Ithycythara bahamense Fallon sp. nov.

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Fig. 73A–J

Differential diagnosis

Ithycythara unid. sp. M is similar in most respects but has angled whorls, not shouldered ones.

Ithycythara pentagonalis (Reeve, 1845) has 5, not 6 ribs per whorl, stronger ribs, and is larger (> 5.9 mm, not including a missing portion of anterior canal, versus 4.7 mm, the largest I. bahamense Fallon sp. nov.).

Ithycythara unid. sp. T is larger and has a protoconch of 2¼ not 1½, whorls.

Ithycythara unid. sp. U has 2 protoconch whorls that end with a few riblets.

Etymology

Ithycythara bahamense Fallon sp. nov., the Bahamas Ithycythara, is named after the country from which specimens have been collected to date.

Type material

Holotype

BAHAMAS • 3.7 × 1.4 mm; East Grand Bahama District, Gold Rock; 26°30′ N, 78°22′ W; depth 24 m; J. Worsfold leg.; ANSP 369736.

Paratypes (8 specs)

BAHAMAS • 1 spec., 3.6× 1.3 mm; same data as for holotype East Grand Bahama District, Gold Rock; 26°30′ N, 78°22′ W; depth 24 m; J. Worsfold leg.; ANSP 369736 • 2 specs, 3.7× 1.4 and 3.7 × 1.5 mm; Grand Bahama Island, Indian Cay; 26°42.75′ N, 78°39.25′ W; depth 24 m; J. Worsfold leg.; ANSP 366929 • 1 spec., 3.2 × 1.2 mm; Grand Bahama Island, Borco Pipelines, 5 mi. [8 km] W of Freeport; Jun. 1982; 26°30.5′ N, 78°46.5′ W; depth 35 ft [11 m]; J. Worsfold leg.; ANSP 370846 • 1 spec., 3.2 × 1.3 mm; Grand Bahama Island, Borco Pipelines, 5 mi. [8 km] W of Freeport; 26°30.5′ N, 78°46.5′ W; depth 35 ft [11 m]; Jun. 1982; J. Worsfold leg.; ANSP 370845 A • 2 specs, 4.2 × 1.7 and 4.0 × 1.5 mm; Grand Bahama Island; 26°31′ N, 78°46.5′ W; J. Worsfold leg.; ANSP 374464 • 1 spec., 4.7× 1.7 mm; Grand Bahama Island, Bootle Bay; 26°39.5′ N, 78°57′ W; depth 24 m; J. Worsfold leg.; ANSP 371869.

Description

Shell is small, of about 5 whorls total, teleoconch whorls turreted, with flat shoulders and straight sides. Sculpture of narrow ribs and a single peripheral row of nodules. Aperture narrow, with nearly parallel sides only a little wider than the short anterior canal, apertural dentition present. Protoconch of 1½ whorls, the tip large, the last bulbous, without riblets. Axial sculpture of 6 narrow, opisthocline ribs per whorl with wide interspaces. Ribs are aligned whorl to whorl and extend from suture to suture on spire whorls and evanesce on the last whorl before the anterior fasciole. Varix apertural, rib-like only stronger. Spiral sculpture of densely packed, microscopic grooves overall; weak nodules present on ribs at edge of shoulder, a distinct peripheral spiral cord lacking. Sulcus absent. Outer lip varicose, with a thin extension of shell along the base of the varix. Anal sinus a wide U-shaped rather shallow notch on the shoulder in front of the varix, set off the suture by a callus, sides divergent. Inner lip a narrow but thick, margined callus along the columella and parietal wall. Columella straight. Anterior canal short, narrow, semi-tubular, tip turned to the right when viewed ventrally, unnotched. Color white with a mid-whorl yellowish-brown band on last intercostal space, and traces of spiral lines of the same color below it.

Remarks

The morphology of Ithycythara bahamense Fallon sp. nov. has all the diagnostic characteristics of this genus outlined in beginning of Part 1, except for the number of protoconch whorls, which are less than the 2¼–3¼ that characterize most of the members of the genus Ithycythara.

The average length of 9 specimens is 3.8 mm (range 3.2–4.7 mm). The brown band is lacking in some specimens. One variant specimen has 7, not 6 whorls.

Range and habitat

Bahamas; depth 11– 24 m.