FLOKA OF THE TRINITY FORMATION. 341 



In his paper describing this organism Doctor Knowlton says that the 

 specimens in which it occurs "came from a gulch on one of the smaller 

 branches of the Muddy Fork of Little River, about 6 miles northeast of 

 Centerpoint, Howard County. The deposits containing these fossils were 

 referred by Professor Hill to the Trinity division of the Lower Cretaceous. ' ' 

 He was unable to fix its systematic position, and treated it as a new genus, 

 which he named for Mr. Hill and called the form Paleohillia arkansana.'^ 

 Mr. Theo. Holm published a criticism of Doctor Knowlton's conclusions 

 relative to this form,** but as he did not himself see the specimens his 

 conclusions are entitled to little weight. 



I have now enumerated all the vegetable remains (with the exception 

 of "an undescribed endogenous plant resembling Equisetum ' ' " from the 

 Arietina beds of the Washita division) that have thus far been reported as 

 having been found in the Comanche series of Texas and Arkansas, and have 

 given a somewhat full account of the history of the discovery of fossil 

 plants in the Trinity formation. Although the flora has thus far proved 

 meager, it is sufficient to show, even if the fauna and the stratigraphy 

 failed to do so, that the Trinity formation is of Lower Cretaceous age. The 

 absence of dicotyledons, however, seems to place it at the very base and 

 give it homotactic rank with the Knoxville and the Kootanie. 



The Twenty-first Annual Report of the United States Geological 

 Survey, Part VII,'' which bears date 1901, but really did not see the light 

 until May, 1902, constitutes Mr. Hill's final contribution to the geology of 

 Texas, and would seem to exhaust the subject. The Black and Grand 

 prairies occupy most or all of the Cretaceous terranes within the State, 

 although they are not confined to them, and their description afforded Mr. 

 Hill an opportunity to deal at length with the beds that have chiefly 

 occupied us thus far. He has, however, made scarcely any change in the 



classification of the rocks, and adheres to the conclusions last announced 



= \_ 



« Description of a new problematical plant from the Lower Cretaceous of Arkansas, by F. H. Knowlton: 

 Bull. Torr. Bot. Club, Vol. XXII, September, 1895, pp. 387-390, figs. 1-3 on p. 388. 



!> Remarks upon Paleohillia, a problematic fossil plant, by Theo. Holm: Botanical Gazette, Vol. XXI 

 April, 1896, pp. 207-209, pi. xvii. 



'■ Bull. Geol. Soc. Am., Vol. V March 22, 1894, p. 322, in Geology of parts of Texas, Indian Territory, and 

 Arkansas adjacent to Red River, by Robert T. Hill: Ibid., pp. 297-338, pi. xii, xiii. 



'' Geography and Geology of the Black and Grand Prairies, Texas, with Detailed Descriptions of the Creta- 

 ceous Formations and Special Reference to Artesian Waters. By Robert T. Hill, Washington, 1901, 666 pp., 

 71 pis. (6 of which are maps), 80 text figs. 



