Acteocina, Gray, 1847

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 705-706

Genus ACTEOCINA Gray, 1847

Acteocina Gray, 1847: 160 . Type species: Acteon wetherillii Lea, 1833 [= Acteocina canaliculata (Say, 1822) ; Pleistocene and Recent, western Atlantic and Caribbean], by original designation.

Synonyms:

Tornatina A. Adams in Sowerby, 1850: 554. Type species: Bulla voluta Quoy & Gaimard, 1833 [Recent, Guam], by subsequent designation of Cossmann (1895).

Utriculastra Thiele, 1925: 269 . Type species: Volvaria canaliculata Say, 1822 [Recent, Caribbean], by original designation.

DIAGNOSIS. — Shell morphology. Shell external, solid, oval to elongate. Aperture longitudinal, long, anteriorly rounded. Spire short, conical. Columella slightly thickened and often with an anterior callus. Operculum absent. Protoconch flattened, attached to the teleoconch by the aperture.

Anatomy. Large headshield, with the posterior end divided into 2 projecting lobes. Radula with a rachidian tooth and one denticulate lateral tooth on each side of the half-row. Gizzard with 3 lobate plates.

REMARKS. — Marcus (1977) considered Acteon wetherillii Lea, 1833 , the fossil type species of Acteocina , to belong to either the Retusidae or Cylichnidae , but different from Acteocina as in common usage by modern authors. She was unable to determine the taxonomic position of this fossil species, so she decided to use the next available name for the genus commonly known as Acteocina , which is Tornatina A. Adams in Sowerby, 1850. She also maintained Utriculastra Thiele, 1925 as different from Tornatina , because of anatomical differences in the number of denticles on the radular teeth and the position of the oesophagus.

In contrast, Mikkelsen & Mikkelsen (1984) commented that Acteon wetherillii is a synonym of the Recent species Acteocina canaliculata (Say, 1826) , which represents the common usage of Acteocina . Therefore the name Acteocina , with A. wetherillii as its type species, actually does correspond with the common usage of the name. The original description of A. wetherillii (Lea 1833) and the redescription of A. canaliculata by Mikkelsen & Mikkelsen (1984) reveal that their shell morphology is very similar. Mikkelsen & Mikkelsen (1984) also added Utriculastra Thiele, 1925 and Cylichnella Gabb, 1873 to the synonymy of Acteocina , following Gosliner (1979), who regarded Utriculastra and Cylichnella as synonyms. Utriculastra was originally based on A. canaliculata (the type species by original designation), and therefore it is a synonym of Acteocina when A. canaliculata and A. wetherillii are considered synonyms, as here and by Mikkelsen & Mikkelsen (1984). However, Cylichnella differs considerably from Acteocina in shell morphology. Gosliner (1979) commented that Cylichnella has an involute spire whereas Utriculastra possesses a projecting apex. Despite these differences he regarded these two genera as synonyms because of a similar anatomy.

Because of the remarkable differences in shell morphology between Cylichnella and Acteocina , these two genera are here maintained as distinct.

Marcus (1977) and Mikkelsen & Mikkelsen (1984) revised several species of Acteocina and provided detailed anatomical descriptions. The diagnosis above is based on these two papers.