1926] GrinneU: A New Race of the Whit e-hr east ed Nuthatch 409 



put the matter in yet another way, the latter owes the marked degree 

 of its distinctness to a marked degree of isolation, just as is the case 

 with Jagunae. 



The closest resemblance of the race Sitta carolinensis alexandrae 

 is not with either of its two nearest neighboring relatives but with 

 a rather remotely located race, namely, 8. c. tenuissima Grinnell 

 (1918, p. 88). This subspecies occupies an irregular north-and-south 

 range along the western rim of the Great Basin, south through the 

 White and Panamint mountains in extreme east-central California. 

 The differences between tenuissima and alexandrae lie in the heavier, 

 less acicular, longer bill of the latter, in its greater breadth of 

 rectrices, and in the greater amounts of white on inner primar.y 

 tips and tail. The similarities between these two races (relatively 

 long wing, tail, and bill, and dark tone of grayness on back) are 

 evidently due to factors other than immediate genetic relationship. 



Fig. 1. Bills of six subspecies of the White-breasted Nuthatch (Siita caro- 

 linensis) ; all natural size. 



a, S. c. aculeata, (^ ad. ; uo. 30214, Mus. Vert. Zool. ; Jolon, Monterey County, 

 California; October 18, 1918. 



6, S. c. tenuissima, c^; no. 28716, Mus. Vert. Zool.; Panamint Mountains, Inyo 

 County, California; June 1, 1917. 



c, S. c. nelsoni, (^ ; no. 27781, Mus. Vert. Zool, ; Sierra Ancha, Gila County, 

 Arizona; June 24, 1917. 



d, S. c. lagunae, ^ ; no. 37514, coll. Louis B. Bishop; Laguna Valley, Cape 

 District, Lower California; August 21, 1924. 



e, S. c. alexandrae, (^ ad.; no. 46464, Mus. Vert. Zool.; San Pedro Martir 

 Mountains, Lower California; October 10, 1925. 



/, S. c. carolinensis, ($; no. 10858, Mus. Vert. Zool.; Washington, D. C. ; Novem- 

 ber 30, 1890. 



