The _Strombus gigas_, or “Fountain-shell,” occurs in great numbers in the West Indies, and is a very heavy solid shell. It is a favourite ornament for rockwork and fountains in gardens, and, like the Helmet-shells, is used for cameo-carving. It is also employed in the manufacture of porcelain, as many as 300,000 having been imported into Liverpool in one year for that purpose. [Sidenote: Cases 51–52.] The Scorpion-shells, or “Spider-claws,” as they are sometimes called (_Pterocera_), possess singular claw-like projections, which are developed on the outer lip of the shells. [Sidenote: Cases 53–54.] The “Trumpet-shells” (_Lotoriidæ_) have varices or strengthening ribs at intervals, like the Murices; the largest species, _Lotorium variegatum_, is used by South-Sea Islanders as a horn or trumpet. A hole is made in the upper part of the spire to blow through, and the sound produced can be modulated or varied by inserting the hand in the aperture or mouth of the shell. [Sidenote: Cases 55–56.] The “Helmet-shells” (_Cassididæ_) are used for cameo-carving; they consist of differently coloured layers, so that the ground-colour of the carving is of a different tint from the subject engraved. The most artistic shell-cameos are produced in Italy, whence the art has been introduced into France and England. The _Cassis madagascariensis_ (Fig. 12 on p. 19) is in special request by shell-carvers on account of the strong contrast of the white upper layer with the dark ground beneath. Extinct forms of _Cassis_ are found fossil in Tertiary formations, but none of them equal in size the largest living species. [Sidenote: Case 57.] The “Tun-shells” (_Doliidæ_) are remarkable for the globoseness of the shells, which are covered with very regular revolving ribs. [Sidenote: Cases 58–60.] The _Fasciolariidæ_ contains two of the largest living Gastropods: _Megalatractus aruanus_, from North and West Australia, and _Fasciolaria gigantea_, which is found off the coast of South Carolina, and attains at times a length of two feet. [Sidenote: Cases 61–64.] The Mitras (_Mitridæ_) are great favourites with shell-collectors, on account of their beautiful colours and varied sculpture. There are about 600 living species already known, and between one and two hundred have been found in a fossil state. Shells of this group, like the _Fasciolariæ_, are distinguished by a few plaits or folds on the inner side of the aperture (the columella). Mitras are almost exclusively found in tropical or subtropical regions, the majority being met with either at low-water mark or in comparatively shallow water. [Sidenote: Cases 64–66.] The family of _Buccinidæ_ also contains a very large and various assemblage of forms. Among them may be mentioned the Whelks (_Buccinum_). (See Fig. 13 on p. 19.) [Illustration: Fig. 12. _Cassis madagascariensis_, with cameo engraved upon it. Side table-case B. ] [Illustration: Fig. 13. The Common Whelk (_Buccinum undatum_).