INTRODUCTION. XV 



A. PASSERES.* Hallux invariably present, completely incumbent, sepa- 

 rately movable by specialization of the flexor hallucis longus, with enlarged 

 base and its claw larger than that of the middle digit. Neither second nor 

 fourth toe versatile; joints of toes always 2, 3, 4, 5, from first to fourth. 

 Wing-coverts comparatively short and few ; with the exception of the least 

 coverts upon the plica alaris, arranged in only two series, the greater of 

 which does not reach beyond the middle of the secondary remiges." Rec- 

 trices twelve (with rare anomalous exceptions). Musical apparatus present 

 in greater or less development and complexity. Palate segithognathous. 

 Sternum of one particular mould, single-notched. Carotid single (sinistra). 

 Nature highly altricial and psilopsedic. 



a. Oscines.^ Sides of the tarsus covered in most or all of their extent 

 with two undivided horny plates meeting behind in a sharp ridge (ex- 

 cept in Alaudidce ; one of the plates imperfectly divided in a few other 

 forms). Musical apparatus highly developed, consisting of several dis- 

 tinct pairs of syringeal muscles. Primaries nine only, or ten with the 

 first frequently spurious, rarely over two thirds the length of the 

 longest, never equalling the longest. 



b. Clamatores.* Sides of the tarsus covered Avith divided plates or 

 scales variously arranged, its hinder edge blunt. Musical ajjparatus 

 weak and imperfect, of few or incompletely distinguished syringeal 

 muscles (as far as known). Primaries ten with rare exceptions, the 

 first usually equalling or exceeding the rest. 



B. PICARI.ai.'^ Hallux inconsiderable, weak or Avanting, not always in- 

 cumbent, not separately movable by distinction of a special muscle, its claw 

 not longer than that of the middle toe unless of exceptional shape (e. g. Ce7i- 

 tropus). Second or fourth toe frequently versatile ; third and fourth fre- 

 quently with decreased number of joints. Wing-coverts for the most part 

 larger and in more numerous series than in Passeres, the greater series 

 reaching beyond the middle of the secondary quills (except in many Pici 

 and some others). Rectrices commonly ten (eight to twelve). Primaries 

 always ten, the first only exceptionally short (as in Pici). Musical appara- 

 tus wanting, or consisting of a muscular mass, or of not more than three 

 pairs of syringeal muscles. Palate desmognathous or tegithognathous. 

 Sternum of non -passerine character, its posterior border entire or doubly 

 notched or fenestrate. Carotid single or double. Nature completely al- 

 tricial, but young- sometimes hatched with down* (e. g. Cap?imulgidce). 



jjossess in common one single character not also to be found in other groups, nor is the colloca- 

 tion of their characters peculiar. 



1 Corresponding closely with the Linnaean and earlier Sundevallian acceptation of the term. 

 Equivalent to the later Oscincs of Sundevall. 



2 As remarked by Sundevall, exceptions to the diagnostic pertinence of these two characters 

 of hind claw and wing-coverts taken together are scarcely found. For, in those non-passerine 

 birds, as Jtcqitores and some Hcrodioncs, in which the claw is enlarged, the wing-coverts are 

 otherwise disposed ; and similarly when, as in many Pici and elsewhere, the coverts are of a pas- 

 serine character, the feet are higldy diverse. 



^ Laminiplantares of Sundevall plus Alaudidce. 



* Scutelliplantares of Sundevall minus Alaudidce. 



^ Nearly equivalent to the Linnsean Piece. Equal to the late (1873) Volucres of Sundevall. 



® A polymorphic group, perfectly distinguished from Passeres by the above characters in wliich, 

 for the most part, it approximates to one or another of the following lower groups, from which, 

 severally, it is distingiiished by the inapplicability of the characters noted beyond. My divisions 



