MEMBERS OF THE DENISON SECTION. 325 



White.* These beds have many areas of outcrop in northern Grayson 

 county, especially near old Preston and in southern Indian Territory.f 



In their stratification and alternations of clay and stone they resemble 

 the Walnut clays underlying the upper lime beds of the Comanche peak 

 or Fredericksburg division, thus indicating similar conditions of deposi- 

 tion. In the upper part of the cla}^ the layers become more calcareous 

 (marly) as they pass by insensible transition into the Duck Creek beds. 



The Kiamitia beds X mark a well defined shallowing and beginning 

 of the oscillatory upward movement Avhich characterizes the Washita 

 division. Paleontologically these beds, with the overlying Duck Creek 

 chalks, constitute a single fauna, as they have many species in common. 

 The following forms, however, have been noted in the Kiamitia : 



Epiaster whitei, Clark. Cyprimera (?) sp. (not C. crassa, Meek). 



Rolaster comanchesi, Marcou. Protocardia sp. 



Gnjphxa forniculata, White {G. pitcheri Ammonites penaianus, xon Biich. 



and G. roemeri of Marcou). ^4. vespertinus, Morton. 

 Avicula leveretti, Cragin. 



Duck Creek Chalk. § — The Kiamitia alternations increase in marliness, 

 and their limestones become chalkier without break until they culminate 

 in a bed of massive, chalky .limestone about 50 feet thick, which in turn 

 grades upward into marly clay. 



The importance of these beds in the Cretaceous system has been en- 

 tirely overlooked, but they are of unusual historic interest, for they con- 

 tain a unique fauna, which has been partially described and illustrated 

 by Professor Jules Marcou. || This writer was the first to correctly refer 

 any of the beds of the Texas Cretaceous to the Lower Cretaceous. Al- 

 though the great series of rocks to which they belonged was not at that 

 time appreciated. Professor Marcou clearly distinguished the Lower Cre- 

 Cretaceous age of the fossils, referring what are now known to be the 

 Caprotlna te.mna beds to the Neocomian and what are now defined as the 

 Preston beds to the Gault (greensand and marly chalk), and deserves 

 credit for having alone of all the earlier writers on the subject perceived 

 and announced the existence of the Lower Cretaceous rocks of the In- 

 dian Territory-Texas region, and I wish to express clearly, as I have 



•This is the form called G. pitcheri, var.fornicidnta, in my previous writings. It is the Gryphcsa 

 intchcri of Murcou, Geol. North America, p. 38, pi. iv, figs. 5, (J, and also called Gryphcea pitcheri 

 throughout the Texas reports. 



tThe buildings of old fort Washita, India-i Territory, are constructed of this stone. 

 4 Mr Taff places these beds in the Fredericksburg or Comanche peak division. This is merely 

 a question of opinion. 



? In their writings Taff and Cragin include these beds and their fossils in the Fort Worth lime- 

 stones. 



Ij Geology of North America, Zurich, 1858, pp. 20, 27. 



