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



divisions after the typical localities of each, and where thejr 

 were first noticed and described. While there is a great faunal 

 and stratigraphic continuity between these two temporary 

 divisions, nearly every species of the essentially deep sea fauna 

 has a horizon of greatest culmination which will serve as land 

 marks to the perfect section of the future. There are also 

 certain specific differences between the faunas of the two divis- 

 ions that mark them well, each having; many characteristic 

 forms of its own. 



The Washita Division. 



The upper half or Washita division is preserved only in a 

 limited belt, seldom exceeding twenty miles in width, adjacent 

 and parallel to the western border of the Black Prairie region. 

 Its strata are the same as mentioned but not defined by Eoemer 

 from the Waco camp,* ten miles west of New Braunfels, by 

 Dr. B. F. Shumard at old Fort Washita, Indian Territory, 

 from which it takes its name,f and as has been more fully 

 described by Jules Marcou from Comet creek, in the same 

 vicinity. I have traced the formation from the vicinity of Fort 

 Washita to San Antonio, and have good authority for its 

 occurrence westward of the latter place to the Rio Grande, 

 beyond Eagle Pass. The strata are of great uniformity of 

 deposition, throughout, except that they are thinner in the 

 northern portion of the exposures, where, from Fort Worth to 

 Fort Washita, and especially at Denison, they make a gradual 

 transition from deep-sea limestones to alternating limestones 

 and shales, and then from shales to the littoral sand and clay 

 deposits of the Lower Cross Timbers (Dakota Sandstone ?), 

 representing the termination of the long period of deep-sea 

 sediments that marked the Comanche series. The follow- 

 ing fossils have been found in this Washita division of the 

 Comanche series, as far as I have been able to verify by care- 

 ful field investigation : 



Fauna of the Upper, or Washita Division. 



Astrocoe.nia guadalupce Roem. 

 Terebratula toacoensis Roem. 



T choctaioensis Shum. 



T. leonensis Con. 

 Holaster simplex Shum. 

 Holaster eomanchesi Marcou. 

 Toxaster elegans Shum. 

 Cidaris hemigranosus Shum. 



Pyrinia Parryi Hall. 

 Ophioder'ma ? sp. no v. 

 Ostrea carinata Lam., Roem. 

 Exogyra arietina Roem. 

 Plicatula incongrua Con. 

 Ostrea crenidimargo Roem. 



0. quadriplicata Shum. 

 0. diluviana Linn., White. 



* " Texas," pp. 317 ; Kreidebildungen von Texas, p. 18. 



f Dr. B.'F. Slmmard partially described this division, but misinterpreted its 

 stratigraphic position in his section. 



