GEOTHLYPIS. 221 



Total length, 4.40 ; wing, 2.15 ; tail, 2.30 ; graduation, .25 ; width of outer 

 tail feather, .23 ; difference between 1st and 3d quills, .15 ; length of bill from 

 forehead, .52, from nostril, .30 ; along gape, .GO ; tarsus, .75 ; middle toe and 

 claw, .86 ; claw alone, .18 ; hind toe and claw, .48 ; claw alone, .26. 



In autumnal plumage the whitish of th(5 belly becomes tinged with 

 yellowish, affording but little distinction from the yellow of the 

 breast and crissum. The black becomes obscured, especially that 

 on top of the head, by the extension forward of the brownish of the 

 vertex. The eyelids are apt to show a whitish ring. There appears 

 to be a tendency in the bill to become lighter colored, especially the 

 lower mandible, as in Icteria. I have not yet seen an autumnal 

 male with the black bill so characteristic of spring specimens. 



Specimens vary in the width of the black forehead, in that of the 

 hoary gray behind it ; the whole crown being sometimes of the latter 

 color, and the occiput behind it. 



In some western specimens the size is a little larger, and the bill 

 appears considerably stouter than in the eastern, but I cannot see 

 any other difference. 



West Indian, Mexican, and Guatemalan specimens do not present 

 appreciable differences, except what arises from their autumnal 

 dress ; all have the paler bills referred to above. 



The female bird either lacks the black mask entirely, or else it is 

 only appreciable on the sides of the head ; the whole top of the 

 head is usually strongly tinged with reddish-olive. The feathers on 

 the eyelids are generally whitish in the female and autumnal male, 

 quite different from the pure black of the spring male. 



I find considerable difference in specimens of this species, both as 

 to size and extent to which the yellow of the breast reaches over the 

 abdomen, etc. In some the black frontal band is bordered behind 

 by a narrow band of gray, abruptly defined against the olive of the 

 crown (2,535) ; in others it is of greater extent, and shades more 

 insensibly into the olive. In 10,95*7, from Fort Bridger, and some 

 others, this gray is nearly white, and as broad as or broader than the 

 black. I am, however, unable to see any permanent characters 

 looking to a separation into two species. The characters assigned 

 by Swainsou for his Trichas brachi/dactylus, as distinguished from 

 T. personatus, appear to be common to all specimens of Maryland 

 Yellowthroat I have ever seen. 



All specimens from Washington appear smaller, with slepderer 

 bills than others. 



As this species is found distributed throughout the entire extent 

 of the United States, from the Atlantic to the Pacific coast, and up 



