Ji4 



MULLUSCA. 



^ 



a little under the angle of the side of the moath, has a 

 muscle is as yet excessively little. When the ears are 

 iiiloiVmes, Lara. (Marf/ortta, Leach). 



Tlie irioi^t celebrated is the Pr-arl-mussel (M/jfili'-'i mnr- 

 ']nrififp-i-i(x, Linn.) Its nacred interior is employed in all 

 sorts of fancy-worli, and the orient-pearls, fished foi- hy 

 divers, chiefiy at Ceylon, at Cape Cujnorin, and in tlju Per- 

 sian Gulf, are but excretions of it. The name of Ariridn 

 is ;n\'en to such species as have the ears njore pointed, and 

 the shell more oblique. There is in the hin;^e in front of the 

 I.Liainent, a vestie;eof a tooth, whose first trace is indeed to be 

 detected in the Pentadines. The M>//ilus hini n do, L\nn , is 

 ■Au exaniiile from tlie Mediterranean, remarkable for its 

 ii'ni,'"thened auricles : its Ityssns is larL,''e ami slron;,'', and has 

 some resemblance to a little shrub. 



TiiK I'lxxx.s, Linn, — 

 Have two equal wedge-shaped valves, whicli arc closely united by a ligament along one of their sides. 

 The animal {Chimcpra, Poli) is elongated in the same direction as the shell, as well as its lips, its 

 hranchife, and all the other organs. Its cloak is closed on the side of the ligament; its foot is of ihe 

 shape of a CDnic. 1 little tongue, and marked with a groove ; there is a small transverse muscle in the 

 acute angle of the valves, near whii h the mouth is situated, and a very large muscle at their \Aidest 

 part. On the side of the anus, which is behind this large muscle, there is attached a conical appen- 

 dage, peculiar to this genus, and capable of inflation and elongation, hut of the use of \\liich we are 

 ignorant. 



The byssus of several species is as tine and brilliant as silk, and is used in weavinp; precious stulTs. The chief Js 

 the Pinna nobilis. 



The Arcace/E {Area, Linn.) — - 

 Have the valves equal and transverse, that is to say, the hinge occupies the longest side. It is fur- 

 nished with a great number of small teeth, interlocking with each other; and with two nearly equal 

 adductor muscles inserted towards the two extremities of the valves. 



The Arc.T, properly so caller! {Arca^ Lam.), have a strai2;ht hinge, and the shell is elongated in a direction 

 par;il!el to the bin^e. The apices of the valvee are generally protube- 

 rant, and rurved towards tlie liing-e, but widely apart. The valves do 

 not meet in the middle, becavise the animal (Daphne, Poli) has in front 

 of the abdomen a process of a horny substance, or a tenilinous ribbon, in 

 lieu of afoot, which passes out thence, and by which the animal is 

 atfixed to submarine bodies. These shells reside near the shore in 

 rocky places. They are usually covered with a velvety epidermis. They 

 are in little request for the table. There are some species in the Medi- 

 terranean ; and a great number of fossil species, particularly in Italy, 

 in depositions anterior to the chalk. M de Lamarck separates, under 

 the name of C'ucnllien, some Arcae in which the teeth at the ends of the 

 hinge assume a longitudinal direction. [In Cuculla?a tlie two valves are i-ti;, ivs — irci i..iri.;,tri. 



not exactly alike, and there does not appear to be a byssus, whence 



Sowerby doubts the propriety of arranging' this genus with the Arcacea\] "We ought probably to separate also such 

 species as have well-niarkcd ribs, and \^llns,e valves meet closely and completely, for there is thus reason to believe 



that the animal is not fixed, and may rather resemble that of 

 the Pectunculus. There Is assuredly still greater reason to sepa- 

 rate the Area tortuosa, Chem., because of its peculiar figure, and 

 its nncipiidly ubliqnt; valves. (It is the type of the genus Trisis of 

 Oken.; 



pECTUNCtTLUs, Lam. — 

 lias the hinge in a curved line, and the shell of a lenti- 

 culirl'orm. The valves close exactly, and their apices are 

 near each otlicr. Tlie animal {Jxinea, Poli) has a large 

 compressed foot, with a doidile lower margin, and is hence 

 riipable of creeping. It hves in sand. AVc have some 

 n,iU\e species. 



Fig. 189.— Plh 



