DEVELOPMENT OF THE SKULL IN THE OSTRICH TEIBE. 165 



We have shown that this rostrum attains its extremest size in the "Struthionidae; " 

 and amongst them it is largest in the African Ostrich. JDinornis rohustus agrees entirely 

 with the African bird in this respect, as the photograph beautifully shows, for the lower 

 table of the bone is broken towards the base, and the coarse diploe can be seen within ; 

 in front of this abrasion the rostrum is seen swelling out into an enormous basiseptal 

 beam, exactly as in Struthio camelus. At the base of the rostrum, in front of the basi- 

 temporals, the great anterior pterygoid processes are given off in the Dinomis ; they 

 extend further outwards than the basitemporals, as in aU the Struthionidse, and in no 

 other birds. These processes are aborted in all the Rails, a mere trace being visible in 

 some of them, as in the Crake ; they are quite aborted in the Notomis, and they exist 

 in no known Reptile ; but they reappear in some Mammals, e. g., Cavia. In all the 

 " Struthionidse " the body of the basisphenoid intervenes (below) between the openings 

 of the Eustachian tubes ; in all other birds the basitemporals meet below these tubes so 

 as to protect them with a lip-like floor, the tubes opening together close to the mid 

 line ; all this is well seen in the Notomis. 



When in old birds the Eustachian tubes are at all enclosed in bone, in members of 

 the Ostrich family the sheath is quite lateral, and is formed by the meeting of one lip 

 from the basitemporal, and another from the " posterior pterygoid process ; " they evi- 

 dently have not even this protection in the Dinomis, but, as in the Emu, are only roofed 

 by bone, and are at the widest distance apart. We spoke of both basitemporal and of 

 anterior basisphenoidal outgrowths (wings) ; they coexist in the Palamedea and the 

 King Vulture, but not in the Great Rail, which thus diverges furthest from the birds 

 towards the Lizards ; it had them all, however, in its infancy, for they exist in all 

 embryo-birds. 



In Dinomis the thick " rostrum " passes forwards to within a short distance of the 

 body of the intermaxillary ; in Notomis the feeble rostrum is broken off anteriorly ; but 

 even if it passed on in front of the vertical ethmoid as far as it does in Crex, Ocydrormis, 

 PorpJiyrio, and Psophia, yet it would still be an inch from the body of the intermaxillary. 

 In Dinomis, as in the other Ostriches, the perpendicular ethmoid ossifies the whole 

 septum, filling up the space between the large nasal fossae ; in Notomis this bone stops 

 abruptly beneath the cranio-facial hinge, in the manner of a typical bird. The posterior 

 wall of the lateral ethmoid is well ossified in Dinomis, and has coalesced with the middle 

 bone ; these osseous plates extend much further outwards than in Notomis. 



The OS quadratum of Dinomis is quite struthious, the upper head not being divided 

 into two heads, the foreshadowings of the incudal crura of the Mammal ; and the meta- 

 pterygoid process is bluntly conical, as in the Emu. In the Giant Notomis this bone 

 is thoroughly ralline, and at the same time perfectly typical. Professor Owen has 

 described it under the term tympanic {op. cit. p. 256), and has well shown its peculia- 

 rities. It comes very near that of its ralline congeners, especially Crex ; and the form of 

 its double upper head, convexo-concave, broad metapterygoid process, and pimple-shaped 

 pterygoid process, are all diagnostic characteristics showing its true relationships. 



