178 SHOULDER-GIRDLE AND BREAST-BONE. 



intensified in the Trochili. The scapula is long and ensiform ; the coracoid is short and stout ; 

 the furcula is U-shaped, strong, and has a small inter-clavicle. The Sternum is longer than in 

 the Swift, and widens more suddenly towards the end. I see no fenestrse; but in some 

 kinds the body of the bone is much swollen on each side of the middle line, which is a 

 deep groove punched full of air-holes. There is a thick upper " rostrum," as in the Swift ; the 

 coracoid grooves lie on each side of this process, and the costal processes are still smaller than in 

 those Birds; the keel, in some species at least, is considerably larger, relatively, than in Cypselus ; 

 it reaches the end of the bone, which ends below the tail, as in the Tinamou, a Bird which can 

 lay but little claim to relationship with these Insect-like Vertebrata. 



Sub-ordo" PASSERINE." 

 Examples. Linota cannabina, Linn. ; Turdus merula, Linn. ; Corvus monedula, Linn. 



In this group I would include the thick- and thin-billed songsters (Fringillinge, and the 

 allied Sub-families ; Sylviinse, and their congeners) ; the Crows ( Corvinse including the 

 old-world and Australian types, and the Birds of Paradise) ; Shrikes (Laniinse) ; Flycatchers 

 (Muscicapinae, Tyranninae) ; Swallows (Hirundinae) ; Creepers (Certhiinse) ; Tits (Parinse), &c. 

 A great host this, yet wonderfully uniform in osteological structure, being varied in the 

 gentlest manner; and the cases in which the typical character are either in excess or aborted 

 very few. It is difficult to believe that this group is not equal in a systematic sense to 

 what I have just spoken of as the Picariae ; yet this latter group is polymorphic in a very 

 great degree, and is most strongly in contrast with the homomorphic Passerinae. If the 

 Picariae were treated as three distinct orders, namely, Zygodactyli, Syndactyli, and Hetero- 

 dactyli, even then the comparison of the Passerines with either of these would not hold ; for 

 there is no such uniformity in any one of these lesser groups, such as is seen in the Passerine 

 Sub-order. The only group equally homomorphic is the Psittaciue Family ; but this is only one 

 amongst many members of the Picariae. The Gallinaceae might be compared with the Passerinee, 

 were it not for the Columbine, Hemipodiine, and Pterocline groups; to say nothing of the 

 semi-strut hious Tinamous. So that we see half of the Gallinaceous Birds diverge con- 

 siderably from, or have not arrived at, the typical condition. I shall give an account of the 

 development of the Shoulder-girdle and Sternum in a typical Passerine Bird, namely, the Brown 

 Linnet (Linota cannabina} ; in the Blackbird (Turdus merula) ; and in the Daw (Corvus monedula). 



In Linota, when two fifths of the incubating period have elapsed, the coraco-scapular 

 structures appear as shown in Plate XV, fig. 1 2 (magnified twenty diameters) : this view is from the 

 inside. The scapula (sc.) is a broad falchion-like cartilage ; out-turned, broad, and then pointed 

 in its supra-scapular region (s. sc.) : at its base it is separated from the coracoid (cr.) by a sharply 

 defined, undulating, transverse cleft (s. sc.), which passes through the middle of the glenoid 

 concavity (gl.) to the emarginate meso-scapular projection ("acromion," m. sc.). A delicate 







i Professor Huxley (' Proc. Zool. Soc./ 1867, p. 450) proposes to add the Goatsuckers, Swifts, 

 and perhaps also the Humming Birds, to the Passerine group, and to call the whole sub-order 

 " (Egithognathae :" it is a great relief to my mind to have the Swallows and the Swifts thus made to 

 " atone together." 



