286 



MUSEUM OF ANIMATED NAIURE. 



[Tehedina. 



3012.— The Maskib Tebeuina 



(Tcredina pertonata). The genus Teredina is 

 known only in a fossil slate. Like Teredo, and 

 other lorms to which we shall presently allude, be- 

 sides valves, it presents a tubular extension, solid, 

 testaceous, and of considerable thickness, graduiilly 

 diminishing as it proceeds ; it is not divided by 

 a partition into two siphons, but it is continued 

 from and unites the posterior part of the two 

 valves 



M. Deshayes remarks that Tcredina is a true 

 Pholas, with globular vhIvcs fixed at the end of 

 a tube, and is furnished within wilh those ap- 

 pendages characteristic of Pholas and Teredo. Turn- 

 ing to the figure, a shows the valves with the basal 

 part of the tube ; b is the continuation of the 

 same tube ; c, an accessory valve ; d, the two valves 

 with the accessory valve in its place. 



The Tcredina persoiiata is found in the Eocene 

 beds of the teitiaiy system. 



Tlie genus Teredo is represented by that formi- 

 dable animal Calamitas navium, the ravages of 

 which upon submerged wood are so extensive and 

 dangerous. 



These animals, says Cuvier, Les Tarets of the 

 French, have the miuiile continued into a tube, very 

 much lonjier than their two little rhomboidal valves, 

 and terminated by two short siphons ; a muscular 

 ring at the point of junction of the mantle and the 

 tubes has implanted there a pair of pediculaled 

 corneo-calcareousappendages, or "palettes," playing 

 laterally one against the other. These moUusks 

 penetrate when young info the interior of sub- 

 merged wood, as stakes or piles, and the keels of 

 ships, and, establishing themselves there, commit 

 great mischief, riddling every part. It is supposed 

 that the Teredo, in oider to bury itself according to 

 its growth, perforates the wood by the aid of its 

 valves. The tubes remain always towards the 

 orifice by which it made its entrance, and through 

 which it draws in the water and nutriment, by the 

 action of the " palettes. ' The tunnel in wliich it 

 dwells is lined with a calcareous crust transuded 

 from it, and which forms a sort of tubular shell. 



The animal, we may add, is vermiform in shape, 

 with a delicate mantle open in front, and at its 

 lower part for the passage of a manimiliform foot ; 

 the nioulh is small, with short labial appendages. 



The shell is thick, short, annular, and open before 

 and behind. There is no hinge ; an elongated nearly 

 straight spoon-shaped process presents a slightly 

 marked muscular impression. 



The tube is cylindrical, straight or flexuous, and 

 becomes closed with age at the anterior extremity, 

 so as to envelope both animal and shell, but it always 

 remains open at the other end, and lines the cavity 

 which the animal luas perforated. 



Sir Everard Home, whose account of the Teredo 

 navalis, and a species called by him Teredo gi- 

 ganlea, was published in the ' Pliilosoiihical 

 Transactions,' ISOG, states that on examining the 

 shell of Teredo navalis while in the wood, he found 

 the external orifice of the canal very small, and in 

 fact only just large enough to give passage to the 

 two small tubes or siphons. The canal at its 

 termination and for an inch in length was not 

 lined with shell, but smeared over with a dirty 

 green-coloured mucus, which was also spread 

 upon the last-formed portion of the shell. When 

 the animal was alive, and undisturbed, what is 

 termed the head was in contact with the end of 

 the canal in the wood ; but on laying bare the head 

 it was drawn for an inch into the shell. 



The largest of the worms (Teredines) examined 

 measured eight inches in length ; and many were 

 alive twenty-four hours after being removed from 

 the shell. The head of the worm was enclosed 

 between the two boring-shells, and these were united 

 toeether by a strong double muscle, having a 

 middle tendon, and enclosing the oesophagus and 

 other parts. On the opposite side of the head 

 the shells were united by a ligament, and at this 

 part were two small tooth-like processes, one from 

 the narrow edge of each shell, where they were 

 joined together. From the middle of the exposed 

 part of the head projected a kind of proboscis, 

 which in the living animal had a vermicular mo- 

 tion ; its extremity was covered by a cuticle not 

 unlike the cornea of the eye ; and it was found to 

 cover a cavity like a Florence flask with the large 

 end uppermost, and containing a hard biovvn-co- 

 loured gelatinous substance. This pioboscis has 

 no orifice, and Sir E. Home remarks, there is reason 

 to believe it adheres to the wood, acting as a centre- 

 bit, while the animal is at work witli the shell, 

 and thus the canal in the wood is perfectly cylindrical. 



The mouth was nearly concealed by the projection 

 of the proboscis, but was a distinct round orifice. 

