ABSTRACT It has long been known that true denticles, as opposed to mere ridges, tubercles, or spines of the outer ganoine layer may occur on the exposed surface of the scales and dermal bones of living Actinopterygii such as Poly pt er us orLepidosteus. But, so far as I know, they have never been described on the scales or dermal bones of any fossil Actinopterygian.1 This is a remarkable fact, for we should certainly expect to find them at all events in the more primitive forms.