Sr 
Sr 
OSTREA. 
OSTREAD A. 
One genus, with a single proteiform species, constitutes 
this peculiarly British family. Ostrea is the Lamarckian 
monomyal type. What has been said on the Anomiade and 
Pectinide renders further detailed remarks unnecessary. We 
will only observe, though the general form of the branchial 
laminz is similar to those of the Pectines, that they are in 
their composition very distinct ; the complete absence of the 
byssal foot is another important deviation, and in other re- 
spects it is eminently distinguished from Pecten; Ostrea is 
generally fixed by the under or convex valve, and has, if any, 
a very limited locomotion, whilst Pecten is almost always free, 
and can perform the most rapid leaps and movements. 
OSTREA, Linnzus. 
O. eputis, Ibid. 
O. edulis, Brit. Moll. ii. p. 307, pl. 54, (animal) pl. T. f. 1. 
O. parasitica, Auct. 
Animal orbicular, subcompressed, of a pale drab colour 
throughout ; mantle thin at the beaks, gradually thickening 
to the ventral range, entirely open, except a short dorsal 
area, and has no trace of siphons or sessile apertures; the 
margin is not reflected on itself as mm Pecten; there are two 
rows of tentacular filaments springing from cord-like offsets 
of the margin; the front one is furnished with very thick, 
short, white, blunt cirrhi, disposed in a disorderly double line ; 
the other is more within the shell, and has a simple series 
of short, pale brown filaments of different lengths; these are 
rarely seen exserted, from the habitude of the animal to keep 
the valves closed. The body, including the dark green liver 
with the icorporated cream-coloured ovarium, proceeds from 
the centre of the dorsal area on the anterior and posterior 
sides of the great subcentral muscle, at which point it termi- 
