Observations on the bivalvesMontacuta substriataandM. ferruginosa, ‘commensals’ with spatangoids

Field and laboratory observations were made of the erycinacean bivalvesMontacuta substriataandM. ferruginosa, which are usually considered as ‘commensals’, respectively, with the burrowing spatangoidsSpatangus purpureusandEchinocardium cordatum. These species were obtained mainly from the Plymouth area, whereM. substriatawas also found withE. flavescensandE. pennatifidum, and also very occasionally withE. cordatum.Similarly,M. ferruginosawas also found with 5.purpureus, E. flavescensandE. pennatifidum.This indicated that the associations are not as specific as had been thought.