28 :mi:s()Z()I(' floijas of rNiTKi) statks. 



amphitheater that I h:ive de.scriljecl. It is also seen above the Shiiia- 

 riimp to the east of the Petrified Forest. It is therefore probal)ly safe 

 to assume that this formation is continuous from Echo ('hffs to the 

 boundary Hn(^ of Xew Mexico. 



Of tlie painted cliffs there seems to be little more to say. In 

 looking at these cliffs fi'om a tlistance it is seen that they are overlain 

 by a white formation, the nature of which it is important to consider. 

 Before we had visited the region, so as to ()l)tain a close view of them, 

 it was natural to suppose that they might constittite Jin-assic limestones 

 and that the Triassic system might terminate at the line which separates 

 them from the variegated sandstones. But upon close examination 

 this was found not to be the case, and these white rocks were fotmd to 

 consist of sandstones, often very pure and cross-bedded, with scarcely 

 any admixture of marl. These, withovit question, constitute the summit 

 of the Triassic system in this region. The}' are, however, not always 

 white; or at least in some places, as, for example, in the vicinity of Tuba, 

 they are underlain ])y a still thicker bed of soft brown sandstone, which 

 is somewhat argillaceous and easily worn by the wind, forming chimney 

 l)uttes and ruins. This bed has a thickness along the headwaters of 

 the Moencopie Wash of about 200 feet, and is overlain at the highest 

 points by the white sandstones to a thickness of 100 feet more. These 

 sandstones are very porous and all the waters that fall in that region 

 innnediately pass through them; but as they approach the summit of 

 the much harder and firmer beds that constitute the lower formations 

 these waters are arrested and come out in the form of springs, sometimes 

 almost of small rivers, along the crest of the cliffs above the Moencopie 

 Wash. It is on one of these springs that the little Mormon town of 

 Tuba is located, and this is true also of Moa Ave, Willow Springs, and 

 other settlements in that country. Still farther back the Cretaceous 

 lignites and limestones lie vmconformably tipon these tipperniost sand- 

 stones of the Trias, and the Jurassic is wanting altogether. 



r 



PALEONTOLOGICAL RELATIONS. 



Having thus l)riefly sketched the stratigraphical relations of the 

 Older Mesozoic rocks of Arizona, I shall next consider their paleonto- 

 logical relations, in so far as they were ascertained on this expedition, 

 as shedding light upon the age of the group. 



