Figures 3 A–T, 4A–G
Fusus plumbeus Philippi. Gould, 1852: 230, pl. 1, figs. 281, 281a (non Philippi, 1844) in agreement with Cernohorsky, 1977: 109.
Fusus roseus Homb. et Jacq. in Rousseau, 1854: 107, [1848] pl. 25, figs. 4–5, non Anton, 1839.
Euthria atrata Smith, 1881: 29, pl. 4, fig. 5.
Fusus (Sipho) scalaris Watson, 1882: 377 (non Lamarck, 1816: 6, pl. 425, fig. 7.)
Fusus (Neptunea) scalaris Watson, 1886: 203, pl. 12, fig. 5.
Trophon candidatus Mabille & Rochebrune in Rochebrune & Mabille, 1889: H.56, pl. 2, fig. 2; Petit, 2010: 49.
Euthria rosea Hombron & Jacquinot. Rochebrune & Mabille, 1889: 59; Strebel, 1905: 616, pl. 21, figs. 1–4; Strebel, 1908: 28; Melvill & Standen, 1912: 355.
Euthria ringei Strebel, 1905: 619, pl. 21, figs. 5, 5a–c.
Probuccinum scalare Thiele, 1912: 263.
Pareuthria rosea (Hombron & Jacquinot). Powell, 1951: 133; Carcelles & Williamson, 1951: 295; Powell, 1960: 148; Dell, 1971: 206;
Pareuthria scalaris (Watson). Powell, 1951: 134; Powell, 1960: 148; Cernohorsky, 1977: 109.
Neptunea scalaris (Watson). Carcelles & Williamson, 1951: 294.
Northia atrata (E. A. Smith). Carcelles & Williamson, 1951: 294.
Paraeuthria (sic) rosea (Hombron & Jacquinot). Fernández, 1967: 140, fig. 6; Castellanos, 1970: 100, pl. 6, 2; Castellanos & Fernández, 1976: 10, fig. 4; Castellanos, 1992: 17, pl. 1, fig. 10.
Pareuthria powelli Cernohorsky, 1977: 109, fig. 5, new name pro Fusus roseus Hombron & Jacquinot non Anton, 1839; Pastorino, 1995: 10, pl. 2, fig. 12; Reid & Osorio, 2000: 127, fig. 4D; Zelaya in Häussermann & Försterra, 2009: 497, figs.; Forcelli, 2000: 97, fig.
Paraeuthria ringei (Strebel, 1905). Castellanos, 1992: 14, pl. 1, figs. 1, 2, (non pl. 4, fig. 35 = Meteuthria batialis n. sp.).
Paraeuthria michaelseni (Strebel, 1905). Castellanos, 1992: 16, pl. 1, fig. 3 (non Strebel, 1905).
Pareuthria powelli (Hombron & Jacquinot, 1854). Linse, 2002: 105, pl. 14, figs. 9.1.1–106/108.
Type material. [Euthria atrata] NHMUK 79.10.15–10, 6 syntypes, mostly very worn, 4 of them pagurized; one of these specimens, illustrated here in Figure 3 A–C is designated as lectotype in order to preserve stability of nomenclature in agreement with ICZN article 74; [Fusus scalaris] holotype, NHMUK 1887.2.9.700; [Fusus roseus] 1 syntype, MNHNP 6443; [Euthria ringei] 2 syntypes, ZMH 3132 (ex SE6176 (153) and [Trophon candidatus] 1 syntype, MNHNP 1035.
Type locality. [Euthria atrata] Here restricted to Portland Bay, St. Andrews Sound, 10 fms. [18.2 m] depth; [Fusus roseus] “ détroit de Magellan ” [Euthria ringei] Strait de [Le] Maire and Puerto Gallegos (= Río Gallegos), 51°38'00"S, 69°13'00"W; [Trophon candidatus] “ Baie Orange, sud du cap Horn ”, 5–120 m depth; [Fusus scalaris] CHALLENGER station 305a, 47°48'30"S, 70°47'W, N. W. Patagonia, 125 fms. [228.6 m] depth (Chile).
Description. Shell medium sized, up to 22 mm in height, fusiform, of six convex whorls; protoconch (Fig. 4 F) of 2 ½ convex whorls, translucent, smooth, transition to teleoconch well defined; suture impressed, aperture oval, labrum expanded, sharp, with a small, curved subsutural slit; siphonal canal short; parietal callus very thin; axial ornamentation of about 10 to 12 varices, complete in all whorls but the last, where they vanish below middle whorl; some specimens, only with weak varices on the early whorls; spiral ornamentation of about 15 characteristic, regularly spaced striae per whorl, 30 on the last; periostracum absent (?); color typically pinkish, reddish or dark purple, inside creamy white; operculum (Fig. 4 G) brown, ovate, nucleus subterminal.
