706 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
Genus PLAUTUS Gunnerus. 
Plotus (not of Linneus, 1766) Gunnerus, Trondheimske Selek. Skrifter, i, 1761, 
263. (Type, by monotypy, Plotus eller Plautus columbarius Gunnerus= 
Alca alle Linneus.) 
Plautus GuNNERUS, Trondheimske Selsk. Skrifter, i, 1761, 263, pl.6. (Type, by 
monotypy, Plotus eller Plautus columbarius Gunnerus=Alca alle Linnzus.) 
Alle Linx, Beschr. Nat. Samml. Univ. Rostock, i, 1806,17. (Type, by monotypy, 
A, nigricans Link=Alca alle Linneus.) 
Mergulus Visrutor, Analyse, 1816, 67. (Type, by original designation, Petit 
plongeon noir et blanc Edwards=Alca alle Linnzus.) 
Small Alcide (wing 106-122 mm.) with short, thick galliform bill, 
secondaries tipped with white, and under parts of body white. 
Bill short and thick, its depth at base about equal to its width at 
same point and to the distance from nostril to tip of maxilla; culmen 
strongly curved from near base, the tip of maxilla distinctly uncinate; 
gonys straight, ascending terminally, exceedingly short, its length 
equal to less than half the distance from nostril to tip of maxilla; 
maxillary tomium slightly but distinctly concave, the mandibular 
tomium correspondingly convex, both notched subterminally; cor- 
neous sheath of mandibular rami gradually contracted in width from 
base of gonys to rictus; nasal fossa semicircular, the lower third 
(approximately) occupied by the longitudinally ovate or broadly 
elliptical nostril the latter overhung by a rather prominent, slightly 
arched, corneous operculum and posteriorly in contact with the 
dense, velvety loral feathering. Longest primaries exceeding distal 
secondaries by half the length of wing: Tail less than one-third as 
long as wing, slightly rounded or double-rounded (the middle pair of 
rectrices decidedly longer than outer pair), the rectrices slightly nar- 
rowed at tips, 12 in number. Tarsus about as long as distance from 
anterior end of nasal fossa to anterior angle of eye, the acrotarsium 
continuously and regularly transversely scutellate; middle toe, with- 
out claw, decidedly longer than tarsus, the outer toe very slightly 
shorter, the inner toe very slightly shorter than first two phalanges 
of middle toe. 
Plumage and coloration.—Plumage of head (especially the anterior 
portion) very soft, dense, and velvety. Upper parts black, the 
scapulars streaked with white, the secondaries narrowly tipped with 
the same; under parts white, the flanks streaked with black; in sum- 
mer, head, neck, and chest uniform blackish brown or fuscous; in 
winter, the under side of head and neck and chest mostly white. 
Range.—Arctic Ocean, from western side of Baffin Bay to Novaya 
Zemlya, southward in winter to Atlantic coast of United States, 
Azores, and Canary Islands. (Monotypic.) 
