Eimeria marsica Restani 1971 is re-described from oocysts recovered in pure culture from experimentally infected coccidia-free lambs. The ellipsoidal oocysts, which measure 19-1 x 13-1 mum, possess an inconspicuous micropylar cap. The prepatent period varies from 14-16 days. E. marsica is recorded for the first time from sheep in England.