448 CEYLON PEAEL OYSTER REPORT. 



currents, and over- washes of sand which may sweep away or bury a promising bed ; 

 and lastly man who comes periodically from above on his diving stones and clears the 

 bank of its tens of millions of oysters, old and young. The carnivorous fishes and the 

 monsoons cannot be controlled ; but to show that much can be done by man to mitigate 

 their influence, and to compensate for the decimation necessarily caused by his own 

 operations, has been the chief object of the present Report. 



EXPLANATION OF THE PLATES. 

 PLATE I. 



Some Enemies of the Pearl Oyster. 



Fig. 1. Pentaceros linchi, de Br.. Reduced to one-third natural size. 

 2. Modiolus barbdtns, Linn. The " Suran," in its nests or entanglements. 

 3. A, B, C, D, the following four large Chanks, from left to right : 



A. Murex ra/mosus, Linn. The elephant chank. 



B. Fasciolaria 1/rwpeziwn (Linn.). Chank. 



C. Turbinella pi/rum, Linn. The common chank. 



D. Turbinella rwpa (Linn.). The sacred chank possibly only a form of the last species. 



PLATE II. 



Some Characteristic Animals of the Pearl Banks. 



Fig. 1. Pe/rosia teshidinaria (Lamk.). Reduced one-half. 



2. Phakellia ilonnani (Bc-WEBB.). Nat. size. A, flabellate ; B, cup-shaped form. 



3. Aulospongus tubulatus (BOWEBB.). Nat size. 



4. Phyllospongia holdstoorthi (Bowerb.). Reduced one-half. 



,, 5. Halicoinaria insignia, Allman. Reduced to one-fourth. 



,, 6. Campanularia juncea, Allman. Reduced to one-third. 



7. A living pearl oyster, Marga/ritifera vulgaris, ScHUM., covered with many encrusting and adhering 

 organisms ; slightly reduced. 



