ON ACEPHALA. 387 
thick bivalve shells, such as the wniones, and more particu- 
larly by the pearl-mussel, vulgarly called the pearl-oyster, 
M. margaritaceus of Linneus, and the old conchologists, 
avicula margaritacea of Bruguiéres, and finally, the pinta- 
dina margaritacea of Lamarck. In all the countries in which 
it exists, as in the Gulf of Mexico, (if indeed it be the same 
species) in the Red Sea, in the Persian Gulf, on the coasts 
of Japan, and especially in the Indian ocean on the coast of 
Ceylon, it has given rise to regulated fisheries, and to a very 
considerable commerce, as it would appear, from time imme- 
morial. 
This fine species of shell exists in considerable banks, at- 
tached by its byssws, or beard, to the submarine rocks, some- 
what like the mussels, and as it would appear, constantly at 
considerable depths. ‘There are many such banks in the 
Gulf Manaar, island of Ceylon, at Arippo, Condatchy, and 
Pomparippo. The most considerable is said to occupy a 
space of twenty miles opposite Condatchy. To prevent the 
useless destruction of a great number of individuals, the bank 
is divided, as it were, into regular cuts, pretty nearly like the 
banks of coral on the coast of Sicily, that is to say, it is di- 
vided into seven parts, which are worked successively every 
year, because it is supposed that these animals, in that space 
of time, attain the full size of which they are capable, and that 
if they were left longer, the pearls would become troublesome 
to the animal, and that it would finally expel them from the 
shell. Be this as it may, in the commencement of February, 
when the fishing begins, to end in April, all the boats which 
are to be employed in it, assemble in the bay of Condatchy, 
whither they come from different parts of the continent, and 
from the isle of Manaar. At ten o’clock at night, on a signal 
given by cannon, the boats set out together, so as to be upon 
the bank where the fishery takes place, at break of day, which 
is the hour of commencement. Each bark is manned by 
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