220 THE ESSEX NATURALIST.
remaining in the shell of one of the valves. This is the largest
member of the Rutupinian group, and seems to be confined to
Scotland and N.E. Britain, but not exclusively to this area.
The tincta variety (pl. xii., fig. 4), I gather from Mr. Calder-
wood's notes and specimens, abounds not only in the Sound of
Scalpa, but also in Skye and on the west coast of Mull (Loch na
Keal). With him I think they belong to the Rutupina group
of the south-east of England, with which they agree in size and
shape, mainly differing in the internal colouring. This, however,
may be a local peculiarity as I have noticed it in other western
shells, and in all these localities the immature shells are ovate.
the anterior margin becoming pointed in later life.
I have not as yet found any intervening locality for this type
between the Eastern Counties of England and the Western Isles.
Its presence in a Pleistocene deposit at March is a strong point in
favour of the antiquity of the type.
I have lately found in some Roman debris sent me by Mr.
S. H. Warren, two or three examples of the O. Cantii referred to
in p. 206 (ante.)
Erratum.—Will readers kindly transfer the ascription on
p. 205 of pl. xvi., fig. 17, from O. tenbiensis to the Helston shell
referred to on p. 208 to which it properly belongs ?
EXPLANATION OF PLATES.