Beth
Anadara(Scapharca) inequivalvis is an Australian species occurring in
Queensland through to the Northern Territory, a similar species is
Anadara(Scapharca) rufescens (Reeve,1844). Both of these species were described
without locality, which was not uncommon in those days. The orange stain you
refer to is more likely to be the latter species than inequavalvis.
Many of the Indo-Pacific species are now being found in the Mediterranean Sea
and other European localities, probably being introduced as a result of ship
ballast.

Kev Lamprell