Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 18. 1996. (Budapest, 1996)

Bivalve assemblages of seamount-tops and slopes show similar guild-structures. Epifaunal byssally attached forms highly dominate in both environments (88 and 97%, respectively). Pectinids are especially frequent (41 and 45 %). In the red biomicrites smooth and delicately ornamented scallops, such as Entolium (E.) lunare (Roemer, 1839) (Pl. I: 4) and "fine" phenotypes of Praechlamys subreticulatits (Stoliczka, 1861)(P1. I: 5), prevail. In the Hierlatz limestone "coarse" phenotypes of P. subreticulatus are much more frequent (SZENTÉ, in press). Limids are also important elements in seamount top and slope assemblages (15 and 14%, respectively). Species of Parainoceramus are relatively common in seamount-top faunas (12 %) and become more frequent in the assemblage of the Hierlatz limestone (32%). Subordinately (4%), presumably semi-infaunal forms such as "Modiolus" malfattii Fucini, 1906 also occur in the assemblage of red manganiferous limestones. Shallow and deep burrowing forms, such as Tutcheria cingulata (Goldfuss, 1838) (Pl. I: 11) occur subordinately in seamount top and slope assemblages (4% and 5%, respectively). (Recently, Tutcheria Cox, 1946 was mentioned by LIU (1995) as restricted to the Boreal Bivalve Province during the Pliensbachian. Although this genus can be found as a characteristic element in faunas of the Boreal Province (see HOLDER 1995), it occurs in Mediterranean faunas as well (see e. g. "Cardium" italicum in FUCINI 1895, p. 240, pi. 8, fig. 13)). Guild structures of bivalve faunas of the basinal sediments differ significantly from those of the seamount assemblages. In the crinoidal, spiculitic or cherty limestones the high proportion of epifaunal byssate forms is due to the abundance of Caenodiotis janus at the Káváshegy locality (28%). This species (Pl. I: 2) belongs to the "paper pectens" and judging from its mass and exclusive occurrence (see e. g. MONARI 1994), C. janus was an opportunistic benthic species, or may represent the pseudoplanktonic mode of life. Parainoceramus is also an important element in basinal sediments (19.5 and 28%, respectively), represented by at least three species including P. cantianensis MONARI, 1994 (Pl. I: 1). In ammonitico rosso limestones several species of Limea (Pseudolimea) occur relatively frequently (12%). Other limids, such as Plagiostoma punctatum J. Sowerby, 1818 (PI. I: 3) are extremely rare. The infauna of the basinal sediments consists of presumably shallow burrowing taxa, such as "Astarte" kamarika TAUSCH, 1890 (Pl. I: 12) and several other, unidentified forms. Deep burrowers are represented by Pleuromya (Pl. I: 13). In ammonitico rosso limestones medium-sized, posteriorly rostrate bivalves occur frequently (Pl. I: 14-15), which bear considerable resemblance to some genera of the family Cuspidariidae DALL, 1886. Cuspidariids are micro-carnivorous bivalves characteristic of Recent deep-sea faunas (e. g. KNUDSEN 1967, 1970), living on "friable" substrate (BERNARD 1979). Although the Bakony specimens are internal moulds and their sound identification is not possible, their shape as well as the apparent lack of traces of well defined teeth may indicate that they represent Cuspidariidae. Presence of possible ancestors of Recent deep-sea bivalves is not unexpected in the Mediterranean Pliensbachian. As SZABÓ (1995) demonstrated, the environmental distribution of eucyclid gastropods in the Pliensbachian and Toarcian of the Transdanubian Mid-Mountains is very similar to that of their living relatives. Recent descendants of the genera characteristic of basinal Jurassic sediments are living today in bathyal depths.