1895.] NATURAL SCIENCES OF PHILADELPHIA. 107 



and then tbey corresponded to a lower division of the Moseby Ferry 

 section than those found near Elm Creek. Moreover, on the south 

 prong of" Thompson's Creek, about eight miles north of the well 

 boulders and of ferruginous fossiliferous sandstone occur imbedded 

 in the yellowish gray sandy clay of the Yegua beds. 



The correlation of any of these three stages — the Frio clays, 

 Fayette sands and Yegua clays — with the deposits of Louisiana lying 

 immediately to the east is attended with more or less difficulty and 

 doubt from the fact that little or no work, and that of the most 

 general character, appears to have been done in that portion of the 

 State. The Grand Gulf, according to both Hilgard and Hopkins, 

 appears to have embraced the upper two and at least a portion of the 

 Yegua clays besides the upper calcareous sandstones, and was, accord- 

 ing to these writers, above the Vicksburg. The lower portion of the 

 Yegua clays were apparently considered by them to be of Jackson age. 

 Dr. Hilgard says, after describing the Grand Gulf formation: "On 

 the Sabine River, ' too, the upper portion of the profile is pretty 

 correctly reproduced. At the base of the Grand Gulf rocks we find 

 on the Bayou Taureau a seam of shell- limestone with Vicksburg 

 fossils. We then pass over lignito-gypseous strata to Sabine Town, 

 Texas, where we see about seventy feet of these overlying ledges of 

 blue fossiliferous limestone alternating every two or three feet with 

 what would be green sand marl like that of Vicksburg had not the 

 lime of the numerous shells, of which it contains casts, been removed 

 by subsequent dissolution. So far as I have seen, the usual leading 

 tbssils of Vicksburg are wanting here, while the greater saudiness of 

 the materials, as well as the prevalence of shallow sea bivalves indi- 

 cates their deposition in shallower water. As we proceed north- 

 ward from Sabine Town liguitic clays and lignite alone separate, and 

 sometimes altogether replace the limestone ledges which themselves 

 become poorer in fossils as we approach the northern edge of the 

 formation." 37 



According to Hopkins the Jackson beds consist of marine strata 

 with characteristic fossils of lignite and non-fossiliferous beds and 

 laminated sands and clays and among the marine beds massive beds 

 of clay full of selenite. 38 



37 Geol. Reconn. of La., American Journal of Science, Second Series, Vol. 

 XLVIII, 1869, p. 338. 



38 First Annual Report Louisiana State Geol. Survey, 1869, pp. 94-90; Second 

 Annual Report Louisiana State < }eol. Survey, 1871, pp. 7 to 84. 



