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Inasmuch as the nomenclature in general use is largely of the writer's invention, he deems it proper to insert at this place a brief history of its origin and evolution, and to suggest certain necessary improvements.

Until the year 1886 little was known of the stratigraphy of the Cretaceous formations of Texas. Since 1819, beginning with the travels of Thomas Nuttall, fragmentary and disconnected observations had been made on the Cretaceous rocks and miscellaneous collections of fossils made, but no intelligible section of the rocks as a whole had been presented. The sequence of the formations was misunderstood and, in accordance with the classification of B. F. Shumard, then accepted, the lower beds were erroneously considered to be the upper. It was generally believed that the whole group represented a synchronous and deeper-water facies of the Upper Cretaceous or Meek and Hayden section as developed in northwestern United States, the base of which was the Dakota (Woodbine) formation, and that the Lower Cretaceous was unrepresented.

In 1886 the writer presented a section of the Cretaceous beds of Texas along the line of the Texas and Pacific Rail way from Millsap to Terrell, through Weatherford, Fort Worth, and Dallas. This section brought out the fact that the Texas Cretaceous included not only the equivalents of the Meek and Hayden section but also another series of Cretaceous rocks of older age and equal import. At that time the writer commented upon the fact that the composition and arrangement of these beds presented peculiarly favorable conditions for furnishing artesian water to a large area of the Black and Grand prairies, and their adaptability to this end was constantly borne in mind and suggested as his studies progressed. It was then stated that it would be a labor of years to trace out the full extent and variation of the numerous Cretaceous strata of the section, in order that a final classification could be made. Since that time the writer has continued his investigations, studying the stratigraphic and paleontologic sequence along lines of typical cross sections from Arkansas to the Rio Grande and mapping the areal extent of the formations, but he has not been able to carry on the work continuously. Furthermore, large parts of the region are not yet topographically surveyed.

Thus it will be seen that the classification of the Cretaceous formations of Texas has been a subject of evolution. From time to time preliminary papers have been presented, but with no pretense to finality. The writer can not here detail the labors which he has devoted to the amplification of the early section and to tracing the variations of the Comanche series throughout the vast areas in which "

Trans. Acad. Sci., St. Louis, Vol. I, pp. 582-589, 1856-1860.

Am. Jour. Sci., 3d series, Vol. XXXI, April, 1886.