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)

shown on the figure are repeated regularly, and possibly mark daily growth periods. Slightly irregular transverse ribs or riblets, corresponding to these bars, were recognised on the shell of Pentagonodiscus angustus. Two of this riblets are separated frequently by "parabolic growth-lines" independent of spines. This "parabolic growth-lines" marks only that the spiral lines do not lit to the lines of the previous riblet. This latter type occurs mainly near the real "parabolic growth-lines", on its adorai shell portion. This suggests a complete soft part rearrangement for the time its formation. Facies-dependence and mode of life of Discohelix and Pentagonodiscus — Figs. 1A-B show the distribution of the specimens by facies-types. Prominent specimen number values generally mark preferred facies. In the cases of restricted specimen numbers, the occurrence in the preferred facies is most probable. All the Pentagonodiscus Fig. 2. A: Model for the formation of the Jurassic facies-types of the Bakony Mountains. — B: Distribution of Discohelix and Pentagonodiscus species in the facies-types, 1 = D. inornata, 2 = D. cf. ornata, 3 = D. miocarinata, 4 — D. excavata, 5 = D. orbis, 6 = D. acarinata, 1 = ID. cotswoldiae, 8 = P. réussii, 9 = P. initiopentagonatus, 10 = P. angustus