not unlike a contracted purse, is in front, between the smaller tentacula; and within its folds are situated six or eight horny lamina or erect teeth. Under this lie the stomach and intestines, and the tendons, by which the animal adheres to the shell.

OF THE TEREDO TRIBE*.

There are not more than four known species of Teredo. Of these, two are found in holes, which they perforate in wood; a third, in the seed-vessels of a plant which grows in the East Indies, and called, by Linnæus, Xylocarpum Granatum; and the fourth, (the Gigantic Teredo,) in mud at the bottom of the ocean, on the coast of the island of Battoo, near Sumatra. The shells of the latter are sometimes betwixt five and six feet in length.

These animals were formerly arranged with the more simple of the univalve shells, but their proper place is certainly among the multivalves.

THE SHIP-WORM t.

Great numbers of these destructive worms, which are supposed to have been introduced from India into Europe, are sometimes found in the sides and bottoms of

The shell of the Teredo has two principal hemispherical valves, truncated and open at the end; and two small lanceolate accessory valves, remote. The hinge is furnished with a long incurved tooth in each valve. The tube in which the animal resides is testaceous, and somewhat cylindrical. The animal is an Ascidia.

+ DESCRIPTION. The Ship-worm, when full-grown, is in general from four to six inches in length, of a gray colour, and about the thickness of the middle finger. It is covered with a whitish, thin, cylindrical, and smooth shell; and has, in front of the head, two small hemispherical valves, flat before, and angular behind.

SYNONYMS. Teredo navalis. Linn.-Serpula Teredo. Da Costa. Le Taret Naval. Bosc.

ships. By means of their hard and cutting jaws, they are able to penetrate into any timber, except such as is of an extremely hard and compact substance. They, however, bore as seldom as possible across the grain; for, after they have penetrated a little way, they turn, and continue with the grain tolerably straight, until they meet with another shell, or knot. Their course then depends on the nature of the obstruction: if this be considerable, they prefer making a short turn back, in form of a syphon, rather than to continue for any distance across.

Col. Montagu states, that he had an opportunity of examining a great number of these shells in the Dockyard at Plymouth, where every possible means have been tried to prevent the ravages which are committed by them. Although they have not been known in this country more than fifty or sixty years, they are now become naturalized to our climate, and have, of late, very considerably increased in numbers. Piles of solid oak, which had not been in the water more than four or five years, were found, on examination, to be perforated by them.

In the year 1730, the inhabitants of the United Provinces were under serious alarm concerning these worms, which had made dreadful depredations in the piles that support the banks of many parts of their coasts. One of the persons who had the care of the coasts at that time, observed, to his astonishment, that some of the timbers, in the course of only a few months, had been made so full of holes, that they could be beaten to pieces with the least force.

Although, when the mud was scraped off, the perforations did not appear much larger than to admit a pin's head, yet the piles, on being split lengthwise, were found full of large passages, or hollow, cylindrical ducts, each of which contained a worm, enclosed in its testaceous tube, which it exactly filled.

The most efficacious method which has hitherto been discovered, to preserve timber from the ravages of these

worms, is that which is now adopted in the Dock at Plymouth, to cover all the parts that are under water with short, broad-headed nails. These soon cover the whole surface with a strong coating of rust, which is found to be altogether impenetrable to the animals.

OF THE PHOLAS TRIBE*.

The animals of this tribe, while very young, perforate clay, spongy stones, and wood; and, as they increase in size, they enlarge their habitation within, and thus become imprisoned. They are always found below high-water mark, and a mass of rock may sometimes be seen wholly perforated by them. They have two orifices, or openings, capable of elongation in the manner of a proboscis: one of these is supposed to be the mouth, and has the faculty of spouting water. Most of them contain a phosphorescent liquor, of great brilliancy in the dark, which also illuminates whatever it touches or happens to fall upon.

From the following species, the character of nearly the whole tribe may be collected.

THE DACTYLE PHOLAS t.

The very extraordinary powers possessed by these animals, of penetrating into solid bodies, when compared

* The Pholas has a shell of two valves, that open widely at each end, with several lesser ones at the hinge. The hinges are folded back, and united by a cartilage; and in the inside, beneath the hinge, there is a long, incurved tooth. The animal contained in this shell is an Ascidia.

+ DESCRIPTION. This is an oblong shell, marked with somewhat spinous stripes. When full grown, it is about an inch and a quarter deep, and nearly five inches broad. It is of a whitish colour, and, in its general external form, has a distant resemblance to a muscle.

SYNONYMS. Pholas dactylus. Linnæus.-Pholade dactyle. Bosc.-Pholas muricatus. Da Costa.

with their apparent imbecility, have justly excited the astonishment of philosophers and naturalists in all ages. When divested of their shells they are roundish and soft, and seem destitute of any instrument fitted for boring into stones. They are, indeed, each furnished with two teeth; but these are placed in such a situation as to be incapable of touching the hollow surface of their stony dwellings. They have also two corners to their shells, that open and shut at either end; but these are totally unserviceable to them as miners. The instrument with which they perform all their operations, and by means of which they bury themselves in the hardest rocks, is a broad fleshy substance, somewhat resembling a tongue. With this soft, yielding instrument, while yet young and small, they work their way into the substance of the stone, and enlarge their apartment as their increasing size requires.

The seeming unfitness of these animals, for penetrating into rocks, and there forming a habitation, has induced many philosophers to suppose that they entered the rock while it was yet in a soft state, and that, from the petrifying quality of the water, the whole rock afterwards hardened round them by degrees. This opinion, however, has been confuted, and, in a very satisfactory manner, by Dr. Bohads, who observed that many of the pillars of the temple of Serapis, at Puteoli, were penetrated by these animals. He justly concludes, that the Pholades must have pierced them after they were erected; for no workmen would have laboured a column into form, if it had been honey-combed by worms in the quarry. In short, there can be no doubt that the columns were perfectly sound when erected, and that these animals attacked them during the time they were buried under water, after the earthquake that swallowed up the city.

Hence it appears that, in all nature, there is not a greater instance of perseverance and patience, than that which this animal is seen to exhibit. Furnished with the bluntest and softest augur imaginable, it effects, by

slow successive applications, what other animals are incapable of performing by force, and penetrates the hardest bodies with only its tongue. When, while yet small, it has effected an entrance and buried its body in the stone, it there continues, for life, at its ease; the sea-water that enters at the little aperture, supplying it with luxurious plenty. On this seemingly thin diet it by degrees grows larger, and soon finds itself under the necessity of increasing the dimensions of its habitation and its shell.

The motion of the Pholas is slow, almost beyond conception; its progress keeps pace with the growth of its body; and, in proportion as it becomes larger, it makes its way further into the rock. When it has penetrated to a certain depth, it turns from its former direction and hollows downward; till at last, when its habitation is completed, the whole apartment resembles the bowl of a tobacco-pipe; the hole in the shank being that by which the animal entered.

Thus immured, the Pholas lives in darkness, indolence, and plenty: it never removes from the narrow mansion into which it has penetrated; and seems perfectly content with being enclosed in its own sepulchre. The influx of the sea-water that enters by its little gallery satisfies all its wants.

These animals are found in immense numbers at Ancona, in Italy. They are also found along the shores of Normandy and Poitou, in France, and some of the coasts of Scotland. In general they are considered a great delicacy at the tables of the luxurious.

Bivalves.

OF THE MYA TRIBE*.

Most of these animals are inhabitants of the ocean, but some of them are found in fresh water. They per

The shell, in most of the species, is gaping at the end.