BIRDS OF NORTH AND MIDDLE AMERICA, 675 
Bill stout, the exposed culmen shorter than middle toe without 
claw, its depth at base equal to or slightly greater than its width at 
same point and at least equal to one-third the length of exposed 
culmen; supra-nasal saddle, measured from loral antia, longer than 
distance from its anterior end to tip of the strongly decurved or unci- 
nate tip of maxilla; gonys less than half as long as mandibular rami 
(measured to point of malar antia), rather strongly ascending term- 
inally, faintly concave, its basal angle prominent; nostril with anterior 
end nearer to tip of maxilla than to loral antia, the latter on nearly 
the same vertical line as malar antia or slightly anterior to it, the 
mental antia decidedly anterior to both. Wing moderately long, the 
longest primary (outermost) exceeding distal secondaries by not more 
(sometimes less) than half of the length of wing; primaries 
broad, rounded at tips, their shafts thick and rigid; sec- 
ondaries relatively short and broad, with inner webs longer 
than outer webs; tertials elongated, but falling considerably short of 
tips of longest primaries. Tail less than half as long as wing, nearly 
truncate, the rectrices sub-truncate at tips, the middle pair project- 
ing slightly, if at all, beyond the next pair; tail-coverts very long 
and full, the lower ones reaching to or beyond tips of lateral rectrices. 
Tarsus as long as middle toe without claw, strong, the lower half or 
more of the acrotarsium covered with a single series of obliquely 
transverse scutella, the upper portion with a double row of similar 
but shorter scutella, the planta tarsi covered with small, irregular 
scales, the sides of tarsus with larger hexagonal scales; outer toe 
slightly shorter than middle toe, the inner toe much shorter, the 
hallux very short; anterior toes fully webbed; claws relatively large, 
strongly curved, acute, that of middle toe with inner edge dilated. 
Coloration.—General color brown or sooty, usually indistinctly 
streaked with light rusty, cinnamon, or buffy, especially on neck and 
back; primaries whitish. basally. 
Range.—Northern portions of North Atlantic. and southern parts 
of South Atlantic oceans, southern parts of Indian Ocean, Antarctic 
Ocean, seas near New Zealand, and Pacific coast of Chile and Peru. 
(At least four species or subspecies.) 
KEY TO THE SPECIES OF MEGALESTRIS.@ 
a. Billrelatively longer and narrower, with anterior edge of supra-nasal saddle (viewed 
from above) strongly concave; under parts more or less rufescent, and back 
streaked or mottled with rufous or cinnamomeous. 
@ Mr. Gregory Mathews (Birds of Australia, ii, 1913, 496) recognizes eight forms of 
this genus, referred to three species, as follows: 
1. Megalestris skua skua. (Catharacta skua skua Mathews, Birds Australia, ii, 
pt. 5, Jan. 31, 1913, 496.—North Atlantic Ocean; Hudson Strait.) 
2. Megalestris skua antarctica. (Catharacta skua antarctica Mathews, Birds Aus- 
tralia, ii, pt. 5, Jan. 31, 1918, 496.—Falkland Islands, breeding; Gough 
Island.) ; 
