  Let SU_C(2) denote the moduli variety of rank 2 semistable vector bundles
with trivial determinant on an algebraic curve C. We prove that if C is
trigonal then there exists a projective moduli variety N_C containing SU_C(2)
as a subvariety and smooth of dimension 7g-14 away from SU_C(2). N_C
parametrises Galois Spin(8)-bundles on the Galois closure of C over P^1.
Moreover, if x in J_C[2] is a 2-torsion point let R(x) be the Recillas
tetragonal curve whose Jacobian is isomorphic to Prym(C,x). Then there is an
injection of SU_R(x)(2) into N_C giving a `nonabelian Schottky configuration'
in N_C singular along the classical Schottky configuration in SU_C(2).
