702 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
toes fully webbed and armed with strongly curved and sharp, though 
not large, claws, the hallux always absent, the nostrils not overhung by 
membrane, and the lores always densely feathered. The bill is 
exceedingly variable in form, often quite unique in structure, but is 
never acuminate. The wing is moderately large or rather small, with 
relatively short secondaries, the longest primaries (usually the outer- 
most only but sometimes the two outermost, the second always being 
nearly as long as the first) exceeding the distal secondaries by appoxi- 
mately half (sometimes a little less, sometimes more than half) the 
length of the closed wing. The primaries are always more or less 
bowed, and their coverts very large, covering nearly their basal half, 
The tail is always short, the rectrices normal and 12 to 18 in number. 
The tarsus is usually much shorter than the middle toe without claw 
(onger only in Synthliboramphus and Endomychura), much com- 
pressed, wholly reticulate or (in a few genera) with more or less dis- 
tinct transverse scutella on lower or inner portion of acrotarsium, 
rarely with a continuous series. The outer toe (without claw) is 
always very nearly if not quite as long as the middle toe (without 
claw), the inner toe as long as the first two phalanges of the middle 
toe. In one genus (Synthliboramphus) the outer toe is longest and 
the inner toe longer than first two phalanges of middle toe. 
Peculiar to the seas and coasts of the more northern parts of the 
northern hemisphere, they represent there the Penguins of the 
Antarctic seas. With one exception, however, they possess the power 
of flight, usually to a marked degree; but the Great Auk (Pinguinus 
impennis), extinct since 1844, was quite unable to fly. The flight, 
however, while rapid and strong, is direct and not buoyant as it is in 
the Lari. 
The family is represented by about 15 genera and 28 species, all of 
the former and all but four of the latter occurring in North America. 
They nest in cavities among the rocks, usually on the face of cliffs, 
though some genera lay their eggs in burrows beneath the surface of 
the ground, like most of the Procellariide (Petrels). The single egg 
is variable in form (which may be either pyriform, ovate, or elongate- 
ovate), even more so in color. The molt is said to be semi-annual. 
KEY TO THE GENERA OF ALCID&, 
a. Bill gallinaceous in form (short and thick, with distinctly curved culmen), its 
width at posterior end of nostrils equal to its depth at same point, the gonys 
exceedingly short (less than one-third the distance from gonydeal angle to 
rictus); only 1 carotid artery. (Plautex)......... Se ena Plautus (p. 706). 
aa, Bill not gallinaceous in form; if short and thick, its width at posterior end of 
nostrils decidedly less than its depth at same point; gonys relatively longer, 
always longer than one-third the distance from gonydeal angle to rictus; 2 
carotid arteries. 
