Beautiful shells

by H. G. Adams

INTRODUCTION.

WHAT ARE SHELLS?

Dr. Johnson gives us no less than eight different meanings for the word Shell. First, he calls it ‘The hard covering of anything; the external crust.’ Second, ‘The covering of a testaceous or crustaceous animal.’ And here we may stop, for this is just the signification which has to do with our subject; so let us turn the sentence inside out, and see what we can make of it. We all know what a covering is—an outer coat, a case, a protection from injury, a husk, a crust, a—in short, a shell,—scyll or scell, as our Saxon forefathers called it; schale, as the Germans now term it. No Latin nor Greek here, but the good old Saxon tongue, somewhat rough and rugged, perhaps, but stout and sturdy, and honest and serviceable; a kind of language to stand wear and tear, like a pair of hob-nailed shoes, with little polish, but useful, yes, very useful! Well, we have got so far, now comes a hard word—Tes-ta-ce-ous, what can it mean? It is pronounced tes-ta-shus, comes from the Latin testaceus—having a Shell, and means consisting of, or composed of shells; so we find that a testacean is a shell-fish, and testaceology is the science of shells. Johnson’s second meaning of the word testaceous is ‘Having continuous, not jointed shells, opposed to crustaceous.’ So we find that some naturalists call those testaceous fish, “whose strong and thick shells are entire and of a piece, because those which are joined, as the lobsters, are crustaceous.”

Now some of the true testacean have shells in more than one or two pieces, and therefore this last explanation of the term is rather calculated to mislead a learner; but we shall explain presently wherein the difference consists between them, and the Crus-ta-ce-ous, or, as we pronounce it, krus-ta-shus, fish consists. Here is another long word, it comes from the Latin crusta, a word of many meanings, all having reference to an outer coat or covering. My readers know all about pie-crust, and have perhaps heard a surly, snappish, peevish person called a crusty fellow; they will now understand what is meant by a crustacean and crustaceology, that part of Zoology which treats of crustaceous animals. They constitute quite a large family, these ologies, and have a strange way of twisting themselves about, and exchanging limbs and features, so that one is puzzled at times to tell which is which. But here we have fixed two of them, called Testaceology and Crustaceology, twin brothers, and very much alike in their characteristics. Let us have a good look at them, so that we may know them again if we should lose sight of them for awhile. Now we will spell over the name of the first—

CONCHOLOGY.

Why, it is changed already? Has this science of shells then another name? Yes, and this is it, pronounced kong-kol-o-gy, and derived from the Latin concha, which means properly a shell-fish with two shells, joined by a hinge, as the oyster, the cockle, etc. This present volume then is a work on Conchology, the subject of it is Conchiferous, and whoever studies it will be doing something towards becoming a Conchologist.

So much for names and titles; but still we have the question to answer, What are shells? In a learned work called a Cyclopædia, we find it stated that “shell is the hard calcareous (that is chalky) substance which protects, either partially or entirely, the testaceous mollusks externally, or supports certain of them internally.” All this you will understand, except perhaps the word ‘mollusks;’ this is a term applied to soft-bodied animals, such as shell-fish, snails, etc., about which we shall have more to say as we proceed. By this we learn that all shells are not external or outer coverings, some are internal or inner supports for the soft, jelly-like bodies to which they belong, thus performing the duty of bones. An example of this is seen in the shell of the Cuttle Fish, called by naturalists Sepia, a description of which will be found further on in the book.

Shells are either Crystalline or Granular. Now look at those two words, they almost explain their own meaning. Crystalline shells are those which have more or less of clearness, transparency as we say, so that if held against the light it shews through them; they are sometimes called Porcellaneous shells, from their resemblance in this respect to porcelain, or chinaware; the Common Cowry, (Cypræa Tigris,) is a shell of this description.

Granular, or, as they are sometimes called, Concretionary shells, are the most hard and compact; it is in these that the substance called nacre, or mother-of-pearl, is mostly found. One of the commonest examples is the oyster shell; if broken across it will be seen to consist of very thin plates, or laminæ, as they are termed, closely packed together. The thinner these laminæ may be the more lustrous and beautiful appears the lining of the shell; that shifting play of colours which we call iridescent, from iris—the rainbow, is then brightest and most noticeable. A very remarkable substance is this mother-of-pearl; smooth, and shining, and delicately-tinted. Who would expect to find such a beautiful lining to the rugged, rough, dingy-looking oyster, or mussel shell? Truly these mollusks, some of them, live in gorgeous palaces. And the most curious part of the matter is that from the fluids or juices, of their own bodies, and from the chalky matter collected from the water, they are enabled to secrete or deposit such wonderfully-constructed habitations, which after all are little more than chalk. Burn a heap of oyster shells, or any other testaceous coverings, and you get lime the same as that produced by burning the white lumps from the chalk-pit, which lumps, by the way, are said to be composed wholly, or for the most part, of marine shells. This we should call cretaceous matter, from creta, which is the Latin for chalk, or calcerous, from calcis—lime. Granular shells you have been told are sometimes called concretionary, this is because they contain a large amount of this chalky deposit. The rock called limestone, geologists tell us, is composed entirely of fossil shells and mud, or what was once mud, dried and hardened, most likely by extreme heat, to the consistence of rock. Wonderful this to think of; huge mountains, and mighty masses, and far-stretching strata, forming a large portion of the crust of the earth, made up chiefly of the coverings of fishes, a great portion of them so small as to be scarcely visible to the naked eye.—Truly wonderful! But we shall have more to say upon this head when we come to speak of Fossil Shells, as well as on the subject of Pearls, in our chapter on the fish in whose shells they are chiefly found.