I32 MADRAS FISHERIES BULLETIN VOL. XIV^ 



is beset with wide rounded ridges. Fiisus antiqitus is an extremely 

 abundant species in Western Europe; apart from its considerable 

 economic value as food, a point of great interest is that a separate 

 race or variety arose in Pliocene times distinguished for its reversed 

 or sinistral twist. In the chank, this abnormal form is extremely 

 rare, but even here the bulk of them occur in one particular locality, 

 indicating that there is in that place a family (in the popular 

 sense) distinguished by this peculiarity, just as there are occasion- 

 ally families among men distinguished by six fingers in place of 

 five on each hand. In Pliocene days such a family evidently 

 competed successfully with their normally shaped relatives and 

 formed a race that became dominant ; to-day this sinistral form still 

 exists in the Mediterranean and on the coast of Spain, but on the 

 British coasts the normal (dextral) form has ousted completely the 

 abnormal sinistral variety. 



Fig. iS. Egg cases of a, large Gastropod, probahly a .Murcx, 

 common off Tuticorin. 



The Mitre-shells {Mitridac) are handsome, brightly 

 coloured shells, much sought after by collectors. Unfortunately 

 the finer species are rare in Indian waters ; the BISHOP'S MiTRE 

 {Mitra episcopalis) found in the Gulf of Mannar, is particularly 

 beautiful, its shape elongated into a stout spindle and the surface 

 decorated with spiral rows of blotches and spots. The mouth is 

 rather narrow and like that of the chank is distinguished by the 

 presence of several pleats or folds on the columella. The mitres are 

 almost exclusively confined to the warm regions of the earth, from 

 the Mediterranean, where they are small and few, to the East 

 Indies and thence to Panama. They are most abundant and diverse 

 in the Philippine region. 



