Ulva lactuca

Paula Lightfoot Mussel 3mm x 2mm - very hairy! Found on mid-intertidal rocky shore near Whitby. We wondered if it could be Modiolus modiolus or Modiolula phaseolina...but I've just read that Mytilus edulis sometimes have hairy spat too. Looking in Paul Chambers and Hayward and Ryland for inspiration but they don't say much about the spat.

Chris Barrett Are the hairs hydroids? Could be M.edulis if so

Bernard Picton There's a great bivalve site on the National Museum of Wales web pages: http://naturalhistory.museumwales.ac.uk/britishbivalves/browserecord.php?-recid=93

Andy Pange Sharkbait Richardson Looks like Modiolus barbatus to me

Steve Wilkinson I think Modiolula phaseolina. You can separate from barbatus by whether the spines as serrated on one side or not (phaseolina is not) and be absolutely sure if you can open it and look for the little pocket of crenulations - as per the link Bernard provided.

Paula Lightfoot Thanks everyone! The actual specimen is in the (i hope) safe hands of Royal Mail on its way to our Conchological Society Recorder right now so I can't open it up. It was found quite high on the shore, attached to a blade of Ulva lactuca. Andreia Salvador, Curator of Marine Mollusca at the NHM also thinks it is Modiolula phaseolina from the photographs.

Could it be a juv Modiolus barbatus