Jlesozoic and Cauiozoic Geology and Palaeontology. 73 



large scales and other remains of fishes, and numerous specimens of 

 Ostrea congesta, attached to fragments of Inoceramus. Passing down 

 into light 3^ellowish and whitish limestone, containing great numbers 

 of Inoceramus problematicus, I. pseadomytiloides, I. aviculokles, fish 

 scales, etc. Found in the bluffs along the Missouri, below the Great 

 Bend, to the vicinity of Big Sioux River ; also below there on the tops 

 of the hills. Estimated thickness, 200 feet. 



4. Fort Pierre Gronp, consisting of dark beds of very fine unctuous 

 clay, containing much carbonaceous matter, with veins and seams of 

 gypsum, masses of sulphuret of iron, and numerous small scales, fishes 

 local, filling depressions in the bed below. Lower fossiliferous zone, 

 containing Ammonites complexus, Baculites ovatiis, B. coiripressas, 

 Helicoceras mortoni, H. tortum., H. umhiUcatiim, H. cocfileatum, 

 Ptychocey^is mortoni., Fusiis vinculum, Anisomyon borecdis, Amaur- 

 op)sis paludiniformis, Inoceramus subloivis, I. tenuilineatus, bones of 

 Mosasaurus niissouriensis, etc. Middle zone, nearly- barren of fossils. 

 Upper part consisting of dark gray and bluish plastic clays, containing-, 

 near the upper part. Nautilus dekayi, Ammonites placenta, Baculites 

 ovatus, B. compressus, Scaphites 7wdosus, Dentalium gracile, Crassa- 

 tella, evansi, Cuculloia nebrascensis, Inoceramus sagensls, I. nebras- 

 censis, I. vaiiuxemi, bones of Ilosasaurus missouriensis, etc.. Found 

 on Sage creek, Cheyenne river, White river above the Mauvaises 

 Terres, Fort Pierre, and out to Bad Lands, down the Missouri on the 

 high countr3% to Great Bend and near Bijou Hill on the Missouri. 

 Estimated thickness, 700 feet. 



5. Fox Hills Group, consisting of gray, ferruginous and yellowish 

 sandstone and arenaceous clays, (^ontammg Belemnitella bulbosa, Nau- 

 tilus dekayi, Ammonites 2)lacenta, A. lobatus, Scaphites conradi, ti. 

 nicolletti, Baculites gra?idis, Busycon bairdi, Fusus culbertsoni, F. 

 newberryi, Aporrhais americana, Pseudobuccinum nebrascense, Mac- 

 tra xoarrenana, Cardium subquadrafum, and a great number of other 

 molluscous fossils, together with bones of Mosasaurus missouriensis, 

 etc. Found at Fox Hills, near Moreau river, near Long Lake, above 

 Fort Pierre, along the base of Big Horn Mountains, and on North and 

 South Platte rivers. Estimated thickness, 500 feet. 



In Nebraska the sandstones of the Dakota Group rest directly upon 

 rocks of the age of the Upper Coal Measures, or of Permian Age. 



They described from the Fort Pierre and Fox Hills Groups, at Deer 

 Creek, near the north branch of the Platte river, Leda bisulcata, now 

 Nuculana bisulcata, Gervillia recta, Crenella elegantula, Cardium 

 pertenue, now Protocardia pertenuis, Tellina nitidula, now JIactra 



