Tritonia insulae (Baba, 1955)

Description

A small Tritoniidae, body length 25 mm. The body is uniformly white, with vermilion gills. Head-veil margin bears 3-4 simple finger-like processes per side. Rhinophore-sheath margin serrate. The dorsum is densely covered with fine granules; the body sides are smooth. Cerata 12 per side. The genital orifice opens below the third right gill; the anus between the third and fourth right gills; the nephroproct directly above the anus. The masticatory edge of the jaw plate is covered along its entire length by 3-4 rows of scale-teeth. Radula formula 30×40-46.1.1.1.40-46. The central tooth has 3 cusps; the first lateral is asymmetric; the other laterals are all smooth and awl-shaped. The left and right livers are fused, and there are no stomach plates.

Distribution

Type locality is Amanawa-ba Kannon-bori-deshi, Sagami Bay (70 m depth, December 1953, single specimen). The original description (Baba, 1955) records the species only from the type locality, in deeper water.

Etymology

The specific epithet insulae is Latin for "of the island" (genitive). The original description does not give an explicit etymology paragraph; the descriptive sense is uncertain. The Japanese name "Shira-hime-hanagasa-umiushi" (white-princess flower-cap sea slug) likens the white body to a white princess.

Remarks

Originally described as Duvaucelia (Duvaucelia) insulae (Family Duvauceliidae). The Nomenclatural Review at the end of Baba 1955 Supplement (p.63) reassigned it to Tritonia insulae (Family Tritoniidae). The colour resembles that of Paratritonia lutea (Kiiro-hanagasa-umiushi), but the latter has a uniformly yellow body with vermilion gills; the two species differ in the positions of the cerata, genital orifice, and anus, and in jaw and radula details.

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References

• シラヒメハナガサウミウシ（新称）, 生物學御研究所編. (1955). 相模湾産後鰓類図譜〈補遺〉. 岩波書店.