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MADRAS FISHERIES BULLETIN 



VOL. XlV, 



The Zebra Wing-shells (A. zebra) are still more adept at 

 mimicry; they live chiefly upon a tall handsome zoophyte {Hali- 

 cornaria insignis). The host has stoutly built pinnate branches of 

 a deep brown colour. Upon these the little zebra wing-shells often 

 congregate in numbers, their shells striped brown and white 



Fig. 40. Avicttla radiata commensal upon a Sea-fan. (Gulf of Mannar.) 



X \. 



exactly simulating the brown pinnules and the colourless spaces 

 between — precisely the same idea is exploited as is seen in the 

 colouration of the tiger and the zebra ; against their usual back- 

 ground, they are indistinguishable at a distance. 



The smallest of our wing-shells is Avicula vexillum, known in 

 old pearl-oyster reports as ' false spat,' as it has been mistaken 

 times out of number for the spat of pearl oysters, thereby raising 

 unfounded hopes of great pearl-fisheries in the immediate future. 

 It is a tiny shell, seldom more than one-third of an inch long. It 



