Barnacle goose Barnacle goose The barnacle goose ("Branta leucopsis") belongs to the genus "Branta" of black geese, which contains species with largely black plumage, distinguishing them from the grey "Anser" species. Despite its superficial similarity to the brant goose, genetic analysis has shown it is an eastern derivative of the cackling goose lineage. The barnacle goose was first classified taxonomically by Johann Matthäus Bechstein in 1803. "Branta" is a Latinised form of Old Norse "Brandgás", "burnt (black) goose" and the specific epithet is from the Ancient Greek "leukos" "white", and "opsis" "faced". The barnacle goose and the similar brant goose were previously
Genus of a quadratic form the same genus have equal discriminant and hence there are only finitely many equivalence classes in a genus. The Smith–Minkowski–Siegel mass formula gives the "weight" or "mass" of the quadratic forms in a genus, the count of equivalence classes weighted by the reciprocals of the orders of their automorphism groups. For binary quadratic forms there is a group structure on the set "C" equivalence classes of forms with given discriminant. The genera are defined by the "generic characters". The principal genus, the genus containing the principal form, is precisely the subgroup "C" and the genera are the cosets of "C":