 The body of the worm was found enclosed in one 

 general covering, extending from the base of the 

 boring shell, with which it was connected, to the 



root of the two small tubes which appear out of 

 the wood. It terminates in a small double fold, 

 forming a cup, on the inside of which are fixed 

 the stems of two opercula, which become broad and 

 flat towards their extremity ; these, when brought 

 together, shut up the shell and enclose the two con- 

 tracted limbs. The Teredo, he adds, turns round 

 in the shell, to which the animal is not attached, and 

 to which its covering has only a slight connexion at 

 one particular spot, to prevent the external tubes 

 from being disturbed. The motion, he observes, 

 is for the purpose of boring. 



Fig. 3013 reoresents the animal of Teredo navalis 

 out of the shell. A. In this the opercula are want- 

 ing and the tubes retracted ; B. In this specimen the 

 opercula are in their situation : a a, the boring- 

 shells ; 6, the proboscis; c, the mouth; d d, the 

 contents of the abdomen, seen through the trans- 

 parent external covering ; e e, the branchiae, seen in 

 the same manner. 



Fig. 3014 represents the tube and shell of Teredo 

 navalis : a, the tube with "the valves in their natural 

 position at its anterior extremity; b and c, two 

 views of valves ; d, the two tubular siphons of the 

 animal protruded. 



Fig. 3015 represents a block of wood perforated 

 by the Teredo navalis. 



The Teredo navalis has been found at depths 

 varying from the surface to ten fathoms; though 

 unfortunately now so common in our seas, this 

 terrible scourge is said to have been originally 

 brought by ships from warmer climates. All sub- 

 marine wood-work, such as the piles of piers, flood- 

 gates, and the like, are soon riddled by it, often in 

 spite of every precaution ; and it has threatened the 

 submersion of Holland by the destruction of the 

 flood-gates and wood-work of the dykes. 



The rapidity with which it commits its ravages is 

 astonishing ; a piece of deal after forty days' sub- 

 mersion has been found completely riddled by these 

 animals, some of which had attained to a consider- 

 able size even in that short space of time. Montagu 

 obtained a number of these animals in piles from 

 the Dockyard at Plymouth, which were taken up to 

 be replaced with new, although they had not been 

 above four or five years under water, and were 

 sound solid oak when driven. The most effectual 

 way to preserve wood from the attacks of these 

 "worms" is to cover the whole of the suiface 

 exposed to their depredations with short broad- 

 headed nails, set as closely together as possible. 

 The action of the salt-water on the iron produces 

 a coating of rust, which is said to be superior 

 in durability and effect to the copper sheathing 

 with which the hulls of vessels are covered under- 

 neath. 



II has been a question whether the Teredo navalis 

 derives nutriment from the particles of the wood 

 in which it drives its galleries, or the contrary. We 

 think the probability is that it does not, and that 

 the end of its boring is only to secure a proper 

 habitation. It is, we believe, ascertained that an 

 impalpable vegetable sawdust is found in the intes- 

 tines, but unchanged by the process of digestion ; and 

 besides, at a certain period of existence, the animal 

 closes the tube and valves anteriorly, and ceases to 

 bore, deriving its nutriment, through one of the open 

 siphons, from the animal matters with which the 

 sea-water is replete. Sir E. Home suggests that, as 

 the alimentary canal is straight and simple, the 

 sawdust may be needful in order to retard the 

 progress of the food, that the complete digestion of 

 the latter may be effected. This, however, is a 

 mere theory. 



A gigantic Teredo, Teredo gigantea, is found in 

 the Indian Seas, but fortunately it does not bore 

 into wood, its habitation being perforated in deep 

 beds of hardened mud. This species, which attains 

 the length of six feet, and perhaps much more, was 

 first figured by Rumphius. His specimens were 

 found in shallow water among mangrove-trees. In 

 1805 Captain Maxwell, of the Calcutta, East India- 

 man, gave to Sir Everard (then Mr.) Home a 

 specimen of this singular shell or tubular envelope, 

 five feet long, though imperfect at both extremities. 

 By some scientific men this was considered as a 

 hollow stalactite, but Sir Joseph Banks regarded it 

 as a shell, and chemical analysis confirmed the 

 correctness of his opinion. 



In the ' Phil. Trans. ' for 1806 is a paper by Mr. 

 Gi ifiiths (to whom Sir E. Home was introduced by 

 Mr. Marsden) on the Teredo gigantea, immediately 

 preceding that by Sir E. Home. 



Mr. Giiffiths relates that a short time afler a very 

 violent earthquake which occurred in the year 17i)7, 

 at Sumatra, and produced a most tremendous 

 inundation of the sea, spreading desolation around 

 and causing the loss of many lives, these shells 

 were procured in a small bay with a muddy 

 bottom, surrounded by coral reefs, on the island 

 of Battoo. On the recession of the sea alter 

 the extraordinary inundation, they were observed 

 : protruding from a bank of slightly indurated 



mud, and two or three specimens were brought 

 to Mr. Giiffiths, by the master of a trading 

 boat. Mr. Griffiths then sent one of his servants, a 

 Papooa Cofl'ree, who was an excellent diver, to 

 procure others. This man stated that he had found 

 the shells in the bay already mentioned, and also in 

 an inlet of the sea, sticking out of hard mud mixed 

 with sand and small stones; they protruded to the 

 extent of eight or ten inches, and were from one to 

 three fathoms under water. 



