1922] MADRAS PEARL FISHERIES 89 



to be of two generations, the one four to five months, the other 

 ranging from six weeks to two months. 



Sponges were not obtrusive ; several specimens of the peculiarly 

 massive Petrosia testudinaria were seen but the commonest species 

 was one which interiorly is yellow, while the exterior is more or 

 less tinted with pale green. In its growth it envelopes much sand 

 in its substance, which is generally level with the sand surface, 

 sending up stout tapering branches at intervals. Its general 

 appearance is inconspicuous. 



No living coral was seen except a small Favia sp. and an occa- 

 sional Gorgonid. 



While on the bottom I saw many fishes including both Kilati 

 (Trigger fishes) and Vellumin together with a beautifully stripped 

 sponge-eating fish {Holocanthus imperator). The Asterid, Pentaceros 

 fi/icki, was not abundant. No Suran {Modiola barbata) was seen. 



After I had completed my examination of the bottom, Captain 

 Carlyon being of opinion that it was now too late in the season to 

 do further work, and as the coal supply was on the point of giving 

 out, under the circumstances I determined to bring the investi- 

 gation to a close. 



When the anchor was brought up we had a repetition of our 

 former experience on this bank — the chain being studded with 

 young oysters of about two months old affixed by their byssal 

 cables near the attachment to the anchor. 



Two hours later we landed for the last time at Tuticorin and 

 although I had not been able to examine every bank charted, I 

 considered that I now knew the general characteristics of the 

 principal groups sufficiently well to answer all practical purposes 

 and enable me to furnish solutions to the majority of the problems 

 I had set out to solve. 



VII- COMPARISON OF THE CHARACTERISTICS AND 



RELATIVE IMPORTANCE OF THE VARIOUS 



PEARL BANKS. 



In the present section an attempt is made to seize upon the 

 essentially characteristic features of the chief pars — historical, 



