CARBONIFEROUS AGE. 163 



At and near Des Moines there is no millstone grit such as is 

 found at this horizon farther east, and therefore the lower coal beds 

 rest, as White and Meek have observed, on the sub-carboniferous 

 rocks. West of the Des Moines River, as also shown by these ge- 

 ologists, the coal measures belong to a higher geological horizon, 

 and most probably to the middle series, though there is no serious 

 palasontological or physical break between these and the lower 

 rocks of this age. On going southwestward from the Des Moines, 

 in the deep valley of Middle River, which lies about two hundred 

 and fifty feet below the plain, the rocks here dipping slightly to- 

 wards the southwest. Here the increasing thickness of the upper 

 coal measure beds can be distinctly seen. The upper bed of the 

 middle series is last seen at Winterset, at the very bottom of the 

 valley, and all the beds above for two hundred and fifty feet belong 

 to the still higher series, consisting largely of heavy beds of light 

 yellow limestone, sandy micaceous shale, black laminated shale, 

 blue, drab and reddish clays, and occasionally a few inches of im- 

 pure coal. In these upper beds are found almost identically the 

 same fossils as on the Nebraska side of the Missouri. Amon<r 



o 



these is the curious fossil {Fusilina cylindrical), which is so often 

 mistaken for fossil rice or w T heat. Twenty-three additional fossils 

 are characteristic of these two sections. On leaving this valley, no 

 more exposures of the middle series are visible, the inclination of 

 the strata towards the southwest taking these beds below the deepest 

 eroded valleys. At various points, however, between this place and 

 the Missouri, opposite Plattsmouth, the upper beds are exposed, and 

 can be readily identified by their contained fossils. Dr. White, also, 

 who made a critical examination of the whole region, is confident 

 that he can identify the upper members of the Winterset exposures 

 in the Missouri bluffs on the Iowa side between Nebraska City and 

 Plattsmouth. However that may be, there is no doubt, judging 

 from the evidence of fossils, and the physical character of the rocks, 

 that the series on both sides of the Missouri, between the south line 

 of the State and Omaha, belongs to the upper series of the coal 

 measures. According to Dr. White, the nearest visible series of the 

 middle coal measures to the Missouri is at a point in Iowa nearly 

 due east from Blair, at a distance of about sixtv miles. Having 



*/ o 



also myself gone over and carefully examined these exposures, the 

 conviction was forced on me that White and Meek are proximately 

 correct in their determinations of the horizons of these rocks. It is 

 therefore definitely established that on the Nebraska side, as far as 



