Barbour — Carboniferous Eurypterids of Nebraska. 507 



Art. XLV. — Carboniferous Eurypterids of Nebraska; by 

 Erwln H. Barbour. 



During the field season of 1912 the Nebraska Geological 

 Survey found a bed of eurypterids about one mile south of 

 Peru. This adds one more to the list of known eurypterid 

 localities, and adds one form believed to be new. Nowhere 

 apparently are eurypterids found in such variety and in such 

 excellent preservation as in New York State, yet the Nebraska 

 beds bid fair to make an unusual showing numerically. 



The eurypterid shales of Nebraska, as far as known, outcrop 

 one mile south of Peru, in the Coal Measure bluffs facing the 

 Missouri River. The alternating limestone and shale in the 

 bluffs at the edge of the town change rapidly to shale, which 

 becomes increasingly arenaceous and merges finally into massive 

 sand some forty to fifty feet thick about a mile south of Peru. 

 Here the eurypterid bed is found. The walls and bluffs are 

 vertical, because only recently they were deflection banks of 

 the Missouri River. The tracks of the Burlington Railroad 

 run close to the base of the bluffs. About ten feet above the 

 tracks, and about thirty feet above the river level, may be 

 noticed in the massive sand a distinct shaly band scarcely a foot 

 thick, and two to three hundred feet long. This local band is 

 composed of thin, irregular, shaly layers, seldom a half inch 

 thick, alternating with micaceous sand. The shale seams in 

 the topmost two inches yield the eurypterids. These thin 

 shale seams cleave readily, exposing the eurypterids and 

 numerous associated plants. Because of shrinkage joints, the 

 shales tend to break into rather small blocks, and unfortunately 

 many good specimens are damaged or destroyed. 



Since removing a dangerous overhanging ledge the work 

 of collecting has been rendered quite safe and easy, and 

 about forty specimens were found on as many square feet 

 of shale, or approximately one to each square foot. Their 

 chitinous shells are reduced to mere carbonaceous films some- 

 times scarcely distinguishable from the shaly matrix. Accord- 

 ingly, some specimens are faint. Others are distinct, however, 

 and well differentiated from the slate-colored background. 

 Some specimens are so well preserved that the details of the 

 gross anatomy may be made out, and even some of the 

 ornamentation and minute sculpturing. 



Associated with the eurypterids at Peru are innumerable 

 leaves, stems, and fragments of certain land plants, con- 

 spicuously Neuropteris pinnules, stems of Calamites, and leaf- 

 whorls of Asterophyllites. The last mentioned add to the 

 beauty of some of the specimens in our collection, because the 



Am. Jour. Sci.— Fourth Series, Vol. XXXYIII, No 228. — December, 1914. 

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