Drill holes on tests of Echinocyamus linearis from the Middle Miocene Korytnica Basin represent the first well documented fossil record of cassid predation from Poland. These traces complement the ecological information on the size and structure of cassid populations recorded by body fossils. The high number of drill holes recognised from the Heterostegina Sands, the uppermost part of the Korytnica depositional sequence, indicates the occurrence of a large cassid population during the late stage of development of the Korytnica Basin. The small size of most of the drill holes indicates that juvenile gastropods of the family Cassidae, which are not preserved in the fossil record of the investigated area, were also present in the cassid populations.

Key words: Cassidae, echinoids, drill holes, predation, population structure, taphonomy, Middle Miocene, Poland.

Tomasz Ceranka [tceranka@op.pl] and Michał Złotnik [mzlotnik@geo.uw.edu.pl], Instytut Geologii Podstawowej, Uniwersytet Warszawski, Żwirki i Wigury 93, PL−02−089 Warszawa, Poland.