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PALAEONTOLOGY OF ILLINOIS. 



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boniferous limestone series in Illinois, and from these the new 

 species now introduced to the notice of the scientific world 

 were mainly obtained. 



The Kinderhook group, consisting mainly of argillaceous and 

 arenaceous beds, which form the base of the Carboniferous 

 system in Illinois, has afforded but few of these ichthyic fossils, 

 but on ascending to the Burlington limestone we -find them 

 more abundant; and in the upper part of this limestone occur 

 the lowest beds that contain these remains, in any considerable 

 numbers. In the upper part of this limestone we find a single 

 stratum of brownish-gray rock, from four to six inches thick, 

 in which the teeth and spines of fishes are imbedded in great 

 numbers. This fish led was first observed at Quincy, Illinois, 

 and was subsequently identified, occupying apparently the same 

 horizon, on Honey creek, in Henderson county, and at Augusta, 

 in Iowa, points nearly a hundred miles away from the first 

 named locality, showing that the cause which produced this 

 general destruction among the vertebrated animals of this 

 period was not local, but operated simultaneously over a wide 

 geographical area. At Quincy there is a seam of green shaly 

 clay, about two inches thick, interstratified with the lime- 

 stone, beneath which, upon the surface of the underlying rock, 

 the remains of fishes were found in considerable numbers, as 

 though the animals had been destroyed' suddenly by the intro- 

 duction of this muddy sediment into the ocean. As this has 

 not been observed at any other locality, it may, perhaps, be a 

 merely local phenomenon. 



The second fish led is situated some fifty or sixty feet higher 

 in the series, and is near the base of the quarry rock of the 

 Keokuk group. It has only been identified at a single locality 

 in the vicinity of Hamilton, in Hancock county. The rock is 

 a single stratum of soft, granular, crinoidal limestone, and its 

 friable character is probably in part due to surface exposure. 

 It is about four inches thick, and crumbles readily, under a 



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