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

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

lateral wings (Fig. 3). The beak is moderate in size, straight. The pedicle opening is submesothyridid, with well-developed delthydial plates. Internal characters (Fig. 4) : Pedicle valve : Widely set, subparallel, slightly dorsally divergent and shorter dental plates divide the subquadrate delthyrial cavity and the narrow umbonal cavities. No pedicle collar has been observed. The hinge teeth are strong and deeply inserted in the sockets. Moderate, blunt denticula were ascertained. Brachial valve: The hinge plates are horizontal, demarkated from the inner socket ridge by a groove. The sockets are deep, the outer socket ridges are markedly high and straight. The shallow V-shaped septalium is supported by a relatively long dorsal median septum, which persists almost to the plane of articulation. The crura are of radulifer type. Remarks: While describing "Rhynchonella altaplecta", the so common species of the fauna of Felsőörs, BÖCKH (1873) held in his hands a specimen representing another species, vivida. Furthermore, one of his figured specimens belongs to this one. BÖCKH himself noted and mentioned the differences, e.g. in the character of the beak. BITTNER (1890) pointed out that the species described by BÖCKH consists of two forms. He named the newly segregated one as vivida, and treated it as the variety of "Rhynchonella decurtata"

. He also figured a specimen from Köveskál (which shows great resemblance to the one figured in the present paper) and named it as vivida excavata. The diagnostic features which allow one to distinguish it from Caucasorhynchia altaplecta are the straight beak, the ventrally curved lateral commissure and the ventrally projected wings. GAETANI (1966) provisionally attributed this species to his newly defined genus Decurtella. SIBLIK (1971a) also considered this species to belong to Decurtella, but later DAGYS (1974) included it in his new genus Volirhynchia. SIBLIIK accepted it in his paper of 1983. The internal characters of vivida shows great resemblance to those of the genus Volirhynchia diagnosed by DAGYS. The serial sections are closely similar to that of Volirhynchia volitans, the type species of the genus (DAGYS, op. cit. p. 105.) Distribution: The species seems to be confined to the Anisian. Its occurrences were reported from various localities in the Southern Alps, Eastern Alps, West Carpathians and the Dinarids. 1890 Rhynchonella Tommasii sp. n. — BITTNER: p. 53, fig. 1890 Rhynchonella decurtata GIR. var vivida tumescens — BITTNER: p. 11, pi. 37: fig. 16. 1902 Rhynchonella Tommasii BITTN. — BITTNER: p. 531, pi. 21: fig. 14. Material: 66 specimens for Aszófő, where this species is a very characteristic element of the fauna of the "Recoaro-type" limestone. Most of them are incomplete or disarticulated valves, others are recrystellized with sparry calcite. Only four of them are well-preserved and complete specimens. Two specimens were found at Köveskál. Dimension: The following list shows the measured data of six characteristic specimens. No. 1 originated from Köveskál, Nos 2-6 are from Aszófő. Description — External characters: Medium to large shell, triangular in outline, slightly rounded at the anterio-lateral corner. Biconvex at an early stage of growth, but later the pedicle valve becomes rather flat and a sinus developes on it. The maximum width and thickness are at the anterior third of the length. The angle between the lateral margins is about 110°. The anterior commissure is uniplicate, the dorsal fold occupies the central third of the anterior front. The fold is usually as high as wide. The ventral sinus is V-shaped. The posterior part of the shell is smooth, but anteriorly from about the posterior third costae develop. The originally blunt costae become higher, sharper and trigonal in cross-section toward the anterior margin. Usually there are 3 costae in the dorsal fold, 2 in the central sinus and 2 to 5 on the lateral flanks. The beak is moderate in size, triangular and erect, with a hypothyridid pedicle opening on it. Internal characters (Fig. 5): Pedicle valve: The dor so-ventrally elongated, rounded subquadrate delthyrial cavity is located between the subparallel, ventrally shorter dental plates. The umbonal Volirhvnchia tommasi (BITTNER, 1890) (Plate 1: figs 1-2; Fig. 5) Length Width Thickness 12 3 4 11.7 11.9 16.2 13.5 16.5 14.9 20.8 15.9 8.7 9.1 12.1 7.2 5 6 13.0 11.2 15.1 13.8 9.0 7.7