Sampling the depth: New data on the Caecidae (Mollusca, Gastropoda) from northeastern Papua New Guinea Author Walter, Angelo Vannozzi Via M. L. Longo 8, 00151 Rome (Italy) ang.vannozzi@gmail.com Author Renda, Walter Via Bologna 18 / A, 87032 Amantea (CS) (Italy) w.renda1@tin.it text Zoosystema 2024 2024-06-07 46 14 327 347 journal article 299020 10.5252/zoosystema2024v46a14 b5619e29-fcbd-4ddc-9231-138300251568 1638-9387 12548683 23D972D0-F573-429C-816B-F42AFF02D0B1 Caecum restrictum n. sp. ( Fig. 4 ) urn:lsid:zoobank.org:act: 73675C26-F3E9-4D3A-A4A9-828A4C35CAC0 TYPE MATERIAL . — Holotype . Papua New Guinea • sh (length 1.9 mm , Fig. 4 A-D); New Ireland , KAVIENG 2014 Stn DW4486; 2°28’S , 149°54’E ; 272-276 m depth ; 5.IX.2014 ; MNHN-IM-2000-38944 . Paratypes . Papua New Guinea • 2 sh worn; same data as for holotype; MNHN-IM-2000-38945 . TYPE LOCALITY . — Pacific Ocean, Papua New Guinea , New Ireland , 2°28’S , 149°54’E ; 272-276 m depth. OTHER MATERIAL EXAMINED . — Papua New Guinea • 1 sh; Off Bougainville ; 5°02’S , 154°29’E ; 615-632 m depth ; 13.X.2010 ; BIOPAPUA Stn DW3754; MNHN . DISTRIBUTION . — Known from northeastern PNG (western New Ireland and eastern Bougainville Island). ETYMOLOGY . — The specific epithet is derived from the Latin adjective restrictus (restricted) to indicate the adapically constricted tube. The epithet alludes also to the restricted distribution of the species. DESCRIPTION Shell small for the genus, tubular, smooth, colourless, semitransparent. Protoconch unknown. Teleoconch tubular, arched, almost smooth. Early teleoconch unknown. Adult shell tubular, cylindrical, clearly tapering close to the apex, straight in ventral view. Surface smooth. Microsculpture of evenly-spaced growth lines defining fine flat rings visible in the abapical half. Macula none detected. Aperture preceded by a strong varix-like swelling crossed by coarse growth lines, then contracting and ending with a fine reflected lip. Septum low dome shaped without mucro, slightly recessed below the cutting plane. Traces of temporary septum visible at the boundary of the septum with the tube. Periostracum none detected. Operculum and soft parts unknown. Holotype : length 1.9 mm , max diam 0.4 mm , min diam 0.3 mm . FIG . 4. — Caecum restrictum n. sp. : A -D , holotype MNHN-IM-2000-38944; E , F , paratypes MNHN-IM-2000-38945 from type locality; G , specimen from Stn DW3754 (MNHN). Scale bar: 1 mm, details not to scale. REMARKS This species is known from a few specimens. The two paratypes , originating from the type locality, although smaller and worn, display the characters shown by the holotype and have been designated accordingly. Caecum restrictum n. sp. can be compared with C. succineum de Folin, 1880 , C. biomaglo Vannozzi, 2023 and C. iricolor Vannozzi, 2023 , all of them showing smooth shells with dome-shaped septum without mucro. Caecum succineum , described from Cape York, NE Australia , but recorded throughout the IWP, is smaller and slenderer, is not clearly constricted close to the apex and shows several rings close to the aperture. Caecum biomaglo , described from Mayotte , is larger and stouter and shows a longitudinal microsculpture. Caecum iricolor , also described from Mayotte , is larger and shows a slightly twisted iridescent tube, sometimes with longitudinal grooves.