102 MADRAS FISHERIES BULLETIN [VOL. XVI, 



are to the north-north-west of the Uti group in rather shallower 

 water, 6 to 6% fathoms. 



The bottom on the pars consists of level stretches of continuous 

 rock, brownish tinted calcrete exactly similar to that on the Uti 

 Pars. 



The fauna differs considerably from that of the last-named 

 banks. Sponges are less extensive, Siphonochalina communis being 

 the most conspicuous and numerous. 



Among other animals noted were large Pinna sp. in abundance 

 rooted in the thin layer of sand covering the rock in many places, 

 with Balauus and zoophytes crowding the exposed surfaces of the 

 Pinna ; Eunice tubifex in quantity ; Heteroneid form of Nereis sp. in 

 the canal system of Suberites inconstans; Botrylloides sp. ; Turbinella 

 pirum in the sand on the western side. 



The large fishery of l86l was contributed to from these banks 

 which appear more favourably situated than many others for 

 receiving spat falls, some eight being recorded since 1861. Unfor- 

 tunately in only three instances, 1878, 1884 and IQ02, did the re- 

 stocking take place on an extensive scale — even in 1902 the 

 quantity of I % to 2 years old then present was estimated at but 

 1,700,000, a number too small to give good results two to three years 

 after in view of the unpreventable wastage that must be 

 allowed for. 



In many respects the Cruxian group has points of resemblance 

 with the North and South Moderagam Pars on the Ceylon side, 

 notably in the in-shore situation, the comparative shallowness of 

 the water and in the characteristic abundance and association 

 together of Pinna and Balanus. 



The ground referred to on the Ceylon side is much the more 

 clean of the two, both faunistically and physically ; the sand there 

 is of the usual coarse grit and this, by the attrition of its movement 

 during disturbed weather conditions effectually scours the bank, 

 keeping down the growth of weed and other organisms unprotected 

 by a hard external protective casing. 



This mechanical cleansing of the bottom is nowhere well seen 

 on the in-shore Indian banks where the fineness and low specific 

 gravity of the sand lacks not only an adequate scouring force, but 

 by reason of the presence in it of a certain amount of mud exercises 

 a retarding influence upon oysters when they are present — an 

 influence resulting in a stunting of the growth- 



