352 ANCIENT POPULATION LN 



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 cristones. The hog-back of No. 4, being com- 

 posed of softer material, is worn by erosion into a succession of subcorneal 

 eminences. 



My attention was first called to the archaeology of the region by 

 observing that the conic hills just mentioned appeared to be in many 

 instances crowned with stone structures, which, on examination, proved to 

 be ruined buildings. These are round or square, with rounded angles, and 

 from 15 to 25 feet in diameter. The walls are 2 and 3 feet in diameter, 

 and composed of stones of moderate size, which have been roughly dressed, 

 or built without dressing into solid but not very closely-fitting masonry. 

 The walls remaining 1 measure from 1 feet high downward. The floor 

 inside is basin-shaped, or like a shallow bird-nest, and frequently supports 

 a growth of sage brush (Artemisia) of the same size and character as that 

 growing on the plains below, and other shrubs. Sometimes they contain 

 pinion trees (Pinus cembroides) of 1 and 2 feet in diameter, which is the 

 average and full size to which they grow on the adjacent ridges and pla- 

 teaus. Within and about them fragments of pottery abound, while flint 

 implements are less common As these are similar in all the localities 

 examined, they will be subsequently described. A building more or less 

 exactly agreeing with this description was found on the summit of every 

 hill of a conical form in the vicinity. Their form is probably due to the 

 shape of the hill, as they were differently built on the level hog-backs. 

 None of the circular buildings were found to be divided, nor were any 

 traces of such buildings observed on lower ground. 



The hog-back of Cretaceous No. 3 is the locality in question, only one 

 or two hundred yards distant from the eastern of the hills just described, 

 from which it is separated stratigraphically by a bed of lignite. At some 

 points this stratum has been removed by atmospheric erosion, leaving a 

 ravine between the hog-backs. Near the middle of a section of the hog- 

 back No. 3 a portion of this formation remains, forming a narrow causeway 



