beak and mouth of several give them no small resemblance to the heads of certain birds, thus one is called the thorny woodcock,' another the snipe, &c.

2

At the first blush an inquirer into the use of these spines and other arms of shell-fish, would imagine that their object is defence, yet when he is told that those which are most remarkable for them, are themselves predaceous animals; and that the herbivorous shell-fish are usually not distinguished by any thing of the kind, he seems to hesitate as to what conclusion he shall draw. It may be observed, however, that the tribe most distinguished for these arms, the rock-shells, are not so remarkable for their size as many others which live by prey, as the strombs, the helmet-shells, and the tritons, so that their armour may sometimes prevent one of these from boring their shells, and inserting its proboscis into them.

The tribe we are now considering, the rockshells, were in high esteem from the earliest ages on account of the die that some of them afforded, and cloths died with it bore a higher price than almost any other: more than one species, however, yielded anciently a die; one, according to Bochart, a glaucous or azure colour, as he interprets it, and the other purple. But

Tyrian purple is no longer in request. I could say much, observes the author just named, upon the finding, fishing, and method of dying of the purpura, about the price formerly enormous, nearly equalling that of pearls, a single shell, according to Aristotle, selling for a mina or about 31. concerning the time at which it began gradually to grow out of fashion, and at length to be wholly neglected: so that now it is never used, and no one knows the method of preparing it. In fact, the cochineal seems to have supplanted it, but it would surely be an object of great interest to re-discover the Tyrian rock-shell, as well as that which yielded the azure colour, and ascertain how far they deserved, especially the former, the high encomiums bestowed upon them, and to deck imperial shoulders. The shells are probably still in existence on the coast of Palestine. It was the custom to crush the shell as soon as taken, for if kept the animal was wont to vomit its flower, as the purple die was called by Aristotle. This great philosopher thought the purpura lived six years, as the adult animal had six whirls in its shell, and he supposed one to be formed annually. He gives a detailed history of these animals, of their congregating in the spring, and of their forming a kind of comb, like bees; he also mentions several kinds of them, that the small shells were bruised, and the animal extracted from the large ones;

that the die lies between the neck and what he denominates the poppy. It is found, by Cuvier, to be placed above the neck by the side of the stomach. Plumier relates that a shell-fish of this genus squirts out its fluid in a stream, whenever molested, which renders it probable that its object is defence.

Aristotle mentions the operculum of the purple, and also the proboscis, or tongue as he calls it, which he describes as longer than the finger, and protruded from under the operculum, with this it feeds, and with it can pierce shells, and will attack even those of its own kind; this agrees with modern observations, adding that the tongue is terminated by a sucker armed with short tentacles. Aristotle also observes, an observation confirmed likewise by modern investigators, that these animals bury themselves in the sand like the pectens. This learned naturalist also states that shell-fish at certain seasons hide themselves, snails in the winter, and the purples and whelks for a month during the dog days.

The die of the purple is mentioned in scripture as well as that of the coccus, and was used as such in the time of Moses. It is said also to be used at this time in India and America to dye small pieces of stuff, but in no place is it an important object.

Having given so long an account of the rock

shells or purples, I shall not have occasion to dilate upon any of the remaining genera, but shall merely notice a few peculiarities that some of them exhibit.

The Cowries are a tribe long known and admired for their beauty and polish, and one species' forms the current coin in many parts of Africa, and many Asiatic Islands. Some remarkable facts distinguish their history; from the form of their shell and of its aperture, its increment could not take place in the usual way, these animals, therefore, are furnished by their Creator with a remarkably ample mantle, the wings of which cover half the shell, and thus it is gradually thickened, and changes and variations in the colour take place that have puzzled conchologists to distinguish a species from a variety. At certain times the animal is also stated to quit its shell, and form itself a new one more appropriate to its size, a circumstance related by Aristotle of the Buccinum.2

Volutes are another polished tribe of shells, which are probably formed by the mantle as in the Cowries-they are particularly distinguished by having no operculum. The jet volute is viviparous, and its young when excluded are said to have shells an inch long. These probably are more exposed to enemies than the

young of other shell-fish. They form an important article of food to some African nations.

Before I close this account of these predaceous Molluscans, I must observe, that they have two distinct sexes, and consequently male and female shells. The genuine hermaphrodites are confined to the bivalves, for in the univalve hermaphrodites two individuals are necessary for re-production, and therefore those form a distinct link between the true hermaphrodites that impregnate themselves, and those that have distinct sexes. So gradual are the steps by which the Creator passes from low to high. First, animals are re-produced without sexual intercourse, as in the polypes; then the two sexes are united in one body, and suffice for their own impregnation-next follow two sexes in the same body, which cannot impregnate themselves, bringing us at last to distinct sexes, or unisexual individuals.

4. Lamarck's fifth family, the Heteropods, I introduce here because, being univalves, they appear to connect that tribe with the Cephalopods forming his fourth order, but which from the discovery of the animal of Nautilus Pompilius, so admirably described by Mr. Owen, being further removed from the other Molluscans, and the animal of the Heteropods having a proboscis and only two tentacles, seems inter