I found a few of these tiny, elongated brachiopods while searching the Bois d'Arc formation. I believe it is called Camarotoechia haraganensis. It's a small shell that is longer than it is wide. Both valves are equally convex with strong costellae (or ribs as I sometimes call them). The sides of each valve are fairly flat and nearly at a right angle to the rest of the valve. On the pedicle valve, the beak extends well past the brachial valve with little to no curving with the umbo at the very tip, perpendicular to the rest of the beak.
These are much larger specimens that those that I have from the Haragan formation and could represent a different species. The only other similar species, that I can find reference too, is Rhynchospirina maxwelli but that shell is wider and has finer costellae.
"Stratigraphy and Paleontology of the Hunton Group in the Arbuckle Mountain Region, Part V - Bois d'Arc Articulate Brachiopods " Amsden, 1958, Oklahoma Geological Survey Bulletin 82
"Stratigraphy and Paleontology of the Hunton Group in the Arbuckle Mountain Region, Part II - Haragan Articulate Brachiopods " Amsden, 1958, Oklahoma Geological Survey Bulletin 78