The distribution and relationships of Lower Cambrian units in the Flinders Ranges are illustrated by a panel diagram and sketch maps. A new rock name, Hawker Group, is introduced for six formations of Lower Cambrian age which represent a phase of marine transgression following the deposition of the Pound Quartzite. An archaocyathid biostrome development associated with graben faulting above the Oraparinna Diapir is noted. The Billy Creek Formation is considered to lie disconformably on the Hawker Group in several areas and to represent a widespread phase of uppermost Lower Cambrian marine regression. A thin but persistent tuffaceous unit occurs in the lower half of this formation.