202 ]ME. W. p. PYCEAFT ON THE MOEPHOLOGT AND 



sphenoid, anchylosis therewith taking place later. Thus it is that the pio-otic comes to 

 be entirely concealed. 



In all ihis, Dromceus and Casuarius seem, to be less primitive than the Penguin. In a 

 skull of this group recently described and figured by me [82] the squamosal was attached 

 to the dried skull simply by its articulation with the parietal. Its hinder border was 

 dee2)iy emarginate and free, exposing the pro-otic. Its anterior border was also free, 

 not extending to the alisphenoid, but exposing between itself and this last a small 

 portion also of the pro-otic. 



There is one great point of difference, however, between the squamosal of Bromceus 

 and that of the Penguin. In the former, its antero-ventral angle is produced 

 downwards into a large " zygomatic process," to embrace the quadrate ; in the latter, 

 this spine is replaced by two small spines, as in all the Neognathce. 



Except in Apteryx the squamosal takes no part in the formation of the inner wall of 

 the skull. 



In Apteryx the squamosal has entered into a slightly closer relation wdth the 

 alisphenoid and exoccipital than in the forms described above, resembling in this 

 respect the Neognathce. Thus the anterior border is concave and fits the corresponding 

 convex border of the alisphenoid ; whilst the posterior border, though separated by 

 a narrow line of cartilage from the exoccipital, yet gives signs of effecting a close union 

 therewith immediately. 



The squamosal appears on the inner surface of the skull as a small triangular plate 

 above the pro-otic. 



The nasal in Lromceus is holorhinal. The maxillary process is greatly reduced, 

 especially so in the adult, where it exists only as a vestige. It is produced caudad into 

 a long slender process resting on the frontal, and projecting beyond the lozenge-shaped 

 plate of the mesethmoid, to which it binds externally. Its premaxillary or internal 

 process is of considerable length, extending forwards almost the whole length of the 

 nasal process of the premaxilla, which protects them from above. 



Dinornis is holorhinal. 



A skull of Megalajyteryx, in the collection of the Hon. Walter Eothschild, retains 

 sufficient of the traces of sutures in this region to indicate the form of the nasal in the 

 Linornithida^. 



In this skull, it is seen to be relatively much shorter than in Lromceus. Its backward 

 extension does not pass the level of the horizontal mesethmoid plate and is not so 

 pointed as in Bromceus. Its maxillary process is wanting. The ossified aliethmoidal 

 plate projects beyond its lateral border. 



In Casuarius the nasal is schizorhinal . The maxillary process is vestigial, and the 

 premaxillary process long, as in Bromceus. It is peculiar in that the body of the bone 

 is greatly inflated and takes part in the formation of the casque as already described 



