CHAPTER XVI. 



The Tooth Shell— Indian Money — The Violet Snail — 

 Siphonaria — Fresh-Water Limpets — Carnifex New- 

 berryi — The Helisomas — The Physas oe the Brooks 

 — Sinistral Shells in Variety. 



A STRANGE little shell is that shown in Fig. 101, 

 and a fairy tale could it tell of the life of its 

 little inhabitant. Shaped like the tusk of an ele- 

 phant, pure white, slightly curved, and open 

 at both ends, it differs widely from all the 

 shells which we have so far considered. 



The name of this little creature is Denta- 



lium pretiosam, Nutt, Den-ta'-li-um pre-shi- 



o'-sum, and it is found chiefly in the vicinity 



Fig. 101. f p U get Sound. The species has also been 



named Indicniomim, Cpr. ; we will call it the Precious 



Tooth-shell. 



The mollusk is not so highly organized as some of 

 its neighbors, and it spends its life in the sand. The 

 large end of the shell opens downward, and from its 

 aperture projects the foot, with which it is able to dig. 

 From the small end which projects above the sand, it 

 can throw out little tenacles, which ensnare the infu- 

 soria and other minute animals upon which it feeds. 

 In olden times the Indians used these shells as 

 money, stringing them upon long threads, and they 

 were highly prized. This fact explains both the 



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