A revision of Hexacanalis Perrenoud, 1931 (Cestoda: Lecanicephalidea) and description of H. folifer n. sp. from the zonetail butterfly ray Gymnura zonura (Bleeker) (Rajiformes: Gymnuridae).

Hexacanalis Perrenoud, 1931 was erected for H. abruptus (Southwell, 1911) Perrenoud, 1931 based on the presence of six excretory vessels, a unique feature among the Lecanicephalidea. The genus has since been considered a junior synonym of Cephalobothrium Shipley & Hornell, 1906 or Lecanicephalum Linton, 1890, or as a genus inquirendum. Based on examination of the syntype series of H. abruptus, this species is redescribed and a lectotype designated. Examination of cestodes from the zonetail butterfly ray Gymnura zonura (Bleeker) from off Indonesian Borneo resulted in the discovery of a second species. Hexacanalis folifer n. sp. is unique among lecanicephalideans in its possession of an ovary that is U-shaped in cross-section and craspedote proglottids with prominent posterior dorso-ventral processes in the form of large lappets. The presence of six excretory vessels, confirmed in both species, supports the validity of Hexacanalis. An additional species, H. pteroplateae (Zaidi & Khan, 1976) n. comb., also from a butterfly ray, G. micrura (Bloch & Schneider) [as Pteroplatea micrura (Bloch & Schneider)], is transferred to this genus from Cephalobothrium Shipley & Hornell, 1906. A revised diagnosis of Hexacanalis is presented. Seven species of this genus remain species inquirendae. Hexacanalis appears to parasitise species of the Gymnuridae van Hasselt; however, specific identifications of the hosts are in need of re-evaluation. A summary of the cestode parasites of the Gymnuridae is presented.