Multielement taxonomy was instituted for Ordovician conodonts over a decade ago, and probably a majority of the multielement genera have been defined or are well understood. The present systems of notation for elements within apparatuses are inadequate and cumbersome. A new notation scheme is proposed which applies a single‐letter code to the position in the apparatus occupied by certain element morphotypes. The taxonomic status of all known Ordovician conodont genera is reviewed (appendix) using the new notation, and a new scheme to classify conodont apparatuses is presented. Five main apparatus types (I‐V) and seventeen subtypes (IA‐IC, etc.) are defined. Within these groups, all known Ordovician conodont genera can be accommodated, and probably few new groups are required to include all other conodont genera. The apparatus types and subtypes are defined on the basis of symmetry, curvature, and number of the element types, with a clear distinction being made between the first and second transition series. Certain homologous relationships, both between and within many apparatus types, are noted. The evolution of the five major types, and the subtypes, is traced through the Ordovician. The pattern of evolution suggests that the types and subtypes recognized are probably natural biologic groupings, largely reflecting phylogenetic change.

The Tetagouche Group is a 10 000 m geosynclinal sequence of slates, greywackes, rhyolite tuffs, and greenstones underlying parts of northern New Brunswick. It hosts the well-known stratabound massive sulphide deposits of the Bathurst–Newcastle mining area. Few fossils have been found in the group and its age is poorly known. More than 890 conodonts have been recovered from a locality near Camel Back Mountain in the Metabasalt unit. Coelocerodontus? lacrimosus and Protopanderodus liripipus are described as new species. The faunule contains species indicative of the Prioniodis alobatus Subzone of the Amorphognathus tvaerensis Zone and is the first record of the subzone in North America. The subzone equates with the middle Caradocian (approximately the Soudleyan Stage) or late Wildernessian Stage of the Middle Ordovician Epoch. During this interval the Proto-Atlantic Ocean is considered to have been undergoing closure, hence recent interpretations that regard the Metabasalt unit as forming during an earlier phase of opening must be reexamined.

Uppermost Cambrian and lowest Ordovician slope deposits in Highgate Gorge, northwestern Vermont, yield a succession of conodont faunas (and a few associated trilobite species) similar to that observed in coeval North American carbonate-platform sequences. Decimeter-scale sampling of a 15-m-interval in two sections comprising thin-bedded limestone–shale rhythmites alternating with thick-bedded debris flow conglomerates yielded 60 trilobite specimens and more than 5,000 conodont elements from 48 productive horizons. The new biostratigraphic control does not support earlier claims that the lowest occurrence of Cordylodus proavus in the Gorge Formation and presumably in other slope sequences is significantly older than the base of the C. proavus Zone in platform deposits; rather, it demonstrates the isochronous persistence of this boundary across the North American (Laurentian) shelf margin into Iapetan slope deposits. The common occurrence of the deep, cool-water conodont Eoconodontus alisonae and the agnostoid trilobite Lotagnostus hedini in the Eoconodontus Zone at Highgate Gorge makes it possible to extend the correlation even farther from the Laurentian platform into uppermost Cambrian strata in Kazakhstan and China. This new information greatly strengthens arguments in favor of using this zonal boundary for defining the international boundary between the Cambrian and Ordovician Systems.In earlier studies of Highgate Gorge strata, composite treatment of biostratigraphic data from similar but non-correlative intervals (Zones 2 and 3) in two sections created an illusion of significant stratigraphic overlap of C. proavus with older faunas and direct association of some trilobite species for which overlap has never been established. Composite treatment of data from Zones 2 and 3 under designations such as “main zone’ or “upper zone’ should be discontinued and species that have been reported as occurring together in the “main zone’ should not be assumed (on the basis of that association alone) to have come from the same stratigraphic level.

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