DEVONIAN AND MISSISSIPPIAN FAUNAS 117 



In the Mauch Chunk series of eariier authors, Stevenson' recog- 

 nizes three members, a lower the Tuscumbia, a middle the Maxville, 

 and an upper the Shcnango. Toward the close of Pocono time there 

 was a marked contraction of the sea in the Appalachian Basin, just as 

 was the case at a corresponding time in the Mississippi Valley Basin. 

 This contraction was of such proportions that the Tuscumbia beds 

 were not deposited in Ohio in the area occupied by the earlier Waverly, 

 except at the Kentucky border, but, as in the west, there was a read- 

 vance of the sea until it had reached its maximum extent in the deposi- 

 tion of the Maxville limestone w^hich is to be correlated essentially with 

 the Ste. Genevieve limestone of the Mississippi Valley. Such a cor- 

 relation would make the Tuscumbia essentially contemporaneous with 

 the St. Louis limestone of the Mississippi Valley, a correlation which 

 is sustained by the paleontologic evidence. The Shenango is said to 

 contain fossils characteristic of the Chester of the Mississippi Valley,^ 

 and may be correlated with that formation. 



MISSISSIPPIAN FAUNAS OF THE ROCKY MOUNTAIN BASIN 



In Montana and elsewhere in the northern Rocky Mountain region, 

 limestones of Mississippian age are widely distributed, although but 

 little data in regard to the faunas have been published. The most 

 notable contribution to our knowledge of these faunas is that of Girty 

 on the Carboniferous fossils of the Yellowstone National Park.^ The 

 faunas here described are distributed through more than 1,600 feet of 

 strata of the Madison limestone, but they do not show any such differ- 

 entiation as is recognized in the Mississippi Valley. One general fauna 

 persists with but minor changes throughout the entire series and this 

 fauna shows many affinities with the southern Kinderhook faunas of 

 the Mississippi Valley, as well as with the fauna of the Salem lime- 

 stone. Faunas allied to that of the Salem have also been detected 

 elsewhere in the region, as the Idaho fauna noted by Meek and the 

 fauna of the Yakinikak limestone already mentioned. These relations 

 suggest that in this northwestern region a long-lived fauna, having 

 more or less close relationships with the Salem fauna, was contem- 

 poraneous with the larger part of the entire Mississippian series of the 



1 Op. cil., p. 85. 



2 Stevenson, op. cit., p. 85. 



3 Monograph, U. S. G. S., XXXII, Pt. 2, pp. 479-599. 



