Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 15. 1992. (Budapest, 1992)

Distribution: According to Aimeras (1964), Z. alpina is Hettangian and Sinemurian in age. Vörös (1982) mentioned this species from the Upper Sinemurian and the Ibex Zone (Lower Pliensbachian) of the Bakony Mountains. The species was reported from the Eastern Alps (Hierlatz), the Central Appennines, the Gerecse Mountains and the Bakony Mountains. Zeilleria choffati (HAAS, 1885) (Pl. V, Fig. 3; Text-figs. 31-32) 1889 Waldheimia Choffati HAAS - Geyer: p. 22, pi. 3, figs. 8-13. 1943 Waldheimia choffati HAAS - Vígh: p. 34, pl. 1, fig. 16. 1964 Zeilleria choffati HAAS - Sacchi Vialli: p. 17, pi. 2, figs. 3., 10. Material: 3 complete specimens. Dimensions (mm): Specimen M.91.29. (Text-fig. 31) length: 18.3, width: 14.3, thickness: 10.5. Description - External characters: Medium-sized shell, subtriangular in outline. The sides of triangle are slightly convex, the base is straight. The angle between the lateText-fig 31 - Drawing of ral margins is about ^ The width is signiZeillena choffati ficantly smaller than the length while the thickness is about half of the length. Biconvex form, the valves are quite convex. The maximum width is situated at half of the length, the maximum convexity is at the anterior third. The beak is small and erect. There are two weak beak ridges on the pedicle valve, running to half of the length. The lateral commissures are straight and form a slightly elevated edge. The anterior commissure is straight or slightly uniplicate. The shell surface is weakly capillate. Internal characters (Text-fig. 32). The dental plates are parallel. The delthyrial cavity is rectangular in cross-section. Later the dental plates become divergent and the delthyrial cavity is trapezoidal in cross-section. The umbonal cavities are relatively large and triangular in cross-section. No pedicle collar has been observed. The hinge plates are narrow, the septalium is deep. The socket is extremely large and wide. The teeth diverge from the dental plates. The teeth are slightly crenulated and there is a large denticulum on its side. The median septum runs to one-third of the length. Most of the loop is missing. Remarks: Some specimens of Z. choffati are similar to the triangular Z. mutabilis. However, the convexity of valves is greater at Z. choffati and the maximum width and the maximum convexity is situated at half of the length, whereas at the Z. mutabilis the maximum width is at the anterior margin, the maximum convexity is at the posterior third. Distribution: According to Aimeras (1964), Z. choffati is Sinemurian in age but its occurrence in the Late Sinemurian is uncertain. The species was reported