Viriiella Schröder, Schächinger, Bouchet & Haase, 2024, gen. nov.

Genus Viriiella gen. nov. (by monotypy) urn:lsid:zoobank.org:act: C856F38F-7BDC-4DD6-9B57-22E31943C654 Type species Viriiella touaouroua sp. nov., by monotypy. Diagnosis Shell small (<1.5 mm high), cylindrical to cylindro-conical, transparent, protoconch smooth; central tooth of radula with a single pair of basal cusps, lateral teeth with solid neck-region and square face; the operculum has neither smear nor peg in the attachment area; the stomach has no proximal caecum; the renal oviduct bends twice in opposite directions, first 180°, then 270° and bears distally a seminal receptacle; the bursa copulatrix is club-shaped and extends straight beyond the albumen gland; the penis is simple without glands or muscular appendages. Etymology Viriiella, feminine, is derived from ‘virii’, which means ‘small’ in nââ numèè, the language spoken in the region where the type species has been found. Description SHELL. Small (<1.5 mm high), cylindrical to cylindro-conical, transparent, periostracum practically colorless, protoconch smooth. OPERCULUM. Ovate, thin, yellowish, paucispiral, nucleus excentric, without smear or peg. EXTERNAL FEATURES. Epidermis without pigment, eyes black, small. MANTLE CAVITY. Ctenidium with small number of filaments; osphradium ovate. DIGESTIVE SYSTEM. Typical taenioglossate radula with rhachis (= central), lateral, inner and outer marginal teeth; central tooth with a single, large pair of basal cusps; lateral tooth with solid neck and square face; stomach without proximal caecum; pallial rectal loop simple and wide. FEMALE GENITALIA. Ovary a simple sac; renal oviduct describing almost a triangle, bending first almost 180° backwards, descending almost straight and then bending forward, the descending part thickened, glandular, small receptaculum seminis arising anterior to these loops; bursa copulatrix elongate club-shaped extending straight behind albumen gland; capsule gland with two portions. MALE GENITALIA. Testis lobate, vas deferens entering prostate medio-ventrally, distal vas deferens originating on distal end of prostate; penis simple, without glands or lobes. Remarks Among tateid genera, Viriiella gen. nov. probably resembles most Fluviopupa occurring on Lord Howe Island and the archipelagos of Vanuatu, Fiji and the Australs with respect to the arrangement of the renal oviduct and the distal position of the seminal receptacle. However, the distal counter-clockwise loop of 270° seen in most Fluviopupa (e.g., Haase et al. 2005, 2006) is here at best insinuated. In Fluviopupa, the protoconch is wrinkled and not smooth, though the operculum may have a white smear, the central radular tooth bears two to five pairs of basal cusps instead of one, the neck region of the lateral tooth is membranous and not solid, and the face rectangular rather than square. From the genera of the New Caledonian Hemistomia -clade, Viriiella differs in the same shell and radular features. The operculum in Hemistomia Crosse, 1872, and allies, including Leiorhagium Haase & Bouchet, 1998, bears long pegs, and the proximal loop of the renal oviduct is bent anteriorly in Leiorhagium. The genetic and phylogenetic justification of the genus is presented below.