CYPRÆA.
BULLA.
"The shells of the genus Cypræa, cowry, are general favourites: the species are fifty-eight; one British, C. pediculus. C. moneta (Plate 1) is very common. The generic characters are, shell univalve, involute, obtuse, smooth; aperture linear, the whole length of the shell; effuse at both ends, toothed on each side.
"Look carefully at those three shells: do you perceive much resemblance between them? 'Not much, if any,' you reply, yet they are all of the genus Bulla. Here is B. lignaria, B. terebellum, (see Frontispiece,) and B. naucum. ([Plate 6.]) There are other forms, as the B. ovum, B. volva, the first somewhat like a cowry; but it is toothed only on one side of the aperture; the second has two long beaks.
"This genus is confessedly ill-determined. B. naucum and B. ampulla are examples of the common characters of the genus. The species are sixty-one.
VOLUTA.
BUCCINUM.
"Voluta is also a large genus, containing one hundred and eighty-six species. Shell univalve, aperture without a beak, and somewhat effuse; columella plaited. This latter character we meet with for the first time. Here is the common Voluta. ([Plate 6.]) The genus has been much diminished by forming other very striking genera out of it, as I shall soon show you, under the names of Mitres, Olives, Gondolas, &c. Voluta musica, the music-shell, is remarkable, and not at all rare.
"Buccinum is another large genus. The shell univalve, spiral, gibbous; aperture ovate, ending in a canal turning to the right, with a short beak; pillar-lip expanded. Species, one hundred and seventy-two.
"You must recollect that when the apex of the shell is turned downwards the canal turns to the right, when it is turned upwards the canal will be to the left hand. My example is Buccinum reticulatum, a very common species upon our own shores." ([Plate 7.])
"Is not this genus reduced by other authors?' asked Charles.