Halobacteriumvolcanii is the correct name if this species is regarded as a separate species within a separate genus Halobacterium.
On the Approved Lists of Bacterial Names, and on the Approved Lists of Bacterial Names (Amended Edition), this taxon is incorrectly cited as Halobacterium volcanii Mullakhanbhai and Larson (sic) 1975.Publication:
Larsen H. Genus I. Halobacterium Elazari-Volcani 1957, 207AL. In: Krieg NR, Holt JG (eds), Bergey's Manual of Systematic Bacteriology, first edition, vol. 1, The Williams & Wilkins Co, Baltimore, 1984, p. 262-266.