Cylichnoides Minichev, 1977

Chaban, E. M., 2016, Opisthobranch molluscs of « Cylichna occulta group » (Gastropoda: Opisthobranchia: Cylichnidae) from the Chukchi Sea and adjacent waters, The Bulletin of the Russian Far East Malacological Society 20, pp. 5-26 : 8

Genus Cylichnoides Minichev, 1977

Type species. Bulla occulta Mighels et Adams, 1842 ( OD).

Diagnosis. Shell is oval with spiral sculpture, spire completely sunken; penial sac well developed with strong muscular folds, prostate connected with lateral side of the penial sac; radula formula is 2:1:1:2; rachidians with a deep notch and irregular denticles that are composed sometimes in group on 2–4; three large gizzard plates of equal size and form; crop absent.

The genus includes five arctic species: C. occultus , C. validus , C. scalptus , C. densistriatus , and Cylichnoides sp. 1 . Two species of Cylichna from the tropical southwest Pacific have also been studied [ Valdés, 2008] for penial morphology; Cylichna biplicata (A. Adams in Sowerby, 1850) and C. involuta (A. Adams in Sowerby, 1850) have penial sac and tentatively can be included in Cylichnoides but more studies need to clarify their systematic position.