SivatheriumSiv`a*the"ri*um\, n. [NL., from E. Siva + Gr. ???? a beast, an animal.] (Paleon.) A genus of very large extinct ruminants found in the Tertiary formation of India. The snout was prolonged in the form of a proboscis. The male had four horns, the posterior pair being large and branched. It was allied to the antelopes, but very much larger than any exsisting species.