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 (pi. 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 
Real). 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 0 . cantii referred to 
in p. 206 (ante.) 
Erratum.— Will readers kindly transfer the ascription on 
p. 205 of pi. xvi., fig. 17, from 0 . tenbiensis to the Helston shell 
referred to on p. 208 to which it properly belongs ? 
EXPLANATION OF PLATES. 
Plate 
XII. 
Fig. 
1. 
Ostrea edulis var. celtica 
Oransay 
Fig. 
2. 
,, edulis (typica) 
River Deben 
Fig. 
3 - 
,, edulis var hippopus 
Hartlepool Docks 
Fig. 
4 - 
,, edulis var. tincta 
Scalpa 
Plate 
XIII. 
Fig. 
5 - 
O. edulis var. rutupina 
Felixstowe 
Fig. 
6. 
O. edulis var. rutupina 
Forth Estuary 
Fig. 
7 - 
O. edulis var. rutupina 
March 
Fig. 
8. 
O. edulis var. celtica 
Shetland 
Plate 
XIV. 
Fig. 
9 - 
O. edulis, var. celtica 
Ramsey, I. of Man 
Fig. 
10. 
O. edulis var. estuarii 
Lough Larne 
Fig. 
11. 
O. cantii 
Herne Bay 
Fig. 
12. 
O. ed. var. estuarii (interior) 
Lough Larne 
Plate 
XV. 
Fig- 
13 . 
O. cantii 
Herne Bay 
Fig. 
14. 
O. Foulnessii 
Foulness, Essex 
Fig. 
15 - 
O. sp. 
Selsey 
Fig. 
16. 
O. sp. 
Selsey 
