Leucosyrinx Dall 1889

Genus Leucosyrinx Dall, 1889 Pleurotoma (Leucosyrinx) Dall, 1889: 75. Type species Pleurotoma (Pleurotomella) verrillii Dall, 1881 (OD). Diagnosis Shell small to large, reaching 90 mm in length (L. bolognai), narrow to broad fusiform, spire high, siphonal canal distinct, medium-long to long. Shell uniformly colored, from off-white to beige and light brown. Protoconch paucispiral, small, diameter about 1 mm, of 1.5–1.75 rounded whorls. Teleoconch whorls roundly angled at shoulder, at least on upper whorls, with well-defined concave subsutural ramp. Axial sculpture of usually strong, oblique, axial ribs, present on shoulder and below, not extending to subsutural ramp. Ribs can be reduced just to knobs on shoulder, but can extend to periphery and even shell base. Spiral sculpture from weak to rather strong, of uniform spiral cords, that can be present or absent on subsutural ramp. Anal sinus moderately deep, subsutural, broadly arcuate, extends across entire subsutural ramp, and confluent with large forward extension of outer lip. Operculum narrow to medium-broad leaf-shaped, nucleus terminal. Radular marginal teeth duplex (Fig. 2), narrow to broad lanceolate, rather flat in dorsal view, particularly in anterior part (tooth tip). Major limb pointed, with sharp cutting edges (Fig. 2C – bl), broadest at midlength and narrowing towards both ends, with rather distinct socket on dorsal surface where accessory limb embeds. Central formation very weak to completely absent, of indistinct symmetrical folds of the membrane and rarely with very weak central cusp. Remarks As confirmed by molecular data, Leucosyrinx exhibits significant variability in shell shape, size, and, to a lesser extent, in spiral and axial sculpture. Nonetheless, certain key diagnostic features can be identified. The axial folds, which may be limited to nodules on the shoulder or extend to the shell periphery, are consistently absent on the subsutural ramp. The ramp, including the zone immediately adjacent to the upper suture, is either smooth or exclusively features spiral cords and lacks any other elements. The anal sinus located subsuturally, commences at the upper suture and extends across the entire ramp. Correspondingly, the sinus line in its upper part is prosocline and concave. Below, the sinus is confluent with a notable forward arcuate projection of the outer lip, enhancing the impression of depth in the generally medium-deep sinus. There are several genera, superficially similar to Leucosyrinx. The species treated here as members of Leucosyrinx were often confused with genera discussed below, and vice versa some species belonging to those genera were erroneously attributed to Leucosyrinx.