1906.] OF THE TRACHEOPHONE PASSERES. 149 



The autei'ior lateral process in Hylactes is of enormous length, 

 projecting far beyond the level of the end of the spina externa : 

 along its free outer border are placed the articular surfaces for 

 the ribs. The spina externa is moderately long and slightly 

 pointed. The carina sterna is small. 



The sterna of all the remaining genera here discussed are of 

 the typical Passerine type, and present but few structuiul 

 variations : these, however-, I will briefly indicate. 



Except in the case of the Philepittidee, all these sterna agree 

 in having a forked spina externa — in Philepitta it is imforked 

 and small, — a moderately long anterior-lateral pi-ocess to which 

 alone the sternal ribs articulate, and but a single notch along 

 the posterior free border, the processus intermedius being 

 wanting. In the climbing forms of the Formicariidse and Den- 

 drocolaptidse the sternal plate is long and narrow, and the keel 

 shallow. In the Philepittidte and Pipridte the spina externa is 

 pierced on its doi'sal aspect by a large pneumatic foramen, and 

 there is a second aperture in the sternum, immediately behind 

 the first. In some of the Synallaxinee the sternal foramen is 

 found, but the more anterior aperture is wanting. 



The coracoid grooves do not meet in the middle line, and have 

 pi-ominent, sinuously cui-ved, dorsal lips : the ventral lips are 

 thin and continued inwards on to the spina externa. These 

 grooves attain their maximum development in the Oonopophagidse. 



The coracoid shaft is long and slender, but is apparently never 

 longer than the corpus stertii. The procoracoid process is never 

 lai'ge, and takes the form of a short, oblong, downwardly directed 

 plate ; thus, though smaller than in the Eulyljemidse, it is larger 

 tha.n in the highei- Passei-es. In the Hylactinse it extends upwards 

 to fuse with the inturned head of the acrocoracoid. The width of 

 the shaft at its base is increased by a short and narrow flange of 

 bone along the outer border, but this never extends further forward 

 than the level of a line passing in front of the free end of the 

 spina externa. 



The sca2mla, except in its relation to the foramen triosseum, 

 which will be discussed presently, presents no features of sufficient 

 interest to demand special notice. 



The furcida is of the typical U-shape, but varies as regards 

 the development of the hypocleideum and the form of its free 

 ends. The hypocleideum in Hylactes and in the Pipridse is vesti- 

 gial. In the Pittidse it is linguiform and rises abruptly from its 

 base : in the Philepittidaj it is almost quadrangular. It is 

 largest among the Dendi-ocolaptine, Synallaxine, and Formi- 

 cariine types, where it inclines to a cordiform shape. 



The nature of the articulations between the coracoid, scapula, 

 and furcula, where they meet to form the foramen tinosseum, are 

 interesting. They are of two kinds, one of which is peculiar 

 to the Hylactinas (text-fig. 51 e), while the other obtains more 

 or less exactly among all the other gi-oups. 



In Ilijlacies — Conopophagidfe, — as I have already mentioned. 



