02, 3. P. varius, Linn. (Ostrea.)—P. monotis.—Brit. co. generally, 3 to 35 fath.; C. Vertically elongate; auricles very unequal.
04. P. niveus, Macgillivray.—Scotland, R. (15 fath.) Ribs more numerous than P. varius; white.
05, 6, 7. P. opercularis, Linn. (Ostrea.)—O., and P. subrufus, pictus, lineatus (var. f. 6), and sanguinea.—Brit. co. generally, 5 to 100 fath., C. As broad as long; ribs rounded.
08. P. Audouinii, Payraudeau.—P. opercularis, var., B. Moll.—Ribs angular and squamose.
09, 10. P. danicus, Chemn.—P. and O. pes-felis, glaber, triradiata, adspersus, septemradiata, etc.—Several Scotch localities, 25 to 90 fath., Mc. Very variable, extreme vars. f. 9, 10. Auricles more equal than P. tigrinus.
11, 12. P. tigrinus, Müller.—P. obsoletus, domesticus, lævis, parvus, etc.—Brit. co. generally, 12 to 60 fath., C. Variable; one auricle minute, the other large and ribbed.
13. P. maximus, Linn. (Ostrea.)—P. vulgaris.—Brit. co. generally, 3 to 40 fath. The common eatable Scallop. Valves unequal.
14. P. similis, Laskey.—O. and P. tumidus.—Fr. Forth, Isl. Man, Lerwick, Cape Clear, etc., Mc. Minute, smooth, with undulating marks.
15. P. striatus, Müller.—P. aculeatus, fuci, etc.—Scotland, C.; England, R.
16. P. furtivus, Lovén.—Zetland, Guernsey, etc., 40 to 50 fath., Mr. More rounded, and with auricles less broadly based than P. striatus.