The mountain structures originated in three great orogenic periods, the earliest in the Archean, the second at the end of the Palaeozoic and the third at the end of the Mesozoic. The Archean mountain chains, which enclosed the present region of Hudson Bay, were so ancient that they had already been worn down almost to a plain before the early Palaeozoic sediments were laid down. [Please select]
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The species _pulcher_ probably differentiated from the remaining _lineatus_ stock during the Early Pleistocene orogenic upheaval in Guatemala. [Please select]
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