Geological Problems in Muscatine County. 15 



coal. At one locality on Pine Creek, above Wild Cat Den, 

 this sandstone is somewhat more indurated than usual, and is 

 quarried to supply the local demand for building stone. 



The coal seam which appears everywhere to accompany 

 the Carboniferous shales and sandstones of the region, varies 

 in thickness from eight or ten inches to two or three feet. 

 For the most part the coal is of inferior quality, being more 

 or less shaly, and containing large quantities of pyrites of 

 iron. At a few localities, however, notably near Buffalo, the 

 coal has been profitably worked. 



The Devonian sandstone, as developed at and near Mont- 

 pelier, seems not to have a very wide geographical distribu- 

 tion. The conditions favoring its deposifion were evidently 

 local. In the particular locality affected by them, these con- 

 ditions, whatever they may have been, operated disastrously 

 on most of the Devonian fauna. During a part of the time, 

 however, Sfirijera ■parryana found the conditions unusually 

 favorable. The great number of casts of this species occur- 

 ring in the spirifer-bearing layer would indicate that the sea- 

 bottom was fairly crowded for a time with large, healthy, 

 vigorous individuals; and that the species occupied the region 

 to the almost total exclusion of ever3'thing else. S-pirifera 

 aspera, the constant associate of S. parryana in the under- 

 lying Hmestones is almost entirely absent, only two or three 

 S. aspera being seen among many hundred S. parryana. 

 Even Atrvpa reticularis, that most ubiquitous of all Devonian 

 brachiopods, apparently capable of living anywhere and under 

 any circumstances, was represented by a comparatively few 

 widely scattered individuals. The Ort/iis iowensis attained a 

 larger size than usual, but the number of individuals was 

 small. Athyris vittata which is one of the most abundant 

 shells in the subjacent limestones, is unrepresented in collec- 

 tions from the sandstone. In the fossiliferous portion of the 

 sandstone individuals of Strophodonta deniissa are about as 

 numerous as in the limestone. 



It is only in one la3er, and that not very thick, that Spiri- 

 fera parryana occurs. Some of the species mentioned persis- 



