BRITISH OYSTERS : OLD AND NEW.
199
pointed, anterior margin straight or slightly incurved, sloping
to a rather produced margin about the lower third of the shell,
with closely appressed corneous growths, not extending much
beyond the margin, lower valve strongly ribbed with broad
costae, and well defined lines of growth. Surface irregular, area
of ligament shallow. Height 70 mm., greatest breadth 65 mm.,
slight and very thin scar (plate xii., fig. 4).
I do not think that Jeffreys' note "attached at every stage"
of growth is quite exact, certainly it is rarely so in the only
examples I have seen. A Skye example in the Holmes Collec-
tion, Norwich Castle Museum, shows a conical shell, very equal
sided, graduating to a pointed central apex, 33 mm. long, 23 mm.
broad, possibly an immature growth.
The authors of the Roussillon memoir refer to Jeffreys' shell
as a coloured form of his O. rutupina, but do not seem to write
from personal acquaintance, and no other writers have noticed
it, but it seems to be a well-marked form.
VAR. RUTUPINA Jeffreys.
Jeffreys describes this variety (B.C. ii., p. 39) as small,
transversely oval, and of a regular shape. Coasts of Essex and
N. Kent. In a semi-cultivated state well known in this country
as "Natives." It is found in its greatest purity at Milton,
the Reculvers, and Pegwell Bay, Kent, in lineal descent from
pre-Roman times. It never grows very large, only 45-60 mm.
long. Shell rather solid, strongly ribbed on the lower valve.
Upper valve convex, shape mostly subtrigonal, occasionally
much produced on the anterior side, with incurved beak.
Reeve's figure (Conch. Icon., Ostrea, xviii., pl. v., fig. 8,b), is that
of a "small, regularly formed, not very flaky" variety.
The Firth of Forth oysters, the old Scottish Pandoures,
now almost extinct, are of this type, and form a group by
themselves (pl. xiii, fig. 6), trigonal in outline, the anterior side
curving in as it descends towards the margin, carrying occasion-
ally a spread of shelly matter like an ear near the beak,
giving the shell a rounded or very ovate appearance. Lower
valve costate, better displayed in some specimens than in others,
top valve very scaly, loose, not depressed as usual, beaks small
and frequently acute. Shell very flat and light. Thickness,
back to front, 20 to 30 mm., height 85-90 mm., breadth 80-