Caecum sepimentum de Folin, 1868

Walter, Angelo Vannozzi & Renda, Walter, 2024, Sampling the depth: New data on the Caecidae (Mollusca, Gastropoda) from northeastern Papua New Guinea, Zoosystema 46 (14), pp. 327-347 : 330

Caecum sepimentum de Folin, 1868

( Fig. 2 A-D)

Caecum sepimentum de Folin, 1868b: 84 , pl. 6, fig. 7. — Vannozzi 2023: 424 , fig. 2A-C and synonymy therein.

TYPE MATERIAL. — Lectotype. Mauritius • sh; Mauritius ; MNHN-IM-2000-24907 .

Paralectotypes. Mauritius • 20 sh; same data as for lectotype; MNHN-IM-2000-24908 .

TYPE LOCALITY. — Indian Ocean, Mauritius.

MATERIAL EXAMINED.— Papua New Guinea • 1 sh; Vitu Islands ; 4°37’S, 149°27’E; 615-647 m depth; 27.IX.2010; BIOPAPUA Stn DW3680; MNHN • 4 sh; Off Bougainville; 5°02’S, 154°29’E; 615-632 m depth; 13.X.2010; BIOPAPUA Stn DW3754; MNHN • 8 sh (3 juv); New Ireland; 2°44’S, 150°35’E; 240-305 m depth; 3.IX.2014; KAVIENG 2014 Stn DW4463; MNHN • 3 sh; New Ireland; 2°43’S, 150°36’E; 140-214 m depth; 3.IX.2014; KAVIENG 2014 Stn DW4464; MNHN • 2 sh; New Ireland; 2°43’S, 150°36’E; 90-228 m depth; 3.IX.2014; KAVIENG 2014 Stn DW4465; MNHN • 7 sh (3 juv); New Ireland; 2°45’S, 150°37’E; 163-358 m depth; 3.IX.2014; KAVIENG 2014 Stn DW4470; MNHN • 7 sh (4 juv); New Ireland; 2°28’S, 149°54’E; 272- 276 m depth; 5.IX.2014; KAVIENG 2014 Stn DW4486; MNHN. Philippines • 5 sh; Mactan, Punta Engano ; beached; coll. WR .

DISTRIBUTION.— The whole IWP. From the east coast of Africa (Red Sea to eastern South Africa) to Maldives, Papua New Guinea, Philippines, Japan, Australia, New Caledonia, French Polynesia, Hawaii ( Kay 1979; Lightfoot 1992a; Hasegawa 2000; Albano & Pizzini 2011; Pizzini & Raines 2011; Pizzini et al. 2013; Vannozzi et al. 2015; Vannozzi 2017, 2019b, 2023; Blatterer 2019; unpublished data). Allochthonous to the Mediterranean Sea ( Pagli 2009; Ovalis & Mifsud 2014).

DIAGNOSIS. — Shell of average size for the genus, colourless or creamy, often with darker blotches. Protoconch planorbid, multispiral of c. 2 whorls. Teleoconch tubular, arched, with strong collabral rings. Early teleoconch conical, rings increasing in strength during the growth. Adult shell subcylindrical, evenly arched. Sculpture of c. 20 strong rings with a somewhat subtriangular outline. Aperture preceded by a swelling, ending with several concentric small rings. Microsculpture of fine longitudinal threads. Septum almost flat without mucro, lying below the cutting plane. Periostracum brownish. Operculum thick, terraced. Animal described by Vannozzi (2019b). Adult shell length c. 2.5 mm, protoconch size 375 µm.

REMARKS All deep-water (90-647 m depth) examined specimens are worn, confirming that this species is exclusive to shallow-water habitats. Freshly-collected specimens, known only from shallow water, often show a colour pattern of brown blotches ( Fig. 2C, D ).

Figures

FIG. 2. — Caecum Fleming, 1813 species from deep-water stations from northeastern PNG: A, B, C. sepimentum de Folin, 1868 from Stn DW4463 (B: juvenile); C, D, C. sepimentum from Mactan, Philippines, beached (coll. WR); E-H, C. vertebrale Hedley, 1899 from Stn DW3754; I, J, C. japonicum (Habe, 1978) from Stn. DW4464; K, L, C. japonicum from Stn DW4463 (L, juvenile); M, C. inflatulum Vannozzi, 2017 from Stn DW4463; N, C. inflatulum from Kotok, Indonesia, beached (coll. WR). Scale bar: 1 mm, details not to scale.