^{page 428 note *} “His natura in tenebris, remote lumine, alio fulgore clarere, et quanto magis humorem habeant, ludere in ore mandentium, lucere in manibus, atque etiam in solo et veste decidentibus guttis.”—Plin. lib. ix. c. 61.

^{page 428 note †} “Hæ in saxis latet, ut saxo undique contegatur, per foramen duntaxat exiguum et sensui vix patens aqua nutritus. Testis constat duabus longis, non in latum extensis mytulorum modo, sed rotundis. Intus eadem fere est caro quæ in mytulis.” —Rond, . de Testaceis, lib. i. p. 49Google Scholar. I strongly suspect, that Rondeletius has figured the Mytilus lithophagus under the title of Pholas; and that subsequent writers have been misled from not having seen his figures. The species of Pholas which he delineates is given under the name of Concha altera longa.—Vide Rond. p. 23, 27.

^{page 428 note ‡} “Hæ conchæ juxta Hartlepool frequenter reperiuntur, et in lapidis cujusdam cretacei foraminibus latitant ab ipso eorum ortu; nam ex his eximi non possunt, nisiprius lapis frangatur.”—Lister, Anim. Ang. p. 172.

^{page 429 note *} Bonanni, Recreat. p. 36.

^{page 430 note *} In opposition to this theory, it has been remarked, that, from the lodgment which the Pholades have made in the pillars of the Temple of Serapis at puteoli, it must be concluded that they have bored their holes after the erection of the pillars. Dr Bochadsch, who noticed these columns, observes, that the workmen would certainly have rejected any stones that had been disfigured in this manner. The Pholades must therefore have worked their way into them while they were buried by the influx of the sea, which immediately succeeded the destruction of the city by an earthquake. —Bochadsch, as quoted by Mr Wood.

^{page 430 note †} As Reaumur has been referred to as supporting a very different theory, I give his own words:

“Apparemment qu'l n'y a guère dans la nature de mouvement progressif plu lent que celui du Dail; muré comae il est dans son trou, il n'avance qu'en s'approchant du centre de la terre: le progrès de ce mouvement est proportionné à celui de l'accroissement de l'animal; à mesure qu'il augmente en étenduë, il creuse son trou et descend plus bas. La partie dont il se sert pour creuser ce trou est une partie charnuë située près du bout inferieur de la coquille; elle est faite en losange et assez grosse par rapport au reste du corps. Quoiqu'elle soit d'une substance molle, il n'est pas étonnant qu'elle vienne à bout de percer un trou assez profond dans une matière dure: elley employe bien du temps. J'ai vû ces Dails se servir de cette partie à l'usage queje lui attribuë, après les avoir tirés de leurs trous et les avoir posés sur un glaise aussi molle que de la bouë; en recourbant et ouvrant ensuite cette partie, ils se creusoient un trou, et en creusoient en peu d'heures un aussi profond que celui auquel ils travaillent pendant plusieurs années, aussi y trouvoient-ils beaucoup moins de résistance, et le besoin qu'ils avoient de se cacher leur faisoit apparemment accélérer leur travail.” Mém. de l'Acad. Roy. des Sciences, 1712, p. 127.

^{page 431 note *} L'Hist. Nat. éclaircie dans une de ses parties principales.—Zoomorphose, p. 69, 70. Paris, 1757.

^{page 331 note †} British Zoology, vol. iv. p. 158,

^{page 432 noote *} Testacea Britannica, p. 560, 561.

“It is well known (observes Montagu in another place) that animals as well as vegetables prepare, by various occult processes, fluids powerfully corrosive: the viper secretes a deadly poison, which is forced through the cavity of its fang; the pismire, and some other insects, eject a powerful acid, capable of dissolving calcareous stone. Surely, then, it may most reasonably be admitted, that, by some such chemical means, prepared in the great elaboratory of Nature, these testaceous Ascidia perform the part assigned to them by the Creator of the Universe.”—Montagu, Supplement, p. 15.

The Pholades, it is remarkable, bore the wood across the grain, while the Teredo navalis perforates it in the direction of the fibres.

