The Ashgillian Pabos Formation underlies the Ashgillian-Llandoverian White Head Formation and consists, in the immediate Perce area, of 21 trilobite taxa. Of these, 11 are left in open nomenclature, four of which are summarily described, commented upon, and illustrated. Ten species are specifically determined and three of these are new: Remopleurides arenosus, Achatella (Achatella) clivosa, and Meadowtownella sacerdos. Hibbertia whittingtoni (McNamara, 1979) is a junior secondary homonym and renamed H. conistonensis. The Ashgillian-Llandoverian cheirurines of the Perce area are reviewed and new generic assignments suggested; these are a major component of the Pabos trilobite fauna. Revision of Ceraurinus icarus, a widely distributed North American species, shows its inherent variability; limits of variation, more complete descriptions, and stratigraphic distribution of most previously described species are also given. The distinctive trinucleid Novaspis elevata occurs in the Pabos, outside the immediate Perce area. Almost all of the Pabos trilobites are also present in the coeval Grande Coupe beds of the Matapedia Group; otherwise they are a mixture of taxa with greatest faunal affinities with North American or northwestern European taxa of the same age.