66 MADRAS FISHERIES BULLETIN [VOL. XVI 



about 8 miles to the east of Hare island. There we commenced 

 the examination, the day's work extending over the southern half 

 of the bank, with traverses extending some distance beyond the 

 charted margin. This bank, which yielded fisheries in 1784, 1787, 

 1807, 1810, 1822, 1830, 1889 and 1890, has generally been considered 

 one of the most favourable for rearing oysters to maturity, and to 

 be fully the equal of any other bank in respect to the number of 

 spat falls reported upon it during the past half century. 



It possesses by far the largest area of any productive Indian 

 bank, its charted outline being 7 miles long with a width varying 

 from one mile to two miles. The depth varies from 8 to II fathoms. 

 Our examination showed the bank to consist of a somewhat 

 uneven, but not rugged, rocky framework rendered level by the 

 accumulation of sand in the depressions. Here and there the rock 

 shows bare save for a thin veil of sand, but the greater part is 

 covered by sand varying from I and 2 inches to 6 inches and a foot 

 in depth. 



The sandy bottom appears to the divers as broken up by a 

 multitude of rocky outcrops usually of limited extent and from this 

 circumstance we may infer the origin and propriety of the name 

 "Tolayiram," literally " nine hundred." 



The surface of the bank shows considerable local diversity — 

 both physical and faunistic. In some places a rocky surface 

 sprinkled lightly with sand bears loose blocks of calcrete (recently 

 formed rock) of varying size; elsewhere fragments of Madrepore 

 coral branches, corroded and water-worn, lie loose, here sparsely 

 scattered, there abundant. In other places deep sand, bare of any 

 life, largely preponderates. Variation in every proportion is 

 represented. 



The sand is altogether different from that on the Ceylon side. 

 Instead of being clean large-grained quartz grit, as there, the sand 

 of the Tolayiram Par is fine in grain, the angles well rounded ; 

 chemically it is composed principally of calcium carbonate- 

 comminuted shell fragments in the main. 



In colour it is yellowish brown and there is always associated 

 with it a certain, though variable, amount of mud particles, which 

 rise with every movement upon the bottom — the scramble of the 

 divers, the under-tow of strong currents. 



The majority of the diving descents made upon the bank proper 

 showed the greater part of the area examined to be thickly covered 



