CALHOUN COUNTY. 11 



of Hamburg, and has afforded the following species: Rynchonetta pustulosa, 

 Spiriferina subtexta, Leda fiarrisi, and a Terebratula resembling T. hastata. 

 On the eastern side of the county we found an oolitic rock exposed on Mr. 

 Whitaker's place, northwest quarter of section 27, town 8 south, range 2 west, 

 which probably should be referred to this horizon. The lowest rock seen at 

 this point is a blue argillaceous shale, with some thin layers of limestone 

 strongly impregnated with the sulphuret of iron. This shale was overlaid by 

 a bed of oolitic conglomerate, closely resembling that found at Rockport in Pike 

 county. It is here from four to five feet in thickness, one-half of which con- 

 stitutes but a single layer, and the remainder is in thin beds, from two to six 

 inches thick. This was the only point where we found it exposed on the east- 

 ern side of the county. 



These oolitic beds are generally succeeded by argillaceous and sandy shales, 

 which vary in thickness from forty to eighty feet, and are argillaceous at the 

 base and arenaceous at the top, passing into shaly gritstones. These beds 

 contain but few well marked fossils in this county, except a large fucoid, like 

 the Cauda Galli of the New York corniferous beds, which is quite abundant 

 in the shaly gritstones of this group. Its occurrence in these beds has been 

 urged as an evidence of the Devonian age of this formation, but a similar fucoid 

 is found high up in the Coal Measures in Illinois, and hence no satisfactory 

 conclusion as to the age of any formation could be predicated upon the occur- 

 rence of this peculiar fossil in it. At Reed's Landing^ in the northeast part of 

 the county, this fucoid is quite abundant in the thin gritstones which form the 

 upper portion of the group in that vicinity. 



At Hamburg the upper beds of this group become calcareous, and form an 

 ash-gray shaly limestone, twenty-five to thirty feet or more in thickness. Some 

 of the beds are magnesian and partly concretionary in their structure, and con- 

 tain a few fossils, among which are Strophomena analoga, Euomphalus latus 

 and Producing semireticulatus. It may be that these magnesian and shaly 

 limestones are the stratigraphical equivalents of the lower division of the Bur- 

 lington limestone, but they contain very few crinoidal remains here, and these 

 are generally too fragmentary to be specifically determined. 



About three-quarters of a mile north of Brussels, there is an outcrop, just 

 above the level of the Illinois bottoms, of a striped purple and green oolitic 

 conglomerate. The quarry exposes about four feet in thickness of the rock, 

 which lies in thin beds from two inches to a foot in thickness. It is overlaid 

 by about three feet of fine grained limestone, apparently the equivalent of the 

 so called "Lithographic" limestone of the Kinderhook group. No similar rock 

 has been found anywhere else in the State, and we are only able to determine 

 the horizon to which it belongs, from its connection with the overlying lime- 

 stone. From its association with that limestone we refer it without hesitation 



