Oelandiella, the earliest Cambrian helcionelloid mollusc from Siberia

The helcionelloid molluscs Oelandiella korobkovi and O. sibirica Vostokova are redescribed on the basis of type material from the lowest Cambrian of n orthern Siberia. Oelandiella is reinstated as a recognizable genus separate d from Latouchella Cobbold, of which it has been considered generally to be a junior synonym, by differences in the prominent comarginal plication. Th e bilaterally symmetrical shells of both of these genera are readily delimi ted from Oelandia Westergard, originally described from the Middle Cambrian of Sweden, which has a characteristic asymmetrical alternation of plicae.