No. 6 (I921) COMMON MOLLUSCS OF SOUTH INDL\ I05 



foot in many gastropods. When the animal retires into its shell, 

 when alarmed or attacked, the operculum serves as a door to close 

 the opening and to keep the intruder out. In the Top-shells it is 

 horny and marked with a closely set spiral ; in the Turban shells, 

 it is stony and very massive, and there are species so large that 

 the operculum is heavy enough to be used as a paper weight— two 

 inches in diameter. The operculum of one species found in New 

 Zealand, very brightly mottled with green and brown, is highly 

 valued by the Maoris as a personal ornament set in gold; they 

 also used it to form the eyes of their idols in former times. Even 

 in India the operculum of Turbo has value. It finds its place, with 

 all sorts of local shells and marine curiosities, in numerous booths 

 within the main entrance to Rameswaram temple, for sale to the 

 pilgrims and devotees who flock there in thousands from all parts 

 of India. The best ones are retailed at 8 annas per hundred, sea 

 worn ones at considerably less. The Valayan women who collect 

 shells on the Pamban reefs get about 8 annas per measure for these 

 opercula and 2 annas for the same quantity of any Top-shells they 

 can collect — another object of sale to pilgrims. The Tamil name 

 for Turbo opercula is ambiliiiian, meaning "the disc of the moon." 

 The flesh of Turbo {nathai, Tamil) is eaten by the island people 

 (Valayans) but that of Trochus {tbalappaikatti, Tamil) is not 

 esteemed owing to its small size and the difficulty of extracting the 

 body from the coils of the shell. 



All our species of Turbo and Trochus are small except in the 

 Laccadive Islands where a commercial " Trocas " {Trochus pyramis) 

 is sometimes found and some fairly large Turbos T. {argyrostoma). 

 Sometimes on overturning a large boulder among the scrub near the 

 beach in one of these islands, a score or more of big Hermit-crabs 

 have scurried away in all directions, the majority hiding their soft 

 tail in a big Turbo shell. 



A rather pretty Top-shell {Clanculus clanguloides) is not uncom- 

 mon in the Pamban neighbourhood. Like the other Top-shells, the 

 sides of the body are fringed and provided with a number of long 

 and slender tentacle-like filaments. 



Most common of all the Trochidae is the beautifully variegated 



and polished shell of Uiiibonium {Rotclla) vestidrium, a little species 



that occurs at the mouths of some of the East Coast backwaters in 



enormous numbers. It is one of the most dainty little shells I know. 



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