Frasnian deposits in Poland are mostly organogenic, forming biostromes and bioherms. The latter should be considered as reefs, because they are rigid, continuous structures, elevated above the sea floor. In the Holy Cross Mts they form a chain along the Dyminy anticline. Some communities of these bioherms are preserved in situ. The fauna in biostromes is mostly redeposited a short distance from the site of life. Depositional environments changed in the uppermost Frasnian becoming more terrigenous. The lower Famennian is characterized by intercalations of marly limestones and shales containing small horn-shaped corals, blind trllobites and small bivalves. Upper Famennian depositional environments were variable. External morphology of corals, shape of their calices, ornamentation of septa and arrangement of skeletal elements reflect their habitats.