MOUNT STEPHEN ROCKS AND FOSSILS.
By Charles D. Walcott.
The north face and slope of Mount Stephen presents a wonderfully interesting section of rocks in which many finely preserved fossils occur. At the base, where the railroad passes through the north shoulder of the mountain mass, fossils of the Lower Cambrian fauna occur in the hard, brown sandstones and in the bluish-gray limestones and shales above them for 315 feet. The characteristic fossil of this horizon is a large trilobite called Olenellus. No whole ones have been found on Mount Stephen, but an entire specimen found at about the same place in the section in Nevada is shown by Figure 1, Plate II. Above the Lower Cambrian formations comes the massive Cathedral limestone, 1680 feet thick, which forms the summits of Cathedral Mountain. These limestones are sandy and impure and in Mount Stephen only worm borings have been seen in them. Above the Cathedral formation there is a series of thin layers of bluish limestone and shale, 525 feet thick, which is called the Stephen formation. In this may be found many fragments of fossils that belong to the Middle Cambrian fauna. We have now reached the level of the celebrated fossil bed of Mount Stephen. The rock is a gray, siliceous and sandy shale that, 2200 feet above the railroad station at Field, is 150 feet in thickness. A sharp fold in the shale and the rock below has bent the layers sharply down the slope in the direction of Field. The frost, rain and snow have gradually broken up the great layers of shale and scattered them down the slopes. Nature has done all that