10 Hill Paleontology of tlie Trinity Division. 



owing to the fact that the fundamental problems concerning the 

 sequence and relative importance of its subdivisions had not 

 been presented until lately, although the identity of the scries, 

 as a whole, was made known in 1886. Prior to that time most 

 of its fossils had been described by Shumard, Roemcr, and others, 

 but it was supposed that the species all came from beds which 

 w r ere in some manner equivalents of the upper Cretaceous or the 

 well known Meek and Hayden section. Since the writer ascer- 

 tained that the Comanche Series was a distinct and lower Cre- 

 taceous formation he has spent several years in studying the 

 subdivisions and their extent, in ascertaining the stratigraphic 

 position of the fossils or faunas already described, and in ar- 

 riving at a rational system of nomenclature.* These steps were 

 necessary before the homotaxy of the scries could be discussed. 



In early papers by the writer ,f pending more minute study 

 of details, the Comanche Series was broadly divided into two 

 divisions or convenient groups of strata, as follows : 



(1) An Upper or Washita Division, so named because of its 

 prevalent occurrence in the vicinity of Old Fort Washita, Indian 

 Territory, whence some of the species, which I ascertained were 

 peculiar to this division, were originally described by Professor 

 Jules Marcou and the brothers Shumard. (2) A Lower, or 

 Fredericksburg Division, J so named because many of its char- 

 acteristic species were those described originally from the vicinity 

 of Fredericksburg, Texas, by Dr. Ferdinand Roemer. 



In 1887, while studying the Cretaceous formations of Arkansas, 

 the writer discovered that the beds of the Fredericksburg Divis- 

 ion, so called, consisted of two well-defined groups of strata, 



*The Comanche Series of the Arkansas-Tex^is Region, by Robt. T. Hill : 

 Bull. Geol. Soc. of America, vol. ir, pp. 503-528. 



fThe Topography and Geology of the Cross-Timbers and Surrounding 

 Regions in Northern Texas : Am. Journ. Sci., vol. xxxn, April, 1887. 



J Tt has been alleged (Third Annual Report Texas Geological Survey, 

 p. 272, and American Geologist, January, 1893), that the term Fredericks- 

 burg Division was originated by Dr. Ferd. Roemer. Inasmuch as Dr. 

 Roemer never recognized the existence of the Comanche Series, it is im- 

 possible to suppose that he named its divisions, and from none of his 

 writings can such an inference be made* 



\ The evolution of knowledge concerning the Cretaceous formations of 

 Texas prior to the writer's publications is set forth in Bulletin 45 of the 

 TJ. S. Geological Survey. 



