Lissodrillia ebur (Dall, 1927) Dall, 1927

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 : 241

Lissodrillia ebur (Dall, 1927) , new combination

( Plate 122 )

Cymatosyrinx ebur Dall, 1927: 42 .

Type material. Syntypes are in USNM 107948 (about 20 according to Dall). The illustrated syntype is 7.9 x 2.7 mm.

Type locality. Albatross Station 2668, off Fernandina, Florida, 30°58'N, 79°38'W, in 294 fms [538 m].

Other material examined. An additional 10 specimens were examined that are likely this species: 3 spec., 7.3 x 2.9, 8.3 x 3.1 & 5.9 x 2.4 mm, in 520 m, MRV Lady Lisa, Geryon Crab Survey, 1985 –86, Blake Plateau, SE of Charleston, South Carolina, L. Campbell! (L. Campbell coll.); 5 spec., 5.2 x 2.1, 5.2 x 2.0, 5.5 x 2.2, 5.0 x 2.1 & 4.7 x 1.9 mm, in 457 m, W of Hillsborough Co., W Florida (ANSP 336398); 2 spec., 6.7 x 2.5 & 5.3 x 2.3 mm, in 308– 323 m, about 2 km W offshore of Pinellas Co., W Florida, 27°51.79'N, 84°59.82'W (EFG 25289).

Range and habitat. South Carolina (Blake Plateau); E Florida; W Florida. Reported from 308– 538 m.

Description. Shell very small (to 8.3 mm) but sturdy, fusiform, surface smooth but opaque; not glossy, of up to about 7¾ convex whorls, peripheries about mid-whorl, the last about 60% of total shell length; suture impressed. Sculptural elements only of ribs; aperture oval, with a short, wide anterior canal and large anal sinus. Protoconch of 1¾ large smooth glossy whorls, the beginning of the first slightly imbedded in the last whorl such that the spire tip appears blunt. The protoconch lip is visible where its glossy-smooth surface meets the contrasting duller, opaque surface of the adult shell. Axial sculpture of low, broad, arched ribs, variable but generally wider than their interspaces, lower and narrower on shoulder in sulcus near suture and fade at anterior fasciole. Rib crests are round. Growth striae microscopic. Varix larger than ribs, about ¼–⅓-turn from edge of outer lip. Spiral sculpture absent. Sulcus absent, ribs recurved, lower, and narrower in sulcal region. Growth striae also curved reflecting past positions of the anal sinus. Outer lip thin, with low axial folds, smooth, edge slightly inrolled from anal sinus to beginning of anterior canal; stromboid notch absent. Anal sinus a deep notch on whorl shoulder near suture, outer edge divergent and congruent with edge of outer lip such that. Inner lip thin, margined, recumbent; extending over apex of aperture with a weak callus at anal sinus. Anterior canal short but well defined, open, unnotched. Color white.

Remarks. Taxonomy. Lissodrillia ebur has the characteristics of the genus: a small smooth shell with a short anterior canal, axial ribs that extend from suture to suture, an outer edge of the anal sinus that is divergent and congruent with the edge of the outer lip, forming a reverse “S” on lateral view of the shell, and a shell that lacks spiral sculpture. Variability. The average length of 11 specimens is 6.09 mm (4.7–8.3 mm); their average W/ L ratio is 0.394. Identification. The species is differentiated from its congeners by its opaque, dead-white color and relatively large size for the genus. Its convex whorls are fairly evenly arched in profile, unlike most other congeners with whorls that appear to “sag”. Its evenly convex whorls are somewhat reminiscent of those of Lissodrillia turgida , new species but that species is smaller (4.72 mm average total length, the largest = 7.3 mm) and possesses ribs that are more convex. Lissodrillia fasciata , new species has whorls with a similar profile, but is slimmer, translucent and possesses a mid-whorl color band.

Figures

PLATE 122. Lissodrillia ebur (Dall, 1927). Upper Panel. Figs. 1 – 3: syntype, off Fernandina, Florida (USNM 107948). Fig. 1: ventral, lateral & dorsal views; Fig. 2: apical view; Fig. 3: enlarged view of protoconch. Figs. 1 – 3 are SEM images courtesy of Ms. Yolanda Villacampa, Smithsonian Institution. Lower Panel. Figs. 4 – 5: Blake Plateau, SE of Charleston, South Carolina (L. Campbell coll.); Figs 6 – 7: 212 km W of Pinellas Co., W Florida (EFG 25289); Figs. 8 – 10: W of Tampa Bay, Pinellas Co., W Florida (ANSP 336398).