Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 79. (Budapest 1987)

Conti, M. A. ; Szabó, J.: Comparison of Bajocian gastropod faunas from the Bakony Mts. (Hungary) and Umbria (Italy)

may change. There are many form-pairs, in which the only significant difference is the opening of an umbilicus. Only larger umbilicus angle-intervals together with (an)other feature(s) may chara.cterize higher taxa, for example: appearance of planispiral or pseudosinistral (hyperstrophic) coliing. The simple presence-absence pair may be base of subgeneric distinction at most. In our opinion, the latter one seems more likely but we cannot verify this opinion without doubt. Owing to this reason, this principle is not consistently followed in this paper. In case of Crossostomotidae, Crossostoma and Palaeocollonia are treated in the traditional manner as independent genera, though the only difference between them is the prsence of an umbilicus in Palaeocollonia. However, this character is used to separate only subgenera in another family (Coleostylinidae). Family Euomphalidae DE KÖNINCK, 1881 Discohelix cooki CONTI et FISCHER, 1984 1968: Discohelix (Discohelix

) cotswoldiae (LYCETT, 1850) — WENDT, p. 520, Pi. 110: 5-12, figs 2F, 3M 1979: ? Discohelix cotswoldiae (LYCETT, 1850) — SZABÓ, p. 25, Pl. II: figs 1-3., fig. 6F. 1984: Discohelix cooki CONTI et FISCHER, p. 132, fig. 5., Pl. I: 5a-b, 6a-b, 7a-b. 1987: Discohelix cooki CONTI et FISCHER, 1984 — CONTI & MONARI, p. 182, Pl. I: figs 12-13. Remarks — The identification, given by Wendt (cit. above) is not correct. The dimensions of the real D. cotswoldiae are much smaller than those of Wendt's figured specimens, belonging really to D. cooki CONTI et FISCHER, 1984. An adult shell of this species is about twice larger than that of Lycett's species. The ornament is also different: D. cotswoldiae has nodulae along the outer angulations but D. cooki bears radial riblets at comparable position. In a previous paper, SZABÓ (1979) has already tried to denote the fact of this misidentification, though it was not put unambiquously owing to a misinterpretation during the printing (place of questionmark!). The Umbrian and the Bakony material do not contain such markedly ornamented specimens which are figured by WENDT (1968) in Pi. 110: figs 9-12. A possible explanation: Wendt's material cosists of Aalenian and Bajocian elements (condensed fauna) ; the mentioned forms might be the earlier (Aalenian) ones which are not only temporarily but also morphologically nearer to the possible ancestor, the Toarcian, more markedly sculptured D. dyctiota WENDT, 1968 than the Bajocian specimens. The embryonal spiral lineation is not visible in the Umbrian specimens of D. cooki but its lack certainly originates from the poor state of preservation. Such fine ornamental details might have easily disappeared during fossilization. Distribution — W Sicily, Condensed Aalenian-Lower Bajocian; Bakony Mts., Humphriesianum-Parkinsoni Zone; Case Canepine, Humphriesianum Zone; "Bivio Macerino" ?Aalenian-Bajocian (? Condensed Murchisonae to Humphriesianum-Humphriesianum Zone). Family Phymatopleuridae BATTEN, 1956 GENUS TROCHOTOMARIA CONTI et FISCHER, 1981 Type species: Trochotomaria somhegy ensis (SZABÓ, 1980) -— see below. Original diagnosis: "Shell trochiform. Selenizone at midwhorl, slightly depressed below surface, limited by two spiral cords and denticulated by transversal costellae. Ornament collabral and spiral element, collabral dominant. Periphery angular; base flattened, with deep and narrow umbilicus which is abruptly delimited and costulated inside. Aperture quadrate, with thin and right columellar lip". Remarks — Trochotomaria was originally defined after some Umbrian juvenile specimens, on which the position of selenizone was at the midwhorl. In the adult Bakony specimens, however, it was below the midwhorl. This shifting of the selenizone between this two stages is characteristic tor Trochotomaria (Fig. 1A). It is necessary to emphasize that this genus has a somewhat different embryonal-juvenile shell than the other members of the family, having depressed or planispiral initial whorls. In Trochoto-