IOWA, AND WAPSINONOX RIVE II S. 



87 



and interrupts the continuity of the strata for the distance of about fifty paces. 

 On crossing this hollow, a soft brown sandstone, several feet thick, with vegetable 

 impressions, is exposed, in a low arch, fifteen feet lower than the top of the limestone. 

 This appears to be another outlier of coal sandstone, so frequently met with in this 

 portion of the Iowa River ; which, by a fault or slip of the beds, has sunk into a 

 depression. Thirty paces beyond the sandstones, up stream, the white limestone is 

 again in place, at nearly the same elevation as the sandstones. In the two adjacent 

 exposures of limestone there are no intercalations of sandstone. 



About two miles and a half from Iowa City, on Section 36, Township 80 north, 

 Range 6 west, of the 5th Principal Meridian, a schistose, marly limestone, about 

 twenty feet thick, is exposed on the east bank of Rapid Creek, opposite Falkner's Mill, 

 surmounted by a decomposing bed, from which loose corals of the following genera 

 and species have become detached, and lie scattered on the surface : IAtliostrotimt 

 hexagonum (?), L. ananas, OyatTbojphyllwm turbinatum, G. ceratites (?), C. dianthus (?), 

 C. vermiculare (J) , Cystijjhyllum Devoniensis, Chcetetis (species undetermined), and 

 Favosites polymorpha. The beds beneath contain chiefly shells of the following 

 species : Terebratula reticularis, Orthis resupinata, Spirifer euruteines, and Terebra- 

 tula concinna (?) . 



On the same creek, on Section 30, Township 80 north, Range 5 west, of the 5th 

 Principal Meridian, sandstone with vegetable impressions occurs, in a similar position 

 with reference to the coralline limestone as near Iowa City. 



On Section 4, Township 79 north, Range 6 west, of the 5th Principal Meridian, 

 two or three feet above the level of the Iowa River, limestone is found containing: 

 coralline beds similar to those near Iowa City ; the latter extending to the height 

 of from twelve to fifteen feet. 



In ascending the Iowa, the above-described limestones occur at intervals for the 

 distance of about twenty miles, by the meanders of the river, and twelve to fourteen 

 miles in a direct line. 



The principal exposures are as follows : Near the line between Sections 32 and 

 33, Township 80 north, Range 6 west, of the 5th Principal Meridian, on the west 

 side of the river; above, and below the mouth of Newcomb's Creek, on Sections 33 

 and 34, same township and range, on both sides of the river, having a slight westerly 

 dip ; on Section 27, Township 80 north, Range 6 west, in a cliff of about 27 feet, 

 on the left bank, where the strata dip 3° or 4° to the southwest. Here some of the 

 beds are full of fossil shells, viz. : Terebratula aspera (very abundant), Terebratula 

 reticularis (large variety), Orthis resupinata, Spirifer euruteines; Spirifer with a 

 highly extended cardinal area, measuring sometimes five inches from angle to angle, 

 which we have described in the Appendix; Leptena (sp. ?), Pliacops macrophthalma , 

 several reticulated lamelliferous corals, Cyathophyllum ceratites (?) . It is at this locality 

 that much of the rock used in the construction of the State House has been pro- 

 cured. The lower beds are rather schistose, but the upper are more solid and 

 substantial, and may be obtained in blocks of from nine inches to two feet. The 

 upper eight feet contain but few fossils. 



On the opposite side of the river, on Section 22, same township and range, rocky 

 ledges, of from thirty to forty feet in thickness, are exposed for three-quarters of a 



