INTRODUCTION. XXXVii 
lower part of the tibia bare for some distance ; tarsi tulerably strong ; three 
toes in front entirely webbed, hind toe small, elevated (p. 657). 
RuoDosretHia, Afacgillivray.—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, Linneus.—Bill 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 tibiz 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.—Bill 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, Kazp.—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. Winys 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. 685). 
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 ; caeca much larger than in Laride ; 
toes fully webbed, furnished with large, strong, hooked and sharp claws. 
MEGALESTRIS, Bonaparte.—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, Brisson.—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). 
