Original description Elysia japonica

Dear Nishina,
Eliot (1913) published a paper based on preserved specimens in the collections of the Imperial University, Tokyo. Some species seem to have been accompanied by colour sketches, but for many of the specimens there seems to have been no accompanying information on the living animal. The specimens of Elysia japonica fall into that category. As I said earlier there seems to be no way we can easily identify Eliot's species.

Eliot's description is relatively short so I have copied it below:
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Elysia japonica sp. nov.
18 specimens. Locality? (No label found). The largest is about 20mm long and the wings are moderately ample. In two specimens which were dissected, the radula was found to contain six teeth in the ascending row, 15 in the descending and about 20 more of various sizes lying in a heap. The structure of the radula and the shape of the teeth is as usual in the genus. No denticles are to be seen. I think that this form is probably a new species distinguished by the following characters:
(1) Colour: In all the specimens the rhinophores and the tip of the tail are conspicuously black or very dark brown. Otherwise the colour is uniform and in the best preserved specimen is yellowish brown. The wings have no coloured borders and the head and pericardium are of the same colour as the dorsal surface.
(2) The arrangement of the dorsal surface. This is similar in all the specimens and I have not seen it in any other species. The pericardium is not ovate but is constricted in the middle. Its length is greater than its breadth but it is short in comparison with the length of the whole animal. The dorsal ridges which run into it are very distinct and the two hindmost, which run backwards towards the tail, are parallel to one another and enclose an area which is differentiated from the back and forms a smooth trench.
• Eliot, C.N.E. (1913) Japanese Nudibranchs. Journal of the College of Science, Tokyo Imperial University, 35: 1-47. [pp46-7]
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There are no illustrations. Basically we do not know what the animal looks like alive, where in Japan it was collected, or anything meaningful about its anatomy. My feeling is that this name is unidentifiable and should be ignored. It is possible that some of the original specimens still exist. If so I guess it might be possible to dissect them and see if there are any recognisable anatomical characters which could be used to identify the species. If the original type material is shown to be lost then it is possible under the International Rules for a research worker to choose another specimen and designate it to be the neotype of the species. However since neither we, nor Eliot, had any idea of the animal's colour or where it came from in Japan, it seems better to just ignore his name.
Best wishes,
Bill Rudman