Syntomodrillia bermudensis, 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 : 317-319

Syntomodrillia bermudensis , new species

( Plate 164 )

Type material. Holotype 10.8 x 4.3 mm, A.T. Guest & J.R.A. Lightbourn! Sep 1975 (UF 470346); 117 paratypes, all from the same lot as the holotype. 49 measured spec.: 14.8 x 4.8, 13.7 x 5.1, 7.6 x 3.3, 12.1 x 4.3, 10.4 x 4.0, 10.7 x 3.9, 9.8 x 3.4, 9.0 x 3.6, 10.6 x 4.2, 10.7 x 3.9, 10.6 x 4.1, 10.1 x 3.9, 10.3 x 4.1, 10.5 x 3.9, 10.2 x 4.0, 16.6 x 4.0, 9.3 x 3.5, 8.7 x 3.6, 9.9 x 4.1, 9.0 x 3.6, 7.9 x 3.1, 13.2 x 4.8, 13.6 x 4 ,7, 12.0 x 4.5, 11.2 x 4.1, 10.3 x 3.4, 10.8 x 4.3, 9.7 x 3.5, 9.0 x 3.6, 9.0 x 3.6, 9.3 x 3.6, 8.5 x 3.4, 8.5 x 3.3, 10.7 x 4.0, 11.0 x 4.1, 10.9 x 4.3, 10.6 x 4.0, 9.9 x 4.0, 10.0 x 4.1, 9.8 x 3.9, 9.9 x 3.9, 8.3 x 3.4, 8.7 x 3.7, 8.5 x 3.5, 9.1 x 3.8, 9.4 x 3.7, 9.6 x 3.6, 10.7 x 4.2 & 11.4 x 4.5 mm, A.T. Guest & J.R.A. Lightbourn! Sep 1975 (UF 470347).

Type locality. Off Tucker’s Town, Bermuda in 91 m.

Range and habitat. Known only from the type locality.

Description. Shell small (to 14.8 mm total length) fusiform, truncated anteriorly, glossy, translucent between ribs; up to 10 convex whorls, the last approximately 57% of total length; suture impressed, scalloped by ribs of preceding whorl. Aperture narrowly oval, a little wider than the anal sinus and anterior canal. Protoconch of approximately 2 smooth whorls, the first rapidly expands such that it is off center; the second somewhat bulbous but its diameter not exceeding the first teleoconch whorl. Axial sculpture of broad opisthocline ribs that run from suture-to-suture on spire whorls, to anterior fasciole on last, recurved in upper ⅓ whorl height; rib crests ridged, slightly concave in sulcus; that is, crests are higher at suture and anterior margin of sulcus, lowest at center of sulcus. Ribs about as wide as the intercostal space, number 10–13 on penultimate, and 6–9 on last whorl to varix. Varix convex, straight not opisthocline, higher and wider than preceding ribs, not hump-like; positioned about ⅓- turn from edge of outer lip. Spiral sculpture of closely spaced intercostal grooves, absent in sulcus, obsolete on rib crests but present on all teleoconch whorls. Grooves develop into fine threads on shell base, becoming strongest on anterior fasciole. Sulcus with crescent-shaped ribs reflecting outline of anal sinus, slightly excavated on ventral side. Growth striae also present, curved, heavier than on shell proper. Outer lip thin, flattened from varix, lip edge angled slightly into aperture; up to 4 strengthening axial folds across width of lip; edge of lip traces a low arc from and congruent with the anal sinus to anterior canal; stromboid notch broad and very shallow. Anal sinus deep, Ushaped, close to the suture, sides parallel; parietal lobe on one side; forward edge of outer lip at sinus bent out slightly. Inner lip narrow, recumbent, margined, thick on columella, thin on parietal wall, and formed into a low lobe on parietal wall side of the anal sinus. Anterior canal open, moderately long, unnotched; fasciole not swollen; columella straight. Color white, translucent between ribs, with a faint, narrow, golden brown spiral band just above the suture such that it is visible on spire whorls; a golden-brown patch present on varix.

Remarks. Taxonomy. Syntomodrillia bermudensis , new species has all of the characteristics of the genus: a slender shell (though more robust than others) with a moderately long anterior canal, ribs that extend from sutureto-suture, microsculpture of spiral lines between the ribs, and a high, narrow (not hump-like) varix. It is unique among its congeners in possessing a spiral color band (all others are monochromatic, except for a color patch on the varix.). Variability. The average total length of 50 specimens is 10.13 mm (7.6–14.8 mm) and their average W/ L ratio is 0.388. Examined specimens varied somewhat in the intensity of the central color band, which may be due in part to the age (most were collected empty), and in size at maturity (fully developed anal sinus), which is the same as the observed range in size (10.2–14.8). Identification. Syntomodrillia bermudensis is atypical among its congeners for its large last whorl, which is more streamlined in other species. It is also among the largest in size. Because of its unique color pattern, and large size, it is unlikely to be confused with known congeners. It superficially resembles Splendrillia but has ribs suture-to-suture, a longer anterior canal, and spiral grooves between ribs.

Etymology. The Bermuda Syntomodrillia ; named for the country of the type locality, where it is probably endemic.

Figures

PLATE 164. Syntomodrillia bermudensis, new species. Upper panel. Figs. 1 – 3: holotype, off Tucker’s Town, Bermuda (UF 470346). Fig. 1: ventral, lateral & dorsal views; Fig. 2: enlarged view of protoconch (not to scale); Fig. 3: apical view, V = varix, L = edge of outer lip. Lower panel. Figs 4 – 27: paratypes, all from the type locality.