42 



KEY TO FAMILIES. 



A. Tip of the upper mandible more or less swollen, rounded, and 

 sharply pointed; upper parts, including wings, and sometimes the 

 entire plumage, dark sooty blackish, sometimes irregularly barred ; 

 tail always dark, the middle leathers longest. . . . Family iSterco- 

 rariidce : Skuas and Jaegeks (Fig. 6, a), p. 65. 



£. Upper mandible curved but not swollen at the end ; tail generally 

 white, sometimes tipped with black ; the tail-feathers usually of about 

 equal length. . . . Subfamily Larinoe : Gulls (Fig. 6, J), p. 67. 



Fig. 8. 



C. Bill straight, not hooked and sharply pointed ; outer tail-feathers 

 generally longer than the middle ones. Subfamily Sterninoi : Terns 

 (Fig. 7), p. 76. 



D. Bill thin and bladelike, the lower mandible much longer than the 

 upper one. . . . Family Rynchojoidce : Skimmers (Fig. 8), p. 85. 



y 



a \ 



Fig. 9. 



Order III. Tubinares.— Albatrosses, Petrels, and Fulmars. 



Bill hawklike, the tip of the upper mandible generally much enlarged ; 

 nostrils opening through tubes; hind toe reduced to a mere nail, and 

 sometimes entirely wanting. 



A. Size very large, nostrils separated and on either side of the bill. . . . 

 Family Diomedeidoe : Albatrosses (Fig. 9, a), p. 86, 



B. Size smaller, nostrils joined and placed on top of the bill. . . . 

 Family Procellariidon : Petrels, Fulmars, and Shearwaters (Fig. 



9, &), p. 86. 



