IN examining a series of more than one hundred specimens of Ostrea (Exogyra) flabellata, Goldfuss, from the Middle Cretaceous of Lebanon, I was struck with the marked reproduction in the free upper valves of the figures of other shells to which the lower valves have been attached. These specimens were all collected in the same place, a hill near Bhamdun, Mount Lebanon, Syria. They have been freed by weathering from a soft marly rock exceedingly rich in fossils. Specimens of Ostrea, Plicatula, Pecten and Anomia have the shell well preserved. Many others, including species of Cardium, Trigonia, Corbula, Isocardia, Cytherea, Leda, Nucula, Cerithium, Alaria, Melo, Pterocera, Turritella, Natica and others are preserved only as casts. Consequently the shell to which the oyster was attached has usually disappeared, except in those cases in which it was attached to one of its own species. More than half of the specimens have the two valves united and free from adhesions, so that they are capable of exhibiting the phenomenon referred to. More than nine-tenths of these show more or less clearly in the upper valve the figure impressed upon the lower valve by the shell to which the latter adhered.