114 WHITMAN CROSS 



pebbles. It is not certain that Ward referred to this material, the 

 significance of which is not known. 



Comparing the results obtained by Walcott and Ward in portions 

 of the Colorado Plateau not many miles apart and where all earlier 

 geologists have given the impression that the formations change 

 but little from place to place, we find in fact remarkable differences. 

 Walcott established an unconformity below the original Shinarump 

 conglomerate; he discovered no vertebrate fossils in or near that 

 stratum; but 910 feet above it, below the Vermilion Cliff sandstone, 

 he found fish remains of unique character suggesting to the specialist 

 Jurassic rather than Triassic affinities. Ward, on the other hand, 

 finds at 400 to 800 feet below the Vermilion Cliff the Triassic reptilian 

 fauna characterizing the basal portion of the Dolores formation 

 through western Colorado and on Grand River; he noted no uncon- 

 formity near this vertebrate horizon and does not recognize the 

 Shinarump conglomerate of Powell, Walcott, and others. These 

 discrepancies demonstrate that there is room for much further study 

 of the Shinarump and associated formations in northern Arizona. 



The lower Trias of the Zuni Plateau. — The continuity of Mesozoic 

 and upper Paleozoic formations from the vicinity of the Grand Canyon 

 into northwestern New Mexico is a subject on which all geologists 

 who have examined the region are agreed. In his report on the 

 Zufii Plateau, Button (8, p. 134) identifies 450 feet of strata as 

 Permian, through the presence of fossils mentioned as Bakewellia 

 and Myalina (without specific identification) and from the strati- 

 graphic position of the beds between the Aubrey and a sandstone iden- 

 tified by Button as the Shinarump conglomerate. The identification is 

 not convincing, for the only descriptive terms employed are of general 

 application and indicate a character which one cannot suppose to be 

 persistent. The Shinarump conglomerate is referred to by Button, 

 in speaking of its general character, as "a well-marked, coarse sand- 

 stone," and as "a very coarse conglomeratic sandstone." The only 

 statement of its character in the Zuiii Plateau is in the first three words 

 of the following sentence : " The coarse sandstone, equivalent, I believe, 

 to Powell's Shinarump conglomerate, will be for the present the pro- 

 visional base of the [Triassic] series" (8, p. 135). In view of Ward's 

 statement that conglomeratic beds appear variably through some 



