36 OARBONIKKROTTS FORMATI()NS AND KAITNAS OK COLdKADO. 



tlircc iir(^ coiuinon lo (lie lis( frdiii tlii' beds (■iillc<l hy the simii'. iiiiini' in the UJnta 

 Mountains, aiul these three { l/> niijinniiteft (nxnintria, Producf ks hirnjitijnniis, and 

 Seiiiiinilti siili/ilihi) are sucli as. havino- hi coiiiinon acceptation specific limits of th(> 

 liroiidest, liiive also the loiiyest range, which may be said to have been synchronous 

 with all Upper Carljoniferous time. Two Upper Carboniferous faunas of equal 

 extent could scarceh' have less in common than the two listed hei-e. The same is 

 true of the meager faunas Icnown from the upper Aubi'e}^ group in tlie two areas. 

 These faunas, as cited from the Uinta Mountains and from the confiuence of the Grand 

 and Green rivers, contain not a single species in common, but it is noteworthy thiit 

 the fauna of the Tipper Aubrey in the Uinta Mountains is practical!}' the same as 

 that of the lower Aubrey in the same region, and a similar resemblance ma}' ))e 

 pointed out Ijetween the faunas of the upper and loM'er Aubre}' groups at the 

 confluence of the Grand and Green rivers. 



Of the geology of the Grand Canj'on region, whence Powell derived the name's by 

 which the formations in the Uinta Mountains are denoted, but little need be said. 

 Powell himself cites no Carboniferous fossils from 'this region. Gilbert first gave 

 local names to the Carboniferous series in the Grand Canyon region," dividing it into 

 the Aubre}' limestone, the Aubrej^ sandstone, and the Red Wall limestone. He cites 

 from the Aubrey limestone (the upper Aubrey of Powell) an Upper Carboniferous 

 fauna not unlike that which the latter obtained in the homonymous beds at the junc- 

 tion of the Grand and Green rivers. In the topmost strata Schizodu^, Pleuroj)horus, 

 and BaTiev^eUia were found, an assemblage not noted by Powell, and one "suggesting 

 the Permo-Carboniferous of the Mississippi Valley."" The Aubrej' sandstone con- 

 tains few fossils, "but an intercalated limestone, below the middle of the series at 

 Can3'on Creek, bears the familiar Coal Measure shells."" 



In the Hed Wall limestone fossils are said to be "abundant near the top, but 

 difficult to find in the lower portions."* The lowest horizon from which fossils were 

 obtained was a trifle below the middle of the series. Thej' were doubtfully referred 

 by Meek to the Lower Carboniferous. "The fauna of the upper portion is rich in 

 species, and, while differing from that of the Aubrey limestone, is equally referable 

 to the Coal Measures."* 



In describing the Paleozoic section in Kanab Canyon, Walcotf identities Silurian, 

 Devonian, Carboniferous, and Permian strata. These are separated from one another 

 bj' planes of erosional unconformity, and in addition the Permian is divided into 

 two portions b}' an erosion period, and the Upper Permian is succeeded bj' another. 

 To the Carboniferous Walcott refers the Ked AVall limestone and the upper and 

 lower Aubrey groups. His Lower Permian is the Permo-Carboniferous of Gilbert, 



nU. S. Geog. Geol. Surv. W. 100th Mer., Rept., vol. 3, 1875, p. 177 



iabia.,p. 178. 



<• Am. Jour. Scl.. 3d ser., vol. 20, 1880, p. 222. 



