374 



MOLLUSCA. 



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

 notch for the byssus. The anterior adductor muscle is as yet excessively little. When the ears are 

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



The most celebrated is the Pearl-mussel (Mytilus mar- 

 (/ariii/erus, Linn.) Its nacred interior is employed in all 

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

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

 sian Gulf, are but e.\cretions of it. The name of Avicula 

 is g-iven to such species as have the ears more pointed, and 

 the shell more oblique. There is in the hinjfe in front of the 

 lio-ament, a vestige of a tooth, ysfhose first trace is indeed to be 

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

 an example from the IMediterranean, remarkable for its 

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

 Fig 187.— Avituh miicropiem. soffiB resemblance to a little shrub. 



Tnii PiNN^, Linn. — 

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

 The animal {Chima>ra, Poll) is elongated in the same direction as the shell, as well as its lips, its 

 branchiae, 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 this 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 nobilis. 



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 Areas, 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 /'.<3~j^!e^'='"T7*K. 

 not meet in the nnddle, because the animal (Daphne, Poll) has in front ,,.,^<^'— ^^♦ips.-^^"^-- ' *>-^ 

 of the abdomen a process of a horny substance, or a tendinous ribbon, in >Ji 'A ' \ 

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

 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 Cuctilliea, some Arcffi in which the teeth at the ends of the 

 hinge assume a longitudinal direction. [In Cucullaea the two valves are tig. iss— Arta Uarb^ta. 

 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-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 tortuusa, Chem., because of its peculiar figure, and 

 its unequally oblique valves. (It is the type of the genus Trisis of 

 Oken.) 



Pectunculus, Lam. — 

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

 cul ir form. The valves close exactly, and their apices are 

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

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

 .1S9.— Pcctuiicuius capalde of creeping. It lives in sand. We have some 



native species. 