Mr. GiitSths was assured that the animal throws 

 out tentacula from the two apertures of the apex of 

 the shell, resembling small Actiniae (sea anemones), 

 and that the shell was filled with soft gelatinous 

 flesh, similar to that of the Teredo navalis; this, 

 however, being putrid, was washed out by the men 

 who collected the specimens. All the shells were 

 more or less mutilated, probably by the action of the 

 waves, which had torn up large masses of coral and 

 madrepore, during the continuance of the earth- 

 quake. The longest Air. Griffiths procured was 

 five feet four inches; some had the anterior ex- 

 tremity, others the posterior extremity broken. 

 Most of the shells had the small cocks-comb oyster 

 and various scrpnlae adhering to their posterior 

 extremity for more than a foot, proving that during 

 their existence this part of the shell had protruded 

 above the mud in which the remainder was buried. 

 The specimens were milk-white externally, and 

 tinged with yellow within ; and the large or buiied 

 end was completely closed, and had a rounded 

 appearance. The substance of the shell was 

 composed of layers having a fibrous and radiated 

 appearance, covered externally with a pure while 

 crust. Many specimens were nearly straight, others 

 more or less contorted. 



Here then we have a gigantic Teredo, which 

 bores not into wood, but into banks of mud in the 

 sea, and lives alter the closure of the buiied ex- 

 tremity of its singular shell. 



Fig. 3<)16 represents the Teredo gigantea as 

 figured by Rumphius, with two terminal tubes, in 

 which it differs a little from the specimens obtained 

 by Mr. Griffiths, perhaps in consequence of a 

 different kind of situation. The anterior extremity 

 is closed. 



Fig. 3017 is the Teredo gigantea, as figured by 

 Mr. Griffiths. A, the small or upper end, protruding 

 from the mud; the external covering is broken away, 

 showing the termination of the tubes, one of which 

 is broken : B, a longitudinal section of that part of 

 the shell where the double tubes are formed : C, the 

 shell complete, or nearly so, the upper extremity 

 only being imperfect. 



Fig. 3018, a transverse section of the shell, giving 

 a front view of the orifices of the double tube, and 

 showing the thickness of the shell at that part. 



Fig. 3019, a transverse section of the shell at a 

 thicker part, after it had been polished, showing 

 the density of its structure, and giving a front view 

 of the orifices into the double tube. The circum- 

 ference at the base of a shell of five feet four inches 

 was nine inches, but at this part its substance is 

 thin. The apex with the double tube is brittle. 



Family GASTHOCH.ENIDJi, Gray (G ASTRO. 

 CH^NA, CLAVAGELLA, &c.). 



The family Gastrochaenidse comprehends part of 

 the family TubicolidiE of Lamarck, and is composed 

 of tubular burrowing moUusks, of which we first 

 select the Gastiochaena. 



Of the genus Gastrochaina several species aie 

 known, and in the ' Proceeds. Zool. Soc' 1834, pp. 

 21, 22, will be found the description, by Mr. G. B. 

 Sowerby, of five species from the western coast of 

 South America and the islands of the South Pacific. 



In Gaslrocha;na there is a delicate bivalve shell, 

 extremely gaping, with distinct umbones, a straight 

 hinge, anU an external ligament, and showing 

 internally two muscular impressions. In this shell 

 the mollusk is partially enclosed, with the lobes of 

 the mantle united, (leaving only a small anterior 

 opening fora conical loot,) and produced posteriorly 

 into two united tubes. 



To the shell is sometimes added a calcareous tube 

 which envelopes the valves, and lines the cavity of 

 the stone into which the animal has penetrated. 

 Cuvier says, it appears, that the Gastrochacnae have 

 uniformly a calcareous tube, but M. Hang states that 

 this is not the case, though, like the Pliolas, all 

 burrow into stones. Sometimes, however, the 

 animal burrows in madrepore, and sometimes not 

 at all, but takts up its abode in old shells, as 

 spondyli, and pearl-oysters, &c. M. Rang divides 

 Gastrocha-na into two sections : I. species whose 

 shell is smooth without a distinct tube — Example, 

 Gastrochiena cuneilorrais ; 2. species whose shell is 

 striated from the umbo to the base, and contained 

 in a distinct tube. — Example, Gastrochaena clava. 

 This testaceous lube, it may be observed, the 

 Gastrocliaena forms either as a lining lor the 

 canal it has perforated, or as a covering tor its shell 



