266 



MUSEUM OF ANIMATED NATURE. 



[LiTUODOMUS. 



occurring in beds which cover rocks and stones, 

 generally between high and low waler-niark, but 

 often also at a greater depth. We have teen shells 

 clu^tered over by these niullusks, and some time 

 since had under our immediate notice a large live 

 lobster, the back of which was densely covered by 

 a phalanx of mussels in senied array, a circumstance 

 to which, on other considerations, we shall hereafter 

 revert. 



We need not say that the mussel is extensively 

 Used as food, and by some exceedingly relished. 

 It is however eaten by many persons with certain 

 misgivings, arising from its supposed poisonous pro- 

 perties ; some regarding the byssus as deleterious, 

 while others have supposed that a little crustacean 

 (Pea-crab) which at particular seasons shelters itself 

 in the shell of the mussel, is the source of mischief 

 The fact is the mussel is by no means digestible, 

 and that with some constitutions, or some temporary 

 conditions of the digestive organs, it cannot be eaten 

 with impunity. Several persons may partake of the 

 same dish, and yet only one or two may suffer ill 

 effects — which manifest themselves in flushings of 

 the face, nausea, derangement of the system, often 

 followed by blotches, rashes, swellings, spasmodic 

 asthma, and other unplea.sant syra|itom3. Similar 

 eH'ects occasionally follow a hearty meal upon crab, 

 or even upon lobster ; a phosphorescent lobster is 

 poison. The most celebrated mussels are from Ilam- 

 Dleton, a village in Lancashire ; they are taken out 

 of the sea, and placed in the river Weir within reach 

 of the tide, and grow fat and delicate. 



There is a fine species of mussel (Mytilus Choros, 

 Molina) particularly noticed by Captain King 

 amongthe ghell-fish of the island of Chiloe. Molina, 

 he says, has described the Choro (mussel) of Con- 

 ception, which is not different from that of Chiloe. 

 It is often found seven or eight inches long. The 

 fish is as large as a goose's egg, and of a very rich 

 flavour; there are two kinds, one is dark brown, 

 the other of a yellow colour : but the last is most 

 esteemed. 



There is another sort also, much larger than the 

 Choro, but equally delicate and good ; the fish of 

 which is as large as a swan's egg : it is called Cholgua, 

 but as the shells seem to be of the same species, I 

 think the distinction can be only owing to size. The 

 manner in which the natives of these islands, both 

 Indians and descendants of foreigners, cook shell-fish 

 is similar to that used for baking in the South Sea 

 Islands, and in some parts of the coast of New 

 Holland. A hole is dug in the ground, in which 

 large smooth stones are laid, and upon them a fire 

 is kindled. When they are sufficiently heated, the 

 ashes are cleared away, the shell-fish heaped upon 

 the stones, and covered first with leaves or straw, and 

 then with earth. The fish thus baked are exceed- 

 ingly tender and good, and this mode of cooking 

 them is superior to any other, as they retain within 

 the shell all their own juiciness. 



Some of the Mylili have the shell striated lon- 

 gitudinally ; as the following : — 



2909. — The Magellanic Mytilus 



(^MytUus MageUanicus). In this species the shell is 

 violet purple above, with long thick undulated fur- 

 rows ; inside whitish ; length four or five inches. 

 The shells of old individuals when polished are very 

 brilliant and deeply tinted with purple, passing into 

 rich violet. 



This mussel is found in the Strait of Magalhaens, 

 at Chiloe, &c. Its flesh is excellently flavoured and 

 nutritious. The specimen is represented as attached 

 to a rock by its strong byssus. 



The next genus to oe noticed is that to which Dr. 

 Vanbeneden has given the title of Dreissina (from 

 M. Dreissins of Mazeyk), of which the type is the 

 Mytilus polymorphus of Pallas and Gmeliii. 



In this genus the raollusk differs from that of 

 Mytilus, the mantle being far more extensively 

 closed, with three apertures, one anterior and two 



f>osterior: of the latter the terminal aperture is 

 arger than the other, and prolongs itself into a 

 short siphon, destined to conduct the water over the 

 branchiae ; the other aperture is placed more dor- 

 sally for the rejection of effete matters : the anterior 

 aperture is for the passage of the byssus and the 

 foot. 



The shell exhibits three muscular impressions, 

 and a septum internally at the umbo. The shell is 

 of a more recurved form than we find generally in 

 Mytilus ; the Mytilus recurvus, however, of America, 

 is regarded by Dr. Vanbeneden as its analogue. 



Dr. Vanbeneden records two recent species, 

 Dreissina polymorpha, and Dreissina Al'ricana. 



In their habits these species resemble the marine 

 mussels ; they form beds at the bottom of the water, 

 adhering to stones, shells, rocks, &c. : numbers are 

 often agglomerated together by means of their 

 byssus in bunches, or to a stone or shell, which they 

 entirely shroud. Their extent of range is consider- 

 able, their dispersion resulting from the circumstance 

 of their attaching themselves to logs of wood, or the 



keels of vessels, by means of which they are trans- 

 ported from sea to sea. 



