y6 THE HABITAT OF THE EURYPTERIDA 



desired to show that the eurypterids from the earliest times lived in 

 terrestrial waters, for the Belt terrane has been shown by Barrell 

 from purely lithological evidence to be non-marine. From the pres- 

 ence of mud-cracks and other structural characters of the formation 

 he concludes that the terrane gives evidence of "two sedimentary 

 cycles, each of which contains a strongly marked formation of mud- 

 cracked red shales, the shales alternating with sandy strata, and 

 both judged to have been deposited on the flood plains of rivers, whose 

 deltas had gained over the subsidence, finally filling up and dis- 

 placing the shallow epicontinental sea" (14, 319, 320). 



2. THE NORMANSKILL AND SCHENECTADY BEDS 



The Normanskill sandstones and shales of Catskill and the Schen- 

 ectady bluestones of Schenectady, New York, are so similar litho- 

 logically and faunally that they may be considered together. Com- 

 paratively little is known concerning the details of distribution of 

 these formations and their physical changes from place to place, yet 

 the descriptions available and the studies I have been able to make 

 in the field, make clear what must be the origin of the sediments. In 

 reference to the Normanskill beds Clarke and Ruedemann make the 

 following statement: 



"The lithologic and faunal conditions at the Broom street quarry 

 exposure were found to be a singularly complete duplication of those 

 of the eurypterid-bearing exposures in the bluestone quarries at 

 Schenectady. The Broom street quarry is also a bluestone quarry, 

 the rock being mostly used in the crusher. The courses of 'bluestone' 

 (here an impure argillaceous sandstone) are very compact, from 3 to 

 30 feet thick between the intercalations of black shales. There is 

 distinct evidence of shallow water conditions, one bed being con- 

 glomeratic and largely composed of pebbles, many of which appear 

 to be mud pebbles; another beautifully exhibiting very regular, widely 

 separated wave marks with winnows of comminuted seaweeds and 

 eurypterids in the troughs. 



"Quite as in the bluestone quarries of the Schenectady beds, the 

 surfaces of some of the sandstones are densely covered with rather 

 poorly preserved seaweeds and eurypterids. It was therefore natu- 

 ral to expect that here too the black intercalated shales would contain 

 better material of these fossils and possibly also graptolites that would 

 indicate the age of the beds. They have indeed afforded a layer with 



