I IOKNELL MARINE KESOKHCKS 5 



economic value from the active aggression of predatory enemies and from the |m.-.-iv<- 

 competition of creatures of similar habitat or dietary. 



As a result of the information obtained by dredging, diving, and shore-collecting 

 during the five weeks of the investigation, it appears that the seaward or western 

 coast of Okhamandal may be eliminated from further consideration. Its aspect, 

 fronting the terrific onset of the south-west monsoon surf, renders it too exposed to 

 permit of exploitation from May to September, save for a paltry number of chanks 

 that may be picked up in the shallows at low tides. The turmoil of the breakers 

 is too great to permit of existence on the littoral and down to a depth of twelve 

 to fifteen fathoms save to such quickly growing animals and plants as can spring 

 into luxuriance in the comparatively quiet interlude afforded by the north-east monsoon 

 season, or to such others as have so modified their structure and habits as to be 

 able to withstand the battering of the surf and the wrench of a violent undertow. 



Not a trace of pearl oysters, living or dead, was found ; not even the smallest 

 fragment of a valve. From this and the physical circumstances of the locality I 

 am satisfied that no deposit or bed of pearl oysters has existed here since the 

 configuration of the adjacent coast assumed its present aspect. Even if they did 

 exist, it would in practice be impossible to fish them, either by means of the dredge 

 or by the help of naked divers, the former because of the rough nature of the 

 bottom great surf-worn boulders in many places, the latter because in the season 

 available, winter, chill winds prevail with too low a temperature. 



By means of the dredge and occasional diving descents we also went over all 

 the likely localities in the deeper off-shore waters, notably the great bank named 

 Gurrur 011 the Admiralty Chart. This extensive bank which lies five to six miles 

 west of Okha Point, measures ten miles in length by one and a quarter miles in 

 breadth, with depths of from six to ten fathoms over it; it slopes rapidly into deeper 

 water on the landward side as well as on the seaward or western aspect. Judging by 

 the analogy of the similarity in depth, in distance from the mainland, and in apparent 

 configuration with some of the large pearl banks in the Gulf of Mannar, I had some 

 hope of finding here likely biological conditions for pearl oysters. Such hopes were 

 disappointed ; the bank proved to be an irregular plateau a flat-topped rocky reef 

 covered more or less thickly with rolled and water-worn fragments of shells and 

 small pieces of dead coral. There appeared to be an almost complete dearth of life. 

 The bank is barren and washed by continual currents that keep the bottom in ;i 

 constant flux and reflux. The day devoted to its examination (December J-Jnd) \\;is 

 comparatively fine, and even then the launch drifted at quite four knots an hour, 

 while the divers reported such a strong bottom-current as to render it almost 

 impossible to keep a position on the bottom for even a few seconds. With a light 

 north-east wind and calm sea the water on the bank was distinctly muddy and in 

 contrast to the brighter water beyond its margin, so that even without resort to 



