140 CRETACEOUS ROCKS OF TEXAS. 



the material for a commercial lime of unexcelled purity, which is now- 

 shipped as far east as New Orleans, and west to San Francisco. 



Mineralogical Features. — The Cretaceous formations east of the Pecos 

 are not a profitable field for the search for metallic minerals, owing to their 

 slightly disturbed condition. There are many beautiful and rare forms of 

 the non-metallic minerals of the lime group, but none of great value. 



Gold has been found in small and unprofitable quantities in the chalky re- 

 gions of Williamson County, as recorded by SchaefTer, but there is hardly a 

 possibility that it will ever prove of commercial value. Its mode of occurrence 

 and distribution, however, will be exhaustively examined into, so as to settle the 

 question beyond cavil. Occasional nodular lumps of limonite iron ore, often 

 of deceptive size, are found in the Caprina limestone, but in no case have I seen 

 a locality where a cart load could possibly be gathered. Calcite, aragonite, ce- 

 lestite, gypsum, anhydrite, occur in great abundance in places, as well as flint, 

 chalcedony, agate, opal, etc., all of which are upon the list for further study. 

 A large amount of information concerning the general occurrence and distri- 

 bution of these has been collected, preliminary to their final study. 



Plant and Animal Life of the Cretaceous Region. — Any one who 

 attempts to observe the character and distribution of life in the Cretaceous 

 region of Texas will soon be impressed with the fact that it possesses floral 

 and faunal conditions peculiarly its own, which no existing classifications 

 or text books sufficiently explain; and he will find that these conditions 

 also vary with the subdivisions, and that there is a most intimate relation 

 between the substructure and the life which inhabits it, especially exhibited 

 in the plants. Thus it is that the Exogyra Ponderosa marls are singularly 

 void of forest growth; that the evergreen oaks are fond of the White Rock 

 and Shoal Creek limestone; that the juniper loves the Caprina limestone; 

 while the unique and beautiful Sophora (Mount Bonnell laurel) flourishes 

 only in the magnesian beds of the Lower Fredericksburg division. The 

 post oaks and black jacks tenaciously inhabit the sandy formations, such as 

 the Upper and Lower Cross Timbers, and the Quaternary debris of the river 

 terraces. This natural plant growth will prove the surest guide to the most 

 appropriate agriculture to which the region is adapted. Lists of many of the 

 plants have been kept, which, together with the observations of previous 

 observers, and more careful investigations to be undertaken during [he com- 

 ing season, will prove of great value. 



It is popularly supposed that observations upon the animal life in general 



are of less economic importance, and are of interest and value only for 



educational purposes. The insects, mammals, and birds may be destructive or 



protective to vegetation. They are therefore of great economic interest. 



In concluding this paper, the writer can not omit the opportunity to urge 



