TWENTY-FIFTH ANNUAL MEETING. 109 



St. John, in his report for 1885, where he shows that the exposure of the character- 

 istic leaf-bearing Dakota sandstones in the extreme southwest is at least 1,100 feet 

 higher than at Lamed, in Pawnee county, or 1,700 feet higher than in Saline county; 

 observations quite in accord with my own. 



In Lane county, south of Dighton. on the head waters of the Walnut, I deter- 

 mined the Niobrara cretaceous. In all probability there is a small outcrop of the 

 same on the head waters of Pawnee Fork, and possibly also north of Coolidge. 

 Professor Hay tells me that there is a small outcrop on the White Woman, in Gree- 

 ley county. I believe that these are the southernmost outcrops of the formation in 

 the State. The Benton probably occurs furthest south in the longitude of Meade 

 county, where St. John and Hay have determined rocks of a more recent age than 

 the Dakota. 



There is a very interesting problem in this connection. In Professor St. John's 

 report, he says (page 145) the Niobrara rocks of the southwest "consist of only a 

 few feet thickness, of light, creamy, buff chalky limestones, in rather even layers, 

 from a few inches to a foot thick, and in places charged with Inoceramus problem- 

 aticus, another large, thin-shelled, undetermined species, and remains of bony fishes, 

 such as characterize the Niobrara formation in the region to the north and north- 

 east. . . . Similar exposures occur on north-side tributaries of Crooked creek, 

 in the southwest part of Ford county. The limestone at the latter localities has 

 also been quarried to a limited extent, and it affords the same species of fossils. 

 These occurrences are identical with those on Sawlog creek, north of Fort Dodge, 

 and in the valley of Pawnee Fork, in Hodgeman county. . . . The heavy lime- 

 stone deposit that forms the upper horizon of the Benton, of the Smoky Hill, is ap- 

 parently wanting in this southwest region." 



Six miles south of Rush Centre, I found a similar deposit, less than 50 feet in 

 thickness, lying upon undoubted Benton rocks, and covered by the tertiary of the 

 summit of the divide. At the time of my visit, I had no doubts of its Niobrara char- 

 acter, and later Niobrara as well. It showed the same chalky shales, numerous 

 specimens of small shells, and fragments of weathered fish bones. I was exceed- 

 ingly surprised a few days later to discover the massive, chalky limestone less than 

 20 miles north, on Timber creek. Further, this limestone undoubtedly occurs on 

 the Walnut; Mudge says that it occurs on the Pawnee, and I found it north of Cool- 

 idge. In other words, it runs uninterruptedly through the State, and, without doubt, 

 St. John's outcrop, as well as that of Rush county, are earlier. We have much to 

 learn of the Benton in Kansas, and, I believe, many interesting results to obtain. 



The divisional line between the Benton and Niobrara I take at the top of the 

 stratified beds already mentioned, following Mudge. But I am not at all certain 

 that it should not be placed below this, or even below the subjacent dark-blue shale. 

 Its chief distinction is its firmer texture, its comparative barrenness in fossils, and 

 its well-marked lines of stratification. Its invertebrates are much more like those 

 of the Niobrara than those of the more yellow limestone below. These fossils, how- 

 ever, are much more broken up and much less numerous. Immediately overlying 

 this, and conformable with it, is found the true chalk of the Niobrara. In micro- 

 scopic structure, the chalk, whether from the highest or the lowest of the outcrops, 

 seems tolerably uniform, and closely resembles the English chalk. The great mass 

 of the material is made up of coccoliths, but with a considerable quantity of both 

 rhabdoliths and foraminifera. In its gross characters, however, there is not a little 

 difference between the upper and lower beds. In the lower portions, the chalk, where 

 exposed, is white or gray, never deeply yellow, and the shales are of a lighter blue. 

 In the upper portion, the chalk is more yellow, and often shows decidedly buff or 

 reddish tints. It is also here smoother and softer to the touch. There is, also, a very 



