Marine Shells &c.
We have previously dealt with the preservation of the shell-less molluscs, and the soft bodies of the shelled species when such are required, so we will now see what should be done with the shells.
Numerous shells are often to be found on the sea beach—shells that have been washed in by the breakers, and from which the animal contents have disappeared, either by the natural process of decay, aided by the action of the waves, or by the ravages of the voracious or carrion-eating denizens of the sea; and although these shells are rarely perfect, having been tossed about among the other material of the beach, yet we occasionally find here the most perfect specimens of both univalve and bivalve shells in such a condition that they are ready for the cabinet, and these often include species that are seldom found between the tide-marks, or that are otherwise difficult to obtain.
However, the shell-collector must not rely on such specimens as these for the purpose of making up his stock, but must search out the living molluscs in their habitats and prepare the shells as required.
The molluscs collected for this purpose are immersed in boiling water for a short time, and the animal then removed from the shell. In the case of bivalves it will generally be found that the hot water has caused the muscles of the animal to separate from the valves to which they were attached, or, if not, they have been so far softened that they are easily detached, while it does not destroy the ligament by means of which the valves are held together at the hinge; but the univalve molluscs must be removed from their shells by means of a bent pin or wire. In the latter instance care must be taken to extract the whole of the body of the animal, otherwise the remaining portion will decompose within the shell, giving rise to the noxious products of natural decay.
The univalves have now simply to be placed mouth downwards on blotting-paper to drain and dry, when they are ready for the cabinet. If, however, they include those species, like the periwinkles and whelks, that close their shells by means of a horny lid (operculum) when they draw in their bodies, these lids should be removed from the animal and attached to their proper places in the mouth of the shell. The best way to accomplish this is to pack the dry shells with cotton wool, and then fasten the opercula to the wool by means of a little gum tragacanth or acetic glue.
Bivalve shells should, as a rule, be closed while the ligament is still supple, and kept closed until it is quite dry, when the valves will remain together just in the position they assume when pulled together by the living animal. The shells of the larger species may be conveniently kept closed during the drying of the ligament by means of thread tied round them, but the very small ones are best held together by means of a delicate spring made by bending fine brass wire into the form shown in fig. 44.
Fig. 44.—Spring for holding together small Bivalve Shells