William Berryman Scott,
A history of land mammals in the Western Hemisphere
(1913)
“ In order to identify a species, the genus to which it belongs must be stated, hence the term, binomial system of nomenclature, which Linnæus introduced, becoming trinomial when the name of a subspecies is added, a modern refinement on the older method. A very large species (i.e. one which is represented by great numbers of individuals) , extending over a very large area, is often divisible into groups of minor rank, as varieties, geographical races or subspecies. Taking the species as the unit in the scheme of classification, the varieties and subspecies may be considered as fractions. ”
