Eastern and Southern United States. 471 



The sequence of sediments during the Upper Cretaceous 

 subsidence and emergence I have shown to be as follows: 

 1. littoral sands, 2. clays becoming more and more calcareous, 

 3. chalks ; (4) chalky clays, 5. sands. The sands of this last 

 stage are characterized throughout by the presence of glauco- 

 nite in perceptible quantities, an accompanying mineral which I 

 have never seen in any of the Texas sediments of the lower 

 beds. These glaucouitic beds may be almost pure, siliceous 

 sand with only a few grains of glauconite, as in the upper beds 

 at Arkadelphia. or almost pure greensand with little siliceous 

 sand as at Washington, Ark. Again, they may be imbedded 

 in a firm calcarous matrix, as in the so-called " rotten lime- 

 stone " which distinguishes it from the lower occurring chalk. 

 The beds may be white, brown, green, blue, gray, or deep red, 

 owing to varying of proportions of lime and moisture and the 

 oxidation constantly going on, but the mineral glauconite is 

 always present, and this presence (if glauconite be of organic 

 origin) indicates some uniform condition of habitat during sed- 

 imentation which will be further shown in the discussion of the 

 fossils. 



Thirty miles west of south of Arkadelphia the Little Mis- 

 souri, a stream parallel to the Ouachita cuts down to the same 

 glauconitic strata, as shown by the stratigraphic and paleon- 

 tologic identity. At the old town of Washington they are 

 again exposed by the drainage of Town Creek. Thence south- 

 ward they are concealed again by the Eo-Lignitic overlap, for 

 two hundred miles, until the county of Anderson* is reached, 

 wheie a hundred miles east of the main Cretaceous area in 

 Texas they are exposed by the cutting of the Trinity River. 

 This outcrop differs lithologically and paleontologically from 

 the underlying beds of the main body of the Cretaceous ex- 

 tending westward through Texas to Mexico, but is identical 

 with the Arkansas calcareous glauconitic beds above mentioned. 

 These glauconitic beds insensibly gradate downward into the 

 Exogyra Ponderosa clays, the top exposures of the main area 

 of the Upper Cretaceous formations in Texas, and geograph- 

 ically they are the nearest western deposits to those of Missis- 

 sippi and Alabama, the intervening area being obscured by 

 Tertiary and Quaternay deposits. Upon careful comparison of 

 fauna and sediment with those of the latter region there 

 is found such a striking similarity that there can be no possible 

 doubt of their general identity with Hilgard's section from the 

 Ripley to the Tombigbee inclusive, although no correlation of 

 minute horizons is attempted. The Mississippi and Alabama 

 beds are characterized by the same fauna and structure, and the 

 universal presence of glauconite which places them like the 



* This exposure lias been recently discovered by Dr. R. A. F. Penrose, Jr., of 

 the Texas and Arkansas state surveys. 



