Up to eight ceratal rows, ground colour translucent greyish, ceratal cores white to dark greyish, ceratal tops dull reddish, no apical white spot, anterior cerata with prominent dark brownish basal spot, sparse white spots in the first half of the dorsal part, white gonad spherules very dense, cerata considerably widened at top with smaller separate cupola-shaped tip, central tooth narrowly triangular with largely non-pitted top and only few denticles, up to ten small denticles, irregular in size; no accessory penial gland, penis unarmed.
Central parts of the Pacific coast of main Japanese island Honshu; potentially can occur at the southern parts of Honshu and Kyushu.
After the Japanese name hyōtan (瓢箪, ヒョウタン) for the calabash Lagenaria siceraria, the fruits of which are very similar in shape to the peculiar cupola- shaped tip of cerata of this new Myja species.
- Martynov, A.; Mehrotra, R.; Chavanich, S.; Nakano, R.; Kashio, S.; Lundin, K.; Picton, B.; Korshunova, T. (2019). The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia). ZooKeys. 818: 89-116., available online at https://doi.org/10.3897/zookeys.818.30477
- Myja longicornis, Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition, 2018 - Terrence Gosliner, Ángel Valdés and David Behrens
- ウメガエミノウミウシ（新称）, 日本のウミウシ, 2018 - 中野 理枝
- Myja longicornis, Nudibranch and Sea Slug Identification Indo-Pacific, 2015 - Terrence Gosliner, Ángel Valdés and David Behrens
- Eubranchus sp. 7, 本州のウミウシ, 2004 - 中野 理枝