While examining and sorting Ordovician graptolites of the Palaeontological Museum in Oslo, l noticed a peculiar and characteristic preservation of certain species. In cases where the graptolites occur in great quantities on the surface of the black shale-slabs of t he Ceratopyge Shale (3 a ß) and the Lower Didymograptus Shale (3 b) , the specimens are arranged in a peculiar way as described below. The position of the preserved graptolites suggests distinct conditions of the black m ud in which the specimens were embedded.
To the problem of black graptolite shales. Tracs of gas-bubbles penetrating the surface-layers on the bottom