194 ME. W. P. PYCRAFT ON THE MORPHOLOGY AND 



that of Binornis. The form of the t)iUer and inner mandibular condyles is not unlike 

 that of Linornis. The inner condyle is, however, more nearly spherical tlian in any of 

 the other forms herein described. 



Apteryx possesses a readily distinguishable quadrate. The height of its vertical axis 

 is less than that of a line passing backwards through the orbital process, which is very 

 long. 



The articular condyles for tlie mandible present the same ground type as in Dromceus 

 and Casuarius, but the external condyle presents a tendency to split into two facets, 

 the region nearest the quadralo-jugal bar being scooped out. The zygomatic process 

 of the squamosal is closely applied to the outer side of the quadrate. In Struthio and 

 B/iea, it should be mentioned, there is a considerable space between these two points. 



In all the Pala'0(j)iath(e the quadrate is peculiar in that the pterygoidal articulation 

 extends upwards on to the orbital process for more than half of its length. 



In Apteryx the articular surface for the pterygoid is rather more sharply defined 

 than in the other Pakeognatluv. Arising at the base of the internal mandibular 

 condyle, it extends outwards on to the inferior border of the base of the orbital process, 

 taking the form of a deep hollow into which the pterygoid closely fits. 



The otic process has two fairly distinct articular facets. Superiorly transversely 

 elongated, its mesial extremity is expanded into an almost circular head and articulates 

 with the pro-otic. Its external extremity runs obliquely down to the shaft towards the 

 middle line, and affords an articular surface for the alisphenoid and squamosal. 



The pneumatic posterior aperture is sometimes absent. 



The separation into pro-otic and squamosal heads in the other Pakeo(jnatlm is only 

 very feebly indicated. 



The exoccipital does not contribute towards the articular surface for the quadrate in 

 Apteryx. 



The Mandible. (PL XLIII. fig. 9.) 



The mandible in Casuarius is long, slender, and sigmoidally curved. Posteriorly, it 

 is expanded to afford an articular surface for the quadrate. This is moderately deep, 

 and with sloping sides meeting at a sharp angle at the bottom of the fossa. Internally, 

 it is produced into a blunt internal anyular p>TOcess. The surface for the external condyle 

 forms a long narrow facet running parallel with the external border of the cup ; that 

 for the inner forms a band-shaped facet, hollow from within outwards. Immediately 

 without the inner end of this internal facet is a pneumatic foramen. The posterior 

 angular process is only feebly developed. 



In Dromceus the internal and external angular processes are larger than in Casuarius. 

 The rami are almost straight, and the symphysis is very broad. In other respects the 

 jaw agrees with that of Casuarius. In Pinornithidce, e. g. Linornis, the articular 



