Two new microconchid (Tentaculita Bouček, 1964) genera from the Early Palaeozoic of Baltoscandia and England

Two new genera of microconchids (Palaeoconchus n. gen. and Annuliconchus n. gen.) are introduced from the Ordovician and Silurian of Baltoscandia and Silurian of England. The new genera represent the earliest record of microconchids. Spirorbis tenuis Sowerby from the Wenlock of England is assigned to Palaeoconchus n. gen., and Palaeoconchus minor n. sp. is described from the Upper Ordovician of Estonia. Spirorbis siluricus Eichwald is assigned to Annuliconchus n. gen. A. lectotype is selected for the latter species.