"The striped Hypselodoris in your photo is Hypselodoris nigrostriata because the lines are more or less oblique. In the very similar species, Hypselodoris zephyra the lines are parallel. I thought they were the same species, but then Rudie Kuiter showed me a lot of his pictures from Bali where both species seem to occur together and he has made a strong argument that they are separate in the new book Nudibranchs of the World. So I haven’t made up my mind yet. One other character supposedly only possessed by Hypselodoris nigrostriata is a yellow border to the mantle. I really cannot see this yellow band in the animal in your picture, so maybe that character is no good?"
Comment from Richard Willan
The striped Hypselodoris in your photo is Hypselodoris nigrostriata because the lines are more or less oblique. In the very similar species, Hypselodoris zephyra the lines are parallel. I thought they were the same species, but then Rudie Kuiter showed me a lot of his pictures from Bali where both species seem to occur together and he has made a strong argument that they are separate in the new book <em>Nudibranchs of the World</em>. So I haven’t made up my mind yet. One other character supposedly only possessed by Hypselodoris nigrostriata is a yellow border to the mantle. I really cannot see this yellow band in the animal in your picture, so maybe that character is no good?