850 U. Ss. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
CHROICOCEPHALUS, Eyton. 
Chroicocephalus, Eyton, Cat. Brit. Birds, 1836. 
Cu.—Bill moderate, rather slender, much compressed; upper mandible straight at base, more or less curved at the end; 
nostrils lateral and longitudinal ; wings long, narrow, and pointed ; tail moderate, usually even ; tarsi rather slender ; feet 
webbed ; hind toe small and elevated. 
These gulls are of medium or small size; in their spring attire the head is clothed with a 
dark colored hood, but in winter it becomes white, with a dusky spot behind the ear. These 
birds are very handsome, the dark and light colors of their plumage forming a beautiful 
contrast. 
The species of this genus are beautiful birds, and readily known by the dark colored hood or 
cowl which envelopes the head in summer. Five species are enumerated as belonging to the 
United States, but the occurrence of minutus may be considered as accidental. They may be 
known by the following characters : 
Mantle and wings grayish blue; hood blackish lead gray; narrow white lines on the 
upper and lower cy clidSiev ccs sav-ncecntcessdeshe taceoessscas-stieceessomsicnstueerwscamas CpOLnUChlGs 
Mantle and wings dark bluish gray ; hood plumbeous black, eyelids white..C. franklinii. 
Mantle and wings ash blue; hood plumbeous black ; an oval white spot over the eye and 
one on the lower eyelidict tes. ascecesccce forsee. coca ccestetnsecstecsosessecestsetentess() CUCTLUALUS. 
Mantle and wings light grayish blue; hood grayish black; a white band divided by a 
narrow black line surrounds the posterior part of the eye............000C. philadelphia. 
Mantle and wings pale bluish gray ; hood black ; behind the eye a white crescent......... 
C. minutus. 
CHROICOCEPHALUS ATRICILLA, (Linnaeus.) 
The Laughing Gull. 
Larus atricilla, Linn, Syst. Nat. I, 1766, 225.—Bonap. Syn. 1828, No. 294.—Nurvr. Man. II, 1834, 291—Avp. Birds 
Am. VII, 1844, 136; pl. eccexliii. 
Larus ridibundus, Wis. IX, 1824, 89; pl. Ixxiv. 
Alricilla catesbyi, Brucu, Cab. Jour. 1855, 287. 
Sp. Cx.—4dult. Head and upper part of neck blackish lead gray, extending lower in front ; upper and lower eyelids white 
posteriorly ; lower part of neck, entire under plumage, rump, and tail pure white ; in spring a beautiful roseate tint exists on 
the breast and abdomen ; back and wings grayish lead color ; the first six primaries are black, beginning on the first at about 
two-thirds of its length from the point and regularly becoming less on the others until on the sixth it is reduced to two spots 
near the end ; tips in some specimens white, and in others black to their points; bill and inside of the mouth dark carmine ; 
iris bluish black ; legs and feet deep red. In winter the head becomes white, intermixed on the crown and hind neck with 
brownish gray. 
Length, 17 inches; wing, 13; tail, 5; bill, 12 ; tarsus, 2 inches. 
Hab.—Texas to Massachusetts. 