Fig. 2910 represents the Dreissina polymorpha. 

 A, the shell and animal of the natural size, with the 

 siphon, a, exerted ; and the more dorsal orifice also 

 to be seen at 6; c, the posterior row of papillae, b, 

 a view of the ventral side : a, tlie siphon ; b, the 

 anterior row of papillae ; c, the languette. c, animal 

 in the left, valve : a, the abdomen ; b, the languette 

 in situ ; c, the branchiae ; d, the dorsal orifice ; e, 

 the aperture of the byssus;/, the byssus turned 

 back. 



The languette, it is stated, does not appear to be 

 the true foot (which is muscular and serves as an 

 organ of progression), but forms a part of the re- 

 tractor muscle ; and possesses no character in 

 common with the foot except its mobility; at the 

 base of this organ is the byssus — such is Dr. Vanbe- 

 neden's opinion. If this be not the foot modified, 

 then the mollusk is destitute of such an organ ; but 

 the admission that it seems to explore bodies with 

 this languette, would lead us to think that it was at 

 least a substitute for that organ, which in the mussel 

 is more developed. 



Fig. 2911 represents the Shell of Dreissina poly- 

 morpha; a, the inside view of the valve, showing 

 the septum at the umbo ; i, the valve viewed ex- 

 ternally, so as to afford a good idea of the general 

 outline. 



The Dreissina polymorpha is spread extensively 

 through Europe and Asia. It inhabits seas, lakes, 

 rivers, and marshes, all being alike congenial abodes. 

 It is found in the Caspian Sea, the Black Sea, the 

 Baltic, the rivers Danube, Wolga, and Rhine 

 (abundantly), the marshes of Syrmia, the canal of 

 Belgium (Canal Guillaume), the lakes of Holland, 

 the Thames, the Lea, the Commercial Docks, London, 

 the Union Canal at Edinburgh, and many other 

 localities. Mr. J. D. C. Sovverby, we are inlbrmed, 

 was the first to notice the occurrence of this species 

 in the Commercial Docks in the Thames, and he is 

 of opinion that it was originally introduced adherent 

 to shipping, logs of timber, &c. 



We now advance to the genus Modiola (Modiolus 

 of some authors). 



This genus is separated from Mytilus upon some- 

 what unsatisfactory grounds, and principally because 

 the umbones, instead of being pointed and terminal, 

 are rounded and do not advance so far as the an- 

 terior margin of the shell, which is produced in a 

 rounded form. Nevertheless, when a number of 

 species, fossil and living, of both genera are assem- 

 bled together, it will be found that the transition 

 from genus to genus is so imperceptibly gradual 

 that there is no possibility of determining the point 

 where the one ends and the other begins. These 

 observations equally apply to the transition between 

 Modiola and Lithodomus, proving that the genera 

 are artificial rather than natural. 



Many of the Modiolce live in stones, into the 

 substance of which they bore their way, but by what 

 means is not positively ascertained ; others, however, 

 moor themselves by a byssus. Mr. G. B. Sowerby 

 observes that "the Modiolae, like the Mytili and 

 many other genera, afiix themselves to submarine 

 productions by means of a bundle of rather coarse 

 fibres, commonly called a byssus, each fibre of 

 which is fastened to the rock by its expanded 

 external termination, and applied by the foot of the 

 animal. The recent species of modiolus are not 

 very numerous ; we have, however, several on the 

 coasts of Britain, of which the most remarkable 

 are M. discrepans and M. diseors." These two 

 species are always found imbedded in the com- 

 mon ascidia (one of the Tunicata), and appear to be 

 destitute of a byssus, while much larger specimens, 

 brought from the West Indies, are found completely 

 enveloped in a fine silky byssus, closely matted 

 together and forming large bundles. Some cognate 

 species, however, which have been brought from 

 the Northern Ocean, appear, he adds, to have been 

 aflSxed by a few filaments only. 



2912.— The Shlcated Modiola 

 (Modiola sulcata). This species represents a sec- 

 tion in which the shell is sulcated longitudinally. 

 It is a native of the Indian Seas. Hinge margin 

 dentilated ; shell bluish white ; epidermis yellowish. 

 a, the shell closed, with the byssus; b, outside view 

 of valve ; c, inside view of ditto. 



2913. — The Cinnamon-coloured Modiola 



(Modiola silicula). This species, which according 

 to M. Deshayes is identical with M. cinnamomea, 

 is found in the seas of the Isle of France and of New 

 Holland. The shell is of a maroon brown or whitish; 

 the epidermis is deep maroon brown. 



