78 AVES. 



tudinal furrow on each side : gonys concave, more or less 

 ascending: nostrils at the extremity of an open truncated 

 tube extending along the culmen : a simple claw in the 

 place of a hind toe: wings long; first or second quill 

 longest. 



(1. PROCELLARIA.) Bill moderate, robust ; lower mandible straight, 

 somewhat truncated at the tip ; mental angle projecting : nostrils 

 opening by a single orifice, the tube extending half the length 

 of the bill : tail slightly rounded. 



(2. PUFFINUS.) Bill longer than the head, slender; lower mandible 

 pointed, deflected at the tip, following the curvature of the 

 upper ; mental angle obsolete : nostrils in a double tube ex- 

 tending one-fourth of the length of the bill : tarsi moderate : 

 tail rounded. 



(3. THALASSIDROMA.) Bill shorter than the head, slender; lower 

 mandible pointed, deflected at the tip, following the curvature 

 of the upper : mental angle obsolete : nostrils opening by a 

 single orifice, the tube extending half the length of the bill : 

 tarsi slender, elevated: tail square, or slightly forked. 



