449 



with it. The most likely point of attachment would be an 

 operculum ; then when the animal was withdrawn into the 

 shell it would draw the bivalve within the aperture, and when 

 the animal extruded itself and crawled about on the ventral 

 surface of its foot, the bivalve could ride in safety fixed to the 

 operculum on the dorsum of the foot. Some of the Mitridse 

 have opercula, especially the smaller forms, and T. teresice 

 may ; but though I tried to determine this point, I could not 

 find the operculum in two of the examples examined, but they 

 had been largely destroyed by carnivorous larvae. This note 

 is published to direct attention to the bare possibility of 

 commensal association between a bivalve and a gasteropod, 

 and to suggest investigation by any who can get fresh material 

 as to whether the L. scalaris is commonly found in the 

 -apertures of gasteropods, and especially of T. teresicB, and 

 whether this shellfish is possessed of an operculum and whether 

 it is carnivorous. 



Jos. C. Verco. 



