Symposium : 1. The geological history of the Protobranchia and the dual origin of taxodont Lamellibranchia / L.R. Cox -- 2. The status of the Protobranchia in the bivalve Mollusca / C.M. Yonge -- 3. The ligament and digestive system in the taxodont bivalves / G. Owen -- 4. Phylogenetic classification of the Lamellibranchia, with special reference to the Protobranchia / R.D. Purchon
