Phacopid trilobites are relatively widespread in Devonian deposits of north Gondwana and some have been collected from several sections of the Saoura Valley in SW Algeria. New occurrences of phacopids assigned to Trimerocephalus, Dianops and Phacops sensu lato are described from this area and comparisons are made with closely allied species from Morocco and Europe. The trilobite assemblages of the ‘Argiles de Marhouma’ Formation are considered to be Frasnian–Famennian in age. These new occurrences have been integrated into an analysis of Upper Devonian phacopid biodiversity. Diversity fluctuations reflect environmental changes, bioevents and stratigraphic turnovers throughout the Upper Devonian. Peak diversity was attained after the post-Kellwasser event.

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The brachiopods (Pentamerida, Rhynchonellida, Spiriferidina) that are described and illustrated are from the Blue Fiord, Bird Fiord and comparable formations of the Canadian Arc tic Islands, principally from Ellesmere, Devon and Bathurst Islands. The brachiopods were selected from numerous collections of fossils made by the Geological Survey of Canada during Operation Franklin (1955) and in subsequent field studies. The brachiopod faunas obviously are st rongly endemic in character; of the more than thirty species or subspecies identified, ten belong to genera or subgenera of limited geographic provenance, twenty-five are restricted to the Arctic and among these, twenty-one are new taxa. These are: Pentamerida: Carinagypa (Aseptagypa) maclareni, Ivdelinia grinnellensis, I. (Ivdelinella) ellesmerensis; Rhynchonellida: Ancillotoechia? ventricosa variabilis, Cupularostrum? pentagonale, C. ? ellesmerense, Camarotoechia s. l. pseudomedea, Hypothyridina bifurcata, Cassidirostrum vexans arcticum, Athyrhynchus susanae intermedius, A. sverdrupi eosverdrupi, A. trilobatus; Spiriferidina: Fimbrispirifer? pseudoscheii, F. fascicostatus, Warrenella disjuncta, W. franklini praefranklini (typical and transverse forms), W. collina arctica, W. pseudaequabilis, W. (Warrenellina) extensa, Emanuella bisiruata, Elythina sverdrupi. A considerable number of forms at present remain generically or specifically undetermined, because of insufficient material to allow reliable determination. The faunas of the two formations, especially that of the lower part of Blue Fiord Formation, clearly are related to Nevada faunas. At the close -of the Early Devonian, the Arctic Islands belonged to the same faunal province as Nevada and the Yukon. This province has been named the Cordilleran subprovince by Boucot et al. (1967) and considered by them to be a subprovince of the Old World Province. This connection between the Arctic Islands and Nevada continued at least for a part of the Middle Devonian, that is until the close of Blue Fiord sedimentation. These conclusions are deduced from the appearance at certain times of a number of common genera or species in the faunas of the two regions. These same elements are used to establish the following correlations which form the prime evidence of the ages of the rock units: (1) the Nevada zone of Eurekaspirif er pinyonensis (dated as Emsien) with the lower part of the lower member of the Blue Fiord Formation in the type locality; (2) the Nevada Zone of Leptathyris circula and the lower part of that of Warrenella kirki (dated as Eifelien) with the upper part of the lower member and the lower part of the upper member of Blue Fiord Formation in the type locality. The age of the Blue Fiord Formation at its type locality and in the other areas in which it outcrops is deduced principally from these correlations. The Bird Fiord Formation is dated at its type locality and in other parts of Devon and Ellesmere Islands as probably Late Eifelien but as probably Givetien in Bathurst Island, inferred principally from the distribution of certain brachiopod genera (Ivdelinia, Hypothyridina, Cupularostrum and Elythina). Among the representatives of these three groups of brachiopods, some elements show relationships with faunas from northeastern Russia, while some others have Appalachian or European affinities. The distribution of species within the Blue Fiord and Bird Fiord Formations at their type localities provides a basis to discuss !and in some cases to make more precise) correlations previously proposed by authors between these sections and rock units at other localities in the Arctic Islands where these formations have been reported.

Studies of fossils collected from the Nictaux–Torbrook and Bear River synclines (Nova Scotia) allow a reexamination of the Siluro-Devonian stratigraphy of the Meguma terrane. The location of this terrane relative to the main paleocontinents of the circumatlantic domain during this period is discussed. Wenlockian, Ludlovian, and Pridolian biostratigraphic horizons have been dated. The benthic fauna of the Torbrook Formation are assigned here to the Lochkovian, Pragian, and Lower Emsian. The Pridolian fauna shows northern European affinities. Thus, the Meguma terrane probably belonged to the North Atlantic domain, as for the Avalon terrane, and occupied a southern position in the "Euramerica" plate during this period. The Devonian fauna belongs to the "old world realm" and shows north Gondwanian and Rhenish affinities. As early as the Lochkovian, species known from both the Rhenish and north Gondwanian domains are recognized in Meguma, as well as others reported so far only from northwestern Africa, Iberian Peninsula, and (or) Armorican Massif. The presence of Rhenish fauna confirms the postulated location for the Meguma terrane during the Upper Silurian since this fauna is representative of southern Baltica marginal areas in Europe. On the other hand, the presence of north Gondwanian fauna implies close relationships with western European margin of Gondwana. The lack of a wide oceanic gap separating north Gondwana and Euramerica can explain the faunal exchanges during Lower Devonian times between western Europe and easternmost Appalachian province despite the presence of a physical barrier.

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The biostratigraphic significance of selected uppermost Famennian (Upper Devonian) and lower Tournaisian (Mississippian) brachiopod genera, belonging to the orders Rhynchonellida (e.g. Araratella), Spiriferida (e.g. Sphenospira, Prospira), Spiriferinida (Syringothyris) and Productida (except Chonetidina), is discussed. Owing to the difficulties of identifying productidine and strophalosiidine genera, in contrast to rhynchonellides and spiriferides, the biostratigraphic potential of the former has generally been overlooked. Brachiopods flourished in neritic environments that were unfavourable for conodonts and ammonoids. In the absence of the latter traditional marker fossils, they are potentially important for locating the Devonian–Carboniferous boundary in shallow water depositional settings in conjunction with rugose corals and foraminifers. On a worldwide scale, further work is required to reach a better assessment of the aftermath of the Hangenberg biological Crisis on brachiopods, notably in revising the faunas from the classical areas of the Famennian and Tournaisian stages in Western Europe.

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The specific biodiversity of stromatoporoids, tabulates and brachiopods from the Ardennes (707 taxa) has been analyzed stage-by-stage from the Lochkovian up to the Famennian. The diversity of each group may be correlated with external factors (e.g. facies), but it varied individually (e.g. decline of brachiopods in the Givetian). The faunas are discussed at the order level, however some more diversified orders are analyzed at family level. Biodiversity shows a single peak centered on the Givetian for the bioconstructors, and two major peaks (Emsian-Eifelian and Frasnian) for the brachiopods. The most diversified orders are Stromatoporellida (stromatoporoids), Favositida (tabulate corals) and Spiriferida (brachiopods). Stromatoporoids display two, tabulate corals four and brachiopods five stages of renewal of fauna.