1875.] 4:ib [Cope. 



3d. That the Cretaceous from the beginning was a lignite-producing 

 period, 



4th. That the fauna, whenever of a chai'acter to be compared with 

 known standards is Cretaceous, even to the top of the series, 



5th. That the hypothesis that this group or any portion of it is Ter- 

 tiary is unsupported by definite evidence, 



I am compelled to regard the Great Lignitic Group as Cretaceous, 

 simjDly a renewal of the conditions marking the period of the Dakota 

 Group. 



ON THE EEMAIKS OF POPULATION OBSERVED ON AND 

 NEAR THE EOCENE PLATEAU OF NORTH- 

 WESTERN NEW MEXICO. 

 By E. D. Cope. 

 {Bead before tlie American PMlosopMcal Society, June 18, 1875.) 



While encamped on the Gallinas Creek, at the point where it issues 

 from the Sierra Madre, with the party detailed by Lieut. Wheeler for 

 purposes of geological exploration, I occupied intervals of time in the 

 examination of the traces left by the former inhabitants of this portion 

 of New Mexico. 



Had time permitted, the exploration of these remains might have been 

 much extended, but under the circumstances a mere beginning was made. 

 The observations show that the country of the Gallinas, and the Eocene 

 plateau to the west of it, were once occupied by a numerous population. 

 Now, there are no human residents in the region, and it is only traversed 

 by bands of the Apache, Navajoe, and Ute Tribes of Indians. The in- 

 dications of this ancient i^opulation consist of ruined buildings, pottery, 

 flint implements, and human bones. Broken vessels of baked clay are 

 frequently found, and the fragments occur in all kinds of situations 

 throughout the country. They are usually most easily discovered on the 

 slopes of the hills and hog-backs of Cretaceous and Tertiary age, and 

 where abundant, generally lead to a ruined building standing on the 

 elevation alone. 



The hog-back ridges which I have described in my geological report, 

 extend in a general north and south direction on the western side of the 

 Sierra Madre, south of Tierra Amarilla. They vary from two to four in 

 number, and stand at distances of from half a mile to three miles from 

 the mountain range. The Gallinas Creek flows between two of them 

 near their southern extremities for perhaps fifteen miles. At one point 

 the hog-backs of Cretaceous Nos. 3 and 4 approach near together, 

 and the creek flows near to the foot of the eastern front or escarpment of 

 No. 3. The rock of this ledge is a hard sandstone, and resists 

 erosion hence its outcrop forms continuous sharp ridges, with distant 

 interruptions, which are termed by the Mexicans the Cuchillas or Cris- 

 toues. The hog-back of No. 4, being composed of softer material, is 

 worn by erosion into a succession of sub-conical eminences. 

 A. p. S. — VOL. XIV. 3j 



