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

In POJETA & SOHL (1987) just like in BALUK & RADWANSKI (1984) Stirpulina is regarded as a distinct genus and not as a subgenus of Clavagella. On the basis of the small fragment it is not possible to take sides and the "Treatise" is followed. The representatives of the superfamily Clavagellacea are rare both in Recent and fossil materials. These bivalves only in some cases were observed alive (see SAVAZZI 1982a). Most Recent clavagellaceans are tube dwellers in soft bottoms, but several rock-boring forms are also known. Within the genus Clavagella, C. (Clavagella) and C. (Stirpulina) subgenera are burrowed into soft substrates while C. (Bryopa) and C. (Dacosta) subgenera are bored into hard substrates. Sometimes the same species may be facultatively borer or tube dweller. According to POJETA & SOHL (1987) all known Cretaceous clavagellids are burrowing species, so probably this is the ancestral mode of life of the clavagellids. SAVAZZI (1982a) used the term crypt to indicate the whole external construction of tube-dweller bivalves (burrow or borehole, calcareous lining, adventitious envelope, shell fused to the envelope). In adult tube-dweller clavagellaceans the ciypt is usually straight and long and the shells can be found at the anterior end of the ciypt. In Penicillus both the valves are fused to the envelope, in Clavagella only the left valve is fused to the envelope and the right one is free within the tube, while in Humphreyia both the valves are united into a single calcareous plate. At the anterior part of the crypt lots of tubules (Clavagella) or perforations (Penicillus) can be found. These openings are probably used in the burrowing process of the crypt by outward-directed water currents (SAVAZZI 1982b). The water pumping is made by the highly muscular anterior part of the mantle in Penicillus, while in Fig. 3. Life position of Clavagella (Stirpulina) sp.