456 



THALASSIDROMA WILSONII. WILSON'S STORM- 

 PETREL 



Thalassidroma "Wilsonii. Bonap. Synops. 367. 



Wilson's Petrel. Thalassidroma WUsonii. Aud. Omith. Biogr. III. 486, 



V. 645. 

 Thalassidroma Wilsoni. Bonap. Comp. List. 



Tail even ; bill and feet black, but the interdigital mem- 

 branes yellow in the middle ; plumage greyish-black, tinged 

 with brown above, sooty-brown beneath ; outer secondary wing- 

 coverts and some of the secondary quills light-hroionish-grey , 

 terminally edged with white ; rump, sides of ahdomen and 

 outer lower tail-coverts white ; lejigth, seven inches and a 

 half 



Male. — Having examined several specimens of this species, 

 both skins and entire individuals preserved in spirits, I am 

 enabled, through the liberality of Mr. Audubon, who pre- 

 sented me with them, to give a detailed description of it. As 

 in the other species, the body is slender, the neck short, the 

 head of moderate size, and ovate. 



The bill is shorter than the head, slender, as broad as 

 high at the base, much compressed toward the end, with the 

 tip decurved and acute. The upper mandible has the dorsal 

 line a little concave to the end of the tube of the nostrils, 

 which appear to open by a single aperture, the septum being 

 considerably withdrawn, beyond them for a short space nearly 

 straight, then decurved, the ridge narrow, and separated by a 

 deep groove from the sides, which arc convex, the edges sharp 

 and inflexed, the tip slender, compressed, descending, and 

 acute. The lower mandible has the intercrural space narrow 

 and pointed, the lower outline of the crura little decurved, 

 the dorsal line very slightly concave, the sides erect, toward 



