No. 6(1921) COMMON MOLLUSCS OF SOUTH INDIA 



133 



The next family, the WHELKS or Biiccinidae, conversely are 

 characteristically northern in their habitat, in regard to their most 

 typical genera. The only conspicuous Indian genus is Eburna 

 { = LatruNCHliis\ These are stout whelk-like shells, solid, smooth 

 and white, usually brightly spotted or blotched with red, obscured 

 during life by a thin dirty brownish periostracum ; the foot is 

 similarly spotted. A characteristic feature is the rectangular form 



Fig. 19. Elntrna spirata crawlinii; Dver sand. 



of the suture dividing the whorls. In the young an umbilicus is 

 present; with age the inner lip becomes thickened and eventually 

 spreads over the umbilical opening. The common Indian species 

 are Eburna spirata and E- zeylauica. 



The NASSAS {Nassidac) are all small and often tiny shells of 

 the outline of a chank, usually covered completely with many rows 

 of tiny tubercles ; the aperture is usually small, the outer lip thick- 

 ened and strong and often armed with peculiar and prominent 

 "teeth," as may also be the inner lip formed by a strong callus 

 deposited upon the end of the columella. The foot is long and broad 

 and the siphon elongated. The Nassas are in the main scavengers 

 living upon carrion; their sense of smell is extremely acute and 

 they may be trapped in numbers by laying down a dead crab or a 

 piece of decaying meat in shallows or rock pools and watching the 

 effect. If Nassas abound it is not long before they are seen trooping 

 from all sides, each with its siphon extended in front and waving 

 inquiringly from side to side, to locate the source of the odour they' 

 have smelled. They cluster round and over a dead mollusc or a 

 dead crab exactly as ants do over a dead insect they have found, 

 but instead of dragging it away to their nest the Nassas devour 



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