Some articles on khmas:

Ait Ouriaghel - Khmas System
... The Ait Waryaghar are with the Ikeräiyen the only Riffian tribes that make use of the Khmas system ... A khams (singular for Khmas) is a sort of independent tribe inside a tribe, with their own qaid (tribe-leader) ... These are the five Khmas of the Ait Waryaghar Khams of the Ait Youssouf W'Äri / Ait Äri Khams of the Ait Bouäyach Khams of the Imrabdhen Khams of the Ait Abdellah ...