Toyama Bay, The Japan Sea, 30-50m, 13-24 July 2002, from a fishing net. Photos: Shigeru Hayashi
In both of Baba's descriptions (1937, 1949) he notes the colour as being 'generally olive in colour' so these photos give us a much better idea of this species' colours. They match one of the illustrations in Baba, 1949 (Pl.34, fig. 126) very well. The animal is a translucent cream with a pattern of dark brown and orange brown. The sides of the body are pustulose with a network of orange brown running between the pustules. The mantle and oral veil are essentially orange brown with a symmetrical pattern of dark brown patches along the edge of the mantle and at the base of the gills. It grows to 80mm.
Bergh (1905) described a species Tritonia olivacea from Indonesia. It is possibly congeneric with Baba's species, but until it is rediscovered and examined we can't say whether these 2 species are homonyms.
• Baba, K. (1937) A New Species of the nudibranchiate genus Marionia from Sagami Bay, Japan. Venus, Jap. Jour. Malac., 7(3): 115-120.
• Baba, K. (1949) Opisthobranchia of Sagami Bay, collected by His Majesty Emperor of Japan. Iwatani Shoten, Tokyo, 86-87.
Rudman, W.B., 2002 (December 2) Marionia olivacea Baba, 1937. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/marioliv