KEY 



FOR THE 



Analysis of Shells 



MARINE UNIVALVES. 



CHAPTER. 



Shell somewhat fusiform, with a distinct canal and an 



unpolished surface II — V 



With short canal and polished surface VI 



With opposite varices and canals . VI 



Without canal, rounded, white, spire short VII 



Shell consisting chiefly of a slender spire VII, VIII 



Shell an inverted cone VIII 



Aperture as long as the shell IX 



Shell spiral, very minute X 



Shell short and full, found on upper rocks X 



Shell horn-shaped, dark XI 



Shell tubular and contorted XI 



Shell slipper-shaped XI 



Shell top-shaped or turban-shaped, aperture entire, pearly 



within XII 



Shell large and flattened, with holes in the side XIII 



Shell volcano-shaped XIII 



Shell like an inverted cup or saucer XIV 



Shell small, with ear-shaped aperture XVII 



Shell thin and bubble-shaped XVII 



FRESH-WATER UNIVALVES. 



Shell wheel-shaped XVI 



Shell rounded, with short spire IX, XVI 



With long spire X, XVII 



Sinistral shells XVI 



Shells minute, limpet-shaped XVI 



221 



