Melanella, Bowdich, 1822

Souza, Leonardo Santos De, Pimenta, Alexandre Dias & Barros, José Carlos Nascimento De, 2021, Revision of the deep-sea Eulimidae (Gastropoda, Caenogastropoda) from off Northeast Brazil, Zootaxa 4927 (4), pp. 451-504 : 482

Melanella sp. 1

( Figure 17 A–G)

Material examined. Brazil: Off Pernambuco, REVIZEE Nordeste (08°46′00″S 34°44′00″O, 690 m), coll. RV Natureza, 18/xi/2000: MNRJ 35251 † [1 dd] .

Description. Shell subcylindrical, straight, reaching about 3.6 mm long, 1.0 mm wide. Larval shell vitreous, cylindrical, with about 2.0 whorls, 370 µm wide; smooth, except for microscopic striations close to suture, transition to teleoconch marked by an almost indistinct incremental scar. Teleoconch with about 7.0 whorls, flat outline; suture almost indistinct, sloping; subsutural zone about 20% of the whorl height; surface polished, sculptured by straight axial lines spaced every 10–15 μm ( Figure 17D ); incremental scars slightly demarcated, appearing at irregu-lar intervals. Last whorl about 40% of the shell length; base rounded. Aperture short, pear shaped, acute posteriorly and rounded anteriorly; outer lip thin, opisthocline, sinuous, slightly retracting near the suture and after projecting, maximum projection in the lowermost third of the height, retracted in distal region; inner lip sinuous, sloping, reflected, well demarcated. Not umbilicate. Shell colourless.

Measurements. MNRJ 35251†, 9 whorls, SL= 3.6 mm; BWL= 1.4 mm; AL= 0.9 mm; SW= 1.0 mm; AW= 0.5 mm.

Remarks. The species that most resembles Melanella sp. 1 ( Figure 17 A–G) is Melanella jeffreysi ( Tryon, 1886) ( Figure 17 H–J), with the subcylindrical shape, dome shaped apex, similar outline of the outer lip and similar dimensions of the protoconch (~ 370–380 µm wide) and teleoconch. According to Jeffreys (1884), the shell surface of M. jeffreysi (as “ Eulima solida ”) is covered by longitudinal, extremely thin axial lines, but Bouchet & Warén (1986) disagree with Jeffrey’s description. The latter authors commented that there are “only a few scattered, indistinct, very thin axial lines”, and that Jeffrey’s description is possibly related to a specimen collected in the PORCUPINE 1869 Expedition stn. 23. Bouchet & Warén (1986) identified the latter specimen as M. orphanensis despite uncertainties. We examined the lectotype of E. solida (USNM 133126) under SEM and verified that the teleoconch surface is almost entirely smooth, marked only by strong incremental scars ( Figure 17J ). Melanella sp. 1 has thin axial lines, distributed over the whole teleoconch in extremely small intervals ( Figure 17D ).

Melanella sp. 1 differs from M. orphanensis ( Figure 17K ) by the straight spire, with shallower sutures and a slower increasing diameter.

Despite the differences mentioned above, we refrain to describe Melanella sp. 1 as new because there are several Melanella s.l. with a subcylindrical shape currently known or awaiting description ( Bouchet & Warén 1986; Personal observation). We prefer to wait for new material to become available.

Geographical distribution. Brazil: Pernambuco.

Bathymetric distribution. 690 m.

Figures

FIGURE 17. A–G. Melanella sp. 1: MNRJ 35251. H–J. Melanella jeffreysi: lectotype of Eulima jeffreysi Tryon, 1886, USNM 133126. K. Melanella orphanensis Clarke, 1974: holotype, CMNML 66345. D, J. Detail of the teleoconch surface. G. Detail of protoconch, apical view. Scale bars: A–C, H, I, K= 1.0 mm. D= 50 µm. E, F, J= 200 µm; G= 100 µm. Credits: J, courtesy of USNM; K, courtesy of J-M Gagnon (CMNML).