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The thorax of Hypodicranotus has ten segments and a spine on the eighth. The ages of Erratencrinurus s.l. spicatus and Erratencrinurus (Erratencrinurus?) vigilans in the Lake St. John district do not confirm their temporal roles leading to subgenera of Erratencrinurus, as has been recently suggested. Phylogenetic analyses of large data sets of species previously referred to Encrinuroides and Physemataspis yield a minimal length cladogram containing 18 species. Encrinuroides is restricted to four species, two of which have biogeographic affinities with Iapetus. These results lead to three clades, named the Walencrinuroides n. gen. clade, Frencrinuroides n. gen. clade, and finally the Physemataspis clade, with an enlarged concept of the genus with the erection of Physemataspis (Prophysemataspis) n. subgen. These last three clades are restricted to North America and Scotland, with alternating predominance of one region. Walencrinuroides s.l. gelaisi n. gen. n. sp. is described. New morphological data on Erratencrinurus s.l. spicatus confirm its close relationship with the clades discussed above. Data are insufficient for phylogenetic analysis of selected cheirurine species here surveyed. Eye position, glabellar segmentation, and pygidial shape differentiate the genera Ceraurus and Gabriceraurus; emended diagnoses of these genera are presented. Ceraurus globulobatus and C. matranseris are distinct, but morphologically close to one another. The status of Gabriceraurus dentatus can be stabilized on its extant types.

So far, the Palaeozoic fossil jawless vertebrates have not provided any direct evidence for the organization of the gills, apart from vague impressions--supposedly left by gill filaments--on the bony surface of the gill chamber in certain armoured forms or 'ostracoderms' (for example, osteostracans and heterostracans). The latter are currently regarded as more closely related to the living jawed vertebrates (crown gnathostomes) than to the living jawless vertebrates (hagfish and lampreys, or cyclostomes). Here we report the first direct evidence for the position of the gill filaments--possibly supported by gill rays--enclosed by gill pouches in a 370-million year (Myr)-old jawless vertebrate, Endeiolepis, from the Late Devonian fossil fish site of Miguasha, Quebec, Canada. This extinct jawless fish has much the same gill organization as living lampreys, although it possesses an unusually large number of gill pouches--a condition unlike that in any extant vertebrates and that raises questions about gill development. Endeiolepis is currently regarded as a close relative of anaspids, a group of 410-430-Myr-old 'ostracoderms'. Assuming that current vertebrate phylogeny is correct, this discovery demonstrates that pouches enclosing the gills are primitive for vertebrates, but have been subsequently lost in jawed vertebrates.

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Four previously defined formations within the Chicoutimi outlier are extended to the Lac Saint-Jean outlier; these formations are gradational into one another. The lowest of these formations, the Tremblay, is restricted to siliciclastic strata (predominantly coarse-grained sandstones); the overlying Simard, to micritic limestones. This last-named formation is succeeded by the highly fossiliferous Shipshaw Formation, composed of alternating limestones and shales, whereas the youngest of the previously named carbonates, the Galets Formation, is made up of echinodermal calcarenites. Graptolitic shales, herein assigned to the new Pointe-Bleue Shales, overlie in sharp contact the Galets; the youngest limestones of the area, previously assigned to the Richmondian, are different from the other Ordovician limestones. Trilobite faunas from the Shipshaw (and Galets) are correlated with the Edenian; the same correlation is probable for the uppermost of the four informal units recognized within the Simard Formation. The lowest three informal units of the Simard Formation are assigned to the Kirkfieldian; Shermanian strata have not been identified but are probably present. The Pointe-Bleue Shales were previously assigned to the Maysvillian. The Simard Formation contains an "Arctic" fauna, also present in the Manicouagan outlier but yielding in this last case a Shipshaw–Galets trilobite fauna. The Simard fauna, previously correlated with the "Black River," is thus interpreted as significantly time transgressive and of limited stratigraphic use. Depositional environments present in the Lac Saint-Jean and Chicoutimi outliers, but absent in southern Ontario during the Shermanian and Edenian, account for the necessity of significantly increasing the biozones of numerous taxa.