TO JUNCTION OF GEAND AND GEEEN RIVERS. 47 



under that name in the Coal-Measures east of the Mississippi, yet accords well with 

 the figures and descriptions of the type specimens by Professor Hall; spines of Archce- 

 ocidaris, in great numbers, scarcely distinguishable from A. aculeattis of Shumard; 

 a Betteroplion, very like, if not identical with, one found in the Upper Carboniferous 

 and Permian of Kansas ; a species of Myalina (M. perattenuata), and an undeter- 

 mined Avicula. These fossils occur in great numbers, and there are, perhaps, other 

 species, which I have not enumerated, contained in the bed. It will be seen that in 

 this list of fossils there are none which are peculiarly Permian. The Bakevellia, Pleuro- 

 phorus, Axinus, and the species of Murchisonia, which give character to the fauna of the 

 upper magnesian limestone of Kansas, are here all wanting. It is evident, therefore, 

 that the question whether this bed shall be regarded as of Permian age depends upon 

 where the conventional line shall be drawn dividing the Permian and Carboniferous 

 formations in Kansas. If that line be drawn at the base of No. 10 of Meek and Hay- 

 den's section, this stratum would be excluded from the Permian and connected with the 

 Carboniferous series below. Should the Permo-Carboniferous beds of Meek and Hay- 

 den be included in the Permian, this would, of course, be Permian. If these beds 

 were divided midway, this would probably fall into the Permian division, but it might 

 be necessary to divide even this stratum, only 3 or 4 feet in thickness. 



TRIASSIG FOEMATION. 



The Red Beds of the Gypsiferous series form a conspicuous feature in the geology 

 of the neighborhood of Santa FC", being very freely opened both in the valley of the 

 Rio Grande and in that of the Pecos. In a previous report I have given a general 

 description of the rocks of this formation as developed in this vicinity, and have com- 

 pared the sections which they present with those of their equivalents in the Navajo 

 country and other parts of New Mexico, where I have examined them. The question 

 of their precise place in the geological series is also there discussed at some length, so 

 that already much has been said, which, though essential to a full presentation of the 

 facts relating to this group, need not be here repeated. A general re*sume" of this for- 

 mation will also be given in a succeeding chapter. I have before remarked, in the 

 description given of the geology of the country bordering the Santa Fd road, that the 

 vertical interval occupied by the Gypsum series in Kansas is much less than in New 

 Mexico. This fact will be at once obvious to the traveler coming from the East when 

 he enters the valley of the Pecos. Where last seen on' the Kansas, Little Arkansas, 

 or Cow Creek, "the Red Beds" which represent this group have nowhere a thickness 

 of more than 500 or 600 feet, while at Pecos 'village more than 1,000 feet of the series 

 is exposed in a single section, and its entire thickness in the vicinity of Santa Fd can- 

 not be less than 1,500 or 1,600 feet. By Mr. Marcou, this formation, considered as the 

 equivalent of the Trias of Europe, is represented as attaining a thickness of 5,000 to 

 6,000 feet ; but even in the Navajo country or on the San Juan, where it is apparently 

 most fully developed, its entire thickness is not more than 2,500 feet. In the Pecos 

 section the red sandstones and shales rest directly upon the Coal-Measure limestones, 

 and the Permian magnesian rocks of Kansas are entirely wanting. It is possible, 

 however, as I have before stated, that they are represented by the extreme upper 

 portion of the calcareous beds and by a part of the overlying red sandstones and 



