314 PROCEEDINGS OF THE ACADEMY OF [1893. 



that river of a great plateau broken by mountain ranges, southern 

 spurs of the Rocky mountains. The plain east of the Pecos is 

 broken in only one place, where the Paleozoic rocks are exposed 

 by the removal of the Cretaceous covering, and this has been called 

 by Professor Hill, the Central Denuded Area. 



On the Gulf coast are the Quaternary beds, forming the Coastal 

 Prairies, a great, level tract of land chiefly swampy and but 

 slightly elevated above the Gulf. A forested region of Tertiary 

 sands and clays, carved into gently undulating topography is 

 interposed between the Coastal Prairies and the great Cretaceous 

 plain. The Cretaceous plain, commencing at an elevation, in the 

 vicinity of Austin, of not far from four hundred feet, though vary- 

 ing in different parts, forms one of the greatest geographical units of 

 Texas. It is a treeless prairie, with a few exceptions, and occupies 

 nearly one fourth of the state, rising gradually away from the coast 

 and reaching an elevation of two thousand feet and more. 



Partly enclosed in this Prairie is the Central Denuded Area, a 

 region of hilly, sparsely forested Carboniferous and older rocks, 

 which to the west merge into the Red Beds of Permian age. These 

 beds on the east have something of the topographic diversity of the 

 older rocks, but to the west change gradually in topographic form 

 and merge, geographically, almost imperceptibly into the lake or 

 inland sea beds of the Staked Plains, the Llano Estacado. These 

 plains, treeless and arid, form a true plateau with an elevation of 

 from 3,000 to 4,500 feet. The Pecos river flows along the base of 

 the Llano Estacado plateau which ends abruptly in a steep west 

 facing escarpment. To the west there is another plateau, broken by 

 mountain ranges, the Trans-Pecos Mountain and Basin region of 

 Hill. 



There are, therefore, six great topographic divisions in Texas: — 

 1st, the Coastal Prairies ; 2nd, the Rolling Forested Tertiary Area ; 

 3rd, the Grand Prairie ; 4th, the Central Denuded Area ; 5th, the 

 Llano Estacado ; 6th, the Trans-Pecos Mountain and Basin Region. 

 To this might be added many minor divisions dependent upon minor 

 topographical or geographical features. East of the Pecos the coun- 

 try is one of plateaus, plains, and prairies, forested only in one of its 

 parts (with one or two exceptions to be hereafter noted). The Cen- 

 tral Denuded Area alone is hilly and in no place are there mount- 

 ains. Buttes, chiefly of Cretaceous strata, form the only striking 

 elevations and these are dignified by the name of mountains by the 



