Cuttle Fish, and all other molluscous animals, can only be preserved in spirits. The same observation applies to the animals which inhabit that numerous tribe called Testaceous Shells. They must be detached from the shells, and put into spirits, while the shells themselves must be preserved, independent of the animal.
Shells naturally arrange themselves under three distinct heads : Marine, Land, and Fluviatile, or Fresh Water.
Marine shells are only to be expected perfect, when procured in a living state. The way to extract the animal is to pour some warm water on it; but, if too hot, it is liable to crack the shells. When the animals are dead, they can easily be pulled out with any hooked instrument, or fork, or if the animal is small, by a common pin. This applies to all marine shells; whether univalve, bivalve or tubular. It is of great consequence to preserve the ligament of bivalve shells entire, so that the valves may not be separated. The animals of laud and fresh water shells are killed by the same means, only that the water requires to be very hot.
Unless the shells are covered with extraneous matter, it is not necessary to clean them. Marine shells are, however, very liable to be incrusted with other marine bodies, particularly with serpula and balani, etc. These must be started off by means of a sharp instrument; an engraving tool is well adapted for this purpose. This must be done with great caution, in species which have spines, and other excrescences, as they are very liable to be broken. Should any of the calcareous matter still adhere, this must be removed, by applying to it a very weak mixture of muriatic acid and water, applied with the point of a quill, and then plunged into water, and allowed to remain till the acid is quite extracted. But on no account whatever attempt to eradicate these parasitic bodies by means of acid, or acid and water alone, as the chances are that the shell will be completely destroyed by their application. We have seen many fine and valuable shells destroyed by an injudicious application of acids - they should never be used when it can possibly be avoided. We have, on the other hand, seen shells which were so completely enveloped in calcareous crust, that it was impossible to trace their external surface, most thoroughly cleared of all this, without being touched at all by acids, the whole being removed by a small knife or other sharp instrument; and these, in many cases, having long and tender spines externally.
Nothing can be more monstrous than the application of pumice-stone, which some recommend, for polishing shells; as is also the use of tripoli, rotten-stone, and emery. Neither do we approve the application of varnishes, as such shells never have their natural luster.
If a shell is found dead upon the beach it is probable that it will have undergone a certain degree of decomposition, that is, it will have parted with part of its animal matter, and consequently the colors will have faded and the surface present a chalky appearance. To remove this take a small proportion of Florence oil and apply it to the surface, when the colors which were invisible will appear. When completely saturated with oil let the shell be rubbed dry and placed in a cabinet. Oil may also be applied after acid has been used, and it will be found extremely useful when applied to dry the epidermis, which it will prevent from cracking or quitting the shell entirely, which it frequently does.
Whether marine shells are procured in a living or dead state, a very necessary precaution is to immerse them in pure tepid water after the animal has been extracted, and allow them to continue in it for an hour or two so as completely to extract any salt or acid which may be in them.
Fresh water shells are liable to a calcareous or earthy incrustation, which must be removed by immersing them in warm water, and afterwards scraping and brushing them with a nail or toothbrush. Much nicety is necessary in cleaning these, as their great thinness renders them, in general, liable to be broken. A little Florence oil will improve the appearance of the epidermis and render it less liable to crack.
Land shells seldom require any cleaning except washing in water, as they are not liable to incrustations of any kind.
When shells are perforated by marine animals, or otherwise broken, if the specimen is rare, it is desirable to remedy these defects as far as possible; they may therefore be filled up, or pieces added to them with the cement, which may be colored when dry to its original state.
Of Polishing Shells. Many species of marine and fresh water shells are composed of mother-of-pearl, generally covered with a strong epidermis. When it is wished to exhibit the external structure of shells, the epidermis is removed and the outer testaceous coatings polished down till the pearl-aceous structure becomes visible. It has been a common practice to remove the strong epidermis of shells by means of strong acids, but this is a hazardous and tedious mode of operating. The best method is to put the shells into a pan of cold water with a quantity of quicklime and boil it for two to four hours, according to the thickness of the epidermis. The shells afterwards must be gradually cooled, and some strong acid applied to the epidermis, when it will easily peel off. Two hours are sufficient for the common muscle being boiled. The shells are afterwards polished with rotten-stone and oil, put on a piece of chamois leather.
The epidermis of the uno margaritifera is so thick that it requires from four to five hours boiling. After the epidermis has been removed, there is beneath it a thick layer of dull, calcareous matter, which must be started off with a knife or other sharp instrument; this requires great labor, but, when accomplished, a fine mother-of-pearl is exhibited which adds an agreeable variety as a specimen.
Various turbos and trochuses are also deprived of their epidermis and polished with files, sand-paper, pumice-stone, etc., till the pearly appearance is obtained; but all these modes are invented for disfiguring rather than improving the shells in the eye of the naturalist, and should never be resorted to except where the species is very common, in which case it is well enough to do so with one or two specimens to show the structure of the shells.
After the operation of polishing and washing with acids, a little Florence oil should be rubbed over to bring out the colors and destroy the influence of the acid.