Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 73. (Budapest 1981)

Vörös, A.: A survey of the Rhaetian (Upper Triassic) Bivalvia from Borzavár (Bakony Mts., Hungary)

Material : 104 specimens in different state of preservation. — Locality: Borzavár, Rhaetian grey and yellow limestones. Dimensions : The length and height data of 26 measurable specimens are presented in Fig. 1. Description : The shell is of small size for the genus; moderately inflated. The outline is modioliform to oval (in the smaller specimens); obliquity is about 50°. The straight dorsal margin occupies about one-half of the total length of the shell and passes gradually into the widely arched, rounded posterior margin. The ventral margin has a short straight portion which may be slightly inflected in the larger specimens. The anterior margin strongly bulges. The umbo is almost terminal, lies in the line of the dorsal margin or, in a few cases, slightly emerges above it. The diagonal ridge is not well developed, only its anteroventral slope is marked. On the larger specimens, a shallow sulcus is present between the diagonal ridge and the anterior lobe. The shell surface is ornamented with fine, irregularly spaced growih lines. The shell (particularly its inner layer) shows very thin capillae (fibres) which are radial, or more precisely, always perpendicular to the growth lines. Remarks : The large number of specimens from Borza vár makes possible to interpret this species in a wider sense than the earlier authors have done. Accordingly M. visgnolae, M. adrarae and M. orbicularis figured by MARIANI (I.e.) and DESIO (I.e.) respectively, can be ranged into M.faba. The M. adrarae specimen described and figured by ALASSINAZ (1962) (p.333., pl. XXIV., fig. 4-5) is however different from M. faba by its strongly parabolic posteroventral margin. "Myacites faba''' figured by CAPELLINI (I.e.) are something quite different, probably pleuromyid bivalves. Distribution : Rhaetian of the Northern Limestone Alps, the Southern Alps and the Bakony Mts. (Hungary). Fig. 1. The length and height data of 26 specimens of Modiolus (M.) faba (WINKLER) from Borzavár