42 R. Ridgway— Relation between Color and 
the northern race of C. Steller should grade into C. macrolopha, 
and why the southern one does not, seems to be easily explained 
by the following facts: The habitat longitudinally of C. cor- 
onata (var. macrolopha) within the United States is exceedingly - 
limited, it being confined to the central ranges of the Rocky 
Mountain system; thus it is everywhere separated from the 
habitat of Stelleri var. frontalis, which is equally restricted longi- 
tudinally by that broad desert expanse, the Great Basin, which 
affords no sheltering woods such as are furnished on the two 
boundary barriers, the Sierra Nevada and the Rocky Moun- 
tains, which each represents. 
e northern limit to the range of C. macrolopha passes just 
a little beyond the southern limit of the habitat of the north- 
ern race of the coast stock, and at a latitude where the ‘Great 
Basin a greatly reduced in width, or even terminates, 
and where the two great mountain systems become less dis- 
tinctly aati Consequently the coast stock cannot grade 
into the Rocky Mountain one, by iwgoaeine) its habitat, er 
before it becomes modified into var. frontalis. Thus in the 
rd parallelism of modification on 
tween Stelleri var. frontalis and 
coronata var. macrolopha, as we 
trace the two forms southward, 
we recognize merely the effect of 
a latitudinal influence. The coast 
stock reaches its southern limit 
with the Sierra Nevada, and this 
of course prevents it from passing 
into C. coronata var. diademata. 
he proportionate jeeenemels 
of these two forms may be mo 
clearly illustrated by the follow. 
ing diagram and synopsis; the letters and figures of the former 
representing those of the latter 
A. Supraocular spot of white; Se wing-coverts barred with 
black; chin and throat abruptly lighter than adjacent parts 
ae sarbniataks 
ead and crest deep blue; back purplish blue B gpears 
amount of blue). Hab. Vera Cruz to — 
sho onata.* 
2. Head and crest blue-black, er tinged with blue; 
back agora iseae (Int termediate rm.) Hab. Central 
regions of Mexico, a diademata.t 
* CYANURA CORONATA var. 
Cyanura coronata Swains, Phil. 2 aaa +) 1, 182%, 437. 
Hab, Eastern Mexico and Honduras. (No orth to Mirador and Xalapa.) 
. Central table-lands and mountains of Mexico. 
