30 GEOLOGY OF ILLINOIS. 



tain Orthis Michelini, Euomphalus latus, Spirifer Grimesi, and S. imbrex. The 

 pygidium of a beautiful Trilobite was found in these lower beds, near Kinder- 

 hook, to which the name, Phillipsia tuberculata has been given. From the 

 north line of the county, southward, to a point about ten miles below Atlas, this 

 limestone forms the upper portion of the bluff at most of the points examined, 

 and from thence it trends eastwardly across Six Mile creek to the waters of Bay 

 creek, and caps the bluffs on the eastern side of that creek, at the south line 

 of the county. It outcrops on all the small streams south of Pittsfield, and is 

 extensively quarried on Big Blue creek, about four miles southeast of there, for 

 building stone for the supply of the town and adjacent country. 



On the eastern side of the county, the most northerly outcrop of this lime- 

 stone is in the vicinity of Griggsville Landing, where the cherty beds of the 

 upper division of this rock are exposed at the base of the bluff. The outcrop 

 is here about fifty feet in thickness, and so far as it is exposed in the quarries 

 opened, the rock consists of alternations of thin bedded, gray limestones, with 

 seams of chert. The cherty material is also disseminated through the limestone 

 strata, in nodules and concretionary masses of considerable size. From this 

 point to Montezuma, this limestone forms a low bluff, seldom rising more than 

 fifty feet above the level of the adjacent bottom lands. At Montezuma, where 

 several quarries have been opened in this rock, the beds exposed are about fifty 

 feet in thickness, the lower ten feet being a massive gray limestone, compara- 

 tively free from chert, while the remaining portion consists of thin bedded, 

 brownish gray crinoidal limestone, with considerable cherty material in seams 

 and nodules. Fossils are quite abundant, and among others not yet determined, 

 the following species were collected here : Spirifer striatus, S. Grimesi, S. im- 

 brex, Productus punctatus, P. semireticulatus, Strophomena analoga, Orthis 

 Michilini, Euomphalus latus, Lyropora retrorsa, Evactinopora grandis, E. sex- 

 radiata, Agaricocrinus planoconvexa, Platycrinus planus, and several species of 

 Actinocrinus. From Montezuma to Bedford, this limestone rises rapidly, and 

 the bluffs immediately north of Bedford are at least one hundred and fifty feet 

 in hight, and consist mainly of this limestone, capped with a few feet of Loess. 

 Just below Bedford, the underlying shales appear at the base of the bluffs, and 

 from thence to the south line of the county, the bluffs range from one hundred 

 and fifty to two hundred feet, or more, in hight, the upper escarpment consist- 

 ing of a hundred feet, or more, in thickness, of Burlington limestone, while 

 the talus below covers the shaly beds of the Kinderhook group. 



On Bay creek, this limestone is well exposed, and forms the main portion of 

 the bluffs along this stream, from the vicinity of Pittsfield to the point where 

 it intersects the river bluffs, about two miles above the Calhoun county line. 

 It is the most important of all the limestones exposed in this county, whether 



