Genus Crucigera Benedict, 1887

Type-species. Crucigera websteri Benedict, 1887

Diagnosis. (from ten Hove & Kupriyanova 2009). Tube white or yellowish, opaque, circular to semi-circular in cross-section, with or without longitudinal keels and/or peristomes; tabulae may be present. Granular overlay absent, but outer layer may be shiningly hyaline. Operculum soft, funnel shaped, formed of fused radii. Base of funnel with 2–4 finger-like bosses. Peduncle smooth, cylindrical, without wings, separated from operculum by constriction; inserted proximal from first and/or second dorsal radiole on one side. Pseudoperculum present. Arrangement of radioles in two half to complete circles, up to 50 radioles per lobe in larger taxa. Inter-radiolar membrane present. Branchial eyes may be present. Stylodes absent. Mouth palps absent. Seven thoracic chaetigerous segments. Collar trilobed, tonguelets between ventral and lateral collar lobes absent. Thoracic membranes long, forming apron. Collar chaetae bayonet-shaped and limbate. Thoracic chaetae limbate, Apomatus chaetae absent. Thoracic uncini saw-shaped with 5–7 teeth, including simple pointed anterior fang. Triangular depression present. Abdominal chaetae flat trumpet-shaped, with denticulate edge. Abdominal uncini saw-shaped with 4–6 teeth anteriorly; rasp-shaped with 2–4 rows, 7–8 teeth in profile posteriorly. Long posterior capillary chaetae present. Achaetous anterior abdominal zone absent. Posterior glandular pad absent.

Remarks. The genus, with five species, was thoroughly revised by ten Hove & Jansen-Jacobs (1984). It is most similar to the nominal genus Serpula, the only difference being the finger-like bosses below the opercular funnel. However, a molecular phylogenetic study by Kupriyanova et al. (2008) demonstrated that both traditional genera Crucigera and Serpula most probably are paraphyletic.