THE NAUTILUS. 67 



antly on the fiats. To get at the Nassa, they envelop the shell 

 in the foot until it is asphyxiated, and then clean out the 

 animal with the radula. In the second stage the quahaug and 

 oyster are the chief articles of food, and, contrary to the general 

 opinion, the radula is not used to bore through the shells, but 

 the edges of the valves are chipped away against the lip of the 

 Busy con's shell. 



I was led to take up these investigations by the following 

 facts : in examining radulae of the Busycons I noticed that 

 they were not so worn as in the borers Polinices and Urosalpinx ; 

 the lips of their shells are almost invariably chipped : and the 

 dead quahaug shells on the flats were not bored but chipped. 



Subsequently I found that Mr. Harold S. Colton had de- 

 scribed (Proc. Acad. Nat. Sci., Phila ; 1908) the feeding of B. 

 cannliadata as observed in the aquarium of the University of 

 Pennsylvania. The following statements are quoted from his 

 summary. 



" They (canaliculata and carica) open the shells of oysters by 

 wedging their own shell between the valves and tear out the 

 jBesh with their radula. They probably treat quahaugs in the 

 same way. 



"Sycotypus will attack any except Venus." 



He also states that the whelk waits until the bivalve opens 

 and then inserts its shells between the valves. 



Mr. C. W. Johnson suggested to me that the bivalves might 

 have been weakened by life in the aquarium, and this is pro- 

 bably the explanation of the shells' opening their valves while 

 gripped in the Busycon's foot. Also Avhile B. canaliculata will 

 not attack quahaugs as early in life as B. carica, since the lip 

 of its shell remains almost paper-like until the animal is well 

 grown, I found two large specimens eating quahaugs. 



The Busycons I observed ate in the following manner. An 

 oyster is held in the foot with the hinge toward the canal, while 

 a quahaug is grasped in such a way that the hinge is toward 

 the columella, but in both cases the edges of the bivalve are 

 left free. In the majority of cases the Busycon rests on its foot 

 with the canal pointing upwards at an angle of about 30°. The 

 foot is slowly contracted, about six times a minute, and the 



