Lying between the Lower Plains and the black prairies is an irregularly bounded district comprising the Grand Prairies and the Lampasas Cut Plain. The region extends southward from the Red River in Cooke County to the Colorado River valley in Burnet County. The entire area is underlain by rocks of the Comanchean series, comprising extensive layers of hard limestone together with the characteristically interbedded marly clays. The Lampasas Cut Plain is an extension northward beyond the Colorado River of the same type of rocks that underlie the Edwards Plateau. The topographic pattern of the Lampasas Cut Plain, however, is entirely different. The type of dissection the Lampasas Cut Plain exhibits belongs more nearly with the Lower Plains, although dissection and reduction have not proceeded nearly as far as in that area. The Lampasas Cut Plain has a mesa-type topography with wide lowlands intervening between the mesa uplands. The flat-topped mesas are capped with hard limestones, the edges of which are margined by a typical rim-rock vegetation. The lowlands may have somewhat sloping surfaces, in which case they usually are erosional and underlain with shallow caliche, or they may be completely reduced to flatness, in which case they have a smooth constructional surface and thick soils of the Chernozem type. The Grand Prairies form an elongated area of grassland country which lies between the western and eastern sections of the Cross Timbers. The Grand Prairies are underlain by Lower Cretaceous (Comanchean) "hard" limestones with interbedded marly clays, in contrast with the "soft" rocks and calcareous clays underlying the black prairies. The landscape features of the Grand Prairies are similar to those of the black prairies, although the surface features of the former are sharper and more acute in outline than the typically smooth-featured, roundly rolling to undulating topography of the black prairies; and in the Grand Prairies the underlying limestone layers are much in evidence. The Grand Prairie country is cut across by streams with meandering channels which were acquired during a previous cycle of topographic development and are rather deeply incised below the regional level of the area. The strata at the surface dip perceptibly eastward. Outcrops of the hard limestone form distinctive erosional ridges with thin soils, which are mainly utilized for grazing purposes. These features are well expressed, for instance, in the Goodland Escarpment, an interior-facing escarpment which marks the western limit of the Grand Prairies. The original vegetation of the area was mostly tall grasses, but modern pastures have short grasses or bunch grasses together with typical herbage growths characteristic of the drier portions of the prairies. Farming enterprises in the Grand Prairies are mainly devoted to cotton growing, although a considerable amount of wheat is grown in the northern portion of the region.