100 PROCEEDINGS OF THE ACADEMY OF [1895. 



The same characteristics prevail in Houston County where the 

 base comprises a series of blue and brown laminated gypsum- bearing 

 beds showing a section of : 28 



1. Ferruginous gravel talus from Cook's Mountain. 4 feet. 



2. Thinly laminated brown clays 4 " 



3. Thinly laminated dark blue clays with inter- 



laminae of brown sand and crystals of selenite . 6 " 



4. Fossiliferous brown sand, containing an extensive 



fauna, including, among others, Anomia ephip- 

 pioides Gabb; Volutilithes petrosa Conrad; 

 Venericardia planicosta Lam.; Calyptrophorus 

 velatus Conrad, 29 and forming an intermediate 

 bed of the marine stage 10 to 15 " 



Towards the western side of the same county these clays give place 

 to massive brown sands and clays containing broken plant remains 

 and sheet-like formations of crystalline gypsum. Still farther west, 

 in Grime and Brazos Counties, gray sand forms the prevailing 

 characteristics. 



While towards the eastern end of the area it may be broadly stated 

 that the clays are gypseous throughout and, as in the northern edge 

 of Polk County, the overlying Fayette sauds rest upon heavy beds of 

 blue gypseous clays. The same conditions do not hold good along the 

 contact between these divisions in the western portion. In Houston 

 County, while the gypsum is pretty generally distributed throughout 

 the whole of the series, the heavier deposits of that material occur 

 towards the base ; and in Brazos County the gypsum- bearing beds 

 appear only at, or close to, the base of the division and is there over- 

 laid by a series of dark blue clays containing broken plant remains, 

 gray sands and sandy clays and the Fayette sands rest upon laminated 

 or thinly stratified banded dark brown and yellow clays showing 

 everywhere a heavy sulphur efflorescence. 



The sauds belonging to this series of deposits are blue, brown and 

 gray in color and lie in beds from a few inches to over fifty feet in 

 thickness. The gray sands form the prevailing type and occur over 

 the whole area, but are better developed in Houston, Grime and 



28 [bid., i>. 17. 



29 Harris, M.S., Monograph of Texas Tertiary Fossils. . 



