The structure of vesicular tissue in bryozoans Esthoniopora lessnikowae (Modzalevskaya, 1953) from the Latorp Horizon (Lower Ordovician) of the Leningrad Region is studied for the first time. The intercolonial variability of this species, which is expressed in the variations in the thickness of the walls of autozooecia, shape of apertures, and the structure of vesicular tissue, is thoroughly studied. New data are used to supplement the description of the species E. lessnikowae (Modzalevskaya, 1953) and the diagnosis of the genus Esthoniopora Bassler, 1911.