i86 Natural History Bulletin. 



facts that have not before been recorded, nor even suspected 

 in connection with Iowa geology. The Cedar Bluffs are made 

 up of Niagara limestone, Hdiolitcs inte7'stincttis, H. megasioma, 

 JLyellia americana, Favosites his-pidiis^ F. niagarensis and other 

 Upper Silurian species are here more or less common. The 

 rocks too have the characteristic color, texture and composi- 

 tion of the Niagara strata in Delaware, Jackson and other 

 counties in which the Niagara limestone has long been known 

 to be exposed. 



Rocks belonging to the lovveV part of the Devonian in Iowa 

 are well developed at Fa3'ette. The same strata are again 

 exposed in the southeast corner of Buchanan county. Omit- 

 ting the irregularities caused by erosion, a line joining the 

 points named, it was supposed, would coincide ver}^ nearly 

 with the Devonian outcrop. Such a line however would pass 

 at least fifteen miles to the east of Fairbank. For the facts 

 as now known, the only explanation thus far suggested, is that 

 after the close of the Niagara period, pz'obably early in the 

 Devonian, an antichnal fold was developed in the neighbor- 

 hood of Fairbank, having a general trend east and west. 

 While this Niagara uplift as we may call it, was not ver}* 

 great, it will be seen, if we draw a line from Fayette to Fair- 

 bank and thence to the southeast corner of Buchanan count}^ 

 that it was sufficient to cause a \&cw pronounced and unex- 

 pected deflection in the line of Devonian outcrop. At Fair- 

 bank the line will be bent at a right-angle. Such a line may 

 be compared with that which marks the eastern edge of the 

 Devonian area in White's Geological Map of Iowa. On the 

 geologic maps of Iowa, Hazelton, ten miles east of Fairbank, 

 lies well within the Devonian area; but at Hazelton as would 

 be expected after the observations made at Fairbank, the 

 exposures are all in the Niagara limestone and Favosites 

 favostcs^ Zaphreniis siokcsi, Thecia minor, and other Niag- 

 ara species were collected in addition to the species found at 

 Cedar Bluffs near Fqiirbank. Near Coytown, about two 

 miles northeast of Hazelton, the upper part of the exposures 



