Famennian and Lower Carboniferous trilobites of the subfamily Cyrtosymbolinae (Proetidae) from the cephalopod biofacdes of the Holy Cross Mountains (Góry Świętokrzyskie) are described. Of the 51 species described, 20 are new
and 26 are identified only at the generic level. The variability and ontogenetic development of the species are investigated. Suggestions on the occurrence of proetid and phacopid trilobites in correlation with the type of lithofacies are made. An attempt is made to base the stratigraphy of Famennian and Lower Carboniferous beds on the trilobites here studied.