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character. The blue shale, on the contrary, frequently contains numerous 

 concretions, and great abundance of thin layers of gypsum and crystals of the 

 same. Near Sheridan, concretions and septaria are abundant. In some 

 places, the latter are of great size, and, being imbedded in the stratum, have 

 suffered denudation of their contents, and the septa, standing out, form a huge 

 honey-comb. This region, and the neighborhood of Eagle Tail, Colorado, are 

 noted for the beauty of their gypsum-crystals, the first abundantly found in 

 the Cretaceous formation. These are hexagonal-radiate, each division being 

 a pinnate or feather-shaped lamina of twin rows of crystals. The clearness 

 of the mineral and the regular leaf and feather forms of the crystals give 

 them much beauty. The bones of vertebrate fossils preserved in this bed 

 are often much injured by the gypsum-formation, which covers their surface, 

 and often penetrates them in every direction. 



"The yellow bed of the Niobrara group disappeai's to the southwest, west, 

 and northwest of Fort Wallace, beneath a sandy conglomerate of uncertain 

 age. In color, it is light, sometimes white ; and the component pebbles are 

 small and mostly of white quartz. The rock weathers irregularly into holes 

 and fissures, and the soil covering it is generally thin and poor. It is readily 

 detached in large masses, which roll down the bluffs. No traces of life were 

 observed in it ; but it is probably the eastern margin of the southern extension 

 of the Miocene Tertiary stratum. This is at least indicated by Dr. Hayden in 

 his Geological Preface to Leidy's Extinct Mammals of Dakota and Nebraska. 



"Economically, the beds of the Niobrara formation possess little value 

 except when burned for use as a fertilizer. The yellow chalk is too soft in 

 many places for large buildings, but it will answer well for those of moderate 

 size. It is rather harder at Fort Hays, as I had occasion to observe at their 

 quarry. That quarried at Fort Wallace does not appear to harden by ex- 

 posure ; the walls of the hospital, noted by Leconte on his visit, remained in 

 1871 as soft as they were in 1867. A few worthless beds of bituminous 

 shale were observed in Eastern Colorado. 



"The only traces of glacial action in the line explored were seen near 

 Topeka. South of the town are several large, erratic masses of pink and 

 bloody quartz, whose surfaces are so polished as to appear as though vitrified. 

 They were transported, perhaps, from the Azoic area near Lake Superior." 



The following species of Vertebrata have thus far been detected in the 

 Niobrara formal ion : 



