For over 85 years, the stratigraphic determination of the Tabir Formation of Sumatra has been confused by a single fossil identification. Professor Fritz Frech recognized a specimen collected at the Batoe Kidjing locality by August Tobler to be an indeterminate, diminutive, ribbed oyster. Subsequently, this formation has been considered Upper Jurassic, perhaps Kimmeridgian, by several authors on the basis of this scant and inconclusive evidence; indeed, at least one author referred this sample to the genus Ostrea. However, these specimens are neither ribbed nor can they be demonstrated to be oysters; rather, this rock fragment contains a number of indeterminate mouldic fragments of fossils, too poorly preserved for confident identification. Modern determinations of the Tabir Formation as of Late Permian age are not contested by the evidence of this specimen. Copyright © 2008 John Wiley & Sons, Ltd.