Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 73. (Budapest 1981)
Vörös, A.: A survey of the Rhaetian (Upper Triassic) Bivalvia from Borzavár (Bakony Mts., Hungary)
M a t e r i a 1 : 5 incomplete left valves in bad state of preservation. — Locality : Borzavár, Rhaetian yellow and pink limestones. Description : Small (length: less than 15 mm), very strongly convex shell. The umbo is placed anteriorly, gibbose, prosogyrate and projects above the hinge line. The outline is oblique, alate but the posterior wing can not be traced. The ornamentation consists of numerous (about 20) radial ribs and secondary riblets in the intervals. Remarks: R. contorta is a well-known and profusely documented species and since it is the only representative of the genus Rhaetavicula, the assignment of the specimens from Borzavár needs no further discussion. Distribution : Rhaetian of the British Isles, W Europe, Alps (in general), Apennines, W Carpathians, Bakony Mts. (Hungary) and Burma. Genus BAKEVELLIA KING, 1848 Bakevellia faberi (WINKLER, 1859) (Plate I: 11) 1856: Gervill. praecursor QUENST. — OPPEL et SUESS, Über die Äquivalente, (pars), p. 9, pl. II, fig. 3. (non fig. 4.) *1859: Gervillia Faberi WINKLER, Schichten der Avicula. .., p. 10. 1861: Gervillia ornata, MOORE —MOORE, Avicula contorta Zone, p. 500, pl. XV, fig. 8. Material : 3 specimens; two left valves and an internal cast. — Locality : Borzavár, Rhaetian grey and yellow limestones. Dimensions (mm): length: 17.2 16.8 9.3 height: 12.3 10.1 5.2 Description : The shell is of moderate size for the genus; moderately inflated. The outline is elongate, oblique, bialate. The dorsal (hinge) margin is straight and attains more than twothirds of the total length. The posterior margin of the posterior wing forms a gently concave curve and passes gradually into the convex posterior margin of the shell. The ventral margin is less convex, and after a short concave portion, the anterior auricle bulges strongly forward, showing a modioliform appearance. The umbo is almost terminal, prosogyrate and lies in the one-tenth of the total length. A diagonal ridge extends from the umbo to the anterior part of the ventral margin. The ridge has asymmetric flanks: very steep anteriorly and gently sloping posteriorly. The ornamentation consists of 6 radial ribs which run from the very point of the umbo to the posteroventral margin. The first of these ribs coincides with the ridge crest. A seventh rib can be seen delimiting posterodorsally the convex part of the shell. The ribs are sharp in the umbonal region but become flattened in their course. The posterior wing bears a narrow groove along its hinge margin. Thin growth lines developed on the whole surface of the shell ; they are particularly well seen on the auricles and in the ribs' interspaces. Remarks: B. faberi was erected by WINKLER (I.e.) for the ribbed specimen figured by OPPEL et SUESS (I.e.) as B. praecursor (QUENSTEDT, 1856). On the basis of well preserved material from the N Alps he was able to distinguish the ribbed B. faberi from the completely smooth B. praecursor. B. ornata described by MOORE (I.e.) can be regarded synonymous with B. faberi as it was expressed by DITTMAR (1864, p. 165). The relation between B. faberi and praecursor became somewhat confused because MOORE (I.e., p. 500., pl. XV., fig. 6) described a praecursor with radial colour bands and because DITTMAR (I.e.) wrote about transitional forms between the two species. It is hard to imagine a single species with completely smooth and characteristically ribbed forms together: a thorough study of a larger material would be needed to clarify this problem. The specimens from Borzavár (even the internal cast) show radial ornamentation, therefore they must be ranged into B. faberi. Distribution : Rhaetian of the British Isles, South Germany, the Northern Limestone Alps and the Bakony Mts. (Hungary).
