sT.Joirs-.] PALEOZOIC AEEAS CAEBONIFEEOUS. 487 



denee goes. we have good grounds for the recognition of physical con- 

 ditions, accompanied by organic manifestations, representative of at 

 least two i>rominent formations of the Lower Carboniferous in this region, 

 viz. the Keokuk and Warsaw beds of the Saint Louis. There also occur 

 in this range certain limestones which are charged with Liihostrotion 

 and Syringopora; but the relative position of these beds with those 

 above mentioned was not determined. However, in the vicinity of Sta- 

 tion IX, the LitJwstrotion limestone is underlaid by a heavy series of 

 bluish-gray cherty limestone, with Zophrentis and crinoidal remains, 

 which may well embrace the lower horizons. If the paleontological 

 evidence in all cases holds good, then we should infer that the Litho- 

 strotiou horizons correspond to the Saint Louis formation. 



It is probable that, in the Snake Eiver Range, the Lower Carbonifer- 

 ous formations are well developed, especially in the magnificent natural 

 sections exposed along the lower course of the Grand Cation. But in 

 the northeastern belt, which alone was penetrated the past season, at 

 only one or two points in the Pierre's Mountains are these deposits well 

 exposed. Here was noted the uppor Lithostrotion bearing limestones, 

 and it seems not improbable the older formations may yet be found in 

 then- proper order in the ridge terminating in Spring Point. They here 

 exhibit the same lithological and mineralogical concomitants elsewhere 

 prevalent, and wherever the rocks are much disturbed they are, in 

 common with other limestone formations above and below, traversed by 

 seams of calc-spar, which doubtless owe their origin to infiltration. 



Little was elicited, in the course of the hasty examination made in the 

 Teton Range, relating to the detail stratigraphy of these lower limestone 

 deposits, beyond the recognition of the various groups above alluded to 

 in the similar faunal associations which also here occur. We also ob- 

 serve in this quarter the frequent occurrence of red-stained beds, and in 

 the vicinity of Station XXXII, at the northern end of the range, these 

 lower horizons are < |uite siliceous. But at no point visited were the pas- 

 sage-beds at the base of the series satisfactorily revealed, although it is 

 apparent, almost to a certainty, that the space intervening between the 

 Carboniferous and the Niagara limestones is occupied by soft or shaly 

 deposits. Even the Carboniferous limestones appear to be iuterbedded 

 with shales and shaly layers, Avhich give rise to the step-like steep 

 slopes of their outcrop, which usually weathers in low mural exposures, 

 alternating with narrow taluses, giving to some of the isolated outlines 

 in the higher portions of the range their peculiar pyramidal form. 



In the Gros Ventre Mountains, particularly at Station XL VI, we gain 

 a clue to the character of the inferior deposits of this series, as also the 

 nature of the beds of passage. The latter as here exposed show yellow 

 weathered shaly deposits, j)robably made up of limestones and shales, 

 and which constitute a rather marked band wherever the horizon is not 

 covered with debris. The lower limestones are a grayish or bluish drab 

 color, overlaid by dark brownish-drab magnesian layers charged with 

 Hemipronites crenistria, or a closely-allied form. The thickness of the 

 limestones intervening between the heavy magnesian limestone of the 

 horizon of the Xiagara and the upper red siliceous or arenaceous horizon, 

 which latter may be regarded as the top of the lower series, it is impos- 

 sible to state with accuracy; but this space appears to be of less vertical 

 extent at this locality than in the Teton Mountains, yet it may reach 

 1,000 feet. 



As has already been observed, in the vicinity of Buffalo Fork Peak 

 the deposition of limestone-making materials went on without interrup- 

 tion from the time of the Upj>er Quebec limestone to the Lower Carbon- 



