The Clan Graham society has posted this information:
"The English branches of the de Tancarvilles were generally named Chamberlain. The banner of the Chamberlains of Lincoln bore three escallops, which also appear in the arms of de Graham or de Grantham, originally from Lincoln. (Sir John Graham of Dundaff carried a banner with three golden escallops on a field of black. The same three golden escallops are a part of the Montrose Coat of Arms.) From this family descended the famous Marquis of Montrose and the brave Viscount of Dundee; also Sir James Graham of Netherby, the eminent statesman."