692 BULLETIISr 50, UNITED STATES NATIONAL MUSEUM. 



polj^morphio one and without dou])t requires subdivision into two or 

 more; but the species are ver}" numerous and the working* out of the 

 prolilem would require far more time than is at my disposal for the 

 purpose. 



The relativel}^ few American forms belong to two groups, one of 

 which (Polioptilime), consisting of a single genus, is peculiar to Amer- 

 ica, while the other includes two genera, one of which {Regulus) is 

 circumpolar and the other {Acantliopneuste) Paliearctic but included in 

 the American fauna on account of the occurrence of a single Siberian 

 species in western Alaska. Limiting a description of the family char- 

 acters to the American forms, they ma}' be given as follows: 



Bill much shorter than head, slender, rather broad and depressed at 

 base, where its width is decidedly less than half the length of exposed 

 culmen but greater than its depth; culmen distinctly, almost sharply, 

 ridged (at least basally), straight to near tip of maxilla, where gradu- 

 ally but decidedly decurved; commissure straight or nearl}^ so, the 

 maxillary tomium distinctly notched immediately behind the dis- 

 tinctl}' but minutely uncinate tip of the maxilla; gon3's slighth' convex 

 or nearly straight, ascending terminally, its base anterior to nostril or 

 at least not posterior to anterior end of nostril. Nostril at least partly 

 exposed, longitudinal, operculate, sometimes partly covered by 

 antrorse bristly plumules of the frontal antias. Rictal bristles distinct. 

 Wings rather long but with rounded tip; eighth, seventh, and sixth, or 

 eighth to fifth, primaries longest, the ninth longer than third, some- 

 times longer than fifth, the tenth much less than half as long as ninth, 

 usually less than one-third as long, often scarcely longer than primary 

 coverts. Tail variable as to relative length but usually decidedly 

 shorter than wing (longer only in subfamily Polioptilinse), even, emar- 

 ginate, slightly double-rounded, or (in Polioptilina?) much rounded, the 

 rectrices usually broad and rounded at tip but sometimes (in genera 

 with shorter and emarginate tail) somewhat pointed. Tarsus much 

 longer than middle toe with claw, often nearly (sometimes quite) twice 

 as long as middle toe without claw, the acrotarsium booted or scutel- 

 late, or intermediate with respect to this character; lateral toes about 

 equal in length (the outer sometimes slightly longer than inner), their 

 claws, especially the outer, sometimes reaching to or beyond base of 

 middle claw but usually falling short; hallux about as long as lateral 

 toes but much stouter, its strongly arched claw shorter than the digit; 

 basal phalanx of middle toe adherent for most of its length to outer 

 toe, for about half its length to inner toe. 



Coloration.- — Above plain olive, olive-green, brown, or bluish gray 

 (wings and tail, sometimes crown also, black and lateral rectrices partly 

 white in Polioptila^ the crown with a ^^ellow, orange, or red patch 

 in Beguhis)\ under parts whitish, yellowish, or pale grayish; sexes 



