Noumea subnivalis? from Japan

Dear Yasuhiro,
Thanks for the photo, but I think this is probably Chromodoris verrieri rather than Noumea subnivalis.

I am still having difficulty identifying N. subnivalis. In the Baba's description of N. subnivalis he notes:
"the back is pure white (snow white) without any sign of yellow or orange-yellow spots on it. The mantle margin has a double border of orange-yellow at the edge and yellow inside. ... The rhinophores are reddish purple above and colourless below. The branchial plumes are almost entirely pure white ...."

Compare this to the similarly coloured:
• Noumea nivalis - has a single orange-yellow band around the mantle edge; the upper half of the rhinophore club is orange, the lower white, and the white gills are orange tipped. There can sometimes be a few diffuse orange spots on the mantle.
• Chromodoris verrieri - the outer band around the mantle border is red, not orange-yellow, and the rhinophore club is red with white edging to the lamellae.

In N. subnivalis, Baba describes the rhinophore as "reddish purple at the tip and white below", but I am not sure if he is referring to just the club or the rhinophore stalk as well. If it were not for the radular morphology, as described by Baba, I would consider N. subnivalis to be almost certainly a synonym of C. verrieri. One very distinctive point is Baba's description of the background colour being "pure white (snow white)" which suggests that it has an opaque white background colour which is unusual as in most species the colour is a translucent white. Interestingly C. verrieri also has an opaque white background colour.

I guess what we have to try and find is an animal with an 'orange-yellow' outer and yellow inner mantle margin.

References:
• Baba, K (1987) A new species of Noumea from Ogi, Toyama Bay and vicinity, Japan (Nudibranchia: Chromodorididae). Venus, The Japanese Journal of Malacology, 46(1): 19-24.
• Baba, K (1987): Noumea sp. from Echizencho Coast, Japan. Janolus, 69: 2.

Best wishes,
Bill Rudman