6 PROCEEDINGS OF THE ACADEMY OF [Jan., 



both F. perversa and F. carica do injure the shell of Venus mercenaria 

 (Quahog); and, although they leave marks on the shell of Mytilus 

 (mussel) and perhaps Ostrea, the shell of Mya (soft shell clam) is left 

 without a scratch. 



In the case of Sycotypus eating oysters, I have been able to watch 

 the whole process from the beginning to the end without interruption, 

 so I will take this as my first example. It will be an account of the 

 behavior of a single individual. 



The Sycotypus had not been fed for a month or so and was buried in 

 the gravel. To stimulate, I added some very finely chopped-up oyster 

 to the aquarium. When it started to crawl out of the gravel, a few 

 minutes after I added the oyster juice, I placed some live oysters in the 

 aquarium with it. It attacked one of the oysters five minutes after I 

 placed them with it. Fifty minutes afterward it left the empty shell. 

 Going a foot to another oyster, it began to attack it twenty minutes 

 after it left the first one. 



The Sycotypus crawled on top of the oyster, which closed its valves. 

 The conch waited two minutes when the oyster opened its valves 

 (Plate II, fig. 7). Rotating its shell on the axis of the columella 

 through an angle of 70°, it thrust its own shell between the valves of 

 the oyster and introduced its proboscis between the shells (Plate II, 

 fig. 8). Forty minutes later it left the empty shell. 



Sycotypus does not wedge the shells of Mya apart, because it can get 

 at the soft parts without doing so, since the valves gap slightly (Plates 

 II and III, figs. 11, 12). To test this I introduced an oyster that 

 had had three-quarters of an inch broken from the margins of both 

 valves on the end away from the hinge so that the valves appeared to 

 gap. I found that Sycotypus attacked this one in the same manner 

 as it attacked Mya and did not wedge the .shells apart (Plate I, fig. 6). 



Fulgur eating Venus is a much more complicated case. The conch 

 {Fulgur perversa or F. carica) grasps the Venus in the hollow of its 

 foot (Plate IV, fig. 13), bringing the margin of the Veiius shell against 

 its own shell margin. B}^ contracting the columellar muscle it forces 

 the margins of the shells together, which results in a small fragment 

 being chipped from the shell of Venus. This is repeated many times 

 and, finally, the crack between the valves is enlarged to a width of 

 3 mm. or more (text fig.). 



The proboscis is normally about 5 mm. to 8 mm. in diameter 

 There are three ways in which it may get at the animal. First, it may 

 flatten out its proboscis so that it will go through the crack; secondly, 

 it may pour in a secretion between the valves which kills the clam. 



