228 SPOLIA ZEYLANICA. 



As will be seen from the chart on Plate 2, the four areas, 

 B, C, D, E, on the north side of the main bed contain but few 

 oysters. There are also barren patches on the north-western side of 

 the main bed (sections M and W) , and in the south-western corner 

 (sections U, V, and W). 



The depth and nature of the bottom in the various sections may 

 be made out clearly from the charts published by me in Spolia 

 Zeylanica, Volume VIII., Part XXIX. 



During the examination of the oysters in January, May, June, 

 and September of this year a large number of measurements have 

 been taken, which are given in the Appendices and are shown by 

 means of curves on Plates 4 to 9. 



Area A , Nachchikkuda. — This bed was only surveyed in September, 

 1912. Dived at 22 stations, but oysters found only in the four most 

 northerly stations. Altogether 44 oysters were examined, having 

 an average size of 3" 36 x 3 "70 inches. These oysters have the 

 smallest average size in the whole lake. 



The enclosure erected in Nachchikkuda in January last has been 

 twice stocked with oysters, which have been eaten by predatory 

 fish. In September, 1912, 500 oysters from area J were placed 

 in this area, just south of the enclosure. 



Previous writers have regarded the position of Nachchikkuda as 

 highly favourable for oyster cultivation, lying as it does at a con- 

 siderable distance from any of the rivers opening into Lake Tamble- 

 gam. The only point in its favour, to my mind , is the fact that there 

 is not the same chance of extermination in the event of very heavy 

 rains, but apart from this very important point, the evidence tends 

 to show that the oysters are usually more abundant at the mouths 

 of rivers. The evidence of the last two years shows that the 

 Nachchikkuda bed is inferior to the main bed. 



Area B. — Comprising the whole width of the lake between Periya 

 Vellai Kalmunai and-Kodaipota, it is characterized by the presence 

 of a sandspit which stretches half-way across from Periatmunai. 

 This area is evidently unsuitable for oysters, mainly because of the 

 presence of too much sand. 



Area C. — The north-eastern half of this area does not appear to be 

 potentially suitable for Placuna, as no oysters have been found here 

 during the last tAvo years. The south-eastern half marks the begin- 

 ning of the main central bed, and there are a fair number of this 

 year's oysters present. In May, 9 specimens had an average size of 

 1 ' 59 X 1 • 69 inches, an extremely low average. In June no records 

 were taken, but in September 20 specimens showed an average size 

 of 3 • 89 X 4*11 inches, which is slightly less than the average for the 

 whole bed. Since the oysters present in this area form the fringe 

 of the main bed, it is not surprising that they are rather small. 



Area D. — No oysters have been found in this area during the 

 last two years. 



