284 GEOLOGY OF ILLINOIS. 



rocks, they presented that peculiar ground, and striated appearance, commonly 

 referred to the action of glaciers. 



North of this there are no outcrops till we reach the southwest quarter of 

 section 8. In section 5, on the Malay and Russ branches, the rock again 

 appears. The most extensive quarry in this section is in the southwest quar- 

 ter, on the farm of Mr. Malay. An ahundant supply of good building material 

 can be had here. 



Along Fall creek, there are exposures for two or three miles from its mouth. 

 The rock has been most extensively worked in the north part of section 4. It 

 is light-colored and compact. In township 12, range 4, sections 27 and 28, 

 there are other outcrops of these beds. The strata as exposed here, commenc- 

 ing below the drift, gave 



FEET. 



1. Thin-bedded sandstone 2 



2. Limestone, containing thin beds of clay, and towards the top some chert 12 



Some of the less common crinoids were comparatively abundant at this local- 

 ity, and the rock here is mostly thick-bedded, light-colored, and when free from 

 chert, it makes good lime. 



The most northerly exposure of the Burlington is in section 18, on the west 

 and northwest sides of Bald bluff. Only about twenty feet are to be seen at this 

 point, and the whole mass is thin-bedded, seldom over a foot in thickness, and 

 is composed of brown arenaceous limestone and sandstone. Bald bluff is a little 

 over two hundred feet high. From here the bluff runs back for several miles 

 in nearly an easterly direction. The Burlington limestone, though not exposed 

 north of here, may exist in the bluffs for some distance, where it probably 

 thins out. 



Fossils. The beds of this limestone exposed in Henderson county probably 

 belong, for the most part, to the upper Burlington division of the group, for at. 

 nearly every outcrop I obtained more or less crinoids, all of which have been 

 identified as belonging to the upper Burlington. These beds are exceedingly 

 rich in fossils, particularly crinoidea. Along the northern shores of the lower 

 carboniferous ocean these "stone lilys" flourished in much greater profusion 

 than in any other known region ; and nowhere else have their remains been 

 found in such abundance, or so finely preserved, as in this rock. Though but 

 part of the beds are found in this county, many species have been already ob- 

 tained, and new ones are still being found. Other fossils, though not as 

 numerous, are abundant, particularly brachiopods. Bryozoa are also found 

 here, but not as abundantly as in the Keokuk rocks. Teeth and spines of fish 

 are not uncommon. 



Among the crinoids found are Actinocrinus multiradiatus, A. asterius, Batocri- 

 nus rotundus, B. oblatus, B. Christyi, B. wquibrachiatus, B. pyriformis, B. Verne- 

 uilianus, B. Nashville. B. Konincki, B. Hageri, Strotocrinus cegilops, S. liratus. S. 



