The Tyger of all other Beasts (except the Lion) is the most honourable, he being a Beast of incomparable Swiftness and Cruelty.

From The Grammar of Heraldry by Samuel Kent, p130


The heraldic tigre, the invention of the early heralds, is depcited as having the body similar to a wolf, but more strong and massive; powerful jaws armed with prominent canine tusks, and with a short curved horn or spike at the end of his nose. A row of knotted tufts of hair adorn the back of his neck as a mane; tufts also on his breast and thighs, and with strong claws; the tail of a lion completes his equipment.

From Fictitious and Symbolic Creatures in Art by John Vinycomb, p191

The tigre or tyger of the old heralds still holds it place in English armory, retaining the ancient name to distinguish it from the natural tiger, to which it bears but little resemblance except the name… The habit of drawing in a conventional manner may also have assisted in producing such a monster. This type of wild and ruthless ferocity, approaching the draconic in its power and destructiveness, was to their minds fitly suggested by exaggerations of those attributes of savageness and bloodthirstiness with which it was supposed to be endowed.

From Fictitious and Symbolic Creatures in Art by John Vinycomb, p190