32 Dwellers of the Sea and Shore 



from natural enemies or other accidents. These ene- 

 mies are sometimes large, sometimes small; they may 

 be microscopic. Surprising as it may appear, after 

 long resistance to the former, many animals reach a 

 ripe old age only to succumb to the insidious attacks of 

 the latter. Of course, the weaknesses due to old age 

 make them especially liable to the invasions of these 

 invisible hordes; nevertheless, sooner or later, the great 

 majority of marine animals meet a premature death. 

 Thus it has been with the occupants of the shells on 



HOLE DRILLED IN THE SHELL OF A MUSSEL BY A MOON SNAIL. 



the beach. In the case of the many, both the bivalves 

 and the univalves show one unmistakable clue to the 

 identity of the assassin who dispatched them. This is 

 a small round perforation in the shell through which a 

 wheat straw can be passed. It is the mark of the moon 

 snail or one of its carnivorous brethren. 



The moon snail {Lunatia heros) is easily the largest 

 shell-bearing mollusk in these waters. When full grown 

 its rounded, w^hitish, spirally coiled shell is about four 

 inches long. But like the familiar pond snail, the ani- 

 mal crawls on a large fleshy foot. This foot with its 



