The two series comprising the Cretaceous System occupy the areas of the State known as the Black Prairie, the Grand Prairie, and the two Cross Timbers, and unstudied areas in the eastern and trans-Pecos regions of the State.

To these strata the State owes a large part of her agricultural and general prosperity, for they are the foundation and source of the rich black waxy and other calcareous soils of the Black and Grand Prairie regions. In addition to their agricultural features, these formations are the most productive source of building material, while along the parting between them, extending the entire length of the State and dependent upon their stratigraphy, is a remarkable area of natural and artesian springs, as seen at Fort Worth, Austin, San Marcos, and elsewhere.

It is not the purpose of this paper, however, to enter into the economic discussion of these formations, but to give in brief language, for the benefit of the professional geologist, a resume of the scattered results which have been published from time to time concerning the strata under discussion, in order to aid in the field examination and to enable the geologist to ascertain exactly what is to be known and what is to be found out concerning them.

In beginning it should be distinctly understood that, notwithstanding the many scattered publications upon these formations, very little exact detail has been published concerning them, and that we are now just ready to begin their systematic study, and to publish results that will be of value both to the practical development of the country and to knowledge.

It is now known that the series of rocks which a few years ago were considered as the whole Cretaceous group of the United States east of the Rocky Mountains, or the section published by Meek and Hayden, rests in Texas unconformably upon another great series of rocks of even greater thickness, to which I have given, out of deference to the town of Comanche where I first studied them, the name of the Comanche series; hence, we now have in the United States two great series, the Lower or Comanche and the Upper or Meek and Hayden series. Each of these is entirely distinct from the "

The first announcement of this series was published by me in the American Journal of Science, January, 1887, p. 75. See Record of Science for 1886, Smithsonian Report, 1887-8, p. 220.