BRITISH OYSTERS I OLD AND NEW. 
211 
The loss of the large horny plates causes the upper valve to 
sink into the lower, leaving exposed in a shell of 3 inches dia¬ 
meter a bare space of over J inch all round. This hiatus is 
■equally present whether the shell be one inch broad, or four. 
This habit of growth is common to many S. Western oysters, 
but hardly to the same extent. It may be an extreme 
variety of the next species, judging from some examples of the 
latter sent me by M. Ph. Dautzenberg recently. 
OSTREA SCAEVA (Valenciennes MS.) Monterosato. 
This beautiful shell is described by Miss A. L. Massy ( Fisheries 
<of Ireland Scient. Invest. No. 11, 1913), and is figured in all stages of 
growth on pp. 1-10, as 0. edulis, var. b. Poli, and subsequent 
writers, have called it 0. cristata, a name originally given by Born 
{ Mus. Caes. Vindob. 1780, pi. xii., fig. 3) to a shell that cannot 
be identified, and by Lamarck to a Senegalese species 0. atlantica 
(see ante). The lower valves are crossed by prominent lamellar 
•growth produced into broad and deeply arched fimbriation. 
The upper valve is irregular, usually swollen towards the umbo, 
but mostly sinks into the lower valve at the margins ; the horny 
lamellae are long, irregular in outline and very conspicuous and 
foliated. The foliated edges often give the appearance of slight 
dentation. In nearly every instance the shells have been 
attached to some extent. The colour is at times a vivid pink, 
and striped at the top,of the valve (plate xvii., fig.21). The name 
being preoccupied, Monterosato revived the name 0. scaeva 
in a Memoir on Mediterranean oysters (Ann. del Museo Civico, 
vol. vii., plate 1, fig. 1-3, p. 3), and the authors of the Roussillon 
memoir figure it as 0 . edulis var. cristata (vol. ii., figs. 1 and 2). 
I have not met with it in the English Channel, and only doubt¬ 
fully as a Selsey fossil. As a recent shell it is known from 
Bohuslar to the western Mediterranean, via. Galway and Jersey, 
but does not come farther east in Britain than Devonshire. A 
full-grown specimen averages length 2J inches, breadth 3 inches. 
Miss Massy (op. cit.) figures some fine Norwegian examples, 
quoting one as being 105 mm. from hinge to ventral edge. 
OSTREA STENTINA, Payraudeau. 
Prof. Kerr, of Glasgow University, has kindly sent me a 
number of oysters from Loch Sween, Argyleshire, quite unlike 
