LABIDJ;— THE GULLS AND TEBNB. 223 



The species belonejing to eastern North America may be char- 

 acterized as follows: 



A. Adult with the entire head, neck, lower parts, and tail pure white. (Larus, Link.) 



a. 'Mantle very pale pearl-blue; primaries the same, fading into white toward the ends. 



1. L. elauous. Wins, 16.75-18.<i0 inches; oulmen, 2.15-2.65; depth of blU through the 

 angle, .75-1.00; tarsus, 2.30-3.00; middle toe, 1.95-2.50. Eyelids In summer adult, red- 

 dish purple; feet flesh-color. 



2. 1. leuoopterus. Wing, 15.40-16.50 inches; culmen, 1.65-1.90; depth of bill through 

 angle, .C0-.70; tarsus. 2.05-2.20; middle toe, 1.70t].95. Eyelids in summer adult, flesh- 

 color i feet inclining to orange-red. 



b. Mantle pale pearl-blue ; primaries similar, but abruptly tipped with white. 



3. L. kumlieni. Five outer prio^aries marked with' slate-gray spaces immediately be- 

 fore the white tips; color of the mantle as in Z.' Zeucojiferus, and size about the 

 same. Eyelids in summer adult reddish purple, or purplish flesh-color ; feet flesh- 

 color. Wing, 15,00-17.00 inches ; oulmen, 1.60-1.90 ; depth of bill through angle .55-.66 ; 

 tarsus, 2.10-2.40. Sab. North Atlantic coast, breeding in Cumberland Bound, and 

 migrating south in winter to Nova Scotia, New Brunswick, and New York. 



c. Mantle dark slate-color, the primaries marked with black and white terminally. 



4. L. marinas. Wing, 17.60-19.50; culmen, 2.40-2.6«; depth of bill at angle; .98-1.05; 

 t tarsus, 2.79-3.10. Kab. Coasts of the North Atlantic. I 



d. Mantle some shade of bluish gray; primaries marked with black and white at and 



near the end. 



5. L. argentatuB. Wing, 15.75-17.90 inches; culmen, 1.85-2.20; depth of bill through 

 angle, .70-.80; tarsus, 2.30-2.72; middle toe, 1.85-2.25. Mantle pale pearl-blue. Bill 

 deep yellow, the mandible with red subterminal spot; eyelids yellowish; iris sil- 

 very white or pale yellow; legs and feet flesh-color. 



6. L. argentatus sniithsonijnus. Similar to true L. argentatus, but averaging larger 

 and with less white and more black on primaries. Wing, 16.25-17.50; oulinen, 1.95- 

 2.50; depth of bill through angle, .68-.85; tarsus, 2.30-2 80: middle toe,1.85-2.25. 



7. L. delawarensis. Mantle pale pearl-blue (much as in L. argentatus). Wing, 13.60- 

 15.75 inches; oulmen, 1.S5-1.75; depth of bill through angle, .5(V-.66 ; tarsus, 1.90-2.45 ; 

 middle toe, 1.30-1.60. Bill greenish yellow, crossed near the end by a blackish 

 band, the tip sometimes tinged with orange: eyelids vermllion-red; iris clear pale 

 yellow; legs and feet pale yellow, sometimes tinged with greenish. 



8. L. oanns. Mantle pale ashy blue (as in L. brachyrhynchua). Wing, 13.90-14.50 

 inches; oulmen, 1.35-1.60; depth of bill through angle, .45-.60; tarsus, 1.90-2.26; mid- 

 dle toe, 1.35-1.46. Bill greenish olivaceous (in the dried skin), the terminal third 

 yellow; eyelids vermilion-redj iris grayish brown; legs and feet yellowish gi-een. 

 Sab . Palaearetic region ; acoid''ental in Labrador ? 



B. Adult with the head and upper part of the neck black or slaty in summer, forming a 



well defined "hood;" plumage of the lower parts rose-tinted; size medium to very 

 small; the bill slender. (Chroioooephalus, Eyton.) 

 a. Tarsus longer than the middle toe and claw. 



9. L. atrioilla. Bill and feet dark brownish red, the former sometimes tipped with 

 brighter red; eyelids dull red; iris dark brown; hood dark sooty-slate; mantle 

 deep plumbeous-slate. Wing, about 13.00 inches. 



B. Tarsus shorter than the middle toe and claw. 



10. L, franklinii. Bill and feet carmine-red; iris dark brown; hood plumbeous-black; 

 mantlQ deep bluish plumbeous. Wing, about 11.2S inches. 



11. L, Philadelphia. Bill uniform deep black: legs and feet flue orange-red in summer, 

 flesh-oolor in winter; iris dark brown; hood dark plumbeous; mantle delicate 

 pearl-blue; Wing, about 10.25 inches. 



12. L, minutus. Bill reddish dusky; legs and feet vermiUon- or coral-red; hood deep 

 black; mantle delicate pearl-gray; primaries without any black markings. Wing, 

 about 8. 7S-9. 00 inches. Sab. PaleearctlcBegion; accidental in Massachusetts and 

 Bermudas. 



