  We investigate an elliptic quantum group introduced by Felder and Varchenko,
which is constructed from the $R$-matrix of the Andrews-Baxter-Forrester model,
containing both spectral and dynamical parameter. We explicitly compute the
matrix elements of certain corepresentations and obtain orthogonality relations
for these elements. Using dynamical representations these orthogonality
relations give discrete bi-orthogonality relations for terminating
very-well-poised balanced elliptic hypergeometric series, previously obtained
by Frenkel and Turaev and by Spiridonov and Zhedanov in different contexts.
