unfortunately these
large oysters are no longer procurable, the Belfast Lough not
paying to fish. The ancestors of these molluscs abound in the
Estuarine Clays in the Alexandra Dock, Belfast, and in the rich
shell-banks at Magheramorne, Lough Lame. Bedded originally
at about 5 fathoms deep in the Thracia convexa zone, as suggested
by Mr. Praeger, they now exhibit in Lough Larne a thick mass
of shells. They occur mostly in pairs, but single valves of great
weight are common, one now in the Belfast Museum weighing
five pounds, and of corresponding size. A full account of the
Estuarine Clays and their magnificent fauna may be found in
Mr. Praeger's valuable and exhaustive report on the N.E.
Estuarine Clays (Proc. R.I. Acad. (iii.) v. 2, no 2, 1892). The
estuarine shells vary in shape, looked at from the outside, from
ovate, trigonal, or broad-shouldered, to a curved or crescentic
outline. Inside, this variation is less apparent, which is largely
due to the spread of shelly growth at the sides.
As this race, or group, so far as I am aware, has not been des-
scribed in detail, a brief notice may be useful (plate xiv., fig. 10).
Sculpture (lower valve) strong, well defined costae traversed
by broad lamella, rising into tubular ridges on the costae in the
earlier growth, these dying out as the shell advanced in age and
thickness, leaving a plain, non-indentate margin. The shell
seems to have grown normally to a length of 3-4 inches before
the alteration in sculpture and lateral deviation ensued. The
ligamental area varies much, where the shell is much drawn out
it may be as much as 30 mm. in length and 15 mm. in breadth.
The scar is large, and in old shells is cut off below from the rest
of the valve by a thick growth of shelly matter (see Chambrage,
Of Oysters, p. 80