lO GIRTY 



some interestinof relations between beds of the West and the 

 Southwest. The Pennsylvanian faunas of the West have often 

 a fades which is novel and perplexing to one familiar only with 

 the well-known Eastern ones ; and it is probable that the lowest 

 faunas of this region will in many cases prove to be of Pottsville 

 age. While I have not been able as yet to make the numerous 

 identifications and comparisons necessary to establish this as a 

 fact, the resemblances to the fauna of the Morrow formation 

 (Pentremital limestone, coal-bearing shale, and Kessler lime- 

 stone) are sufficiently numerous and striking to make this a very 

 promising hypothesis. 



It will be remembered that C. D. Walcott described an inter- 

 esting fauna from the Eureka district,' in which there was found 

 a commingling of Upper and Lower Carboniferous types. This 

 is likely to prove of Pottsville age. The lowest Pennsylvanian 

 faunas of Colorado and of New Mexico, especially the latter, 

 also show similarities which appear to me highly significant. 

 The Bend and Millsap formations of Texas may likewise prove 

 to be Pottsville. In Indian Territory the Wapanucka limestone, 

 whose fauna I at one time described^ in a very limited and cur- 

 sory manner, is, I feel fairly well assured, to be closely corre- 

 lated with the Pentremital and Kessler beds. 



The faunas of the middle and lower Pottsville are as yet un- 

 known, unless to this horizon belong the beds underlying the 

 Morrow formation in Arkansas and the Wapanucka limestone in 

 Indian Territory. The possibility involved is interesting, and 

 deserves investigation. The case may be stated as follows : 

 The faunas between the Boone and the Pentremital have always 

 been regarded as belonging in the upper Mississippian (Gene- 

 vieve), in which case the lower and middle Pottsville are unrep- 

 resented in this area. Now the stratigraphic and lithologic 

 break at the top of the Boone is as strong as, possibly stronger 

 than, that at the base of the Morrow formation. Furthermore, 

 while the faunas of the beds between the Boone and Kessler 

 show marked Mississippian affinities, they at the same time 

 possess much individuality. The resemblances to the Gene- 



' U. S. Geol. Surv., Mon. S,.iSS4. 



2U. S. Geol. Surv., 19th Ann. Rept., pt. 3, 1S99, pp. 543, 573. 



