186 THE ESSEX NATURALIST.
Bohuslan oyster and others from N. Jutland agree with our
North Sea Hasborough shells in having a more efflorescent
lamination than is usual with the East coast oyster.
The "human" history of the subject goes back to the caves,
middens and shell-banks of Azilian and later days, on the northern
coasts at Dunagoil, Colonsay, Oransay, Ardrossan, Caithness, the
Shetlands, N.E. Scotland and elsewhere. Many of these are
of large size. Of two mounds on the shores of Loch Spynie,
one measures 240 by 90 feet, the other 178 by 90 feet. Another
at the Creggauns in Co. Galway (more recent) is nearly as large..
That at Oronsay has been beautifully described and illustrated
in Tr. Soc. Antiq. Scotland, vol. 48, p. 52, by Mr. Henderson
Bishop, to whose courtesy I owe a fine series of valves (Plate xii.,
fig. 1). The mound of Cnoc-sligeach in Oronsay now stands
some 35 feet above the original sea-level, and according to
Prof. Scott Elliott was accumulated 6000 years B.C., when
the hunting tribes, finding flesh-meat to be getting scarce, took
to fishing. The shells are of large dimensions, one measuring
120 by no mm. The lamination on the top valve is very closely
set and flattened; on the lower valve the ribs are very strong
and equal in thickness to the interspaces, with a shallow ligamental
area, slightly curved but of moderate breadth and length.
The genus has now died out in this district, but at Colonsay
banks of dead shells may be seen on the beach between tide marks.
The value of the British oysters as food became apparent
to the Roman settlers in Britain as early as A.D. 50, and there is 
hardly a Roman site, station, or town where the shells are
not present in abundance. The small Rutupinian mollusc was
the one mostly in demand for exportation, but the Romans
also utilised the larger and deep sea form whenever procurable,
especially at Verulam, Folkestone and about London. The
shells found in the dwellings of this people are a very good
index to the type of shells then living on the nearest coast line;
thus at Silchester they are of the Channel or Southampton type,
at Caerwent and Uriconium they are of the larger or Welsh
series, and on the Eastern coast mostly Rutupinian.
Our Saxon forefathers do not seem to have been interested
in Oysters, as their shells are seldom or never found in or about
Saxon sites.
Although the oyster was abundant all round our coasts prior