The Mississippian Caney shale of the northern Arbuckle Mountains is differentiated into three new members, the Ahlosa, the Delaware Creek, and the Sand Branch, in ascending order. The change of the goniatite faunas from the Sand Branch down to the Delaware Creek is so complete as to suggest major time hiatus, being comparable to that between the goniatites of the lower Namurian and the upper Visean of Britain and western Europe. In the southern Arbuckle Mountains similar change is observed between the goniatites of the soft shale of the lower Goddard formation above, and those of the hard, siliceous "Caney" shale below.

It is proposed to adjust the customarily accepted boundary between the Mississippian and Pennsylvanian in the northern and southern Arbuckle Mountains to the new faunal (chiefly goniatites and conodonts) and stratigraphic evidence, as follows. In the northern area the soft, non-bituminous, dark gray to gray shale with the ferruginous concretions remains wholly in the Pennsylvanian. However, in the southern Arbuckle Mountains most if not all of the soft Goddard shale with its abundant ferruginous concretions may be correlated by fossils with the upper part of the Caney shale of the northern Arbuckle Mountains (Sand Branch member). The Sand Branch is lithologically unlike the Goddard of the southern Arbuckles, being dark gray to black, and containing no ferruginous concretions; the lowe Goddard of this area, however, contains two small lentils of siliceous shale similar to that of the Caney.

New genus Edmooroceras is introduced for the American and European species of Eumorphoceras distinguished by a sharp and nodose umbilical edge. Edmooroceras is restricted to the basal part of the Eumorphoceras zone, and in the Barnett formation of Texas it mingles with Goniatites and Girtyoceras in an apparently very late Visean assemblage.

The lowermost series of the Pennsylvanian, the Springer, is believed to start with the Rod Club sandstone. The newly named, richly fossiliferous Redoak Hollow sandstone is placed about 600 feet above the base of the Goddard shale and between two recently discovered Eumorphoceras horizons. The subsurface Goodwin sandstone may be the equivalent of the Redoak Hollow. The Primrose sandstone originally included in the Springer by Tomlinson, is added to the overlying Morrow series, and so correlated on the evidence of the goniatites, with the Union Valley formation of the northern Arbuckles, and the Hale formation of northwestern Arkansas. However, the basal part of the Primrose seems to be of pre-Hale age.

A new name, Rhoda Creek, is applied to a somewhat sandy, fossiliferous unit below the Union Valley formation in the northern Arbuckle Mountains, and separated from it by a shale interval 100-300 feet thick.

A local lentil of conodont-bearing siliceous shale occurs in the basal part of the Goddard shale, and two lentils of conodont-bearing shale occur in the Sand Branch formation. The conodonts from all these lentils are described, and their illustrations assembled together with the previously known conodonts from the Barnett formation (by Roundy and by Hass), the Delaware Creek formation (Caney conodonts by Branson and Mehl), and the Johns Valley and the Wapanucka formations (by Harlton). All conodonts are illustrated to a uniform scale, and arranged in stratigraphic order.

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