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

Clavagella it is made by opening and closing of the free valve against the other valve. The valves are very small in Penicillus while the shell fills up the anterior part of the crypt in burrowing Clavagella. With the exception of the shell the anterior part of the ciypt usually does not show growth lines. According to SAVAZZI (1982b) the growth model of the crypt is the following. After a period of life with free, articulated valves, the anterior region of the ciypt, including the anterior tubules, is formed first. This part will not be subsequently modified, therefore it predetermines the future adult size of the specimen. While the ciypt progressively sinks into the sediment due to the active hydraulic burrowing mechanism, the siphonal tube is being developed at the posterior end, maintaining the siphonal opening just above the sediment surface. The siphonal tube may form 90% of the total length of the adult crypt. Some collar-like structures can be found at the distal end of the siphonal tube to prevent further sinking in the substrate. According to TAYLOR et al. (1973) the material of both the shell and the tube of clavagellacean bivalves are aragonite. The tube of Penicillus is made up of platy crystals 0.5-2 micrometer in diameter, 0.3-0.5 micrometer in width and irregular in outline but aligned with the long axis parallel with the outside of the tube. Most Recent and fossil clavagellaceans are shallow-water bivalves, but some of them can survive intertidal environments and a Recent species were mentioned from deeper water (SAVAZZI 1982a). According to DAVITASHVILI & MERKLIN (1966) clavagellaceans can be found in shallow water sublittoral environments, but were mentioned down to 180 metres at the Australian and Asian coasts of the Pacific Ocean. Stirpulina lives in soft bottoms (DAVITASHVILI & MERKLIN 1966) but SAVAZZI (1982a) also mentioned silty sand as preferred substrate for all tube dweller Clavagellaceans. Representatives of the superfamily can be found all over the world, mainly in temperate and warm seas. CLAVAGELLACEAN BIVALVES FROM THE MIOCENE DEPOSITS OF THE PARATETHYS Since no valves are available, only a tube fragment, it is determined only to the (sub)generic rank, as Clavagella (Stirpulina) sp. On the basis of the data in the literature Clavagella (Stirpulina) bacillum is a species, which is known from some European Miocene localities. It was mentioned from Italy (SACCO 1901), and some localities from the Vienna Basin (HÖRNES 1870). VADÁSZ (1906) described also this species, and a new clavagellacean species ("Aspergillum" miocaenicum) from the Middle Miocene Leitha limestone from Budapest, Rákos. (''Aspergillum" is an invalid name for Penicillus (KEEN & SMITH 1969)). According to BALUK & RADWANSKI (1984) the fragmented parts of Stirpulina tubes can be found frequently in the topmost part of the Middle Miocene Korytnica Clay in Poland. In the absence of real valves, these fragments are also determined only to the generic rank. Some of their dichotomously branching tube fragments (for example Pl. II: 5) are very similar to the Szob specimen. So clavagellacean bivalves seem to be very rare elements of the Miocene faunas on the basis of the literature. However, probably there are several unpublished specimens