^{page 432 note †} General Conchohgy, vol. i. p. 74.

^{page 432 note ‡} Zoological Journal, No. 3. p. 406.

^{page 435 note *} Of the power of the Pholades to bore limestone, marble, or shale, it is easy to satisfy one's self, by the simple experiment of rubbing the shell gently on a piece of marble, which it cuts without rounding the asperities of the shell. Oak is likewise scratched in the same manner; but the action of the Pholades is always on submerged wood or rocks partially covered by the tide, and the water, in both cases, must facilitate the process of boring.

^{page 436 note *} There are several striking points of similarity of habit between the Pholades and the Myæ. The Myæ burrow in sand, gravel, or clay, and project their tube to the surface in the same manner as the Pholades. The form of their syphon is nearly the same, as is also the mantle which connects the two valves. Their mode of sucking in the water, and expelling it in jets, is the same in both. I have kept the Mya arenavia alive in sea-water for several days, and witnessed repeatedly its wetting the room to a considerable distance, from its often repeated and violent ejection of the water. The Mysæ, however, at least the M. arenaria and truncata, though they easily penetrate soft clay or sand, do not seem to have the power of boring into hard substances; for in many specimens I have met with, in gravelly places, the shell was distorted, from being placed between stones, which its force could neither remove nor form to the contour of its shell.

^{page 436 note †} Since the foregoing remarks were written, I have seen Poli's magnificent work, and feel gratified by finding that the observations I have hazarded entirely coincide with the opinions of that able observer. In Tab. VII. he has not only given beautiful representations of the shell of the Pholas dactylus, and its contained animal; but has displayed its anatomical structure in a series of figures which leaves nothing further to be desired. M. Poli is clearly of opinion that the Pholades bore the rocks by mechanical action alone; and he elsewhere adduces arguments to prove that even the Mytilus lithophagus, the comparatively smooth shell of which seems unfitted for such a purpose, forms its dwelling in a similar manner. The passage regarding the Pholas is as follows:

“Cryptae hujusmodi conicam formam prae se ferunt, angustiore sui parte sursum versa, per quam Molluscum Pholadem incolens tracheas pro lubitu exerit. Earum amplitudo Pholadum ætati, atque magnitudini respondere videtur: in adultis duos circiter pedes in altitudinem patet, et hiatus diameter quinque lineas minus excedit. In junioribus, mollusca turn pede exerto, ac in terebræ formam accommodate, tum etiam conchæ ministerio circa pedis apicem veluti circa axem revolutæ, cryptam profundiorem, latioremque efficiunt quemadmodum adolescunt. Tanta est motus hujusmodi efficacia, ut lapidibus simul perterebrandis par est.”—Poli, J. X., Testacea utriusque Sicilia eorumque Historia et Anatome, vol. i. p. 40. Parma 1791Google Scholar.

^{page 437 note *} “Ego crediderim in saxorum cavernulis vel vi vel natura factis, aquæ marinæ appulsu procreari atque in concham verti, quæ cavitatis sive foraminis figuram servat.” —Rondelet, . De Testaceis, lib. i. p. 49Google Scholar. Lugd. 1555.

^{page 438 note *} The disposition of the strata on the coast at Joppa, and its present appearance, strikingly illustrates the power of the instruments which Nature has employed in the disintegration of certain classes of rocks. The beds of shale, which in some places seem to have been from 12 to 20 feet thick, have in most instances wholly disappeared; parallel roads or spaces, deeply covered with sand, and on a level with the neighbouring shore, being alone left to mark out the places formerly occupied by the shale. Dead shells, of very large size, are also frequently found on various parts of the coast, or dredged up by fishing-boats; thus affording indications, in the places where they are found, of the disappearance of strata effected by their agency. Encrinites are found in the shale at Joppa inhabited by the Pholades.

^{page 439 note *} Bosc. in Nouv. Diet. d'Hist. Nat. Vol. xxv. p. 539. M. G. P. Deshayes has recently described and figured four species of fossil Pholades, found by him, among other perforating bivalves, at the village of Valmondois in France.—Mém. de la Soc. d'Hist. Nat. tom. i. p. 245.