Sphenothallus sp. Hall

3/31/2012: Thanks to the astute members of The Fossil Forum, the “mystery Pennsylvanian fossil, inside brachial valve of Pulchratia symmetrica” is identified, to within a reasonable certainty, as Sphenothallus sp. Hall. Cf. Van Iten, Heyo, Robert S. Cox & Royal H. Mapes (1992). “New data on the morphology of Sphenothallus Hall: Implications for its affinities.” Lethaia 25, 135-144, whose authors “favor[] the hypothesis of a cnidarian affinity for Sphenothallus.” Pennsylvanian, near Vinton, KS.