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)

Ornament: It consists of prosocline growth-lines being prosocyrt in a narrow band along the suture. Distribution : Bakony Mts., Somhegy: Humphriesianum Remarks : These specimens are comparable with such forms, that have been uncertainly determined by earlier authors: Nerita (Neridomus) "near to" ovata ROEMER (by HUDLESTON, 1894) and Nerita cf. ovula BUVIGNIER (by UHLIG,1881). The exact determination needs more and well preserved material. Family Crossostomatidae Cox, 1960 Genus CROSSOSTOMA MORRIS & LYCETT, 1851 Crossostoma sp. (Plate II: figs. 4—5) Measurements: H HL HA D W A Plate II: figs. 4-5 11 9.5 8.5 17.5 122° Material: A single, damaged shelly specimen. Shape : Dextral, low turbiniform species. The whorls are convex and axially somewhat depressed, and along the suture, the shell bends slightly upward the former whorl. On the last half whorl, there is a narrow, somewhat concave band below the suture. Near the peristome, a short section of the last whorl deviating from the former mode of coiling observable ; it bends somewhat downwards. The rather prosocline peristome is rounded, somewhat thickened and extended like a trumpet. The columellar lip is not observable as well as the medial region of the depressed-convex base having certainly a deep excavation or a broad umbilicus. Ornament : The only ornamental elements are the very fine, prosocline growth-lines. Distribution : Bakony Mts., Somhegy: condensed Subfurcatum to Garantiana Zone. Remarks: It is similar to d'ORBIGNY' S Crossostoma reflexilabrmn, but much more depressed and the building of the peristomeis significantly different. It seems to be a new species, howewer, without the knowledge of the umbilical (?) region, the definition of such a featureless species would become doubtful. Crossostoma ? cf. perampla (UHLIG, 1881) (Plate II: fig. 6) (Plate II: fig. 6) cf. 1881: Vitrinella perampla n. f. UHLIG, p. 402, pl. IX, f. 19. Measurements: H HL HA W D A Plate II: fig. 6 13 125° Material : Three, poorly preserved specimens. Shape : Dextral, low-spired, almost discoidal species with thick-walled shell. The diameter of the few, axially depressed whorls is growing quickly. The periphery is much more convex than other parts of the surface of the whorls. Owing to the downward deviation of the last whorl, the rounded peristome is rather prosocline. The suturai part of the outer lip and the columellar lip are thickened and certainly, there is a waek, circular inner varix on the remaining parts of the peristome. It is observable only in an impression of an inner mould of a badly preserved specimen. Ornament : The species is ornamented by fine growth-lines, which are orthocline on the whorls and prosocline at the peripherial basal parts. Distribution - Bakony Mts., Somhegy : ? Upper Bajocian. Remarks : The shape of this species is comparable with some ataphrid forms, but the deviating last whorl and the thickening of the circular peristome are indicative of Crossostoma. The specimens are similar to UHLIG'S species, but owing to the damages, important