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)

into ridges. Toward the peristome the ridges are accompanied by increasingly stronger nodes on the keels. The oter side shows only fine growth-lines, with a few faint, broad spiral thread. Embryonal shape and sculpture — The nucleus and the first whorl slightly raised on the spiral side, then the characteristic adult coiling appears. The embryonal shell is completely smooth. Because of the lack of the sculpture, its size can only be estimated as about 2.5 whorl. Remarks — The available stratigraphically oldest (Upper Sinemurian) and jungest (Davoei Zone) specimens show marked differences, which are represented as refinement and weakening of the sculpture. Arriving in Davoei times, the transversal bars become narrower and attain 2 or 3 times greater number per whorls. The ridges and the nodes of the last whorl are less marked and appear rather as weak undulations. The identification of the adult specimens do not present difficulties. This species, having a characteristic, strong sculpture on the last whorl, is easily distinguished from the similarly sized other species. On the last two whorls of Discohelix miocarinata sp. n. the keels become rounded and the carinae become smooth. On the other hand, juvenile specimens are rather hard to distinguish. The adult specimens differ from D. levis WENDT, 1968, because this latter has smooth keels on its last whorls and a peristome, which is reinforced outward by an inner varix. In this case the identification of the juvenile specimens is problematic, too. The young specimens of D. acarinata sp. n. with their rounded keels without carinae can be easily distinguished from D. excavata. From D. excavata specimens mentioned by earlier authors those North African forms described by DARESTE DE LA CHAVANNE (1920) differ from the specimens of the Bakony Mountains (and from the other described specimens). In the North African forms the strong nodes appear much earlier (1 or 2 whorls). Distribution — Eastern Alps: Austria, Hierlatz limestone; Vedana, Middle Liassic; — Eastern Sicily, "Terebratula aspasia zone"; Eastern Atlas, Middle Liassic; Bakony Mountains: Sümeg, ? Upper Sinemurian; Kericser, beds with mixed Obtusum to Ibex Zone fauna — Davoei Zone; Lókúti-domb, Davoei Zone; Kávástető, Davoei Zone; ? Kisnyerges-árok, Ibex Zone. Discohelix inornata sp. n. (Plate I: figs. 6-7; Fig. 6c) Holotypus : Plate I: fig. 6. — Stratum typicum: Hierlatz-type, fissure-filling limestone — Locus typicus: Sümeg, Mogyorósdomb — Derivatio nominis: inornatus -• without sculpture. Measurements: D H S H/D H/S A U Plate I: fig. 6 29.1 7.2 6.8 0.25 1.06 216° 144° Plate I: fig. 7 17.7 5.6 3.5 0.32 1.60 Material —Three specimens from the same locality, all are fragmentary, with strongly recrystallized shell, but the fragments can be completed with each other. Diagnosis — Dextral form with concave spire, keels without carinae, peristome trumpetlike, shell smooth, except growth-lines. Shape — The shell is biconcave, with nearly bilateral symmetry. The keels, which are somewhat more distinct on the juvenile whorls, do not have carinae. The surface of the whorls is convex, more slightly on the spiral and umbilical than the outer side. The trumpet-like peristome do not show thickening. Sculpture — On the shell only the fine growth-lines are visible. These are uniform, without any periodicity with growth. Embryonal shape and sculpture — The embryonal whorls can be studied in sections, and show slight raising on the spiral side. Remarks — The characteristic shape, dimensions and "sculpture" make this species easily distinguishable. Distribution — Bakony Mountains: Sümeg, ? Upper Sinemurian Discohelix miocarinata sp. n. (Plate I: figs. 8-9; Fig. 6b) Holotypus : Plate I: fig. 8. — Locus typicus: Lókút, Kericser — Stratum typicum: Hierlatz-type limestone — Derivatio nominis: less carinated (last whorl without carinae). Measurements: D H S H/D H/S A U Plate I : figs. 8-9 19.8 7.9 5.1 0.40 1.55 229° 131°