28 Bulletin 9 220 



It will be observed here that the Midwa}^ has been separated 

 out from the Lignitic, but that the Matthews' landing and Black 

 bluff beds are still retained in this stage. 



The distribution of the different substages of the Lignitic are 

 shown on a large geological map of the State accompanying this 

 work. 



Since the publication of these stratigraphic works Mr. Aldrich 

 has written two Bulletins ( Bull. Amer. Paleont. No's 2 & 8 ) 

 describing among other Eocene shells many from the Lignitic 

 stage. The present writer has also contributed an article to the 

 Proceedings of the Philadelphia Academy of Natural Sciences 

 wherein are described and figured several Lignitic species. 



Stratigraphy . — In passing down the Tombigbee from the last 

 characteristic Midway exposure, viz, Naheola, various bluffs are 

 seen on either side of. the river, blackish and clayey at first but 

 becoming more grayish or yellow and arenaceous downstream, 

 until the famous Nanafalia exposure is reached. Here fossils 

 which seem to be exceedingly scarce in the stretch just described, 

 become very noticeable. Here the river is deflected to the west 

 principally or primarily by an indurated ledge of marl which 

 shows a moderate southern dip. Its height above water depends 

 accordingly upon the exa(5l point examined and the stage of the 

 water at the time. 



The sedlion as given by Smith and Johnson is as follows : 



Section of Nanafalia landing, Tombigbee River. 



" I. Greensand marl, highly fo.ssiliferous, containing chiefly 

 Gryphcsa thirsce Gabb, but holding also Turritella morto7ii 

 Con., Flabellnm, and a few other fossils. This marl 

 makes a tolerably firm rock, with a line of indurated, 

 projecting bowlder-like masses 12 to 18 inches thick of 

 nearly similar material along the whole length of the 

 bluff and near the middle of the bed about 20 feet. 



"2. Dark blue, almost black, laminated clay, devoid of fossils, 

 but passing below gradually into a bluish marl... 3 to 4 ft. 



" 3. Bluish greensand marl, wnth a few shells in the upper 3 or 

 4 feet, but more highly fossiliferous below. This bed 

 contains a great variety of beautifully'' preserved and easily 

 detached fossils. The fossils can be collecfted only during 



very low stages of the water 8 to 10 feet. 



It is from the under side of the indurate masses that break off 



