392 PEOF. T. JEFFBET PAEKER ON THE CEANIAL OSTEOLOGY, 



of the dorsum sellae : the internal ophthalmic foramen [inf.. op. for.) is also continued 

 by a groove which extends downwards and backwards to the entrance of the internal 

 carotid artery {cnr.for.). The internal opening of the minute pathetic foramen {fatJi. 

 for.) is placed about 1 mm. dorso-laterad of the oculomotor. The internal carotid 

 canals (car.for.) open by paired apertures placed close together in the posterior wall 

 of the pituitary fossa. And lastly, in occasional instances, the fossa is perforated 

 anteriorly by the anterior basicranial fontanelle. 



The cerebral fossce lie altogether in front of the cerebellar fossa, there being no 

 overlapping of the cerebellum by the hemispheres such as occurs in Apteryx. They 

 are separated from the cerebellar fossa by the prominent tentorial ridge, which, starting 

 in the centre of the skull-roof, aimost exactly above the dorsum sellae, sweeps at first 

 backwards, outwards, and downwards, and then forwards, downwards, and slightly 

 inwards, and finely comes to an end near the extremity of the preoptic ridge. From 

 the middle of the tentorial ridge a somewhat less prominent median elevation, the 

 bony falx, passes forwards and ends just over the crista galli, marking the separation 

 of the hemispheres dorsally. 



The line of separation between the hemispheres on the ventral surface is similarly 

 indicated by a low median ridge which extends from the crista galli backwards to the 

 preoptic ridge. For a distance of about 5 mm. (in Emeus) on each side of this 

 ridge the cerebral fossae are floored by the presphenoid (fig. 15, pr.sph.) ; from it the 

 orbito-sphenoids {or.sph.) extend outwards and backwards, forming the dorsal 

 boundaries of the optic foramina. The resemblance of this portion of the Moa's 

 skull to that of an embryo Kiwi is very striking ; in the adult Apteryx the 

 presphenoid undergoes a remarkable shortening. 



The anterior moiety of the roof and side-walls of the cerebral fossa is furnished by 

 the frontal, the posterior portion by the parietal and alisphenoid. A low horizontal 

 ridge running a short distance above the parieto-alisphenoid suture indicates the 

 presence of a similarly-placed sulcus on the cerebrum. 



The olfactory fossw are paired oval pits placed vertically at the anterior end of the 

 cerebral fossae. They are separated from one another by a narrow bony ridge, the 

 crista galli, and the floor of each is perforated by a variable number of somewhat 

 irregular apertures for the branches of the olfactory nerve. 



b. The Premaxilla. 



The premaxilla is a triradiate bone which may be described in general terms as 

 consisting of a thickened body which forms the end of the beak, a median dorsal nasal 

 process, paired ventro-lateral maxillary processes, and thin ventral palatine processes 

 connected in front with the body and externally with the maxillary processes. 



The anterior extremity of the body, forming the apex of the beak, is rounded in 

 Dinornis and Emeus, bluntly pointed in Pachyornis, Mesopteryx, and Anomalopteryx. 



