SKULL OF THE “ZGITHOGNATHOUS BIRDS. 279 
the outer a little the longer of the two. ‘These processes continue long and sharp even 
in thoroughly fledged birds (Plate LI. fig. 2). In the adult the dentary part is a 
broadish band of bone, enlarged near its end by the coalescence with it of the descend- 
ing crus of the nasal, but not by the maxillary, which lies behind it as in other Classes 
of the Vertebrata. 
The palatine processes of the premaxillaries (p.pa) are now small processes lying 
below the prepalatal bar, at its end; between these there is an elegant triangular 
middle process. The angle of the dentary part is cut off transversely, and is notched 
in the middle; into this notch the fore end of the once styliform maxillary (op. cit. fig. 4, 
ma) fits: it is now a short knuckle of bone. The body of the maxillary is very short, 
and at once gives off and ends in two processes—one, the jugal (j.mx), originally very 
long and free (op. cit.), but now coalesced with the jugal; the other branch is the maxillo- 
palatine (ma.p), once (op. cit.) a large curved spatula, and now a large, decurved ladle, 
its end being wrought into a thin-walled air-cell. Above, the hinge is made by such 
adaptation of the rostrum with the frontals that the fibres of bone running into the liga- 
ment are extremely thin, and the bones are nearly applied by transversely squared ends. 
In the vomer also the Tits are contrary to their relations; for, whilst its shoulders are 
broad, its legs are feeble and drawn near together (Plate LI. fig.1,v). In the embryo 
(op. cit.) the vomer is two threads of bone; in my figure these are shown as just united 
in front, and these threads converge backwards. In adults of the same species, 
through difference of age, the head of the bone varies: it has no emargination at 
first; but this appears and increases as the bony matter creeps into the contiguous 
nasal wall. 
The vomer is subcarinate in front, below; and it neither shows parallel lateral divi- 
sion, nor have I found the smallest septo-maxillary at its angles. ‘The septum nasi has 
a large posterior ossicle (fig. 1, s. »), which involves the wings, or bridges, that cover 
the nasal-nerve tract. The rest of the relatively large and deep septum is ossified con- 
siderably above, in conjunction with the floor of the al, in front; but the trabecular, 
or basal portion (tr), which is alate, remains soft, as do the turbinals and outer 
wall. 
The ecto-ethmoid (fig. 1, p.p, ¢.eth) is typically Passerine: the upper part projects 
moderately ; the pars plana is thick and spongy, and has a lateral rounded emargination, 
a large “foot,” and no appended os uncinatum. The nerve-passages above the ante- 
orbital are perfectly distinct. I find no distinct lacrymal in the adult. 
Example 56. Skull of the Ox-eye Tit (Parus mgor). 
Habitat. Great Britain. 
In a young specimen of our native largest Tit the parts just described are interme- 
diate between those of the embryo (op. cit.) and of the adult of the last species. The 
