By distinguishing between producible and nonproducible public goods, we are able to propose a general equilibrium model with externalities that distinguishes between and encompasses both the Starrett [1972] and Boyd and Conley [1997] type external effects. We show that while nonconvexities remain fundamental whenever the Starrett type external effects are present, these are not caused by the type discussed in Boyd and Conley. Secondly, we find that the notion of a “public competitive equilibrium” for public goods found in Foley [1967, 1970] allows a decentralized mechanism, based on both price and quantity signals, for economies with externalities, which is able to restore the equivalence between equilibrium and efficiency even in the presence of nonconvexities. This is in contrast to equilibrium notions based purely on price signals such as the Pigouvian taxes.