And with this curious piece of mechanism the little Winkle works away and cuts down swathe after swathe of the minute vegetation, just as a mower does the meadow grass; only the mollusk eats as he goes, and so gets payment for his labour; the man has it in another and to him more useful form. We might tell a very long story about these Tops and Winkles, which are nearly related to each other, but must now pass on to describe the rest of the shells on Plate IV, which are the Perspective Solarium, (_S. perspectivum_,) Fig. 5, the generic name comes from _sol_—the sun, and viewed perspectively, that is, in such a position that the whole top of the shell is at once presented to the view, looking like a flat surface, it presents a circular appearance, marked with rings and rays like representations of the sun sometimes do. The Variegated Solarium, (_S. variegatum_,) Fig. 6, is a small but very pretty shell, somewhat rare. The mollusk is remarkable on account of the singular shape of its operculum, which differs from that of all other species; it is of a cone-shape, and covered from top to bottom with what are called membranous lamellæ, that appear to stand out like little shelves winding up spirally. This singular form of operculum has been long known to naturalists, but it is not until lately that they have discovered to what species of testacean it belonged. Let us here explain that _operculus_ is the Latin for a cover or lid. CONES, VOLUTES, MITRES, AND OLIVES. These are names given by collectors to certain classes of univalve shells distinguished by peculiarities of formation, more or less distinct. We shall describe two or three of each, that our readers may have some idea of the meaning of the terms which are often used by those who speak or write on conchology. The family of Cones, called _Conidæ_, is an extensive one, considerably above two hundred species having been discovered. Many of them are very beautiful both in shape and colour, so that they are highly valued by collectors; they are principally found in the southern and tropical seas, upon sandy bottoms, at depths varying from a few feet to seventeen fathoms. The shells are generally thick and solid, rolled up, as it were, into a conical form; the most familiar illustration that can be given of this form is a sugar-loaf, which all these shells more or less resemble in general outline, as thus— [Illustration] Cones are either plain or coronated, that is, crowned, having rows of projections round the top of the shell, like the second of the above figures; and this forms a mark of division into two classes, although these classes often run, as it were, one into the other; some plain cones having slight irregularities of surface, and some crowned ones being very nearly plain.