Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 80. (Budapest 1988)

Pálfy, J.: Middle Triassic rhynchonellids from the Balaton Highland (Transdanubian Central Range, Hungary)

The beak is medium-sized, suberect. It swells from the posterior part of the pedicle valve, but anteriorly graudally disappears, since the dorsal sulcus grows. Internal characters : There were no adequate specimen available for serial sectioning due to the recrystallization and the paucity of the material. Remarks — The identification of this species remains uncertain due to the scarcity of figured descriptions known by the author. BITTNER (1890) presented two specimens slightly different in outlook, what may be explained by the different stages of growth. This is also the main cause of the differences in the form of the specimens treated here. DAGYS (1974) attributed this species to the genus Volirhynchia which was questioned by SIBLIK (1983). Being no other generic attribution suggested, here I preserve DAGYS' point of view. Nevertheless it is doubtful, since projectifrons has smooth valves, whereas all the other species of Volirhynchia have costate anterior part. Serial sectioning can help to resolve this problem, if subsequent collectings provide more available material. SIBLIK (1983) assumed that projectifrons and "RhynchonellcC protractifrons (BITTNER, 1890) are synonymous. This is highly probable, since our specimens from Felsőörs shows greater resemblance to the latter one of BITTNER'S species, while common features suggest it is conspecific with the specimens from Aszófő. It would be advisable to preserve the name projectifrons, because the original figures of protractifrons hint a rather juvenile form. In the sense of SALOMON (1895), Rhynchonella ottomana (BITTNER, 1890) and Rhynchonella generosa (BITTNER, 1890) also belong to "Rhynchonella protractifrons". This seems to be an obvious mistake. Distribution: Beside the Balaton Highland this species is known from the Anisian formations of the Southern Alps and Eastern Alps (Schreyeralm). Genus Costirhj nchopsis (DAGYS, 1974) Costirhvnchopsis mentzeli (BUCH, 1843) (Plate 2: fig. 1; Fig. 7) 1890 Rhynchonella Mentzelii BUCH spec. — BITTNER: p. 12, pi. 32: figs 14-16. 1902 Rhynchonella Mentzelii BUCH spec. — BITTNER: p. 502, 503, pi. 21 : figs 8-12. 1935 Rhnnchonella Mentzelii BUCH — MILOSAVLJEVIÓ: p. 271, p\. 1: fig. 2. 1912 Rhynchonella Mentzelii BUCH — DE TONI: p. 339, pl. 1 : fig. 11. 1937 Rhynchonella Mentzelii v. BUCH sp. — ASSMANN: p. 31, pi. 7: fig. 12. 1949 Rhynchonella Mentzelii BUCH — BESICH: p. Ill, pl. 1 : fig. 8. 1971 "Rhynchonella" mentzeli (Buch) — SIBLIK: p. 176, pi. 19: fig. 1, pi. 20: fig. 9, fig. 12. Material: 63 specimens from Aszófő and 2 specimens from Köveskál, the bulk of which consists of incomplete or disarticulated shells. Dimensions: The following table shows the data measured on five specimens from Aszófő representing the average. 1 2 3 4 5 Length 8.0 7.9 7.7 84 8.8 Width 8.7 9.1 9.4 9.3 10.7 Thickness 4.! 4.6 3.4 6.5 3.9 Description — External characters : Usually small, sometimes medium-sized shell. The brachial valve is oval, the pedicle one is subtrigonal in outline. Both valves are equally convex. The flat biconvex character is more common, but in some cases the lateral view has a rather globose appearance. The maximum width can be measured at the anterior third, the maximum thickness is at half length. The anterior commissure is more often uniplicate than rectimarginate. A low, wide, gently arched fold may develop only in the later stage of growth. Both valves are fully covered by the sharp, dense costation. The number of costae is 14-15, 4-6 of which are placed in the central fold. The straight costae start from the beak and run slightly divergently to the anterior end without bifurca-