2l8 BULLETIN OF THE BUREAU OF FISHERIES. 



on a long series of experiments on the feeding habits of these creatures, came to a very- 

 different conclusion. He found that they spend about 65 per cent of the time buried 

 in the sand. They may eat two oysters a day on two successive days, but this is inva- 

 riably followed by a long period of several days to months during which the animal 

 remains buried in the sand. The method of attack is to crawl on top of an oyster, 

 mussel, or clam and wait for the victim to open its valves; then, rotating its shell on 

 the axis of the columella to the proper position, to thrust its own shell between the 

 valves of the prey, introduce its proboscis, and with its radula tear out the flesh of 

 the victim. 



These observations are in harmony with those of the author who, during the 

 summer of 1917, kept an individual of each of the two species of Busycon in an aqua- 

 rium with several mussels. During a period of six weeks five mussels only were eaten, 

 three of them being consumed during the night. The method of attack, as observed, 

 was somewhat different from that described by Colton (1908), but the principle was 

 the same. On one occasion the author saw one of the conchs creep up to a mussel 

 which was lying on its side with the valves open. Moving very slowly it thrust the 

 edge of its foot between the valves and then inserted the edge of its shell in such a 

 manner as to pry the valves open so that the proboscis could be inserted. After feed- 

 ing on its victim for a few minutes the snail turned the mussel over onto its back and 

 forced the prolonged portion of its shell between the two valves, in which position it 

 held the bivalve until every particle of the flesh was eaten (fig. 205). 



llyanassa obsoleta is a gastropod often found on the mussel beds, especially where 

 they are located on protected muddy flats. The author has never seen anything to 

 indicate that it is an enemy of the mussel, but the observations of Belding (1910) 

 suggest that it belongs to the class of predatory mollusks.. He observed that these 

 snails are active enemies of the scallop, forcing themselves in between the open valves 

 of the unwary shellfish to form a wedge while other members of their species creep in 

 and feed on the victim. If this is true for the scallop, it undoubtedly holds for the 

 mussel also. 



FISHES. 



Fishes of various species depend upon the mussels for their food supply. Killifish, 

 cunners, scup, and tautog greedily strip them from wharf piles, seaweed, and from the 

 beds. The squeteague, flounders, and cod also eat them in great quantities. Vidal 

 (187 1) states that young eels are very destructive enemies. He says they dart in 

 between the open valves into the mantle cavity, where they gnaw the muscles free 

 from the shell, so that the valves can not remain closed, and then devour all the soft 

 parts of the shellfish. The fact that mussels constitute the best bait known next to 

 squid indicates how they rank as a food for fish. 



BIRDS. 



Birds, such as herring gulls, night herons, crows, and ducks, find this mollusk a 

 desirable morsel. At Menemsha Pond, Marthas Vineyard, Mass., the author has seen 

 herring gulls, Larus argentatus, apparently eating mussels. They would seize the shell- 

 fish, which were about 2%. inches in length, in their bills and shake them to break their 

 byssal threads which bind them together. When frightened the gulls would seize a 



