Cylichnium, Dall, 1908

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 699

Genus CYLICHNIUM Dall, 1908

Cylichnium Dall, 1908: 242 . Type species Utriculus domitus Dall, 1889 [Recent, Caribbean], by original designation.

Synonym:

Volvulopsis Schepman, 1913: 463 . Type species: Volvulopsis ancillarioides Schepman, 1913 [Recent, Indonesia], by original designation.

DIAGNOSIS — Shell morphology. Shell external, solid, elongate, with only 1 whorl visible. Aperture longitudinal, as long as the shell, anteriorly rounded. Columella slightly thickened and often with no folds. Operculum absent.

Anatomy. External morphology unknown. Radula with several simple and hamate lateral teeth. Rachidian teeth absent. Reproductive system monaulic, with a complex female copulatory organ. Penis unarmed.

REMARKS. — Cylichnium Dall, 1908 was originally described as a subgenus of Cylichnella Gabb, 1873 , and included three species: Utriculus domitus Dall, 1889 (type by original designation; from Guadeloupe, Caribbean Sea), Cylichnella pizarro Dall, 1908 (from the Pacific side of Panama) and Cylichnella atahualpa Dall, 1908 (also from the Pacific side of Panama) (Dall 1908). Subsequently, several other species were assigned to this genus: Cylichnium matsumotoi Habe, 1955 (from Japan), Cylichnium waldae Bouchet, 1975 (from the southeast Atlantic) and Cylichnium oliviformis (Watson, 1883) (from the Caribbean). Bouchet (1975) transferred Aceras africana Fischer in Locard, 1897 and Aceras fischeri Locard, 1897 to this genus, based on anatomical examination of newly collected specimens. The original description of Cylichnium (Dall 1908) indicates that the type species ( Utriculus domitus Dall, 1889 ) has a short, conical shell, with an aperture about 4/5 of the shell length and a pointed apex, which suggests that it is probably a juvenile of another species of the genus.

Schepman (1913) described the genus Volvulopsis based on the single species Volvulopsis ancillarioides Schepman, 1913 (from Indonesia, in 959-1301 m). Subsequent authors regarded Volvulopsis Schepman, 1913 as a synonym of Cylichnium Dall, 1908 (see Bouchet 1975). The shell characteristics of V. ancillarioides resemble those of some species assigned to Cylichnium by Habe (1955) and Bouchet (1975).