PROCELLARIID^ — PBOCELLARIINJE : PETRELS. 
781 
converging to narrow tip ; less than half as long as head, about half the tarsus. Wings 
folding beyond tail ; 2d primary longest, 3d little shorter, 1st less than 4th. Tibia brietiy 
bare below; tarsus equal to middle toe and claw; claws compressed, curved, acute. Tail 
rounded or nearly square, with broad feathers ; under tail-coverts very ample. Several species, 
distinguished by shape of tail from those of the preceding or following genus. 
833. P. pela'gica. (Gr. TreXayi/cdj, jjelagikos, oceanic.) Stormy Petrel. Above, glossy brown- 
ish-black, below more fuliginous ; upper tail-coverts M^iite, with black tips ] v/hite streaking 
on crissum, and usually white touches under the wings. Bill and feet black ; no yellow on 
webs. Size of the last; wing about 4.50. Common (f) oflF the Atlantic Coast; not known to 
breed on our side. This is the rarest of the three little black white-rumped " Mother Carey's 
chickens " of our Atlantic Coast, easily distinguished by its short legs and square tail; Leach's, 
the most numerous, is also short-legged, but larger and forked-tailed ; Wilson's is interme- 
diate, with square tail, but very long stilt-like legs, flat claws, and a yellow spot on the webs. 
327. CYMOCHORE'A. (Gr. /cC/xa, huma, a- billow; x^P^^y ^ dancing.) SoOTY Fork-tail 
Petrels. Bill much shorter than head, about f as long as tarsus, rather stout, as high 
as or higher than wide at base, the hook strong and acute ; nasal tube less than half as long 
as culmen. Wings moderately long, folding little beyond tail; 2d primary longest; 1st longer 
than 4th. Tail very long, deeply forked, the feathers all broad, obtusely rounded. Legs 
short; tibia little bare below; tarsus equal to middle toe and claw, or slightly longer. Of 
rather large size (for this group) and robust form. Color fuliginous, uuicolor or nearly so. 
Three or four species are known. 
Analysis of Species. 
Upper tail-coverts white. 
General plumage sooty-brown leucorrhoa 823 
No white anywhere. 
Sooty-brown; large ; wing 6.75; tail 4.00, forked 1.00 or more melcena 824 
Sooty-gray; small; wing 5.00; tail 3.25, forked about 0.50 homochroa 825 
823. C. leucor/rhoa. (G.'KevKos, leiikos, white] oppos, orhros, rumip. Fig. 525.) Leach's Petrel. 
White-rumped Petrel. Coloration as in the last species, with white upper tail-coverts, 
forming a conspicuous mark; but apt to be lighter — rather 
of a grayish or even ashy hue on some parts ; but easily 
recognized, whatever the shade of color. Bill and feet 
black; iris brown. Length about 8.00; extent 17.50; 
wing 6.00-6.50; tail 3.00-3.50, forked about 0.75; tarsus 
1.00; middle toe and claw the same; bill 0.67- N. Am., 
both coasts, and W. coast of Europe. Abundant on our 
N. Atlantic coast, breeding from New England northward. 
Nest in burrows in the ground; egg single, white. 
824. C. melae'na. (Gr. p.eXaiva, melaina, black. Fig. 526.) 
Black Petrel. Form of the last very nearly; bill more yig. 525. -Leach's Petrel, much re- 
robust ; tarsus a little longer than middle toe and claw. No duced. (From Tenney, after Audubon.) 
white anywhere. Plumage sooty brownish -black, darkest above and on head, more smoky- 
brown on under parts, grayer on wing-coverts, quite black on wing- and tail-feathers ; bill and 
feet black ; iris brown. Length 9.00 ; extent 18.50 ; " wing 6.75 ; tail 4.00, forked 1.20 ; tibia 
bare 0.50; tarsus 1.25; middle toe and claw 1.10 ; bill 0.60; gape 0.95; height or width at 
base 0.25 ; nasal tubes 0.30. Cape St. Lucas, L. Cala. ; a rare and little known species. 
825. C. homo'chroa. (Gr. o/nos, omos, like, equal ; xP^^i chroa, color.) Somewhat like the last ; 
smaller, with short, weak, compressed bill, and tarsus no longer than middle toe and claw. 
No white anywhere. Plumage duU plumbeous or slaty-blackish, more smoky-brownish on 
lower parts, lighter grayish-brown on greater wing-coverts ; wings and tail black. 2d primary 
