126 CRETACEOUS ROCKS OF TEXAS. 



Caprina limestone is no doubt the continuation and culmination of the great 

 subsidence of the ocean's bottom in Lower Cretaceous time, and will be of 

 service in future interpretation and final correlation. It is very uniform, and 

 covers large areas of the Grand Prairie plateau in southwest Texas, especially 

 in the region adjacent to the lower Pecos. It also caps the mesas of the 

 remnantal areas in the Abilene country, and as far east as Comanche Peak in 

 Hood County. The railroad from Brueggerhoff to McNeil along the Wil- 

 liamson-Travis County line crosses a typical portion of its strike. 



Economics of the Capeina Limestone. — The Caprina limestone is also 

 productive of many rare building stones and other structural material, while 

 the immense flint deposits will no doubt be ultimately utilized.* 



The Caprina limestone is the material used in the manufacture of the Aus- 

 tin lime, which has a wide celebrity for its purity. This stone also makes a 

 good material for macadamizing roads, and is now being extensively used 

 for that purpose by the city of Waco. 



The residue of the Caprina limestone and certain marly beds at the topj- 

 make the richest and most productive agricultural soil of the Grand Prairie 

 region. It is readily distinguished by its dark red, sometimes nearly black, 

 color, as seen in the country between Florence, Williamson County, and 

 Leander, and in the Jollyville neighborhood of Travis County. It also 

 occurs in Bell, Coryell, Hamilton, Bosque, and Hood Counties. This soil has 

 not yet been mapped or classified. 



No. 3. THE WASHITA DIVISION. 



The Caprina chalky limestones which mark the culmination of subsidence 

 in the Comanche series are succeeded by deposits of a lithologic and strati- 

 graphic character which indicate that the ocean's bottom had reached the 

 culmination of the long subsidence which it had been undergoing since the 

 beginning of the Trinity beds, and had commenced the gradual elevation 

 which finally terminated in the Mid-Cretaceous land. This shallowing is well 

 illustrated in the thin stratification of the rocks above the Caprina limestone, to 

 which the name Washita Division has been given, after the region where its 

 rocks were first seen by early explorers near Port Washita, I. T. 



*The Caprina limestone was given its name by Dr. B. E. Shumard from the abundance of 

 the peculiar aberrant fossils of the genus Rudistes (which have been described as Bequienia, 

 Caprina, Monopleura, Ichthyosarcolithes, etc.) occurring in it. These peculiar forms are found 

 occasionally in great masses. Accompanying these beds are also many new and undescribed 

 species. 



fThese beds are characterized by the peculiar smooth-ribbed Ammonite Schloeribachia 

 peruviana, De Buch (A. acuto-carinatus, Rcemer). They have not been satisfactorily studied 

 in the Colorado section as yet. 



