222 Proceedings of the Royal Physical Society. 
Family MyriLipé@. 
Mytilus, Mytilus edulis, Linne. 
Linne. 
Mytilus edulis, Linn., Syst. Nat., p. 1157. 
na ie F, and H., vol. ii., p. 170, pl. xlviii., figs. 1-4. 
58 5 Jeff., loc. cii., vol, i.;-p. 104;-vol. Ve, pk, =e 
fig. 1. 
Common. As a fossil it is found in all the Post-Pliocene 
clays of the British islands, and as a living species it is 
abundant everywhere. 
Modiolaria, Modiolaria marmorata (Forbes). 
Beck. 
Mytilus marmoratus, Forb., Mal. Mon., p. 44. 
Crenella marmorata, F. and H., vol. ii., p. 198, pl. xlv., fig. 4. 
Modiolaria marmorata, Jeff., loc, cit., vol.ii., p. 122; vol. v., pl. xxviii., 
ng, i, 
Rare. This species does not appear to be very common as 
a fossil; it is recorded from the estuarine clays of Belfast and 
Larne Lough in Ireland, from the Red and Coralline Crag in 
England. 
As a living species Modiolaria marmorata is found on all 
the British coasts, attached to old shells or imbedded in the 
skin or outer integument of ascidians. 
Family ARCID#. 
Nucula, Nucula nitida, G. B. Sowerby. 
Lamarck, 
Nucula nitida, Sow., Conch. Ill. (Nucula), p. 5, fig. 20. 
ra * F, and H., vol. ii., p. 218, pl. xlvii., fig. 9. 
eg bb Jeff., toe, cit., vol. ii, p. 1495 vols vs, ply mee, 
fig. 3. 
Not common. It has been obtained as a fossil at 
Cocklemill Burn, near Largo, and in the deposit at 
Paisley. 
This species is found living on most of the British coasts 
but nowhere abundantly. 
