3G6 



Div. 2. I^IOLLUSCA.— ACEPIIALES. 



Class 4. 



tlie month of tlm animal. The anterior side, a little under the angle of the side of the mouth, has a 

 notch for tlie hvssus. The anterior adductor muscle is as yet excessively little. Wlien the ears are 

 less prominent, the species have been named Pintadincs, Lam. {Margarita, Leach). 



The most celebrated is the Pearl-mussel (Mt/tihts mar- 

 garitiferus, Linn.) Its nacred interior is employed in all 

 sorts of fancy-work, and the orient-pearls, fished for by 

 divers, rhielly at Ceylon, at Cape Comorin, and in the Per- 

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

 is given to such species as have the ears more pointed, and 

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

 ligament, avestigeof a tooth, whose first trace is indeed to be 

 detected in the Pentadines. The Mytilus hirundo, Linn , is 

 an example from the Mediterranean, remarkable for its 

 lengthened auricles : its byssus is large and strong, and has 

 Fig IS;.— AvicuU ma. r"i it[.i. souie rcsemblancc to a little shrub. 



The PinnyE, Linn. — 

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

 The animal {Chimo'.ra, Poli) is elongated in the same direction as the shell, as well as its lips, its 

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

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

 acute angle of the valves, near which the mouth is situated, and a very large muscle at their widest 

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

 dage, peculiar to tliis genus, and capable of inflation and elongation, but of the use of which we are 

 ignorant. 



The byssus of several species is as fine and brilliant as silk, and is used in weaving precious stuffs. The chief is 

 the Pinna nobilit. 



The Arcace^ {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 Arccp, properly so called (Area, Lam.), have a straight hinge, and the shell is elongated in a direction 

 parallel to the hinge. The apices of the valves are generally protube- 

 rant, and curved towards the hinge, but widely apart. The valves do 

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

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

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

 affixed 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 Cucullcea, some Area; in which the teeth at the ends of the 

 hinge assume a longitudinal direction. [In CuculUca the two valves are 

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



Sowerby doubts the projuiety of arranging this genus with the Arcaces.] We ought probably to separate also such 

 species ag have well-marked ribs, and whose 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., brcause of its peculiar figure, and 

 its unequally oblique valves. f>4.. s Vne type of the genus 7V/,v/4- of 

 Oken.) 



Pectunculus, Lam. — 

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

 cid ir form. The valves close exactly, and their apices arc 

 near each other. The animal {Axinea, Poli) has a large 

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

 capable of creeping. It lives in sand. We have some 

 native species. 



Fig. 183.— .-Vrca barbatn. 



Jig. 139.— PcttJi CHIOS. 



