Vol. XI, Nos. 5 & 6.] Pearl Fishery in Palk Bay. 159 
[N.S.] 
Such conditions as these are impossible for the pear! oyster, 
and indeed for any lamellibranch, except such forms as Placuna 
, which has evolved a greatly compressed body and 
highly flattened disc-shaped valves, admirably adapted to 
suitable—from 8 to 9 fathoms on sandy bottom interspersed 
with flat masses of calcareous rock. I have no hesitation in 
ideal for pearl oyster prosperity, being a dirty dark greyish 
blue mudd sa i thin layer of mud, when 
bic the ratio of mud present in the sand decreases markedly, the 
ttom being usually a brownish sand of somewhat varying fine- 
88 mix sometimes with a large proportion of shell fragments. 
dartz grit so conspicuous a feature of the best Ceylon banks 
'S Wholly absent. The bottom fauna living in this shallow 
"ater area is dant. Sometimes, as 
generally enormously abundan 
M *r much of the aeena between iy and 5} fathoms thousands 
