Motley and stripe are co-dominant, to an extent. It appears as though motley is slightly(or partially) dominant to the stripe gene, but they exist on the same allele. "motley het. stripe" is one term used to describe it. "Het. Motley and stripe" would be just as sufficient, because with both recessive genes, it is impossible to have a homozygous state.
The snake will show a phenotype that can range anywhere from perfect motley to fully striped...and any combination therein.
Some babies will be motley(two motely alleles), some will be stripe(two stripe alleles), some will be motley het. stripe(one motley allele, one stripe allele), but all three combinations will show a motley pattern to some degree...
Of course, if both snakes are motley het. stripe, all the babies will show motley, stripe, or motley het. stripe as the phenotype. In other words...a snake cannot be "het. motley + stripe" and still have a "normal" pattern. There are only two loci at the allele.