Silicified specimens of 26 genera of early Middle Ordovician (Chazyan) ostracodes occur in two sections of the lower Esbataottine Formation in southwestern District of Mackenzie . Many of these ostracode genera are widespread in the upper Tulip Creek - lower
Bromide formations of Oklahoma; the upper New Market - Lincolnshire - lower Edinburg formations of Pennsylvania and Virginia; and the Day Point - Crown Point - lower Valcour formations of New York. By means of a bathymetric succession of trilobite biofacies already proposed for plat{ orm carbonate
strata of the lower Esbataottine Formation, a shallow-water widespread ostracode assemblage I (=Bathyurus-Isotelus bi of acies) and a deeper water ostracode assemblage II (=Calyptaulax-Ceraurinella - proximal Dimeropyge bi of acies) may be distinguished . These ostracode assemblages occur with some
modification elsewhere in North America and may be used for the first time to indicate the relative bathymetry of comparable faunas from widely separated segments of the early Middle Ordovician North American continental platform . Five new genera (Palaeocopida: Eurybolbina, Nahanniopsis,
Canadabolbina, Valcouropsis; Podocopida: Bolboscapha) and twelve new species are erected. In addition, taxonomic revisions and observations are presented for some previously incompletely known North American Chazy ostracode species and for those taxa observed during the study that may have
affinities with Middle Ordovician ostracode faunas from Europe. At present, faunas from both regions require additional detailed study before intercontinental biogeographic considerations may be attempted
The 200- to 300-foot-thick Ellis Bay Formation on Anticosti Island has yielded a well preserved and distinctive ostracode fauna. This fauna is closely related to that of the underlying Vaureal Formation and contains elements common to the Porkuni beds of Estonia
and the Dalmanitina Series (5a, 5b) of Norway. The Late Ordovician age of these faunas is indicated.
Strata of Middle Silurian age from Lake Timiskaming, Ontario and Quebec contain numerous diverse fossils. One hundred and thirty-five taxa are listed and ninety-three illustrated in this report. Some comparative fossils from Middle Silurian formations of the
Michigan Basin are also illustrated. Strata of older Silurian age occur in the subsurface of the Lake Timiskaming area; these have not yet yielded fauna of proved stratigraphic value .
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