Hypselodoris malacitana? from Portugal

Dear David,
I think this is Hypselodoris malacitana, but I am having some difficulty deciding the difference between this species and H. cantabrica. Both species seem quite variable in colour and both have colour forms with a median yellow line on the dorsum. Ortea, Valdés, García-Gómez (1996) mention that one of the distinguishing features of H. malacitana is a yellowish line down the posterior midline of the rhinophore which splits basally to form an inverted V. Looking at the photos of H. cantabrica on the Forum [messages #2124, #12745] they also have this same marking. If they are both H. malacitana as well, I have no idea how the two species can be differentiated. Any advice would be welcome.

• Ortea, J., Valdés, Á. & García-Gómez, J.C. (1996) Revisión de las especies atlánticas de la familia Chromodorididae (Mollusca: Nudibranchia) de grupo cromático azul. [Review of the Atlantic species of the family Chromodorididae (Mollusca: Nudibranchia) of the blue chromatic group.] Avicennia. Revista de Ecologia y Oceanologia y Biodiversidad Tropical. Supplement 1. 165pp.

Best wishes,
Bill Rudman