Odontornithes: a Monograph of the Extinct Toothed Birds of North America

Abstract

WEST from the valley of the Mississippi the stratified formations which underlie the prairie region spread over thousands of square miles nearly as horizontal as when they were deposited. Here and there they have been ridged up into anticlines, now deeply trenched by denuding agents, or have had wedges of the ancient Archæan rocks thrust through them, along the flanks of which their upturned beds can be examined in detail. Hence in spite of their prevalent flatness opportunities are afforded for tracing their stratigraphical succession from top to bottom. They reach a maximum of thickness of some seven or eight miles. Yet throughout this vast depth of strata the unconformabilities seem to be nearly all of local and unimportant character. The several geological systems follow each other continuously, and generally in such a sequence of insensible gradation as to show that geological history in that part of the globe was marked by comparatively few great and destructive geographical revolutions. The record of this history remains in an almost unbroken series of strata from the Primordial zones up into the older Tertiary formations.

Odontornithes: a Monograph of the Extinct Toothed Birds of North America.

By Prof. O. C. Marsh Yale College. Vol. I. of Memoirs of the Peabody Museum of Yale College, New Haven, Conn., and Vol. VII. of the Geological Exploration of the 40th Parallel.