A = Living species but found fossil in some tertiary deposit. B = Mammilliferous crag, and glacial deposits. C = Red crag. D = Coralline crag. E = Eocene. +----------------------------+---+---+---+---+---+ | Name. | A | B | C | D | E | +----------------------------+---+---+---+---+---+ | Balanus tintinnabulum | * | | * | | | | calceolus | * | | | * | | | spongicola | * | | | * | | | concavus | * | | * | * | | | porcatus | * | * | * | | | | crenatus | * | * | * | * | | | Hameri | * | * | * | | | | bisulcatus | | | * | * | | | dolosus | | * | | | | | inclusus | | | | * | | | unguiformis | | | | | * | | Acasta undulata | | | | * | | | Pyrgoma anglicum | * | | | * | | | Coronula barbara | | | * | | | | Verruca Strömia | * | * | * | * | | | Scalpellum magnum | | | | * | | | quadratum | | | | | * | | Pollicipes reflexus | | | | | * | +----------------------------+---+---+---+---+---+ | Total, 18, recent and } | | | | | | | extinct, found fossil in } | 9 | 5 | 8 |10 | 3 | | Great Britain, in some } | | | | | | | tertiary deposit } | | | | | | +----------------------------+---+---+---+---+---+ As affording some standard of comparison by which to compare the number of fossil species, at any period, in relation to the number of species probably existing in the neighbouring seas during the same epoch, I may state that there are now living and propagating on the shores of Great Britain, 18 species belonging to the three Families included in the above table. I have not counted three species, in the genera Alcippe and Conchoderma, which, from the minuteness of their valves, it is hardly possible would be found fossil. On the other hand, I have included in the 18, five species of Lepas, which from floating and being oceanic, are more likely to be cast up on beaches, than to be imbedded in sedimentary deposits; so that 13 would, perhaps, be a safer number, as a standard of comparison. Now in the coralline crag, which seems to have been eminently favorable for the existence and subsequent preservation of Cirripedes, and which has been so well worked, only nine fossil species, as may be seen in the table, have been as yet discovered. Sub-Family--BALANINÆ. _Shell with the rostrum having radii, but without alæ; lateral compartments all having alæ on one side and radii on the other side; parietes generally either porose, or longitudinally ribbed on their inner surfaces._