20 NORTH AMErdCAN BIRDS. 



Order LONGIPENNES.— The Long-winged 



Swimmers, ci'^'g^ i-) 



Families. 



a'. Bill with the lower mandible iiol longer than the upper, and not excessively 

 compressed. 

 6'. 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 culmeu, its edge overhanging the nostril. 



Stercorariidse. (Page 20.) 

 61 Covering of upper mandible consisting of a single piece, through which the 



nostrils are pierced Laridse. (Page 23.) 



fll Bill with lower mandible much longer than the upper, both mandibles excessively 

 compressed, like a thin knife-blade, for terminal portion. 



Rynchopidae. (Page 48.) 



Family STERCORARIIDSE.— The Skuas and Jaegers. (Pago 20.) 



Genera. 



rt'. 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 ; tai-sus shorter than middle toe with claw ; tail short, nearly 

 even, the middle pair of feathers scarcely projecting beyond tlio rest ; color 

 dull brownish, sometimes streaked (never barred) with paler, the base of the 

 primaries with a whitish patch Megalestris. (Pago 20.) 



rt'. 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 reetrices in tho adult projecting far bej-ond 

 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 Bonaparte. (Page 20, pi. YIL, fig. 1.) 



Species. 



Common Characters. — 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. 



