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Show 424 MOLLUSCA. trate and establish their habitations in sub~erged pieces ~f wood, such as piles, ships' bottoms, &c., perforattng and destroymg them in every direction. It is thought, that in order to penetrate as fast as it increases in size, the Pholas excavates the wood by means of its valves; but the tubes remain near the opening by which its entrance was effected, and through which, by the aid of its palette, it receives water and aliment. The gallery it inhabits is lined with a calcareous crust which exudes ft·om its body, and which forms a second kind of tubular shell for it. It is a noxious and destructive animal in the sea ports of Europe. Teredo navalis, L. This species, which is the most common, and is said to have been introduced into Europe ft·om the torrid zone, has more than once threatened Holland with ruin by the destruction of its dikes. It is upwards of six inches in length and has simple palettes. Larger species inhabit hot countries, whose palettes are at·ticu· lated and ciliate. They should be remarked for their analogy to the Cirrhopoda. Such is the Teredo palmulatua, Lam., Adans., Ac. des Sc., 1759, pl. 9, f. 12.' FisTULANA, Brug. Separated from Teredo; the external tube is entirely closed at its larger end, and is more or less like a bottle or club. The Fistula· nre are sometimes found buried in submerged fragments of wood or in fruits, and the animal, like that of a Teredo, has two small valves, and as many palettes. Recent specimens are only obtained from the Indian Ocean, but they are found fossil in Europe( 1 ). We should approximate to them the GAsTROCHJENA, Spengler. Where the shells are deprived of teeth, and their edges being wide apart anteriorly, leave a large oblique opening, opposite to which there is a small hole in the mantle for a passage of the foot. The double tube, which can be retracted co.mpletely within the shell, is (1) Teredo clava, Gmel., Spengl., Naturforsch., XIII, 1 and 2, copied Encyc. Method., Vers., pl. clxvii, f. 6-16. It is the Fistulana gregata, Lam. ;-Teredo utriculus, Gm., Naturf., X, i, 10; probably the same as the Fistulana lagenula, Lam., Encyc ., Method., I, c, f. 23 ;-Fistulana clava, Lam., Ib ., 17, 22. It is probable that the Pholas teredula, Pall., Nov. Act. l'etrop., II, vi, 25, is also a Fistulana. ACEPHALA TESTACEA. 425 susceptibl~ of bein_g greatly elongated. It appears that they are certainly furmshed w1th a calcareous tube( 1). In some_ of them, as in the Mytili, the summits are at the anterior angle(2); m others they are placed near the middle(3). They inhabit the interior of Madrepores ' which th ey per1r orate. Two genera of Acephala furnished with tubes have be d fi . , en detecte among ossds, but the first of them, the TEREDINA, Lam., Has a little cuilleron on the inside of each of its valves, and a small ft·ee, shield-shaped piece on the hinge( 4). In the second, ' CLAVAGELLA, Lam., One of the valves is clasped by the tube, leaving the other, however, free( s). A single living species is found in the Madrepores of the Sici· lian seas, which has been described by M. Audouin. Some naturalists think we~.should also place in this family the AsPERGILLUM, Lam., The shell of which is formed of an elongated conical tube closed at its widest extremity by a disk perforated with numerous' small tub~ lar holes; the little tubes of the oute1· range being longest, form a kmd of corolla round it. The reason for approximating them to the Acephala with tubes is found in the fact that there is a double projection on one part of the cone which really resembles the two valves of the Acephala. The affinity between these little tubes and those which envelope the tentacula of certain Terebella, formerly caused this animal to be referred to the Annelides. The species most known,-Asper. javanum, Mart., Conch., I, pl. 1, f. 7, is seven or eight inches in length(6). (1) This tub~ has been observed by Messrs Turton, Deshayes, and Audouin. lWll Pholashtans, Chemn., X, clxxii, 1678, 1679. ~3) Id., 1681, a very different species from the preceding, not properly distin· gu1shed by Chemnitz. ~:~ Teredi~a personata, Lam., and Desh., Foss. de Par. I, pl. i, f. 23, 28. 15 01. echmata, Lam., Ann. du Mus., Xll, xlii, 19, 01. C{)'l'onaia, Desh., Foss., I, v, '16. (6) Add the .Jlrroaoir a manchettea, Savig., Egyp., Coq. pl. xiv, f. 9. VoL. II.-3 D |