Existence of Majorana fermions for M-branes wrapped in space and time

We show that it is possible to define Majorana (s)pinor fields on M-braneswhich have been identified under the action of the antipodal map on the adSfactor of the throat geometry, or which have been wrapped on two-cycles ofarbitrary genus. This is an important consistency check, since it means thatone may still take the generators of supertranslations in superspace totransform as Majorana fermions under the adjoint action of $Spin(10,1)$, eventhough the antipodally identified M2-brane is {\it not} space-orientable. Wepoint out that similar conclusions hold for any p-branes which have the generic(adS)$~{\times}~$(Sphere) throat geometry.Comment: 10 pages REVTe