66 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
Small Formicariide resembling Myrmotherula but differmg in 
relatively much longer tail (much more than half to more than two- 
thirds as long as wing), much stouter and relatively shorter and less 
depressed bill, the adult males neither streaked nor plain gray or 
slaty. 
Bill decidedly shorter than head, rather stout, not depressed 
basally, its width at frontal antic about equal to or very little greater 
than its depth at same point and equal to less to slightly more than 
half the distance from nostril to tip of maxilla; culmen distinctly 
and rather sharply ridged, straight or nearly so for most of its length, 
rather strongly and abruptly decurved terminally, the tip of maxilla 
minutely but distinctly uncinate; tomium nearly straight, that of 
maxilla distinctly, that of mandible slightly notched subterminally; 
gonys faintly convex (more decidedly so basally). Nostril exposed, 
posteriorly nearly (sometimes quite) in contact with feathering of 
latero-frontal antie, roundish or broadly oval, margined for basal 
half by the membraneous cover of nasal fosse (this sometimes extend- 
ing along upper margin as a narrow “‘operculum’’), and with a con- 
spicuous internal tubercle. Rictal bristles present but minute 
(practically obsolete); feathers of chin, malar antiz, and lores with 
slender terminal sete. Wing moderate, with longest primaries dis- 
tinctly longer than secondaries; sixth and seventh, or fifth, sixth, 
and seventh, primaries longest, the tenth (outermost) slightly more 
than one-half to nearly two-thirds as long as the longest, the ninth 
about as long as secondaries or a little shorter. Tail much more 
than half to more than two-thirds as long as wing, much rounded, 
the rectrices (12) moderately broad to rather narrow, rounded ter- 
minally. Tarsus decidedly longer than exposed culmen, less than 
one-third as long as wing (except in WM. ornata), the acrotarsium 
distinctly scutellate, the planta tarsi usually fused (at least in part) 
or with the scutella somewhat indefinite as to form and arrangement 
(with a general tendency toward two longitudinal series); middle 
toe, with claw, decidedly shorter than tarsus; outer toe, without 
claw, reaching to beyond middle of subterminal phalanx of middle 
toe, the inner toe slightly shorter; hallux about as long as inner toe 
but much stouter; basal phalanx of middle toe wholly united to 
outer toe, for about half its length to inner toe; claws moderate in 
size and curvature, that of the hallux decidedly shorter than the 
digit. Plumage soft, lax, and blended, that of rump and flanks 
much elongated and fluffy; feathers of pileum not elongated. 
Coloration.°-—Adult males plain gray or slate color above, the 
wings black, spotted with white, the tail black with white tip to 
@ Not having been able to examine much the greater number of the species referred 
by Dr. Sclater to Myrmotherula (see note on page 62) I am not able to define the 
full range of variation as to coloration in this group, 
