THE NAUTILUS. 45 



times tne channel bottom is purple with the migrating snails. 

 Each one will be seen to be poking his siphon out an inch 

 ahead of him testing the water to the right and to the left and 

 always moving along with a characteristic persistency. He only 

 stops where the current has swept everything else away and 

 then only until the tide favors him again. I have seen, him 

 crawling along where the crabs were hanging on to the sea weeds 

 for dear life, and even while stopped for a while one sees him 

 still testing the water ahead of him. He eats his lunch on the 

 march, troubles himself not at all about his shelter for the night 

 but ploughs his way along even though the water in his path 

 be fresh, opaque with sediment or a briny salt pool. It matters 

 nothing to him : over the obstacles in his path he crawls, reaches 

 the channel bank and then seeks out a new environment in the 

 water below or if it be in spring on the mud flats above. 



One more interesting habit of Ilyanassa and we shall be done 

 with him. He is not always submarine in his habits. While 

 traveling over the surface he must have water running over him. 

 He stops wherever the tide uncovers him. When the tide 

 comes in again it may find him perched on a rock. This ap- 

 proach of the water may loosen his hold and he may tip back- 

 ward curling in his foot as he tumbles. Many times he simply 

 rolls over and is submerged ; but as often the current catches 

 him and bears him along upside down with his inturned foot 

 preserving the buoyancy of the mass. I have seen dozens float- 

 ing along in just this manner, but whether it is an accident or 

 purposeful activity, I have been unable to find out. Sometimes 

 he steals a ride on the back of his neighbor, or on a floating 

 weed or stick and quite often on the shell of L. litorea. 



Litorina litorea migrates with Ilyanassa but is far less active. 

 They move very slowly, rest frequently and often explore the 

 rocks and ledges that line the channel. They follow Ilyanassa 

 down stream in the fall part way, winter with them in the 

 shallower, ice-free basins and return with them in the spring. 

 During the winter L. litorea may be found clinging fast to the 

 rocks in the channel bed or may go no farther than the lowest 

 of the shore bowlders where they hibernate with L. rudis under 

 the Fucus hovers. They migrate at most 25 or 30 feet. 



