380 
SHELLS. 
[Chap. XI. 
the inspection served only to suggest the prospect (which 
has since been realised) that in time the income from 
this source might be expected to revive ; — and, forced 
to content ourselves with this anticipation, we weighed 
anchor from Condatchy, on the 30th March, and arrived 
on the following day at Colombo. 
The banks of Aripo are not the only localities, nor is 
the avicula the only mollusc, by which pearls are fur- 
nished. 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 de- 
light 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. 
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 
given from drawings made for the at four months old, No. 3. No. 4, 
Official Inspector, and exhibiting sis months. No. 5, one year. No. 
the ascertained size of the pearl 6, two yews. The second plate 
oyster at every period of its growth, exhibits the shell at its full growth, 
from the "spat" to the mature 1 Report of Dr. Kelaart, Oct. 
shell. The young "brood" are 1857. 
shown at Nos. 1 and 2. The shell 
