THE DUSKY SHEARWATER. 
101 
margins, the outer toe slightly longer than the third. Claws small, slightly 
arched, compressed, obtuse. 
Plumage soft, full ; the feathers rounded, those of the back and wings 
rather compact. Wings long; primaries tapering, rounded, the first longest, 
the rest rapidly graduated; secondaries of moderate length, rounded. Tail 
rather short, much rounded, of twelve feathers. 
Bill light blue, the tips black, mouth light blue. Edges of eyelids light 
blue, iris bluish-black. Outside of tarsus and toes indigo-black, inside and 
webs pale yellowish-flesh-colour ; claws bluish-black. The upper parts are 
sooty -black, the lower pure white. 
Length to end of tail 11 inches, to end of wings 10J, to end of claws IK; 
extent of wings 26£; bill along the back lyV, along the edge of lower man- 
dible II; tarsus 1J; outer toe 2, its claw f-|-. 
Genus V.— THALASSIDROMA, Vigors. PETREL. 
Bill shorter than the head, slender, as high as broad at the base, extremely 
compressed at the end ; upper mandible with the nostrils dorsal forming a 
tube on its ridge at the base, on which the dorsal line is concave and ascend- 
ing, then abrupt, afterwards, for a short space, straight, and lastly decurved, 
the sides separated by a groove, convex, the edges sharp and inflected, the 
tip decurved, slender, acute ; lower mandible with the angle rather long, 
narrow, and pointed, the dorsal line beyond it decurved, the sides erect, the 
edges sharp, the tip decurved, acute. Head of moderate size, rounded 
above ; neck short.; body rather slender. Feet rather long, slender ; tibia 
bare at its lower part; tarsus slender, reticulate; hind toe minute, with a 
conical deflected claw; anterior toes of moderate length, slender, scutellate, 
webbed, the third and fourth about equal. C.'aws slender, arched, com- 
pressed, acute. Plumage very soft and blended, the feathers distinct only 
on the wings, which are very long, with the primaries a little incurved 
toward the end, the second longest, the first and fourth about equal ; tail 
