At the present time the American geologists, both those of the United States and the Dominion of Canada, are at variance as to the groups the Archæan should be divided into; it is however unnecessary to enter into this controversy, as the strata may be conveniently grouped, as in Selwyn's map (1884), into Norians or Labradorians, excessively coarse gneiss or other granitic rocks; Laurentians, gneisa and granite; and Huronians, schists with subordinate gneiss.