477 



LESTRIS. SKUA. 



A gi-oup of birds nearly allied to the Petrels, and more 

 intimately to the Gulls, from which they are readily distin- 

 guishable by their bolder and somewhat faleonine aspect and 

 habits, has generally been considered as forming a single 

 genus, to which some give the name of Cataractes, others 

 that of Lestris. They who divide the Gulls into two or 

 more series ought not, perhaps, to object to an arrangement 

 of the birds in question into two genera, especially if they 

 consider them as forming a sub-family. Considering that 

 they scarcely merit generic distinction, and that no other very 

 obvious external character than that presented by the form 

 and elongation of the two middle feathers of the tail can be 

 adduced, we may, notwithstanding the method of rather 

 minute division followed in this work, refer them to a single 

 genus. 



The body is of a compact and robust form ; the neck of 

 moderate length ; the head large, ovate, anteriorly narrowed. 

 Bill shorter than the head, about as broad as high at the 

 base, compressed toward the end, straight, with the tip 

 decurved ; upper mandible cerate for half its length, with 

 the ridge broad and rounded, the nasal space covered by a 

 thin plate ; nostrils linear-oblong, wider anteriorly, pervious ; 

 edges sharp and inflected ; tip very strong, laterally convex, 

 much decurved, thin-edged, rather obtuse ; lower mandible 

 Avith the intercrural space long and narrow, the branches 

 broad and erect, the prominence formed at their junction 

 slight, the edges sharp and inflected, the tip compressed, 

 thin-edged, obtuse. 



Mouth rather wide and dilatable ; tongue broadly chan- 

 nelled above, contracted and induplicate toward the end ; 

 oesophagus very wide ; stomach small, moderately muscular. 



