Form B of Ancula. gibbosa sensu lato from Maine, Atlantic coast of eastern USA. September 2021. © J. Goddard. This form lacks an orange or yellow dorsal line to the rear of the gills like that found on many of form A in Europe. The single publicly available sequence of an A. gibbosa from eastern North America has a CO1 gene difference of over 3% from European specimens, raising the possibility of it being considered as a separate species.