6 CEYLON PEARL OYSTER REPORT. 



banks, depths of between 1000 and 2000 fathoms are reached. On our two cruises in 

 the "Lady Havelock " we made a careful examination of the ground in several places 

 outside the banks, to the westward, on the chance of finding beds of adult oysters 

 from which possibly the spat deposited on the inshore banks might be derived. No 

 such beds, outside the known " paars," were found ; nor are they likely to exist. The 

 bottom deposits in the ocean abysses to the west of Ceylon are " globigerina ooze" 

 and "green mud," which are entirely different in nature and origin from the coarse 

 terrigenous sand, often cemented into masses, and the various calcareous neritic 

 deposits, such as Corals and Nullipores, found in the shallow water on the banks. 

 The steepest part of the slope, from 10 or 20 fathoms down to about 100 fathoms or 

 more all along the western coast, seems in most places to have a hard bottom covered 

 with Alcyonaria, Sponges, deep-sea Corals, and other large encrusting and dendritic 

 organisms. Neither on this slope, nor in the deep water beyond the cliff, did we find 

 any ground suitable for the pearl oyster to live upon. 



It soon became clear to us that different paars were placed under very different 

 physical and biological conditions, and that the sudden disappearance, or the continued 

 absence, of pearl oysters in different localities and at different times might be and 

 probably was due to very different causes. The Periya Paar, about 20 miles from 

 land and close to the top of the steep slope (see p. 78), is very differently situated 

 from the East Cheval or the Modragam paars relatively near the shore, protected to 

 some extent from the ocean and with shallow water all around. The pearl oyster is 

 the same animal all over the district, and facts of anatomy and physiology once 

 ascertained will hold good ; but the paars are different, each presents its own problems, 

 and all must be studied. In reading the reports of former superintendents and 

 inspectors of the pearl banks, it is possible, after acquiring some knowledge of the 

 physical and biological conditions of the various paars, to account for some of the 

 apparently mysterious disappearances of oysters and catastrophic changes in the fauna. 

 It is unnecessary to go over all the cases that have been recorded, but the recent 

 history of the Periya Paar, and the more noteworthy disasters on the Cheval and other 

 important paars, will be found discussed below. For a knoAvledge of the past history 

 of the pearl banks we are indebted mainly to the official reports of the Ceylon 

 Government. I would mention especially as amongst the most important contributions 

 to our knowledge of the subject : the reports of Dr. E. F. Kelaart in 1857 to 1859; the 

 " Account of the Pearl Fisheries of Ceylon," by Captain James Steuart, Ceylon, 1843 ; 

 H. Sullivan Thomas' " Report on the Pearl Banks and Fisheries of Tuticorin " ; 

 "The Pearl and Chank Fisheries of the Gulf of Manaar," by E. Thurston (Bulletin 

 of the Madras Museum, No. 1, 1894) ; Mr. E. W. H. Holdsworth's "Report on the 

 Pearl Oyster Banks," 18G7; Captain J. Donnan's successive Reports on Inspections 

 and Fisheries ; and finally the comprehensive and most interesting " Report on tbe 

 Ceylon Pearl Fisheries," drawn up in 1899 by Sir William C. Twynam, K.C.M.G. 

 (Colombo, 1900). 



