114 
THE PEARL OYSTER 
remark in Tryons' Conchology " Muller has seen Cerithia 
- bored by Murex Senegalensis, in consequence 
of wbicli the animal dies and opens its operculum, when a 
Turhinella comes to share the feast." In this connection it 
may be noted that on the Ceylon side of the Gulf of Manaar 
the Turbinella is not fished, and is consequently in much 
greater abundance than on the Madras side, where it is 
regularly fished, and yet the Ceylon pearl fisheries suffer no 
injury therefrom. 
Fasciolaria trapezium, Lamark, which is also called a 
chank by the natives, is fortunately much rarer and has conse- 
quently not attracted so much attention ; it has however a 
labial ribbon armed at its tip with rows of glistening lancets 
with which it can bore through a thick shell, and another 
chank which is seemingly Murex trapezium, Lin., is said by the 
divers always to clear a space around it by destruction of the 
oysters, a reputation which I have had no means of testing. 
The Trigger Fish. 
The trigger fish, so named from the trigger-like second 
ray of its first dorsal fin, and called also the file fish, or 
leather jacket from its rough exterior, is said to be another 
enemy of the oyster. The fishermen say there are three of 
them in the Tuticorin seas. The one shown me was Balistes 
mitis. The fishermen say they eat mainly Modiola, and con- 
gregate wonderfully on the beds of these small mussels, and 
never attack any but the very young oysters ; and to this 
agreed the teeth and the contents of the stomach of the one 
full-sized individual I was able to examine. The teeth, 
though sharp, were not strong, and were easily displaced 
by a penknife. The intestine contained chiefly shells of 
Modiola and no oysters that I could detect, and no shells of 
any thickness. Doubtless they do eat yoimg oysters on 
occasion as do all rock fish, and Captains Phipps and Donnan 
have found shells of young oysters in them, but their favorite 
