i8o 



MADRAS FISHERIES BULLETIN 



VOL. XIV, 



This species, although its shell is usually too thin to be of any 

 use in pearl-button manufacture, sometimes produces pearls in 

 considerable quantity of fair value. Occasionally they are offered 

 in the Surada Bazaar (Ganjam) ; these are obtained from a great 

 irrigation reservoir in the neighbourhood wherein these mussels 

 flourish, growing to a length of about three inches. The pearls 

 have a reddish tint and less lustre than those from the marine 

 pearl oyster. Another species in Bengal is extensively employed 

 in making buttons. An allied genus, Parrcysia, has coarser 

 hinge-teeth and generally a stouter shell. 



The species of TelliNA [TcUinidac) most common on all our 

 sandy shores is small and pink-shelled, about M of an inch long, 

 compressed from side to side. The fore end of each valve is 

 rounded, the hinder end shorter and slightly angular; the ligament 

 is external, showing as a prominent black hinge behind the beak or 

 umbo. The markings on the inside of the valves are distinctive ; 

 the pallial sinus, which marks the position of the " siphons " when 

 withdrawn into the shell, is extremely deep, extending from the 

 hinder margin nearly to the anterior adductor. Without seeing 



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Flc. 46. A Masking Crab {Dorifpe dorsifcs) carrying a Tellina shell on which 

 is an anemone, for the purpose of concealment and defence. 



the live animal a zoologist can tell from this that the Tellinas 

 have long siphons. These in fact exceed twice the length of the 

 shell ; they are formed by the tubular outgrowth of the mantle 

 edge at the posterior end of the body ; the evolution of the 

 siphonal tubes in bivalves is particularly interesting, for among 



