128 PROCEEDINGS OF THE ACADEMY OP 



This species is very closely related to the preceding, if it be really distinct 

 from it. The fine series in the Museum of the Smithsonian Institution, pro- 

 cured by the United States Exploring Expedition under Com. Wilkes, all 

 differ from the skua of Europe and America in the possession of shorter, and 

 comparatively stouter and deeper bills, with more obtuse tips. These are the 

 only points of discrepancy I have been able to detect in the examination of 

 the series ; but they appear to be quite constant. 



Among the series is a specimen much larger than the rest, and than the 

 slcua from Europe. The bill is nearly two and a third inches long, and very 

 stout ; the wings an inch, and the tarsus a third of an inch longer than the 

 average of European skins. It is evidently a very old individual, and the 

 chestnut and whitish have almost entirely disappeared from both the upper 

 and under parts, leaving the whole bird deep blackish-brown above, and a 

 somewhat lighter brown, or fuliginous, below. The specimen is referred to 



in Cassin's List of the Birds of the Exploring Expedition, as " Lestris ?" 



Although the general appearance of the bird is really different from that of 

 the rest of the series, I do not think that the differences presented are any- 

 thing more than indicative of the great age of the specimen. A collection of 

 American and European Jiigers, obligingly furnished by Mr. D. G. Elliott for 

 examination, contains a specimen of the true skua from the Atlantic Ocean, 

 which presents a very similar condition of things. The size is greater than 

 that of any other of the series of specimens, and the colors are nearly as 

 uniform as in the antarctic specimen referred to. I think it more than probable 

 that the birds of this genus continue to grow in size and proportions with 

 increasing age, and that the colors have a tendency to become darker and 

 more uniform under the same circumstances. 



Genus STERCORARIUS Brisson. 



Sterc'orarius, Brisson, Ornithologia, 1760, vi. (Typus Larus parasiticus, Linn.) 



et auctorum pleriq. 

 Catharacta (partim), Briinnich, Ornith. Borealis, 1764. 

 Larus (partim), Linnaeus, Systema Naturae, 1766. Gmelin, Systema Natune, 



1788. Latham, Index Ornithologicus, 1790. Meyer et Wolf, Taschenb. 



Deutsch, 1810. 

 Lestris, Illiger, Prodromus, 1811, p. 272. (Typus Larus parasiticus, Linn.) 



Et auctoram. 

 P)-mdatrix, Vieillot, Analyse, 1816, p. 62. 

 Labbus, Rafinesque, 1816, fide Bp. 

 Coprothcres, Reichenbach, 1850. 



A single genus cannot, without great latitude and looseness of definition, be 

 made to include all the species of this subfamily. The differences between 

 Buphagus skua (with its southern representative antarcticus) and the other 

 known species, are very great, and strongly pronounced, if we regard stature, 

 proportions, character of central tail feathers, changes of plumage, &c. The 

 differences fully warrant the distribution of the species of the subfamily into 

 two genera, which may be thus defined : 



Buphagus. Bill shorter than the middle toe without the claw ; exceedingly 

 robust ; width at base about equal to the height, which is a third of the length 

 of culmen. Stria? and sulci numerous and well marked. Encroachment of 

 feathers on bill moderate ; and nearly the same on both mandibles. Occiput 

 scarcely crested. Wings only moderately long for this subfamily, the pri- 

 maries very broad, and rounded at their tips. Tail very short, broad, nearly 

 even, the feathers truncated ; central pair projecting but little, and broad to 

 their very tips, which are also truncated. Feet large and stout ; tarsi shorter than 

 the middle toe and claw. Size large ; form robust and heavy ; general 

 organization very powerful. Colors much the same over the whole body ; 



[May, 



