I60 MADRAS FISHERIES BULLETIN VOL. XIV, 



in the alimentary canals of these birds that the flatworm larvae 

 found in the adult mussels are derived. Under certain circum- 

 stances occasional larvse induce the formation of pearls in the 

 mantle of the mussel, the dead body of the parasite persisting 

 as the nucleus of the pearl. The life-history of the Sonapur 

 pearl-inducing parasite has yet to be worked out. 



The Brown Mussel {Mytilns sp.) is the largest and stoutest species 

 found in South India, attaining commonly a length of 4 inches. 

 It is distinctly larger than the Green Mussel, but unlike the latter 

 its distribution is limited to a comparatively short length of coast 

 in South Travancore, where it displaces the green species. The 

 coast here is exposed to exceptionally heavy seas during the mon- 

 soon, but in spite of this it thrives in great abundance on rocks 

 from low-tide level to a depth of about 2^ or 3 fathoms. Annually 

 large quantities are taken from the rocks by divers. They fcrm an 

 important food item among fishermen and coast Muhammadans. 



Several medium-sized species of the WEAVING MUSSELS {Modiola 

 spp.) exist in our seas ; in Palk Bay and the pearl bank region in the 

 Gulf of Mannar one species, the Bearded Weaving Mussel {Modiola 

 harbata; suran, Tamil) is so abundant that I have seen several square 

 miles of sea bottom covered continuously with a carpet of these 

 shells, felted together in a tangle of byssal threads. The presence 

 of suran in such myriads is one of the adverse influences militating 

 against the prosperity of our pearl banks; the rapidity of their 

 growth and their habit of enveloping everything about them in a 

 dense network of felting fibres, contributes largely to the destruc- 

 tion of the more delicate pearl-oyster spat. The two molluscs have 

 identical feeding habits and the competition of hungry myriads of 

 suran has the same blighting effect on pearl oysters as that of 

 the American slipper limpet upon the edible-oyster on the East 

 Coast of England. The larger species, the Tulip Mussel {Modiola 

 tulipa), is common in Palk Bay where it forms extensive beds. The 

 average size is not too small for food purposes, and were there any 

 demand, tons of them could easily be dredged in Palk Ray. The 

 larger species is excellent eating, while the smaller would make, if 

 dried and pulverized, poultry meal and fertilizer. A very small 

 species, Modiola variabilis, characterized by the fine ribbing of the 

 shell, lives associated with the edible oyster in backwaters, 



