Article: Acritarchs of the Middle Silurian Rochester Formation of southern Ontario

The Rochester Formation yields an acritarch microflora containing 24 genera and 46 species and varieties. Genus Hemideunffia; Species Domasia canadensis, D. rochesterensis, Hemideunffia trifurcata, Elektoriskos simplex, Filisphaeridium bifurcatum, Gorgonisphaeridium wenlockium, Lophosphaeridium rugosum and L. microgranulosum; varieties: Deunffia furcata var. niagarensis, D. monospinosa var. tonowandensis, and D. ramusculosa var. rochesterensis are proposed as new.The Rochester netromorph assemblage, in particular the Deunffia and Domasia complex, shows a close resemblance to those from the Ilion Shale in Utica, New York, the Rochester Formation in West Virginia, and the Buildwas Beds in Shropshire, Britain. The stratigraphically restricted genus Deunffia, in particular D. ramusculosa and D. furcata which probably made their first appearance during the Lower Wenlockian times, is present in all four areas.However, the absence of Deunffia and the presence of Domasia complex in the Wenlockian assemblages from Visby and Belgium suggest some connections with the Rochester assemblage; but the absence of Deunffia-Domasia complex in the Wenlockian assemblages from Spain and Sahara suggests fewer connections with the Rochester assemblage.