A new species and genus of marine mite, Corallihalacarus chilcottensis, is described from Australia. It occurs in sandy deposits around Chilcott Island, some three hundred kilometres off the northeastern Australian coast, and can be distinguished from other marine mite species by having a flexible neck between the idiosoma and the gnathosoma. Other unusual features of this species include a large median claw on each tarsus, rigid lamellae on legs III and IV, a very long apical palp segment and closely abutting, fused or overlapping idiosomal plates. The new genus is most closely related to Mictognathus Newell and the new subfamily Mictognathinae is established to accommodate both genera.