New data on trilobites from Hecker mud mounds (Ordovician) in the Leningrad region

Twenty-three trilobite species were found in Hecker mud mounds of the Ordovician deposits from the Leningrad region. Most characteristic of Hecker mud mounds are the following four species: Ampyx pater Holm, Celmus longifrons Poulsen, Diaphanometopus volborthi (Schmidt), Orometonus gryphos Tjernik. These species are also known from South Sweden and Bornholm. The above findings enabled the author to suppose that there are two more Hecker mud mounds in the Volkhov horizon of the Leningrad region: those on the Lopukhinka and Gummulosarovka rivers.