"West of Armidale occur a number of dykes which intrude Woolomin group greywackes and which are genetically associated with Permian granite. The rocks are similar to bostonites and quartz-bostonites and show remarkably developed flow structures which indicate the condition of the magma at the time of intrusion. It is shown that intrusion probably took place by laminar flow despite the occurrence of a pseudo-turbulent structure in one dyke and it is suggested that evidence of turbulent flow is unlikely to be preserved in intrusions even if such flow did occur."