Splendrillia cruzensis, Fallon, Phillip J., 2016

Fallon, Phillip J., 2016, Taxonomic review of tropical western Atlantic shallow water Drilliidae (Mollusca: Gastropoda: Conoidea) including descriptions of 100 new species, Zootaxa 4090 (1), pp. 1-363 : 294

Splendrillia cruzensis , new species

( Plate 149 )

Drillia coccinata auct. non (Reeve, 1845) is a misidentification by Nowell-Usticke (1959: 81).

Type material. Holotype 10.6 x 3.9 mm, April 1958, ex coll. Nowell-Usticke (AMNH 192603); paratypes from the same lot as the holotype (only 13 of 64 measured): 13.9 x 4.5, 12.7 x 4.7, 12.5 x 4.1, 13.0 x 4.7, 11.5 x 4.1, 11.1 x 3.9, 15.4, 10.4 x 3.9, 12.0 x 4.4, 10.3 x 4.1, 9.9 x 3.7 & 11.8 x 3.9 mm, (AMNH ICZ 249986); 1 spec., 11.3 x 4.3 mm, St. Croix, U.S. Virgin Is., M. Hayes! (UF 163009); 1 spec., 12.4 x 4.6 mm, Pointe des Fleches, St. Croix, U.S. Virgin Is., G. Usticke! Jun 1958 (UF 158124); 1 spec., 10.4 x 4.0 mm, Judith’s Fancy near Salt River, near dock entrance, St. Croix, U.S. Virgin Is., G. Usticke! 10 Apr 1958 (UF 158125); 2 spec., 13.0 x 4.4 & 9.5 x 3.8 mm, Pointe des Fleches, St. Croix, U.S. Virgin Is., D. Steger! 1976 (DMNH 114829).

Type locality. Pointe des Fleches, St. Croix, U.S. Virgin Is.

Range and habitat. U.S. Virgin Is. (St. Croix). Depth and substrate unknown; based on their condition, specimens were probably collected as empty shells in the intertidal area.

Description. Shell small (to 15.4 mm), fusiform, slender, with a truncated anterior, whorls slightly convex, to approximately 9, surface of shell smooth but dull, surface sculpture of numerous low ribs. Protoconch of approximately 1¾–2 smooth whorls. Axial sculpture of low ribs with round crests that terminate at sulcus and evanesce below whorl periphery before anterior fasciole, 10–13 on penultimate and 7–9 on last whorl to varix. Growth striae throughout, heavy and dense rendering the shell surface less glossy. Varix broad, hump-like, approximately ⅓-turn from the edge of the outer lip. Spiral sculpture of widely spaced microscopic spiral lines or grooves over entire shell, developing into ridges anteriorly, most visible in the sulcus, otherwise mostly obscured by growth striae. Sulcus concave, with microscopic spiral lines and curved growth striae; ribs absent. Outer lip thin, flattened from varix to edge, with 1–3 axial folds; edge bent slightly inward posteriorly and forms a flattened arc from anal sinus to the anterior canal, without an inflection for the anterior canal; stromboid notch absent. Anal sinus deep, apex adjoins suture behind callus, outer side straight to slightly divergent. Inner lip recumbent, narrow, thin, unemarginate, produced into a short erect lip anteriorly on canal, formed into a low callus posteriorly. Anterior canal barely delineated at the anterior end of the aperture; with spiral ridges on anterior fasciole, fasciole not swollen. Color white with rose a blush over most of the whorl, deep rose between ribs. A narrow white spiral band is located just below the suture line, visible on the last whorl. Varix a deep rose patch dorsally, with a white central band.

Remarks. Taxonomy. Splendrillia cruzensis has all the characteristics of Splendrillia : axial ribs that terminate at the sulcus, oblique ribs that fade just below the whorl periphery, and outer lip that joins the suture behind the sulcus. Variability. The average total length of 18 measured specimens is 11.76 mm (9.5–15.4 mm), and their average W/L is 0.363. Identification. Splendrillia cruzensis is unique among its congers in possessing a slim shell with low ribs, round shoulders, and moderately heavy growth striae. It is most similar to S. dissimilis , new species, with which it was initially confused, but differs in being slimmer (average W/ L ratio of 0.363 versus 0.388), in possessing less angular shoulders, and in being a different color: white, rose and deep rose versus creamy yellow and orange-brown. From S. coccinata (Reeve, 1845) it differs in being larger (11.76 versus 7.88 mm average total length), possessing stronger growth striae such that the shell surface appears dull, not glossy; its ribs are lower, and shoulders more rounded. From S. interpunctata (E.A. Smith, 1882) it differs in being smaller, in having less angular shoulders, and in general possessing more ribs (10–14 versus 9–11 on the penultimate whorl). From S. karukeraensis , new species it differs in having slightly shorter ribs on the spire and last whorls, a slightly narrower shell (average W/L = 0.363 versus 0.390), and a different color (white with rose with deep rose markings versus light golden brown).

Etymology. The St. Croix Splendrillia , after the country of the type locality.

Figures

PLATE 149. Splendrillia cruzensis, new species. Upper panel. Figs. 1 – 3. Holotype, Pointe de Fleches, St. Croix (AMNH 192603). Fig. 1: ventral, lateral & dorsal views; Fig. 2 same, enlarged views of protoconch (not to scale); Fig. 3: apical view, V = varix, L = edge of outer lip. Lower panel. Figs. 4 – 17: paratypes. Fig. 4: Pointe de Fleches, St. Croix (DMNH 114829); Fig. 5: St. Croix (UF 163009); Figs. 6 – 17: Pointe de Fleches, St. Croix (AMNH ICZ 249986).