The surface structure of Cement is more or less a symmetrical fold with 2 well-defined domes. Since the early development which followed the drilling of the discovery well in 1916, exploration has been guided mainly by subsurface geological work. The discovery well, located on the crest of the anticline, was a producer from the Garber sandstone of Permian age. Most of the nomenclature of the Cement field took partial form in 1939 and 1940 when production was developed in the Rowe and Marchand sandstones. Though the correlations and identifications of the lithologic units involved have been generally known and accepted, it is obvious that the nomenclature now being used should be standardized. The boundaries of the Cisco, Missouri, Des Moines, and the Atoka are herein established on the basis of fusulinid determinations. The old field, about 16 mi. in length, is a structural accumulation of a NW.-SE.-trending anticlinal axis. An interesting structural feature of the field is the well-defined fault on the N. flank. Structurally high and low fault blocks are fundamental features of the axis.