  Generalized Dirac equation with operator mass term is presented. Its
solutions are non standard (ELKO) spinors which are eigenvectors of the charge
conjugation and dual helicity operators.
  It is demonstrated that in spite of their non covariant nature ELKO can serve
as a carrier space of a representation of Poincar\'e group. However, the
corresponding boost generators are not manifestly covariant and generate
non-local momentum dependent transformations which are presented explicitly.
These results present a new look on group-theoretical grounds of ELKO theories.
