A COMMON SPECIES. 85 



resist the buffeting of the waves, it clings to the 

 rocks which are daily left bare by the retreating 

 tides. Immense numbers of these little creatures lie 

 at the base of the cliffs; in some cases I have seen the 

 rocks almost black with them, of all ages and sizes. 



On my first visit to the seaside, I wanted them all, 

 and I gathered and cleaned them for hours. Two 

 very natural results followed; first, that there remained 

 apparently as many as before; and second, that on 

 subsequent visits I gathered very few. But whether 

 we collect them, or merely watch their movements 

 and study their habits, still they soon become like old 

 friends to anyone who has learned the pleasant art of 

 putting himself in sympathy with the lower animals. 



When in the water, the little black animal with its 

 short head and lively feelers may be seen briskly 

 moving about; but when out of water he evidently 

 feels that the inside of his shell is the safest spot for 

 him to rest, and into it he withdraws, and closes the 

 doorway with his circular operculum. 



The color of the shell is dark purple, almost black 

 on the outside, with greenish white pearly layers 

 beneath. The whorls are four in number, and the 

 uppermost ones are often eroded, so that the shell 

 appears more flattened than is shown by the engrav- 

 ing. The body- whorl is puckered near the suture; 

 the umbilicus is nearly closed, and the columella is 

 set with two little white knobs, near its base. The 

 common length of the shell is less than an inch, but 

 sometimes specimens are found which are considera- 

 bly longer. 



Ethalia supravalata, Cpr. , and its variety, inval- 

 lata, Cpr., are exceedingly minute creatures, having 

 flattened, spiral shells, about the size of a pin's head. 



