Bithyniidae, Gray, 1857

Frolov, Pavel D., Danukalova, Guzel A. & Osipova, Eugenia M., 2018, Late Miocene molluscs of the Morskaya 2 site (Azov Sea region, Russia), Palaeontologia Electronica (a 20) 23 (1), pp. 1-32 : 14

Bithyniidae indet.

Figure 5.9 -10

Material. 78 specimens from layer 3.

Description. Operculum is oval with concentric growth lines, thin (L is 3.0-3.3; W is 2.0- 2.6 mm) or thickened (L is 4.1-5.0 mm; W is 3.0- 3.3 mm).

Variability. Appears in the shape of opercula: some of them are flat and oval ( Figure 5.9 ), while others have the shape of a truncated cone with an oval base ( Figure 5.10 ).

Remarks. The two varieties of opercula can belong to different species, and possibly to different genera of the family Bithyniidae , but because no special studies have been conducted on this subject, their systematic identification is impossible.

Figures

FIGURE 5. Assemblage of the Maeotian freshwater molluscs (layer 3). 1, Borysthenia cf. pronaticina (Lindholm, 1932). 2-3, Lithoglyphus acutus Cobălcescu, 1883; 2, smooth shell; 3, shell with keel. 4, Viviparus cf. karaganicus Volkova, 1939. 5, Viviparus cf. maeoticus (Bogachev and Shishkina, 1919). 6, Lymnaea sp. 7, Sphaerium rivicola Lamarck, 1818. 8, Gyraulus cf. acronicus (Ferrussac, 1807). 9-10, Bithyniidae, opercula.