Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 14. 1989. (Budapest, 1989)
Remarks : The specimens slightly differ from Rhynchonella moutoniana d'Orbigny in having no little lateral ribs and being circular in outline. The little lateral ribs also appear in SMIRNOVA's description of L. moutoniana , but she remarks that they develop only at adult stage. The majority of my specimens are juvenile forms as they could have been released easier from the preserving limestone. Their internal structures agree closely with those pub lished by SMIRNOVA. According to her, the species described by KARAKASCH (1907) can be assigned to Lacunosella moutoniana as they were distinguished by the width and the depth of the sinus, by the number of the ribs in the sinus, and by the absence or presence of the little lateral ribs. SMIRNOVA had examined numerous specimens from one locality and established that these varieties fell within the limits of variation for the species. The studied material seems to reinforce SMIRNOVA's establishment by showing transitions between the extreme forms. It significantly differs from Rhynchonella malbosi Pictet var , tenuicostata Noutsoubidse , 1945 by ribs developing at ,the anterior third of the shell only. Distribution : Lower Barremian of Crimea and France (Mouton); Barremian and Aptian of Georgia. Genus Orbirhynchia Pettit, 1954 Orbirhynchia parkinsoni Owen, 19 59 (Plate I: 17-18) 1872. Rhynchonella sulcata (Parkinson) - PICTET, p. 35, pi. 99, Figs. 1-3,6 1913. Rhynchonella sulcata (Parkinson) - JACOB and FALLOT, p. 66, pi. 9, Figs. 14-15 1959. Orbirhynchia parkinsoni OWEN, p. 250, pi. 5, Fig. 2 Material: complete pedicle brachial specimen valve valve Szilas-árok 7 18 33 Bocskor-hegy 17 3 Eperkés-hegy 10 18 Dimensions (mm): L 21 W 21 T 10 15 16 8 Description: The shell is rounded triangular or pentagonal in outline with maximum width at the anterior third and maximum thickness at the mid-line. The pedicle valve is depressed, being convex near the umbo only. It has a low sulcus. The umbo is massive, flat, suberect, pointed at the end. The rounded foramen is hypothyrid. The beak ridges are rounded. The interarea is short and wide. The brachial valve is rounded, inflated, with maximum convexity near the umbo. It has a very weak median fold. The lateral comissure is arched, the anterior one is widely, linguiformly uniplicate. On both valves, there are 25 to 30 coarse and sharp radiating ribs, 5 of which are in the sulcus, getting more marked towards the margin. Internal structures: The pedicle collar is narrow. The hinge plates are straight and narrow. Falcifer crura are present. Thin plates develop on the crural bases. The dental plates are massive, parallel to one another or slightly diverging. The outer and inner socket ridges are well developed. The conspicuous median septum is very low, reaching 2/3 the length of the valve (Fig. 6). Remarks : This form agrees fairly well with Lamellaerhynchia rostriformis externally, but its internal structures with the falcifer crura are completely different. It also differs from Orbirhynchia parkinsoni Owen, 1959 in having a median septum, although it is very low and could be observed in one individual only. They also differ in age: in the Bakony Mts. it is Aptian, while OWEN's species is from the Upper Albian. SMIRNOVA (1972) described a species as Orbirhynchia asymmetrica from the Upper Aptian of the northern Caucasus, but our form significantly differs from that in having a larger and more depressed shell with a deeper and wider sulcus. In addition, the number of the ribs is less, and the beak-ridges are more rounded. Great variability can be found in the number of the ribs, but as the general outline of the shells is quite uniform, and transitional forms were found, I consider it to be of intraspecific variability.
