SUMMARY.Schellackia occidentalisn. sp., is described from the following lizards from southern California:Sceloporus occidentalis becki, S. o. biseriatus, andUta stansburiana hesperis.Evidence is presented to show that lizards become infected by ingestion of the lizard miteGeckobiella texana.The mite acts as a passive vector by swallowing infected erythrocytes. After ingestion of the mites carrying parasitized red cells, the lizard is infected by migration of the sporozoites into the lizard's intestinal epithelial cells. Schizogony and sporogony occur in the intestinal wall of the lizard. Sporozoites appear in the peripheral blood from 30 to 45 days after ingestion of infected mites. This is the first species of the genusSchellackiato be described in the Western Hemisphere.