332 MESOZOIC FLORAS OF UNITED STATES. 



Doctor White's Cretaceous correlation paper" appeared in 1891, 

 in which the Texan region is treated at some length. He recognizes 

 the Trinity division, but does not subdivide it. He makes it coordi- 

 nate with and not a part of the Comanche series, and considers that the 

 latter is separated from the former by a hiatus. Both Doctor White 

 and Mr. Hill continued erroneously to correlate the Trinity with the 

 Tuscaloosa. 



It was in 1891 that, on my return from Mexico, I visited the Lower 

 Cretaceous areas of Texas and Arkansas, guided at first by Mr. Hill, 

 who, however, was obliged to return to Washington before I had com- 

 pleted my investigation. We examined the Arkansas beds first, arriv- 

 ing on October 5 at Centerpoint, in Howard County, and working three 

 days in the Trinity belt that stretches across that part of the State 

 from east to west. Near the old Fort Towson road north of Centerpoint 

 is a lignite bed belonging to the Trinity. The lignite is identical with 

 that of the Potomac formation in general appearance, mode of preser- 

 vation, and character of fracture. With it occur jointed stems of 

 Frenelopsis varians subsequently described from Texas by Professor 

 Fontaine. B}' far the best exposure found was that of Plaster Bluff, 

 a great gypsum cliff on the right bank of the Little Missouri Pv,iver, 3 

 miles south of Murfreesboro, Pike County. About 80 feet of the Trinity 

 are here exposed, overlain by 30 feet of superficial deposits. Vast 

 quantities of lignite occur above heavy beds of variegated clays greatly 

 resembling those of the Potomac formation in Virginia. Above the 

 lignite beds are the alternating marine shell-bearing beds, which are 

 also gypsiferous. The lignite bed contains considerable vegetable mat- 

 ter, chiefly black fragments of stems, similar in all respects to those 

 found farther west. Frenelopsis varians Font, was the most common 

 form and most of the impressions were indeterminable. 



The principal collection was made at Plaster Bluff, and this was 

 sent to Professor Fontaine, but not at the same time as the collection 

 from Glenrose, Tex., presently to be mentioned. I did not suppose 

 there was anything determinable in the Plaster Bluff material, and 

 placed it in a drawer. Several years later it was sent to him along with 



« Correlation papers, Cretaceous, by Charles A.White: Bull. U. S.Geol. Surv. No. 82, 1891. See pp. 

 114-130. 



