198 J. Marcou — Jura and Neocomian of Arkansas ■, 



the most elementary kind of knowledge of the genus Gryphwa, 

 uniting into a single species six or eight entirely distinct spe- 

 cies. It was to be hoped that when, in about 1880, Indian 

 Territory and the Tucumcari region were finally opened for 

 settlement and civilization, my opponents would examine the 

 two localities; one called Comet Creek, now in G. County, 

 Oklahoma, and the other Pyramid Mount in the Tucumcari 

 region of New Mexico. But not at all ; to this day, Comet 

 Creek has not been visited by any other practical geologist* ; 

 and Pyramid Mount of the Tucumcari area was systematically 

 left out of the route of exploration by the three persons who 

 were there, since 1888. The curious part of it is that the 

 section at Pyramid Mount is most complete, without any ob- 

 scurity by vegetation, practically a bare wall, and unique in 

 the Tucumcari region for its beauty and perfection from a 

 geologic point of view. I shall not imitate the frankness of 

 my friend Pasteur, and contest the capacity of my adversaries 

 as stratigraphists and paleontologists, but I owe it to science 

 to maintain what I consider to be exact and true ; and how- 

 ever tired and wearied by years, by my infirmities and the 

 exceptional length of the discussion — lasting almost half a cen- 

 tury — I shall continue not only to affirm the correctness of my 

 observations, but also to ask my numerous adversaries to visit 

 Comet Creek and Pyramid Mount, and beg them to publish 

 the sections accompanied by good figures and descriptions of 

 all the fossils they may gather in situ. I am happy to remark, 

 that they will have the great privilege and immense advantage 

 of remaining there as long as they please, to observe and col- 

 lect specimens, while I was enabled, on account of the rapidity 

 of the march of my military escort, to remain at Comet Creek 

 only one hour and at Pyramid Mount only three or four hours. 



The question of the existence of the Jura and the Lower 

 Cretaceous (which I call briefly Neocomian) has taken, thanks 

 to the opposition, such great proportions, that one of my oppo- 

 nents said lately : " There are reasons for suspecting that no 

 marine Jurassic formations of Atlantic sedimentation have as 

 yet been discovered north of Argentina (South America) on 

 the present Atlantic slope of the American hemisphere." 

 (Science, vol. iv, ]STo. 103, p. 920.) A clean sweep of the 

 marine American Jura. 



Let us review the main localities in the United States, west 

 of the Mississippi Piver and east of the Pio Grande del Norte. 



Arkansas. — For the sake of brevity, and not to burden the 



* Lately the locality of Comet Creek has been visited by Mr T. W. Vaughan, 

 who finds the same beds of limestone containing G. Rcemeri (called G.forniculata). 

 His description does not differ from the one I have given as far back as 1853. 

 " Outlying areas of the Comanche series" ; this Journal, vol. iv, July, 1897J 



