NATURAL SCIENCES OP PHILADELPHIA. 309 



near the angle, which is well developed, the outline from angle to tip perfectly 

 s^aight. 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 ar.d feet 

 black. Length 19-50 inches; wing 13-25; bill above 140, 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. Pacjopbila brachytarsus Bruch ex Holb. 



Larus brachytarsus, Holb. 1846. Pagophila brack. Bruch, 1855. P. Lrachy- 

 tarsi, Lawr. 1858. Larusniveus, Brehm, fide Bp. ; (nee 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 V. Chroicocephalds Eyton. 

 Xenia, Boie, 1822 ; (nee Leach, 1818.) 



Gavia, Kaup, 1829 ; (typus L.ridibundus ; nee Moehr. 1752.) 

 Ichthyaetus, Kaup, 1829; (t. L. ichthyaetus, Pall.) 

 Hydrocoloeus, Kaup, 1829 ; (t. L. minulus, Pall.) 

 Chroicocephalus, Eyton, 1836 ; (t. L. capistratus, Temm. fide Gray.) 

 Gavia, Macgill. 1842, p. (Nee Moehr. 1752.) 

 Atricilla, Bonap. 1854; (t. Atricilla Caiesbyi, 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. ; (nee Linn.) L. major, 

 Catesb. Atricilla Caiesbyi, 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 cccdllatus Bruch ex Licht. 



Larus pipizcan, Wagler. L. melanorhynchus, Temm. fide Bruch. Chroicoce- 

 p h at 'us cucullatus, Bruch, 1855; Lawr. 1858. 



Sp. char. Bill very short, scarcely more than two-thirds 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.] 



