THE C EN O ZOIC DEPOSITS OF TEXAS. 55 I 



The fossils, which, according to Mr. Harris' determinations, 

 are those characteristic of the Lignitic of Alabama, include the 

 following : 



Dentalium micro-stria? Heilp., Plenrotoma moorei Gabb, and 

 numerous others which are common to these beds and those 

 underlying or overlying them. 



In addition to the invertebrate forms these beds also contain 

 a varied and well preserved flora which has not yet been studied. 



Marine Beds. — The Marine beds are composed of sand, with 

 considerable amounts of glauconite, clays and iron ores, and are 

 the principal fossil-bearing beds of the series. The lower beds 

 contain extensive deposits of ferruginous sandstones and lami- 

 nated iron ores, while the upper comprise brown fossiliferous 

 sand, green sand marls, stratified black and gray sandy clays and 

 green clays, and are the principal fossil-bearing beds of the sub- 

 stage. Thin beds or laminae of carbonate of iron occur through- 

 out the entire section, but the heavier beds or ore deposits are 

 found toward the top of the lower beds. The lower ores are 

 laminated, while those above are nodular. 



The surface exposure of the Marine beds forms a broad ridge 

 or range of hills crossing the state from the east, where it forms 

 the greatest elevation of that portion of the Eocene belt, to the 

 southwest. Its topography is the consequence of the resistance 

 of the iron ore caps of the eastern plateaux or hills to erosive 

 agencies, and the similar service of the brown sandstones of the 

 west. In areal extent this is the most widely distributed of the 

 sub-divisions of the Eocene. 



In elevation it varies from 375 to 700 feet above sea level. 



The fossils are very abundant and well preserved, and among 

 those characteristic of it may be noted : 



Ostrea alabamiemis Lea, 0. sellaeformis Con. var, divaricata, Lea, 

 Anomia epliippioidcs Gabb, Modiola houstonia Harris, Yoidia clai- 

 bornensis Con., Vcnericardia planicosta Lam., Semele linosa Con., 

 Terebra houstonia Har., Cancellaria geinmata Con., Marginella 

 semen Lea, Terebrifnsus amcenis Con., T. costatus Lea, Levifitsus 

 trabeatoides Har., Nassa texa?ia Gabb, Murex vanuxemi Con., Dis- 



