20 NORTH AMERICAN BIRDS. 
Oxi LONGIPENNES.—Tue Lone-wincep 
SWIMMERS. (Page 1.) 
Families. 
a. Bill with the lower mandible not longer than the upper, and not excessively 
compressed. 
b.. Covering of the upper mandible composed of three distinct pieces—a ter- 
minal unguis, or hook, a lateral piece, and a cere-like piece saddled upon 
the culmen, its edge overhanging the nostril. 
Stercorariide. (Page 20.) 
b*. Covering of upper mandible consisting of a single piece, through which the 
nostrils are PierCed..........ccccceseereeeeccesseeeeeneeeees Laridz. (Page 23.) 
a, Bill with lower mandible much longer than the upper, both mandibles excessively 
compressed, like a thin knife-blade, for terminal portion. 
Rynchopidz. (Page 48.) 
Famity STERCORARIIDZE.—Tue Sxuas anp JAEGERS. (Page 20.) 
Genera. 
a‘. Size large (in bulk equal to the largest gulls), and form robust; depth of bill at 
base equal to not less than half the length of the upper mandible, measured 
along the side; tarsus shorter than middle toe with claw; tail short, nearly 
even, the middle pair of feathers scarcely projecting beyond the rest; color 
dull brownish, sometimes streaked (never barred) with paler, the base of the 
primaries with a whitish patch ..........cssccesssecsees Megalestris. (Page 20.) 
a’, Size medium or rather small (not exceeding the medium-sized gulls), and form 
more slender and graceful; depth of bill at base less than half the length of 
the upper mandible, measured along the side; tarsus decidedly longer than 
middle toe with claw; middle rectrices in the adult projecting far beyond 
the rest; color plain slaty or dusky, often varied with white or yellowish, 
in the adult, dusky barred with paler in young ; no white at base of primaries. 
Stercorarius. (Page 21.) 
Genus MEGALESTRIS Bownaparre. (Page 20, pl. VIL, fig. 1.) 
Species. 
Common Cuaracters.—General color nearly uniform grayish brown or sooty, 
usually indistinctly streaked with light rusty, or cinnamon, especially around neck 
and on back; quills whitish at base. Eggs olive, spotted with brown. 
