144 MR. W. K. PAEKEE ON THE STRUCTUEE AND 



enlarged (Plate XII. fig. 1, o.s.); the two pieces have become one, and this is spreading 

 into the alae ; it commenced in this case in the floor of the skull ; in the young D. irro- 

 ratus the two bony points began in the angle on the right side. The interorbital 

 fenestra (Plate XII. fig. 1, i.o.s.) is small and very high up, and the interethmoidal 

 fenestra {Le.s.) is increasing ; it is twice the size of the other. The large, irregularly 

 V-shaped vertical ethmoid {p.e.) bounds most of this fenestra; its sutures (in front and 

 behind) with the upper oval bone (Plate XII. fig. 3, eth.) are not yet obliterated ; that 

 behind is best seen. The descending part of the upper bone is thick both before and 

 behind ; above the fenestra it is extremely thin. All the rest of the cranio-facial axis 

 is still unossified, and the septum nasi [s.n.), which is deeply emarginate in front, has 

 (relatively) retreated far back ; the prenasal cartilage has become a mere thread of 

 tissue ; the whole of the rest of the olfactory cartilages are still soft. 



The axis of the palatine apparatus is difierent from what we saw in the almost ripe 

 embryo ; for the pterygoid is more outspread (reptilian), whilst the anterior part of the 

 palatine has become elongated (Plate XII. fig. 2, jj.g., pa.), and the broad part thinner 

 in the middle, the absorption of its substance having increased. The metapterygoid pro- 

 cess of the quadrate bone {q.) is still unossified to a great degree ; if an epiphysis were 

 to develope in this cartilage, we should have the metapterygoid of the Fish, the Lizard, 

 and the Python*. 



The " articulare " (Plate XII. fig. 1, ar.) is now a curious, thick, three-faced wedge of 

 bone, and the Meckelian rod is gradually wasting. 



The OS hyoides has acquired a basi-hyal bone ; the uro-hyal, although continuous, is 

 still cartilaginous, as are the cerato-hyals, the upper thyro-hyals, and the ends of the 

 lower thyro-hyals. 



The squamosal (Plate XII. figs. 1-4, sg-.) is already very thick, and the " zygomatic 

 process," instead of joining the malar, as in Mammals, grows down the quadratum to 

 the very edge of the articular cartilage. It may not be easy for the mere anthropoto- 

 mist to see the relation of the squamous part of the temporal to the little " incus," but 

 the problem is soluble enough in this young Emu ; a splint could not be put on better 

 than this is. The five pairs of secondary pieces (Plate XII. fig. 1) in the lower jaw are 

 all distinct, but are well grown ; the coronoid is the shortest, does not rise to the edge 

 of the jaw, and has nothing whatever to do with the coronoid " process " of the dentary 

 in the Mammal. As for the true maxillary, it has either not been ever separate, or it 

 has already coalesced with either the malar or the prevomer; the jugal and quadrato- 

 jugal (Plate XII. figs. 1, 2, «& 3,/, q.j.) together form a round style. 



I have already spoken of the decreased width and lessened elevation of the premaxil- 

 lary; its prenasal groove is almost extinct (Plate XII. fig. 2, ]).x.); there is a large 



* In my paper on the " GalUnae," p. 221, I have spoken of the absence of the metapterygoid in certain 

 groups of the Vertebrata, amongst them the Ophidia ; since then I have found it very distinct on the front 

 of the 08 quadratum in a half-grown Python Sebce, the gift of Mr. Watekhouse Hawkins, and in other non- 

 venomous snakes. 



