Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 74. (Budapest 1982)

Szabó, J.: Lower and Middle Jurassic Gastropods from the Bakony Mountains (Hungary). Part IV.: Neritacea, Craspedostomatacea, Amberleyacea (Archaeogastropoda)

somewhat thickened by a callus along the inner lip and an external varix at the outer lip. The aperture is rounded less so at the inner lip and more so at the outer one. Ornament : The varices are periodically repeated and crossed by the two carina and numerous spiral cords and lines. Usually, the varices appearing near the suture and becoming strong at the ramp angle, then they run down to the lower suture, or the inner lip on the last whorl. At the intersections with the upper carina, long, hollow spines are sitting, which may be longer than the height of the peristome on the adults, observable only on fortunate breaking surface of the matrix, because the specimens are hardly deliverable owing to the strong ornament. The spines are curved and bear a narrow slit from the aperture to the tip. At the crossing points of the lower carina and the varices, only small nodes are found. Embryonal shape and ornament: The protoconch consists of the nucleus and about 2.5 whorls, with subglobose — low turbiniform outline, without any ornament. Its boundary with the teleoconch is marked by the sudden appearance of the adult form and ornament. Distribution : Bakony Mts., Somhegy: Humphriesianum to Parkinsoni Zone. Remarks : The lower, weaker carina being slightly stronger than a spiral cord on the last whorl, not appearing on the stratigraphically younger specimens. An operculum of the neritopsid type definitely belongs to Neritopsis spinigera sp. n., being the only known neritopsid species on the locality (Plate I: figs. 15—16) Neritopsis veronensis DAL PIAZ, 1912 also bears long spines, but in two rows, and this species has an extremely deep suture, and a dissimilar peristome. Neritopsis spinosa HEBERT & DESLONGCHAMPS, 1860 is ornamented by three rows of spines on three carinae. Family Neritidae RAFINESQUE, 1815 Genus NERITOM A MORRIS, 1849 Neritoma (Neridomus) aff. tethys (GEMMELLARO, G. G., 1878) (Plate II: fig. 1.) aff. ISIS: Neritina tethys GEMMELARO, G. G., p. 326, pi. 27, figs. 40, 42. Measurements: H HL HA W D A Plate II: fig. 1. ~ 6 -5.5 -5 -4.5 -7 Material: A single, damaged and possibly juvenile specimen. Shape : Small, globose shell, with a last whorl nearly completely enveloping the earlier parts. Peristome is rounded, angulate at the suture, its inner lip thick and largely callous. Ornament : Shell smooth with some obscure longitudinal lines on the last whorl, and very fine growth-lines without sinus. Distribution : Bakony Mts., Kericser: Davoei Zone. Remarks : The shape of the specimen is highly similar to that of Neritina tethys GEMM., G.G., but owing to bad preservation and to its certainly juvenile state, the determination is doubtful. Neritoma (Neridomus) sp. (Plate II: figs. 2-3) Measurements: H HL HA W D A Plate IL figs. 2-3 12.5 12 11.5 9.5 14 Material : Two specimens in bad state of preservation. Shape : Dextral, globose, thick-walled shell with a just visible spire. The slightly ovate peristome is angulate at the suture. Callosity missing along the inner lip.