Seventeenth Annual meeting. Ill 



on some estuarian Hat between ebb and ebb. It is possibly a small fraction of an inch 

 between spring tides. In one place, in Ellsworth county, a deposit, tilled with leaves 

 from bottom to top, is from ten to fifteen feet thick. The leaves not huddled together, 

 but evenly distributed, and often lying perfectly fiat and straight. It was a time of 

 what might well be called permanent conditions of climate. Yet there was all the while 

 going on a gentle subsidence of the whole region, and this subsidence was the certain 

 prelude of change, and the change came at last, and changes many have been since then. 

 We have, in collecting specimens of the Dacotah Hora, encountered a difficulty in 

 identifying species, which lies not only in the way of amateurs, but is also a trouble to 

 specialists. The difficulty we refer to is that caused by not readily recognizing what 

 particular form of fossil we have found, and which form is figured or described in the 

 books we use. About fossil leaves, we remark that there are five forms, any one or two 

 of which may be presented to us by a particular specimen, and all of which, for each 

 species, should be in position in a typical cabinet. 



1. There is simply the impression that the leaf may have left on the material with 

 winch its upper surface was in contact. 



2. The similar impression made by the under side of the leaf. 



3. The leaf itself may be petrified, and we may see the upper surface of it. 



4. The petrified leaf may be adhering by the upper surface, and we may see the under 

 side. 



5. The leaf itself may all have been dissolved away without other material taking 

 its place, leaving a thin cavity between the impressions of the upper and lower sides 

 which a tap of the hammer may lay open. 



These same forms, essentially, if not numerically, occur for all kinds of fossils. A 

 locality a few miles from Lawrence gives us beautiful internal and external casts of a 

 gasteropod-pleurotomarid spharulata, as well as the fossil itself. We have on the table 

 a plaster cast taken from the external impression of a Dacotah bivalve. Having often 

 experienced the difficulty above referred to, and sometimes found specimens of which 

 the form was readily distinguishable, we have thought it worth while illustrating this 

 point by some experiments in plaster with leaves from trees now growing in Kansas. 

 And we have a few fossils illustrating some of the forms. Those fossils best illustrating 

 forms three and four are those of thick coriaceous leaves. 



BUILDING STONE. 



In Ottawa and Washington counties, the Dacotah yields a heavy, dark-brown stone, 

 which can be readily worked, and where used in squared blocks makes a very handsome 

 building material, and is well set off by sills and corners of the neighboring Benton, or 

 Permian, limestone. The rough, ferruginous sandstones, and even the softer varieties, 

 supply building material of various qualities all through our Dacotah region. 



COAL. 



In several counties — Washington, Republic, Lincoln, and Russell — seams of an inferior 

 quality of coal have been found. It is lignite, having much pyrites and a large quan- 

 tity of ash when burned. It is, however, of some use as household fuel where the thick- 

 ness of the seam is sufficient to pay for working it. Professor Mudge indicates that there 

 is one horizon for several of these seams. It would be valuable geological service to de- 

 termine the position of that horizon, and if it was a continuous seam now broken by ero- 

 sion, or whether the localities indicate a series of islands or basins. Though the term 

 lignite indicates the presence of wood fiber, yet we have no idea that any considerable 

 part of this material was wood, for it has been shown conclusively by experiments, the 

 results of which are confirmed by our experience of modern forests, that wood fiber, 

 especially of the higher kinds of trees, is not preserved in the conditions under which 

 coal was formed, so well as material of the leaves, stems and seed vessels of the under- 