Most naturalists agree in the generic distinction 

 of our next genus Lithodomus, Cuvier ; the shell is 

 delicate, covered with an epidermis, oblong, elonga- 

 ted, subcylindrical, and rounded anteriorly, but not 

 gaping ; the umbo is distinct, but surpassed by the 

 { anterior margin ; the hinge is toothless ; the animal 



is oblong, elongated, thick, with the mantle pro- 

 longed and fringed posteriorly ; the foot is very 

 small, linguiform, and channelled ; it carries a byssus 

 at its base during the early period of the animal's ex- 

 istence, but this is afterwards lost. The Lithodomi 

 are rock-borers. In theearlystagesof their life they 

 live like mussels moored by their byssus to masses of 

 stone, madrepores, &c., but soon, impelled by an in- 

 stinct which cannot fail to excite surprise, they com- 

 mence boring the rocks or masses of madrepore to 

 which they were attached, and form galleries into 

 which they work their way, boring and enlarging the 

 cavity as they proceed, and in which they are im- 

 prisoned during life ; for their volume increasing as 

 they advance in age, they cannot retreat by the way 

 through which they have effected their entrance. 

 Their byssus is now useless, it becomes lost, and is 

 never reproduced. 



Lithodomi are common in the warmer seas of 

 Europe, as the Mediterranean, and also in the seas 

 of the Antilles. 



With respect to the mode in which these animals 

 effect their mining operations, in stones and hard 

 madrepore, we have many theories, but nothing 

 positive. That the delicate valves are capable of 

 acting as raspers on such rough dense materials is 

 scarcely to be believed. Is there any solvent used? 

 if so, would not such solvent eat away the shell as 

 well as the rock, and leave the animal to perish? 

 Can it be by the action of incessant currents of 

 water, produced by the vibratile action of the 

 branchiae, directed against the point to be worn 

 down, and that perhaps with more impetus than 

 might be supposed ? Such, we reply, is Mr. 

 Garner's opinion. But for these effects to be 

 produced by such an operation, for the rock to be 

 chambered by little currents of water, and that not 

 in the course of a lapse of years, but with consider- 

 able dispatch, is indeed startling. We know that a 

 perpetual current bubbling from its fountain will 

 wear down the asperities of the rudest granite ; but 

 then time must pass, ages glide away. Here, on 

 the contrary, the rock is bored, the mollusk self- 

 buried, and onwards, mole-like, it drives its levels. 



2014. — The Finger Lithodomus 



(Lithodomus dactt/lus). a, the young with the 

 byssus; 6, the full-grown shell, showing the inside 

 of one of the valves ; c, the valve seen outside ; d, 

 three specimens in a ma.ss of madrepore. This 

 species is very common in the Mediterranean, and 

 is in considerable esteem as an article of food, being 

 plump, juicy, and highly flavoured. It is generally 

 served up in the form of a stew, which is said to be 

 excellent. Cuvier alludes to the agreeable flavour 

 of its flesh, "i cause de son gout poivr^." 



We may now turn to the genus Pinna, on which 

 we have previously ventured a few observations. 



In most cabinets the great fan-like, delicate 

 valves of these shells are to be observed, no one 

 can overlook them ; they resemble huge expanded 

 flattened mussels, with an elongated acute apex, 

 and a dusky roughened surface ; and with them we 

 generally observe large tults of delicate brown 

 byssus, and gloves or similar articles are manu- 

 factured with this silk-like material. 



M. Rang characterizes the shell in this genus as 

 fibrous and horny ; rather fragile, and delicate ; 

 regular, equivalve, triangular, pointed anteriorly, 

 rounded posteriorly. The hinge is linear, striate, 

 and toothless ; the ligament is marginal, a great 

 portion of it internal. Anterior muscular impression 

 small and entirely in the umbonal angle ; posterior 

 muscular impression very large. The mollusk has 

 the lobes of the mantle disunited along their ventral 

 border ; there are no projecting siphons, and the 

 foot is conical or tongue-like, and slender. An 

 elaborate anatomy of this animal, which he calls 

 CliimiJEia, has been given in his great work by Poll 



In the old shells of Pinna we observe a tendency 

 of the valves towards a laminated structure ; but in 

 the young, the lamination is not only more distinct, 

 but the different layers rise up externally, forming 

 rows of fringes or subtubular spines. These wear 

 down as the animal increases, and at last almost 

 entirely disappear. If, however, a young spinose 

 pinna be placed by the side of an adult shell, few 

 would regard them as specifically the same, unless 

 previously aware of the fact ; and indeed, species 

 have been fabricated on this very ground. 



The Pinna), or Les Jambonneaux of the French, 

 attain to a large size. The great Mediterranean 

 Pinna (Pinna flabellum) sometimes exceeds two 

 feet in length. These shells are generally found in 

 deep water, on sandy bottoms, but at no great 

 distance from the shore, on sandy bottoms, moored 

 by the byssus ; it is said that the animal is sometimes 

 fixed by its byssus, and sometimes removes itself by 

 the aid of its foot. 



This byssus, instead of consisting of coarse scanty 

 fibres, is fine, silken, glossy, and abundant. It 

 is employed in Italy for the manufacture of various 

 articles, which find a ready market; it does not, we 



