W. J. McGee — Geology of the Mississippi Valley. 359 



vegetable matter are found associated. It is not very uncommon 

 indeed for the vegetation itself to be converted into lignite. Though 

 there is generally a thin stratum only of this member so highly 

 bituminous, it is not very rare to find the whole mass so rich in 

 carbon, nitrogen, etc., as to act as an excellent fertilizer. 



It is very common to find wood in this member, which may be 

 either in the shape of small fragments, or of trunks and branches of 

 trees. These may be sound, and so slightly mineralized as to burn 

 readily, or they may be almost wholly decomposed. The species 

 represented are usually identical with those now found on the 

 surface in the same region ; but there is a much larger proportion of 

 coniferous trees in the drift than growing upon the present surface. 

 Endogenous plants of undetermined relations have also been 

 observed, as well as cones, leaves, etc., though these are so indiffer- 

 ently preserved, and in so fragile a matrix, that they cannot be 

 successfully studied. It is impossible to get good specimens into the 

 hands of palaao-botanists. These remains are very abundant near 

 Otterville, Jersey county, Illinois, where the structure containing 

 them (and which is largely made up of vegetable humus, with many 

 logs and fragments of wood and bark) rests upon the Keokuk Lime- 

 stone (the third formation above the base of the Sub-Carboniferous, 

 noted for its geodes), and is overlaid by (1) 20 feet of blue clay, 

 •with a few boulders, and (2) 20 feet of brown clay, with a little 

 gravel and a few boulders near its base. Coniferous trees are not 

 now found in the vicinity. Peat is also found occasionally, but is 

 usually quite metamorphosed. Sometimes, however, its mass is well 

 preserved, as in the case of a stratum a foot in thickness just 100 

 feet below the surface in Mendota, Illinois, passed through in boring a 

 well. Many specimens of well-preserved Sphagnum were obtained, and 

 several, mounted on slides, have been placed in the hands of the writer. 



Bones, and rarely shells, are reported from this member. None of 

 the latter to which any value could be attached have been examined. 

 A cranium of Bison latifrons, and an abnormally developed molar 

 belonging to some member of the Ox family, which cannot 

 be identified, have been found in place in this formation. Two 

 molars of Equus complicatus, Leidy (perhaps E. major, De Kay), are 

 believed to be from this member, but both were found where the 

 total thickness of the drift was limited, and the divisions not well 

 marked. Charred wood has been observed in several instances. 



With some reservation it may be said that these organic remains 

 occur indiscriminately in all parts of the member. When it is 

 wholly unstratified, however, they are most commonly found only 

 at or near its surface, and occasionally extending slightly into the 

 superimposed deposit. This is quite general beyond the southerly 

 limit of member number three. Thus in Ohio, the " forest bed " 

 (as it was designated by Dr. Newberry) occurs above the blue clay, 

 and seems to be distinct from it. The colouration of the clay of this 

 member is suspected to be due to the action of the carbonic acid set 

 free in the decomposition of the vegetation of the ancient surface, in 

 liberating the iron from the rocks and earths, and permitting it to 



