The Tooth Shells 



vulgare. The longitudinal striae are wanting almost entirely, 

 and distinct segmentation of the shell is often made by the lines 

 of growth. The anterior margin is jagged, the posterior aperture 

 is oblique and notched on the convex side. This is the familiar 

 tooth shell of the New England coast and of the British Isles. 



The Elephant-tusk Shell (D. elephantinum, Linn.) is 

 well named. It is curved and tapers like the tusk of an ele- 

 phant, is strong, and has the texture of ivory. Ten strong 

 longitudinal ribs give it a corrugated surface. The usual colour 

 is dark green, fading to white at the apex. Transversely the 

 ridges are crossed occasionally by bands that limit the annual 

 growth of the shell. These strikingly handsome tusk shells 

 come from the Orient, notably from the Philippine Islands. They 

 are sometimes three inches in length. 



D. aprinum, Linn., is a pea-green, glossy tooth shell 

 of a slender, gracefully curving form, but strongly built. 

 The 9 to 12 ridges are not so prominent as in the two preceding 

 species; they are separated by wide, flat and highly polished 

 intervals. These measure up to 2f inches in length. Diameter of 

 aperture, \ inch. They come from the Philippine Archipelago. 



The Japanese angled tusk shells resemble these in form, 

 but they are white. They are of closely related species. 



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