Lower Silurian Conodonts from Northern Michigan and Ontario

Conodonts representing 50 species, 8 new, from 19 genera, one new, were collected from 15 outcrop sections and a core of lower Silurian rocks in the northern peninsula of Michigan and in Ontario. New taxa include the genus Exochognathus and the following species: Ambalodus anapetus, Aphelognathws siluricus, Exochognathus keislognathoides, Icriodella discreta, Spathognathodus comptus, S. elibatus, S. hassi, and S. manitoulinensis. The conodont zone between the top of the Ordovician and the base of the Icriodina irregularis Assemblage Zone is named the Panderodus simplex Assemblage Zone.