NARRATIVE. 



39 



7 P.M. in Trincomalee harbour the temperature was 78 F. and the specific gravity 

 L - 0202. The entrance to Tamblegam is obstructed by a long curved sand-spit on the 

 south and a number of scattered rocks and reefs on the north, so the steamer was 

 unable to get within a mile or more of the channel. From there we sailed in the 

 ship's gig with a strong easterly wind which carried us into the lake in fine style, 

 lint gave considerable trouble when we tried to return in the afternoon. The passage 

 was found to be too narrow and too much obstructed to beat out against the wind, 

 and when we lowered the sails and started to row out through the breakers now 

 coining in from Great Bay, first one and then a second of the six oars broke, followed 

 by the snapping off of one of the brass rowlocks at a critical moment. The boat then 

 made way very slowly, dodging where possible behind the rocks at Noddi Tevu, and 

 so eventually got through the worst of the sea and out of the narrow channels into 

 the open bay. 



Lake Tamblegam has long been known as the scene of a fishery of the flat thin 

 "window-shell" oyster, Placuna placenta, a remarkable form (see fig. 4) in which 



Fig. 4. Placuna placenta, from Lake TamMegam; half natural size. A, outside of shell; B, inside; 



C, edge view. 



an exceedingly thin body is contained or compressed between two almost flat 

 discoidal valves of considerable size (up to (J inches across) which can easily by scraping 

 off the outside be rendered at least translucent to light, and are said to be used as 

 window-panes in Chinese huts and at Goa. Pearls are not unfrequently found in 

 these window-shell oysters and profitable fisheries have been held in the past at 

 Tamblegam. The pearls are mostly small and these are said to be exported to India 

 to be calcined to make chunam for betel-chewing. We did not on this visit see any 

 living specimens of Placuna, although Mr. Hornell has seen them since ; but the 

 great gleaming piles of dead shells seen at various points along the shore (fig. 5) 

 were evidence of the enormous numbers that had been taken in the former fisheries, 

 and especially at the last fishery fifteen years ago, when the stock in the lake seems 

 to have been nearly cleared out. There were also in places heaps of piled up rock- 



