Original published in D.F. Merriam, ed., 1964, Symposium on cyclic sedimentation: Kansas Geological Survey, Bulletin 169, pp. 541-563

Figure 9--Concretions from Limopsis-Gervillia Assemblage Zone. A, Weathered core of a Limopsis concretion. B, Fresh fragment of a Limopsis concretion. C, Part of a Gervillia concretion oriented as found in place.