PALEONTOLOGIC METHODS EMPLOYED. 9 



essentially fringed directly against the old continent. Even the FeiTugi- 

 nous sandstone appears here and there to have been either overlapped b^- 

 the coal or eroded prior to the deposition of the latter. Thus, as Dr. Britts 

 informs me, in artesian well No. 2, at Clinton, this sandstone was met at a 

 deptli of 40 feet, and was found to be about 20 feet thick ; but at well No. 

 1, aboiit 1 mile distant, no sandstone was found, the cherty Mississippian 

 floor being reached at a depth of 50 feet. 



From the foregoing stratigraphic references it appears (1) that the plant 

 collections from Henry County, which furnished by far the greater jjart of 

 the material herein considered, come from two horizons about 45 feetajjart; 

 and (2) that these liorizons may be separated from the old Mississippian 

 land surface by an observed thickness of nearlj^ 100 feet of Mesocarbon- 

 iferous sediments in the direction of deeper water, or that they may, land- 

 ward, rest practically in direct contact with the old shore line in that region. 



It is possible that in that portion of the State farther southwest, as in 

 Barton County, in which the Lower Coal Measures sections can not defi- 

 nitely be correlated as to principal details with those of Henry County or 

 the comities farther north, beds of the Lower Coal Measures and Pottsville 

 series extending for some distance below the horizon of the Jordan coal may 

 come to light along the western flank of the Ozark uplift. It is certain that 

 the Pottsville is developed and is coal-bearing near Fayetteville in Wash- 

 ington County, Arkansas. But in the region of Henry County, at least, the 

 richly phytiferous roof shales of the Jordan coal mark the time when the 

 continental subsidence reached the vicinity of Clinton, and the abundant 

 and varied flora is of a date which approximately marks in this region the 

 close of the period intervening' since the uplift of the Mississippian. 



PALEONTOLOGIC METHODS EMPLOYED. 



In the following notes and discussions it has seemed best to j^ublish the 

 results of a critical study and comparison, constituting essentially a revision 

 of manj^ of the species originally described from Missouri, as well as to 

 give more detailed descriptions of or observations pertaining to other species. 

 The descriptions of the species are based entirely on material from Mis- 

 souri, and it is hoped that they are generally given in sufficient detail to 

 enable geologists as well as paleontologists to recognize the various forms 

 in the field. In some instances the scope of species has been narrowed and 



