202 WEST COAST SHELLS 



the aperture is nearly circular in shape, and it is 

 closed with a thin, horny operculum. As you find 

 them perched upon the rocks, quietly resting till the 

 time of the next high tide, you will note that a little 

 part of the "foot" of the animal must be outside the 

 shell, to enable him to cling securely to the rock. 

 But the portion is very small, and just how the crea- 

 ture fixes himself so that he will not roll off and at 

 the same time not dry up is something to be in- 

 vestigated. 



If you brush them off, however, the whole foot is 

 immediately retracted, and the aperture is securely 

 closed with the operculum. If you then put them in 

 a bowl of sea-water or drop them into a tide- 

 pool the little black animal quickly emerges from 

 the shell and begins to rapidly creep along the 

 smooth surface towards the upper air. Some of them 

 will live a long time out of water, and can safely be 

 sent from one port to another. 



The food of these little animals is vegetable mat- 

 ter, especially the minute plants that form the thin 

 green coatings upon the stones. This is scraped off 

 by means of the little hooked teeth which grow upon 

 the tongue, or ribbon, with which the mouth of most 

 mollusks is provided. In respect to their food they 

 present quite a contrast to the purples, nassas and 

 other mollusks having siphons, that we have been 

 considering. Those creatures are flesh-eaters, and 

 they often use their sharp teeth as instruments to 

 enable them to break into other mollusks' houses. 

 And so we have a kindly feeling for the littorines 



