The studies of Cyclops O.F. Müller, 1776 have more than two centuries of tradition in Fenno-Scandinavia, yet, basic taxonomic questions remain unresolved and the limits of the distributional area are very poorly understood in the majority of the taxa (11+) occurring in the region. Based on the types and other materials we redescribe two species, C. lacustris G.O. Sars, 1863 and C. bohater Koźmiński, 1933, the latter being reported here for the first time from Fenno-Scandinavia; lectotypes of both species have been designated herein. Setulation characters of the antennal coxobasis- and maxillulary palp setae and P1 medial spine, as well as the spine formula of the terminal exopodal segments of the swimming legs (3433) in the adult female distinguish C. lacustris and C. bohater from their congeners. An identification key is provided to the Cyclops species of Fenno-Scandinavia, including information about both the female and male morphology. Although the limited material does not allow us to define the species range limits, our data nevertheless support a Northern European distribution in C. lacustris, and Northern and Central European distribution in C. bohater, while the records from the southern Palearctic need further verification.
Cyclopidae, morphology, zoogeography, freshwater, Europe.