NATURAL SCIENCES OF PHILADELPHIA. 
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near the angle, which is well developed, the outline from angle to tip perfectly 
straight. Feathers extending between the rami nearly to the angle! Wings 
long and pointed, reaching beyond the tail ; primaries gradually attenuated to 
the tip. Adult: Entirely pure white, the shafts of the primaries straw yellow. 
Bill dusky greenish yellow at tip, and along the cutting edges. Legs and feet 
black. Length 19-50 inches; wing 13-25; bill above 1*40, along gape 2-10, 
height at nostrils -45 ; tarsus about 1-45 (varying) ; middle toe and claw 1*75. 
Habitat . — Northern coasts of both continents. 
17. Pagophila brachytarsus Bruch ex Holb. 
Larus brachytarsus , Holb. 1846. Pagophila brach. Bruch, 1855. P. brachy- 
tarsi , Lawr. 1858. Larus niveus, Brehm, fide Bp.; (nec Pall. 1811.) Pago- 
phila niveus , Bp. 1856. 
Sp. char . — “Bill yellow, with a darker tip. The long wings, which when 
folded reach two and a half inches beyond the tail, are distinguished from those 
of all other Gulls by the extraordinary breadth of the four first primaries. 
Color snow-white, with or without dark brown spots. Feet and webs black, 
the latter very deeply excised. Length 17 inches ; extent 40 ; tail 5 ; tarsus 
one inch ; middle toe 1-75. Breadth of outer primary four inches from tip 1*23.” 
Habitat . — “ Greenland.” 
Never having seen a specimen of this supposed species, I have nothing to 
offer with regard to its relationships to the P. eburnea. The description is com- 
piled from Holboll’s original account. 
Genus Y. Chroicocephalus Eyton. 
Xema , Boie, 1822 ; (nec Leach, 1818.) 
Gavia , Kaup, 1829 ; (tvpus L . ridibundus ; nec Moehr. 1752.) 
Ichthyaetus , Kaup, 1829; (t. L. ichthyaetus, Pall.) 
Hydrocoloeus , Kaup, 1829 ; (t. L. minutus , Pall.) 
Chroicocephalus , Eyton, 1836 ; (t. L. capistratus, Temm. fide Gray.) 
Gavia , Macgill. 1842, p. (Nec Moehr. 1752.) 
Atricilla , Bonap. 1854; (t. Atricilla Catesbyi, Bp ) 
Cirrhocephalus , Bruch, 1855 ; (t. L. cirrhocephalus , Vieill.) 
A. — Large ; bill rather stout, tip much decurved ; middle toe and claw three- 
fourths the tarsus. 
18. Chroicocephalus atricilla Lawr. ex Linn. 
Larus atricilla , Linn. 1766. L. ridibundus, Wils. ; (nec Linn.) * L. major , 
Catesb. Atricilla Catesbyi , Bonap. (fide Bruch.) Chroico. atricilla , Lawr. 
1858. \ 
Sp. char . — Bill deep carmine. Hood deep plumbeous, grayish black, extend- 
ing further on the throat than on the nape. Eyelids white posteriorly. Mantle 
grayish plumbeous. Length 16-50 inches; wing 13; bill above 1-75; tarsus 
2-00; middle toe and claw 1-50. 
Habitat . — More southern portions of Atlantic coast of North America. Texas. 
B. — Medium ; tarsus equal to the middle toe and claw. 
19. Chroicocephalus cucullatus Bruch ex Licht. 
Larus pipixcan, Wagler. L. melanorhynchus , Temm. fide Bruch. Chroicoce- 
phalus cucullatus , Bruch, 1855 ; Lawr. 1858. 
Sp. char . — Bill very short, scarcely more than two-tbirds the head, about 
three-fourths the tarsus, moderately stout, the culmen regularly curved from 
base to tip ; angle well defined and very prominent. Adult : hood deep plum- 
beous black, barely encircling the head, not extending further on the throat 
than on the nape.^ Lower eyelid white, upper more broadly so, the white ex- 
tending behind the eye. Mantle bluish plumbeous, as in Franklinii , with more 
blue than in atricilla. Primaries : Shafts of three outer black, of the inner 
1862.] 
