406 rniversify of California Puhlicatiovs in Zoology [Vol. 21 



broader rectrices, in greater propprtion of white on rectrices, in 

 broader white-tippings to inner primaries, and in slightly darker 

 color-tone of dorsum. 



Measurements. — Of Type : Wing, 93.4 mm. ; interval between ends 

 of secondaries and tip of longest primary, 25.6 ; tail, 52.3 ; greatest 

 width of outer rectrix, 10.0 ; greatest length of terminal dark bar on 

 outer rectrix, 12.0 ; greatest length of subterminal white patch on 

 inner web, 15.6; tarsus, 18.8; hind toe with claw, 20.0; middle toe 

 and claw, 20.4; culmen, 23.0; bill from nostril, 18.7; depth of bill at 

 nostril, 3.8 ; width of bill at nostril, 4.4 ; weight of bird, 16.4 grams. 

 For average dimensions in this and related subspecies see accompany- 

 ing table, and also Ridgway {loc. cii.). 



Eange. — So far as known, only the San Pedro jMartir plateau. 

 Lower California, between latitudes 30° and 31° 30'; altitude, 6000- 

 8500 feet; life zone. Transition and Canadian. Specimens exam- 

 ined, 16, all from the San Pedro Martir Mountains (Vallecitos, Arroyo 

 La Encantada, La Grulla), collected by Chester C. Lamb, Adrey E. 

 Borell, and J. Grinnell in May, June, and October, 1925. 



Comparisons and geographical considerations. — Judged from 

 study-skins, aJcrandrae might seem to be much larger than acuJeata; 

 but I believe this appearance is due to the greater relative length of 

 its wing, tail, and bill and not to any difference in body size. I am 

 led to this belief by weights of freshly taken birds, which are avail- 

 able as follows. The average weight of 16 ale.ranclrae is 16.6 grams 

 (extremes 15.5 and 17.7) ; of 21 aculeata from west-central and 

 northern California, 17.7 grams (16.7 and 19.1). Indeed, such differ- 

 ence as does obtain indicates alexandrae to be the lighter. This fact 

 is not due to unequal proportions of the sexes, for the two sexes 

 weigh practically the same ; thus, in alexandrae 10 males average 

 16.5 grams, and 6 females average 16.7 ; in aculeata 15 males average 

 17.8, 6 females 17.5. Furthermore, the examples of the two races 

 weighed are representative of about the same season. Therefore the 

 greater dimensions of alexandrae as compared with aculeata mean 

 the relative elongation of wing, bill, and tail. 



As to this wing difference, I find that, in the dimension taken (the 

 usual chord of wing), it is in good part occupied by the interval in 

 the closed wing (not "stripped" in preparation) between the super- 

 imposed ends of the secondaries and the tip of the longest primary. 

 Thus, this interval in 5 unworn males of alexandrae averages 25.8 

 millimeters, while in 8 similar males of acuJeata it averages 23.3. In 

 other words, this difference in wing length is due in significant part 

 to the lengthening of the primaries; the wing is "sharper." 



Not only are the feathers of the tail in alexandrae longer, but they 

 are broader, than in aculeata. 



