112 PROCEEDINGS OF THE ACADEMY OF [1895. 



man beds exist almost wholly in the form of casts, whereas, on the 

 other hand, the fauna of the Cook's Mountain, or upper beds, is 

 beautifully preserved, many being in a very perfect condition and 

 exist in great numbers. 



In crossing the whole series from north to south the first indica- 

 tion of well preserved fossils in the east occurs in the southern por- 

 tion of Rusk County, near Mount Enterprise, and on Stevens branch, 

 a tributary of Shawnee Creek. Farther west they are found in 

 Cherokee, south of Jacksonville, a few miles west pf Palestine, in 

 Anderson, near the mouth of Elkhart Creek, in Houston, near Cen- 

 treville, in Leon, and south of Franklin, in Robertson County, and 

 near the Burleson County north line on the Brazos. These locali- 

 ties may therefore be taken as approximately indicating the northern 

 line of the "Cook's Mountain " or upper series of the Marine beds 

 as known in Texas, but it must be remembered that on the eastern 

 side very extensive erosion has taken place, and probably these beds 

 may have extended much farther north. At any rate the line may 

 be considered as only an approximate division of what evidently 

 constitutes but one stage of the Eocene. 



To. the south of this approximate boundary we have an extensive 

 series of green sands, glauconitic sands, ferruginous sandstones, clays 

 and iron ores in most resj>ects similar to those lying north of it. The 

 green sands, as a general thing, are less altered and more glauconitic, 

 the sands less indurated and the iron ore deposits much heavier and 

 almost altogether laminated. The fauna is very much richer both 

 in species and number of specimens, and the fossils all in a good 

 state of preservation and easily obtainable. 



While these beds are known to exist in isolated hills throughout 

 the counties of Rusk, Nacogdoches, San Augustine and Sabine 

 Counties, lying east of the Angelina River, no satisfactory sections have 

 been obtained and only a few of the fossils from these areas have been 

 determined. According to Professor Heilprin 41 these include Veneri- 

 cardia transversa Lea, Crassatella texana Heilp., Pecten deshayesii 

 Lea, Ostrea alabamensis Lea, 0. sellosformia Lea and var. divaricata 

 Lea, from San Augustine County. Pectuneulus idoneus Con., and 

 Ostrea sellceformis, var. divaricata Lea, from Nacogdoches County, 



" Proceedings A.cad. of N. S., Phila., Oct. 1800, pp. 303-404. 



