New pteraspididae (agnatha, heterostraci) from the lower devonian of Northwest Territories, Canada

Three new genera of pteraspidids from Arctic Canada improve the known distribution of the family beyond Europe, Spitsbergen and eastern Canada where they have biostratigraphic value. Stegobranchiaspis baringensis, S. baringensis var. falcata, Unarkaspis schultzei and Escharaspis alata from the Peel Sound, Drake Bay and Snowblind Bay formations of Prince of Wales and Cornwallis Islands, N.W.T., are medium-sized to large pteraspidids with distinctive proportions of probable adaptive significance. Faunas containing these pteraspidids provide a local correlation between the basal Snowblind Bay Formation and upper members of the Peel Sound and Drake Bay formations. Associated conodonts indicate a late Gedinnian to Siegenian age for the fauna, and comparison with successions elsewhere suggests an equivalence with the "vogti" horizon in Spitsbergen and the "crouchi" zone of the Anglo-Welsh succession.