Silurian inarticulate brachiopods from Poland

Members of four families are recognized from etched Wenlockian carbonates from the eastern Poland. The acrotretids are of special interest as being recorded in the Polish Silurian for the first time. Of two acrotretid species, Opsiconidion podlasiensis is described as new. The dorsal median septum of the genus Opsiconidion is discussed in detail.