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Subgenus Janua (Dexiospira) Caullery & Mesnil, 1897
Janua (Dexiospira) palaeoforaminosa (Jäger, 2005)
Pl. 6, figs. 13, 14.
Description – Very small, diameter of spiral up to 2.2 mm; dextral, which means that the spiral is coiled anti-clockwise when viewed from above. Three keels occur; these may be smooth, undulate or denticulate. Rarely, rows of granules are present instead of keels. Many specimens larger than 1.5 mm have three longitudinal rows of small pores; two rows between the keels, and one between the outer keel and the base. These outer pores are in contact with the cells at the base which are present only in specimens which have pores. Peristomes may be present. The operculum has a brood chamber.
Remarks – This species was named ‘Spirorbidae, coiled dextral’ and ‘Neodexiospira n. sp.’ by Jäger (1988), and is perhaps identical with ‘Spirorbidae indet.’ of Jäger (1987).
Distribution – Kunrade limestone facies (equivalents of Lanaye to Gronsveld members) and Emael to Meerssen members in the main Maastricht ‘tuffaceous chalk facies’. Relatively common in the Meerssen Member. The total known range is early Maastrichtian (obtusa Zone)(?); late Maastrichtian.