F. bostoniensis from Maine, USA. December 2021. © J. Godden.
Cerata seem a little stouter than on European specimens, otherwise very similar. The molecular sequence of a single specimen from New Hampshire, USA, (Gen Bank KY129046) is only 1.67% different from that of three specimens from Scotland (AY345031 & KY513635) and Sweden (KY513637), and is insufficient to challenge acceptance of F. bostoniensis as an amphiatlantic species (Carmona, 2020).