714 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
and shallow transverse, slightly curved (distally convex) grooves, the 
mandible usually with one or two similar but more vertical grooves. 
Wing moderate, the longest primary (outermost) exceeding distal 
secondaries by more than half the length of wing. Tail about two- 
fifths as long as wing, graduated for more than one-third its length, 
the middle rectrices obtusely pointed; rectrices 12. Tarsus about 
as long as chord of exposed culmen, the acrotarsium continuously 
transversely scutellate; middle toe, without claw, much longer than 
tarsus, the outer toe as long as middle toe (but its claw smaller), the 
inner toe (without claw) as long as first two phalanges of middle toe, 
Plumage and coloration.—Plumage of head, especially the anterior 
portion, short, very dense, and soft or velvety. Upper parts sooty 
blaek, the secondaries narrowly tipped with white; under parts 
immaculate white. In breeding season, the head and upper neck 
dark sooty brown (deepening into blackish on pileum and hindneck), 
relieved by a white line from eye to base of culmen. 
Range.—Coasts and islands of the northern Atlantic Ocean, south 
in winter to Atlantic coast of United States, Mediterranean Sea, etc. 
(Monotypic.) , 
ALCA TORDA Linneus. 
RAZOR-BILLED AUK. 
Adults in breeding season (sexes alike)—Head and upper neck 
plain dark brown (bright clove brown or deep olive-brown), becoming 
much darker on pileum and gradually darkening into slate-black on 
hindneck and rest of upper parts; secondaries narrowly but sharply 
tipped with white; a narrow white line extending from anterior angle 
of eye to near base of culmen; under parts, including axillars and 
under wing-coverts, immaculate white, this extending forward to and 
including the lower foreneck; bill black, with one or more of the 
transverse grooves whitish; interior of mouth yellow; iris dark 
brown; legs and feet dull black. 
Winter plumage.—Whole under portion of head and neck and 
space behind auricular region white; no white line between bill and 
eye; bill without the basal lamina; otherwise as in summer. 
Young.—Similar in coloration to the winter adult, but bill smaller 
and without grooves. 
Downy young.—Head, neck, and under parts plain dull whitish, 
usually more or less tinged above with brownish buff; back, rump, 
and flanks varying from pale brownish buff, more decidedly brownish 
posteriorly, to dark sooty brown, the down dusky immediately beneath 
the surface; posterior and lateral under parts more or less tinged 
with brownish buff or sooty brownish. 
