DESCRIPTION OF THE PEARL-OYSTER BANKS OF THE GULF OF MANAAR. 109 



sand. The samples we obtained were calcretes, largely encrusted with Polyzoa and 

 Nullipores, and some shell conglomerates (fig. 35) formed of casts of the valves of 

 pearl oysters, Cardium, Pectunculus, Murex, 

 and Cerithium. Here and there the sur- 

 face of the rock is exposed and coated by 

 Nullipores and other encrusting organisms, 

 and there pearl oysters (fig. 36, o.), or the 

 marks of their byssus (b.), are found in 

 quantity. Many crushed valves and broken 

 fragments were also seen, showing that 

 many more pearl oysters had been present 

 lately. We attribute the destruction in 

 this case to the carnivorous fish Trygon 

 uarnak browsing over the bottom. 



Very little coral is present here a few Astrseids only were found. There is some 

 Sargassum and a few other Algse (Acetabularia, Laurencia, and Lithothamnion balls), 



Fig. 35. 



Shell conglomerate from Periya 

 Paar Kerrai. 



***i 





-U.j) 1 



Fig. 36. Diagram illustrating the distribution of pearl-oysters and old byssus on " rock " and sand. 



some black sponge (Spongiondla nigra), a few trepang (Holothuria atra), and some 

 starfishes (Pentaceros linchi). This paar yielded important fisheries in 1833, 1835, 

 1836, and then was not fished until 1903. 



Outer or True Vankali Paar. 



This lies 2 miles north-west of Periya Paar Kerrai, and about 14 miles due west 

 of Aripu. It is 1|- miles in diameter and the depth is 6^ to 8h fathoms. 



The bottom is flat " rock" covered with very many dead shells of pearl oysters, and 

 other Mollusca, with comparatively little sand. 



Amongst the other animals noticed were : 



Spongionella nigra, Astrseids (small colonies), Juncdla juncea, Antedon black and 

 grey on the Gorgonids, Psoitis sp., Balanus sp. (large), Galathea comatulorum (this 

 and a similarly coloured Myzostomum were attached to the Antedon), Turbinella rapa, 

 Murex regius and some fishes (Labridse and species of Balistes). 



