FLORA OF THE TRINITY FORMATION. 329 



Mr. Robert T. Hill, who had had the advantage of a number of years' 

 residence in Texas, studied its geology with great care and worked 

 out the stratigraphical relations of the beds with much greater exact- 

 ness than any of his predecessors. To him, in fact, we are indebted 

 for the first correct section. After joining the staff of the United States 

 Geological Survey as chief assistant to Dr. C. A. White, his work was 

 verified by the latter, who went personally over the ground. 



In February, 1887, Doctor White published a paper" giving the results 

 arrived at so far as the Cretaceous was concerned. In the section given 

 on page 40 of that paper the Comanche series is recognized and the 

 lowest bed is called the "Dinosaur sands." It is described by Mr. Hill, 

 who, as Doctor White states, wrote "the remarks at the right-hand 

 side of the column," as "coarse silicious sand, popularly called 'pack- 

 sand.' Occurs between the base of the fossiliferous Cretaceous and the 

 Carboniferous series. Contains vertebrate remains." 



In April of the same year appeared Mr. Hill's paper * on the Cross 

 Timbers, with his own much fuller section of the Cretaceous of Texas 

 (pp. 298-299). It is the same in its more general features as the sec- 

 tion given in Doctor White's paper, except that Shumard's name "Austin 

 limestone" is substituted for the name Dallas limestone; but much 

 fuller historical, stratigraphical, and paleontological data are here given. 

 The term "Dinosaur sand" is still retained for the basal beds representing 

 the Upper Cross Timbers. The Lower Cross Timbers are shown to occupy 

 a belt at the base of the Upper Cretaceous, which, therefore, practically 

 corresponds to the Dakota formation. In these sections the whole of the 

 Comanche series is shown to be Lower Cretaceous and the basal sands 

 to be at the boundary line between the Cretaceous and the Jurassic. 



Six months later Mr. Hill published a second paper on the Texas 

 Cretaceous,'' further discussing the stratigraphical relations. On pages 

 305-306 of this paper he says : 



The basal or Dinosaur sands of my section, which are interpolated between 

 the Fredericksburg division and the undoubted Carboniferous, are the shore detritus 



a On the Cretaceous formations of Texas and their relation to those of other portions of North America, 

 by Charles A. White: Proc. Acad. Nat. Sci. of Philadelphia, 1887, pp. 39-47. 



6 The topography and geology of the Cross Timbers and surrounding regions in Northern Texas, by Robert 

 T. Hill: Am. Journ. Sci., 3d ser., Vol. XXXIII, April, 1887, pp. 291-.303, pi. vi (map). 



c The Te.\as section of the American Cretaceous, by Robert T.Hill: Am. .Journ. Sci., 3d ser., Vol. XXXIV, 

 October, 1887, pp. 287-309. 



