HORNELL THE INDIAN CONCH 5 



The central type has a heavy massive shell, with a well-proportioned and well- 

 defined apical spiral. Apart from the chestnut coloured surface-markings which are 

 extremely variable and tend to disappear with age, these shells are of an opalescent 

 lily-white colour, porcellaneous in texture and slightly translucent when cut into sections. 

 Unlike var. obtusa the colour of the body at the mouth is not deeply tinted ; usually it 

 is of a very pale flesh tint or even quite white, whence comes the Tamil name Vel-vayan 

 or " white-mouth " used to designate this variety, which again is split into several 

 local races whereof the principal are known locally as (1) big-bellied chanks and (2) 

 small-bellied chanks. The former come from the beds lying off the mouth of the Tam- 

 braparni River, the other chiefly from the northern beds off Tuticorin. 



A second location of the central type is found on the coast of Kathiawar, separated 

 from the Gulf of Mannar and Ceylon area by hundreds of miles of sea bottom from which 

 all forms of Turbinella pyrum are absent. 



(b). Turbinella pyrum, variety obtusa, is very distinctive in shape and sometimes in 

 colouration. The apical spire is emphatically abbreviated, the whorls appearing as 

 though telescoped while the colouring of the body at the mouth opening is frequently of 

 a dark brick-red in shells from the Tan j ore coast, most distinctive when compared with 

 the delicate pallor of this region in shells of the central type. 



The distribution of the obtusa variety includes the littoral waters of the eastern 

 coast line of the Madras Presidency from Pamban Pass in Palk Bay to the delta of the 

 Godaveri River in the north ; the chief fishing grounds are situated in Palk Bay and off 

 the Tanjore coast, where this variety furnishes annually about 200,000 shells to the 

 Calcutta market. 



The shortening of the apical whorls often becomes extreme and so abbreviated 

 as to be subtruncate and to approach in general form the aboral appearance of a 

 typical Conus. This extreme form appears to arise when the environment is highly 

 unfavourable, such as life in a muddy sea co-ordinated with scarcity of food ; it re- 

 presents an extreme form of stunting, analogous to that seen on those pearl banks where 

 dense over-population reduces the available food supply to a degree insufficient to meet 

 the normal individual requirements. 



(c). Variety elongata is a much elongated spindle-shaped form found in the Andaman 

 Islands. As var. obtusa is the extreme in variation in the coniform direction so elongata 

 approaches to the long-drawn-out spiral of Fusus. (PI. II., fig. 4). Shells of this variety 

 are very rare on the coast of the Indian mainland but I cannot accept it as anything 

 more than a very well-marked variety of Turbinella pyrum. 



The anatomy of the body of Turbinella. pyrum follows closely the lines of such a 

 typical gastropod as Buccinum (Whelk), and it is unnecessary to go into any details 

 here, save to mention that the sexes are separate, the proboscis much elongated, and the 

 columellar muscles extremely powerful. It is well nigh an impossibility to extract 

 the animal intact from its shell even after death ; the ordinary methods which are read'ly 



