The Black Prince Limestone in southeastern Arizona has previously been assigned a Mississippian age. Paleontological evidence for this age has been scanty, with emphasis being placed on the occurrence of Lithostrotionella shimeri (Crickmay) in the basal 2 ft of the formation. Results of the recently completed field and laboratory investigation show that Lithostrotionella shimeri in the Black Prince Limestone occurs in a residual accumulation from erosion of the underlying Escabrosa Limestone (Mississippian). An assemblage of 5 coral genera found in the Black Prince Limestone correlates with Lower Pennsylvanian (Morrowan) fauna in the Marble Falls Limestone of central Texas. The occurrence of Millerella throughout the formation, as well as Atokan fusulinids at the base of the overlying Horquilla Limestone (Pennsylvanian), indicates a Morrowan age for the Black Prince Limestone.