88 MADRAS FISHERIES BULLETIN [VOL. XVI, 



the branches alone were coloured pink, the crabs were uniformly 

 white except for two splashes of pale pink on the anterior edge 

 of the carapace. The large fan-shaped green alga with bulbous 

 base embedded in the sand was the only alga found. A single 

 specimen of Lingula sp. was one of the noteworthy acquisitions 

 made in this locality. 



The sand was fine, clean, and with no trace of the mud which is 

 a characteristic component and essential attribute of a prolific 

 chank bed. 



Hence we moved north to the Tolayiram Par, where we anchored 

 after verifying the locality by cross bearings and by some trial 

 dives, which indicated the presence of numerous young oysters. 



During the evening the crew caught a large number of trigger 

 fishes {Balistcs) and of strong-toothed fishes of the genus Lethrinus, 

 the latter being known as Vellamin,* among the Tamil fishers. 

 The stomach contents of the Balistcs were in this case free from 

 incriminatory evidence in respect to pearl oysters, due probably to 

 the fact that all the individuals were of a small size. In the case 

 of the Vellamin on the contrary the stomachs were crammed with 

 fragments of pearl oyster shells upon which these fishes appeared 

 to be feeding exclusively. As six of these, all of large size, were 

 caught within two hours, it is plain that these fish are now inflicting 

 enormous havoc upon the bed of oysters on this par. 



The next morning I donned the diving dress, and the water being 

 fairly clear I had an excellent opportunity of examining the bank. 



The depth where the descent was made is 9% fathoms. I found 

 the bottom very variable; in most places a covering of about an 

 inch and a half of sand lay upon flat-surfaced rock. Here and 

 there the rock protrudes or lies level with the general sandy surface. 

 These exposed patches are small in area, usually from 1% to 2 feet 

 in diameter. A limited amount of small cultch is present on the 

 surface to which the majority of the oysters adhered. The cultch 

 consists of short fragments of much worn branches of coral 

 ("challai"), quite small Nullipore balls (Lithothatnnion), the tests of 

 dead echinoids (chiefly of Clypcastcr humilis), fragments of calcrete 

 and such like. 



The oysters were fairly abundant, their numbers obviously cur- 

 tailed by the quantitative limitation of the cultch. They appeared 



* Lethrinus nebulosus and other species. 



