The spleen of the Australian lungfish (Neocerarodus forsteri, barrammunda) was investigated histologically. The chief findings are as follows. The spleen of the lungfish is embedded in the wall of the stomach and localized in the submucosal layer, like that of larval Lampetra. The central arteries are ensheathed by a mass of densely aggregated cells. The mass resembles the periarterial lymphoid sheath of mammalian spleens. However, it consists of two types of collections of lymphocytic and granulocytic series. It is, therefore, essentially a periarterial lymphomyeloid sheath