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

Description - External characters: Medium-sized to large shell, circular in outline but almost straight at the anterior margin. The angle between the lateral margins is about 85°. The width is nearly equal to the length while the thickness is two-thirds of the length. Biconvex form, the convexity of valves is equal. The maximum width is situated at half of the length while the maximum convexity is at the posterior third. The beak is mediumsized and erect. There are two strong beak ridges on the pedicle valve running to the Text-fig. 33 - Drawing of anterior margin. There are two less deveZeilkria aff. venusta loped beak ridges on the brachial valve as well. The lateral margins are straight, curved dorsally only at the umbones. The lateral commissures run in the middle of the planareas. The lateral and the anterior margins slightly rise from the surface of shell. The shell is "box-like" in appearance. Text-fig. 34 - Transverse serial sections of Zeilleria aff. venusta