"The beautiful genus _Harpa_, harp-shell, is remarkable for its elevated ridges on the back of the shell, its large aperture, and its fine colouring. They are East Indian shells. _H. ventricosa_ is a common species. _H. nobilis_ is very fine, and also _H. costata_. "Equally well-known are the Tuns, _Dolium_, by their globose form, the right-margin toothed, and a canal below. They reach a large size, and are light shells in proportion to their bulk. _Dolium galeum_ is sometimes the size of the human head. _D. perdix_ is a choice species. [Sidenote: DOLIUM. BUCCINUM. EBURNA.] "_Buccinum_ contains some British species, as _B. reticulatum_, (Plate 7,) _B. anglicanum_, _B. undatum_, which is very common. In connexion with this species I wish you to know that a marine substance, called by sailors _sea-wash balls_, by others sea-sponge, and extremely common on all our sea-coasts, is the egg-cases of the _Buccinum undatum_. The mass is remarkably light, and composed of numerous little cells, each of which has an opening. The colour varies from yellow to white." "I know them well," exclaimed Lucy, "how often I have asked the name of those nests, but never could I obtain a reply worth having! And now, father, give me leave to interrupt you a few minutes. What are those black, stiff, marine substances, with a horn-like projection at each of the four corners; they are all hollow, and open at each end, I think, and usually inflated?" "The egg-cases of the scate." "Thank you, father, I will examine them again carefully when I am at the sea-side." "The genus _Eburna_," continued Mr. Elliot, "is remarkable from the smoothness of the shells. _E. spirata_, the Joppa whelk, has the whorls deeply channelled. (See the Frontispiece.) The columella is umbilicated, and has a canal beneath it. [Sidenote: TEREBRA. COLUMBELLA.] "The _Terebra_ genus is turreted; very acute at the apex. (Plate 9.) "The family _Collumellaria_ is next in order. The _canal_ now disappears at the base of the shell, but there is a slope and folds on the columella. We have reached the large genus _Voluta_ of Linnæus, greatly reduced by withdrawing the following genera: _Columbella_, } _Mitra_, } _Cymba_, } _Melo_, } _Voluta_. _Voluta_, } _Marginella_, } _Volvaria_, } "The shells of _Columbella_ are of small size; two species are very common in collections. _C. mercatoria_ is a little shell striated transversely; the outer lip is thickened in the middle, and toothed; the columella is plaited: the animal is furnished with an operculum. "_Columbella nitida_ is another pretty species, smooth and shining: you may perceive the generic marks if you look closely--two small folds on the pillar-lip, and the swelling, toothed, outer margin. They are all West Indian marine shells. [Sidenote: MITRA. CYMBA. MELO.]