330 WEB-FOOTED BIRDS. 



paler. Quills and tail pitch-black. The shafts of the primaries and of 

 the central tail feathers white to near the tips. Beneath hair-brown, 

 mixed on the ears and sides of the neck with yellowish-brown. Un- 

 der tail coverts darker. Axillaries and inner wing coverts black. 

 Interior of the quills greyish-brown, paler than any other part of the 

 plumage. Bill greenish-black, towards the base cylindrical, being 

 very slightly higher than broad ; culmen rounded ; upper mandible 

 towards the end rather hooked, and destitute of a distinct notch. 

 Legs and feet of a shining velvet black. Wings an inch longer 

 than the lateral tail feathers ; the primaries acute, the secondaries 

 truncated. Thighs bare for 8 lines. The tarsi protected anteriorly 

 by strong falciform or crescent-shaped scales; reticulated behind, as 

 well as the knee and tarsal joints. The soles of the feet and sides 

 of the toes and webs covered with small thick scales, which have 

 each a raised central ridge, or a sharp point. 



SWALLOW-PETRELS. (Thalassidroma, Vigors.) 



In these small birds of the ocean, the bill is shorter than the 

 head, slender, attenuated, much compressed, acute, and hooked at 

 the point ; upper mandible slightly seamed on each side ; the lower 

 shorter. Nostrils contained in a single tube carried out on the 

 top of the bill. Feet rather long and slender; naked space above 

 the knee extensive: tarsus longer than the middle toe, smooth; 

 middle toe nearly equal with the outer, the inner shortest : webs of 

 the toes small and somewhat indented : the hind toe merely a slen- 

 der, acute nail. Wings long and acuminated : the 1st primary 

 shorter than the 3d ; the 2d longest. Tail of 12 feathers, emarginate 

 or forked. 



The sexes alike in plumage ; and the young scarcely differ from 

 the adult in this respect. They are said to moult twice in the year 

 without changing their colors ; which are blackish, with more or 

 less of white, usually on the rump. They are the smallest of web- 

 footed birds. 



These are oceanic birds, wandering out far from the land nearly at 

 all seasons of the year, and are found in all parts of the world. 

 Their flight is rapid, like that of the swallows, which they so much 

 resemble in general appearance ; they fly low, skimming the water, 



