636 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



KEY TO THE SPECIES OF CHROICOCEPHALUS. 



a. Tarsus much longer than middle toe with claw, the latter decidedly shorter than 



exposed culmen. 



b. Tail entirely white; back, scapulars, and wings uniform neuti-al gray, the longer 



primaries partly black; head dark quaker drab in summer. (Atlantic and 



Gulf coasts of United States and West Indies; coast of western Mexico in 



winter; casual in Mississippi Valley. ).Chroicocephalus atricilla, adults (p. 636). 



bb. Tail gray and blackish; scapulars, interscapulars, and wing-coverts grayish 



brown broadly margined with whitish or pale buffy; chest and breast brownish 



gray or grayish brown, like head and neck. 



Chroicocephalus atricilla, young (p. 637). 

 aa. Tarsus not longer than middle toe with claw, the latter longer than exposed 

 culmen. 

 b. Bill much stouter, its depth at gonydeal angle equal to more than one-fourth the 

 length of exposed culmen, reddish; three outer primaries without wliite, except 

 at tips, 

 c. Tail white, shaded with gray on middle rectrices; back, scapulars, and wings 

 uniform neutral gi'ay, the longer primaries partly black and white; head 

 dusky piu*plish gray and bill deep red in summer. (Interior of North 

 America, south in winter to Peru, Chile, etc.). 



Chroicocephalus franklinii, adults (p. 641). 



cc. Tail pale gray or grayish white with a broad subterminal band of blackish; 



back and scapulars grayish brown, some of the latter margined terminally 



with pale grayish buffy; bill blackish, with reddish or pinkish tinge basally. 



Chroicocephalus franklinii, young (p. 642). 

 bb. Bill much more slender, its depth at gonydeal angle equal to less than one- 

 fourth the length of exposed culmen, black; three outer primaries extensiA^ely 

 white, 

 c. Tail entirely white; back, scapulars, and wing-coverts uniform pale neutral 

 gray; head very dark purplish gray in summer. (Whole of North America, 

 breeding northward; southward in winter to Yucatan, Jalisco, etc.) 



Chroicocephalus Philadelphia, adults (p. 645). 



cc. Tail with a broad subterminal band of black; scapulars and interscapulars 



grayish brown , tipped with pale buff; central area of lesser wing-covert tract 



dusky Chroicocephalus Philadelphia, yoimg (p. 645). 



CHROICOCEPHALUS ATRICILLA (Linnaeus). 



LAUGHING GULL. 



Adults in suminer (sexes alike). — Head and upper half of neck 

 (extending farther downward in front than behind) plain dark sooty- 

 gray or dark quaker drab), darkest on upper neck; a small elongated 

 spot of white on each eyelid; lower neck (all round), upper tail- 

 coverts, tail, and under parts immaculate white, the under parts 

 sometimes (in newly killed specimens) tinged with delicate pink; 

 back, scapulars, wings, and rump uniform neutral gray, the tertials, 

 secondaries and proximal primaries broadly tipped with white; five 

 outer primaries black, with or ^yithout a small apical spot of white, the 

 third, fourth, and fifth (from outside) with basal portion gray for a 

 greater or less distance, this sometimes abruptly defined against the 

 black of distal portion, sometimes shading gradually into it; remain- 



