6T. joiix.j SECTION IN Pierre's mountains. 427 



brancli Avliicb, but for its greater convexity, resembles Camptonectes, 

 and a small indeterminate Gasteropod. 



28. Drab sbaly limestone. 



29. Dark chocolate-colored shales. 



30. Mainly light drab, indurated, marly shales, with thin bands of 

 drab shaly limestone, forms a heavy deposit. A small Grijphcca {G. Gal- 

 ceola f) occiu's in great abundance in the middle and ujiper part of the 

 bed. 



31. Hard, indurated grit bed, 5 to 10 feet. 



32. Chocolate-mottled indurated deposit, 30 to 50 feet. 



33. Dark blue and gray, laminated, gritty limestone, a heavy bed, 20 

 to 40 feet. Dip 37°, S. 4uO W. 



34. Unexi)osed space, toward top light drab deposit. 



35. Dark and light gray, very hard sandstone, overlaid by dark blu- 

 ish-gray very hard gritty layers. 



30. Dark and buff gray coarse-grained sandstone, with hard pink lam- 

 inated layers and dirty yellow and brownish soft layers above -, 50 to 

 75 feet exposed. Dip 44°, S. 50° W. 



37. Eusty-brown, gray, and reddish conglomerate, and laminated, cross- 

 bedded, verv' hard sandstone, forming a conspicuous heavy ledge, of 

 which a thickness of 25 feet is exposed, dipping S. G0° AV., at an angle 

 of 45°. The pebbles are rounded and arranged in more or less regular 

 layers, and the whole bed is transformed into an intensely hard quartzite, 

 whose rugged outcrop may be traced for miles, and is the same ledge 

 that crosses the spur-ridge in the vicinity of Low Pass on either side. 



38. Dull red shales, 40 feet, more or less. 



39. Alternations of drab limestone and chocolate-colored sandstone, 

 40 feet, more or less. 



40. Chocolate-red shales and indurated sands. 



41. Light drab limestone and interbedded shaly layers. 



42. Chocolate-colored shales and gTitty layers. 



43. Drab shaly and bluish limestones, interbedded with drab shales, 

 forming a heavy deposit several hundred feet in thickness. 



44. Keddish buff-gray hard sandstone, a heavy ledge. 



The base of the section rests upon the lower limestones of the Carbonif- 

 erous series, succeeded by the ui)per siliceous member of the same series, 

 which here attains a thickness of above 2,000 feet between beds No. 1 

 and Xo. 18, inclusive. The fossils of bed No. 10, although at present not 

 specifically determined, clearly belong to Carboniferous types. But in 

 the instance of those obtained from bed No. 17, which on account of the 

 imperfect state of their preservation as also tlie fact that they belong to 

 less characteristic genera, there is room for doubt in the determination 

 of the equivalency of the strata in which they occur. The Linfpila could 

 hardly be admitted in evidence in so important a question, but the httle 

 Lamilli branch certainly bears a striking resemblance to a species of 

 Fleurophorus prevalent in Permo-Carboniferous horizons in the region of 

 the Lower Missouri. Tliis fact, if not actual specific identity, in connec- 

 tion with the stratigraphic position of the ledge, which lies immediately 

 below the TYiassic " red beds," strongly favors the reference of these upper 

 beds to the horizon of the Permo-Carboniferous. As is generally supposed 

 in the case of the Lower Missouri region, there may be no well-defined 

 demarkation, either lithological or paleontological, separating these 

 upper beds from the distinctively Carboniferous horizons ; but taking into 

 account the prominent lithological characters of the latter deposits, they 

 are distinguished in a marked manner into upper siliceous and lower 



