204 J. Marcou — Jura and Neocomian of Arkansas, 



Upper Cretaceous or Cenomanian of Europe. No conclusion 

 can be drawn from such a meagre florula. A Cycadse, called 

 Cycladoidea munita by Cragin, recalls the Cycadse of the 

 Purbeck beds of the island of Portland id England. As to 

 the impossibility of having dicotyledonous plants in the Jura, 

 as has been insisted upon by my adversaries, it is a very haz- 

 ardous supposition without any solid basis to rest upon. The 

 great number of species of dicotyledonous plants of the rich 

 flora of the Dakota formation, indicates that we must expect 

 to find dicotyledonous plants far below that formation ; and to 

 say that dicotyledonous plants did not exist during the Jurassic 

 period, is merely a supposition, based on negative proof; a 

 very uncertain, questionable basis to rest upon in our time of 

 belief in evolution as well of plants as of animals. After the 

 ill success of the great paleobotanist Oswald Heer, in the use 

 of negative proof, to deny the existence of dicotyledonous 

 plants in the Cretaceous of America, it is rather strange to see 

 paleobotanists in America falling into the same error. 



As the Cheyenne sandstone does not exist everywhere in 

 Kansas, where the Neocomian, called Kiowa shales, is seen, as 

 in Central Kansas, McPherton and Saline Counties ; and as at 

 Comet Creek, the Neocomian, with G. Rwmeri, rests in such 

 places directly on the New Red sandstone rocks, it is most prob- 

 able that it belongs to the Jurassic period, and is an eastern 

 prolongation of the yellow and white sandstone of Pyramid 

 Mount. It has the same lithology with brilliant colors, as 

 noted by Professor O. C. Marsh, and future researches will 

 decide its real and exact geological age. A great desideratum 

 is the careful examination near Belvidere of the contact of the 

 Cheyenne sandstone with the first three or four beds resting 

 on it. Some sort of discordance, due to erosion and denuda- 

 tion, and perhaps also some little difference in the dip of the 

 strata — a difference which can be only very small considering 

 the almost horizontality of the strata of the plains — may be 

 detected. Of course it will require prolonged research and a 

 very acute practical geological mind, to discover such discord- 

 ance. But I hope that some day the work will be undertaken. 

 For me such a discovery is only a question of time. So far 

 the discordance may be looked for between No. 6 and No. 7 

 of Mr. Hill's section. The Kiowa shales of Professor Cragin, 

 so well described by Messrs. Cragin and Prosser, represent the 

 Neocomian or Lower Cretaceous in Kansas, from No. 7 of the 

 Belvidere section up ; below they may be Jurassic. 



Oklahoma. — The Comet Creek bed, as it is called by Mr. 

 Hill, is not composed " of a single stratum of Gryphsea lime- 

 stone, five feet thick," as he says (this Journal, vol. 1, p. 228) ; 

 but of five strata or beds, which are described in my " Field 



