No. 6 (192T) COMMON MOLLUSCS OF SOUTH INDIA IO3 



people are accustomed to collect them for food. They are known 

 there as Uiiai in Tamil. 



The common Indian species are Patella variabilis and P. rudis. 



The Keyhole Limpets and the Slit Limpets {FissurdUdae) in 

 the shape of their shell resemble closely the true limpets, but have 

 either a perforation at the apex or a tiny slit in the front margin 

 of the shell. The use of these apertures is to ensure the removal 

 of foul matter. Pure water is admitted to the gills through the 

 space between the edge of the shell and the rock surface beneath 

 and then is passed out by a tubular fold of the mantle through the 

 hole at the apex or the notch in the front edge, washing out at the 

 same time any excreta that require removal. The Indian species 

 are all small and consist of a few species of the keyhole limpet 

 {Fissiirella) and of the still rarer and smaller Emargimda, one of the 

 split limpets. These live below low tide line and are not found 

 except by dredging. Dead and worn shells are occasionally cast 

 up on the Ramnad and Tinnevelly coast. 



Closely allied to the preceding are the Ear-SHELLS or Haliotidae. 

 A common species is Haliotis varia, found living under boulders 

 at extreme low tide at Pamban and Krusadai Island and the 

 other coral reefs that skirt the south-east coast. This species 

 is quite a small one, seldom exceeding 1% inch in length — a poor 

 representative of the family. In other lands, in France, Japan, 

 New Zealand and California, the ear-shells attain a length of 4 to 

 6 inches, and vie with the rainbow in the gorgeous colouration of 

 the mother-of-pearl lining of the shell. As a consequence it is 

 extensively used for pearl inlay work. Pearls are not uncommon 

 in the mantle, but their value is not great as coloured pearls are 

 little in demand. Wherever it is found, the ear-shell is highly 

 valued as food, its great muscular foot being a delicious morsel 

 when properly prepared and cooked. The Chinese especially 

 value it and great quantities are prepared in Japan and California 

 for export to China. It may either be cured dry or put up in tins— 

 the abalonc of Californian markets. In shape it is a flattened 

 limpet with a row of holes piercing the shell along the left margin. 

 The function of these holes is more specialized than in the keyhole 

 limpet, for here it is only the most posterior one which is used as 

 an anal funnel to get rid of impure water and debris, whereas the 

 others, of which there are several, are used apparently to admit 

 water to the gills. 



