Neritilia, MARTENS, 1879

Lozouet, Pierre, 2004, The European Tertiary Neritiliidae (Mollusca, Gastropoda, Neritopsina): indicators of tropical submarine cave environments and freshwater faunas, Zoological Journal of the Linnean Society 140 (4), pp. 447-467 : 448-450

GENUS NERITILIA MARTENS, 1879

Type species (by original designation) Neritina rubida Pease, 1867 ; Recent.

Description: The shell is small, solid, with a relatively flat spire. The protoconch is multispiral tilted relative to the teleoconch coiling axis and ornamented with numerous minute pits. The teleoconch ornament consists principally on growth lines. The inner lip septum is flat and the adaxial margin is straight without teeth; the outer lip is prosocline without teeth.

NERITILIA BISINUATA SP. NOV.

( FIG. 2 )

Etymology: From sinuatus (Latin), sinuous, referring to the shape of the outer lip.

Type specimens: Holotype, coll. Le Renard (MNHN- LR67776A), 2 paratypes, coll. Le Renard (MNHN- LR67776B).

Type locality and horizon: France, Loire-Atlantique, Saffré ‘ Le Bois-Gouët’, Middle Eocene (Lutetian) .

Other material examined: Middle Eocene, France, Loire-Atlantique, Saffré ‘ Le Bois-Gouët’, Middle Eocene (Lutetian), coll. Le Renard, 2 ex. (MNHN- LR6834) .

Measurements (holotype): Height = 1.2 mm; max. width = 1.45 mm.

Description: The shell is minute, solid, very elongate neritiform with a relatively high spire for the group. The protoconch is multispiral, eroded but clearly tilted relative to the teleoconch. Teleoconch whorls up to 1.4 in number, increasing rapidly in size, inflated with a round periphery. The sutural line is gently impressed. The surface of the shell is relatively altered but one can distinguish spiral ridges and sinuous growth lines, which are particularly strong close to the aperture. The semicircular aperture is relatively small and inclined at about 42∞ relative to the teleoconch coiling axis. The outer lip is prosocline and sinuous with two notches, widely bevelled and slightly dilated outward. The inner lip is covered with a smooth, extensive callus; the adaxial margin is straight, without teeth.

Remarks: This very small species is unique within Neritilia because of the presence of well-developed spiral ridges and strong sinuous growth lines. It is also the smallest Neritilia species known.

Figures

Figure 2. Neritilia bisinuata sp. nov. from Bois-Gouët (Middle Eocene). A, apertural view of the holotype (MNHN- LR67776A); B, apical view of a paratype (MNHN-LR67776B), C, apical view of the protoconch; arrow indicates the embryonic shell.