Boa constrictor sigma

Explorer Langhammer gave to the world in year 1983 to discussion one more controversial subspecies of Boa constrictor. Subspecies called Boa constrictor sigma should have its endemic range only on island Tres Marias 100km far from pacific coast of Mexico. To say something exact to this subspecies is quiet hard, because it exist only 9 exemplars somewhere in museums, but no picture is available.
But this situation does not prevent a few of breeders from offering to sell Hogg islands imperators as Boa constrictor sigma.