BIRDS — GAVIAE 819 



Procellaeidab. — Nail only of hind toe projecting. Nasal apertures circular, opening 



in projecting tubes. Bill with a much decurved nail at tip. Outer toe as long as the 



middle. Legs reticulated in front. 

 Laridab. — Hind toe free when present. Nasal apertures linear, opening laterally ; not 



at all tubular. Bill without nail except in Lestris. Outer toe shorter than the middle. 



Legs scutellate transversely in front. 



C. Brachypteri. — Wings and tail short, the latter sometimes wanting. Hind toe free, or 

 wanting. Legs very far backwards. Entirely aquatic, and for the most part capturing the 

 food beneath the water. 



CoLTMBiDAE. — Hind toe distinct, with a broad hanging lobe. The membrane of toes 



entire, or divided. Claws nail-like, flattened. Mostly inhabit fresh waters of all 



countries. 



Alcidab. — Hind toe wanting. Claws compressed. Entirely marine, and chiefly arctic. 



In a strictly natural arrangement the Totipalmi should, perhaps, precede the Longipennes. 



In order, however, to facilitate the passage of the present report through the press, the latter 



tribe has been made to begin the sub-order, as the manuscript belonging to it was first ready for 



the printer. For a similar reason the Anseres come before the Gaviae, although most authors 



place them last. 



The determinations and descriptions of the Gaviae have been prepared and furnished by 

 Mr. George N. Lawrence, with the exception of the Alcidae, which are from the pen of 

 Mr. John Cassin. 



