78 C. W. Honess — Stanley Shale of OMaho^na. 



whether they should be called Rhomhopora or Batostomella. 

 These also throw no light on the question. 



"But the fragments of Cystodictya suggest Chester and 

 Lower Pennsjivania species rather than older species of the 

 genus. 



"Finally there are two fragments that seem to belong to 

 Prismopora, a genus ranging from Mid. Devonian to Pennsylva- 

 nian. Because of their smallness these Stanley specimens sug- 

 gest P. minuta, a Middle to Upper Pennsylvania species in 

 Illinois. 



' ' The invertebrate part of the evidence by itself would not be 

 conclusive either way. The trend of the evidence is toward the 

 Pennsylvanian rather than the Mississippian (either early or 

 late). Again there is nothing in the collection that may be 

 justly cited as definitely opposed to correlation of the Stanley 

 with lower Pottsville or basal Morrow, which conclusion I 

 reached in my "Revision" mainly on physical and diastrophic 

 consideration. 



' ' The fossils observed by me in the Jackf ork seemed decidedly 

 corroborative of my convictions respecting the post Chester age 

 of the Stanley. So far as I can see your new evidence leaves the 

 problem just about where I left it in 1911 — that is, with the 

 probabilities favoring assignment of the Stanlej^ to the earliest 

 Pennsylvanian. ' ' 



Origix of the Stanley Shale. 



The outstanding facts with regard to the sedimenta- 

 tion of the Stanley are: (1) the dark color of all of the 

 shales, slates, and sandstones; (2) the uniform even fine 

 grain of the sandstones and quartzites; (3) the total ab- 

 sence of limestones and of calcareous cements in the sand- 

 stones; (4) the tremendous thickness of the series; 

 (5) the ripple-marked and cross-bedded structure of 

 nearly all of the strata, sandstones and shales alike. 

 Whatever the theory for the origin and source of these 

 beds the above facts must be accounted for. Without 

 arguing the various possibilities and impossibilities of 

 such an accumulation, the writer ^vishes only to state that 

 the conditions involved appear to him to have been essen- 

 tially a gradually subsiding area into which a large river 

 throughout the subsiding period discharged its load. 

 How" large the basin of subsidence could have been, how 

 well-defined and what the shape of it was, are only matters 

 of conjecture with him. That the inflowing river, which 

 discharged its sediments into the bay or basin, was large 

 is attested by the absence of all conglomerates and coarse 

 sands, and by the silty nature of the deposits from top to 



