i which it first manifested in fishes. Beside* the alUphenoid* or neura|K>phym () 

 impressed by the mestnccphalic ganglia MM! transmitting the trigeminal IHH% besides the 

 vastly expanded and gun, as in tube*, divided neural (pine (?) (parjetal bone*), thr |iarapo- 

 phyiw () (mastoid) is independently developed. It is of Urge projiortioiud me ; and, owing 

 to the raited dome of the neural arch, is relatively lower in potition than in the Crocodile . it 

 leads downward* and outwards an unuual)y long ' maitoid ' process, and forms a large pro- 

 portion of the outer wall of the chamber of the internal ear, with the bony capsule of which 

 it speedily coalesces. 



The lurmal arch of the parietal vertebra is more reduced than in the Crocodile, and owe* 

 much of its apparently typical character to the retention of the thyrohyals (M, ) borrowed 

 from the branchial arches of the visceral system, which are feebly and transitorily mauifratrd 

 in the embryo bird. These spurious cornua project freely or are freely impended. 



The bones (it) of the third neural arch (called 'oruito*phcnoid*') protect a smaller pro- 

 portion of the prosencephalon than in the Crocodile, but maintain thrir neurapophyual rela- 

 tion to it and to the optic nerves : the neural spine* (n) (frontal bone*) cover a larger pro- 

 portion of the hemispheres, and, with their homotypes (), exhibit a marked increase of 

 development in conformity with that of tin- cerebral centres protected by their respective 

 arches. The parapophyiis of the frontal vertebra (it) (postfronlal) is relatively smaller in 

 the bird than in the cold-blooded vertebrates, and is rarely ossified from an independent 

 centre, as it is in the Emeu. The hsemal arch of the frontal vertebra lias been transferred 

 backwards to the parietal one ; its pleurapophysis () (the tympanic), which is simple, a* in 

 the Crocodile, articulating exclusively with the parietal parapophysis () (mastoid), though 

 this in some birds unites with that of the frontal vertebra. In the young Ostrich and many 

 other birds, traces of the composite character of the hsemapophysis (mandibula) are long 

 extant ; and bear obviously a homological relation to the telrologically compound character 

 of the same element in the Crocodile : for the pieces, Nos. n, t*', M' and 11 ultimately, and in 

 most birds early, coalesce with each other and with the hsemal spine (n) (dentary clement). 

 the halve* of which are conluent at the symphysis. 



The centrum (u) (vomer) of the nasal vertebra is always single, and, when it does not 

 remain distinct, coalesces with the neurapophyie* (prefrontal*), M, and pleurepophyncs (pala- 

 tine*), M, of it* own segment; and sometimes also with the rostral production of the frontal 

 centrum (*) : it is elongated and pointed at its free termination, and deeply grooved above 

 where it receives the above-named rostrum ; indicating both by its form and position that it 

 owe* it* existence, as bone, to the ossification of the outer capsule of the anterior end of thr 

 notochord. In the Ostrich the long presphenoidal rostrum intervenes between the vomer (i>) 

 and prefrontals (u). These latter bones manifest, however, all the essential neurapophycial 

 relations to the rhinencephalon and olfactory nerves : but they early coalesce together, or arr 

 connate, as in the tail-lews Batrachians. The neural spine (nasals) (is) is divided along the 

 middle line ; but in most birds the suture becomes obliterated and the spine coalesce* with 

 its neurapophyses, with the frontal spine, and with those parts of the hsemal arch of the nasal 

 vertebra with which it conies in contact. 



The pleurapophyse* (palatines) (*) of this inverted arch retain their typical connections 

 with the nasal centrum and neurapophyses at one end, and with the hscmapophysis (maxil- 



