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operculum ; then when the animal was withdrawn into the 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 Mitride 
have opercula, especially the smaller forms, and 7. teresic. 
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 larve. 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 Z. scalaris is commonly found in the 
apertures of gasteropods, and especially of 7. teresiw, and 
whether this shellfish is possessed of an operculum and whether 
it is carnivorous. 
MR. GEO. PATTISON, 
H ' 68 PARTRIDGE STREET, 
: GLENELG, 
SOUTH AUS: RELA 


