^1889."'] PROCEEDINGS OF THE NATIONAL MUSEUM. 117 



46. Creagrus furcatus (Nkb.). 



Chatham Island ( Dairy mple Iiock), two specimens (adult male and 

 female in perfect summer plumage). 



This fine species, from its great rarity and the uncertain history of the 

 type specimen, is worthy of somewhat extended discussion. Although 

 a special genus, Creagrus, was instituted for it by Bonaparte, it has by 

 most recent writers been referred to the genus Xema, Leach; but this 

 is a view of its affinities in which I can not concur, since, beyond a sim- 

 ilarity in the color of the bill and to a less extent in that of the plumage 

 and in the shape of the tail, I see no particular resemblance. In fact, 

 Creagrus seems to me to be one of the best, if not the very best, charac- 

 terized of all the genera or subgenera of Larinw, excepting only Gavia, 

 Bissa, and Bhodostethia. 



From Xema, the points of difference are many and decided. The bill 

 is very peculiar in shape, being much deeper at the base than elsewhere 

 and strongly decurved at the tip; that of Xema being much smaller 

 proportionally, much straighter, and much deeper through the angle 

 than at the base. The tail is relatively much longer and much more 

 deeply forked, being nearly half as long as the wing and forked for 

 about one-third of its length, while that of Xema is much less than half 

 as long as the wing and forked for not more than one-eighth of its 

 length. As to coloration, there is even greater difference, Creagrus hav- 

 ing the dark "hood " descending much farther down over the neck, and 

 instead of being very abruptly terminated by a black border has no very 

 definite outline except on the fore neck; while the white patch at the 

 base of the upper mandible and the very conspicuous white stripe mar- 

 gining the exterior scapulars are entirely peculiar features. Moreover, 

 the plumage of the young is quite distinct in its character from that of 

 Xema. 



Compared with Xema sabiriu, Creagrus furcatus is a large gull, about 

 the size of Larus delawarensis, while the former is hardly so large as L. 

 Philadelphia, and with its dark colored head, deep red feet, and deeply 

 forked tail ought to be very easily identified at a considerable distance. 



The perfect summer plumage of the adult may be described as fol- 

 lows: 



Adult male, breeding plumage (No. 115967, Dalrymple Eock, Chatham 

 Island, Galapagos, April 6, 1888; U. S. S. Albatross) : A white patch 

 at base of upper mandible, crossing anterior portion of forehead, and 

 averaging about .35 of an inch in width ;* a very small white spot on 

 the apex of the malar region; rest of head, with upper half of neck 

 uniform slate-color,t this rather abruptly terminated on the fore-neck, 

 but posteriorly fading gradually into the lighter gray of the hind neck; 



* This white patch does not extend as far down as the edge of the mandible, 

 t Corresponding to the slate-color (No. 4, plate n,)of my " Nomenclature of Colors," 

 but slightly browner. 



