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by a long, narrow strip of prairie country, seldom more than a mile in width, extending through McLennan, Bell, Williamson, and Travis counties, between the Balcones scarp and the western edge of the Black Prairie. The soil of this belt is different from that of the Gainesville Prairie, being black in color and of a sticky nature, instead of brown, and is underlain by the yellowish clay subsoil of the Del Rio (Exogyra arietina) formation. This black soil is an exceptional feature in the Grand Prairie and resembles more the prevalent character of the soil and joint clays of the Black Prairie. The surface of the Bosqueville Prairie can hardly be called a dip plain in the true sense of that word. It is marked by "hog wallow" depressions, and usually supports a dense growth of mesquite trees and mesquite grass, constituting a character of country known in Texas as "mesquite flats."

-Immediately west of the Gainesville Prairie, north of the Brazos, and the Bosqueville Prairie to the south, a belt of more extensive and open prairie sets in, underlain by white and yellowish bands of limestone and clay, which outcrop in roads and streamways and weather into grayish soils, giving to the landscape a lighter and more glaring tone than that of the prairies above described. These prairies are superb illustrations of typical dip plains, the gently sloping flat surfaces being established for miles at a stretch upon single beds of strata, making grass-covered uplands resembling the boundless views of the Great Plains proper.

This prairie region, which is best seen around Fort Worth, in the western half of Tarrant County, occupies most of the uplands north of the Brazos west of the Missouri, Kansas and Texas Railway and east of the Western Cross Timbers, including the greater part of western Cooke, Tarrant, and Denton counties, and the eastern portion of Wise County. It also occurs in limited spots in the northern part of Grayson, and nearly all the Indian Territory division of the Grand Prairie region belongs to it. The Fort Worth Prairie is more rolling along its interior margin, which extends to the western escarpment, and is there usually accompanied by a fringing belt of stiff clay lands, the outcrop of the Preston beds below the Fort Worth limestones. South of the Brazos the Fort Worth Prairie contracts in width and becomes a secondary feature in comparison to the belts of the Lampasas Plain next to be described. In this general region it is a narrowing belt-often a mere ribbon-passing through McLennan, Bell, and Williamson counties, where it is found only on the downthrown side of the Balcones fault zone.

As the more unbroken dip plains of the Gainesville and Fort Worth type which occupy nearly all the width of the Grand Prairie north of