Caecum incisum Vannozzi & Pizzini & Raines 2015, sp. n.
Creators: name: Vannozzi, Angelo
name: Pizzini, Mauro
name: Raines, Bret
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Caecidae
Caecum
Caecum incisum

description: Caecum incisum sp. n.
Figs 8A–F, 11, 22L, M, 23L, M, 26C, D
Etymology: From the Latin adjective incisus (incised) due to the presence of collabral incisions that are observed throughout the tube.
Description: Tube cylindrical, evenly arched, smooth without sculpture. Both tube and septum are semitransparent, colourless and glossy.Aperture simple, without any swelling or varix, even and not oblique. Microsculpture comprised of collabral incisions which define flat rings. These incisions, spaced by about 2–3 µm apart and rather regular in young specimens, tend to become irregular in adults.This feature causes the appearance of the shells, glossy and shining in the former, to become milky and opaque in the latter. Septum smooth, dome-shaped, with an ear-like mucro rotated toward the right by about 45°.The septum shows some more or less parallel grooves arranged like waves coming from the tip of the mucro. In terms of both curvature of the tube and shape of the aperture juveniles are quite similar to the adults, and are distinguished by the smaller diameter and the more regular microsculpture. Periostracum colourless, dull. Larval stage and operculum unknown.
Length: 1.6–1.8 mm.
Type locality: SOUTH AFRICA: Western Cape: Knysna, Gericke Point, Sedgefield.
Holotype (Figs 8A–C, 22L, 23L): SOUTH AFRICA: Western Cape: sh, Walker’s Point, W of Knysna, leg. J.P. Marais iii.1991 (NMSA S3728 / T3355), length 1.69 mm, min. diam. (posterior end) 0.29 mm, diam. in the middle of the tube 0.33 mm, max. diam. (apertural end) 0.36 mm.
Paratypes: SOUTH AFRICA: Western Cape: 4 sh, same data as holotype (NMSA W9660 / T3356); 8 sh, Knysna, Gericke Point, Sedgefield (NMSA W9661 / T3357); KwaZulu-Natal: 1 sh, Aliwal Shoal, - 9–18 m, dived D. Herbert 21.xii.1986 (NMSA D5269 / T3881); 1 sh (juv), Aliwal Shoal, off Umkomaas area, - 27 m, SCUBA, i.1988 (JPM).
Additional material examined: SOUTH AFRICA: Eastern Cape: 2 sh (1 broken), Mzamba, near Natal border, vii.1976 (JPM 2119); KwaZulu-Natal: 1 sh (lost), Aliwal Shoal (off Umkomaas), - 27 m, silt from between rocks (NMSA E1670); 1 lv, Landers Reef, off Scottburgh Area, - 45 m, SCUBA, iv.1988 (JPM).
Comparative material examined: C. sinuatum de Folin, 1879, BORNEO, syntype (MNHN-IM-2000-27585); C. inhacaense Albano & Pizzini, 2011, MOZAMBIQUE: Inhaca I., holotype (MZB 15000).
Distribution: Southern and eastern coasts of South Africa from Knysna to Aliwal Shoal (Fig. 11).
Remarks: The microsculpture exhibited by C. incisum is unique among South African Caecum species. This kind of microsculpture is shown by C. sinuatum de Folin, 1867 described from Borneo. However, de Folin’s species is quite different from C. incisum, showing a very slender and slightly arched tube, a different shape of the septum and a strong constriction before the aperture. Caecum incisum occurs sympatrically with C. austrafricanum sp. n., C. intortum sp. n. and C. inhacaense, from which it can be distinguished by the even curvature of the tube, the lack of apertural swelling, the presence of incised growth lines defining flat rings throughout the tube, the lack of the macula and the different shape of the mucro.
description: Published as part of Vannozzi, Angelo, Pizzini, Mauro & Raines, Bret, 2015, Revision of South African Caecidae (Mollusca: Gastropoda), pp. 99 in African Invertebrates 56 (1) on pages 109-111, DOI: 10.5733/afin.056.0109, http://zenodo.org/record/7661863