l growth.]

The banks of Aripo are not the only localities, nor is the _acicula_ the
only mollusc, by which pearls are furnished. The Bay of Tamblegam,
connected with the magnificent harbour of Trincomalie, is the seat of
another pearl fishery, and the shell which produces them is the thin
transparent oyster (_Placuna placenta_). whose clear white shells are
used, in China and elsewhere, as a substitute for window glass. They are
also collected annually for the sake of the diminutive pearls contained
in them. These are exported to the coast of India, to be calcined for
lime, which the luxurious affect to chew with their betel. These pearls
are also burned in the mouths of the dead. So prolific are the mollusca
of the _Placuna_, that the quantity of shells taken by the licensed
renter in the three years prior to 1858, could not have been less than
eighteen millions.[1] They delight in brackish water, and on more than
one recent occasion, an excess of either salt water or fresh has proved
fatal to great numbers of them.

[Footnote 1: _Report of_ Dr. KELAART, Oct. 1857.]

[Illustration: PEARL OYSTER.

1, 2. The young brood or spat.
3. Four months old.
4. Six months old.
5. One year old.
6. Two years old.]

[Illustration: THE PEARL OYSTER. Full Growth.]

On the occasion of a visit which I made to Batticaloa. in September,
1848, I made some inquiries relative to a story which had reached me of
musical sounds, said to be often heard issuing from the bottom of the
lake, at several places, both above and below the ferry opposite the old
Dutch Fort; and which the natives suppose to proceed from some fish
peculiar to the locality. The report was confirmed in all its
particulars, and one of the spots whence the sounds proceed was pointed
out between the pier and a rock that intersects the channel, two or
three hundred yards to the eastward. They were said to be heard at
night, and most distinctly when the moon was nearest the full, and they
were described as resembling the faint sweet notes of an AEolian harp. I
sent for some of the fishermen, who said they were perfectly aware of
the fact, and that their fathers had always known of the existence of
the musical sounds, heard, they said, at the spot alluded to, but only
during the dry season, as they cease when the lake is swollen by the
freshes after the rain. They believed them to proceed not from a fish,
but from a shell, which is known by the Tamil name of (_oorie cool