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 j 
less prominent, the species have been named Pintadines, Lam. {Margarita^ Leach). ^jj 
The most celebrated is the Pearl-mussel (Mytilus inar- j 
garitiferus, Linn.) Its nacred interior is employed in all J 
sorts of fancy-work, and the orient-pearls, fished for by jil 
divers, chiefly at Ceylon, at Cape Comorin, and in the Per- i 
sian Gulf, are but e.xcretions of it. The name of Avicula 
is ?iven to such species as have the ears more pointed, and 
the shell more oblique. There is in the hinge in front of the 
ligament, a vestige of 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. 187.— Avicula macropteru. some resemblance to a little shrub. 
The PiNXiE, Linn. — I i 
Have two equal wedge-shaped valves, which are closely united by a ligament along one of their sides. ' 
The animal {Chimcp.ra, Poli) is elongated in the same direction as the shell, as well as its lips, its j 
branchiae, and all the other organs. Its cloak is closed on the side of the ligament ; its foot is of the i 
shape of a conical little tongue, and marked with a groove ; there is a small transverse muscle in the : i 
acute angle of the valves, near which the mouth is situated, and a very large muscle at their widest li 
part. On the side of the anus, which is behind this large muscle, there is attached a conical appen- j -j 
dage, peculiar to this genus, and capable of inflation and elongation, but of the use of which we are i 
ignorant. IP : 
The byssus of several species is as fine and brilliant as silk, and is used in weaving precious stuffs. The chief is | j 
the Pinna nobilis. j 
The Arcace/E {Area, Linn.) — j: 
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. i 
The Areas, properly so called {Area, Lam.), have a straight hinge, and the shell is elongated in a direction 'i d 
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 Cucidlaa, some Arcae in which the teeth at the ends of the 
hinge assume a longitudinal direction. [In Cucullaea the two valves are Fig. 188.— Area barbata. 
not exactly alike, and there does not appear to be a byssus, whence 
Sowerby doubts the propriety of arranging this genus with the Arcaceae.] We ought probably to separate also such I 
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- fl 
rate the Area tortuosa, Chem., because of its peculiar figure, and )i 
its unequally oblique valves. (It is the type of the genus Trisis of u 
Oken.) 
Pectunculus, Lam. — | 
Has the binge in a curved line, and the shell of a lenti- 
culir form. The valves close exactly, and their apices are H 
near each other. The animal {Aocinea, Poli) has a large 
compressed foot, with a double lower margin, and is hence » 
Fig. 189 .— Pectuiicams Capable of Creeping. It lives in sand. We have some 1 
native species. j 
