278 MOLLUSCA AND MOLLUSCOIDA 



Twenty- two per cent, of the Indian deep-sea 

 Gastropods belong to the genus Pleurotoma, a genus 

 which is also prolifically represented in the shallow 

 waters of these warm latitudes. Among them is 

 Pleurotoma symbiotes (Fig. 14), first found off Cape 

 Comorin at a depth of over 1000 fathoms, which 

 has already been mentioned as invariably having its 

 shell encrusted with a commensal zoophyte of the 

 genus Epizoanthtts, Turbo indicus, which lives near 

 the 600-fathom line in the same neighbourhood, is an- 

 other hospitable species which gives a lodging on its 

 living shell to a sponge and a barnacle {Scalpellum). 

 This Turbo is of further interest, because, according 

 to Mr E. A. Smith, it is possibly only a variety of 

 Turbo peloritamts, a deep-water species of the Medi- 

 terranean and North Atlantic. 



One of the commonest and most characteristic 

 Gastropods of the edge of the abyssal slope in the 

 Bay of Bengal, is Rostellaria delicatula, Nevill (Fig. 

 70), a small and delicate, but very handsome species. 

 It furnishes a good illustration of the fact that deep- 

 water species as a rule have much thinner and lighter 

 shells than their kindred of the shore. 



A Gastropod which is found in the Andaman Sea 

 at almost every haul between 100 and 300 fathoms, is 

 the Japanese Xenophora pallidula (Fig. 71): this 

 creature also has naturally a thin and translucent 

 shell, which, however, it fortifies by building into it a 



