Caecum sp.

Vannozzi, Angelo, 2023, The Caecidae from BIOMAGLO Expedition in the Mayotte-Glorieuses area (Mollusca, Gastropoda), Zoosystema 45 (12), pp. 421-434 : 428-429

Caecum sp.

( Figs 2N ; 4E ; 5D )

MATERIAL EXAMINED. — Mayotte • 1 dd; Mozambique Channel , W Mayotte, BIOMAGLO Stn DW4847; 12°41’S, 44°57’E; 738- 763 m depth; 30.I.2017; MNHN .

DESCRIPTION

Shell of average size for the genus, smooth, colourless, semitransparent, iridescent. Tube cylindrical, not twisted and gradually tapering toward the apex. Surface smooth crossed by fine growth lines only. Macula absent. Aperture preceded by a strong varix-like swelling, somewhat inclined toward the left side. Septum narrow, dome shaped, slightly asymmetrical in dorso-ventral direction but without any visible mucro. Length 2.4 mm.

REMARKS

This single specimen recalls both Caecum biomaglo n. sp. and C. iricolor n. sp. due to the smooth, iridescent tube with similar size. However, it is clearly distinguished by the more protruding septum, the stronger varix-like swelling and the smooth surface without longitudinal microsculpture.Additional material is necessary to clarify the identity of this specimen.

A loose operculum was found in the capsule containing this sample, possibly belonging to this specimen. In fact, this operculum is corneous, circular, thin, flat on both sides and with compatible size, whereas the specimens of other species found in the same station are very worn, as C. hyalinum Vannozzi, 2022 , or much larger, as Mauroceras kajiyamai , or are known to have a differently shaped operculum, i.e., thick with stepped profile in C. sepimentum or hat-shaped in C. cooki ( Pizzini et al. 2013: fig. 19).

Figures

FIG. 2. — Side and ventral views of Caecum Fleming, 1813 species from BIOMAGLO Expedition: A-C, C. sepimentum de Folin, 1868 from Stn DW4848; A, B, specimens with preserved colour pattern; C, juv.; D, C. succineum de Folin, 1880 from Stn DW4854; E-H, C. iricolor n. sp.; E, F, holotype MNHN- IM-2000-38696, length 2.33 mm; G, H, paratype MNHN-IM-2000-38697 from type locality; I-M, C. biomaglo n. sp.; I, J, holotype MNHN-IM-2000-38700, length 2.46 mm; K, L, paratype MNHN-IM-2000-38701 from type locality; M, paratype from Stn DW4854 MNHN-IM-2000-38702; N, Caecum sp. from Stn DW4847, length 2.4 mm. Scale bar: 1 mm.

FIG. 4. — Detail of the septum (right side) of Caecum Fleming, 1813 species: A, B, C. iricolor n. sp.; A, holotype MNHN-IM-2000-38696; B, paratype MNHN- IM-2000-38697; C, D, C. biomaglo n. sp.; C, holotype MNHN-IM-2000-38700; D, paratype MNHN-IM-2000-38701; E, C. sp. from Stn DW4847; F, C. hyalinum Vannozzi, 2022 from Stn DW4847. Scale bar: 100 µm.

FIG. 5. — Detail of the aperture (right side) of Caecum Fleming, 1813 species: A, B, C. iricolor n. sp.; A, holotype MNHN-IM-2000-38696; B, paratype MNHN- IM-2000-38697; C, C. biomaglo n. sp., holotype MNHN-IM-2000-38700; D, Caecum sp. from Stn DW4847. Scale bar: 100 µm.