Reports to the Colonial Office. 177 



beds. The crab is also said to be injurious, cutting the byssus of the 

 oyster. A note is given on page 6 regarding an enemy that makes a 

 round hole in the oyster shell ; this mysterious enemy is one of the 

 carnivorous whelks. 



Evidently, from the report, numerous small mollusca prey on the pearl 

 oysters. Two fish, the Trigger Fish {Balistes mitis) and skates (Trijgoii 

 irarnah), also do much harm. On page 5 it is stated that " the numerous 

 rock fish which abound on the Arippu banks feed on oysters . . . the quan- 

 tity devoured by these voracious fish must be considerable." Later, it is 

 stated to be useful, as it preys on the injurious Suran or mussel. Skates of 

 several unknown species are referred to as very destructive. Divers, both 

 European and native, give various tales as to the damage done by sea 

 snakes, but nothing authentic is given. 



Floods of fresh, muddy water are stated to be most injurious. 



Little definite seems to be recorded as to the age of pearl oysters, but 

 it is stated " that oysters may be profitably fished at the age of four years, 

 and that they are in their prime at five years, and may be kept till that 

 age if circumstances permit of it, but if they are kept until the sixth yea- 

 they are almost certain to be found dead." The best time to fish then: 

 however, does not appear to be settled. 



The advisability of retaining native divers is entered into at some 

 length, their superiority over the European at this work being clearly 

 pointed out. Their reward is now raised to one-third of the oysters 

 collected. Recommendations to start a chank fishery in the neighbour- 

 hood of the pearl banks are given. One fishery exists north of Manaar 

 Islands, about 2,000,000 chanks being exported from Jaffna to Calcutta. 

 Ths chanks are used as ornaments by the Hindus. 



The main body of the report (39 pages) is taken up by eight appendices. 

 The first dealing with spat, true and false ; enemies of the oyster ; chank 

 fishery ; age of the pearl oyster and artificial culture ; being extracts from 

 the report of Mr. Thomas, Madras Civil Service, to the Government of 

 Madras, on the Pearl Banks and Fisheries of Tuticorin. 



The most important part in this report regarding the true spat is here 

 reproduced : — 



" The challenged spat in the largest shell which I have seen is 

 4-i sixteenths of an inch from binge to contour rectangularly at its 

 widest point, and the largest drawing in Sir J. Emerson Tennent's 

 work is no more ; it is, therefore, so small as to need very close 

 examination. Looked at under a hand lens and under a low power 

 microscope, I made it out to differ from the shell of the pearl oyster 

 in being much more convex, more oblique ; in having the ear on the 

 short side, not produced in an almost straight line, but rounded off 

 and turned up instead of being flat ; in having the right valve fitting 

 deeply into the left valve, with the edge of the right valve turned back at 

 about an angle of 45° for the whole contour in some, for others only from 

 the sinal ear to half way round the contour, instead of _ the two vaJre^i 

 meeting each other nearly fiat, as in the pearl oyster ,■ in having none of the 

 spines with which the pearl oyster is covered, and distinctly different 

 flanges ; in having no algce adhering to it ; in having the umbones more 

 anterior or advanced beyond the hinge line ; in adhering to weed, said to 

 be Saragossum vidgare, instead of to rock and such-like hard substances 



