Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 71. (Budapest 1979)

Szabó, J.: Lower and Middle Jurassic Gastropods from the Bakony Mountains (Hungary). Part I.: Euomphalidae (Archaeogastropoda)

Material — Three relatively well-preserwed, shelly specimens. Diagnosis — Spire concave, keels are carinate only on the juvenile shell, protoconch smooth, shell is ornamented only with bars. Shape •— Dextral, discoidal form with a spire less concave than the umbilicus. The crosssection of the juvenile whorls is straight, on both the spiral and umbilical side, but is slightly convex on the last two whorls. The outer side is slightly arched throughout the shell. On the last two whorls, after a gradual transition, the keels become rounded, without carinae. Peristome is unknown. Sculpture — The spiral sculpture of the juvenile whorls consists of carinae on the keels and some faint spiral threads on the outer side. Transverse sculpture appears only on the spiral and umbilical sides, as tiny roof-tile-like bars. On the juvenile whorls each of these bars are accompanied with small nodes on the carinae of the keels. After the keels the bars fade out rapidly on the outer side. Embryonal shape and sculpture — The embryonal shell is smooth, but has distinct keels after the first whorl. The characteristic sculpture of the adult shell onsets after the third whorl. Remarks — The adult specimens can be easily distingusihed from the similarly-sized D. excavata, because in this latter a marked sculpture appears on the last whorl. In D. excavata the keels remain carinate, with apperance of stronger nodes, and the bars in the sculpture are replaced by strong, widely-space ridges. It is possible, that juvenile whorls can be distinguished on their dimmensions, but this procedure needs larger material. D. acarinata sp. n. is also distinguished in having rounded, uncarinate keels after the embryonal whorls. Distribution — Bakony Mountains: Lókút, Kericser, beds with mixed Obtusum to Ibex Zone fauna; traces of redeposition, perhaps older than Ibex Zone. Discohelix acarinata sp. n. (Plate I: fig. 10, Plate II: fig. 12; Fig. 6a) Holotypus : Plate I: fig. 10. — Locus typicus: Hárskút, Közöskúti-árok — Stratum typicum: red, manganiferous limestone -— Derivatio nominis: without carinae; the teleoconch lacks Fig. 6. Cross-sections of the species: a = Discohelix acarinata, b = D. miocarinata, c = D. inornata, d = D. excavata, e = D. orbis, f = ?D. cotswoldiae, g = Pentagonodiscus reussii, h = P. initiopentagonatus, i = P. angustus