_Zygomatic length._--From anteriormost point of zygomatic process of maxillary to posteriormost point of zygomatic process of squamosal. _d_ to _d´_ _Zygomatic breadth._--Greatest distance across zygomatic arches of cranium at right angles to long axis of skull. _j_ to _j´_ _Breadth of inferior ramus of zygomatic process of maxillary._--Greatest distance across inferior ramus of zygomatic process of maxillary taken parallel to long axis of skull. _d_ to _e_ _Palatal breadth at M3._--Greatest distance from inside margin of alveolus of right M3 to its opposite. _g_ to _g´_ _Palatal breadth at P4._--Same as above except taken at P4. _g_ to _g´_ _Mastoid breadth._--Greatest distance across mastoid bones perpendicular to long axis of skull. _h_ to _h´_ _Breadth of braincase._--Greatest distance across braincase taken perpendicular to long axis of skull. _i_ to _i´_ _Interorbital breadth._--Least distance across top of skull between orbits. _k_ to _k´_ _Length of maxillary tooth-row._--From anterior border of P4 to posterior border of M3. _l_ to _l´_ _Breadth of base zygomatic process of squamosal._--Greatest distance across base of zygomatic process of squamosal taken parallel to long axis of skull. _m_ to _m´_ [Illustration: FIGS. 1-3. Three views of the skull to show points between which measurements of the skull were taken. Based on _Z. t. montanus_, adult, female, No. 22165 KU, Cascade Divide, 6400 ft., Crater Lake Nat'l Park, Klamath County, Oregon. × 4.] The baculum has a characteristic size and shape according to the species, and the following significant measurements of the structure were taken: _Greatest length._--From posteriormost border of base to anteriormost point on tip. _Greatest breadth at base._--Greatest distance across base taken parallel to long axis of bone. _Greatest breadth at tip._--Greatest distance across tip taken parallel to long axis of bone. In the descriptions of color the capitalized color terms refer to those in Ridgway (1912). Any color term that does not have the initial letter capitalized does not refer to any one standard. In the description of the subspecies the two sexes are treated as one because no significant secondary sexual variation was found. Only fully adult specimens of age groups 3 to 5, as defined on pages 377 and 388, have been considered. Unless otherwise indicated, specimens are in the University of Kansas Museum of Natural History. Those in other collections are identified by the following abbreviations: