Diameter of holotype 1.72 mm.

Type material Holotype SMNH 4343, two paratypes in MNHN. Type locality. Corsica, outer part ofBaie de Calvi, 90-120 m, on a bottom largely consisting of old Posidonia fibres,
Material examined. The types and —central part of the Tuscan Archipelago, in an amphora from 300-400 m depth, 20 shs; —off Capraia, Tuscan Archipelago, 200 m, 1 shell, MNHN.
Description. Shell small, transparent, fragile. Planorbis-like. Larval shell of 1.3 distinctly hypertrophic whorls, initial part weakly sculptured with irregular, sharp, very short, randomly dispersed ridges. Teleoconch of 2.3 whorls, sculptured only with weak incremental lines. Whorls just barely touching; suture consequently deep and channeled. Cross-section of whorls rounded, adapical side slightly flattened and sloping outwards from centre. Whorls coiled with upper surface at approximately same level and with an overlap over preceding whorl, measured on underside, corresponding to 1/5 -1/6 of width of earlier whorl. Width of umbilicus about 40% of total diameter. Dimensions. Diameter of holotype 1.72 mm. Radula. As described above for the family.
Soft parts. Foot very short and broad, posteriorly blunt, anteriorly shallowly bifid, with anterior corners drawn out to a width 60 % wider than foot, depth of indentation about 1/4 of width when crawling. Tentacles long and slender with very small eyes situated in centre of the bases. Snout short and conical. Two pallial tentacles situated close together at right corner of pallial cavity, anterior one three times longer than posterior one. Two white, pigmented mantle organs situated centrally in pallial skirt, anterior one larger. Periostracum thin, slightly lamellose, brownish.
Remarks. The two new species of Xylodiscula are quite difficult to distinguish, but Xylodiscula boucheti has a smaller umbilicus, diameter about 30-33% of the diameter of the shell, while that of X.lens corresponds to 40%. This difference is easily seen in a basal view when the two species are placed beside each other. The difference is, however, less obvious in young specimens.

Corsica, outer part of Baie de Calvi, 90-120 m. Also central part of the Tuscan Archipelago, in an amphora from 300-400 m depth.