i?. T. Hill — Texas Section of American Cretaceous. 293 



foot of the highlands (A) older than that of the plateau, and to 

 extend under it as shown in the following diagram. This 

 error, which was the fundamental cause of the confusion of 

 knowledge concerning the Texas cretaceous formation, has ex- 

 isted since Roemer's time.* 



Fig. 2. — The Austin New-Braunfels 2. 



Nox-coxfokmty, as Roemer thought it. A, 

 Rotten limestone of Black Prairie Region 

 ("Kreidebildungen am Fusse des Hoch- 

 lands, r Roemer), supposed by Roemer to ■"■" 

 extend under the escarpment. C, Lower Cretaceous of escarpment and plateau, 

 supposed by Roemer to rest on A. 



Upon investigation of the three divisions of strata along the 

 Austin New Braunfels non-conformity, the rotten limestone 

 group of the Black Prairie Region at its foot, the harder chalky 

 limestones of the scarp and plateau, and the intervening shales 

 exposed along their contact, the following facts are apparent. 



The Upper Division of the Texas Cretaceous. 



The Rotten limestonef underlying the Black Prairie is a deep 

 marine formation of much uniformity. Its strata are of great 

 thickness and constitute a well-defined group. They are over 

 1500 feet at Spofford's Junction, as determined by artesian 

 borings, and over a thousand in the Dallas and Austin regions. 



The limestone of this upper formation, and its included yel- 

 low marls, extend into Arkansas and Mississippi on the north 

 and Mexico on the south. The lower portion is composed of 

 uniform sediments of deep marine origin, containing few mol- 

 luscan remains, except giant Inocerami and a small Grryphasa- 

 like Ostrea, found also in the Fox Hills and Pierre of Meek 

 and Hayden, and Tombigbee sands and Rotten limestone of 

 Hilgard, the exceedingly numerous varieties of which have 

 been described under at least a dozen names:]: in different 

 reports. 



gist with the No. 2 of Meek and Hayden, while the lower part of the formation is 

 said to represent No. 3. Without criticising; their determination it may be ob- 

 served that the fault which should exist has been observed at various lines along 

 the elevatioD. I found it crossing the Heliotes Creek, eighteen miles west of 

 San Antonio, at a locality pointed out to me by Mr. Gabriel W. Marnoch." 



* Roemer confessed (see " Texas,") that he had not seen this contact, and that 

 his conclusions, here shown to be erroneous, were based upon hypotheses. This 

 was the fundamental and radical error in his otherwise excellent, work. 



f Roemer did not separate these limestones from the underlying shales, but 

 described them together as the Cretaceous at the foot of the highlands, and erro- 

 neously thought, as shown on a previous page, that they extended under instead 

 of resting unconformably upon the limestones of the escarpment. Shumard 

 failed to detect Roemer's error, and fell into the same mistake. The two are 

 easily separated in Roemer's writings by interpreting his careful descriptions of 

 the strata and fauna of the waterfall and the ford near New Braunfels. — Kreide- 

 bildungen von Texas, p. 11. 



X Gryphcsa Aucel/a (Lamck.) Roemer ; G. vesicularis Roemer (not Lamck.) ; G. 

 Pitcheri Hilgard, not Mort. ; Ostrea patinia M. and H. ; G. mutabilis Con. ; 0. 

 Artomioformis Hilg., not Roemer, most of which and many more varieties 

 inseparably occur in the same localities. 



