706 BULLETIN 60, UNITED STATES NATIONAL MUSEUM. 



Genus PLAUTUS Gunnerus. 



Flotus (not of Linnaeus, 1766) Gunnerus, Trondheimske Selsk. Skrifter, i, 1761, 



263. (Type, by monotypy, Plofus eller Plautus columbarius Gunnerus= 



Alca alle Linnseiis.) 

 Plaufus Gunnerus, Trondheimske Selsk. Skrifter, i, 1761, 263, pi. 6. (Type, by 



monotypy, Plotus eller Plautus columbarius Gunnerus =^Zca alle Linnaeus.) 

 Alle Link, Beschr. Nat. Samml. Univ. Rostock, i. 1806. 17. (Type, by monotypy, 



A. nigricans Link=.4Zca alle Linnaeus.) 

 Mergulus Vieillot, Analyse, 1816, 67. (Type, by original designation, Petit 



plongeo7i noir et blanc Edwards=J.Zca alle Linnaeus.) 



Small Alcidse (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; culm en 

 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 wmg, shghtly 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 

 Zeml^^a, southward in winter to Atlantic coast of United States, 

 Azores, and Canary Islands. (Monotypic.) 



