516 R. T. HILL — THE COMANCPIE SERIES. 



crossing of Blue river; and five miles north of Marietta, in Indian territory. 

 There are intervening areas forming the surmounting plane of the Good- 

 land limestone escarpment, constituting, with the Duck Creek and Fort 

 Worth limestones, the only black prairies of Indian territory, including 

 the historic plains of the Kiamitia, near Fort Towson, from which Dr. G. 

 Pitcher, in 1830, collected and sent to Dr. Morton, of Philadelphia, the first 

 fossils ever procured from the American lower Cretaceous (Comanche series). 

 The same beds occur south of Red river, in northern Grayson county, at Dr. 

 Marshall's house, two miles south of old Preston, and in other places, and 

 also northwest of Gainesville, presenting the same topographic dip planes. 

 West of Gainesville and southward to Fort Worth they also occur, but in 

 less conspicuous areas. They outcrop ten miles west of Forth Worth, near 

 Benbrook station, and also in Williamson county, where, being thicker and 

 more calcareous, they form the black lands around Bagdad. This horizon 

 dips beneath the surface in the beds of Duck creek three miles north of 

 Denison, where, with the characteristic ammonite {jSchloenbachia peruviamts, 

 von Buch), it is seen in the bluffs of the creek. 



These clays are the basal beds of the Washita division, and represent a 

 shallower deposition than the chalky Caprina beds. 



The Duck Creek Chalk. — The Kiamitia clays are surmounted in Indian 

 territory and in Grayson and Cooke counties," Texas, by another chalky ter- 

 rane, which, from its occurrence on the southern slope of Duck creek north 

 of Denison, I have named the Duck Creek beds. This terraue is about 100 

 feet in thickness, and is composed of a crumbling, white chalky limestone 

 and alternating chalky marls, accompanied by a unique fauna, especially 

 characterized by the fossils Hamites fremonti, Marcou ; Ammonites, sp. nov.; 

 Inoceramus (Aucellaf), sp. nov.; all of which are found only in these beds. 



The Duck Creek beds are principally developed in northwestern Grayson 

 county and northwestern Cooke county, in Texas, and along the southern 

 border of the Kiamitia clays, in Indian territory. They have not been dif- 

 ferentiated south of Cooke county, although I have seen them west of Fort 

 Worth, near the cement works. The fauna of this terrane is so entirely dif- 

 ferent from those above and below that I am sometimes inclined to believe 

 this member should be considered a distinct division. 



The Fort Worth Limestone^ — The Duck Creek chalk beds underlie a 

 series of firmer and less pure yellow limestones and marls in alternating 

 strata of from one to two feet, and of great persistency. These limestones 

 are less chalky and of creamy tints, owing to the slight amount of oxidized 

 ])yrites they contain, and they also contain a little arenaceous matter. 

 After a little familiarity with them and their unique fossils, they will always 

 be readily distinguished from the other terranes. They are seen in the Den- 



* Washita Limestone, old classification of Hill. 



