Eulima, Risso, 1826

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 : 466-468

Eulima sp. 1

( Figure 8 A–I)

Material examined. Brazil: Rio Grande do Norte: REVIZEE Nordeste (04°51′00″S 35°06′00″W, 375 m), coll. RV Natureza, 24/xi/2001: MNRJ 29631 † [1 dd], MNRJ 35215 † [1 dd] .

Description. Shell conical, apex rounded, reaching about 6.4 mm long, 1.6 mm wide. Larval shell with about 2.5 whorls, 290 µm wide, 370 µm in height; smooth, transition to teleoconch marked by a subtle incremental scar. Teleoconch with about 7.5 whorls, almost flat; suture shallow, slightly impressed, sloping; surface glossy and smooth; incremental scars weak, appearing at irregular intervals. Last whorl about 50% of the shell length; base elongated, slightly rounded outline, connected close to the most anterior region of the aperture. Aperture high, narrow, pear shaped, acute posteriorly and rounded anteriorly; outer lip thin, slightly sinuous, opisthocline, slightly projecting near the suture and slightly retracting in the distal region; inner lip sinuous, sloping and well demarcated. Not umbilicate. Shell vitreous or whitish, with a brownish spiral band at the suture of the larval shell.

Measurements. MNRJ 29631, 10 whorls, SL= 6.4 mm; BWL= 3.2 mm; AL= 2.3 mm; SW= 1.6 mm; AW= 1.0 mm.

Remarks. The shell surface of the two specimens examined is corroded ( Figure 8E ) and at first, it seems that it presents a sculpture of axial lines, like some species in the genera Melanella Bowdich, 1822 and Niso Risso, 1826 . However, this is an artifact as examined in SEM and there are only incremental scars ( Figure 8E ). The general shape and the aperture are more similar to Eulima s.s.

Other Eulima species that resemble Eulima sp. 1 are E. psila ( Figure 6 A–M) and E. grimaldii ( Figure 6P, Q ), both with a brownish spiral band at the protoconch. However, Eulima sp. 1 differs from E. psila by features of the protoconch, which has a smaller number of whorls (2.5 vs. 3.5 in E. psila ) and is shorter (370 µm vs. 420 µm), and by the outline of the outer lip, which is slightly protruding in E. sp. 1 ( Figure 8G ) and straight in E. psila ( Figure 6I ). Eulima sp. 1 also differs from E. grimaldii by features of the protoconch, which has less convex whorls in E. sp. 1 (see Figure 8H and Bouchet & Warén 1986: figure 93) and a smaller number of whorls (2.5 vs. 3.3 in E. grimaldii ). Furthermore, the body whorl comprises 50% of the shell length in E. sp. 1 and 40% of the shell length in E. grimaldii , and the aperture is relatively wider and higher in E. sp. 1 comparing shells with a similar number of whorls (AL= 2.3 mm, AW= 1.0 mm vs. AL= 1.6 mm, AW= 0.7 mm, holotype of E. grimaldii ).

Eulima sp. 1 can also be distinguished from Eulima incolor ( Figure 5F, G ) by the brownish spiral band on the protoconch, which is not present in E. incolor , and by the presence of several incremental scars on the teleoconch, while Bouchet & Warén (1986) described that E. incolor does not present any incremental scar on the teleoconch.

Despite the differences mentioned above, we refrain to name Eulima sp. 1 as a new species because of the almost inconspicuous features of the species. Most species of Eulima s.s. are very similar to each other, especially those that do not have a colored teleoconch and we prefer to leave this species undescribed until more samples become available.

Geographical distribution. Brazil: Rio Grande do Norte.

Bathymetric distribution. 375 m.

Figures

FIGURE 5.A–E. Eulima ephamilla Watson, 1883.A, B. Lectotype (herein designated) of E. ephamilla, NHMUK 1887.2.9.1589; C. Paralectotype of E. ephamilla, NMW 1955.158.11088. D, E. Holotype of Eulima rectiuscula Dall, 1890, USNM 87343. F, G. Eulima incolor Bouchet & Warén, 1986: holotype, MNHN-IM-2000-5660. Scale bars: 1.0 mm. Credits: A–C, courtesy of NHMUK; D. courtesy of NMW; F, G, courtesy of MNHN-IM.

FIGURE 6. A–L. Eulima psila Watson, 1883.A. Lectotype (herein designated), NHMUK 1887.2.9.1585. B. IBUFRJ 15233. C. MNRJ 27968. D. MNRJ 35203. E. USNM 433360. F–I, K. MNRJ 25613. J. MNRJ 34490. L, M. MNRJ 16888. N, O. Eulima sp., from Challenger stn. 24, NMW 1955.158.00654. P, Q. Eulima grimaldii Bouchet & Warén, 1986: holotype, MNHN-IM 2000-5659. I. Operculum, external surface. J, K. Detail of protoconch, frontal view. L. Detail of protoconch, apical view. Scale bars:A–F, M–P= 1.0 mm; G, H= 500 µm; I–K= 200 µm; L= 100 µm. Credits:A, courtesy of NHMUK; M, N, courtesy of NMW; O, P, courtesy of MNHN-IM.

FIGURE 8. A–I. Eulima sp. 1. A, B. MNRJ 29631. C–I. MNRJ 35215. B, H. Detail of protoconch, frontal view. E. Detail of teleoconch surface. I. Detail of protoconch, apical view. Scale bars: A, C, D= 1.0 mm; B= 200 µm; E, H, I= 100 µm; F, G= 500 µm.