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MOLLUSCA. 



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posterior niarg-in to that of the opposite valve : those five pieces cover the whole of the clonk. From the place 

 where the lig;ariieiit should be spriiif^s the fleshy peduncle. A strong adductor nmscle unites the two \atves near 

 their beaks. The mouth of the animal lies concealed behind them, and the posterior 

 end of the body, with all its little articulated feet, comes out a little'further dowi 

 between the first four valves. The widest spread species in our seas (Lcpas auoiifa t 

 Linn.) has ;^ot its name from having g-iven rise to a fable of its being the orif^^inal < 

 parent of the Bai-uacle-goose. They grow attached to rocks, piers, to the bottom f 

 ships, &:c. AVe may distinguish the PolUcipes, Leach, which, besides tlie five prit 

 cipal valves, has several small ones near the pedicle. In some species these vah ■. 

 almost equal the primary in size. There is often an odd one opposite the noru I 

 odd one. [^ScalpeUum, Leach, consists of thirteen valves, six on each side and oi 

 dorsal; and its peduncle is squamose.] C'//(erff.y, Leach. — The cartilaginou3 clo^k 

 incloses five valves, but of small size, so as not to occupy the whole surface. Otlo 

 Leach. — The cloak containsonlytwo very small valves, with three little pieces whi li 

 scarcely merit that name ; and there are two tubular appendages in the shape of ear-^ 

 Tetraliwiis, Cuv., has only four paired valves encircling the aperture, two beir^ 

 longer than the others. The animal is partly contaitied in the pedicle, which is wide 

 and hirsute. They are, in some degree, Balani without a tube. [Liihotrya, Sow., 

 is pedunculated like Anatifa, but has, at the base of the peduncle, a shelly appendage 

 analogous to the testaceous base of Balanus, and possesses besides a peculiarity not 

 to be found in any other g-enus of this cla^s, that of penetrating stones for its habi- 

 tation.] 



The Balanus, Brug., or Acorn-Shells. 

 The principal part of the shell consists of a testacous tube attached to various bodies, the aperture 

 of which is more or less chjsed by two or four valves. This tube is formed of various pieces or com- 

 partments, which ap])ear to unloose or separate in proportion as the growth of the animal requires 

 additional room. The branchiae, the mouth, the articulated tentaeula, and the anal tube, dilfer little 

 from the same parts in the Anatifa. 



In Balainis, properly so called, the tubular portion of the shell is a truncated cone, formed of six outer valves, 

 separated by as many inner ones, three of which are narrower than the others. Their base is usually formed of a 

 calcareous lamina, fixed to various bodies. The four valves of the operculum close the aperture exactly. The 

 rocks, shells, and piers of all our coasts are, in a manner, covered with a species, the 

 Lepas balnniis, Linn. 

 // --" Y x-i- There have been separated from these the y^ica^/rt, Leach, whose base is irregular, con- 



\/J:' ^: ■''■,.•}'('', ve\" outwardly, and not fixed : the greater number live within sponges. [Sowerby reunites 

 Acnsta to I'alanus.] Conia, Blainv., whose shell has only four exterior valves. [On the 

 ciMitrary, in the Ocfomeris, Sow., the pieces or valves amount to eight.] A.\vitia, Rauz., 

 whose shell has no well-marked exterior valves. Pyrooma, Sav-, whose shell forms a very 

 depressed cone, with only a very small apei-ture, almost as in a shell of the Fissurella. 

 0fV////CA7*-/, Ranz., which have only three outer valves, and a bivalved operculum. Crcusia, 

 Leacli, wirh four outer valves, and a bivalved operculum. M. de la Lamarck sepa- 

 rates, under the name of CoronulOj the depressed species in which the 

 valves are loosely cellular ; and under that of Ti/i?c/??('/Zo', the species which 

 form an elongated cone, but narrowest at the base, and girded with rings that 

 mark the successive epoclis of its growth. There are species of both genera 

 which plant themselves on tlie skin of "Whales, and penetrate into their lard. 

 Diailcma, Ranz.— The shell is almost spherical, and has otdy two small 

 valves, almost concealed in the membrane that closes their operculum. The 

 opercula do not shut the aperture entirely without the aid of the mem- 

 brane that unites them. They also live iipnu AYhales; and we often lind Otiuns attaclu 







rif- 





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Fi,;. I'ir.-CoLLinru.liata 



■tl to their surface. 



