1907. j TO THE OSTEOLOGV OF BIRDS. 361 



mass of cancellated tissue, surrounded, above and below, by a large 

 air- sinus, so that a considerable space is left, in the dried skull, 

 between the ossified floor of the vestibulum to which the palatines 

 are attached and this cancellated mass. 



The quadrate- jugal bar affords no characters requiring comment. 



The Vomer, Pterygoid, and Pcdatine. 



The vomer is of the typically Passerine type, but presents certain 

 features worthy of note. Broad, and of modei-ate length, its 

 ventral aspect, in the simpler forms, e. g. Tyrannus, is that of an 

 oblong plate of bone cleft in the middle line from behind forwards 

 for rather more than half its length, and sharply triincated in 

 front. The right and left posterior limbs pass insensibly into 

 the palatines. Anteiiorly, the vomer expands to form a pair of 

 thickened quadrangular horns the external, lateral faces of which 

 lodge a more or less cuj)-shaped depression. 



The Tyrannidpe and Muscicajjidfe agree very closely in the form 

 of the vomer. The Campophagidje, however, would appear to be 

 even simpler in this respect than either of these two Families, 

 inasmuch as in Campopliaga the vomer is anteriorly sharply 

 truncated and lacks the quadrangular anterior horns, though an 

 approximation to these is to be seen in the vomer of Tylas. 



In the Lauiinse the vomer, as in the Tyrannidfe, ex])ands, 

 anteriorl}', into a pair of quadrangular homs, but each sends back- 

 wards from its antero-dorsal angle a thin plate of bone which, 

 running backwards along the outer margin of each side of the 

 dorsal aspect, gives the vomer, when seen from above, a trough- 

 shape. Further, in Laniarius, the quadrangular horns referred 

 to afford, on either side, an articular surface for the maxillo- 

 palatine process. 



The Dicruridpe differ from the typical Laniidte in the form of 

 the vomer chiefly in that in the former it is relatively broader, 

 especially at its anterior end which is sharply truncated. The 

 increased width, anteriorly, is due to the fact that the "horns" 

 project outwards and forwards instead of directly forwards. These 

 hoi-ns, furthermore, are peculiar in that they send downwards a 

 broad facet to articulate with the spatulate maxillo-palatine 

 process. The terminal " horns " of the vomer rise upwards to 

 embi-ace the free edge of the nasal septum, and are continued 

 backwards along each side of the dorsal aspect of the vomer, 

 thereby converting this into a shallow trough. 



In the Gymnorhinfe the vomer is more conspicuously modified 

 than in any other of the types herein discussed ; being short, 

 antero-posteriorly, and having a well-defined median ventral keel 

 and deeply trough-shaped dorsal aspect. These characters are 

 perhaps most mai-ked in Gijmnorhina, though in Pityriasis they 

 are scarcely less so. In the former genus the free end (anterior) 

 of the vomer is deeply cleft, while the under surfaces of the 

 two resultant horns are cut away, or hollowed out, so as to 



