| 68 ’ MOLLUSCA. 
| Shells naturally arrange themselves under three distinct 
heads ; Marine, Land, and Fluviatile, or Fresh Water. 
Marine Sheils are only to be expected perfect, when pro 
cured in a living state. The way to extract the animal, is te 
pour some warm water on it; but, if made 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 Land 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 any 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, &c. 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, at- 
tempt 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 instru- 
| ment; 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 imry. Neither do we 
