Bipartite structure

[Randolph Graczyk]

Re the discussion on Siouan instrumentals:  In Crow and Hidatsa, there is no
inner/outer opposition--all the instrumentals are 'inner'.  As far as I can
tell, the same is true in Mandan and in Southeastern Siouan.  Biloxi appears
to have lost the instrumentals that would be outer in other languages, but
there is evidence from Tutelo in Oliverio's grammar that indicates that all
the instrumentals are inner.

Question: is it possible that the inner/outer opposition is an innovation in
Mississippi Valley languages?

Randy