Arnor's heraldic signs?

I'll double-post this with Decipher's board:

I've got a question for the Tolkien scholars out there.
What is Arnor's heraldic sign?

I've found the following in the Encyclopedia of Arda:
>The Guards of the Citadel bore the arms of Elendil himself - a white tree in blossom, surmounted by a silver crown and stars, all embroidered on a field of black.

I know the tree is for Gondor, the 7 stars represent the Palantiri, and the crown is probably the crown of the High-King of the Faitfull.

Dol Amroth has it's Swanship on blue, Rohan has a white horse on a green field. But what are the banners of Arnor, and it's daughter realms: Arthedain, Cardolan and Rhudaur? Does anyone know? Did Tolkien mention this at all?