INTRODUCTION. XXXVII 



lower part of the tibia bare for some distance ; tarsi tolerably strong ; three 

 toes in front entirely webbed, hind toe small, elevated (p. 657). 



Rhodostethia, Mac gill iv ray. — Bill very short, rather slender ; the upper man- 

 dible decurved towards the tip, the lower mandible narrow. Wings long and 

 pointed, the first quill the longest. Tail cuneate, the central feathers much 

 longer than the lateral. Legs rather short, the tibia bare for a short distance ; 

 tarsus anteriorly scutellated, rough posteriorly ; hind toe very distinct, with 

 a large curved claw ; the three anterior toes entirely webbed ; claws rather 

 large, and curved (p. 659). 



Larus, Liuimus.—V^\\\ of moderate length, strong, hard, compressed, cutting, 

 slightly decurved towards the point, lower mandible shorter than the upper, 

 the symphysis angular and prominent. Nostrils lateral, near the middle of the 

 beak, pierced longitudinally, pervious. Wings long, the first and second 

 quills varying slightly in their relative length, but nearly equal. Tail square 

 at the end. Legs moderately slender, lower part of the tibite naked, tarsus 

 rather long ; three toes in front entirely palmated, the hind toe free, short, 

 but not rudimentary, articulated high upon the tarsus above the line of the 

 other toes (p. 661). 



RiSSA, Stephens.— ^\\\ rather short and stout, the upper mandible considerably 

 decurved to the tip, the lower mandible compressed. Nostrils median, linear, 

 oblong. Wings long, pointed, the first primary slightly exceeding the second. 

 Tail slightly but perceptibly forked in the young, nearly square in the adult; 

 tarsus very short in proportion to the foot ; hind toe minute and usually 

 obsolete ; claws rather small, slightly curved (p. 683). 



Pagophila, Kaitp. — Bill shorter than the head, robust, compressed, straight, the 

 upper mandible decurved towards the tip, lower mandible narrower. Nostrils 

 basal, linear, oblong, wider in front, covered above and behind with a sloping 

 thin-edged plate. Wings long, pointed, the first quill longest. Tail rather 

 long, slightly graduated. Legs short, bare for a short distance above the 

 tibia ; tarsi broadly scutellated in front, and minutely at the sides and back ; 

 interdigital membranes emarginated and serrated ; claws strong and curved ; 

 hind toe furnished with a large claw, and connected on the inside with the 

 tarsus by a well-defined web (p. 6S5). 



Family STERCORARIID.E. 



Bill with a cere ; tip of the upper mandible hooked ; sternum with only one 

 notch on each side of the posterior margin ; creca much larger than in Laridce ; 

 toes fully webbed, furnished with large, strong, hooked and sharp claws. 



Megalestrls, Bonapa7-te. — Size larger, form robust ; length of the bill at the 

 exposed base nearly equal to the length of the cere ; tail short, the central 

 pair of feathers projecting about half an inch (p. 687). 



Stercorarius, Bi-isson. — Size smaller, form more slender ; depth of the bill at 

 the exposed base decidedly less than the length of the cere ; the central pair 

 of tail-feathers projecting three inches or more in adults (p. 689). 



