Rictaxis, Dall, 1871

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 594-596

Genus RICTAXIS Dall, 1871

Rictaxis Dall, 1871: 136 . Type species: Tornatella punctocaelata Carpenter, 1863 [Recent and Pliocene, northeastern Pacific], by original designation.

Synonym:

Actaeonidea Gabb, 1872: 273 . Type species: Actaeonidea oryza Gabb, 1863 [Miocene, USA], by monotypy.

DIAGNOSIS. — Shell morphology. Shell external, fragile to solid, ovate, and transversely sulcate; spire variable. Aperture variable in size, anteriorly rounded. Inner lip slightly thickened. Columella with a small and simple fold. Umbilicus closed. Operculum present.

Anatomy. Radula composed of several denticulate lateral teeth. The inner lateral teeth are short whereas the outer teeth are much more elongated. Jaw with several denticulate elements.

REMARKS. — Dall (1871) introduced the genus Rictaxis based on the shell morphology, to include species with the columella obliquely truncated at the base. Later Marcus (1972) redescribed this genus using anatomical characters and included two species, Rictaxis punctocaelatus (Carpenter, 1864) , the type species, and Rictaxis punctostriatus (C. B. Adams, 1840) . The diagnosis above is based on Marcus (1972).

FIG. 3. Collection localities of species of Acteon Montfort, 1810 in the southwest Pacific:σ, Acteon cf. nakayamai Habe, 1952 . Z, Acteon ionfasciatus n. sp.

°, Acteon chrystomatus n. sp.

The radular morphology of Rictaxis is very similar to that of Japonacteon (see above), but the radular teeth of Japonacteon are all of similar size, whereas in Rictaxis the outermost teeth are much more elongated. A revision of the Acteonidae with a phylogenetic analysis is necessary to determine the validity of these names, but in the meanwhile Rictaxis is here used as valid.