Radula (Figs 4 A–C) rachiglossate, very similar to P. fuscata, but the cusps of the lateral teeth are more closely spaced in P. atrata, particularly in the juvenile specimens. Linse (2002) mentioned that the radula is also shorter.
Penis (Figs 4 D, E) large, long, subrectangular, flat, generally similar to that of P. f u s c at a. Some minor differences are likely due to the reproductive stage and the reaction to critical point drying method.
Material examined. Argentina: 1 shell, Mar del Plata, 22 m depth, (MACN-In 16880); 2 spms., 1 shell, 40°03’S, 51°00’W, 91.5 m depth, (MACN-In 15687); 1 shell, Punta Norte, Chubut, (MACN-In 9158-5); 4 pagurized shells, 44°16’S, 65°12’W, temperature of water 14°C, 45.75 m depth, Bahia Vera, Chubut, (MACN-In 23744); 15 spms., 15 km south of Caleta Coyle, Santa Cruz, (MACN-In 1033); 19 shells, 43°18’0.04”S, 64°16’58.8”W, 45–55 m depth, Off Rawson, Chubut, (USNM 894420); 2 shells, 43°27’S, 59°32’W, 145 m depth, (MACN-In 35058); 3 shells, Cabo Blanco, Santa Cruz, (MACN-In 23625); 4 spms., Puerto Deseado, Santa Cruz, (MACN-In 17737-1); 3 shells, 51°46’S, 68°45’W, 22 m depth, (MACN-In 23856-1); 1 shell, 53°32’S, 64°57’W, 119–124 m depth, RV ELTANIN, St. 944, (USNM 870416); 2 shells, 54°04´S, 63°35´W, 247–293 m depth, RV ELTANIN, St. 369, (USNM 870180); 2 spms.,54°27’S, 66°12’W, (USNM 870319); 1 spms., 53°06’S, 67°04’W, 86 m depth, (USNM 898475); 1 spms., 54°26’30”S, 64°53’W, (MACN-In 25033); 4 pagurized, 54°26’30’S, 64°53’W, 112 m depth, (MACN-In 25030); 9 pagurized, 55°07’S, 66°33’W, 82 m depth, (MACN-In 23937); 1 shell, 55°07’S, 66°33W, 82.35 m depth, (MACN-In 23936); 3 shells, 55°07’S, 66°33’W, 82.35 m depth, (MACN-In 23935); 1 spms., Ushuaia, 36.6 m depth, (MACN-In 29656); 2 shells, Puerto Cook, Isla de los Estados, 33.4 m depth, (MACN-In 22083); 4 shells, Puerto Hoppner, Isla de los Estados, (MACN-In 22545-1); 5 spms., 52°30’S, 67°14’W, (USNM 870540); 3 shells, Observatorio Is., (MACN-In 22583); 1 spm., 53°32’S, 64°57’W, (USNM 870415)
Chile: 8 pagurized, Picton Is., 82.35 m depth, (MACN-In 23985); 4 spms., Punta Arenas, (MACN-In 13121); 4 shells, Lennox Is., 22 m depth, (MACN-In 24912); 6 spms., Punta Arenas, (MACN-In 12370); 5 spms., Punta Arenas, (USNM 36653); 1 shell, Calbuco, (MACN-In 11613); 1 spms., 52°52’S, 75°18’W, 119–329 m depth, (USNM 870103); 53°39’24”S, 2 spms.,70°55’30”W, (USNM 898492); 1 spm., 56°06’S, 66°19’W, (USNM 870395); 2 spms., 53°39’S, 70°55’30”W, (USNM 898490).
Distribution. Off Buenos Aires province to Ushuaia, Tierra del Fuego, Malvinas and Staten Is., Argentina in the Atlantic; Southern Chile, Punta Arenas, to Calbuco (41°S) in the Pacific Ocean.
Remarks. This is a very variable species with a large geographic range. The main variations are in the size and number of axial varices. Also the spiral striae are sometimes worn, rendering an almost smooth pattern as seen on some of the syntypes.
Cernohorsky (1977) considered Fusus scalaris Watson as a synonym of his Pareuthria powelli (new name for Fusus roseus Hombron & Jacquinot, 1854 non Anton, 1838) so he proposed no substitute name for this species despite the homonym with F. scalaris Lamarck, 1816. The type material of Watson’s species is housed at the NHMUK and is illustrated here in figures 3P– R. It was collected by the HMS CHALLENGER expedition at Station 305A (47°48'30"S, 70°47'W), which is obviously incorrect as this point lies in the center of Santa Cruz province, Argentina. It could probably be 74°W instead of 70°W, which is north of Wellington Is., Golfo de Penas, Chile. The material reported by Watson presented some differences such as its white colour, which is usual in dead specimens. Nevertheless, the shell morphology falls within the variation range of P. atrata.