PHYLOGENY OF THE PAL^EOGNATH^E AND NEOGNATHvE. 175 



to form the zygomatic process. In Casuarius, Dromceus, JEpyornis, and Rhea this process 

 is of considerable length, and runs down to within a short distance of the cup-shaped 

 fossa for the articulation of the quadrato-jugal bar. In Rhea it runs forwards and 

 downwards to overhang this articulation. 



In Dromceus, except D. ater, the anterior border of the squamosal prominence bears 

 a strong protuberance. 



In Struthio and Apteryx the zygomatic process is very short. 



In Dinornithidce the middle region of the squamosal is much inflated, making the 

 squamosal prominence very conspicuous. 



The temporal fossa is more or less conspicuous in all the Palceognathce, save Apteryx. 



In Casuarius and Dromceus it is narrow and deep. In the latter its limits are 

 sharply defined. 



In the Dinornithidce the size of the fossa varies, but is generally wide and deep, its 

 general direction is backwards. 



In Rhea it is wide and shallow, and with a linguiform impression. In Crypturi it 

 resembles that of Rhea, but is shallower. 



In Struthio narrow, moderately deep, and slopes obliquely backwards. 



JEpyomis has the same type of fossa as Struthio, but deeper and much more sharply 

 defined. 



In Apteryx it is represented by a shallow but sharply defined depression extending 

 far forwards. It is peculiar from the fact that it is not bounded anteriorly by a post- 

 orbital process. 



The post-orbital process in Casuarius is strongly developed ; it forms a broad 

 linguiform process extending downwards to within a short distance of the quadrato- 

 jugal bar. In Dromceus novce-hollandioe and D. ater its downward extent is much less. 



In Emeus, amongst the Dinornithidce, it is even larger than in Casuarius. 



In Rhea it is relatively small, somewhat pointed, and directed slightly backwards. 



In Struthio it is but slightly developed, and runs forward to blend with a shelf-like 

 projection of the frontal overhanging the orbit. 



In Crypturi it is represented only by a minute prickle. 



The trigeminal foramen is a conspicuous aperture lying, in Casuarius, at the bottom 

 of the temporal fossa at the point where the outer angles of the alisphenoid d 

 pre-temporal wing meet, and in the same transverse plane as the basipterygoid pro- 

 cesses. Immediately behind this, in Dromceus, and less distinctly in Apteryx and Rhea, 

 is a smaller aperture leading into the tympanic cavity. 



The orbits in Casuarius, Dromceus, and Rhea are all more or less alike in form and 

 size. All are strongly walled-in behind by overhanging and laterally projecting post- 

 orbital processes, and are in front protected and increased by long backwardly directed 

 spurs from the lachrymal. 



Struthio differs markedly from the above in that the spurs of the lachrymal over- 



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