ORDER TESTACEA. 101 
with the most beautiful mother-of-pearl within. The latter 
is employed in the arts, and it is from the extravasation of 
this substance that are produced the oriental or fine pearls, 
taken by the divers at Ceylon, at Cape Comorin, and in the 
Persian Gulph. 
The name of AVICULA is appropriated to such as have 
more pointed ears and a more oblique shell. The vestige of 
a tooth, of which traces are visible in the pintadine, is ob- 
servable on the hinge, before the ligament. 
One species (mytilus-hirundo, Lin.) that inhabits the Me- 
diterranean is remarkable for the pointed ears which extend 
its hinge on each side. Its byssus is coarse and stout, re- 
sembling a little tree. 
PINNA, Lin. 
The pinne have two equal valves, forming a segment of a 
circle, or resembling a half-opened fan, which are closely 
united by a ligament along one of their sides. ‘The animal, 
the CHIMERA, Poli, is elongated, like its shell; the lips, 
gills, and other parts are in the same proportion. Its mantle 
is closed along the side of the ligament; its foot resembles a 
little conical tongue excavated by a furrow; it is furnished 
with a small transverse muscle, situated at the acute angle 
formed by the valves, near which is the mouth, and with a 
very large one in their broader portion. By the side of the 
anus, which is behind this large muscle, is a conical ap- 
pendage peculiar to the genus, susceptible of expansion and 
elongation, the use of which is unknown. 
The byssus of several species of pinna is as fine and 
brilliant as silk, and is employed in fabricating the most pre- 
cious stuffs; such is the 
P. Nobilis, Lin., which is moreover recognized by the 
valves being roughened with recurved and semi-tabular plates. 
