ABSTRACT: Middle Ordovician (Darriwilian) monothalamous agglutinated foraminifers are described for the first time from strata of the Lashkarak Formation of the Simeh-Kuh section, AlborzMountains, northern Iran. One new genus Damghanites Nestell and Ghobadi Pour with the type species D. lashkarakensis, and three new species Amphitremoida simehkuhensis, Sorosphaera iranensis and S. darriwiliensis are described. Analysis of the foraminiferal wall of some of these species has revealed the presence of quartz, feldspar, products of feldspar degradation and rare grains of anatase, and also the presence of iron. Conodonts fromthe lower part of the Lashkarak Formation indicate an age within the interval of the Lenodus variabilis to Eoplacognathus? pseudoplanus zones of the lower Darriwilian (Middle Ordovician).