114 Cretaceous. 



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 highly 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 usuall}' contains 

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

 at Little Thompson creek 150 feet. The Foi't 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 

 Colorado, TFoocZu'arrf/a latlloha, Pteris erosa ^ P. subsimplex, P. rtjfinis, 

 now Osmmida affinis^ Aspidiam goldianum, now Lasfrea goldana, 

 Sphenopteris memhranacea. Selaginella berthotidi, Hymenophyllum 

 confasum, Flabellai^in fructifera, now Sahalites fructiferus^ Quercus 

 f/oldaniis, Ficus planicosfata, var. goldana^ F. zizyphoides, Platanns 

 rhomhoidea^ Vibernum laJcesi, Nelumbimn lakesanum, Zizyphus dis- 

 tortus, Bhamnus inceqimlis ; from Black 'Bntte,Wyowiing,Woodwardia 

 latiloba. var. minor, Sphenopteris nigricans, Quercus cleburni, Pisonia 

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

 gardneri, now Gym7iogramm.a gardneri, Equisetum Imvigatiim, Erio- 

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

 Cornus Jiolmesi ; from Evanston, Laurus sessiJiJlora, r\ow Tetranthera 

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

 brossana, now Laurus brossana, and Cornus inipressa. 



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 upper 

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

 Colorado, Cionodon arctalus, Polyonax mortuarius, Bottosaurus per- 

 rugosus, Trionyx vagans, Plastomemis inmctulatus, P. insignis, and 

 AdoGus lineolatus. 



* Hayden's 7th Rep. U. S. Geo. Sui'. Terr. 



