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The skull of the Jptrryx b chiefly Mnarkable for iu smooth, expanded, derated, pyri- 

 form cramal portion, the total ab*rnrc of Miperorbiul ridges, the completeoeas and the thick- 

 MS of the iiiterorbital wplum, owing to the great development of the tnrlmml bones, the 

 mall me of the lacrymal bone*, and the combination of the depre*ied with the elongated and 

 alcadar fcrm of the beak. 



The occipital region of the cranium hai a pretty rricular einicircular contour, and differ* 

 fes> that of other Sinithiou* bird* in the greater relative extent of it* bate, and in the com- 

 paratively slight lateral sinuosities due to the temporal depressions. The single bctniipheri- 

 cal tubercle in the basioccipiul, for the articulation with the atlas, hai nut the vertical notch 

 at the upper "part observable in the Utttich and Emeu, but i* entire a* in the Rhea ; and the 

 plane of the occipital foramen ha* the Mine aspect at in that bird, in which it i* more nearly 

 horaontal than in the Ottrich. The tuperoccipital plate form* a aomewhat angular projec- 

 tion, correapoutling with the tmall cerebellum within, and ia bounded on each tide by a ver- 

 tical vascular groove, terminated by a foramen above and below : external to the*e groove* 

 the exoccjpitals extend outward* and downward*, in the form of obtuae protease*, comprand 

 in the antero-posterior direction, (lightly convex behind and concave in front, where they 

 form the back part of the wide meatu* auditoriu* extemu*. All the part* of the occipital 

 bone air anchyloaed together, and aUo to the unrounding bone*. 



The angle between the posterior and superior region* of the cranium i* scarcely produced 

 into a ridge. The superior region i* smooth and regularly convex ; it i* separated from the 

 temporal depressions by a narrow ridge, a little more marked than the occipital one. 



The superior is continued into the lateral region* of the cranium by a continuous curva- 

 ture, so that the upper part of the small orbital cavity is convex, and its limit- undefinablc, 

 there being no trace of superorbital ridge or antorbital or postorbital processes : this *truc- 

 ture is quite peculiar to the Aptrryx among birds, but produce! a very interesting resem- 

 blance between it and the monotrematou* Eekiilna. 



The frontal hones gradually contract to their junction with the nasal bones, between which 

 there i* the trace of a small part of the confluent prefrontals. The narrow frontal region of 

 the skull is traversed by a mesial longitudinal depression. 



At the bate of the skull we End in the Apleryx all the peculiarities characteristic of the 

 Struthiou* birds. The body of the iphenoid sends outward* on each side two processes, of 

 which the posterior abuts against the tympanic bone, and the anterior one, by a flattened 

 oval articular surface against the pterygoid bone : the latter processes exist, but are much 

 more feebly developed, in the Ibis : in most other birds, including the Gratia, they are want- 

 ing : they are well-developed in the Lacertine Sauna. A compressed votnerine process i* 

 continued forwards from the anterior part of the basuphenoid, and this process ia anchylosed 

 to the under part of the expanded and cellular ethmoid. 



The optic foramina are distinct both internally and externally, and are half an inch apart ; 

 they are perforated, not in the (phenoid ala, but in the inflected margin of the frontal bone. 

 In these peculiarities the Apttryx differs from all the rest of its class : each optic foramen, 

 however, transmit* not only the optic nerve and ophthalmic arUry. but also the third, fourth, 

 first branch of the fifth and sixth nerves, a* in most other bird*. Of these nerve* the fifth 

 is the Largest, and it ia continued forwards to the nasal canal, through two foramina, one cir- 



lEl 



