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)

Material :31 specimens (5 complete but more or less encrusted shells; the others are internal and external casts or fragments.) — Locality : Borzavár, Rhaetian yellow limestones. Dimensions (mm): length: 14.3 12.3 11.3 9.5 9.0 height: 11.0 9.7 9.3 7.6 7.6 Description : Small shell with slight inflation. The outline is elongate, subquadrate, very inequilateral. The hinge margin is nearly straight and passes gradually into the straight, vertical posterior margin. The posterior portion of the ventral margin is straight while the anterior portion forms an even curve with the anterior margin. The umbo lies very anteriorly. A diagonal ridge runs from the umbo to the posteroventral corner; there is a flat or gently concave area behind this ridge. The outer surface of the shell is ornamented with 20 sharp radial ribs, with U-shaped interspaces. About five ribs cover the area behind the diagonal ridge; these are weaker than the others. The inner surface of the shell is also ribbed ; the internal cast shows sharply incised radial grooves which correspond to the interspaces of the outer ornamentation. The weak growth lines are lamellose in some cases. Remarks : The presence of the posterodorsal "area", the number of the ribs (about 20) and the internal ornamentation distinguish P. munita from the other Rhaetian species of Palaeocardita. STOPPANI (I.e.) and DITTMAR (1864, p.182.) emphasized the importance of secondary riblets, asymmetrically intercalated between the ribs. These were not observed on the specimens from Borzavár, perhaps owing to their relatively small size (immature stage ?). It is to mention however, that this feature is very vaguely seen in STOPPANI'S figures, and that the photographs published by DESIO (I.e.) (holotypus!), ALASSINAZ (I.e.), BELLONI (I.e.) and SIRNA (I.e.) do not show secondary riblets. The specimens figured by VÉGH (I.e.) are internal casts with about 20 ribs (or rather grooves) therefore they can not be P. austriaca (with 25-28 ribs and flat internally), but belong to P. munita. Distribution : Rhaetian of the Southern Alps, the Northern and Central Apennines and the Bakony Mts. (Hungary). Genus MYOPHORIOP1S WÖHRMANN, 1889 Myophoriopis isosceles (STOPPANI, 1857) (Plate II: 10) * 1857 : [Nucula] Isosceles STOPPANI, Studii geol., p. 385. 1863: Myophoria isosceles STOPP.—STOPPANI, Couches à Avicula.

.., p. 128, pi. 30, fig. 1-4. 71870: Schizodus isocèles DITTM. [sic!] — FISCHER-OOSTER, Thun, p. 64, pl. II, fig. 25. 1962: Myophoriopis isosceles (STOPPANI) 1857 — ALASSINAZ, Retico Endine (pars), p. 351., pl XXV, fig. 4 (7 5-6.) 71964: Myophoriopis isosceles (STOPPANI) 1857 — GELATI et ALASSINAZ, Alta Valtellina, p. 52, pi. I, fig. 10-11. vl964: Myophoriopis isosceles (STOPPANI). 1861 — VÉGH, Rhät, Südl. Bakonygeb.. p. 41, 79, pl. III, fig. 18-19. 71968: Myophoriopis isosceles (STOPPANI, 1857) — SIRNA, Monti di Amelia, p. 779, pi. 55, fig. 9. Material : 5 specimens (internal casts with shell fragments). — Locality : Borzavár, Rhaetian yellow and grey limestones. D i m e n s i o n s (mm): length: 24.5 >23.0 >21.0 13.0 height: 23.9 22.8 20.1 12.7 Description : The shell is of large size for the genus; strongly inflated. The outline is subquadrate to subcircular, nearly equilateral. The anterior portion of the hinge margin forms an evenly convex curve with the anterior and ventral margins. The posterior margin is straight and delimited by a posteroventral and a posterodorsal corner. The posterior portion of the hinge margin is almost straight. The umbo is prominent, incurved, slightly prosogyrate. A sharp diagonal ridge or carina runs from the umbo to the posteroventral corner. The area behind this carina has concave surface. Escutcheon is present but hardly discernible. The surface of the shell is nearly smooth, only very thin growth lines can be observed on it. Remarks : The figures published by STOPPANI (I.e.) demonstrate this species very excellently. The figured specimens are relatively large, almost as high as long, with shortly