TUE FOKT riEREE SHALES. 87 



sota River about 15 and 30 miles northwest of Xew Ulni, referred by Prof. 

 N. H. Wincliell to the Fort Benton formatioii; similar deposits about 70 

 miles farther north, on the Sauk River in Steams County, identified ns this 

 formation by Meek ; and shales, with layers of concretionary limestone, in 

 the Minnesota Valley, at the mouth of the Cottonwood, close to New Ulm, 

 which Professor Wiuchell refers provisionally to the Niobrara formation. 

 In the western outcrops on the Cottonwood, lignite-bearing shales and the 

 sandstone containing impressions of leaves occur together, and the same is 

 true of the shales with limestone and the leaf-bearing sandstone at the 

 mouth of this river; so that possibly all these beds on the Cottonwood and 

 Minnesota rivers may belong to one formation, which must then be the 

 Dakota, according to Lesquereux's determinations of its fossil leaves. 



There is evidence, however, that the ocean extended east nearly across 

 Minnesota in later stages of the Cretaceous period, for Cretaceous fossils 

 and shale have been found in the glacial drift, apparently not far removed 

 from their (iriginal beds, at Lime Springs, Iowa, less than 5 miles south 

 from the south line of Fillmore County, Minn., including sharks' teeth 

 closely like Otodiis appendiculatus Ag., bones, teeth, and scales of teleost 

 fishes, Ammouites (two species), Ostrea, Inoceramus, etc., regarded by Dr. 

 C. A. White as Upper Cretaceous, "as late as any yet recognized in any 

 part of North America."^ A hundi-ed and seventy-five miles northwest 

 from this localitv a perfect tooth of Ofodus appendiculatus Ag. has been 

 found on a sand bar near tlie mouth of Two Rivers, tributary to the 

 Mississippi, in Morrison County, Minn. Other sharks' teeth and fragments, 

 belonging to different species, have also been found in that vicinity and 

 on the south branch of Two Rivers, in Stearns County, at a distance of 

 about S miles to the southwest. These indicate that marine Cretaceous 

 beds, probably of the same age with the fossils at Lime Springs, underlie 

 the drift somewhere in central Minnesota; though it is possible that they 

 have been wholly eroded, their fossils being now contained in the drift. At 

 the mouth of Two Rivers, fresh-water shales, probably of similar middle 

 Cretaceous age witli the lignite-bearing beds of the Sauk and Minnesota 

 rivers, are exposed tij the height of a few feet above the level of the 



' Proo. A. A. A. S., 1872, Vol. XXII, pp. 187-192. 



