_Parus montanus_ Gambel (1843, p. 259); and of authors, part. This name preoccupied (see Ridgway, 1904, p. 409). _Parus gambeli_ Ridgway _in_ American Ornithologists' Union Committee (1886, p. 335); and of authors, part. Substitute name. _Parus gambeli thayeri_ Birtwell (1901, p. 166). Based on adventitiously colored specimen from Albuquerque, New Mexico. Type in United States National Museum. _Penthestes gambeli_, of authors, part. _Type locality._--Santa Fé, New Mexico. _Diagnosis._--Among the four subspecies of _Penthestes gambeli_ here recognized, color alone is sufficient for distinguishing _P. gambeli gambeli_. The flanks, sides of body and back in this form are pervaded with a distinct tinge of cinnamon--more exactly, the "pinkish buff" of Ridgway (1912, pl. 29). In addition, this race shows the greatest length of tail, and slenderest bill. _Measurements._--Average of 14 males: Wing, 70.5 mm.; tail, 70.2; exposed culmen, 8.6; depth of bill at base, 3.8. For extremes, see accompanying table. _Note._--In this paper the length of wing is the usual chord of the folded wing as dried at the side of the body in the conventional study skin. The tail length, however, is measured from the _base_ of the uropygium to the tip of the longest pair of rectrices. It is found that in preparing specimens there is a practically uniform place for cutting off from the body the uropygium with attached feathers, and this is exactly where the tail bends back at an angle to the body in the fresh bird. The lateral rectrices are rooted evenly with the base of the dried uropygium so that the measurement of tail length thus taken becomes the distance from the extreme proximal ends of the most lateral pair of rectrices to the tips of the central pair--somewhat greater than the length of tail as given by Ridgway (1901, p. xv), the latter being the measurement from the base of the central pair of tail feathers to the tips of same. My reason for adopting this different procedure here is that more accuracy seems possible thereby, at least in the kind of material here dealt with. There is less mussing of the specimen also. Neither depth of bill nor culmen is a practical index to degree of slenderness of bill. No ordinary method of measurement will suffice to indicate the facts as they are perceived by the eye. As will be seen by the dates in the tables, as a rule only unworn specimens have been selected for measurement. _Range._--The Rocky Mountain region of North. America, from eastern British Columbia and western Alberta south to western Texas, New Mexico and Arizona. _Specimens examined_, 72, from the following localities: Alberta: Smoky Valley, 50 miles north of Jasper House, 1; Henry House, 1; 15 miles west of Henry House, 1. British Columbia: South fork of Moose River, 1. Montana: Gallatin County: Jefferson River, 1; Madison River, 2; Hillsdale, 2; Mystic Lake, 1; Dry Creek, 1.