L58 CEYLON PEAEL OYSTER REPORT. 



pores, corals and Sabellaria. Lithotfiamnion fruticulosum was the commonest species 

 among the Nullipores, and many of the balls were overgrown with Polyzoa and worm 

 t iihes, and fine sand frequently adhered in the spaces between the branches. 



On breaking, the exterior was seen to he white and compact (Plate I., fig. 4), while 

 the interior consisted of a brick-red spongy mass, almost of a powdery consistency and 

 containing grains of sand. A thin slice examined under the microscope showed the 

 white margin to be composed of fresh Nullipore with clusters of quartz grains and 

 magnetite enclosed and irregularly disposed. Nearer the interior the plant structure 

 became less distinct, and no trace of structure could be distinguished at the centre. 

 The spongy core evidently has resulted from the breaking down of the Nullipore and 

 the staining is due to the hydration of the magnetite. The sand can be accounted for 

 by irregular growth of the Nullipore enclosing grains attached to the surface. 



Two pieces of calcrete from C h i 1 a w P a a r were very like those obtained from 

 Dutch Modragam, except that the grains were larger and less uniform in size. 



Jokenpiddi Paar. The floor is found to be composed of a very coarse calcareous 

 conglomerate. It contains large well-rounded clear quartz, felspars, and rounded 

 pieces of a brown limestone resembling that described from Cheval Paar. Simple 

 Corals, Clinmn, and tangled masses of calcareous worm tubes cover the block, and 

 colonies of Polyzoa find lodgment in sheltered cavities. A delicate tracery of Polyzoa 

 can be seen among the sand grains on a freshly fractured surface (Plate I., fig. 3). 



Karkopany Paar, lying off Chilaw at 7 \ fathoms, consists of a medium grained 

 calcrete with a few large well-rolled pebbles of quartz of larger size. Dark brown 

 ochreous patches occur in places. Some parts are compact, others loosely cemented. 

 Polyzoan walls can be seen with the naked eye all through the mass cementing and 

 covering the grains. Large shells, corals, and worm tubes cover the exterior. 



Oolawittee Paar lies north of Negombo, at %\ fathoms. Here two samples were 

 obtained. Thev consist of a loose sandy reddish-brown material, with a white coating 

 of Polyzoa completely covering the exterior. Simple Corals, Chama and worm tubes 

 are attached to the surface, the latter being mostly found lining the walls of cavities. 



The rock from Negombo Paar is exactly like that obtained from Oolawittee. 

 In a thin section we see clear quartz and felspar embedded in a dark brown opaque 

 matrix. Polyzoa structure is visible, and can readily be traced out from among the 

 sand grains. 



General Remarks. 



Li considering the deposits as a whole, one cannot help commenting on the fact 

 that nothing has been found in them which gives the slightest clue to the character 

 of the solid rocks forming the bottom of the sea. All are of recent origin and can he 

 accounted for by the action of causes now at work. Rivers bring down large 

 quantities of disintegrated material from the interior of the land, particularly in the 

 season of the south-Avest monsoon ; this is spread over the sea floor by the combined 



