A PSEUDOCONFIGURATION OF POINTS WITHOUT ADJOINT

We give an example of a simple oriented matroid D that admits an orien ted adjoint. Furthermore, any adjoint of the underlying matroid D, doe s not itself admit an adjoint. D arises from the well-known non-Desarg ues matroid by a coextension by a coparallel element and, hence, has r ank 4. The orientability of D and some of its adjoints follows from an apparently new oriented matroid construction given in the paper that is a very special case of an amalgam of two copies of one oriented mat roid. (C) 1996 Academic Press, Inc.