278 University of California Publications in Zoology. [Vou 
1 
species are apparently the same as in the case of the males, but 
the material at hand is insufficient. It will be noted in the case 
of the males that artemisiae is decidedly the largest in general 
size, obscurus the smallest, while ater is intermediate, nearest 
artemisiac. But obscurus is much more nearly uniformly 
smaller than arfemisiae, than uniformly smaller than ater. Its 
range of variation in ratios of measurements in the six par- 
ticulars of the tables is five per cent. with artemisiae as compared 
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Figs. 1, 2. Molothrus ater ater, g ad.; no. 4767, coll. H. S. Swarth; 
Chieago, [l.; October 18, 1904. 
Figs. 3, 4. Molothrus ater artemisiae, § ad.; type, no. 8825, Univ. Calif. 
Mus. Vert. Vert. Zool.; Quinn River Crossing, Humboldt County, Nevada; 
May 31, 1909; C. H. Richardson, Jr. 
Figs. 5, 6. Molothrus ater obscurus, g ad.; no. 970, Univ. Calif. Mus. 
Vert. Zool.; Lano, Imperial County, California; April 21, 1908; J. Grinnell 
and ©. H. Richardson, Jr. All figures are natural size. 
to eleven per cent. with ater. The chief differential feature 
between artemisiae and ater is in the proportions of the beak, 
as shown in the accompanying drawings. After has a tumid bill, 
broad and high at base with conspicuously arched culmen. 
Artemisiae has a longer and relatively much slenderer bill, 
vertically shallow at base and laterally compressed, with the 
culmen in its greater portion straight or even slightly depressed. 
The beak of obscurus is practically a miniature of that of 
artemisiae. The average ratio of depth of bill at base to length 
of culmen is 56 per cent. in both obscurus and artemisiae, as 
contrasted with 62 per cent. in ater. The point which I wish to 
