-tion zone to the limestone. Niobrara about as elsewhere, the three ridges usually showing, the eastern one often making an abrupt slope to the Pierre valley. No Pierre exposed so far as I saw, occupying a rather flat undissected valley. To the east could see Fossil Creek sandstone extending northward from where I traced it yesterday. Niobrara contains I. deformis and O. congesta in about the usual condition as from Boulder northward. Arrived where Owl Canyon breaks through Dakota ridge at 10:45. I got out and the driver went to the Forks to get his dinner and feed the horses. In the upper Niobrara I noticed some tendency toward minor folds where the big ditch cuts through it 4 or 5 miles S of Owl Canyon , but I did not examine the region particularly, merely noting a few dips. At Owl Canyon (mouth of) found great numbers of Ostrea and Inoceramus . The