The Crinerville oil field, near Brock, Carter County, Oklahoma, occurs on a surface anticline in Pennsylvanian strata on the west side of, and faulted against, the Criner Hills. The reverse dip of 15° on the northeast side of the anticline disappears under a large part of the anticline in shales within 900 feet of the surface. Production comes from Pennsylvanian oil sands which overlap a truncated portion of the original Criner Hills of Ordovician limestone, now buried at a depth of more than 1,000 feet. The oil originated in the Pennsylvanian shales, and a small quantity migrated laterally into the Ordovician. The field was opened in January, 1922, and has produced between 1,000 and 1,500 barrels a day ever since. The total production to June 30, 1927, was slightly m re than 2,300,000 barrels.

The writer is indebted to R. A. Birk and Miss Dollie Radler for assistance in preparing this paper, and to B. H. Harlton for paleontological determinations. C. W. Tomlinson, who has made a careful study of the Glenn formation, has kindly permitted the use of his determinations and areal map.