19 Rissoella diaphana COMPARE Rissoella opalina

19 Rissoella diaphana COMPARE Rissoella opalina

Rissoella opalina has 1: cephalic tentacles deeply and widely bifid. 2: snout slightly bifid. 4: yellowish hypobranchial gland with U shaped end, flounced margin and brown oval at its end. Croatia, Adriatic Sea. © A. Petani.