Splendrillia dissimilis Fallon, 2016, new species

Splendrillia dissimilis, new species

(Plate 150)

Type material. Holotype 13.2 x 4.9 mm, collected April 1958, ex Nowell-Usticke coll. (AMNH ICZ 249987); 4 paratypes originally from the same lot as the holotype: 12.3 x 4.7, 13.1 x 4.9, 11.1 x 4.3 & 8.9 x 3.8 mm (AMNH ICZ 249988).

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

Range and habitat. Known only from the type locality. The depth was not provided with specimens. Based on the condition shells in the large multi-species lot, they were probably collected as empty shells in the intertidal area.

Description. Shell small (to 13.2 mm), fusiform, with a truncated anterior; whorls with a concave sulcus, angular, almost knob-like shoulders and nearly straight sides, number up to approximately 9, the last is 57% of the total length; ribs numerous; aperture oval with a short anterior canal. The last whorl appears somewhat flattened mid-whorl. Protoconch of approximately 2 smooth whorls. Axial sculpture of low, opisthocline ribs with round crests that become ridged at sulcus, where they are abruptly reduced in sulcus, and evanesce below whorl periphery before anterior fasciole, 10–13 on penultimate and 6–11 on last whorl to varix. Space between ribs less than their width. Growth striae throughout, moderately heavy, heaviest on outer lip; shell surface somewhat dulled by the striae. Varix broad, hump-like, approximately ¼–⅓-turn from edge of the outer lip. Spiral sculpture of ridges or threads on anterior fasciole. Sulcus concave, with much reduced, recurved ribs and growth striae. Outer lip flattened from varix to edge, with 1–3 strengthening axial folds, one aligned under anal sinus, another at lip’s edge, which is thickened in older specimens; edge forms a flattened arc from anal sinus to the anterior canal without an inflection along the anterior canal; stromboid notch weak. Anal sinus deep, apex adjoins suture behind parietal callus, outer side straight to slightly divergent. Inner lip recumbent, narrow, thin, produced into a short erect lip anteriorly on canal, unemarginate on anterior canal, formed into a callus posteriorly. Anterior canal short, barely delineated at the anterior end of the aperture; with spiral ridges on anterior fasciole, fasciole not swollen; end slightly notched. Color creamy yellow with a mid-whorl orange-brown band that spreads between the ribs and pools just below the sulcus, and a fainter band on the shell base. Columella, aperture, and spire tip white, not creamy yellow, on some specimens.

Remarks. Taxonomy. Splendrillia dissimilis has all the characteristics of Splendrillia: axial ribs that are greatly reduced at the sulcus, opisthocline ribs that fade below the whorl periphery, and outer lip that joins the suture behind the sulcus. Variability. The average total length of five measured specimens is 11.72 mm (8.9–13.1 mm), and their average W/L is 0.388. Identification. Splendrillia dissimilis is similar to S. cruzensis, new species, S. karukeraensis, new species, and S. interpunctata (E.A. Smith, 1882). From S. cruzensis it differs in being somewhat stouter (average W/ L ratio of 0.388 versus 0.363), in having more angular shoulders, and a different color, creamy yellow and orange-brown versus white, rose, and deep rose. From S. karukeraensis, it differs in having slightly shorter ribs, more angular whorls, and a different color, creamy yellow with orange-brown bands versus a creamy white with golden brown bands. From S. interpunctata it differs in having a narrower shell (average W/L ration of 0.388 versus 0.429), longer, narrower and usually more ribs (10–13 versus 9–11 on the penultimate whorl), and a different color, creamy yellow with orange-brown bands versus white with light to dark rose or golden yellow with carmine or golden brown between ribs.

Etymology. The Different Splendrillia. From the Latin adjective dissimilis, meaning different or unlike. Originally from the same lot from the Nowell-Usticke collection and mistaken for Splendrillia cruzensis, new species but afterwards recognized as different.