2 PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



formed is about 2.5 miles in its greatest extent, in a north-and-south direction. 

 Its very steep walls, for the most part about 700 feet in altitude, attain their 

 greatest height in the northwest part, where the altitude may exceed 800 feet and 

 where the Permian exposures are the greatest. 



The erosion of the floor of this basin, acting on the beds of alternating sand- 

 stones and clays, has formed a series of steps or low cliffs, which for the most part 

 dip at a small angle toward the west. Toward the sides and upper end of the 

 cafion these ridges become more prominent, frequently forming high bluffs and 

 cliffs. The lowermost beds in the canon are deep chocolate-colored sandstones 

 and fine conglomerates; the latter weather into low, rounded hills, frequently 

 streaked with greenish layers. Bone fragments were found in these layers in vari- 

 ous places in the basin. Above these darker colored sandstones are more massive 

 sandstones, weathering more or less whitish, which ascend at the north end of the 

 canon to perhaps 350 feet above the stream bed. All vertebrate fossils that we 

 foimd, of Permian or Permo-Carboniferous age, were below these sandstones, which 

 form a fairly definite horizon about the basin and which may be taken as the lower 

 limits of the Trias. 



It has been questioned by us elsewhere whether the vertebrate fossils found in 

 Texas, Oklahoma, southern Kansas, Illinois, and Pennsylvania are really of Permian 

 age. At the south side of the cafion Case found a perfect cast of a Spirijer, 

 identified by Professor Schuchert as S. rockymontanus Marcou, a form occurring in 

 Colorado in the Pennsylvanian. Though the specimen was found free, so that its 

 exact horizon could not be determined, its excellent preservation proves conclusively 

 that it had not been carried far from its original bed, and inasmuch as vertebrate 

 fossils are found in the deepest strata of the canon it seems quite certain that the 

 specimen came from an intercalated bed among those yielding so-called Permian 

 vertebrates. No other explanation seems possible. It is the conviction of both 

 the present authors that the lowermost at least of the strata yielding vertebrate 

 fossils are of Pennsylvanian age, and this conviction is strengthened by the known 

 position of the vertebrate horizons in Texas, Kansas, Illinois, and Pennsylvania, 

 that of the last-named region being definitely known to be Pennsylvanian. 



Section I. EL COBRE CANON. 



Feet. 



Yellow sandstone and conglomerates 75 Upper Trias 



Purplish and gray clays 40 ? 



Purplish sandstones 20 Lower Trias? Barren 



PurpUsh clays and nodular sandstone 25 " " 



Red sandstone 5 " " 



Bright red clay 35 



Purple clay 12 " " 



Bright red sandstones 22 " " 



Co^-se purplish sandstones 12 " " 



Bright red clay with greenish nodules and purplish bands . . 100 " " 



Coarse, hard purplish sandstone 8 " " 



Bright red clay and sandstone 65 " " 



Hard red and purplish sandstone 6 " " 



Bright red sandy clay, with purplish streaks 90 " " 



Purplish and dark brown clay 22 " " 



Red clay and hard red sandstone 30 " " 



Hard purpUsh sandstones 35 " " 



Red clay 7 ? 



Purple sandstones 3 ? 



Red clay 22 ? 



Permo-Carboniferous red and brown sandstones and clays, 

 fossiliferous 



A section of the west wall of El Cobre Cafion, as far down as the horizons 

 jrielding fossils of Paleozoic age, is given above. It must be especially remem- 

 bered, however, that this and Section II, on p. 4, will not apply in detail to any 



