22 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



rj. Nostrils wholly exposed, circular, in anterior portion of (listinct nasal 

 fossje; maxilla with culmen gradually curved terminally, tip not 

 distinctly uncinate, and with indistinct subterminal tomial notch 

 and tooth; tail decidedly shorter than wing, even; tenth primary 

 much less than half as long as ninth; under parts conspicuously 



streaked Dulidae. 



gg. Nostrils partly hidden liy liristly loral feathers, longitudinally oval, 

 bored directly into the horny rhinotheca; maxilla with culmen 

 abruptly curved terminally, tip distinctly uncinate, and with 

 subterminal tomial notch and tooth distinct; tail nearly as long as 

 • wing, sometimes longer, much rounded or graduated; tenth pri- 

 mary half as long as ninth; under parts not streaked Laniidae. 



//". Bill more slender (depth at nostrils less than half as long as exposed 

 culmen); the culmen not strongly curved, or else (Corvidpe, part) 

 the nostrils circular, without superior membrane or operculum. 

 g. Nostrils covered (at least partly) by tuft of antrorse plumules, or else 

 (Corvidfe, part) exposed, circular, without superior membrane or 

 operculum, or else (Corvidas, part) longitudinal, with superior 

 operculum, the bill elongate-conical, with broad and depressed 

 mesorhinium, and the tenth primary half as long as ninth. 

 h. Hallux not distinctly, if at all, longer than longest lateral toe, its 

 claw not conspicuously large; outer toe not conspicuously, if at all, 

 longer than inner toe; tarsus equal to or longer than middle toe, 

 with claw. 



i. Larger ( wing more than 102 mm. ) ' Corvidae. 



ii. Smaller ( wing less than 89 mm ) ' Paridae. 



hh. Hallux distinctly longer than longest lateral toe (the outer), its 

 claw conspicuously large; outer toe conspicuously longer than 



inner; tarsus shorter than middle toe with claw Sittidae. 



gg. Nostrils exposed, but not circular and without superior membrane 



or operculum, nor bill elongate-conical with broad and depressed 



mesorhinium, or if the latter the outermost (tenth) primary less 



than half as long as primary coverts (Sturnidae); or if covered, the 



covering a single plumule and the acrotarsium booted (Sylviidfe, 



part). 



li. Hallux distinctly longer than lateral toes; basal phalanx of middle 



toe adherent for whole of its length to both lateral toes. 



i. Rectrices rigid, with tips acuminate; claw of hallux as long as or 



longer than its digit Certhiidae. 



ii. Rectrices soft, with tips normally broad and rounded; claw of 



hallux shorter than its digit Troglodytidae. 



hli. Hallux not distinctly if at all longer than lateral toes; basal pha- 

 lanx of middle toe free for most if not all of its length from inner 

 toe, and (approximately) for half its length from outer toe 



i. Acrotarsium booted, at least on outer side. 



U must confess my inability to discover any external structural characters which 

 will serve to distinguish these two groups as a whole. The Garruliufie and typical 

 Paridfe seem to differ externally only in size, every one of the supposed distinctive 

 characters (as alleged peculiar modification of the planta tarsi in Corvidfe, differences 

 in proportions of primaries, etc.) breaking down when all the genera are compared. 

 The variations of form and in external details in the group called Corvidse are so 

 great that its diagnosis is very difficult. 



