1895. NOTES AND COMMENTS. 301 



Curiosities of Mollusca. 



We hope to give a detailed review of the " Cambridge Natural 

 History " in our next issue ; but there are so many interesting tit-bits 

 of information in the volume which has just appeared that we feei 

 justified in anticipating a little. Everybody had heard of the use of 

 the cowry shell as money. But, possibly, the extent to which this is 

 legal tender is not so well-known. Mr. Cooke relates how a gentle- 

 man in India paid for a house, which he had erected, entirely in these 

 shells. The house cost him ^400 ; the equivalent of this sum in 

 shells was 16,000,000, which were paid as such. Not only is this 

 particular shell used as specie ; in other parts of the world other shells 

 are put to the same use. The wampum of the American-Indian is 

 simply an elaborate ornament formed of shells of the common clam, 

 Venus mevcenavia ; an Indian, therefore, like a Belgian maiden with 

 her gold ornaments, carried his fortune upon his person. 



But shells have a value also among civilised races. They are 

 apt to be dear to the collector ; and rare species have fetched large 

 prices. Mr. Cooke has brought together some excerpts from 

 auctioneers' catalogues, from which it appears that ^"ioo is the record 

 price asked for a shell. The specimen which was supposed to have 

 this extraordinary value is one of Pleurotomavia adansoniana ; but it has- 

 been sold to the British Museum for about half that sum. 



Mr. Cooke has brought together some interesting cases of 

 supposed mimicry among the Mollusca, of which the following is 

 perhaps the most striking. "Certain species of Stvombus (mauritiamts r 

 L., luhuanus, L.) show a remarkable similarity in the shape of the 

 shell to that of Conns, so much so, that a tyro would be sure to 

 mistake them, at first sight, for Cones. In the case of S. luhuanus at 

 least, this similarity is increased by the possession of a remarkably 

 stout brown epidermis. Now Conns is a flesh-eating genus, armed 

 with very powerful teeth which are capable of inflicting even on 

 man a poisonous and sometimes fatal wound. Stvombus, on the 

 other hand, is probably frugivorous (sic), and is furnished with weak 

 and inoffensive teeth. It is possible that this resemblance is a case 

 of ' mimicry.' It is quite conceivable that powerful fishes which 

 would swallow a Stvombus whole and not suffer for it, might acquire 

 a distaste for a Cone which was capable of lacerating their insides 

 after being swallowed. And, therefore, the more like a Cone the 

 Stvombus became, the better chance it would have of being passed 

 over as an ineligible article of food." 



" Protective coloration " is not unknown among molluscs. The 

 Scyllcca of the gulf- weed, with its olive-brown hues mixed with white 

 spots, is one of the most familiar instances. Mr. Cooke draws 

 attention to the fact that the " Blue Limpet," Helcion pellucidum, 

 which, when young, has beautiful iridescent tints, lives at that period 

 of its life exclusively upon the fronds of the great Laminaria, which 

 has also iridescent hues. Later in life, when the iridescence fades,. 



