298 R. T. Hill — Texas Section of American Cretaceous. 



tion to a theory of the considerable hiatus between the deposits 

 of the basal Eutaw clays and part of the Mississippi section 

 above them. 



The Lower Cross Timber series (Dakota sandstone of 

 Shumard, Trans. St. Louis Acad., vol. ii, 1862) which under- 

 lie these shales in northern Texas, are entirely missing south of 

 Waco, and hence do not appear at Austin. Whether this is 

 due to their having been eroded away before the deposition of 

 the shales, or to their having never been deposited, the writer 

 does not feel prepared to state. 



I have also traced the continuity of the Lower Cross Timber 

 (Dakota sandstone?) division from the Texas Pacific railroad 

 to Red river in the vicinity of Denison, and demonstrated their 

 identity with the arenaceous group of Shumard's section, which 

 with the so-called Marly clays he placed erroneously at the 

 base of the whole Texas section. A j^ear after the publication 

 of his original section Dr. Shumard decided these arenaceous 

 beds to be equivalent to the No. 1 (Dakota sandstone of Meek 

 and Hay den.) 



Concerning the relative age of the Dakota sandstone of 

 the Rocky Mountain region, with which these beds in Texas 

 are probably identical, Meek says : " Up to this time we also 

 know of no single species being common to it and any of the 

 beds above; but then we as yet know but comparatively few 

 species of animal remains from this rock; one of these, how- 

 ever, belongs to the Cretaceous genus Leptosolen while the 

 other shells are allied to Cretaceous species and unlike Jurassic 

 forms. In addition to this the modern affinities of the numer- 

 ous leaves of the higher types of dicotyledonous trees found in 

 it, present a strong objection to the adoption of the conclusion 

 that it may belong to a lower horizon than the Upper Green- 

 sand of British geologists; while its position directly below 

 beds almost beyond doubt representing the lower or Gray 

 Chalk, precludes its reference to any higher stratigraphical com- 

 position. Consequently we have long regarded it as most prob- 

 ably representing in part, if not the whole, of the Upper Green- 

 sand." The fossils described by Dr. B. F. Shumard from the 

 Red river country include forms from horizons between the 

 basal portion of the Rotten limestone of Division A, such as the 

 Ostrea belliph'cataj- Shurn. (including the Eagle Ford shales at 

 the Lower Cross Timber beds) and from the top portion of the 

 Comanche series, such as Ammonites Swallovii, etc. These 

 horizons have not been fully studied but they represent all the 



* In the vicinity of Denison the upper part of the Comanche series, the 

 Lower Cross Timber sands, and the Eagle Ford shales succeed each other almost 

 inseparably, so that there, instead of the sharp lines of demarcation between the 

 three groups as at Austin, we have a gradual transition between all the beds. 



+ Ostrea Blackii, of White. 



