Canton is in Ordinaries.

Canton. A small rectangle in the top left corner.

Hotham Arms. Barry of ten argent and azure, on a canton or a Cornish chough proper. Source.

Bassett Drayton Arms. Paly of six, or and gules, a canton ermine. Source.

Fox Arms. Ermine, on a chevron azure three fox's heads and necks erased or on a canton of the second a fleur de lys of the third. The canton is an augmentation of honour to his paternal arms, granted out of the Royal Arms as a mark of esteem to him and his heirs forever, by King Charles II following the Restoration of the Monarchy. Source.

Woodville Arms. Argent, a fess and a canton conjoined gules. Source.

Wrottesley Arms. Or, three piles sable, a canton ermine. Source.

Spencer Churchill Arms. Quartered 1&4 Churchill Arms a canton of St George, 2&3 Despencer Arms a bend sable three escallops, overall an escutcheon St George overall an escutcheon Capet Arms.