Among the rubble that was the eroding rock of the Viola formation I found a few good examples of the brachiopod Oxoplecia gouldi. The shell is subrectangular to suboval in outline with both valves roughly equal in size and depth. There is a wide, shallow fold and sulcus structure present along with fine, widely spaced radiating striae on the surface of the valves. The pedicle valve extends out and curves back over the brachial valve. There is a wide, triangular interarea on the pedicle valve that is almost as long as the hinge line.
These specimens comes from the Viola formation which is upper Ordovician (Sandbian to Katian stage) in age and overlies (unconformably?) the Bromide formation. I found them in a road cut along US 177, south of Sulphur, Oklahoma.