132 GEOLOGY OF ILLINOIS. 



Caiitocrinus. A half a mile west of this point, in the northeast quarter of 

 section 36, of the adjoining township, the same limestone is said to have been 

 met with at the depth of four feet. 



About five miles due north of this locality, in the northwest quarter of sec. 1, 

 on Mr. Watson' Convers's place, a bed of limestone rock was struck in two 

 separate places, in digging wells, in one at the depth of only five and a half 

 feet below the surface. A few flakes of the stone were turned up and were to 

 be seen on the surface at the time of my visit ; a rather even textured, light 

 drab or buff limestone, containing imperfect casts of Pentamerus. . If this lime- 

 stone is here in place, and judging from the account of Mr. Convers, I think it 

 quite probable that it is, it may, perhaps, belong to a considerably lower hori- 

 zon than that of the other localities in the district. In general appearance, the 

 specimens of the stone which were seen were not very different from some of 

 the beds exposed on the Fox river, in Kane county, which were there referred 

 to the lower part of the group. 



The only remaining locality where the beds of this age have been exposed at 

 the surface, is in the northeast corner of section 17, township 44, range 9 ; and 

 nearly on the county line between McHenry and Lake counties. The lime- 

 stone is here seen in the sides and bottom of a shallow excavation on the road- 

 side, about ten or fifteen feet in diameter. In general appearance and texture, 

 it is the same as that at Mr. Rawson's, except that at this point, being some- 

 what more exposed to atmospheric and other wearing influences, it is softer 

 and more disintegrated. No well preserved fossils are contained in this rock; 

 a few imperfect casts of corals and crinoids, and a single specimen of StropTio- 

 mena rhomboidalis were only obtained. 



At a place called the Sand Hills, on the Kishwaukce, in the southwest part 

 of section 21, township 44, range 6, a bed of limestone was reported to have 

 been struck at the depth of fourteen feet below the surface. This, also, proba- 

 bly belongs to the Niagara group, as we have no reason to infer that the other 

 formations extend so far to the eastward. 



Cincinnati Group. This formation, as nearly as we are able to judge, un- 

 derlies a narrow strip of territory running nearly due north and south, near 

 the western border of this district. Its exposures are restricted to one locality, 

 about two miles east of G-arden Prairie Station, on the Chicago and North- 

 western railway, Galena division, and about a quarter of a mile south of the 

 main wagon road, between that place and Marengo. It is here extensively 

 quarried, the excavations being twelve feet or more in depth. The rock is a 

 thin bedded, buff limestone, having frequently a slight bluish tinge, and con- 

 taining much chert in some parts of the quarry. In general appearance, it is 

 very similar to some of the lower beds of the Niagara, to which group I was at 

 first inclined to refer it. Fossils appeared to be scarce, only a few imperfect 

 fragments were obtained. 



