xxiv SYSTEMATIC ARRANGEMENT OF THE GENERA OF BIRDS 
SUB-FAMILY LARIN& 
Bill with upper mandible longer and bent over tip of under one. 
130. Larus (Gull). Bill moderate, strong, sharp-edged above, compressed, 
slightly decurved ; hind toe high on the tarsus ; first primary nearly 
equal to the second, which is longest; tail even, or but slightly 
forked. Page 281 
131. Russa (Kittiwake). Bill rather short and stout, considerably decurved; 
hind toe minute and usually obsolete; first primary slightly exceed- 
ing second ; tail perceptibly forked in young, nearly square in adult.: 
Page 287 
SUB-FAMILY STERCORARIINZE 
Bill with a cere; claws large, strong, hooked. 
132. STERCORARIUS (Skua). Bill moderate, strong, rounded above, com- 
pressed towards the tip, which is decurved; nostrils far forward, 
diagonal, pervious; hind toe very small, scarcely elevated; the 
middle tail-feathers more or less elongated. Page 288 
ORDER PYGOPODES 
Wings short 
FAMILY ALCIDZ 
(AUKs) 
Bill much flattened vertically (compressed) ; wings short; legs placed at 
the extremity of the body; feet three-toed, palmated; tail short. Food, 
mostly fish, and captured by diving. 
133- Atca (Razorbill). Bill large, sharp-edged, the basal half feathered, 
the terminal part grooved laterally; upper mandible much curved 
towards the point; nostrils nearly concealed by a feathered mem- 
brane; tail pointed. Page 291 
134. Uria (Guillemot). Bill strong, nearly straight, sharp-pointed, of 
moderate length; nostrils basal, partly covered by a feathered 
membrane}; first primary longest. Page 292 
135- MeErRcutus. (Little Auk). Bill strong, conical, slightly curved, 
shorter than the head; nostrils basal, partly covered by a feathered 
membrane; first and second primaries equal. Page 294 
136. FRATERCULA (Puffin). Bill shorter than head, higher than long, 
ridge of upper mandible higher than crown; both mandibles much 
curved throughout, transversely furrowed, notched at tip; nostrils 
basal, almost closed by a naked membrane. Page 295 
FAMILY COLYMBIDZ 
(DIVERS) 
Bill slightly compressed, not covered with a membranous skin; edges of 
the mandibles unarmed, or but slightly toothed; wings short; legs placed 
far behind ; tarsi very much compressed; toes four. Food, fish and other 
aquatic animal substances obtained by diving. FFemalessmaller than males. 
137. CoLtymBus (Diver). Bill forming a pointed cylindrical cone; front 
toes entirely palmated ; tail very short. Page 297 
