SEA SNAILS. 23 



there is no notch, or fold, in it. In the three upper figures 

 there is a notch, or fold, in the base of the aperture. 



FIG. 27. SHELL SHOWING LONG CANAL. 



This notch is called the canal, and in some species it is 

 very short, while in other species it is very long, as in Fig. 

 27. 



The mantle of the animal is prolonged in a fold which 

 occupies this canal, and is called the siphon. Through this 

 fold or siphon the water finds access to the gills. (Fig. 28 

 shows another species. The siphon is seen as a fold of the 

 mantle running into the canal of the shell.) 



23. A very common species, found in the greatest abun- 

 dance from Maine to Florida, on mud-flats, will give a good 



