BRITISH OYSTERS : OLD AND NEW. 189
on the lower valve, the ribs varying in number and breadth,
the lower valve rather shallow; the upper valve flat, having the
concentric laminae closely appressed or but little raised; colour
a uniform deep or brownish buff, margins of valves plain; in-
terior an opalescent white, with a white scar of the adductor
muscle.
The same type is present in the Aldborough marshes, and the
Roman coast encampments, the Walton-on-the-Naze raised
beach, the alluvial flats at Norwich, and as far back in time as
the March Pleistocene silts. They show the original oyster
in this area to have been of Rutupinian type (Plate xiii., fig. 7).
Frank Buckland defined a "native" as a thorough-bred
oyster, its geographical limits extending from Harwich to Margate
at or about the mouth of the Thames, and indigenous to the soil.
Most of this district is under cultivation, and it is only here
and there that a few natural freely-fished beds are found; the
cultivated area includes the Colne, Faversham, Whitstable,
and Medway, but the brood has been so often replenished, that
the original type has been nearly lost. The Milton oysters, true
Rutupinian, are perhaps the purest of the East Coast breeds.
The present "Colchester" natives are the result of careful selection
and do not represent the aboriginal species or variety. The
South Coast from Dorset eastwards to Colchester has been
virtually peopled from France and the mid-Channel, and hardly
an aboriginal native is left, and only a few deep-sea shells, mostly
of large size, are now to be had.2
The continual waste of the coast line by denudation is partly
responsible for the scarcity of oyster beds off the Norfolk coast
beyond Burnham and Happisburgh. Although from the recur-
rence of names, such as Oysterness, on the Humber Estuary
their former presence may be inferred, the shell is not given in
Wood's list of the marine Mollusca of the Yorkshire coast (Hull
Museum Publication, No. 91, 1912), the bulk of the shells found
at the holiday resorts on that line of country being mostly
American Blue-points, Portugese, or importations. For many
years before and even after 1820, the extensive oyster banks off
Happisburgh, Norfolk, now almost exhausted, yielded a never-
2 Solent oysters grow very large. Philpots mentions one he bought which was
61/4in. long by 51/2in. broad, and another from off Christchurch which was 7in. by 7in., and
weighing 31/2 pounds. I have had them from off Newhaven nearly as large.