In explanation of certain of these categories it should be said that in the synonymy no attempt is made to list every published reference to the subspecies concerned. It is aimed, however, to include at least one citation to each name-combination that has been applied, to the subspecies concerned, along with other especially important references. Mere records of occurrence are not regarded as especially important and citations to them ordinarily are omitted in the synonymy. No comma is placed between the zoÖlogical name and the name of the author who coined and first used the name in accordance with the rules of zoÖlogical nomenclature. Otherwise a comma is interposed between the zoÖlogical name and the name of the user (author). When the accepted (earliest available) name of a subspecies at the head of any one of the following accounts is combined with a generic name different from that with which it originally was placed, the authority for the name is set in parentheses. The same rule is followed with the name of a full species when it is written without any subspecific name following. Parentheses in such situations, therefore, denote that for the terminal part of the scientific name there has been a change in generic name with which the terminal part of the scientific name is here associated.

In the paragraph headed "characters for ready recognition," only a few characters, namely, those regarded as most useful for identification when the student has limited time, are mentioned. Other features useful for distinguishing the kind of animal in question from its near relatives are to be found in the description and comparisons.

In the description, external measurements, unless otherwise indicated, are those recorded by the collector on the label attached to the skin. Total length is the distance from the tip of the pad on the nose to the tip of the fleshy part of the tail when the relaxed animal is laid out straight, not stretched. This measurement does not include the hairs that project beyond the end of the fleshy part of the tail. Length of tail is the distance from the base of the tail, when it is bent at right angles to the long axis of the body, to the tip of the fleshy part of the tail excluding the hairs that project beyond the fleshy part of the tail. Length of tail and length of tail-vertebrae are synonymous. Length of hind foot is measured from the proximal end of the calcaneum to the tip of the longest claw.

Capitalized color terms, unless otherwise indicated, refer to Ridgway's (1912) Color Standards and Color Nomenclature. Some use is made of color terms taken from OberthÜr and Dauthenay (1905) because those authors show a much larger number of shades between dark brown and black than does Ridgway (1912). The colors of the upper parts of most weasels are some shade or other of dark brown. Color terms that do not have the initial letter capitalized do not refer to any one standard and consequently are used in a general sense.

Relative extents of the color of the upper parts and underparts are computed from measurements of the circumference of the body at the place where the color of the underparts is narrowest. Ordinarily this place is in the lumbar region rather than in the thoracic region.

An explanation of how cranial measurements were taken is given on page 417. In designating teeth, capital letters are used for teeth in the upper jaw and lower case letters are used for teeth in the lower jaw. For example: I2 denotes the second incisor tooth in the upper jaw and i2 denotes the second incisor tooth in the lower jaw; C1 and c1 refer to the canine tooth of the upper jaw and lower jaw, respectively; P3 and p3 refer to the third premolar of the upper jaw and lower jaw, respectively, bearing in mind that the first (anterior) premolar is absent in the lower jaw and upper jaw of weasels (see fig. 31 on page 416), as also, in some kinds of weasels, is the second premolar; M1 and m1 refer to the first molar of the upper jaw and lower jaw respectively.