62 



Indiana University Studies 



by a shell. The presence of a shell covering might, no doubt, 

 favor the formation of the columns, the shell often being more 

 resistant to solution than the opposite rock mass. Shell cov- 

 erings, when present, often show distinct signs of corrosion — 

 a distinct evidence in support of the solution theory. Wag- 

 ner's investigations of the Muschelkalk stjdolites revealed the 

 frequent occurrence of fossil coverings which determined the 

 shape of the columns. The fossils of the Muschelkalk, how- 

 ever, are much larger than those of the Indiana limestones. 

 Wagner treats of the subject in much detail (Wagner, 1913, 



Fig. 28. — Example of a brachiopod shell partially penetrated 

 by a column of a small stylolite-seam. Mitchell limestone. 

 Two times natural size. 



Fig. 29. — Mussel shells pierced by stylolites. (After Wagner.) 



The smoothness and sharpness with which the edges of 

 stylolites are cut is striking. Close inspection of the columns 

 shows that the hundreds of fossils, oolitic grains, mineral 

 crystals, etc., have been sharply smoothed off at the contact 

 of the sides of the penetrations. The missing remains are 

 not to be found. The lower, coarsely fossiliferous portion of 

 the Harrodsburg limestone reveals many examples of this, 

 and microscopic examination of the fine-grained Salem lime- 

 stone gives an abundance of distinct evidence. Above or 

 below the stylolite-seams are often found remains of brachio- 

 pods, gastropods, bryozoans, etc., which have been pierced, or 



pp. 119-121). 



