Mazandaran Province, Nowshahr city, pond near Caspian Sea, 51°31'E, 36°38'N, 18 June 2005.

(ZMH 79369):Shell height 8.0 mm, width 5.0 mm.

Named after the region where the species was collected.

The horn-coloured shell is conical with 5.5 whorls, which are slightly convex with a clear suture and an acute apex. The umbilicus is closed. The aperture is ovate, angled at the top. The margin of the aperture is, from lateral view, sinuated. The surface bears a lattice structure. Shell height 8.0 mm, width 5.0 mm, aperture height 3.6 mm.

The new species resembles Bithynia tentaculata but differs from it by the following features: (i) the operculum is more angled (Fig. 7c), (ii) the whorls are more convex (Fig. 7a–b), and (iii) the surface has longitudinal and transverse striae (Fig. 7d).

Planorbis carinatus, Anisus sp., Valvata cristata, Valvata nowshahrensis sp. n., Hippeutis complanatus.

Probably this species formerly (e.g., Mansoorian 2000) was confused with Bithynia tentaculata. Because we had only an empty shell of this species, we do not know if it belongs to the genus Bithynia or Pseudobithynia, so our generic assignment is tentative. To address this question, anatomical studies of more specimens are necessary.