ACEPllALA TKSTACEA. 



properly so called, a lamina projecting from one vaive into tne other, and an internal ligament proceeding 

 from that lamina to a corresponding fossa. The cloak is reflected outward upon the hinge, and con- 

 tains one or sometimes two or three supernumerary pieces. The foot issues by the opium- at the side 

 of the mouth, which is the widest, and from the opposite end there comes out the two tubes united in 

 one, and capable of being extended in every direction. The Pholades inhabit cells v. Inch they have 

 made, some in the mud, others in rocks, [and others in wood]. They are sought after [in some 

 countries] from their agreeable taste. 



P/iotas dactyliu, Linn., occurs on our coasts. [The genus Xylophaga of Turton, which burrows in decayed wood, 

 is reduced by Deshayes to Pholas.] 



The Teredines {Teredo, Linn.) — 



Have the mantle extended in a tube much longer than the two small rhomboidal valves, and terminated 

 by two short tubes, the base of which is furnished on each side with a calcareous and moveable kind 

 of operculum or palette. These Acephales, while quite young, penetrate and establish their habitations 

 in submerged pieces of wood, such as piles, ship's bottoms, &c, perforating and destroying them in 

 everv direction. It is thought that, in order to penetrate as fast as it increases in size, the Teredo 

 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 from its body, and which forms a second kind 

 of tubular shell for it. It is a noxious and destructive animal in the seaports of Europe. 



The common species (T. navalis, Linn.), which is said to have been introduced from the torrid zone, has more than 

 once threatened Holland with ruin, by the destruction of its dikes. It is six inches in length and upwards, and 

 bus simple palattes. In tropical countries, there are large species with jointed and ciliated palettes, which deserve 

 notice for the analogy they establish with the Cirrhopodes. Such is the Teredo palmulattu, Lam. 



The Fistulana, Brug. — 

 Has been distinguished from Teredo, for its external tube is entirely closed at its larger end, and is more 

 or less like a bottle or club. The species are sometimes found buried in wood or fruits that have been 

 apparently submerged in the water; sometimes they are simply enveloped in the sand. The animal 

 has two small valves and two palettes, as in the Teredo. Recent specimens are brought from the 

 Indian Ocean, but our formations have preserved some fossil species. 



Near Fistulana we should place Gattrocfuena, Spengler*, whose shells have a toothless hinge, and the margins 

 being *\ ide ap n t in front, leave a large oblique opening, opposite to which there is in the cloak a small opening for 

 the passage of the foot. The double tube, which can be concealed entirely within the shell, is capable of great 

 elongation. It appears certain that they have a calcareous tube. In some species, the beaks are at the anterior 

 angle; in others, near the middle. They live in the interior of madrepores, which they perforate. ["'This bivalve 

 is inclosed in the posterior clavate extremity of a shelly tube, which is attenuated and open anteriorly, its aperture 

 being oblong and bilobate, or nearly divided into two by a sort of septum which does not quite meet in tin- centre: 

 this double aperture serves for the passage of the two tubes of the animal : the posterior extremity of the shelly 

 tube is closed. This irregular clavate tube, already inclosing the two valves of the Gastroctuena, is generally found 

 within some other shell, to the inside of which it is attached, or it is protected in the ready-formed cavities of shells 

 or rocks, or it line's cavities perforated by the animal itself in rocks, shells, or corals, and in this hitter case, the 

 double termination of the shelly tube projects beyond the surface of the coral or other object in which it is 

 inclosed."] 



Among fossils, two genera have been recognized furnished with tubes like the Teredo, but the first [Teredina, 



Lain.] has a little, spoon-shaped cavity in each valve, and a little loose piece, in form of a shield, at the binge. 

 The other [Clavagella, Lam.) has one of its valves agglutinated to the tube, ami the other loose. A livn 

 is found in the madrepores of the Sicilian seas, which has been described by M. Audouin. [The best description 

 of this genus :s given by Messrs. Broderip and Owen in the Trout, of the Zoological Society."] 



Some naturalists think we should also place in this family 



Tin. Ami RGILLUM, — 



The shell of which is formed of an elon- 

 gated, conical tube, closed at its wide 



tremity by a disk perforated with numerous 

 small tubular holes ; the little tubes of the 

 outer range, being longest, form a kind of 

 corolla round it, I in for approxi- 



mating them to tie- Acephala with tubes is 



Fig l93-Aip f r B ill„m. fomi( , ,„ ^ ,'„., ,,,,, , „ ,,„„,,,„ 



• According lo DtiKtrri, Gtitlocnana mil IlilttUn* ire the um< 



