1875.] "iuJ [Stevenson. 



lished. Prof. Cope* has given a brief statement of its relations in the 

 region northwest from Santa Fe, and lying between the Chama and San 

 Juan Rivers. This region had been visited previously by Dr. Newberry 

 in 1859, and by myself in 1873, but the trails followed merely crossed the 

 region, and only skirted that portion referred to by Prof. Cope. The 

 Tertiary lake mentioned by Prof. Cope is evidently the same with that 

 crossed by Dr. Newberry, when with the Ives Expedition. The Cretaceous 

 here consists of Lower Cretaceous, sandstones, Middle Cretaceous, mostly 

 dark shales and limestones, Upper Cretaceous, sandstones. Throughout 

 the whole series Cretaceous species occur. In the Upper group Ammo- 

 nites, Baculites, and other indisputable forms occur in great abundance, 

 associated with Halymenites major. The following is Prof. Cope's state- 

 ment : 



" The shore of this lake was formed by rocks of the Cretaceous forma- 

 tion of an age near the No. 3, of Meek and Hayden. In approaching it 

 from the east we traverse the sandstones of Ci"etaceous No. 1, both hori- 

 zontal and tilted at various angles, and find No. 2 resting upon it, fre- 

 quently unconformably, and tilted at higher angles, frequently 45°, some- 

 .times 50°, to the west and southwest, and containing numerous fossils, as 

 Inoceramus, etc. The upper sandstones of this formation pass into a 

 brackish or fresh-water formation, which includes a bed of lignite, of 

 sometimes 50 feet in thickness. Above this rests, conformably, where seen, 

 a moderate thickness of rather soft marine rocks, containing numerous 

 shells, Acephala, Gasteropoda, and Cephalopoda, including Oysters, Bacu- 

 lites, and Ammonites resembling A. placenta most, with sharks' teeth. 

 Resting unconformably upon these, with a much reduced dip, is a mass 

 of brown and reddish sandstone, some 1500 feet in thickness, inclining 

 perhaps 10° south and southeast. These pass continously into the super- 

 incumbent red and gray marls, alternating with brown and white sand- 

 stones of the fossiliferous beds of the Eocene. The observed part of 

 these beds is about 1500 feet in depth." 



Having been within not more than fifteen miles from the verge of the 

 Eocene basin, I feel assured that Prof. Cope is inaccurate in his reference 

 of these I'ocks to Nos. 1, 2, and 3, of the Cretaceous. They are the Lower, 

 Middle, and Upper divisions of the Cretaceous and represent the whole 

 series. 



Prof. Cope's mistake was a natural one in his circumstances, as he had 

 devoted no time to the study of the Cretaceous in New Mexico, though 

 he had examined that formation quite closely at the north. 



Respecting the. geological position of this group there has been great 

 difierence of opinion. On one side the statements have been for the most 

 part very positive, while on the other they have been uncertain and more 

 or less compromising. Those who have studied the plants, throw the 

 beds into the Tertiary, while those who have studied the fauna and the 

 stratigraphy regard the greater portion of the mass as Cretaceous though 



^ * Lieut. Wlieeler's Eeport of Pi-ogress for 1873. Appendix. 



