104 



CEYLON PEARL OYSTER REPORT. 



South Cheval. Unlike the eastern and western regions to the north, a remarkable 

 uniformity characterises the whole of the southern part. The bottom is very level 

 and is composed of sand and shell gravel, the latter chiefly the broken and worn 

 fragments of pearl-oysters, Pectunculids, and Cockles. Scattered about in great 

 profusion lie also fragments of dead coral, calcareous rock, shell-conglomerate, balls uf 

 Lithothamnion (fig. 31), from the size of a hazel nut to that of a cricket ball, and dead 



Fig. 31. Nullipore ball (Lithotluimnion fruticulosum) with tags of byssus where pearl-oysters have 

 been attached (to the right), and similar ball still covered with young pearl-oysters (to the left); 

 natural size. 



shells. These fragments rarely exceed G inches in diameter, but some larger blocks ot 

 rock lie buried under the sand. Very rarely, however, is there any sign of extensive 

 rock, such as is seen in the more northern parts of the paar, and none rises above the 

 surface. This, like so much of the ground on the pearl-banks, is excellently suited 

 for dredging over. 



The pearl oysters lie for the most part loose on the sand in bunches, each bunch 

 having in its centre one of the fragments of coral, rock, or nullipore. Often one 

 oyster has three or four small stones and shell fragments entangled together m its 

 byssus, while other individuals, usually younger, cling to its valves. There may be 

 any number from 3 or 4 up to 15 or 16 oysters in a bunch. Some of the bunches 

 (fig. 32) are formed of young and old individuals, ranging from I month up to nearly 

 4 years of age, joined together. 



Non-calcareous Algas are scarce here, Pentaceivs and Holothurians are fairly 

 common, and the Hydroid Zoophyte Campamdaria junaea is characteristic of the 

 eastern end and extends north along the East Cheval. SpongioneUa nigra, Famjiu 

 dentata, and Astrseid Corals are also common, and a large mass of the delicate 

 Annelid tubes, Filograna, was obtained near the shoal buoy. Dead oyster shells are 

 very abundant at the eastern end, and it is here that we find the occasional lumps of 

 shell-conglomerate formed of pearl oyster valves up to 4 years old, shells and casts of 



