CONCLUSIONS. 337 



rence. The Ammonitidse, Vertebrata and Mollusca have not yet been 

 critically classified in" print with reference to the light they may throw 

 upon the age of these beds, yet without this essential data the fiat has 

 frequently gone forth that no correlation can be made between the North 

 American Cretaceous and that of similar life periods throughout the 

 world. • Without facilities for the publication of a monograph upon the 

 fossils of the Texas section, the writer is at a disadvantage in presenting 

 conclusions, but the faunal charts exhibited at the reading of this paper, 

 but which lack of space prevents publishing, showed that there are sub- 

 stantial grounds for the following conclusions : 



We have in the North American Cretaceous, as represented in the 

 Texas section, as complete a succession of beds and faunas as is repre- 

 sented in any known geographic division of the world. 



The sequence of life in these beds is such as to justify, in discussing 

 the North American Cretaceous, the application of a more definite sub- 

 division of terms, in harmony with world-wide nomenclature — terms to 

 be used as Eocene, Miocene and Pliocene are employed in America in 

 speaking of the much less defined divisions of the Tertiary. 



The North American Cretaceous, of the Atlantic sedimentation, pre- 

 sents the following strong analogies to the European: 1. It is divisible 

 into two distinct systems — an Ui)[)er and a Lower — separated by an epiro- 

 genic land elevation and stratigraphic break. 2. It is divisible into sub- 

 groups, based upon life forms and associations, such as the Neocomian, 

 Gault, Cenomanian, Turonian and Senonian, of the equivalency of the 

 term Eocene, as applied to the Tertiary. 



Some of these divisions, so far as studied, such as the Neocomian 

 (Trinity and Fredericksburg divisions), Turonian (Benton division) and 

 Senonian (Glauconitic), reveal a close homotaxial similarity of generic 

 forms to those of other portions of the world. 



Tha following is a list of the papers on tiie geology of the Te'xas region published by the author : 



Present Condition of Knowledge of the Geology of Texas (1886). Bulletin 45, U. S. tteological 

 Survey, Washington, 18^7. 



The Topography and Geology of the Cross Timbers and Surrounding Regions of Northern Texas. 

 Am. Jour. Sci., April, 1887. 



The Texas Section of the American Cretaceous. Am Jour. Sci., October, 1887. 



Events in North American Cretaceous History, illustrated in the Arkansas-Texas Region. Am. 

 Jour. Sci., April, 1889. 



A Portion of the geologic Story of the Colorado River of Texas. American Geologist, May, 1889. 



Neozoic Geology of Southwestern Arkansas. An. Report of Arkansas Survey for 1888, vol. 11. 



Classification and Origin of the chief geographic Features of the Texas Region. American 

 Geologist, January and February, 1890. 



A brief Description of the Cretaceous Rocks of Texas, and their economic Value. Annual Report 

 of the Geological Survey of Texas for 1888. 



'■ Report of Mr R. T. Hill." Ibid., pp. Ixxxiii-lxxxviii. 



XLVI— Bur.r. GEor, Soc. Am., Vor,. 5, 1893. 



