170 Cincinnati Society of JVatwrd History. 



shows a thickness of 240 feet, and another near the South Platte river, 

 385 feet. 



The Fort Benton Group consists of a series of shal}^ beds, which may 

 be either highl}^ argillaceous or quite arenaceous in character, there 

 being associated with them, in either case, a few thin, brown sand- 

 stones; the thickness from Big Thompson to South Platte varying 

 from 100 to 400 feet. A section at Little Thompson creek shows a 

 thickness of 400 feet, and one at Bear Canon 120 feet. 



The Niobrara Group is decidedly calcareous, and usually contains 

 numerous fossils. A section at Bear Canon shows 105 feet, and one 

 at Little Thompson creek 150 feet. The Fort Pierre Group, at Bear 

 creek is about 300 feet in thickness. 



The total thickness of the Dakota, Fort Benton, Niobrara, Fort 

 Pierre, and Fox Hills Group, at the Middle Park, is estimated at from 

 3,500 to 4,500 feet. A section of the Lignitic Group at Golden City 

 shows a thickness of 3,360 feet, and the estimated thickness at Middle 

 Park is 5,500 feet. 



Prof. Leo Lesquereux* described, from the Lignitic Group at Golden 

 Co\oviidiO,Woodwardia latiloha^ Pteris erosa^ P. subsimplex, P. affinis, 

 now Osmunda affinis.^ Aspidium goldianum^ now Lastrea goldana, 

 Sphenopteris membranacea, Selaginella herthondi^ Hymenophyllum 

 confusum^ Flabellaria fructifera, now Sabalites fructiferus^ Qiiercus 

 goldanus, Picks i^^^^nicostata, var. goldana^ F. zizyphoides^ Platanus 

 rhomboldea, Vibernum lakesi, Nelumbium lakesanum, Zizyphus dis- 

 tortus^ Bhamnus incequalis ; from Black Butte, Wyoming, TFoorZ?rr/rcZi« 

 latiloba, var. minoi% Sphenopterls nigricans, Quercus cleburni, Pisonia 

 racemosa; from the roof of coal mines at Sand creek, Colorado, Pteris 

 gardneri, now Gymnogramma gardneri, Equisetum IcBvigatum, Erio- 

 caulon porosum, JSFelumbium tenuifoUum ; from Coal creek, Colorado, 

 Cornus holmesi ; from Evanston, Lauriis sessilijlora, now Tetranthera 

 sessilljlora ; and from Mount Brosse, or Troublesome creek, Persea 

 brossana, now Laurus brossana, and Cornus impressa. 



Prof E. D. Cope, from the evidence of the vertebrates, and especially 

 from the evidence afforded by the remains of the Dinosauria, re- 

 ferred the Fort Union or Lignitic Group, the Judith River Group, 

 the Bitter Creek Group, and the Bear River Group to the uppei^ 

 Cretaceous. And he described, from the Fort Union Cretaceous, of 

 Colorado, Cionodo7i arctatiis, Polyonax mortuarius^ Bottosaiirus per- 

 rugosus, Trionyx vagans, Plastomenus punctulatus^ P. insignls, and 

 Adocus lineolatus. 



* Haydeu's 7th Rep. U. S. Geo. Sur. Terr. 



